The research team, led by Cristina Antinozzi and Luigi Di Luigi, set out to address a gap in what is known about PDE5 inhibitors and muscle. Skeletal muscle regeneration depends on the activation, proliferation and eventual differentiation of myogenic progenitor cells, the satellite cells that sit dormant along muscle fibers until injury or exercise wakes them up. Nitric oxide signaling is known to be a key player in this process, and because PDE5 inhibitors prolong cGMP signaling downstream of nitric oxide, scientists have long suspected the drugs could influence how muscle repairs itself. What remained unclear was what happens when cells are exposed to tadalafil not for hours, but for days.

To find out, the researchers used C2C12 cells, a mouse myoblast cell line that is one of the workhorses of muscle biology research. When switched to low-serum conditions, these cells reliably exit the cell cycle, fuse together and form multinucleated myotubes, allowing scientists to track every stage of myogenesis in a dish. In the study, the cells were treated with 1 micromolar tadalafil for up to seven days, a prolonged exposure designed to mimic sustained pharmacological use rather than a single transient dose. The team then measured proliferation, cell viability, the activation of myogenic marker genes and the release of myokines, the signaling molecules that muscle cells secrete.

The first striking result was survival and growth. Tadalafil significantly increased cell proliferation and survival across all time points, reducing cell death throughout the treatment period. In practical terms, the drug appeared to keep the myoblast population expanding robustly instead of losing cells to apoptosis or stress. For a field where muscle-wasting disorders such as Duchenne muscular dystrophy and age-related sarcopenia are driven partly by the exhaustion and death of regenerative cells, any compound that keeps progenitor pools alive and dividing is of obvious therapeutic interest.

The myogenic program itself, however, showed a more nuanced response. Tadalafil enhanced the expression of early myogenic factors, the transcriptional switches that mark the beginning of the muscle-building program. Yet at the same time, it delayed terminal differentiation. Cells exposed to the drug for seven days produced fewer myosin heavy chain-positive multinucleated myotubes, the mature structures that represent the end point of myogenesis, and they maintained higher expression levels of Pax7 and Myf6, two markers associated with a less differentiated, more stem-like phenotype. In other words, tadalafil did not simply accelerate muscle formation; it appeared to keep the cells poised in an earlier, more regenerative state.

That combination, more proliferation plus delayed differentiation, is exactly the profile one would want from a drug intended to boost the regenerative capacity of muscle. Satellite cells that differentiate too quickly may rebuild a damaged fiber but fail to replenish the stem cell pool, whereas cells that self-renew can sustain repair over repeated rounds of injury. The Pax7 protein in particular is a master regulator of muscle stem cell self-renewal, and Myf6 has been implicated in maintaining the satellite cell niche. By sustaining expression of these factors, tadalafil seems to preserve the regenerative reserve rather than spend it, a mechanism the authors describe as promoting a highly proliferative state while preventing premature differentiation.

The molecular signature behind this shift offers further clues. The treated cells showed upregulation of Sirt3, the mitochondrial sirtuin deacetylase that governs mitochondrial fitness, oxidative stress resistance and metabolic adaptation, alongside increased IL6, an interleukin with well-documented roles as a muscle-derived myokine that can support regeneration. At the same time, the cells downregulated myostatin and TGF-beta, two of the most powerful brakes on muscle growth in the body. Myostatin inhibition is already a major strategy in the development of drugs for muscular dystrophy and other atrophic conditions, so its suppression under tadalafil treatment is a particularly meaningful signal. Reduced TGF-beta signaling likewise removes a barrier that normally restrains progenitor cell activation and progression through the myogenic program.

These results build on a body of earlier work by the same group and others. Previous studies had shown that tadalafil regulates lipid homeostasis in human skeletal muscle cells, improves lean mass and endothelial function in certain patients, and that nitric oxide and cGMP signaling sustain long-term muscle regeneration by controlling the fate of satellite cells. Clinical observations in boys with Duchenne muscular dystrophy have suggested that PDE5 inhibition can alleviate functional muscle ischemia, and recent epidemiological work has even associated PDE5 inhibitor use with reduced mortality and lower rates of cardiovascular disease and dementia. The new study adds a direct cellular mechanism: prolonged cGMP signaling appears to reprogram myogenic progenitors toward expansion and self-renewal while dialing down the anti-growth factors that would otherwise push them to mature and stop.

The therapeutic implications are considerable. If the same biology holds in human tissue, tadalafil or related compounds could serve as adjuvant pharmacological therapy for muscle-wasting disorders, helping patients with dystrophies, sarcopenia or disuse atrophy maintain a larger, healthier pool of regenerative cells. The drug is already widely prescribed, has a well-characterized safety profile and acts on a pathway that is naturally engaged by exercise itself, since muscle contraction increases nitric oxide production. A licensed medicine that amplifies an endogenous repair pathway is an attractive candidate for repurposing, and the authors explicitly point to this potential in their conclusions.

But the same mechanism that excites clinicians also alarms anti-doping authorities. A drug that increases progenitor cell proliferation, suppresses myostatin and TGF-beta, and keeps muscle in a regeneration-primed state is, on paper, a potential performance enhancer, capable of accelerating recovery from training damage and possibly supporting hypertrophy. The researchers themselves highlight this concern, noting that the potent improvement of the muscle regenerative machinery raises critical questions about misuse in sport and calling for evaluation by anti-doping agencies. As with any cell-culture study, important caveats remain: the work was done in a mouse cell line at a specific dose, and whether prolonged tadalafil exposure produces the same progenitor-sparing effect in living human muscle is not yet known. Still, the study marks a notable step in understanding how a familiar cardiovascular drug talks to the stem cells of the musculoskeletal system, and it ensures that both regenerative medicine specialists and sports regulators will be watching the next round of experiments closely.

Subject of Research: Effects of prolonged tadalafil exposure on myogenesis and myogenic marker activation in C2C12 skeletal muscle cells

Article Title: Prolonged tadalafil exposure promotes skeletal muscle myogenesis and regulates early myogenic markers activation in C2C12 cell lines

Article References: Antinozzi, C., & Di Luigi, L. (2026). Prolonged tadalafil exposure promotes skeletal muscle myogenesis and regulates early myogenic markers activation in C2C12 cell lines. Molecular Biology Reports, 53(1), Article 1701. https://doi.org/10.1007/s11033-026-12929-x

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12929-x

Keywords: tadalafil, PDE5 inhibitors, myogenesis, C2C12 cells, satellite cells, muscle regeneration, myostatin, Pax7, Sirt3, interleukin-6, muscle-wasting disorders, doping

The research began with a question that has lingered in the muscle biology literature for years. Calcium dysregulation is a well-documented feature of diseased and aging muscle. Patients with systemic hypercalcemia, defined by serum calcium exceeding 3.0 millimolar, frequently complain of fatigue and proximal muscle weakness. Duchenne muscular dystrophy drives chronic cytosolic calcium overload through loss of the structural protein dystrophin. Aging muscle, meanwhile, shows increased resting intracellular calcium, leaky ryanodine receptors, and inefficient calcium reuptake by SERCA pumps. Yet most research had focused on how calcium controls contraction in mature fibers, leaving the impact on regenerating muscle largely unexplored.

To connect those dots, the team, led by Kee K. Kim of Chungnam National University, first turned to human data. Analyzing transcriptomes from 679 individuals in the GTEx v8 dataset, they compared gastrocnemius muscle from people aged 50 and older with samples from those under 40. Gene set enrichment analysis revealed that aged muscle showed coordinated activation of calcium signaling pathways and muscle cell proliferation programs, alongside upregulation of the quiescence regulator SPRY1, the early myogenic factor PAX3, and the proliferation marker CCND1. Crucially, the signature appeared in both men and women, suggesting that a proliferative bias tied to calcium signaling is a general feature of aging muscle rather than a sex-specific phenomenon.

The researchers then moved into the laboratory to test whether calcium excess directly alters myoblast behavior. When C2C12 mouse myoblasts and primary myoblasts isolated from hindlimb muscle were exposed to elevated calcium chloride under normal growth conditions, nothing dramatic happened. But when the same cells were pushed to differentiate while bathed in 3 or 6 millimolar calcium chloride, a striking picture emerged: total cell numbers rose significantly, the proliferative marker PAX7 climbed at both the protein and mRNA levels, and the cells failed to exit the cell cycle. Calcium imaging with the Fluo-4 AM indicator confirmed that intracellular calcium remained persistently elevated throughout the differentiation window, rising in a dose-dependent manner in primary myoblasts.

That persistent proliferative state came at a direct cost to myogenesis. Myotube formation declined dose-dependently in calcium-exposed C2C12 cultures, and levels of the myogenic markers MYH3 and myogenin dropped alongside their messenger RNAs. Primary mouse myoblasts showed the same defects, and, importantly, the phenomenon crossed the species line: human embryonic stem cell-derived myoblasts differentiated for two weeks in 3 millimolar calcium chloride formed fewer myotubes and produced less total myosin heavy chain. Notably, prolonged exposure to lower concentrations sufficed to impair differentiation, indicating that the duration of calcium elevation, rather than its absolute peak, is the critical determinant of pathology.

RNA sequencing of calcium-exposed primary myoblasts identified 2,776 differentially expressed genes and revealed the underlying transcriptional logic. Genes upregulated by calcium exposure were enriched for cell division and chromosome segregation, while downregulated genes clustered around muscle contraction and sarcomere organization. Gene set enrichment analysis flagged activation of the calcium-dependent NFAT pathway. Mechanistic experiments followed: NFATc1, tagged with green fluorescent protein, translocated into the nucleus of calcium-exposed myoblasts; the NFAT target gene Ccnd1, encoding cyclin D1, was upregulated; and chromatin immunoprecipitation showed that NFATc1 binding to the Ccnd1 promoter was significantly enhanced under calcium excess. In short, calcium was hijacking a pathway that normally helps orchestrate differentiation and repurposing it to keep the cell-cycle engine running.

To confirm the mechanism in living animals, the team used two complementary models. The first was the ovariectomized mouse, in which estrogen deficiency destabilizes calcium handling by hyperphosphorylating the ryanodine receptor 1, provoking spontaneous calcium release from the sarcoplasmic reticulum. These mice lost bone density, performed worse on treadmill endurance tests, and developed gastrocnemius atrophy. Their muscle transcriptomes mirrored the in vitro signature: enrichment of calcium signaling and proliferation programs, downregulation of developing and mature myosin heavy chain genes, upregulation of Pax7 and MyoD, shrunken myofiber cross-sectional areas, and clear nuclear translocation of NFATc1. The second model was human calcific tendinitis. In supraspinatus muscle samples taken from patients during calcific deposit removal, tissue adjacent to the calcium deposits showed downregulation of SPRY1, PAX3, and MYH3 together with upregulation of CCND1 compared with remote regions, demonstrating that even localized calcium overload in human tissue produces the same proliferative, anti-myogenic fingerprint.

The most translational part of the study came from pharmacological rescue. Using VIVIT, a selective peptide inhibitor of NFAT, the researchers blocked calcium-induced nuclear accumulation of NFATc1 in both C2C12 cells and primary myoblasts. VIVIT restored MYH3 expression and reversed the myotube formation defect under calcium overload. A complementary experiment using caffeine to induce sarcoplasmic reticulum calcium leak recapitulated the suppression of myoblast fusion, and VIVIT rescued that too, confirming the effect arises from intracellular calcium dysregulation rather than nonspecific stress. In vivo, the team injured tibialis anterior muscles with barium chloride, which triggers calcium-dependent proteolysis and robust regeneration, and injected VIVIT locally on days 0 and 2. Treated muscles showed improved regenerative morphology, larger myofiber cross-sectional areas, and a dramatic reduction in the proportion of immature myogenin-positive fibers, all without measurable changes in inflammatory markers such as Il6, Tnfa, and Inos.

One conceptual takeaway is that NFAT plays a duration-dependent dual role in muscle. Transient calcium-dependent NFAT activation has classically been viewed as a positive regulator of myogenesis, supporting fiber-type specification and hypertrophy. The new data show that when calcium elevation persists, the same pathway flips into an anti-myogenic mode, sustaining cyclin D1 expression and preventing the cell-cycle exit that myoblasts must undergo to fuse into contractile fibers. The authors also suggest this framework may help explain osteosarcopenia, the poorly understood co-occurrence of osteoporosis and muscle loss, since both tissues depend on well-regulated calcium handling, although they caution that this connection remains inferential and requires direct testing.

Limitations remain, and the researchers are candid about them. The therapeutic benefit of VIVIT was demonstrated in an acute injury model, not in the chronic ovariectomy setting, because repeated intramuscular injections over a six-week protocol would introduce local tissue damage and inflammation that could confound the results. Future work with long-term pharmacological approaches or genetic models will be needed to validate NFAT as a drug target for chronic calcium-associated myopathies. Still, by tracing a single molecular thread from aged human muscle through mouse myoblasts, ovariectomized mice, calcific tendinitis patients, and a rescued injury model, the study establishes chronic calcium-NFAT signaling as a credible mechanism linking calcium dysregulation to failed muscle repair, and it offers a concrete starting point for therapies aimed at restoring the regenerative capacity of weakened muscle.

Subject of Research: Mechanism by which pathological calcium overload impairs skeletal muscle regeneration through sustained NFAT-dependent proliferative signaling

Article Title: Pathological calcium overload impairs skeletal muscle regeneration through sustained NFAT-dependent proliferative signaling

Article References: Lee, S., Cho, N., Jo, S., Ji, J.-H., Kim, J. O., Park, C., Choi, S., Kim, E.-M., & Kim, K. K. (2026). Pathological calcium overload impairs skeletal muscle regeneration through sustained NFAT-dependent proliferative signaling. Experimental & Molecular Medicine. https://doi.org/10.1038/s12276-026-01856-3

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01856-3

Keywords: skeletal muscle, muscle regeneration, calcium signaling, NFATc1, myogenesis, satellite cells, cyclin D1, sarcopenia, calcific tendinitis, VIVIT, aging muscle, ovariectomy

The story begins with the biology of muscle repair itself. Skeletal muscle has a remarkable capacity to regenerate, and the workhorses of this process are muscle stem cells, known as MuSCs, which sit quietly beside muscle fibers until injury wakes them. Once activated, they proliferate, differentiate into myoblasts, and fuse to replace damaged tissue. But the stem cells do not act alone. They are embedded in a niche populated by immune cells, and the quality of repair depends on a precisely choreographed conversation between the two. Neutrophils flood the wound first, followed by pro-inflammatory macrophages that clear dead debris and release signals such as interleukin-6 and prostaglandin E2, which push MuSCs into their activation and expansion phase.

In a young, healthy muscle, this fiery opening act gives way to a calmer second act. Macrophages shift toward an anti-inflammatory profile, and the tissue begins producing a family of bioactive fats called specialized pro-resolving mediators, or SPMs. These molecules, which include resolvins, protectins, and maresins and are derived mainly from omega-3 polyunsaturated fatty acids, do not simply suppress inflammation the way a steroid might. Instead, they actively drive the resolution program: they help clear neutrophils, encourage macrophages to adopt repair-oriented states, and preserve the host defenses needed to fight infection. Crucially, this lipid-mediated class switch is what allows the regenerative environment to mature so that myoblasts can differentiate, fuse, and complete the repair.

Aging scrambles this choreography. Previous work has shown that old skeletal muscle is deficient in endogenous SPMs while remaining awash in pro-inflammatory eicosanoids such as prostaglandins and leukotrienes. The result is a niche stuck in first gear: macrophages and neutrophils linger far longer than they should, chronic inflammatory signaling persists, fibrosis accumulates, and MuSCs receive contradictory instructions that blunt their regenerative output. The Ottawa team, led by senior author Junio Dort, wanted to know whether supplying one key SPM from outside could compensate for this age-related deficit. They chose RvE1, the principal member of the E-series resolvins, which is derived from eicosapentaenoic acid and had been well characterized in other tissues but largely unexplored in skeletal muscle, where its D-series cousins had received most of the attention.

The first experiments were conducted in a dish. The researchers isolated bone marrow monocytes from mice older than twenty months, which corresponds to advanced age in the mouse lifespan, and differentiated them into macrophages. When these aged macrophages were stimulated with bacterial lipopolysaccharide and interferon-gamma to mimic an inflammatory assault, treatment with 200 nanomolar RvE1 produced a clear shift. The proportion of macrophages expressing CD206, a canonical anti-inflammatory marker, rose by roughly one and a half fold, while the fraction expressing CD163, another resolution-associated receptor, increased fourfold. Western blotting confirmed elevated CD206 protein. At the same time, quantitative PCR revealed that RvE1 significantly suppressed the expression of pro-inflammatory genes including tumor necrosis factor-alpha and transforming growth factor-beta, with downward trends in the neutrophil-recruiting chemokine CXCL1 and the inflammatory enzyme Ptgs2.

Interestingly, the molecule’s effects on classical anti-inflammatory genes such as interleukin-10 were modest. The authors interpret this selectivity through the lens of receptor biology. RvE1 signals primarily through ChemR23, a receptor enriched on inflammatory neutrophils and macrophages, where its activation dampens NF-kappaB signaling and cytokine production. In other words, RvE1 does not install a brand-new anti-inflammatory program; it switches off the persistent pro-inflammatory hum, and that silencing itself feeds back to promote pro-resolving macrophage polarization. This distinction matters therapeutically, because it suggests the molecule fine-tunes rather than blanket-suppresses immunity, preserving the early inflammatory cues that muscle stem cells actually need to begin repairing tissue.

The in vivo experiments then tested whether these cellular effects translate into better healing. The team injured the tibialis anterior muscle of aged mice with cardiotoxin and, beginning twenty-four hours after injury, gave the animals twice-weekly subcutaneous injections of RvE1 at five micrograms per kilogram for two weeks. Fourteen days later, the treated muscles looked meaningfully different from the vehicle controls. Total macrophage infiltration trended downward, the proportion of anti-inflammatory F4/80-positive CD206-positive macrophages rose significantly, and neutrophil accumulation, measured by Ly6G staining, dropped markedly. The regenerating tissue also contained more PAX7-positive muscle stem cells and more MYOG-positive differentiating myoblasts, indicating an expanded and more advanced myogenic cell pool.

Some structural measures told a subtler story. RvE1 did not change the number of newly formed embryonic myosin heavy chain-positive fibers or the average fiber cross-sectional area at the day-14 endpoint, but it significantly reduced the percentage of centrally nucleated fibers, a hallmark of repeated cycles of degeneration and regeneration, and showed a downward trend in collagen-rich fibrotic areas. Force testing with a dual-mode lever system revealed a general trend toward improved contractile function in the treated muscles, although the authors are careful to note that the relatively small sample size of three animals per group limited statistical power for some histological and functional outcomes. The picture that emerges is one of accelerated regenerative kinetics rather than a finished product: RvE1 appears to move the whole repair process forward in time.

The team also asked whether RvE1 acts directly on the muscle stem cells themselves, not just on their immune environment. When primary myoblasts isolated from aged mice were treated with RvE1 for sixteen hours in proliferation medium, levels of the myogenic transcription factor MYOD rose significantly, accompanied by increased Ki67 staining, a marker of active cell division. After four days in differentiation conditions, however, the molecule had minimal effect on myotube diameter or fusion index, suggesting that its direct myogenic action is concentrated in the early expansion phase. The authors propose that RvE1 may engage the BLT1 receptor expressed on myoblasts, and that in living muscle, RvE1-polarized anti-inflammatory macrophages likely add a paracrine boost by secreting myogenic growth factors such as insulin-like growth factor-1 and interleukin-4.

The study has limitations the authors acknowledge candidly. Macrophage polarization was assessed mainly through CD206 and CD163, whereas macrophage activation is now understood as a continuum of states rather than a binary M1/M2 switch; single-cell transcriptomics would paint a richer picture. The single day-14 endpoint cannot capture whether early cellular gains mature into lasting architectural and functional improvements, and the trends in fibrosis and muscle force await confirmation in larger cohorts. Native RvE1 is also hampered by a short biological half-life, though metabolically stable analogs and orally active SPM mimetics are in development, and early clinical studies of SPM-enriched supplements have shown encouraging effects on inflammatory biomarkers in conditions such as knee osteoarthritis. Even with those caveats, the convergence of evidence is compelling: a single omega-3-derived lipid can reprogram the aged muscle niche, clearing out lingering neutrophils, steering macrophages toward repair, expanding the stem cell pool, and nudging old muscle toward the regenerative behavior of its younger self. For a population whose falls, frailty, and lost independence trace back to muscles that no longer heal, that is a molecule worth watching.

Subject of Research: The role of the specialized pro-resolving mediator Resolvin E1 in inflammation resolution and skeletal muscle regeneration during aging

Article Title: Resolvin E1 promotes the resolution of inflammation and enhances myogenic responses during aged skeletal muscle regeneration

Article References: Arsenault, R., Ziadeh, A., Assebbane, A., Yezihalem, H., Green, A., & Dort, J. (2026). Resolvin E1 promotes the resolution of inflammation and enhances myogenic responses during aged skeletal muscle regeneration. GeroScience. https://doi.org/10.1007/s11357-026-02566-4

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02566-4

Keywords: Resolvin E1, specialized pro-resolving mediators, skeletal muscle regeneration, muscle stem cells, macrophage polarization, inflammation resolution, aging, omega-3 fatty acids, myogenesis, neutrophil clearance, fibrosis, GeroScience

The research focused on the Bama miniature pig, a small breed from Guangxi in southern China prized both for its excellent meat quality and its growing role as a biomedical model for human research. The team collected samples from two anatomically distinct muscles at six time points: embryonic days 57, 73, and 90, and postnatal days 1, 28, and 120. The longissimus dorsi, a back muscle dominated by glycolytic type IIB fibers, represents the fast-twitch archetype, while the semitendinosus, rich in oxidative type I fibers, embodies the slow-twitch phenotype. This dual-region, dual-time design allowed the researchers to separate the effects of anatomy from the effects of developmental time—a distinction that many earlier studies, which sampled only single muscles or single stages, could not make.

Technically, the proteomic work was ambitious. The team employed non-targeted data-independent acquisition mass spectrometry, or nDIA, applied for the first time to porcine embryonic skeletal muscle fibers. Using an Orbitrap Astral mass spectrometer with 300 DIA windows and high-resolution scanning, they identified an average of 6,118 proteins per sample, with a range spanning roughly 3,500 to 7,400. The transcriptomic side relied on Illumina NovaSeq 6000 sequencing, capturing an average of 13,354 genes per sample. Together, these datasets covered the vast majority of the expressed muscle proteome and transcriptome, giving the researchers an unusually complete view of how gene activity and protein abundance change in parallel—and, crucially, where they diverge.

The most striking pattern to emerge was temporal rather than spatial. Across developmental stages, the researchers identified 3,509 differentially abundant proteins, dwarfing the 272 proteins that differed between the two muscle regions at any given stage. Principal component analysis showed that fetal samples from E57 through E90 clustered tightly together, with correlation coefficients between adjacent fetal stages reaching 0.86. But after birth, the samples separated sharply along the developmental timeline, and the correlation between E90 and P1 dropped to just 0.59—the lowest of any adjacent pair. Birth, in other words, marks a molecular discontinuity, a wholesale reprogramming of the muscle proteome that no other transition in the study approached in magnitude.

Within that postnatal reprogramming, one window stood out. Between postnatal days 1 and 28, the semitendinosus gained more newly expressed proteins than the longissimus dorsi, and the two regions showed significant differences in both protein abundance and the biological processes those proteins supported. A heatmap of mitochondrial respiratory complex proteins revealed that regional differences in oxidative machinery first appeared at P28 and reached their peak at P120. Because oxidative fibers carry far more mitochondrial content than glycolytic fibers, this divergence in mitochondrial protein abundance is a direct molecular signature of the slow-versus-fast fiber split. The finding aligns with older histological work from 1972 showing that pig oxidative and glycolytic fibers become distinguishable between 21 and 28 days after birth—but the new study supplies the protein-level detail that histology alone could never provide.

The integrated analysis also exposed a deep layer of post-transcriptional regulation. Classifying genes by how their RNA and protein levels changed together, the researchers found that more than 90 percent fell into categories showing minimal or discordant changes between the two levels. Most tellingly, the proportion of Type 2 genes—those with substantial protein-level changes but minimal RNA-level changes—jumped from under 10 percent during fetal stages to 12.8 percent at P1, 23 percent at P28, and 27.7 percent at P120. At P28, these Type 2 genes were enriched in ribosome biogenesis, lysosome function, and basal transcription factors, and gene set enrichment analysis linked them to fatty acid metabolism, a pathway known to run at higher activity in slow fibers. At P120, Type 5 genes, whose RNA and protein levels move in opposite directions, were enriched in the mTOR signaling pathway and lipoic acid metabolism. The message is clear: RNA sequencing alone would miss much of what actually drives muscle fiber specialization.

From the protein domain analysis came the study’s headline discovery. The serine/threonine kinase domain S_TKc was enriched in specific abundance trends in both muscles, but the proteins carrying it showed region-specific temporal patterns. One of these, NEK3—Never In Mitosis Gene A-Related Kinase 3—appeared as a differentially abundant protein between the two muscles at P1 with a striking log2 fold change exceeding 10, yet its RNA levels remained identical between regions throughout development. That discrepancy pointed to post-transcriptional control, and it is precisely the kind of regulatory mechanism that only a combined proteomic-transcriptomic approach can catch. The team used AlphaFold3 to model NEK3’s structure, then moved to the laboratory to test its function.

The functional experiments delivered a consistent verdict. When the researchers overexpressed NEK3 in mouse C2C12 myoblasts, MYHC expression dropped significantly, confirmed by both immunofluorescence and quantitative PCR. Western blotting showed that NEK3 overexpression suppressed MYH4, a fast-twitch fiber marker, while boosting MYH7 and PGC-1α, both hallmarks of slow oxidative fibers. The team then repeated the experiments in porcine embryonic muscle progenitor cells isolated from Bama pigs at 35 days post-coitum—a more physiologically relevant system—and observed the same pattern: fewer myotubes formed, and fast-twitch markers declined. NEK3, in short, acts as a conserved negative regulator of fast-twitch muscle fiber differentiation, and its transient, protein-only appearance at P1 suggests it helps orchestrate the fiber-type decisions made in the critical days after birth.

A second regulator, NCOA2, added another layer of nuance. This nuclear receptor coactivator, known to promote myogenic differentiation through the MEF2C pathway, showed distinct temporal patterns in the two muscles. In the fast-twitch longissimus dorsi, NCOA2 abundance began declining at E73 and vanished by P28; in the slow-twitch semitendinosus, the decline started later, at E90, and did not reach zero until P120. Because most fetal pig muscle fibers start life with slow-twitch characteristics, the researchers interpret NCOA2 as a molecular brake on the slow-to-fast transition: its early disappearance in the longissimus dorsi licenses that muscle to become fast, while its persistence in the semitendinosus preserves slow fiber identity deep into maturity.

Finally, the team widened the lens across species. Comparing 1,869 single-copy orthologous genes among pig, human, and mouse skeletal muscle at weaning-equivalent stages—postnatal day 28 in pigs, day 20 in mice, and 7 months in humans—they found that pig-specific high-expression clusters were enriched in skeletal muscle organ development, circulatory system development, and heart development, while pig-specific low-expression clusters involved autophagy and insulin receptor signaling. Intriguingly, genes tied to lung development were also elevated in pigs at this stage, hinting at a coordinated developmental program in which maturing respiratory muscles provide the mechanical forces that drive lung maturation. For pig farmers, the P28 window coincides with weaning, the most economically sensitive moment in production, suggesting that management strategies protecting muscle development during this period could pay dividends in both meat quality and animal health. For biomedical researchers, the study offers a molecular roadmap of muscle maturation in one of the most important animal models of human physiology—and a reminder that the proteins, not just the genes, tell the fuller story.

Subject of Research: Dynamic changes in muscle fiber types across developmental stages of porcine skeletal muscle, analyzed by integrated proteomics and transcriptomics

Article Title: Integrated proteomics and transcriptomics analysis of dynamic changes in muscle fiber types in different regions of porcine skeletal muscle

Article References: Integrated proteomics and transcriptomics analysis of dynamic changes in muscle fiber types in different regions of porcine skeletal muscle. (n.d.). https://doi.org/10.1007/s44307-025-00080-w

Image Credits: AI Generated

DOI: 10.1007/s44307-025-00080-w

Keywords: skeletal muscle, muscle fiber types, proteomics, transcriptomics, Bama miniature pig, NEK3, NCOA2, mitochondria, myogenesis, meat quality, data-independent acquisition, postnatal development

The case for MuSCs rests on their intrinsic commitment to the myogenic lineage. Unlike pluripotent stem cells, which require elaborate and tightly controlled differentiation protocols before they reliably become muscle, or mesenchymal stromal cells, which convert into muscle fibers only with variable and often disappointing efficiency, MuSCs are already wired for the job. In living animals they are responsible for growth, repair, and regeneration of skeletal muscle, and when activated by environmental cues they proliferate, differentiate, and fuse into the multinucleated myofibers that give meat its characteristic texture. That lineage fidelity translates into straightforward induction conditions in the laboratory and a direct biological relevance to the tissue being reconstructed. Because MuSCs can be harvested directly from livestock skeletal muscle, the resulting cultured product begins its life with the same cellular identity as conventional meat, which is precisely what regulators and consumers will scrutinize.

The catch is that MuSCs, like other primary cells, are mortal in culture. During extended in vitro passage they undergo phenotypic drift and eventually replicative senescence, progressively losing both proliferative capacity and myogenic potential. For a commercial process that may require many population doublings to accumulate enough biomass, this finite lifespan is a fundamental constraint. The review emphasizes that performance also varies with species, breed, donor age and sex, and even the anatomical origin of the muscle from which the cells are isolated. One cited study found that MuSCs from Hanwoo steers proliferated faster and doubled more quickly than cells from Hanwoo cows, with distinct marker expression profiles and differentiation kinetics. The authors call for standardized reporting of population doubling time, proliferation rate, differentiation kinetics, and fusion efficiency so that results from different laboratories can be meaningfully compared and robust cell lines identified.

Understanding myogenesis at the molecular level is the second pillar of the roadmap. Myogenic regulatory factors, including MYF5, MYOD, myogenin, and MRF4, orchestrate the progression from quiescent stem cell to fused myotube, and their expression serves as the standard molecular readout of myogenic status. Growth factors modulate every step of this cascade: IGF-1 drives growth and protein synthesis, FGF-2 sustains the proliferation of bovine and porcine MuSCs while delaying premature differentiation, PDGF promotes myoblast expansion, HGF wakes quiescent cells, and TGF-beta participates in repair and matrix remodeling but can suppress myogenesis depending on context. Beyond the classic factors, immune-derived cytokines exert surprisingly powerful effects. Interleukin-6 significantly enhanced bovine satellite cell proliferation in serum-free media in one study, interleukin-15 promotes myosin heavy chain accumulation, and interleukin-4 drives the secondary fusion step that builds mature myofibers. Myokines such as decorin, which sequesters the muscle-growth inhibitor myostatin in the extracellular matrix, and irisin add further layers of regulation.

Myostatin itself emerges as one of the most promising molecular levers. A member of the TGF-beta superfamily, myostatin is a potent negative regulator of muscle growth, and its genetic disruption in mice and double-muscled cattle produces dramatic increases in muscle mass. In culture, inhibiting myostatin or its downstream SMAD2/3 signaling enhances MuSC differentiation, promotes myotube formation, and upregulates key myogenic markers. Notably, computational docking screens of natural product databases have identified food-relevant plant compounds, including licochalcone A and B, quercetin, and laxogenin, as candidate myostatin inhibitors, and subsequent experimental work showed that these compounds can enhance MuSC proliferation and differentiation or protect cells from oxidative stress. The review is careful to note that such in silico hits are hypothesis generators, not proven ingredients, and that most evidence still comes from rodent or cell-line models rather than primary livestock cells.

That caveat points to the field’s most stubborn bottleneck: the culture medium. Standard formulations rely on fetal bovine serum, an animal-derived cocktail that is expensive, compositionally variable from batch to batch, ethically fraught, and incompatible with a food product meant to reduce reliance on livestock. Serum-free and chemically defined media exist, and formulations such as Beefy-9 have supported sustained expansion of bovine satellite cells across multiple passages while preserving myogenicity, but optimal compositions are highly species- and stage-specific. Media must also be modulated across the process, with expansion formulations maintaining progenitor states and differentiation formulations triggering myotube formation. Economic analyses cited in the review estimate that culture media, particularly the recombinant growth factors used in serum-free systems, can account for roughly half or more of variable operating costs, making media design the decisive battleground for affordability.

This is where artificial intelligence enters the story. The review highlights Bayesian optimization approaches that have streamlined serum-free medium development for myoblasts, multi-objective AI designs that produced low-serum media with reduced cost and environmental impact, and machine learning frameworks that predict the quality and senescence state of porcine and Hanwoo muscle satellite cells from microscopy images alone. Computational screening of vast natural product libraries such as COCONUT, LOTUS, and ZINC can prioritize candidate bioactive compounds, growth factor substitutes, and even antibiotic alternatives before a single wet-lab experiment is run. The authors stress, however, that docking scores and predictions demand rigorous experimental validation of solubility, cytotoxicity, and effective concentrations in food-relevant cells, and that AI should be treated as a complement to, not a replacement for, experimental optimization.

Even with perfect cells and perfect media, meat is a three-dimensional structure, and recreating it is an engineering problem. Skeletal muscle is organized into hierarchical bundles of aligned myofibers wrapped in endomysium, perimysium, and epimysium, and its texture depends on fiber density, alignment, and the extracellular matrix proteins, chiefly collagens, laminins, and fibronectin, that scaffold the whole assembly. Scaffold research is shifting from generic tissue-engineering materials toward edible, food-grade options: soy protein porous scaffolds, whey protein isolate composites, zein-coated alginate fibers that align muscle cells, and decellularized mushroom-derived matrices that produced steak-like constructs with authentic texture. At production scale, anchorage-dependent MuSCs are grown on microcarriers in stirred-tank bioreactors, where recent work has demonstrated bovine satellite cell expansion at microcarrier concentrations up to 80 square centimeters per milliliter and transfer to 3-liter vessels, while edible soy protein microcarriers enabled a 24-fold expansion of bovine myoblasts in eight days followed by differentiation without any cell detachment step.

Safety, regulation, and environmental accounting complete the picture. Hazards span microbial contamination, residual antibiotics and reagents, genetic and phenotypic drift during prolonged culture, and the composition of any scaffold that remains in the final product, and the review argues for risk-based frameworks built on HACCP principles and good manufacturing practice rather than blanket rules. Regulatory pathways are already diverging, with Singapore treating cultured meat as a novel food requiring pre-market safety assessment while the US FDA and USDA share oversight. Life cycle assessments, meanwhile, show that environmental performance is exquisitely sensitive to energy sources, media purification, and production scale, meaning that generalized claims about cultured meat’s footprint should be treated with caution. The authors’ bottom line is that cultured meat will succeed only through integration: stable, well-characterized MuSC sources; defined, food-grade, affordable media; scalable bioprocesses; engineered tissue architecture; and AI-guided optimization, all tracked with quantitative benchmarks of productivity, differentiation efficiency, cost, and safety. The cells are willing. The challenge now is industrial.

Subject of Research: Muscle stem cell cultivation strategies and technical barriers for scalable cultured meat production

Article Title: MuSC cultivation for cultured meat production: recent advances, current limitations, and future directions

Article References: MuSC cultivation for cultured meat production: recent advances, current limitations, and future directions. (n.d.). https://doi.org/10.1007/s44463-026-00108-2

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00108-2

Keywords: cultured meat, muscle stem cells, myogenesis, serum-free media, myostatin, scaffolds, bioreactors, microcarriers, artificial intelligence, food safety, life cycle assessment, bioprocess engineering

The stakes are considerable. Skeletal muscle is the body’s largest protein reservoir and its principal site of glucose disposal, and its maintenance underpins metabolic health and healthy aging. After the age of 50, muscle mass typically declines by 1 to 2 percent per year and strength by 1.5 to 3 percent, a loss that culminates in sarcopenia, a condition linked to disability and increased mortality. With the global population aged 65 and over projected to exceed 1.5 billion by 2050, sarcopenia has become a leading public health concern. What is changing the field, however, is the recognition that chronological age is not the only driver. Environmental exposures, particularly endocrine-disrupting chemicals, are increasingly implicated in the premature onset of muscle degeneration, and human studies have associated the burden of these chemicals with lower muscle mass, reduced strength, and even acceleration of biological age.

BPA is among the most prevalent of these chemicals. It leaches continuously from polycarbonate plastics, epoxy-resin can linings, thermal paper receipts, and medical devices, making human exposure effectively unavoidable. Experimentally, BPA reproduces three features of degenerative muscle aging. It promotes mitochondrial dysfunction and excess generation of reactive oxygen species, which damage macromolecules including DNA. It impairs the proliferation and differentiation of C2C12 myoblasts, a widely used mouse muscle cell line, and reduces myotube formation, the cellular process by which individual muscle cells fuse into functional fibers. And chronic exposure shortens survival and impairs locomotor performance in model organisms. These three axes are not independent: redox imbalance itself modifies myogenic differentiation and anabolic signaling, which means an intervention acting on the antioxidant response could plausibly influence the entire muscle-building program.

The Thai team, led by Woorawee Inthachat and colleagues at Mahidol University, began with the peel itself. Pomelo, Citrus maxima, is the largest of the citrus fruits, and its peel is rich in flavonoids such as naringin, hesperidin, and neohesperidin, along with phenolic acids and coumarins. Rather than using conventional hours-long solvent extraction, the researchers applied microwave-assisted extraction optimized through a Box-Behnken design and response surface methodology, testing 15 combinations of ethanol concentration, microwave power, and extraction time. The winning condition, 70 percent aqueous ethanol at 600 watts for just 60 seconds, yielded a total phenolic content of 21.98 milligrams of gallic acid equivalent per gram of dry weight, notably higher than the 15.79 milligrams obtained from the same peel with a four-hour water bath extraction in earlier work. The microwave’s internal superheating ruptures plant cell walls and accelerates mass transfer, compressing a process that once took hours into a single minute and cutting energy consumption in the bargain.

Chemical profiling by liquid chromatography with tandem mass spectrometry revealed that naringenin dominated the extract after acid hydrolysis, reaching 2,722.60 micrograms per gram of dry weight, with smaller amounts of apigenin and isorhamnetin. Because these aglycones appeared only after hydrolysis, the flavonoids in the native peel exist mainly as glycosides. The extract also showed strong antioxidant activity, particularly in the oxygen radical absorbance capacity assay, which registered 1,198.39 micromoles of Trolox equivalent per gram of dry weight. Armed with this characterization, the team turned to whole organisms, feeding the extract to Canton-S fruit flies at 125 and 250 micrograms per milliliter, alongside two positive controls: resveratrol, a well-characterized anti-aging compound, and naringenin at the dose corresponding to its concentration in the higher extract dose.

The fly results were striking. Chronic exposure to 0.05 millimolar BPA slashed median survival from about 28 days to 19 days in females and 17 days in males, a roughly 40 percent reduction. Co-supplementation with the pomelo peel extract at 250 micrograms per milliliter pushed median survival back to 24.33 days in females and 22.00 days in males, an effect statistically comparable to the positive controls. A feeding assay confirmed the benefit was not an artifact of caloric restriction or food avoidance. BPA also devastated climbing ability, a functional proxy for neuromuscular integrity, but flies receiving the extract maintained climbing indices close to unexposed controls through day 14. At the molecular level, BPA induced the antioxidant genes Cat, Sod1, and Gstd1, the master redox regulator Cnc, the fly homolog of mammalian Nrf2, and the DNA repair gene Ogg1, all hallmarks of a systemic oxidative stress response. The extract returned these transcripts toward baseline and lowered measured reactive oxygen species, while also normalizing Him, a gene whose product inhibits the myogenic transcription factor Mef2 and whose overexpression promotes muscle degeneration.

In parallel, the researchers tested the extract in C2C12 mouse myoblasts differentiating in the presence of 40 micromolar BPA, a concentration chosen because it substantially impairs muscle cell function without causing generalized cytotoxicity. BPA alone left the cells predominantly triangular and mononuclear, with little conversion into elongated, multinucleated myotubes. Co-treatment with the extract at 30 to 50 micrograms per milliliter significantly restored the fusion index, the proportion of nuclei incorporated into multinucleated myotubes, and recovered muscle fiber diameter to values comparable to or slightly above the differentiated control. Western blotting showed that BPA reduced the myogenic transcription factors myogenin and MEF2A, and that the extract significantly increased MEF2A at 20 and 30 micrograms per milliliter. The extract also reactivated the Akt/4E-BP1 anabolic signaling axis, a key regulator of muscle protein synthesis that BPA is known to suppress, raising phospho-Akt at three doses and phospho-4E-BP1 at an intermediate dose.

One nuance deserves attention. The extract was not biologically inert in healthy flies. In males, supplementation alone caused a mild but statistically significant reduction in median lifespan of roughly 13 to 15 percent, without a clear dose-response pattern. The authors interpret this through the lens of mitohormesis: low levels of reactive oxygen species serve essential signaling functions in unstressed organisms, and excessive antioxidant activity can suppress these beneficial signals. The pattern also reflects sexual dimorphism in fly metabolism and detoxification, and possibly the estrogenic activity of naringenin, which can bind both subtypes of the mammalian estrogen receptor and influence muscle cell differentiation. Fruit flies lack classical estrogen receptor signaling, so the fly and cell results may arise through partly different mechanisms. The practical implication is that pomelo peel extract is better regarded as a protective intervention under conditions of oxidative stress or pollutant exposure than as a general lifespan-promoting supplement for healthy individuals, and formal safety margins would need to be established before any functional-food development.

The study also has honest limits. The concentrations used are proof-of-concept exposures rather than human-equivalent doses, although the estimated naringenin levels fall within the low-micromolar range measured in human plasma after citrus consumption. Humans are exposed to complex mixtures of endocrine disruptors, not a single chemical, and the researchers did not measure direct oxidative DNA damage, antioxidant enzyme activities, or canonical atrophy markers such as MuRF1 and Atrogin-1. Notably, the extract did not reduce BPA-induced reactive oxygen species in the differentiating muscle cells even as it restored myogenesis, suggesting the cellular protection may operate through redox-sensitive signaling rather than direct radical scavenging, a distinction that remains to be tested directly.

Even with those caveats, the convergence of evidence is compelling: a one-minute microwave extraction of an agricultural waste product, optimized by statistical design, extended survival and preserved muscle function in BPA-poisoned flies while rebuilding muscle fibers and anabolic signaling in poisoned muscle cells. If further validation in mammalian models holds up, the humble pomelo peel, currently composted or burned by the ton, could become a nutraceutical resource for mitigating the muscle-wasting and accelerated aging that our chemical environment increasingly imposes. It is a vivid example of circular economy science at its most concrete: turning trash into a shield against the toxic legacy of the plastics age.

Subject of Research: Protective effects of optimized pomelo peel extract against bisphenol A-induced oxidative stress, premature aging, and impaired muscle cell differentiation

Article Title: Valorization of microwave-assisted optimized pomelo peel extract mitigates bisphenol A–induced oxidative stress and premature aging in Drosophila and disruption of myogenesis in C2C12 cells

Article References: Inthachat, W., Wudtiwai, B., Umsumarng, S., Buacheen, P., Thangsiri, S., Suttisansanee, U., Pitchakarn, P., & Temviriyanukul, P. (2026). Valorization of microwave-assisted optimized pomelo peel extract mitigates bisphenol A–induced oxidative stress and premature aging in Drosophila and disruption of myogenesis in C2C12 cells. Journal of Agriculture and Food Research, 31, Article 103318. https://doi.org/10.1016/j.jafr.2026.103318

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103318

Keywords: pomelo peel, bisphenol A, endocrine disruptors, oxidative stress, sarcopenia, Drosophila, C2C12 myoblasts, naringenin, microwave-assisted extraction, antioxidants, myogenesis, healthy aging

Cachexia is one of oncology’s most feared complications. More than half of patients with advanced non-small cell lung cancer, which accounts for over 85 percent of lung cancer cases, develop the syndrome, which is characterized by anorexia, progressive weight loss and the relentless erosion of skeletal muscle and fat. Unlike simple malnutrition, cachexia cannot be reversed with nutritional support alone. It is driven by systemic inflammation and profound metabolic dysregulation, and it directly contributes to as much as 20 percent of all cancer-related deaths. Patients with cachexia tolerate anti-tumour therapies poorly, suffer diminished quality of life and die sooner. Despite decades of research, no effective pharmacological therapy exists, leaving clinicians to rely on multimodal strategies aimed at reducing inflammation, preserving lean body mass and improving appetite.

The research team, led by Yingjia Zhou, Shaoli Zhao and Huantian Cui, chose Huangqi Guizhi Wuwu Decoction, commonly abbreviated HGWD, because of its well-documented immunomodulatory, anti-inflammatory and microcirculatory properties. The formula is already used clinically in China to manage metabolic dysfunction and immune dysregulation, particularly chemotherapy-related side effects such as peripheral neuropathy. Yet its potential role in tumour-induced cachexia had never been examined. To test it, the researchers implanted Lewis lung carcinoma cells into eight-week-old male C57BL/6 mice, a widely used model of lung cancer cachexia, and randomly assigned fifty animals to five groups: tumour-free controls, untreated cachectic mice, mice treated with the chemotherapy drug cisplatin, and cachectic mice given either a low or high dose of HGWD by daily gastric gavage for fourteen consecutive days.

The results were unambiguous. By days seven and fourteen of treatment, untreated cachectic mice showed a marked decline in grip strength and wire-hang endurance, while mice receiving the high dose of HGWD maintained significantly greater muscle strength. Cisplatin, notably, failed to improve muscle function and in some measures made matters worse. HGWD also increased tumour-free body weight, gastrocnemius and quadriceps muscle mass, and epididymal fat mass, all of which were severely depleted in the untreated cachectic animals. Histological examination confirmed the protective effect: the cross-sectional area of skeletal muscle fibres, which shrank dramatically in cachectic mice, was substantially preserved in the HGWD-treated groups.

At the molecular level, the remedy appeared to reinvigorate the muscle’s own building machinery. Cachectic mice showed sharp reductions in MYHC, MYOD1 and MYOG, proteins essential for myogenesis, along with elevated ATROGIN-1, a key marker of muscle atrophy. HGWD partially restored the myogenic proteins and suppressed ATROGIN-1. The treatment also corrected metabolic and oxidative stress abnormalities in the muscle: glycogen levels, which had collapsed, recovered; lactic acid accumulation diminished; the antioxidant enzymes superoxide dismutase and glutathione peroxidase rebounded; and malondialdehyde, a marker of lipid peroxidation, fell. Intriguingly, HGWD also reduced tumour volume and weight, whereas cisplatin did not rescue, and sometimes worsened, the wasting parameters despite its antitumour action. HGWD-treated mice additionally ate and drank more, a factor the authors acknowledge could contribute to the improvements.

To uncover the mechanism, the team turned to transcriptome sequencing of the gastrocnemius muscle. Comparing untreated cachectic mice with healthy controls revealed widespread disruption of pathways including amino acid biosynthesis, cysteine and methionine metabolism, arginine and proline metabolism, glycolysis, the HIF-1 signalling pathway and cytokine receptor interactions. When the high-dose HGWD group was compared with the untreated cachectic group, the picture shifted dramatically: the most enriched pathways were again dominated by amino acid metabolism, alongside the PPAR signalling pathway, cholesterol metabolism, galactose metabolism and calcium signalling. Crucially, HGWD markedly upregulated genes encoding motor proteins, including Myhas, Mylpf and Myl1, which are critical for maintaining muscle mass, driving myogenesis and regulating contractility.

Untargeted metabolomics of the same muscle tissue told a complementary story. Principal component and discriminant analyses showed that HGWD substantially reshaped the aberrant metabolite profile of cachectic muscle, and pathway enrichment again pointed squarely at amino acid biosynthesis. Among the metabolites restored by the treatment were S-adenosylmethionine, known as SAM, L-arginine, L-tryptophan, L-ornithine, L-leucine and spermidine. Each of these molecules has established links to muscle health: arginine and leucine supplementation has been shown to partially mitigate cachexia in prior studies, accelerated tryptophan catabolism contributes to sarcopenia, ornithine supports mitochondrial and redox function in wasting states, and spermidine plays a well-documented role in protecting against muscle ageing and preserving muscle homeostasis.

The deepest insight came from integrating the two datasets. The researchers found that HGWD upregulated the genes Amd1, Amd2 and Smox while downregulating Gnmt. AMD1 and AMD2 are rate-limiting enzymes that convert SAM into decarboxylated SAM, supplying the propylamine groups needed to synthesize polyamines such as spermidine. SMOX then converts decarboxylated SAM into spermidine, and its expression positively correlates with muscle mass and function. GNMT, by contrast, channels SAM toward S-adenosylhomocysteine, and its dysregulation lowers the SAM/SAH ratio, a change closely linked to muscle ageing and cachexia progression. Western blot analysis confirmed the pattern at the protein level: AMD1 and SMOX rose, GNMT fell. The authors propose that HGWD alleviates cachexia by suppressing GNMT, raising the SAM/SAH ratio and enhancing the conversion of SAM into spermidine, thereby restoring amino acid metabolic homeostasis in skeletal muscle.

The study is not without caveats, which the authors address candidly. Because HGWD also reduced tumour burden and increased food intake, the muscle-protective effect could be secondary to reduced tumour-derived catabolic signalling or improved nutrition rather than a direct metabolic action within muscle tissue; a pair-feeding experiment would be needed to disentangle these possibilities. The findings are also correlational, lacking direct causal proof, and the specific bioactive compounds within the multi-herb formula responsible for the effect remain unidentified. The team plans follow-up work using in vitro myotube atrophy models treated with HGWD-containing serum, combined with siRNA knockdown of AMD1 or SMOX and enzyme inhibitors, alongside multi-omics integration and target-validation techniques such as surface plasmon resonance and drug affinity responsive target stability assays.

Even so, the implications are considerable. With no approved pharmacological therapy for cancer cachexia and more than half of advanced lung cancer patients affected, a well-tolerated, orally available formula that simultaneously preserves muscle, corrects metabolic derangement and modestly inhibits tumour growth represents an unusually attractive therapeutic profile. The identification of the SAM-to-spermidine axis as a plausible mechanism also gives researchers a concrete molecular handle for drug development, whether inspired by the herbal formula itself or by synthetic compounds that mimic its enzymatic effects. For now, the work stands as a rigorous, multi-omics demonstration that a medicine brewed from herbs first described centuries ago can act on modern molecular targets, and it opens a promising path toward clinical evaluation of HGWD in patients whose cancers are stealing their muscle, strength and time.

Subject of Research: Mechanisms of a traditional Chinese medicine formula in treating lung cancer–induced cachexia through amino acid metabolism regulation

Article Title: Huangqi Guizhi Wuwu Decoction Ameliorates Cachexia in Lung Cancer Mice Through Regulating Amino Acid Metabolism: Insights From Transcriptomics, Metabolomics and Experimental Validation

Article References: Zhou, Y., Zhao, S., Shen, H., Wu, J., Li, M., Liu, S., Yang, J., Jin, X., Li, F., & Cui, H. (2026). Huangqi Guizhi Wuwu Decoction Ameliorates Cachexia in Lung Cancer Mice Through Regulating Amino Acid Metabolism: Insights From Transcriptomics, Metabolomics and Experimental Validation. Journal of Cellular and Molecular Medicine, 30(19), Article e71387. https://doi.org/10.1111/jcmm.71387

Image Credits: AI Generated

DOI: 10.1111/jcmm.71387

Keywords: cancer cachexia, lung cancer, Huangqi Guizhi Wuwu Decoction, traditional Chinese medicine, amino acid metabolism, spermidine, S-adenosylmethionine, skeletal muscle atrophy, transcriptomics, metabolomics, Lewis lung carcinoma, myogenesis

The research, led by Dora Gjirlić, Anja Weber, Guido Posern, and Anurag Kumar Singh of the Institute for Physiological Chemistry, focuses on the actin-depolymerizing factor/cofilin family, a group of proteins that sever and depolymerize actin filaments, thereby controlling the constant turnover of the cytoskeleton. Vertebrates possess two major isoforms: Cofilin-1, which is broadly expressed in many cell types, and Cofilin-2, which is characteristic of muscle tissue. Although both proteins perform the same core biochemical task — cutting filamentous actin into globular subunits — their roles during myogenesis, the process by which muscle cells form, have remained incompletely understood. The new work provides the most detailed picture yet of how these isoforms are swapped during muscle differentiation and why that swap matters.

Using the immortalized mouse myoblast cell line C2C12, a workhorse of muscle biology, the team tracked the expression of both cofilin isoforms as cells transitioned from growth medium into differentiation medium. What emerged was a pronounced isoform switch. As differentiation proceeded, Cofilin-1 and the related Actin-Depolymerizing Factor (ADF) were progressively downregulated, while Cofilin-2 expression rose. Analyses of messenger RNA and protein stability indicated that this switching is controlled primarily at the level of gene expression rather than through altered degradation of the proteins themselves, suggesting that transcriptional reprogramming sits at the heart of the isoform transition.

To probe function rather than mere correlation, the researchers deployed an impressive arsenal of techniques. They used CRISPR/Cas9 genome editing to knock out the Cofilin-1 gene, shRNA-mediated knockdown to deplete it partially, immunofluorescence microscopy to visualize cellular morphology, quantitative gene expression analyses to monitor myogenic marker genes, MRTF reporter assays to measure the activity of the myocardin-related transcription factor A, and pharmacological inhibition of LIM kinase to block a key regulatory phosphorylation pathway. Each approach interrogated a different facet of the same question: what happens to differentiating muscle cells when the actin-severing machinery is perturbed?

The answer, for complete loss of Cofilin-1, was dramatic. Cells lacking the protein developed marked morphological abnormalities, failed to exit the cell cycle properly, showed elevated MRTF activity, and formed far fewer myotubes — the multinucleated structures that represent successful differentiation. This constellation of defects makes mechanistic sense. MRTF-A is a transcriptional coactivator whose nuclear activity is restrained by binding to globular actin; when actin polymerization dynamics are disturbed and the monomeric actin pool shifts, MRTF signaling can be unleashed inappropriately. Cofilin-1, by regulating the filament-monomer balance, normally helps keep this signaling pathway calibrated during the transition from proliferation to differentiation. Remove it entirely, and the cell’s transcriptional program falls out of register with its cytoskeletal state.

The most striking discovery, however, came from the knockdown experiments. When the researchers reduced Cofilin-1 only partially, something unexpected happened: myoblast fusion was enhanced. Cells with modestly lowered Cofilin-1 fused with their neighbors more readily than controls. But when depletion was pushed harder, the opposite occurred — differentiation collapsed and myotube formation was impaired. This bidirectional response demonstrates a dosage-sensitive requirement for Cofilin-1, a Goldilocks principle in which the protein must be present at precisely the right level. Too much Cofilin-1 appears to restrain fusion, while too little disrupts the cytoskeletal remodeling that fusion itself requires. The finding adds muscle formation to a growing list of biological processes in which gene dosage, rather than simple presence or absence, determines the outcome.

Cofilin-2 deficiency, by contrast, produced comparatively mild effects during early differentiation. This asymmetry is intriguing because Cofilin-2 is the isoform ultimately enriched in mature muscle. The results suggest that the two isoforms, despite their biochemical similarity, are not interchangeable in function or timing: Cofilin-1 is the critical regulator of the early, decision-making phase of myogenesis, whereas Cofilin-2 likely assumes importance later, in the context of mature contractile fibers. The progressive switch from one isoform to the other may therefore represent a carefully staged handover of cytoskeletal control, timed to the changing needs of the cell as it commits to the muscle lineage.

The study also illuminates how Cofilin-1’s activity, not just its abundance, is regulated during myogenesis. The researchers found that Cofilin-1 undergoes transient phosphorylation by LIM kinase during early differentiation. Phosphorylation by LIM kinase — which itself sits downstream of the Rho-associated kinase ROCK — inhibits cofilin’s actin-severing capacity, stabilizing actin filaments at specific moments. When the team blocked this pathway with the LIM kinase inhibitor LIMKi3 (BMS-5), myogenic progression was disrupted. The picture that emerges is one of dynamic, moment-to-moment control: the cell not only dials down Cofilin-1 expression over the course of differentiation but also rapidly toggles the remaining protein on and off through phosphorylation, fine-tuning actin turnover as the cell cycle exits and fusion machinery engages.

These findings connect several threads of muscle biology that had previously run in parallel. The actin cytoskeleton must be dismantled and rebuilt for a myoblast to elongate and fuse; the MRTF and serum response factor (SRF) transcriptional pathway reads actin dynamics and translates them into gene expression; and the myogenic regulatory factors MyoD and myogenin drive the differentiation program, with myomaker and myomixer/myomerger executing the fusion step itself. The new work positions Cofilin-1 as a molecular link between the physical and the transcriptional layers of this process — a dosage-sensitive node where cytoskeletal remodeling is converted into signals that govern proliferation, differentiation, and ultimately cell fusion. Caveolin-3, myosin heavy chain, and other differentiation markers tracked in the study provided the readouts confirming that these signaling changes translate into real changes in myogenic identity.

Beyond its immediate significance for understanding how skeletal muscle forms, the research carries potential implications for regenerative medicine and muscle disease. Muscle regeneration after injury recapitulates many steps of embryonic myogenesis, including the fusion of satellite-cell-derived myoblasts onto damaged fibers. If Cofilin-1 dosage and LIM kinase signaling set the efficiency of that fusion, they become candidate levers for improving muscle repair — or potential culprits in conditions where repair fails. The Halle team, whose work was supported by internal faculty core funding from Martin Luther University Halle-Wittenberg and enabled by open-access funding through Projekt DEAL, emphasizes that coordinated regulation of Cofilin-1 expression and activity, together with the timely transition to Cofilin-2, is required for efficient myoblast fusion and muscle formation. In revealing that a humble actin-severing protein must be tuned like an instrument rather than simply switched on or off, the study adds a subtle but essential rule to the growing rulebook of how cells build tissue.

Subject of Research: Dosage-sensitive regulation of Cofilin-1 and LIM kinase signaling in myoblast differentiation and fusion

Article Title: Dosage-sensitive regulation of Cofilin-1 and LIMK signaling controls myoblast differentiation and fusion

Article References: Gjirlić, D., Weber, A., Posern, G., & Singh, A. K. (2026). Dosage-sensitive regulation of Cofilin-1 and LIMK signaling controls myoblast differentiation and fusion. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06437-1

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06437-1

Keywords: myogenesis, Cofilin-1, Cofilin-2, actin cytoskeleton, LIM kinase, MRTF signaling, myoblast differentiation, cell fusion, cytoskeletal regulation, skeletal muscle, Dosage-sensitive, regulation

The research team, led by Jing Pan and Tzu-Shao Yeh of the Department of Nutrition and Food Hygiene at Nantong University in China, together with Luthfia Dewi of Universitas Muhammadiyah Semarang in Indonesia, focused their experiments on C2C12 cells, a widely used mouse skeletal muscle cell line that recapitulates key stages of muscle formation. These cells can be induced to behave like satellite cells, the resident stem cells of skeletal muscle, and to progress through the full differentiation program that turns undifferentiated myoblasts into mature, multinucleated myotubes, the cellular equivalent of muscle fibers. By treating these cells with boswellic acid and measuring changes at both the RNA and protein levels, the investigators were able to map the compound’s effects across the entire myogenic cascade.

The results were striking at multiple points along this cascade. Boswellic acid treatment produced a 17 percent increase in the number of Pax7-positive cells. Pax7 is the canonical marker of satellite cell identity and quiescent muscle stemness, and an expanded Pax7-positive population suggests that the compound preserves or expands the pool of cells capable of regenerating damaged or aging muscle tissue. This is a critical finding for the muscle aging field, because one hallmark of aged muscle is the depletion and dysfunction of its satellite cell reserve, leaving old muscles increasingly unable to repair themselves after injury, disuse, or disease.

Beyond stemness, the compound appeared to push cells more rapidly through the commitment and differentiation stages of muscle formation. The researchers quantified the relative messenger RNA levels of four master regulators of myogenesis: Pax7, Myf5, MyoD, and MyoG. These myogenic regulatory factors act in a choreographed sequence, with Pax7 maintaining the stem cell state, Myf5 and MyoD committing cells to the muscle lineage, and myogenin driving terminal differentiation and fusion into myotubes. Following boswellic acid treatment, the mRNA and protein levels of Myf5, MyoD, and MyoG were all significantly upregulated, indicating that the treated cells were accelerating through the myogenic differentiation program. The study also documented a two to four hour advancement in the myoblast renewal cycle, suggesting that the compound speeds the temporal rhythm by which muscle precursor cells proliferate and renew themselves before differentiating.

Protein-level confirmation came from Western blotting, a technique that separates proteins by molecular weight and detects them with specific antibodies. The team measured protein expression of Pax7, Myf5, MyoD, and MyoG, alongside loading controls such as beta-actin and GAPDH, and found the upregulation observed at the RNA level faithfully mirrored at the protein level. Immunofluorescence staining was used to visualize Pax7 and MyoD expression within individual cells, providing spatial confirmation that the molecular changes translated into shifts in the cellular populations themselves. Cell viability was assessed with the XTT assay, ensuring that the observed pro-myogenic effects were not simply an artifact of compound toxicity or stress-induced changes in cell behavior.

Perhaps the most translationally intriguing results concern hypertrophy, the enlargement of existing muscle fibers. Boswellic acid treatment significantly enhanced myotube hypertrophy through activation of the canonical hypertrophic signaling axis: the Akt-mTOR-p70S6K pathway. This pathway is the central growth-control circuit of skeletal muscle, integrating signals from insulin-like growth factor 1, mechanical loading, and nutrient availability to drive protein synthesis. Akt, or protein kinase B, phosphorylates and regulates downstream targets including mTOR, the mammalian target of rapamycin, which in turn activates p70S6K, a ribosomal protein S6 kinase that promotes ribosomal biogenesis and translation of muscle proteins. The researchers observed increased phosphorylation of all three nodes, indicating that boswellic acid switches on the same anabolic program engaged by resistance exercise and IGF-1 signaling.

The convergence of two effects, expanded stem cell activity and heightened anabolic signaling, is what distinguishes this study from many single-mechanism nutraceutical investigations. Aging muscle fails on both fronts: satellite cells become less numerous and less responsive, and the Akt-mTOR axis becomes progressively resistant to the anabolic stimuli of food intake and exercise, a phenomenon sometimes called anabolic resistance. A compound that simultaneously supports the regenerative stem cell compartment and re-energizes protein synthesis signaling could, in principle, address both dimensions of sarcopenia. The authors suggest that boswellic acid warrants consideration as a nutraceutical agent to enhance muscle differentiation and hypertrophy, and as a potential novel therapeutic strategy for mitigating muscle aging.

Boswellic acid itself has a long pharmacological history. It is the principal bioactive component of frankincense, the resin of Boswellia serrata and related species, and has been studied extensively for its anti-inflammatory properties, particularly its inhibition of 5-lipoxygenase and its effects on inflammatory pathways relevant to arthritis and inflammatory bowel disease. This new study extends its potential repertoire into muscle biology, a domain more commonly occupied by compounds such as creatine, leucine, and other branched-chain amino acids, and by pharmaceutical agents under development for sarcopenia. The triterpenoid structure of boswellic acid allows it to interact with multiple signaling proteins, which may explain its pleiotropic effects across the myogenic program and the growth-factor cascade.

The authors are careful to frame the work within its in vitro limits. All experiments were conducted in murine cell cultures, and the physiological concentration, absorption, and tissue distribution of boswellic acid in living organisms remain open questions. Satellite cell behavior in aged muscle is shaped by a complex niche of inflammatory signals, extracellular matrix changes, and vascular decline that a simplified cell culture cannot fully reproduce. The researchers explicitly state that additional in vivo and clinical investigations are warranted before any therapeutic relevance can be established. Human trials would need to establish safe dosing, bioavailability, and whether oral supplementation can achieve tissue concentrations capable of activating the pathways observed in culture.

Even so, the study adds to a growing scientific effort to identify accessible dietary compounds that can bias the balance between muscle loss and muscle regeneration in favor of renewal. With sarcopenia estimated to affect a substantial share of adults over sixty and to drive frailty, falls, and loss of independence, the search for safe, well-tolerated interventions is intensifying. If future animal and human studies confirm the mechanisms reported here, boswellic acid, a molecule that humans have consumed for millennia in the form of frankincense, could emerge as an unusually well-characterized candidate for supporting muscle health across the lifespan. For now, the finding stands as a compelling proof of concept: an ancient resin component, examined with modern molecular tools, appears capable of speaking the native language of regenerating muscle.

Subject of Research: Effects of boswellic acid on myogenic and hypertrophic signaling in skeletal muscle cells as a potential strategy against muscle aging

Article Title: Boswellic acid modulates myogenic and hypertrophic signaling in vitro: implications for muscle aging

Article References: Pan, J., Dewi, L., & Yeh, T.-S. (2026). Boswellic acid modulates myogenic and hypertrophic signaling in vitro: implications for muscle aging. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05596-9

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05596-9

Keywords: boswellic acid, satellite cells, sarcopenia, muscle aging, myogenesis, skeletal muscle hypertrophy, Akt-mTOR-p70S6K, myogenic regulatory factors, nutraceutical, C2C12 cells, muscle regeneration, frankincense