Hair follicles are among the most dynamic mini-organs in the mammalian body. Each follicle cycles repeatedly through phases of vigorous growth, destruction, and rest, and each new cycle depends on stem cells resident in a region of the follicle called the bulge exiting their quiescent state at precisely the right moment. Once activated, these cells must proliferate, migrate downward, and differentiate into the multiple lineages that construct the follicle and its associated structures. This process demands an extraordinary degree of coordination, and it has long been clear that transcription factors, proteins that switch specific genes on or off, are central to establishing the identity of each cell type. What has remained murky is how cells ensure that the right proteins are actually synthesized in the right amounts once their messenger RNAs have been made, a question of post-transcriptional control that the new study addresses directly.

The answer lies in a chemical modification known as N7-methylguanosine, abbreviated m7G, in which a methyl group is attached to the nitrogen at position seven of a guanosine base. This modification has attracted growing attention in recent years as one of several RNA marks, alongside the better-known m6A modification, that influence the fate and function of RNA molecules inside cells. METTL1, working together with its partner protein WDR4, is the key methyltransferase responsible for installing m7G marks. The modification is best characterized on transfer RNAs, the adaptor molecules of protein synthesis, where it stabilizes the tRNA structure and supports efficient translation. But m7G can also be deposited internally within messenger RNAs, and it is this internal messenger RNA methylation that turned out to be central to the hair follicle story.

To probe the role of METTL1 in hair biology, the researchers created mice in which the Mettl1 gene could be deleted specifically in keratinocytes. The consequences were dramatic. Animals lacking the enzyme in these cells displayed severe dysplasia of hair follicle development, meaning the follicles formed abnormally and failed to achieve their normal architecture. Regeneration was also impaired, with the follicles unable to cycle properly through subsequent rounds of growth. In addition, the team observed disruptions in keratinocyte adhesion, the process by which these cells stick to one another to maintain the structural integrity of the epidermis and follicle. These defects point to METTL1 as a gene whose loss undermines both the construction of the follicle and its ongoing maintenance across cycles.

The complementary experiment strengthened the conclusion. When the researchers introduced a keratinocyte-specific knock-in that increased Mettl1 activity, hair regeneration accelerated. This gain-of-function result demonstrates that the enzyme is not merely permissive for hair growth but is genuinely rate-limiting: more METTL1 means faster regrowth, at least under the conditions of the experiment. Together, the loss-of-function and gain-of-function data establish a bidirectional relationship between METTL1 levels and the tempo of the hair follicle cycle, a relationship that suggests the enzyme could in principle be targeted to modulate hair growth in pathological settings, although the authors are careful to frame the work as mechanistic biology rather than as a therapeutic demonstration.

Mechanistically, the study traced the effects of METTL1 loss to a specific transcription factor with a well-established role in hair biology: HOXC13. This homeobox protein is known to govern the expression of genes required for hair shaft formation and follicle differentiation. The researchers found that when METTL1 is absent, HOXC13 messenger RNA becomes destabilized and its levels fall. The destabilization is attributed to the loss of internal m7G modification on the HOXC13 transcript itself, implying that the methyl mark normally protects or otherwise supports the messenger RNA, allowing it to persist long enough to be translated into protein. Without the mark, the transcript decays, HOXC13 protein levels drop, and the genetic program that depends on HOXC13 falters.

Downstream of HOXC13, the study mapped a signaling axis that connects the RNA modification to the observable defects in the follicle. HOXC13 normally promotes the expression of FOXN1, a transcription factor famous for its role in hair and immune development, and FOXN1 in turn supports the expression of DSG4, a desmoglein, which is a calcium-dependent adhesion molecule of the cadherin family concentrated in the hair shaft and inner root sheath. DSG4 provides the intercellular adhesion that keeps differentiating keratinocytes properly glued together as they build the hair shaft. When METTL1 is lost, HOXC13 messenger RNA decays, FOXN1 declines, and DSG4 falls with it, explaining both the differentiation defects and the adhesion disruptions seen in the knockout animals. The chain from RNA mark to mRNA stability to transcription factor to adhesion molecule constitutes a complete mechanistic pathway linking a chemical modification to tissue architecture.

The conceptual significance of the work extends beyond hair. Biologists have long distinguished between transcriptional regulation, which determines which genes are read into RNA, and post-transcriptional regulation, which determines what happens to those RNA molecules afterward. The new findings show that an RNA modification enzyme can sit upstream of a transcription factor, effectively using post-transcriptional control to tune a transcriptional circuit. In this arrangement, METTL1 does not directly change which genes are transcribed; instead, it safeguards the messenger RNA of a master regulator, ensuring that the transcriptional program for hair differentiation is executed at the right intensity. The authors describe this as an essential regulatory layer of RNA modification in hair follicle morphogenesis and cycling, one that operates through precise post-transcriptional control of a key transcriptional circuit to ensure structural integrity and timely regeneration.

For the broader field of RNA modification biology, the study adds hair follicle cycling to the growing list of developmental and physiological processes controlled by m7G methylation. It also highlights the specificity of the mechanism: although METTL1 modifies many transfer RNAs, the authors found that its effects on hair follicle biology run, at least in part, through internal modification of a single messenger RNA target. This kind of transcript-selective action suggests that m7G marks may function as individualized tuning knobs on particular messages rather than as a blanket adjustment of global protein synthesis, a distinction that will likely shape future experiments in other tissues.

Practical implications remain speculative but tantalizing. Hair loss disorders affect a large fraction of the human population, and most current treatments act indirectly on the follicle cycle. A pathway that demonstrably accelerates regeneration when its enzyme is boosted, and that acts through defined molecular intermediaries, offers a fresh set of potential targets. At the same time, the severe developmental defects caused by METTL1 loss in keratinocytes caution that the pathway is deeply embedded in normal epithelial biology, and any intervention would need to respect its broader roles. For now, the study stands as a vivid demonstration that the fate of a hair, and perhaps of many other tissues, can hinge on a methyl group attached to a single guanosine deep inside a messenger RNA molecule.

Subject of Research: METTL1-mediated m7G RNA modification and its regulation of the hair follicle cycle through the HOXC13/FOXN1/DSG4 axis

Article Title: METTL1-mediated m 7 G modification regulates hair follicle cycle via the HOXC13/FOXN1/DSG4 axis

Article References: Gan, X., Li, Q., Xiong, Q., Huang, D., Liu, Z., Yin, Q., Jiang, S., Matsubara, T., Kokabu, S., Yan, W., & Yuan, Q. (2026). METTL1-mediated m7G modification regulates hair follicle cycle via the HOXC13/FOXN1/DSG4 axis. PLOS Genetics, 22(9), e1012307. https://doi.org/10.1371/journal.pgen.1012307

Image Credits: AI Generated

DOI: 10.1371/journal.pgen.1012307

Keywords: METTL1, m7G modification, RNA methylation, hair follicle cycle, keratinocytes, HOXC13, FOXN1, DSG4, post-transcriptional regulation, hair regeneration, PLOS Genetics, epigenetics

The clinical stakes are enormous. Diabetic foot ulcers alone affect more than 18 million people each year, and anyone with diabetes faces a lifetime risk of developing one between 19 and 34 percent. Once an ulcer appears, recurrence rates climb as high as 65 percent within five years, and roughly one in five patients ultimately requires amputation. The reason these wounds refuse to heal lies in a self-reinforcing pathological loop: persistent infection by bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa, which form antibiotic-resistant biofilms; a flood of pro-inflammatory cytokines including TNF-α, IL-1β, and IL-6 that traps the wound in its inflammatory phase; and a diabetic microenvironment marked by hyperglycemia, oxygen starvation, and destructive oxidative stress that degrades the extracellular matrix and blocks the migration of the fibroblasts and keratinocytes needed to close the wound.

Metal-based nanozymes attack this loop from multiple directions at once. These nanoparticles, built from metals or metal oxides such as cerium dioxide, iron oxide, and molybdenum disulfide, mimic the activity of natural enzymes like peroxidase, superoxide dismutase, and catalase. A copper-based nanozyme, for example, can exploit the Cu+/Cu2+ redox cycle to perform double duty: in the acidic conditions of an acute infection it behaves like a peroxidase, converting hydrogen peroxide into bactericidal hydroxyl radicals that shred biofilms, while in the alkaline environment of a chronic non-healing wound it switches to catalase-like behavior, decomposing hydrogen peroxide into oxygen to relieve tissue hypoxia. The same released copper ions then stabilize HIF-1α, the master regulator of the hypoxic response, driving vascular endothelial growth factor expression and new blood vessel growth even without low oxygen.

The review catalogs how each metal brings a distinct therapeutic personality. Zinc-based nanozymes suppress the NF-κB inflammatory pathway and disrupt bacterial membranes while supporting the matrix metalloproteinases that remodel healing tissue. Iron-based systems use Fenton chemistry to induce ferroptosis in bacteria and senescent cells, and can dampen the TGF-β/Smad signaling that fuels scar formation. Silver combines ion-mediated bacterial killing with photothermal therapy that penetrates biofilms. Magnesium degrades into ions that neutralize wound acidity and activate the Wnt/β-catenin pathway implicated in hair follicle regeneration. Manganese nanozymes generate oxygen from endogenous hydrogen peroxide while scavenging the superoxide radicals produced during ischemia-reperfusion injury. Cerium dioxide stands out for its self-regenerating Ce3+/Ce4+ antioxidant cycle, which can continuously neutralize reactive oxygen species without being consumed.

What elevates the field beyond simple chemistry is the growing mastery of structure-activity relationships. The review details how shrinking particles below five nanometers produces quantum confinement effects that unlock enzyme activities absent in larger particles; ultrasmall gold nanoclusters, for instance, display superoxide dismutase activity that bulk gold lacks. Single-atom nanozymes, in which isolated metal atoms are anchored into coordination sites such as Fe-N4 on nitrogen-doped carbon, achieve complete atomic utilization and catalytic activities orders of magnitude higher than their nanoparticle counterparts, closely mimicking the active centers of natural metalloenzymes. Shape matters too: cerium oxide nanorods expose high-energy crystal facets with lower oxygen vacancy formation energies than spherical particles, two-dimensional nanosheets eliminate diffusion limits by exposing nearly all their atoms, and hollow nanocages act as nanoreactors that concentrate substrates and dramatically amplify reaction rates.

In diabetic wound models, these design principles converge on striking results. One copper-based hydrogel system switches its dominant enzyme activity based on wound pH, killing bacteria in acidic conditions and promoting angiogenesis in alkaline ones. Iron-based dual-nanozyme cascades consume glucose to starve bacteria while generating hydroxyl radicals, a “starvation-enhanced chemodynamic” strategy that also lowers local blood sugar. Platinum systems automatically shift from ROS-generating sterilization in the early hypoxic phase to oxygen-producing repair as inflammation subsides. Multimetallic platforms push further: an Au-Cu aerogel with four enzyme-mimicking activities supplies its own hydrogen peroxide and oxygen, while an ultrasound-activated Cu-Au-L-arginine system runs a five-enzyme cascade covering ROS regulation, oxygenation, glucose control, and nitric oxide-driven angiogenesis. Some of the newest devices even integrate real-time glucose and pH monitoring into self-powered patches that use the generated electric field to stimulate keratinocyte migration.

Perhaps most provocatively, the review documents evidence that nanozymes can push healing past mere closure toward regeneration of skin appendages, the hair follicles, sebaceous glands, and sweat glands whose loss is what separates a scar from true skin. Cerium dioxide nanozymes delivered by microneedle patches outperformed minoxidil in animal models of androgenetic alopecia, clearing ROS around follicles while the microneedles themselves triggered Wnt/β-catenin activation. Nickel-copper bimetallic nanozymes co-delivered with minoxidil achieved 83.4 percent transdermal efficiency and restored follicular stem cell proliferation by generating oxygen in situ. In wound models not designed to study hair at all, researchers repeatedly observed unexpected follicle and sweat gland regrowth, including in a cerium-based hydrogel treated diabetic wound study where RNA sequencing revealed abundant appendage formation alongside complete closure, likely driven by Wnt ligands secreted by M2-polarized macrophages.

On scarring, the review identifies molybdenum, zirconium, and cerium systems as the most promising anti-fibrotic agents. A molybdenum-based nanoscaffold with SOD and GPx-like activity blocks the ROS-TGF-β1 feedback loop by preventing oxidation of the latency-associated peptide that releases active TGF-β1, and metabolomic analysis showed it starves myofibroblasts of the glycine and glutamate raw materials needed for collagen triple helix assembly. Zirconium-doped Prussian blue nanozymes reprogram macrophages toward the anti-inflammatory M2 phenotype while preserving mitochondrial function, and a tannic acid-modified cerium hydrogel spray normalized collagen organization to resemble healthy skin architecture. The authors caution, however, that indiscriminate ROS scavenging can backfire, since reactive oxygen species serve as essential signaling molecules in early healing, and that current studies often cannot distinguish genuine anti-fibrotic reprogramming from the passive benefit of faster wound closure.

The path to the clinic remains steep. No metal nanozyme drug has yet received FDA approval for dermatological use, and only one nanozyme therapeutic has entered clinical trials, a Phase II nanozyme-hydrogel dressing for diabetic wounds. Biosafety concerns differ sharply by context: on open wounds, nanoparticles can translocate into the bloodstream and accumulate in the liver and spleen, silver carries the risk of permanent argyria, copper has a narrow therapeutic window before triggering cuproptosis, and manganese poses neurotoxicity at relatively low exposure thresholds. The safest candidates are those the body already knows how to handle, iron and zinc, which enter endogenous metabolic pools, and molybdenum, which oxidizes into non-toxic molybdate ions that the kidneys readily excrete. Regulatory ambiguity compounds the problem, since a catalytic nanozyme may be classified as a drug while the same material in a dressing may be treated as a device, and manufacturing consistency at kilogram scale, particularly for single-atom architectures, remains a formidable engineering challenge.

The review’s authors frame the future in terms of a shift from material-centric to pathology-centric design: sequential therapies that deploy copper or silver for initial debridement and then cerium or manganese for remodeling, stimuli-responsive systems that switch from bacterial killing to tissue repair as the wound environment changes, and next-generation platforms that combine nanozymes with stem cell niches, gene delivery, and smart bioelectronic dressings. If the field can solve its biosafety and manufacturing bottlenecks, metal-based nanozymes may finally deliver what chronic wound patients have awaited for decades, not just closed skin, but skin that works.

Subject of Research: Metal-based nanozymes for skin regeneration, chronic wound healing, anti-scarring therapy, and hair follicle restoration

Article Title: Skin regeneration axis under metal-based nanozymes: from chronic wound healing to structural and functional restoration

Article References: Zhuang, Z.-M., Guo, K., Wu, Z.-R., Wang, Y., Zhong, X.-C., Chen, C.-Y., Feng, Z.-X., Yu, Y.-Z., Zhang, H.-Q., Tan, M.-H., Zhang, T., Lin, X.-Y., Wang, Y., & Tan, W.-Q. (2026). Skin regeneration axis under metal-based nanozymes: from chronic wound healing to structural and functional restoration. Journal of Advanced Research, 88, 1013-1043. https://doi.org/10.1016/j.jare.2026.01.068

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.01.068

Keywords: nanozymes, skin regeneration, chronic wounds, diabetic foot ulcers, wound healing, scarring, hair regeneration, reactive oxygen species, nanomedicine, biofilms, cerium dioxide, regenerative medicine