The review, published in Frontiers in Endocrinology, synthesizes evidence on how skeletal cells—including bone marrow mesenchymal stem cells, osteoblasts and periodontal ligament stem cells—communicate with macrophages, osteoclast precursors, lymphocytes and other immune populations. It describes osteoimmunity as a cellular, molecular and metabolic network in which immune cells influence matrix remodeling while skeletal cells regulate immune responses.

Three routes were identified for transferring whole mitochondria between cells. Direct contact can involve actin-rich tunneling nanotubes, gap junctions or cell fusion, although the review notes debate over whether intact mitochondria pass directly through gap-junction channels. Extracellular vesicles can enclose intact mitochondria, fragments or mitochondrial DNA, while free mitochondria can be released into the extracellular space and captured by recipients through macropinocytosis or other phagocytic mechanisms.

Examples summarized in the review show that either direction of transfer can have different consequences. Osteolineage cells transferred mitochondria to myeloid osteoclast precursors were associated with improved glutathione metabolism, reduced ferroptosis and less bone resorption. Bone marrow mesenchymal stem cells also transferred mitochondria to T helper 17 cells, reducing interleukin-17 production and promoting conversion toward a regulatory T-cell phenotype. In contrast, mechanically compressed periodontal ligament fibroblasts released mitochondrial cargo in extracellular vesicles that activated the NLRP3 inflammasome in macrophages and induced caspase-1-dependent pyroptosis during orthodontic tooth movement.

Immune cells can also influence skeletal cells. Inflammatory macrophages transferred extracellular-vesicle-associated mitochondria to bone marrow mesenchymal stem cells, impairing osteogenic differentiation and exacerbating alveolar bone loss. By contrast, M2-like macrophages transferred functional mitochondria to injured periodontal ligament stem cells, activating p38 mitogen-activated protein kinase signaling and improving cell survival under inflammatory conditions. Separately, mechanical force activated Drp1 in macrophages and promoted EV-mediated mitochondrial transfer to mesenchymal stem cells through the CD200/CD200R axis, enhancing osteogenic differentiation in the cited experimental work.

The review emphasizes that the direction of transfer and the identity of the donor cell do not by themselves determine the outcome. Reactive oxygen species, hypoxia, inflammatory mediators and disrupted calcium homeostasis can alter mitochondrial dynamics and intercellular communication. The quality of donor mitochondria—including membrane potential, oxidative damage, cristae integrity and respiratory capacity—also matters. Functionally competent cargo can support oxidative phosphorylation, ATP production and redox balance, whereas damaged mitochondria or mitochondrial components can activate innate immune pathways. Recipient metabolic and lysosomal capacity and the surrounding microenvironment further shape the response.

The authors discuss pathological roles in osteoarthritis, osteoporosis and periodontitis. In osteoarthritis, mitochondrial material from stressed chondrocytes may be taken up by synovial macrophages and associated with TLR9, cGAS-STING and NLRP3 pathway activation, while M1-like macrophage EV-mitochondria can increase oxidative stress and chondrocyte dysfunction. In osteoporosis, impaired RIPK4-related mitochondrial dynamics and age-associated donor-cell dysfunction may weaken protective transfer to myeloid and osteogenic cells. In periodontitis, dysfunctional macrophage EV-mitochondria can suppress mesenchymal stem-cell osteogenic differentiation through the LCN2/OMA1/OPA1 pathway.

Four therapeutic categories are proposed: enhancing endogenous protective transfer, blocking pathological propagation, delivering exogenous mitochondria and engineering mitochondrial delivery. Reviewed interventions include functionalized iron oxide nanoparticles that improved aged macrophages in osteoporotic models, inhibitors of vesicle release or inflammasome signaling, and delivery of isolated mitochondria from mesenchymal stem cells to osteoarthritic chondrocytes. Engineered systems include hydrogels, responsive peptide complexes and mitochondrial carriers. These approaches are based mainly on cell-culture and animal evidence, and the review does not establish clinical efficacy in people.

Major limitations remain. Most evidence comes from in vitro studies and animal models, while standardized protocols are lacking for mitochondrial sourcing, isolation, dosing, characterization and safety evaluation. The review proposes a four-level evidence framework: direct in vivo tracing, direct in vitro imaging with functional testing, component-based evidence, and indirect evidence such as colocalization. Controls are needed to exclude dye leakage, cell fusion and uptake of apoptotic bodies, because fluorescence, mitochondrial DNA or mitochondrial proteins alone cannot prove transfer of intact mitochondria. The authors also call for assessment of purity, membrane integrity, respiratory activity, sterility, stability, biodistribution, immunogenicity and long-term toxicity before therapeutic mitochondria could advance toward clinical translation.

Subject of Research: Bidirectional mitochondrial transfer as a regulator of osteoimmune communication and bone disease

Article Title: Bidirectional mitochondrial transfer in the osteoimmune microenvironment: mechanisms and therapeutic perspectives

Article References: Huang, L., Chen, X., Guo, Y., Guo, F., Zhang, Y., Li, X., Dong, Z., & Kou, X. (2026). Bidirectional mitochondrial transfer in the osteoimmune microenvironment: mechanisms and therapeutic perspectives. Frontiers in Endocrinology, 17, Article 1978936. https://doi.org/10.3389/fendo.2026.1978936

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1978936

Keywords: mitochondrial transfer, osteoimmunity, bone remodeling, immunometabolism, mitochondrial quality control, extracellular vesicles, macrophages, mesenchymal stem cells, osteoporosis, osteoarthritis, periodontitis, Bidirectional

According to figures cited in the review, as many as half of women and a quarter of men over the age of fifty in the United States will suffer a fracture attributable to osteoporosis, while researchers in China predict the national patient count will reach 212 million by 2050. National epidemiological surveys place the prevalence of the disease at 19.2 percent among Chinese adults over fifty and 32 percent among those over sixty-five. Beyond the human toll, the economic burden of fractures and long-term care weighs heavily on families and health systems, fueling the search for interventions that could extend the preventive window before fractures ever occur.

Current pharmacotherapy, the review's authors emphasize, remains the cornerstone of clinical management but is far from perfect. Antiresorptive agents such as bisphosphonates and the RANKL antibody denosumab suppress the bone-resorbing cells known as osteoclasts, cutting vertebral fracture risk by 40 to 70 percent in some trials, yet they cannot rebuild lost bone and carry risks including osteonecrosis of the jaw and atypical femoral fractures. Denosumab poses a particular problem: discontinuation can trigger rapid rebound bone loss and a three- to five-fold increase in multiple vertebral fractures.

On the anabolic side, the parathyroid hormone analog teriparatide is capped at twenty-four months of use by the FDA, while the anti-sclerostin antibody romosozumab, despite reducing new vertebral fractures by up to 73 percent in the FRAME trial, raises cardiovascular safety concerns and is generally limited to twelve months of therapy. It is against this backdrop that the gut-bone axis has captured scientific attention. Bone health depends on a delicate balance between osteoblasts, which build bone, and osteoclasts, which dismantle it, and the gut microbiota appears to influence both sides of this equation through parallel channels.

In one striking example highlighted in the review, researchers identified microbial taxa associated with postmenopausal osteoporosis and then showed that supplementing mice with the candidate strain Prevotella histicola attenuated estrogen-deficiency-induced bone loss. The mechanism was elegantly indirect: the bacterium upregulated tight junction proteins such as ZO-1 and Occludin in the intestinal lining, reducing permeability and preventing inflammatory signals from reaching the skeleton, where they would otherwise fuel osteoclast overactivity. Probiotics themselves have now been dissected into functional categories.

Lactobacillus rhamnosus GG promotes bone formation through a butyrate-dependent mechanism involving regulatory T cells and WNT10B signaling. Lactobacillus reuteri ATCC PTA 6475 inhibits roughly 70 percent of RANKL-induced osteoclast precursor differentiation in vitro and significantly reduces bone loss in ovariectomized mice. Bifidobacterium longum 35624 blocks osteoclast formation via a TLR2-dependent pathway mediated by its surface exopolysaccharide.

Soluble metabolites add another layer: short-chain fatty acids shift osteoclast precursor metabolism toward glycolysis, triggering cellular stress that halts their differentiation, while butyrate suppresses osteoclast genes such as CTSK and c-Fos and simultaneously repairs the gut barrier, creating a linked gut-repair and bone-protection effect. Perhaps the most futuristic chapter concerns extracellular vesicles, or EVs, nanoscale lipid-enclosed particles shed by bacteria that ferry proteins, nucleic acids, and lipids between cells. Vesicles from the gut microbiome have been shown to physically reach bone tissue.

Extracellular vesicles from Akkermansia muciniphila upregulate osteogenic genes including Runx2 and Alpl while suppressing osteoclastogenic genes such as Trap and Ctsk, and oral administration of these vesicles significantly increased bone mass, bone length, and bone strength in ovariectomized mice. Vesicles from the pediatric gut microbiome restored Akkermansia abundance and reversed induced bone loss, while outer membrane vesicles from Proteus mirabilis inhibited osteoclastogenesis through the miR-96-5p/ABCA1 axis, a reminder that even vesicles from pathogenic bacteria can exert context-dependent osteoprotective effects. The review's most technically ambitious section details how synthetic biology is transforming these natural particles into precision drug carriers.

Researchers engineered Escherichia coli Nissle 1917 to display the bone-homing receptor CXCR4 on vesicle surfaces, directing the particles toward SDF-1-rich bone tissue. A second-generation construct fused both BMP-2, a master regulator of osteoblast differentiation, and CXCR4 to the vesicle surface protein ClyA, producing engineered vesicles termed BEVs-BMP-2-CXCR4 that significantly ameliorated osteoporosis in ovariectomized mice by activating BMP/SMAD signaling. Alternative platforms include thiol-click conjugation of the bone-targeting peptide SDSSD onto vesicles, electroporation-based loading of sclerostin siRNA to activate Wnt/beta-catenin signaling, encapsulation of the osteoclast-inhibiting peptide FRATtide, and biomaterial-assisted delivery through hydrogels for local bone repair.

Yet the authors are notably candid about the translational gap. Human clinical evidence remains mixed and often contradictory. A landmark multicenter trial of a three-strain Lactobacillus formulation in 249 early postmenopausal women delayed lumbar spine trabecular bone loss, but a recent twelve-month trial of the identical formulation in 114 women failed to replicate the benefit and actually showed greater distal tibia bone loss in the probiotic group.

Other trials have yielded encouraging but modest signals: Lactobacillus reuteri reduced tibial bone loss by roughly half in older women with low bone density, and Limosilactobacillus fermentum CCFM1126 improved T-scores and serum calcium and vitamin D in a small three-month study. Most trials suffer from small samples, short durations, and reliance on biochemical markers rather than fracture endpoints, and the review stresses that probiotic efficacy is likely context-dependent, shaped by baseline diet, microbiome composition, and host genetics. Safety questions surrounding engineered vesicles receive particularly pointed attention.

Bacterial vesicles naturally carry pathogen-associated molecular patterns such as lipopolysaccharide and lipoteichoic acid, which can activate Toll-like receptor pathways and, under repeated systemic dosing, risk cytokine storms, endotoxemia-like reactions, and anti-EV antibody responses that accelerate vesicle clearance. The authors flag four frequently overlooked monitoring needs: dynamic post-administration cytokine profiling, anti-EV neutralizing antibody surveillance, assessment of chronic accumulation in the liver, spleen, and lungs, and evaluation of microbiota perturbation. Engineered vesicles, they argue, should not be assumed safe by default, and rigorous immunogenicity profiling, endotoxin quantification, and biodistribution tracking in aged and comorbid animal models must precede any clinical advancement.

Looking forward, the review proposes a closed-loop roadmap that links multi-omics profiling and artificial intelligence-driven prediction to personalized probiotics and engineered vesicle therapies, converging on bone-targeted delivery and long-term dynamic follow-up. The most urgent research priority, the authors contend, is identifying the specific vesicle-associated proteins that simultaneously promote bone formation and inhibit resorption, which would provide both mechanistic insight and a quality-control marker for future therapeutics. For now, the message is one of tempered optimism: nutraceutical approaches including probiotics, prebiotics, and fermented foods may extend the preventive window for at-risk populations, but they complement rather than replace established pharmacotherapy.

Subject of Research: The role of probiotics and gut microbiota-derived extracellular vesicles in preventing and treating osteoporosis via the gut-bone axis

Article Title: Advances in probiotics and gut microbiota-derived extracellular vesicles for the prevention and treatment of osteoporosis

Article References: Hu, M., Li, H., Li, Y., Cao, H., Dai, X., Tan, Y., Yu, Q., Wang, Z., Wu, X., Xu, J., & Pan, X. (2026). Advances in probiotics and gut microbiota-derived extracellular vesicles for the prevention and treatment of osteoporosis. Frontiers in Nutrition, 13, Article 1884520. https://doi.org/10.3389/fnut.2026.1884520

Image Credits: AI Generated

DOI: 10.3389/fnut.2026.1884520

Keywords: osteoporosis, gut microbiota, probiotics, extracellular vesicles, gut-bone axis, bone remodeling, osteoblasts, osteoclasts, short-chain fatty acids, synthetic biology, bone-targeted therapy, clinical trials

The review specifically addressed patients who had undergone surgery for a fragility hip fracture, a group that remains vulnerable to subsequent fractures, persistent pain and incomplete functional recovery even after the fracture has been stabilized. The authors searched PubMed, Embase, Web of Science and the Cochrane Library for studies published from January 2015 through April 15, 2026. Eligible interventions included zoledronic acid, denosumab, teriparatide, alendronate, risedronate, a sequence of pre-fracture alendronate followed by postoperative teriparatide, and control regimens based on calcium, vitamin D, placebo or a combination of these.

Seven randomized controlled trials and 11 non-randomized comparative studies met the criteria. The researchers used Bayesian random-effects consistency models to combine direct and indirect evidence, expressing dichotomous outcomes as odds ratios with 95% credible intervals and continuous outcomes as mean differences with the same interval type. Primary outcomes included subsequent hip fracture, fractures at any site and bone mineral density reported either in grams per square centimetre or as T-scores. Harris Hip Score and visual analog scale pain scores were secondary outcomes. Analyses restricted to randomized trials or to exactly 12 months of follow-up were conducted where the available networks permitted them.

For subsequent hip fracture within 12 months, five studies with 599 patients contributed data. Both zoledronic acid and denosumab showed trends toward lower risk than background therapy, and zoledronic acid also showed a trend toward lower risk than teriparatide. For fractures at any site within 12 months, six studies involving 725 patients produced favorable numerical trends for zoledronic acid, denosumab and alendronate against control, as well as several comparisons between active treatments. At 24 months, however, four studies involving 1,072 patients showed no clear differences among zoledronic acid, denosumab, teriparatide and control.

Those re-fracture findings came with substantial statistical and methodological uncertainty. Fractures were uncommon, several treatment comparisons contained no events, and some estimates were so extreme that they were sensitive to the priors used in the model. The credible intervals were correspondingly wide, and alternative prior specifications altered the magnitude of some results. Node-splitting analysis did not detect inconsistency between direct and indirect evidence for the 24-month network, and leave-one-out analyses produced broadly stable findings. Even so, the authors described the risk-reduction results as trends rather than definitive evidence of superiority.

Bone mineral density was likewise characterized by outcome-specific patterns rather than a stable medication advantage. Four randomized studies contributing 301 patients supplied areal density data in grams per square centimetre, while four studies with 368 patients supplied T-score data. Zoledronic acid and teriparatide had relatively favorable numerical rankings in the areal-density analysis, whereas alendronate and teriparatide ranked more favorably by T-score. Neither network showed clear between-treatment differences. The apparent divergence also reflected differences in baseline density, anatomical site, laterality, measurement devices and follow-up periods, which could not be resolved with reliable site-specific analyses.

No clear differences emerged for hip function or pain. Eight studies with 684 patients contributed Harris Hip Score data, and eight studies with 1,074 patients contributed visual analog scale data. The Harris Hip Score analysis showed very high heterogeneity, while heterogeneity for pain scores was also very high. Alendronate had a favorable numerical pattern for Harris Hip Score, and zoledronic acid and denosumab showed favorable patterns for pain, but no comparisons clearly distinguished the treatments. Randomized-only and exact-12-month sensitivity analyses were generally consistent with the primary models. The authors cautioned that these outcomes capture the combined effects of surgery, rehabilitation, analgesia, fracture characteristics and baseline health rather than the isolated action of an osteoporosis drug.

Risk-of-bias assessments reinforced the need for caution. All 11 non-randomized studies were judged to have a high overall risk of bias, with concerns involving participant selection, intervention classification, departures from intended treatment, outcome measurement and selective reporting. Although the non-randomized studies received moderate-to-good scores on a supplementary methodological-quality scale, the randomized trials also had unclear or high risk in some areas of sequence generation, allocation concealment and blinding. The GRADE assessment indicated limited certainty across the outcomes, while publication bias could not be assessed reliably because the networks were small and comparison-adjusted funnel plots were not used.

Treatment timing was another unresolved influence. The interval between fracture or surgery and the start of medication could affect early skeletal recovery and the time available for bone-density gains, particularly when antiresorptive and anabolic therapies are compared. Reporting was too inconsistent to form comparable groups, and the evidence could not support reliable subgroup or network meta-regression analyses. The synthesis also did not systematically evaluate adverse events, treatment discontinuation, adherence, renal considerations or hypocalcemia. As a result, it cannot establish comparative benefit-risk profiles, and the relatively favorable signals for individual drugs should not be read as prescribing advice or as evidence that one treatment should be selected over another.

The central message is that the available evidence does not support a universal ranking of osteoporosis medications after fragility hip fracture surgery. Favorable early re-fracture signals for zoledronic acid, denosumab and alendronate were outcome- and time-specific, whereas teriparatide’s relative pattern for bone-mass restoration emerged over longer follow-up. None of these signals was accompanied by consistent advantages across fracture, density, function or pain outcomes. More rigorous head-to-head randomized trials, standardized outcome measurement, clearly reported treatment timing and systematic assessment of safety and adherence are needed before comparative claims can become more reliable.

Subject of Research: Comparative effects of anti-osteoporosis medications after surgery for fragility hip fracture

Article Title: Effects of different anti-osteoporosis medications on re-fracture risk, bone mineral density, and functional recovery following hip fragility fracture surgery: a systematic review and network meta-analysis

Article References: Tian, J., Zhang, H., Lu, Y., Wu, H., Lu, Y., Yu, D., Yu, L., & Luo, Z. (2026). Effects of different anti-osteoporosis medications on re-fracture risk, bone mineral density, and functional recovery following hip fragility fracture surgery: a systematic review and network meta-analysis. Frontiers in Endocrinology, 17, Article 1949781. https://doi.org/10.3389/fendo.2026.1949781

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1949781

Keywords: fragility hip fracture, osteoporosis, network meta-analysis, anti-osteoporosis drugs, re-fracture prevention, bone mineral density, hip function, postoperative pain, evidence certainty, Effects, different, anti-osteoporosis

Investigators used dual-energy X-ray absorptiometry, or DEXA, to assess bone mineral density at the lumbar spine, femoral neck and hip. Measurements were taken at baseline, after participants had received estrogen therapy alone for at least one year, and after they had received estrogen plus testosterone for at least one year. The mean duration of estrogen-only therapy was 3.5 years, while the mean duration of combined estrogen and testosterone therapy was 3.1 years.

Across the study, participants were followed for an average of 4.1 years. The analysis compared T-scores at the three skeletal locations across these sequential treatment periods. Estrogen therapy alone did not produce a statistically significant increase in T-scores at the lumbar spine, femoral neck or hip.

In contrast, estrogen plus testosterone was associated with a significant increase in the lumbar spine T-score. The femoral neck and hip T-scores remained stable across both treatment periods, making the spine the only measured site where the researchers reported a significant increase after combined therapy. The release did not provide the numerical T-score changes, DEXA values, confidence intervals or other effect estimates, so the magnitude and precision of the observed association cannot be determined from the information supplied.

Based on the site-specific pattern, Davis and colleagues suggested that testosterone may have a synergistic effect with estrogen on trabecular bone, with the clearest measured association occurring at the spine. This was the investigators’ interpretation of the results rather than a separately demonstrated biological mechanism. The observational design and the sequence of estrogen-only and combined treatment mean that the findings establish an observed association, not a causal effect of adding testosterone.

Information about participant characteristics, adverse events and adherence was not included in the release. Bone density can decrease substantially during and after menopause as estrogen levels fall, and the release notes that women may lose 10% to 20% of their bone density in the first five to seven years after menopause. This rapid thinning raises the risk of osteopenia, described as low bone mass, and osteoporosis, characterized by weak, brittle bones that are prone to fracture.

Estrogen therapy has historically been prescribed to lower the risk of spine and hip fractures, while weight-bearing and resistance exercise, adequate calcium and vitamin D intake and hormone therapy are described as proven methods for protecting bone health. The present findings do not report a fracture outcome, and Davis said further research is needed to determine how testosterone could be used safely and effectively in individualized menopausal care. Stephanie Faubion, medical director of The Menopause Society, similarly emphasized the need for more studies exploring options that may help protect women’s bones during and after menopause.

Subject of Research: Bone mineral density during sequential estrogen and combined estrogen-testosterone therapy in postmenopausal women

Article Title: Combined estrogen and testosterone therapy increases lumbar spine bone mineral density

Article References: Combined estrogen and testosterone therapy increases lumbar spine bone mineral density. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: postmenopausal women, bone mineral density, estrogen therapy, testosterone therapy, lumbar spine, osteoporosis, menopause, DEXA, Combined, estrogen, testosterone, therapy

The review found convergent evidence linking these effects to signaling pathways involving SMAD2/3, BMP2, SIRT1/Nrf2/HO-1, CDK12, RANKL–RANK, NF-κB, MAPK and ERK. Its scope was limited to English-language in vivo and in vitro research available through November 2025; it did not test ellagic acid in people with osteoporosis. The researchers searched PubMed, Scopus, Web of Science and Google Scholar in accordance with PRISMA guidelines.

Eligible investigations assessed the effects of ellagic acid on osteoporosis-related outcomes. Information was extracted about each experimental model, the compound’s dosage and administration, the signaling pathways evaluated and the bone-related results. Thirteen studies met the inclusion criteria.

The evidence came from cell cultures and animal models rather than clinical trials, so the findings describe laboratory activity under experimental conditions rather than established benefits for human bone health. The review’s purpose was to assess the available preclinical evidence and identify molecular pathways associated with ellagic acid’s effects. Ellagic acid enhanced osteoblast differentiation, viability and bone-forming capacity in the included experiments.

It increased osteogenic markers and was associated with activation of SMAD2/3 and BMP2 signaling, as well as the SIRT1/Nrf2/HO-1 pathway. The compound also inhibited CDK12, which the review identified as a negative regulator of osteoblast differentiation. In parallel, ellagic acid reduced osteoclast differentiation and bone resorption.

It disrupted RANKL–RANK interactions and inhibited downstream NF-κB, MAPK and ERK signaling. Together, these results indicate that the compound affected both bone formation and bone breakdown in the reviewed experimental systems. They do not establish that the same balance of effects will occur in patients.

Animal experiments extended these cellular findings to structural and mechanical outcomes. In ovariectomy-induced and microgravity-induced osteoporosis models, ellagic acid administration improved bone mineral density, preserved trabecular microarchitecture and increased mechanical strength. The treated animals also showed attenuation of oxidative stress and inflammatory responses within the bone microenvironment.

These observations are consistent with the review’s interpretation that ellagic acid may protect bone through coordinated effects on formation, resorption and the cellular environment. However, the evidence base consists of controlled preclinical studies rather than human trials. The authors also identified bioavailability as an important challenge for translating the results.

They concluded that large-scale, long-term clinical studies are required to confirm efficacy, determine appropriate dosing strategies and address bioavailability before ellagic acid can be considered an established osteoporosis treatment.

Subject of Research: Preclinical evidence on ellagic acid effects in osteoporosis cell and animal models

Article Title: Ellagic acid and bone health: a systematic review of preclinical studies on its protective role against osteoporosis

Article References: Gholizadeh, M., Sarajar, B. O., Asadi, J., & Soleimani, A. A. (2026). Ellagic acid and bone health: a systematic review of preclinical studies on its protective role against osteoporosis. Molecular Biology Reports, 53(1), Article 1531. https://doi.org/10.1007/s11033-026-12648-3

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12648-3

Keywords: ellagic acid, osteoporosis, systematic review, preclinical studies, bone formation, bone resorption, osteoblasts, osteoclasts, animal models, clinical evidence, Ellagic, acid

The researchers found that excess glucose, alcohol or acetate activated a mitochondrial reactive oxygen species signaling pathway, which engaged the integrated stress response and the transcription factor CEBPB. This signaling increased ACSS1, a protein involved in converting acetate into acetyl-CoA. Once accumulated, ACSS1 raised acetyl-CoA production from supplied acetate or from acetate generated internally from glucose or ethanol.

The metabolic rewiring promoted excessive protein acetylation and specifically inactivated malate enzyme 2 (ME2) through acetylation at lysine 94. ME2 inactivation disturbed the malate-aspartate shuttle and, according to the study, created a self-perpetuating cycle of redox imbalance and oxidative stress. That cycle intensified mitochondrial dysfunction and impaired the osteogenic capacity of the affected cells.

The mechanism therefore connected several elements of the stress response: acetate metabolism, acetyl-CoA abundance, protein acetylation, mitochondrial communication and the differentiation of cells that form bone. ACSS1 was identified as a key stress responder that mediated this mitonuclear communication in bone marrow skeletal stem cells. Genetic deletion of Acss1 in male mouse models of type 2 diabetes and chronic alcohol consumption restored mitochondrial resilience, osteogenic capacity and bone formation.

The researchers also used an adeno-associated virus to deliver a non-acetylatable ME2 mutant to osteoprogenitor cells; this approach produced protective effects in the models tested. Deletion of Acss1 protected against osteoporosis or osteonecrosis, while delivery of the ME2 mutant similarly counteracted the bone-forming defects associated with the experimental metabolic stresses. Because the reported experiments were conducted in mice and bone-forming cells, the results establish a mechanism in those systems rather than a clinical benefit in people.

The central finding is that nutrient stress can drive ACSS1-dependent metabolic rewiring, mitochondrial damage and impaired bone formation through a pathway involving ME2 acetylation.

Subject of Research: ACSS1-mediated metabolic stress and impaired bone formation in mouse models

Article Title: Nutrient stress-driven ACSS1 controls metabolic flexibility and bone formation

Article References: Gao, L., Yuan, Z., Huang, T., Li, P., Zhong, Y., Gao, J., Luo, Y., Li, B., Pan, H., Ye, K., & Guan, M. (2026). Nutrient stress-driven ACSS1 controls metabolic flexibility and bone formation. Nature Communications. https://doi.org/10.1038/s41467-026-77684-w

Image Credits: AI Generated

DOI: 10.1038/s41467-026-77684-w

Keywords: ACSS1, nutrient stress, bone formation, bone marrow stem cells, mitochondrial dysfunction, osteogenesis, protein acetylation, ME2, type 2 diabetes, osteoporosis, Nutrient, stress-driven

Skeletal complications can arise from both malignant disease and its treatment. The study describes cancer treatment–induced bone loss as a multifactorial process involving systemic inflammation, reduced physical activity, nutritional deficiencies and exposure to treatments such as chemotherapy, radiotherapy, endocrine therapy, glucocorticoids and hematopoietic stem-cell transplantation. These factors can act together to increase bone turnover, reduce bone mineral density and elevate fracture risk. Bone loss associated with cancer therapies is particularly well established in hormone-sensitive malignancies, including breast and prostate cancer, where aromatase inhibitors and androgen-deprivation therapy are linked to accelerated bone loss. However, population-based evidence described by the researchers indicates that fracture risk is elevated across a broader range of cancers and can persist for years after diagnosis.

Despite that wider risk, guidelines from major oncology and endocrine organizations recommend DXA for people at increased skeletal risk, especially those exposed to bone-toxic therapies. The researchers also note that osteoporosis risk-assessment tools can underestimate fracture risk in cancer survivors and that malignancy is not consistently incorporated into fracture-prediction models. Their retrospective cohort used the MDClone platform to extract fully anonymized, statistically accurate data from electronic medical records at Assuta, a private healthcare network operated by Maccabi Healthcare Services. Eligible participants were adults with a first documented cancer diagnosis and complete demographic information. Mean age was 60.2 years, 77.0% were women, and mean body-mass index was 26.7 kg/m². Chemotherapy exposure was recorded in 21.4% of patients and radiotherapy in 7.0%.

Assessment patterns differed sharply according to sex and cancer type. Women were more likely than men to undergo DXA, with utilization rates of 41.7% and 15.0%, respectively. Breast cancer had the highest rate of testing at 42.2%, followed by prostate cancer at 30.0%, while rates were generally below 15% for lung, gastrointestinal, ovarian and pancreatic cancers. In a multivariable logistic regression, female sex was associated with greater odds of DXA assessment than male sex, with an adjusted odds ratio of 2.13 and a 95% confidence interval of 1.79–2.50. Each additional year of age was associated with slightly higher odds, while breast and prostate cancer were associated with adjusted odds ratios of 5.82 and 5.29, respectively, compared with other cancer types. These associations describe testing patterns rather than proving why individual scans were ordered or omitted.

Timing was similarly uneven. Only 14.1% of the full cohort underwent DXA during the first 12 months after diagnosis. Among all patients who eventually received a scan, the median time to assessment was 14.8 months. Median timing was 12.9 months for breast cancer, with an interquartile range of 5.8–28.0 months, and 12.7 months for prostate cancer, with an interquartile range of 4.4–28.8 months. Patients with other malignancies waited longer: their median time to DXA was 17.9 months, with an interquartile range of 8.3–35.1 months. Men and women who were assessed had broadly comparable timing, indicating that the largest sex difference concerned whether a scan occurred at all rather than the interval among those who received one.

Bone density was frequently abnormal when the scans finally occurred. The analysis of bone-density outcomes included 5,570 tested patients with complete, evaluable measurements. Using the lowest T-score from the lumbar spine, femoral neck or total hip, 40.2% had normal bone mineral density, 45.2% met the criteria for osteopenia and 14.5% met the criteria for osteoporosis. The mean lowest T-score was −1.72 among patients classified as osteopenic and −2.95 among those classified as osteoporotic. Site-specific results showed the least favorable average T-score at the femoral neck, at −1.14, compared with −0.83 at the total hip and −0.54 at the lumbar spine. Osteopenia was most frequent at the femoral neck, affecting 50.3% of patients with available site-level measurements, while osteoporosis was most common at the lumbar spine at 10.2%.

These measurements show a large burden of low bone mass among people who reached DXA, but they do not establish when the bone loss began or what caused it. Abnormal density may have predated the cancer diagnosis, and the retrospective data could not uniformly capture histology, disease stage, treatment dose or duration, lifestyle factors and other influences on skeletal health. The investigators could not systematically identify hematopoietic stem-cell transplantation, and DXA examinations performed outside Assuta may not have been captured. Fracture outcomes were not analyzed, so the study could not determine whether delayed testing was associated with more fractures. DXA completion was also used as a surrogate for bone-health evaluation, even though some patients without a recorded scan may have met osteoporosis criteria through other clinical information. These restrictions prevent the findings from establishing a causal effect of the testing gap on skeletal outcomes.

The analysis nevertheless points to missed opportunities for earlier skeletal risk identification. The researchers proposed several potential ways to make assessment more systematic, but did not test the effectiveness of these approaches. Electronic oncology records could issue automated DXA-referral prompts when a cancer is diagnosed or when a patient starts treatment likely to affect bone. Bone-health evaluation could be integrated into standardized survivorship-care plans and multidisciplinary tumor reviews, including for cancers less consistently covered by endocrine-therapy guidance. Dedicated referral pathways were also proposed for patients receiving chemotherapy, radiotherapy or glucocorticoids. Because the study documented substantially lower use among men, the authors suggested targeted education and closer collaboration among oncology, endocrinology and specialist bone-health services, while acknowledging the need to determine whether such measures improve assessment and outcomes.

Uncertainty remains particularly relevant for newer systemic therapies, including immune checkpoint inhibitors and targeted agents. The study notes that their long-term effects on bone mineral density and fracture outcomes remain incompletely characterized. A cited meta-analysis of randomized trials involving more than 19,000 patients associated immune checkpoint inhibitor use with a nonsignificant 18% increase in clinical fracture incidence relative to controls, with an odds ratio of 1.18 and a 95% confidence interval of 0.82–1.70. Because fractures were infrequently reported and the confidence interval included no effect, the estimate was imprecise and does not establish a fracture-causing effect. The present study also had broader generalizability limitations: it included one healthcare network in a specific national insurance system, did not consistently capture ethnicity, and may have enrolled a less complex case mix than the wider Israeli cancer population. Within those boundaries, the results show that DXA after cancer diagnosis was selectively delivered and frequently late, with abnormal bone density already common when assessment occurred.

Subject of Research: Real-world DXA utilization, timing and bone-mineral-density outcomes after cancer diagnosis

Article Title: Delayed and selective bone health assessment following cancer diagnosis: a real-world gap in survivorship care

Article References: Rouach, V., Versano, Z., Sasson, M., Greenman, Y., & Makori, A. (2026). Delayed and selective bone health assessment following cancer diagnosis: a real-world gap in survivorship care. Supportive Care in Cancer, 34(11), Article 1124. https://doi.org/10.1007/s00520-026-11340-3

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11340-3

Keywords: cancer survivorship, bone density, DXA, osteoporosis, osteopenia, fracture risk, screening disparities, real-world cohort, cancer treatment, Delayed, selective, bone

The strategy addresses several features of osteoporotic bone loss at once. Osteoporosis involves an imbalance in remodeling, in which bone resorption by osteoclasts can exceed new bone formation by osteoblasts. The condition is also associated with chronic low-grade inflammation and oxidative stress, while macrophages and other immune cells help determine the local inflammatory environment. The researchers therefore designed a delivery system intended to carry a gene-regulating cargo to relevant bone cells, reduce reactive oxygen species, and dampen inflammatory signaling. This was an experimental nanomedicine approach tested in cultured cells and a mouse model, not a clinical treatment.

For the gene-regulating component, the investigators used a miR-196b inhibitor. Previous evidence cited in the paper showed that miR-196b-5p can inhibit osteoblast differentiation and influence both osteogenic and osteoclastic processes, including signaling associated with Sema3a, Wnt/β-catenin and the RANKL/OPG system. In the engineered particles, the inhibitor increased expression of GATA6, a downstream target used to verify miR-196 inhibition. M2 macrophage-derived exosomes were selected as the carrier because they provide an extracellular-vesicle delivery platform with reported immunomodulatory and osteogenic properties. Platinum nanoparticles were added for their enzyme-like antioxidant activity. The system was thus designed to combine RNA regulation, reactive oxygen species scavenging and alteration of the local osteoimmune environment in a single carrier.

The researchers characterized the engineered vesicles using transmission electron microscopy, nanoparticle tracking analysis, Western blotting and cell-viability assays. The M2-derived exosomes had a typical cup-shaped structure and an average diameter of 118.0 ± 43.9 nm, while the targeted, co-loaded formulation measured 139.2 ± 48.8 nm. Electron microscopy indicated that loading and targeting modifications did not visibly disrupt the vesicular membrane or cause obvious aggregation. HSP90, TSG101 and CD9 were detected as exosomal markers. No significant cytotoxicity was observed after 24 or 72 hours in the tested cell systems. Platinum-containing formulations showed stronger scavenging activity for hydrogen peroxide, hydroxyl radicals and superoxide than unmodified exosomes or blank controls, supporting the intended redox-buffering function of the nanoparticles.

Targeting was tested both in cultured cells and in mice. The SDSSD peptide was selected because it binds periostin, a ligand associated with osteoblast targeting. Confocal microscopy showed that BT-modified exosomes were taken up preferentially by MC3T3-E1 osteoblast-lineage cells compared with RAW264.7 macrophages. After intravenous administration of fluorescently labeled particles, BT-Exos accumulated more strongly in femur sections than unmodified exosomes. Ex vivo imaging of the brain, heart, liver, spleen, lungs, kidneys, tibiae and femora likewise showed stronger skeletal fluorescence and reduced distribution in other organs for the targeted formulation. The authors interpret these findings as evidence of preferential bone accumulation, although the experiments did not establish the complete fate of the particles or the precise cellular route of uptake. The delivery advantage was therefore demonstrated under the study’s experimental conditions rather than as a general property of all exosome formulations.

In inflammatory cell assays, the components produced complementary effects. Platinum-containing formulations showed the greatest intracellular ROS-scavenging performance, while M2-derived exosomes reduced the expression of the pro-inflammatory cytokines interleukin-1β, interleukin-6 and tumor necrosis factor-alpha. Combining the exosome, platinum and miR-196 inhibitor produced the strongest overall reductions in cytokine expression, with quantitative reverse-transcription PCR agreeing with the fluorescence measurements. Comparisons of exosomes from M0, M1 and M2 macrophages also showed that M1 and M2 exosomes increased alkaline phosphatase activity and mineralization relative to controls, but only M2 exosomes significantly increased RUNX2 expression, the osteogenic transcription factor used by the researchers to justify the choice of carrier. These results support the rationale for using M2-derived vesicles, while not establishing that the formulation will produce the same effects in human bone tissue.

The targeted particles promoted osteoblast development in vitro. After seven days of osteogenic induction, the fully engineered formulation produced the strongest alkaline phosphatase staining; after 14 days, treated cultures showed greater calcium deposition by Alizarin Red S staining than controls. Western blotting showed progressively higher RUNX2 and ALP protein levels across the treatment groups, with BT-Exo-Pt-miR-196 inhibitor highest among them. Immunofluorescence measurements of osterix and osteocalcin followed the same pattern. Quantitative proteomics of MC3T3-E1 cells treated with BT-Exo-miR-196 inhibitor identified 605 up-regulated and 531 down-regulated proteins relative to control, with six biological replicates per group. Increased proteins included SP7, LRP5 and RUNX2, together with matrix-related proteins POSTN, BGN and LOX, while innate immune and cytokine-associated proteins including TBK1, P2RX7, C3, CGAS, TLR2, PTGS2 and ISG15 decreased. Pathway enrichment indicated changes involving mitochondrial and respiratory-chain proteins, extracellular matrix processes and immune signaling. These measurements are cellular and biochemical observations, not evidence of fracture healing in people.

Osteoclast formation was also reduced in laboratory cultures. Bone-marrow-derived macrophages exposed to osteoclast-inducing conditions developed fewer TRAP-positive multinucleated cells after treatment with the engineered formulations, and the untargeted co-loaded exosome produced the lowest osteoclastogenesis in that assay. Phalloidin staining showed weaker F-actin ring formation, while Western blot and gene-expression measurements showed lower levels of osteoclast-associated markers, including NFATc1, cathepsin K, MMP9 and TRAP. The untargeted result was not considered a contradiction: the SDSSD peptide binds periostin on osteoblasts and was not designed to bind osteoclast precursors. Its benefit in the animal model was therefore interpreted as preferential delivery to bone surfaces and remodeling regions rather than direct targeting of osteoclasts. In other words, the targeting strategy appeared useful for concentrating the therapy in the bone microenvironment, but the osteoclast cultures did not provide evidence that the peptide directly targets osteoclasts.

In the in vivo experiment, eight-week-old female C57BL/6 mice were assigned to sham-operated, ovariectomized, untargeted-treatment and targeted-treatment groups, with five animals per group. Treatments began two weeks after surgery and involved tail-vein injections every three days for six weeks. Each treatment dose contained 100 μL of PBS with 1.0 × 10^11 particles/mL, and the ovariectomy-only group received PBS on the same schedule. Micro-CT of the distal femur showed that ovariectomy reduced bone mineral density and trabecular bone volume fraction, increased trabecular separation and reduced trabecular thickness and number. Both nanoparticle treatments partially reversed these changes, but the targeted formulation produced the most pronounced preservation of trabecular architecture. H&E and Masson trichrome staining supported the imaging results by showing improved trabecular organization and matrix deposition. TRAP staining showed the least osteoclast-positive area after targeted treatment, while osteocalcin and osterix measurements indicated stronger osteogenic activity and cathepsin K staining indicated reduced osteoclast-associated activity. The experiment therefore showed improved preservation of bone structure and remodeling markers in this model, rather than complete restoration of a healthy skeleton or prevention of fractures.

The study also reported an initial biosafety signal. White blood cell, red blood cell and platelet counts did not differ significantly among the groups. Serum ALT, AST, blood urea nitrogen and creatinine remained within the reported ranges, and histological examination of the heart, liver, spleen, lungs and kidneys showed no obvious inflammatory infiltration, necrosis or structural damage. These findings support short-term tolerability in this mouse model, but they are not a comprehensive translational safety assessment. The exosomes are cell-derived biological products with possible batch variability, immunogenicity and manufacturing challenges, while the platinum nanoparticles are not enzymatically degraded and may persist in internal organs. Longer observation, dose-escalation studies, quantitative clearance analysis and tests for anti-exosome immune responses remain necessary. Overall, the findings identify an experimental strategy for coordinating bone formation, osteoclast suppression, oxidative-stress control and inflammatory modulation, but its efficacy and safety in humans remain untested.

Subject of Research: Experimental bone-targeted exosome delivery for ovariectomy-induced osteoporosis in mice

Article Title: Engineering exosomes-mediated RNA delivery regulates bone homeostasis and alleviates osteoporosis

Article References: Du, Y., Zhang, Y., Wang, Z., Jiang, H., Li, L., Liu, X., Zhou, P., Huang, X., Liu, J., Li, Z., & Li, Z. (2026). Engineering exosomes-mediated RNA delivery regulates bone homeostasis and alleviates osteoporosis. Materials Today Bio, 41, Article 103758. https://doi.org/10.1016/j.mtbio.2026.103758

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103758

Keywords: osteoporosis, exosomes, miR-196b inhibition, bone targeting, platinum nanoparticles, osteogenesis, osteoclastogenesis, oxidative stress, nanomedicine, mouse model, Engineering, exosomes-mediated

Extracellular vesicles are small, membrane-delimited particles released by virtually all cell types. Unlike soluble signaling molecules such as myokines, which have traditionally dominated models of muscle-to-organ communication, EVs carry complex cargo: proteins, lipids, nucleic acids, and metabolites that reflect the physiological state of the cell that produced them. When a muscle cell releases an EV, it is effectively exporting a molecular snapshot of its own condition. Recipient cells can take up these vesicles and alter their behavior in response, making EVs a sophisticated channel for interorgan dialogue rather than a one-way broadcast of isolated chemical messengers.

The review describes experimental evidence that muscle EVs enter the circulation. Using a myofiber-specific fluorescent reporter mouse, researchers demonstrated that vesicles released by skeletal muscle fibers reach the blood. Complementary work linked mechanical loading of muscle to the delivery of EV-associated microRNA-1 to white adipose tissue, where it promoted lipolysis. Within muscle itself, satellite cells, the resident stem cells responsible for repair, release vesicles that carry microRNA-206 to fibrogenic neighbors, restraining excessive scar tissue formation during muscle growth. These local interactions established the groundwork for asking whether muscle EVs could also act at a distance.

The clearest proof of concept for long-range EV signaling comes from the muscle-bone axis. In cell culture, vesicles from muscle cells were shown to promote osteogenic differentiation of bone precursor cells by delivering microRNA-27a-3p, which activates beta-catenin signaling. More strikingly, in vivo studies identified skeletal muscle-derived EVs that enter the circulation, home to bone, and are taken up by bone marrow stromal cells, where they deliver glycolytic enzymes such as lactate dehydrogenase A to boost energy metabolism and protect mice from disuse osteoporosis. Crucially, this communication channel is state-dependent: vesicles from atrophic muscle do the opposite, suppressing bone-forming activity in osteoblasts. Muscle-targeted blockade of EV generation in atrophic animals restored osteoblast function and alleviated bone loss, demonstrating that the same route can carry either supportive or destructive messages depending on the condition of the sending muscle.

The muscle-brain axis is younger but advancing quickly. In defined culture systems, vesicles from muscle cells enhanced survival and neurite outgrowth of motor neuron-like cells. An engineered neuromuscular tissue model showed that innervation and glutamate stimulation increase EV release from muscle and alter exosomal microRNA cargo, and that the resulting vesicles boost neuronal network activity, dendritic branching, and axonal transport in hippocampal cultures. In a separate injury model, preconditioning exercise increased exosomal microRNA-484, derived mainly from skeletal muscle, which reduced neuronal ferroptosis after ischemic brain injury by suppressing the ACSL4 pathway. Muscle-derived exosomes were tracked to the ischemic penumbra and taken up by neurons, and blocking muscle production of the microRNA weakened the neuroprotective effect of exercise. In an Alzheimer’s disease mouse model, exercise-induced muscle EVs were taken up by microglia, promoting a disease-associated state that enhanced amyloid-beta plaque clearance through microRNA-378a-3p-mediated regulation of lipid metabolism.

Tumor cells appear to be listening as well. In vitro, vesicles from differentiated muscle cells were taken up by lung carcinoma cells and reduced their viability, proliferation, and migration while increasing markers of apoptosis, with proteomic analysis identifying decorin as an enriched cargo candidate. More directly, recent work in Drosophila and mouse cancer models showed that healthy skeletal muscle releases vesicles with tumor-suppressive activity, partly mediated by microRNA-7a-5p inhibition of TEAD1 signaling in tumor cells. Muscle cell-derived vesicles have also been shown to dampen inflammatory gene expression in cultured macrophages by increasing IRG1 expression and itaconate production, hinting at an immunoregulatory dimension to the system, though whether this occurs in distal tissues during aging remains untested.

Aging, the review argues, remodels this entire communication network at three levels: vesicle production, cargo composition, and downstream effects on recipient cells. In human primary muscle cells, vesicles from older donors showed altered proteomic and biochemical signatures, including enrichment of proteins tied to oxidative stress and DNA and RNA mutagenesis, even when basic vesicle parameters looked normal. In the bone axis, age-related shifts are well documented: a muscle-associated circulating vesicle population carries increased microRNA-34a with age, promoting senescence in bone marrow stromal cells, while vesicles from aged or atrophic muscle deliver microRNA-125a-5p, which suppresses the Sirt7-Sp7 osteogenic axis in osteoblasts. In the tumor axis, sarcopenic muscle secretes fewer vesicles with altered cargo, losing the protective microRNA-7a-5p signal, a decline traced to an age-sensitive NOTCH-SDC2 pathway that governs muscle EV biogenesis.

Exercise emerges as the most promising physiological countermeasure. In the Alzheimer’s model, swimming-induced muscle vesicles enhanced microglial plaque clearance and improved cognition, and vesicles engineered to overexpress microRNA-378a reproduced the cognitive benefit when administered directly, a proof of principle that protective exercise signals can be mimicked. Resistance training in older adults increased several circulating EV-associated microRNAs toward youthful levels, while in aged mice exercise restored NOTCH-SDC2 signaling, boosted vesicle release and microRNA-7a-5p cargo, and reduced tumor growth. Metabolic state matters too: overexpression of PGC-1alpha in human myotubes enriched vesicles with antioxidant-related messenger RNAs that enhanced protective responses in cultured endothelial cells, suggesting that donor-cell metabolism shapes cargo and function. Additional mechanistic leads include EV-associated mitochondrial DNA engaging cGAS-STING signaling in recipient cells, and stress-driven unfolded protein response pathways in muscle altering vesicle cargo, both flagged as priorities for future investigation.

The therapeutic implications cut in two directions. Protective vesicular signals that decline with age could be restored or mimicked, as the microRNA-378a experiment demonstrates. Maladaptive signals from aged muscle could be selectively blocked, as shown by cargo-directed interventions that preserved bone formation. But the authors caution that broad suppression of EV production is risky, since the same vesicles can carry beneficial cargo for bone, brain, and tumor defense. Rigorous methodology is also essential: different isolation techniques recover different mixtures of vesicles and non-vesicular material, and confirming that vesicles truly originate from muscle, reach the proposed recipient cells, and account for observed effects remains the central challenge. As the field matures, skeletal muscle-derived extracellular vesicles may prove to be not just biomarkers of aging, but rational intervention targets for the multi-organ decline that accompanies it.

Subject of Research: Skeletal muscle-derived extracellular vesicles as mediators of interorgan communication during aging

Article Title: Skeletal Muscle‐Derived Extracellular Vesicles in Interorgan Communication During Aging

Article References: Jiang, W., Chua, K., Young, J., Tan, E. K., & Tang, H.-W. (2026). Skeletal Muscle‐Derived Extracellular Vesicles in Interorgan Communication During Aging. Aging Cell, 25(10), Article e70773. https://doi.org/10.1111/acel.70773

Image Credits: AI Generated

DOI: 10.1111/acel.70773

Keywords: extracellular vesicles, skeletal muscle, aging, sarcopenia, muscle-bone crosstalk, muscle-brain axis, tumor suppression, microRNA, exercise, osteoporosis, Alzheimer's disease, exosomes

Acute lymphoblastic leukemia, or ALL, accounts for about 28 percent of cancers in children under fourteen and 13 percent in adolescents aged fifteen to nineteen, with an incidence of 58.7 cases per million children per year. Thanks to modern chemotherapy protocols and targeted treatments, survival rates now approach 90 percent. That success has shifted clinical attention toward the early and late adverse effects of therapy, and bone disorders rank among the most consequential. Fractures occur in 16 to 36 percent of patients around ALL onset or during treatment, mostly within the first two years and peaking in the spine at roughly twelve months. Long-term survivors face reduced bone mineral density and a six-fold increased risk of fragility fractures compared with healthy peers, with culprits including glucocorticoids, methotrexate, reduced weight-bearing activity, malnutrition, and endocrine disturbances.

The Italian team enrolled 49 patients aged three to eighteen who were treated under the AIEOP-BFM ALL 2009 protocol between March 2012 and April 2016. Participants underwent dual-energy X-ray absorptiometry, or DXA, scans and extensive blood and urine testing at seven timepoints: at diagnosis, every six months thereafter, and until one year after the end of the 24-month treatment program. The researchers measured both lumbar spine bone mineral apparent density, a volume-corrected metric for the vertebrae, and total body less than head bone mineral density, chosen because the growing skull contributes unpredictably to total-body readings in children. All scans were performed on a single densitometer and reviewed by one expert to eliminate inter-observer variability, and body composition indexes were expressed as standard deviation scores against age- and sex-specific pediatric reference ranges.

The baseline results were striking. At diagnosis, before any chemotherapy had begun, 71.7 percent of patients had lumbar spine Z-scores at or below -2.0, with a median of -2.8, indicating severely reduced vertebral bone density. Yet total body bone density was essentially normal, exceeding -2.0 in 97.8 percent of patients. The researchers attribute this dissociation to the biology of the disease itself: leukemic blasts infiltrate trabecular bone, the spongy, metabolically active tissue that predominates in the lumbar vertebrae and serves as a site of hematopoiesis, while cortical bone throughout the rest of the skeleton remains largely spared. Tumor-released cytokines may further erode trabecular integrity. Because the study’s strict enrollment criteria excluded children with prior steroid exposure, immobilization, or conditions affecting bone health, the authors argue that the malignant cells themselves are the most plausible explanation for the spinal damage present at day one.

The picture reversed once treatment began. Total body bone density plummeted within the first six months, reaching its nadir twelve to eighteen months after diagnosis, a timing that coincides with the most intensive phase of chemotherapy, when patients receive high-dose corticosteroids known to trigger apoptosis in both osteoblasts and osteoclasts, along with methotrexate and prolonged hospitalization that drastically reduces weight-bearing activity. Linear mixed-effects models confirmed the pattern statistically: at twelve months, total body Z-scores were on average 1.66 standard deviations below baseline, the largest drop recorded. In contrast, lumbar spine density stayed flat during treatment, suggesting that therapy added little further harm to bone already devastated by the leukemia. Recovery began after the twenty-fourth month, but it was incomplete on both fronts.

Biochemical markers told a parallel story of bone in turmoil. Vitamin D levels below 20 nanograms per milliliter were found in 40.8 percent of patients at diagnosis, and 18.4 percent showed elevated parathyroid hormone. During the first six months of therapy, both bone formation markers, including bone-specific alkaline phosphatase and osteocalcin, and the resorption marker beta-CTX rose significantly, signaling heightened bone turnover accompanied by increased serum and urinary calcium and compensatory parathyroid activation. The researchers also tracked the RANKL-to-OPG ratio, a molecular dial that governs osteoclast activity, and observed it fall between months twelve and eighteen, which they attribute to the withdrawal of steroids and the start of methotrexate-based maintenance therapy, which suppresses RANKL secretion. Notably, alkaline phosphatase correlated negatively with spine density as late as one year after treatment ended.

Body composition shifted in a worrying direction simultaneously. Lean mass percentage declined steadily from the first six months onward, dropping from a median of 74.7 percent at diagnosis to 68.7 percent at the three-year mark, while fat mass rose progressively, a pattern consistent with the sarcopenic obesity reported in long-term ALL survivors, which one prior study found in 43 percent of patients a decade or more after diagnosis. The most clinically meaningful result emerged from multivariable analysis: improvements in the appendicular skeletal muscle mass index over time were significantly associated with recovery of total body bone density between months six and thirty-six (p = 0.008), while fat mass changes showed no such link. Age also mattered, with younger children showing worse spine density at diagnosis but milder, more recoverable losses in total body bone, possibly reflecting a greater bone turnover reserve.

The study’s authors suggest a practical implication: protecting and rebuilding lean muscle mass through timely, weight-bearing physical activity may help shield young survivors from cortical bone loss, though they caution that dedicated interventional studies are needed to confirm the causal pathway. Mechanistically, the connection is plausible, because muscle contraction loads the skeleton and lean mass is one of the strongest determinants of bone accrual during growth. The researchers also note limitations, including the modest sample size, the absence of systematic spinal imaging to detect asymptomatic vertebral compression fractures, unavoidable missed scans among the sickest patients, and the wide age range, which makes pubertal development difficult to disentangle.

Nevertheless, the prospective design, more than 250 DXA scans, and rigorous standardization lend unusual weight to the findings. No symptomatic fractures occurred during the three-year observation window, but when 43 surviving patients were contacted roughly 11.6 years after diagnosis, seven reported at least one fracture afterward, several involving the forearm, a classic site of fragility injury. With survival from childhood ALL now the norm rather than the exception, the study argues that bone health deserves a permanent place in survivorship care. Monitoring both spine and total body density, supporting muscle mass through nutrition and exercise, and correcting vitamin D deficiency may together determine whether today’s cured children face tomorrow’s fractures as adults.

Subject of Research: Longitudinal changes in bone mineral density, bone turnover, and body composition in children treated for acute lymphoblastic leukemia

Article Title: Longitudinal changes in bone mineral density, bone turnover markers, and body composition in children and adolescents treated for acute lymphoblastic leukemia

Article References: Cattoni, A., Molinari, S., Capitoli, G., Vai, S., Carrara, S., Galliera, E., Massaccesi, L., Nicolosi, M. L., Radaelli, S., Sarra, M., Tondelli, D., Corso, R., Speziali, G., Biondi, A., Balduzzi, A., Corbetta, S., & Sala, A. (2026). Longitudinal changes in bone mineral density, bone turnover markers, and body composition in children and adolescents treated for acute lymphoblastic leukemia. Frontiers in Endocrinology, 17, Article 1901073. https://doi.org/10.3389/fendo.2026.1901073

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1901073

Keywords: acute lymphoblastic leukemia, bone mineral density, pediatric oncology, DXA, body composition, lean mass, bone turnover markers, osteoporosis, glucocorticoids, childhood cancer survivors, sarcopenic obesity, parathyroid hormone