Skin and hair are the most visible markers of human aging: they are the first cues others use to estimate someone's age, and they offer the clinician valuable information even before the examination begins. Historically, however, these two structures have been studied independently — skin as the domain of dermatology and aesthetic medicine, the hair follicle as the province of trichology. That approach is increasingly outdated. A growing body of evidence shows that the skin and its appendages share a profound biological kinship, and that their aging is not two parallel processes but a single molecular program.

This synchrony is well recognized clinically: skin atrophy in older individuals is almost always accompanied by hair thinning; exhaustion of hair follicle stem cells is closely linked to impaired epidermal barrier function; in several hereditary progeroid syndromes, premature changes in skin and hair develop simultaneously and follow similar cellular trajectories. This apparent synchrony has long awaited a molecular explanation.

A joint team of Chinese researchers, scientists, and clinicians took up that challenge. In 2026, their systematic review dedicated to the co-regulatory mechanisms of skin and hair aging was published in Experimental Gerontology [1]. The authors systematically examine the molecular cascades already established in skin aging — DNA damage accumulation, telomere shortening, oxidative stress, chronic low-grade inflammation, and stem cell exhaustion — and trace how each manifests in the hair follicle and the specific mechanisms linking the two processes.

The central idea: skin and the hair follicle form a "co-aging axis" with three hierarchical levels — trigger, amplifier, and effector — integrated through a single hub: the skin's neuro-immuno-endocrine system.

Mechanisms of co-aging: from DNA to stem cells

The authors identify several interconnected mechanisms acting simultaneously in the skin and the hair follicle.

• DNA damage and telomere shortening

With age, cells in both structures accumulate DNA damage — from ultraviolet radiation (UVR) and internal sources, including replication errors and progressive telomere shortening.
Telomeres — the protective end caps of chromosomes — shorten with each cell division; once a critical length is reached, p53 is activated and triggers cellular senescence. In the skin, this reduces keratinocyte proliferative capacity and impairs barrier function. In the hair follicle, telomere dysfunction suppresses the self-renewal of hair follicle stem cells (HFSCs). It disrupts the regulation of the BMP (bone morphogenetic protein)/pSmad/P63 axis, resulting in dysregulation of the hair growth cycle [2, 4].
Notably, telomerase activity — the enzymatic counterforce to telomere shortening — is essential for maintaining the HFSC pool: in experimental models, induction of telomerase reverse transcriptase (TERT) stimulated proliferation of these cells.

• Oxidative stress and mitochondrial dysfunction

Oxidative stress — the excess accumulation of reactive oxygen species (ROS) — is identified by the authors as the key driver of the "co-aging axis." ROS damage mitochondrial DNA (mtDNA) and impair the electron transport chain, thereby initiating a vicious cycle: mitochondrial dysfunction amplifies ROS production, which causes further damage.
In skin, this manifests as reduced collagen synthesis, increased matrix metalloproteinase (MMP) activity, and accelerated photoaging. In the hair follicle, excess ROS triggers apoptosis of melanocytes and their stem cell precursors —clinically presenting as graying — and disrupts the normal hair growth cycle.
The antioxidant defense system — including superoxide dismutase (SOD), catalase, and the Nrf2 transcription factor pathway — becomes less effective with age in both organs, closing the loop.

• Chronic inflammation ("inflammaging")

A chronic pro-inflammatory environment develops in aging skin and follicles alike. The NLRP3 inflammasome and the NF-κB (nuclear factor of kappa light chain-B) transcription factor are activated, thereby sustaining persistently elevated levels of the interleukins IL-1β, IL-6, and tumor necrosis factor-α (TNF-α). These cytokines degrade the skin's extracellular matrix (ECM) and disrupt the HFSC niche, thereby accelerating stem cell exhaustion [3].
The authors describe an additional channel of this cross-tissue inflammatory crosstalk: the Piezo1–calcium–TNF-α mechanosensory pathway links biomechanical changes in aging skin to inflammatory activation directly within the follicle.

• Stem cell exhaustion and extracellular matrix remodeling.

Under the cumulative pressure of all these stimuli, epidermal stem cells and HFSCs progressively lose their capacity for self-renewal and differentiation. A particularly important role in this process is played by the degradation of collagen type XVII (COL17A1): this protein anchors basal keratinocytes and maintains the normal architecture of the lower follicle, but under conditions of oxidative stress, it is degraded, causing stem cells to leave their niche and undergo premature exhaustion.
Declining activity of the Wnt/β-catenin signaling pathway simultaneously impairs skin elasticity and disrupts the function of dermal papilla cells (DPCs) — the key regulatory center governing the hair follicle growth cycle.

Skin as a neuro-immuno-endocrine organ

The authors place particular conceptual emphasis on the fact that skin functions as a neuro-immuno-endocrine organ, translating environmental signals into internal biological responses through the synthesis of corticotropin-releasing hormone (CRH), pro-opiomelanocortin (POMC) derivatives, neurotrophins, and vitamin D [5]. This system acts as the "master integrator" of all three levels of the "co-aging axis." UVR, in particular, exerts a photoendocrine effect, regulating the hair follicle cycle, melanocyte stem cell function, and the systemic stress response via α-melanocyte-stimulating hormone (α-MSH), β-endorphin, and vitamin D metabolites.

Limitations

The authors are candid about the boundaries of their conclusions. A substantial portion of the data derives from mouse models, and direct extrapolation to humans requires caution: telomere dynamics in human hair follicles, for instance, remain insufficiently characterized. The review draws on mechanistic data and does not provide systematic clinical validation. The authors call for the integration of multi-omics approaches, development of organoid models, and clinical cohort studies — to move from describing mechanisms to identifying specific regulatory nodes amenable to therapeutic intervention.

From mechanisms to treatment choices

The "one target, dual effect" concept carries concrete practical implications for the clinician.

Enhancing antioxidant defense — reduces oxidative damage in both skin and the follicle simultaneously:

• Niacinamide — topical and oral
• Vitamin E (tocopherol) — topical and oral
• Flavonoids — topical (limited penetration) and oral
• Nrf2 agonists, including lumisterol derivatives and vitamin D metabolites (20(OH)D₃) — topical and oral; the oral route is preferred for bioavailability

Suppressing inflammaging — improves the follicular microenvironment, slows HFSC exhaustion, and supports skin barrier function:

• Melatonin (inhibits NF-κB and AP-1, activates Keap1-Nrf2) — topical (lotions, hair serums) and oral (dietary supplement)
• Vitamin D derivatives (suppress IL-17 and TNF-α via NF-κB inhibition) — topical and oral
• Collagen hydrolysate (reduces TNF-α and IL-1β) — primarily oral: the molecule is too large to penetrate the stratum corneum
• Onion extract (inhibits NO production, modulates Wnt/β-catenin) — topical (shampoos, lotions) and oral
• EGCG (epigallocatechin gallate from green tea) — topical and oral
• JAK inhibitors (baricitinib, ruxolitinib) — block IFN-γ and IL-15 via the JAK-STAT pathway; demonstrated pronounced efficacy in alopecia areata (AA). These are prescription (Rx) drugs, not dietary supplements: topical ruxolitinib is FDA-approved for AA; baricitinib is used systemically; baricitinib encapsulated in mesenchymal stem cell-derived exosomes represents an experimental targeted delivery approach.

Melanin is discussed as a natural radical scavenger and a DNA repair stimulator with dual potential in the skin and hair follicles.

Supporting ECM homeostasis — aligns with the concept of systemic anti-aging intervention:

• Retinoids (stimulate collagen synthesis, inhibit MMPs) — topical; oral vitamin A with caution
• Collagen-stimulating peptides — topical and oral
• Wnt/β-catenin pathway activators (simultaneously support follicle regeneration and skin elasticity) — currently largely experimental
• Soy protein composites (reduce inflammation, stimulate follicle regeneration) — topical and oral

Emerging directions — highlighted by the authors:

• Exosomes derived from hair follicle mesenchymal stem cells — topical (under investigation); the oral route is not viable due to molecular instability
• Nanostructured biomimetic matrices — topical
• Complex formulations combining antioxidant, anti-inflammatory, and matrix-supporting components — topical and/or oral, depending on composition

Important note: most of the agents listed exert systemic effects via both routes of administration, which aligns well with the concept of the skin–hair follicle "co-aging axis." The nutraceutical route is especially relevant for collagen hydrolysate, flavonoids, and melatonin: these molecules penetrate the stratum corneum poorly but reach the follicle through systemic circulation. JAK inhibitors stand apart — they are the only group with Rx regulatory status, and their use falls outside the scope of aesthetic practice.

Conclusion

The review by Wu et al. makes a compelling case: skin aging and hair follicle aging are not two parallel processes but a single molecular program with shared triggers, amplifiers, and effectors. Understanding these connections reframes the logic of anti-aging interventions — from symptomatic treatment of individual organs to systemic correction of common molecular nodes.
For the practicing skincare specialist, this means, above all, a new perspective: a patient's skin and hair constitute a single aging system, and working with one inevitably affects the other. Understanding exactly how is what allows for more precise, targeted care.

References

1. Wu H., Liu H.-B., Cui Y.-X. et al. Co-regulatory mechanisms of skin and hair aging. Exp Gerontol 2026; 222: 113200.
2. Stone R.C., Aviv A., Paus R. Telomere dynamics and telomerase in the biology of hair follicles and their stem cells as a model for aging research. J Invest Dermatol 2021; 141(4s): 1031–1040.
3. Morinaga H., Mohri Y., Grachtchouk M .et al. Obesity accelerates hair thinning by stem cell-centric converging mechanisms. Nature 2021; 595(7866): 266–271.
4. Liu N., Yin Y., Wang H. et al. Telomere dysfunction impairs epidermal stem cell specification and differentiation by disrupting BMP/pSmad/P63 signaling. PLoS Genet 2019; 15(9): e1008368.
5. Slominski R.M., Raman C., Jetten A.M., Slominski A.T. Neuro–immuno–endocrinology of the skin: how environment regulates body homeostasis. Nat Rev Endocrinol 2025; 21(8): 495–509.