As we age, our body’s largest organ—our skin—undergoes profound changes. The epidermis, the outermost layer of the skin, steadily thins over time, compromising its essential role as a barrier against environmental assaults. Nearly 90 percent of the cells in this layer are keratinocytes, which originate deep within the epidermis before migrating upward to form the protective stratum corneum. Age-related declines in keratinocyte proliferation and differentiation leave the epidermis more fragile and less able to fend off pathogens, ultraviolet radiation, and physical damage.
For decades, vitamin C (ascorbic acid) has been celebrated in dermatology for its antioxidant properties and its capacity to support collagen synthesis in the dermis. Yet until now, its direct effects on gene regulation within the epidermis remained murky. A pioneering team of researchers in Japan has illuminated how vitamin C can not only defend skin cells against oxidative stress but actively reprogram their genetic machinery to restore epidermal thickness and function—a discovery with profound implications for skin-aging therapies.
Research Collaboration Bridges Academia and Industry
This groundbreaking study was spearheaded by Dr. Akihito Ishigami, Vice President of Biology and Medical Sciences at the Tokyo Metropolitan Institute for Geriatrics and Gerontology (TMIG), in partnership with colleagues at Hokuriku University and scientists from ROHTO Pharmaceutical Co., Ltd. The interdisciplinary team included Associate Professors Ayami Sato (TMIG, now at Toyo University) and Yasunori Sato, Professor Toshiyuki Kimura, and Hideki Tanaka (Hokuriku University), along with ROHTO researchers Florence, Akari Kuwano, Yasunari Sato, and Tsuyoshi Ishii.
In a statement, Dr. Ishigami emphasized, “While vitamin C’s antioxidant roles have been well characterized, we sought to uncover whether it could influence epidermal renewal at the genetic and epigenetic levels. Our hypothesis was that vitamin C might exert control over keratinocyte proliferation through targeted changes in DNA methylation.”
Air-Liquid Interface Skin Model Mimics Human Epidermis
To interrogate vitamin C’s effects on skin regeneration, the investigators employed a sophisticated laboratory-grown system known as a human epidermal equivalent (HEE). In this model, keratinocytes are cultured at an air-liquid interface, allowing their upper surfaces to be exposed to air—just like genuine skin—while their basal layers receive nutrients from an underlying medium. This arrangement closely replicates the in vivo environment, enabling accurate assessment of nutrient uptake, cell signaling, and barrier formation.
Vitamin C was applied to the culture medium at concentrations of 0.1 mM and 1.0 mM, reflecting physiologically relevant levels likely achieved in human skin via dietary intake or topical application. The HEEs were then monitored over a two-week period, with tissue samples collected on days 7 and 14 for histological, molecular, and biochemical analyses.
Thicker Living Epidermis, Leaner Stratum Corneum
Brightfield microscopy and hematoxylin-eosin staining revealed striking structural changes in vitamin C–treated skin models. By day 7, the living (nucleated) cell layers of the epidermis were notably thicker in the vitamin C groups compared to controls, while the stratum corneum thickness remained unchanged. By day 14, the living epidermis had expanded further, whereas the stratum corneum became thinner—suggesting an accelerated turnover with robust keratinocyte formation and shedding of dead cells.
Immunohistochemical staining for Ki-67, a nuclear protein expressed exclusively in actively dividing cells, showed a significant increase in Ki-67–positive keratinocytes in the basal and suprabasal layers of vitamin C–treated HEEs. Quantitative analysis demonstrated a dose-dependent rise in proliferating cells, confirming that vitamin C directly stimulates keratinocyte cell-cycle entry and division.
Epigenetic Mechanism: DNA Demethylation via TET Enzymes
Delving deeper into the molecular underpinnings, the research team performed genome-wide DNA methylation profiling. They identified over 10,000 differentially methylated regions (DMRs) that became hypomethylated in response to vitamin C treatment. Hypomethylation of cytosine bases in DNA typically correlates with increased gene transcription, as methyl groups can impede the binding of transcriptional machinery.
Central to active DNA demethylation are the ten-eleven translocation (TET) family of enzymes, which oxidize 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC). This reaction requires ferrous iron (Fe2+), which—upon oxidation to Fe3+—must be reduced back to Fe2+ to sustain TET activity. Vitamin C, as a potent biological reductant, donates electrons to regenerate Fe2+, thereby preserving TET enzyme function.
Biochemical assays validated this mechanism: vitamin C–treated HEEs exhibited elevated global 5-hmC levels, and TET enzyme activity assays confirmed sustained oxidation of 5-mC in the presence of vitamin C. Furthermore, when a specific TET inhibitor was applied, the hypomethylation of key genomic regions was abrogated, and the proliferative boost conferred by vitamin C was lost—unequivocally proving the dependence on TET-mediated demethylation.
Upregulation of Proliferation-Related Genes
Integrating methylation data with RNA sequencing, the investigators pinpointed 12 proliferation-related genes whose expression rose by 1.6- to 75.2-fold under vitamin C treatment. These included cyclins, growth-factor receptors, and transcription factors known to drive cell-cycle progression and keratinocyte differentiation. The coordinated hypomethylation of promoter regions and corresponding gene activation offers a clear picture of how vitamin C orchestrates a genetic program for epidermal renewal.
Implications for Anti-Aging and Clinical Dermatology
Aging adults often contend with thinning skin that not only appears less vibrant but also predisposes them to injuries, delayed wound healing, and heightened sensitivity. The discovery that vitamin C—an accessible and safe nutrient—can epigenetically reactivate dormant gene networks in keratinocytes opens new avenues for therapeutic interventions. Topical formulations enriched with the optimal concentration of vitamin C, potentially combined with ingredients that facilitate penetration to basal keratinocytes, could reverse age-associated epidermal atrophy.
Dr. Ishigami highlighted the broader applications: “Beyond normal aging, patients with chronic wounds, radiation-damaged skin or genetic disorders affecting keratinocyte function could benefit from targeted vitamin C therapies. Reactivating the skin’s intrinsic regenerative machinery is a promising strategy to restore barrier integrity and resilience.”
Next Steps: From Bench to Bedside
While the HEE model provides robust mechanistic insight, human clinical trials will be essential to validate efficacy and safety in vivo. Future studies will explore optimal dosing regimens, delivery vehicles (creams, serums or microneedle patches), and the longevity of epigenetic changes in treated skin. Additionally, the interplay between vitamin C–induced demethylation and other epigenetic marks—such as histone modifications—warrants investigation to paint a complete picture of chromatin remodeling in keratinocytes.
Conclusion: Vitamin C as Epigenetic Architect of Youthful Skin
This landmark study, published online April 20 in the Journal of Investigative Dermatology, redefines vitamin C from a mere antioxidant to a powerful epigenetic modulator capable of restoring the structural and functional hallmarks of youthful epidermis. By championing keratinocyte proliferation through sustained TET enzyme activity and targeted DNA demethylation, vitamin C emerges as a frontline ally in the fight against skin aging.
Dr. Ishigami aptly summarized the work’s significance: “Our findings reveal how a simple nutrient can trigger complex genetic programs to thicken the skin and strengthen its defense capabilities. For older adults and patients with compromised epidermal health, vitamin C offers a beacon of hope to regenerate and protect their most visible organ.”
As clinical dermatologists and skincare innovators digest these insights, the future of anti-aging treatments looks set for a vitamin C–driven renaissance—one where the fountain of youth may just be locked inside a familiar molecule we’ve long underestimated.
