Tier 3 — preclinical

Fisetin Promotes Hair Growth by Augmenting TERT Expression

Chisato Kubo, Mizuki Ogawa, Norihisa Uehara, Yoshinori Katakura

Frontiers in Cell and Developmental Biology 2020 Volume 8, Article 566617

Bibliography

DOI: 10.3389/fcell.2020.566617
PubMed: PMID 33178686
PubMed Central: PMC7593534
Funding: This study was partially supported by the Japan Science and Technology Agency (JST) and the Japan International Cooperation Agency's (JICA) Science and Technology Research Partnership for Sustainable Development (SATREPS, Grant No. JPMJSA1506).
Competing interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Study snapshot

Design	Combined in vitro mechanistic study (reporter screen, shRNA rescue) and in vivo topical treatment study in mice
Model	HaCaT human keratinocyte cell line (in vitro); male C57BL/6 mice with dorsal hair follicles synchronised in telogen phase (in vivo)
Sample	In vitro experiments performed in triplicate, at least 3 independent replicates; in vivo n=9 mice per group across three arms (control, resveratrol, fisetin)
Intervention	In vitro: 10 μM fisetin (or resveratrol, urolithin A, sesamol, other polyphenols) in HaCaT culture medium. In vivo: 0.05 mL of 0.1% fisetin in 50% ethanol applied topically to shaved dorsal skin daily
Duration	In vitro: 48 h (primary readouts); up to 4 days for proliferation assays. In vivo: 35 days of daily topical application
Endpoints	hTERT promoter activity in HaCaT cells (EGFP reporter, imaging cytometer); Endogenous hTERT mRNA expression (qRT-PCR); IGF-1, KGF, and TGF-β1 cytokine gene expression (qRT-PCR); β-catenin transcriptional activity (TOP-Flash luciferase reporter); β-catenin protein expression and nuclear localisation (Western blot, immunofluorescence); AXIN2 expression as β-catenin downstream target; HaCaT cell proliferation (Cell Counting Kit-8); Rescue: hTERT shRNA knockdown effect on downstream readouts; In vivo hair regrowth on shaved dorsal skin (macroscopic, per-mouse); Dorsal skin mTERT and β-catenin mRNA (qRT-PCR); Dorsal skin thickness and hair follicle histology (H&E); Ki67-positive proliferating cells in skin sections (immunohistochemistry); CD34-positive hair follicle stem cells; TERT and β-catenin protein localisation (immunofluorescence)

What the study showed, in plain terms

This 2020 study from Kyushu University set out to find natural compounds that could switch hair follicles from their resting state (telogen) into their active growth state (anagen) by turning up a gene called TERT. TERT — telomerase reverse transcriptase — is best known for its role in maintaining chromosome ends in stem cells, but earlier work had shown that when TERT is switched on in the skin, it wakes up the resting stem cells that live in the base of hair follicles and triggers new hair growth.

The team ran a screen of polyphenols against human keratinocytes carrying a fluorescent reporter that lit up whenever the TERT gene was activated. Fisetin and resveratrol emerged as the strongest activators. The researchers then showed that fisetin's effect on downstream signalling — including the β-catenin pathway that governs hair follicle development — depended on TERT itself, because knocking TERT down with shRNA abolished the response.

To test whether this mattered in an intact organism, the team shaved the backs of young male mice (whose hair follicles were all in resting phase at that age) and painted them daily with a 0.1% fisetin solution in dilute ethanol for 35 days. All nine fisetin-treated mice showed clear hair regrowth compared with none in the vehicle group and five of nine on resveratrol. Fisetin-treated skin showed the expected molecular signature — higher TERT and β-catenin, more proliferating cells around the hair matrix and follicle stem cell region, and thicker skin — consistent with a full telogen-to-anagen transition.

Key findings

Fisetin activated the human TERT promoter in HaCaT keratinocytes and increased endogenous hTERT mRNA (both p<0.001 versus control).
Fisetin increased IGF-1 and KGF expression and decreased TGF-β1 — a cytokine profile associated with hair follicle activation rather than regression.
Fisetin activated β-catenin signalling: TOP-Flash reporter activity rose approximately 3-fold, AXIN2 (a β-catenin target) rose approximately 4-fold, and β-catenin protein accumulated and shifted into the nucleus.
shRNA knockdown of hTERT abolished fisetin's effects on β-catenin activity, cytokine expression, and keratinocyte proliferation — demonstrating that TERT is required for the downstream cascade rather than a bystander.
In male C57BL/6 mice with dorsal hair follicles synchronised in telogen, 35 days of daily topical 0.1% fisetin produced visible hair regrowth in 9 of 9 animals, compared with 5 of 9 for resveratrol and 0 of 9 for vehicle.
Fisetin-treated dorsal skin showed elevated mTERT and β-catenin mRNA, thickened epidermis, expansion of CD34-positive hair follicle stem cells, and Ki67-positive proliferation around hair matrix, dermal papilla, and inner/outer root sheath.

What this study can and cannot tell us

Preclinical only — no human clinical data, no evaluation against established hair-loss treatments such as minoxidil or finasteride.
Fisetin was delivered topically as a 0.1% ethanolic solution painted onto shaved skin. This study does not address whether oral fisetin supplementation would reproduce these effects, and there is no pharmacokinetic reason to assume it would; oral fisetin's low bioavailability and rapid metabolism make skin exposure a very different question.
Small in vivo sample size (n=9 per arm) and imprecise dosing — the authors note the polyphenol solution was applied and "made fit in by spatula" daily, a technique that introduces meaningful between-animal variation.
Male mice only; sex-limited findings.
35-day observation window captures induction of anagen but not longer-term follicle sustainability, hair cycle stability, or safety across multiple cycles.
Dose-response not characterised — only 10 μM (in vitro) and 0.1% topical (in vivo) tested.
HaCaT is an immortalised keratinocyte line with known genomic alterations; mechanistic findings should be confirmed in primary human keratinocytes and dermal papilla cells before firm clinical claims are made.
Statistical testing used repeated two-sided t-tests across many endpoints without correction for multiple comparisons.

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