The central clinical message of the review is a race against time. In its early inflammatory stage, traction alopecia is potentially reversible: the follicle is irritated and inflamed, but it has not yet been irreversibly destroyed. If the mechanical stress continues unrecognized, however, the chronic tension gradually converts the condition into a permanent scarring alopecia, in which follicles are replaced by fibrous tissue and hair can never regrow. This window of reversibility is precisely why delayed recognition is so consequential. The authors emphasize that clinicians, hairstylists, and patients themselves often fail to connect early signs, such as marginal hairline thinning, small bumps around follicles, or broken hairs at the temples, with the hairstyles and habits that cause them, allowing a preventable condition to progress to an irreversible one.

The biological mechanism is deceptively simple. Hair follicles are anchored in the scalp and nourished by a rich supply of blood vessels and supporting structures, including the dermal papilla, which signals hair growth. When hairstyles pull repeatedly on hairs, for example tight braids, ponytails, weaves, extensions, or tightly wrapped head coverings, the constant tension damages the follicle at its weakest points. Over time this mechanical stress triggers inflammation around the follicle, and the body’s repair response can ultimately scar the area. The review also highlights an underappreciated risk factor known as nocturnal traction: hairstyles maintained while sleeping, such as tight buns or rollers worn overnight, can exert tension for hours at a time without the wearer noticing. Occupational practices contribute as well, from the documented nurse’s cap alopecia caused by pinned caps to studies of alopecia among active-duty service women whose tight hair buns were required by uniform standards.

Diagnosis relies on a combination of clinical pattern recognition, trichoscopy, and, when necessary, histopathology. Traction alopecia characteristically affects the hair margins, the hairline, temples, and nape of the neck, because these are the areas where styling tension is greatest. Trichoscopic findings evolve with disease stage: early disease may show peripilar casts, broken hairs at different lengths, and small pustules or black dots at the margins, while later disease shows decreased hair density, loss of the vellus hairs that normally fringe the hairline, and eventually smooth, scarred skin devoid of follicular openings. The review notes that standardized clinical photography is increasingly recommended to document hair loss progression over time, an important tool given how slowly and subtly the condition advances. Histopathology in late-stage disease confirms the replacement of follicles with fibrous tissue, cementing the diagnosis of scarring alopecia and ending any hope of spontaneous regrowth in affected zones.

What sets this review apart is its insistence that traction alopecia cannot be understood, or treated, in isolation from identity and culture. Hair plays a distinctive role in personal identity, self-esteem, confidence, and social belonging, and this is nowhere more evident than in the communities most affected by the condition. The authors draw on literature documenting the cultural significance of hair among Black women and girls, where hairstyles such as braids, locs, and weaves carry deep historical and social meaning, and where hair satisfaction has been shown to influence body image and appearance evaluation among Black adolescent girls. Similar cultural dimensions appear in other communities: traction alopecia has been described in Sikh men who tie their hair under turbans, in hijab-wearing women, and in Orthodox Jewish populations using skull caps with pin fasteners. Any management plan that ignores these cultural contexts, the authors argue, is unlikely to succeed, because patients may be asked to give up practices central to their identity without being offered meaningful alternatives.

This cultural sensitivity extends to prevention, which the review treats as the cornerstone of management. The evidence base includes practical guidance from dermatology organizations on reducing damage from weaves and extensions, recommendations to rotate hairstyles, avoid excessive tension at the hairline, and take breaks between chemically processed or tightly styled periods. The review also underscores knowledge gaps: a prior study in the same journal documented substantial gaps in healthy hair care knowledge within the African American community, suggesting that public education must be delivered in culturally responsive ways, ideally through trusted messengers such as hairstylists, community health workers, and clinicians trained to discuss hair practices without judgment. Pediatric cases deserve particular attention, since braids and ponytails in young children can initiate follicular damage early, and prevention habits established in childhood carry lifelong benefits.

Once the condition is established, treatment options fall into several tiers. Behavioral modification, loosening or changing hairstyles, remains the single most important intervention, and it is most effective before scarring sets in. Pharmacological options include topical minoxidil to support regrowth in affected but not yet scarred areas, and increasingly low-dose oral minoxidil, whose safety has been assessed in multicenter studies of more than a thousand patients. Interestingly, the review cites work suggesting that alpha-1 adrenergic agonist induced piloerection, the involuntary standing of hairs, may theoretically protect against traction damage, an intriguing pharmacological angle on a mechanical problem. For advanced, scarred disease, surgical options such as hair transplantation are the mainstay, and the review points to the broader literature on hair restoration techniques for reconstructing lost hairlines.

The review then surveys a range of adjunctive and emerging therapies that reflect the regenerative turn in dermatology. Platelet-rich plasma injections, microneedling, low-level light therapy, exosome treatments, and stem cell based approaches are all discussed as strategies to stimulate follicular recovery, though the authors are careful to note that the evidence for many of these modalities in traction alopecia specifically remains limited. Nutraceuticals, including vitamin and mineral supplementation where deficiencies exist, and botanical agents such as Withania somnifera root extract, which has been tested in a randomized placebo-controlled trial for hair health, round out the adjunctive landscape. Wigs and hair prostheses are also addressed as important options for patients with established loss, with practical guidance on selecting appropriate devices that do not themselves create new tension or pressure damage, a phenomenon documented in case series of hair system-induced alopecia.

The most distinctive contribution of the review is its exploration of osteopathic medicine’s role. Osteopathic physicians are trained in a biopsychosocial, whole-person model, and osteopathic manipulative treatment encompasses hands-on techniques, including lymphatic procedures, aimed at improving tissue mobility, circulation, and lymphatic drainage. The authors review osteopathic literature on the application of manipulative treatment to dermatological disease and on the lymphatic system’s role in tissue repair and regeneration, and they note experimental evidence that standardized scalp massage can increase hair thickness by inducing stretching forces on dermal papilla cells in the subcutaneous tissue. They also discuss the potential relevance of vagal tone and vagal nerve stimulation to anti-inflammatory regulation, a growing research area with documented effects in inflammatory conditions. The authors are explicit that osteopathic interventions for traction alopecia have not yet been rigorously tested and call for future studies to evaluate them, positioning OMT as a promising adjunct rather than a proven therapy.

Ultimately, the review’s conclusion is that restoring hair growth is only part of the therapeutic goal. Because hair loss carries a significant psychological burden, with documented links between alopecia and psychiatric distress, management must include psychosocial support and counseling alongside medical treatment. The authors argue for an integrated model in which evidence-based dermatologic care, culturally responsive education, behavioral change, and appropriate adjunctive therapies are combined in a patient-centered plan. For a condition that is entirely preventable yet frequently irreversible by the time it reaches the clinic, that reframing may be the review’s most important contribution: the best treatment for traction alopecia begins long before the dermatologist’s office, in the everyday choices about how hair is styled, and in a health system prepared to meet patients where their hair, and their identity, actually lives.

Subject of Research: Traction alopecia: causes, diagnosis, and holistic management of tension-induced hair loss

Article Title: Holistic review of traction alopecia: osteopathic medicine insights and beyond

Article References: Carnemolla, A. R., Kemelmakher-Liben, K., Gill, S., Sanjabi, T., Hassan, L., Eppley, D. A., & Elway, M. (2026). Holistic review of traction alopecia: osteopathic medicine insights and beyond. Archives of Dermatological Research, 318(1), Article 503. https://doi.org/10.1007/s00403-026-04991-z

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04991-z

Keywords: traction alopecia, hair loss, scarring alopecia, osteopathic medicine, osteopathic manipulative treatment, hair follicle, dermatology, trichoscopy, minoxidil, hair care practices, cultural hairstyling, prevention

Hoxc13 belongs to the Hox family of homeobox transcription factors, master regulators of embryonic patterning that specify body plans along the head-to-tail axis. Within this family, Hoxc13 has long been recognized as a critical controller of integumentary appendages, the skin-derived structures that include hair, nails, and claws. Previous work by the same team had shown that during mammalian evolution, the Hoxc13 protein acquired a characteristic polyglycine repeat insertion that distinguishes it from its non-mammalian homologs, the related proteins found in birds, reptiles, and other vertebrates. The new study set out to test whether this small structural addition actually changes what the protein can do at the genome-wide level, and whether that change could plausibly have contributed to the emergence of hair.

To answer this question, the researchers employed an elegant experimental design built around two versions of the Hoxc13 protein from cashmere goats. The first, designated Hoxc13-W, is the wild-type protein carrying the intact polyglycine repeat. The second, Hoxc13-S, is a shortened variant in which the polyglycine fragment has been deleted, mimicking the ancestral, non-mammalian form of the protein. Both proteins were synthesized using an in vitro expression system, allowing the team to compare their DNA-binding behavior directly without the confounding effects of living cells. This reductionist approach isolates the intrinsic DNA-binding capacity of each protein variant, a critical consideration when the goal is to attribute functional differences to a specific structural feature.

The centerpiece of the study was DNA affinity purification sequencing, or DAP-seq, a technique that uses purified proteins to fish out genomic DNA fragments they can bind, which are then identified by high-throughput sequencing. The results were striking. Hoxc13-W, the version with the polyglycine repeat, identified 12,679 binding peaks across the goat genome. Hoxc13-S, lacking the insertion, identified only 3,634 peaks. Even more telling was the overlap: just 243 peaks were shared between the two proteins. In other words, the vast majority of genomic sites bound by the wild-type protein were not recognized by the polyglycine-deleted variant, and vice versa. A single short amino acid insertion had fundamentally rewired the DNA-binding landscape of this transcription factor, transforming it from a relatively restricted regulator into one with a vastly expanded reach.

Functional enrichment analysis of the genes associated with these binding peaks revealed why this expansion matters for hair. The targets of Hoxc13-W were specifically enriched in pathways governing hair follicle morphogenesis and cycling, the developmental programs that build follicles and drive them through their growth, regression, and resting phases. By contrast, the targets of Hoxc13-S clustered primarily in the axon guidance pathway, a set of genes involved in steering neuronal growth cones rather than in skin biology. This shift in target preference suggests that the polyglycine insertion did not merely add more binding sites but redirected the protein toward an entirely different set of biological functions, aligning its regulatory activity with the demands of building hair-producing skin.

One of the most consequential findings concerned the Wnt signaling pathway, a cascade of intercellular communication that plays a central and well-documented role in hair follicle development, stem cell activation, and the hair growth cycle. Within this pathway, Hoxc13-W bound 30 genes, while Hoxc13-S bound only 5. The sixfold difference in Wnt pathway coverage implies that the polyglycine-bearing form of Hoxc13 can exert far broader control over one of the most important signaling networks in hair biology. Because Wnt signaling is repeatedly recruited at multiple stages of follicle morphogenesis and regeneration, an expanded capacity to regulate Wnt pathway genes could have provided mammalian ancestors with finer and more powerful control over hair production.

The study also probed how the polyglycine repeat affects the recognition of cis-regulatory motifs, the short DNA sequences to which transcription factors attach. Motif analysis demonstrated that the polyglycine fragment substantially influenced the motifs associated with Hoxc13 binding beyond the core Hoxc13-binding motif, which has the consensus sequence 5′-ATAAA-3′. This suggests that the insertion does not simply strengthen or weaken binding to the same sequence; rather, it changes the sequence context in which the protein operates, likely through cooperation with other DNA-bound factors or through altered preferences for flanking sequence features. Such changes in motif usage can ripple through regulatory networks, opening or closing access to large suites of target genes across the genome.

Molecular docking analysis added a structural dimension to the story. The computational modeling indicated that the polyglycine fragment alters the N-terminal structure of the Hoxc13 protein, the region involved in protein-protein interactions. Glycine is the smallest amino acid and confers exceptional conformational flexibility, so a repeat of glycine residues can act as a flexible hinge or spacer within a protein. By reshaping the N-terminal architecture, the insertion appears to affect how Hoxc13 interacts with partner proteins, which in turn influences how it engages DNA in a cellular context, since many transcription factors bind DNA effectively only as part of larger protein complexes. The polyglycine repeat, in this view, functions as a gain-of-function modification that enhances both the DNA-binding breadth and the interaction capacity of the protein.

Taken together, the findings support a model in which the polyglycine repeat insertion in Hoxc13 acted as an evolutionary gain-of-function mutation that amplified the Hoxc13-mediated gene regulatory network during the transition from non-mammalian to mammalian vertebrates. Rather than requiring wholesale changes in gene sequence or the emergence of entirely new genes, this scenario illustrates how a modest insertion of flexible, low-complexity sequence within a single transcription factor can reconfigure its binding profile, redirect its pathway targets, and reshape its protein interactions. Such low-complexity insertions are increasingly appreciated as a rich source of evolutionary novelty, capable of tuning protein behavior with relatively small mutational steps.

The research, conducted by Guanghao Yang, Chaoyong Huang, and colleagues at Inner Mongolia Minzu University, also carries practical implications beyond evolutionary biology. Cashmere goats, the species from which the two protein variants were derived, are prized for their fine undercoat fibers, and a deeper understanding of the Hoxc13-centered regulatory network could inform breeding strategies aimed at improving fiber quality and yield. More broadly, the study demonstrates the power of combining DAP-seq with pathway enrichment, motif analysis, and molecular docking to dissect the functional consequences of protein sequence evolution. While the polyglycine repeat is certainly not the sole driver of mammalian hair, the evidence presented here makes a compelling case that this tiny stretch of glycine helped tip the balance toward the furry integument that now defines the class Mammalia, from the wool of sheep to the whiskers of cats to the hair on our own heads.

Subject of Research: The role of a Hoxc13 polyglycine repeat insertion in mammalian hair and integument evolution

Article Title: Hoxc13 polyglycine repeat gain-of-function contributes to mammalian integument evolution by altering targeted genes and interactions

Article References: Yang, G., Huang, C., Yu, M., Li, W., Wu, D., Li, C., Hu, S., & Wu, J. (2026). Hoxc13 polyglycine repeat gain-of-function contributes to mammalian integument evolution by altering targeted genes and interactions. BMC Genomics. https://doi.org/10.1186/s12864-026-13314-5

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13314-5

Keywords: Hoxc13, polyglycine repeat, hair follicle, integument evolution, transcription factor, DAP-seq, Wnt signaling, gene regulation, mammalian evolution, cashmere goat, molecular docking, BMC Genomics

Androgenetic alopecia, often called male or female pattern hair loss, is the dominant cause of hair thinning worldwide, driven by a genetic sensitivity of hair follicles to dihydrotestosterone, a potent derivative of testosterone. Under its influence, follicles on the scalp gradually miniaturize, producing finer, shorter hairs over successive growth cycles until they eventually stop producing cosmetically meaningful hair at all. Because the condition is so widespread, affecting a large share of men by middle age and a substantial number of women, the market for supplements claiming to restore hair through nutrition has flourished, often citing older, smaller studies that reported altered levels of zinc, copper, or iron in people with hair loss.

The new investigation set out to test that idea at a scale rarely attempted before. The team retrospectively collected patient data from Sichuan Provincial People’s Hospital covering the period from October 2021 to December 2024. Patients diagnosed with androgenetic alopecia formed the experimental group, while healthy individuals served as controls. Serum concentrations of copper, zinc, calcium, phosphorus, magnesium, iron, selenium, manganese, molybdenum, nickel, chromium, cobalt, and lithium were quantified using inductively coupled plasma mass spectrometry, an analytical technique capable of detecting metals and metalloids at extraordinarily low concentrations by ionizing atoms in a plasma torch and sorting the resulting ions by their mass-to-charge ratio.

The statistical analysis, performed with GraphPad Prism 9.0 software, used unpaired t-tests to compare the two groups, with a threshold of P less than 0.05 for significance. Out of the full panel of elements, only four showed statistically significant differences between patients and controls: copper, lithium, calcium, and phosphorus. And even those differences, on close inspection, were modest and clinically unconvincing. Serum copper averaged 897.8 plus or minus 164.2 nanograms per milliliter in the alopecia group versus 922.3 plus or minus 188.2 in the controls, both comfortably inside the reference interval of 240 to 2000 nanograms per milliliter. Serum lithium, measured at 1.20 versus 1.35 nanograms per milliliter, sat far below the upper limit of 200 nanograms per milliliter in both groups.

Calcium and phosphorus told a similar story of technical significance without clinical meaning. Some individuals in the control group had serum calcium values exceeding the reference interval of 80 to 100 micrograms per milliliter, but the proportion of out-of-range results was similar in both groups, indicating no meaningful association with hair loss. Phosphorus levels remained within the reference interval of 25 to 200 micrograms per milliliter in more than 99 percent of participants in both arms of the study. In other words, the elements that reached statistical significance did so on the strength of a very large sample size, which can detect tiny shifts that would go unnoticed in smaller cohorts, rather than because of any dramatic biological divergence.

Perhaps most striking was what did not differ at all. Zinc, the element most frequently blamed for hair loss in popular nutrition discourse, showed no statistically significant difference between patients and healthy controls. Neither did magnesium, iron, manganese, molybdenum, nickel, selenium, chromium, or cobalt. This null result carries particular weight because zinc and iron have been the focus of numerous earlier investigations, some of which reported lower serum levels in people with various forms of hair loss, fueling a persistent belief that supplementation could slow or reverse the process. The new data, drawn from a far larger patient population, undercut that assumption for androgenetic alopecia specifically.

The authors draw a direct practical conclusion: because serum trace element levels in patients with androgenetic alopecia fall within reference intervals and do not differ meaningfully from those of healthy individuals, routine screening of serum trace elements in these patients is not recommended. That recommendation, if adopted widely, could reshape clinical practice. Dermatologists frequently order panels of micronutrient tests when patients present with pattern hair loss, partly to reassure anxious patients and partly because historical literature suggested deficiencies might contribute. Each panel costs money, delays diagnosis, and can lead to unnecessary supplementation, which is not always harmless. Excess selenium, for example, has been linked in animal studies to changes in hair structure, and indiscriminate zinc supplementation can interfere with copper absorption.

The biology of why trace elements became suspects in the first place is not entirely unreasonable. Zinc participates in hundreds of enzymatic reactions, including processes central to the hair follicle cycle, and severe zinc deficiency is a documented cause of hair loss in conditions such as acrodermatitis enteropathica. Iron deficiency anemia is associated with diffuse hair shedding. Copper is a cofactor for enzymes involved in cross-linking keratin, and experimental work has explored copper-binding peptides in tissue remodeling. Selenium-dependent enzymes protect follicles from oxidative stress. The follicle, one of the most metabolically active structures in the human body, plausibly depends on an adequate mineral supply, which is precisely why the absence of measurable serum differences in this study is informative: the problem in androgenetic alopecia is not supply but signaling.

That signaling problem is hormonal and genetic. Follicles in the scalp of susceptible individuals express androgen receptors and the enzyme 5-alpha reductase, which converts testosterone into dihydrotestosterone. In these follicles, dihydrotestosterone binding to the androgen receptor triggers a cascade that shortens the growth phase of the hair cycle and progressively miniaturizes the follicle. Recent research has even traced how miniaturization depletes follicular stem cells through mechanosensory signals involving calcium flux and inflammatory mediators, an intracellular pathway entirely independent of how much calcium circulates in the serum. Approved treatments, including topical minoxidil and oral finasteride, act on vascularization and hormone conversion respectively, not on nutrition, and their efficacy reflects the true nature of the disease.

None of this means nutrition is irrelevant to hair health in general. Diffuse shedding can accompany crash dieting, malabsorption disorders, or genuine deficiencies, and clinicians should still investigate those contexts. But the distinction matters: androgenetic alopecia is a genetically programmed, hormone-driven process, and this study provides the strongest evidence yet that a blood test for minerals will not reveal anything useful about it. For the millions of people spending money on mineral supplements in the hope of regrowing a receding hairline, the message from this large, carefully measured dataset is blunt and liberating at once. The minerals are there. The hair loss has other causes, and future progress will come from targeting the hormonal and molecular machinery of the follicle itself rather than the chemistry of the bloodstream that feeds it.

Subject of Research: Serum trace element concentrations in patients with androgenetic alopecia compared with healthy controls

Article Title: A study on the serum trace element concentration in patients with androgenetic alopecia

Article References: Sun, H., Luo, J., & Xie, C. (2026). A study on the serum trace element concentration in patients with androgenetic alopecia. Archives of Dermatological Research, 318(1), Article 486. https://doi.org/10.1007/s00403-026-04967-z

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04967-z

Keywords: androgenetic alopecia, trace elements, serum copper, zinc, hair loss, inductively coupled plasma mass spectrometry, micronutrients, dermatology, clinical screening, mineral supplements, hair follicle, case-control study

Dermal papilla cells, or DPCs, sit at the base of the hair bulb and act as the command centre of the follicle. Richly supplied with blood vessels and nerves, they release a cocktail of paracrine signalling molecules, including vascular endothelial growth factor, fibroblast growth factors and Wnt ligands, that guide the proliferation and upward migration of surrounding follicular matrix cells. Those migrating cells then differentiate into the hair bulb and the inner and outer root sheaths, the protective sleeves that surround the growing hair shaft. DPCs effectively determine follicle size, the duration of the active growth phase known as anagen, and the overall rhythm of the hair cycle. When these cells malfunction, the consequences include follicle miniaturisation and atrophy, the hallmarks of conditions such as alopecia. Understanding what makes DPCs proliferate, and what holds them back, is therefore a central question in hair biology.

Androgens occupy a paradoxical position in this story. DHT, a potent metabolite of testosterone, promotes the growth of body hair in areas such as the beard and underarms, yet its excessive accumulation in genetically sensitive regions of the scalp drives androgenetic alopecia, the most common form of hair loss in humans. Previous studies have suggested that DHT may shift the balance between proliferation and apoptosis in DPCs by modulating pathways such as Wnt/β-catenin and TGF-β/Smad, but the precise mechanisms have remained elusive. The TGF-β superfamily comprises more than 30 ligands, including bone morphogenetic proteins, activins, inhibins and growth differentiation factors. In the canonical pathway, TGF-β ligands bind serine/threonine kinase receptors on the cell surface, triggering receptor-regulated Smads such as Smad2 and Smad3 to form complexes with the common mediator Smad4. These complexes enter the nucleus and regulate gene transcription, while inhibitory Smads such as Smad7 provide a built-in brake on the system.

The research team, working at Tarim University, chose their model with care. The Hetian sheep, an indigenous breed from the Hetian area of Xinjiang, is prized for high-quality wool and remarkable adaptation to extreme environments. Neonatal lambs, just three days old, were selected as donors because their dermal papilla cells show superior viability and proliferative potential, their low endogenous androgen levels minimise hormonal interference, and a uniform age group ensures biological consistency. Under institutional ethics approval, a small full-thickness skin sample was excised from the shaved dorsal skin of a healthy female lamb under local anaesthesia and strict aseptic conditions. The wound was treated with topical antibiotics and monitored daily until complete healing, reflecting the careful husbandry that underpins the entire cell culture enterprise.

Isolating the cells demanded considerable surgical precision at the microscopic scale. Skin specimens were minced into fragments and digested with collagenase type II at 37 degrees Celsius, after which intact hair follicles were separated by filtration and centrifugation. Using microdissection forceps and micro-spring scissors under a dissection microscope, researchers incised the narrowest region of the hair bulb, the dermal papilla neck, and gently detached the papilla with a glass capillary exploiting surface tension. Each isolated papilla was transferred to an individual well for primary culture. Within five days, polygonal cells migrated from the explants, forming growth halos that eventually covered half the well surface. By day twelve, the cultures had reached seventy to eighty percent confluency with a uniform, spindle-shaped morphology characteristic of healthy DPCs, and all nine replicate wells from the single donor were successfully established.

Identity verification was rigorous. Haematoxylin and eosin staining revealed cells with abundant nucleoli, while Giemsa staining highlighted the light-blue cytoplasm and central purplish-red nuclei. Chromosomal karyotype analysis confirmed 54 chromosomes per cell, comprising 26 pairs of autosomes and one pair of sex chromosomes, matching the standard sheep genome and proving the cells were genuinely of ovine origin. More decisively, double immunofluorescence staining demonstrated co-expression of CD133 and α-smooth muscle actin. CD133 is a surface marker highly expressed in human and murine DPCs but largely absent from other skin cell types, and recent hair follicle reconstitution assays have shown that CD133-high DPCs are the primary cellular drivers of new follicle formation. α-SMA, meanwhile, marks the contractile, myofibroblast-like properties that help DPCs maintain follicular structure. Together, these markers confirmed the cultures as authentic, hair-inductive dermal papilla cells.

With the model validated, the team turned to the central question: what does DHT do to these cells? Third-passage DPCs were treated with DHT concentrations spanning four orders of magnitude, from 1 to 1000 nanomolar, a range chosen to encompass physiologically relevant levels in androgen-responsive tissues and to extend into the supra-physiological realm to probe dose-dependent saturation. After 48 hours, the CCK-8 viability assay showed no significant differences across concentrations, but the more sensitive EdU assay, which directly measures DNA synthesis through flow cytometry, told a different story. Proliferation capacity rose steadily with increasing DHT concentration, peaking at 1000 nanomolar, where the difference from untreated controls reached statistical significance. The cells, in other words, were not merely surviving the hormone; they were dividing more vigorously in its presence.

The molecular explanation emerged from quantitative PCR analysis of eleven genes spanning the TGF-β ligand, receptor and Smad families. In cells treated with 1000 nanomolar DHT, expression of TGF-β1 and its receptor TGF-βRII was significantly downregulated, while TGF-β2 and TGF-β3 remained unchanged. Within the Smad family, DHT treatment reduced Smad2 and Smad6 expression, increased Smad5, and left Smad1, Smad3, Smad4 and Smad7 untouched. The pattern is mechanistically telling: Smad5 mediates BMP signalling, whereas Smad6 inhibits it, so the concurrent rise of Smad5 and fall of Smad6 suggests androgens may indirectly amplify BMP signalling, a pathway known to regulate follicle cycle timing, size and spacing. Meanwhile, the suppression of TGF-β1, a profibrotic cytokine that previous work has linked to reduced keratinocyte proliferation in co-culture, points to a release of the proliferative brake that TGF-β normally applies to the follicle microenvironment.

The authors are candid about the limits of the study. All experiments derived from a single biological donor, with replicates being technical rather than biological, and the pathway conclusions rest on gene expression data alone. Protein-level validation by Western blot, rescue experiments using exogenous TGF-β1 or pharmacological Smad inhibition, and in vivo or three-dimensional culture systems would all strengthen the causal chain between DHT, TGF-β/Smad suppression and DPC proliferation. The contrast with human scalp DPCs, where DHT has been reported to delay cell cycle progression without boosting proliferation, also underscores how tissue-specific and species-specific androgen responses can be; androgenetic alopecia is confined to genetically sensitive scalp regions and does not occur in normal skin. Even so, the establishment of the first Hetian sheep DPC culture is a genuine advance. It links androgen regulation to follicle development in a system directly relevant to wool fibre quality, potentially supporting higher wool yields and greater economic value for a distinctive livestock breed, while offering human hair researchers a comparative model whose skin biology mirrors our own more closely than rodents ever could. For a hormone best known for taking hair away, DHT has just revealed a surprising talent for building it, at least in sheep.

Subject of Research: Androgen regulation of dermal papilla cell proliferation via the TGF-β/Smad signalling pathway in Hetian sheep

Article Title: Dihydrotestosterone Promotes Hetian Sheep Dermal Papilla Cell Proliferation by Inhibiting the TGF‐β/Smad Signalling Pathway

Article References: Wang, Q., Liu, X., Feng, Z., Zhang, J., Li, C., Shi, R., & Li, S. (2026). Dihydrotestosterone Promotes Hetian Sheep Dermal Papilla Cell Proliferation by Inhibiting the TGF‐β/Smad Signalling Pathway. Veterinary Medicine and Science, 12(5), Article e71118. https://doi.org/10.1002/vms3.71118

Image Credits: AI Generated

DOI: 10.1002/vms3.71118

Keywords: dihydrotestosterone, dermal papilla cells, TGF-β/Smad pathway, Hetian sheep, hair follicle, androgenetic alopecia, wool quality, cell proliferation, Smad signalling, hair biology, Xinjiang livestock, primary cell culture