Topical rapamycin reduces markers of senescence and aging in human skin: an exploratory, prospective, randomized trial

Abstract

Aging is a major risk factor for the majority of human diseases, and the development of interventions to reduce the intrinsic rate of aging is expected to reduce the risk for age-related diseases including cardiovascular disease, cancer, and dementia. In the skin, aging manifests itself in photodamage and dermal atrophy, with underlying tissue reduction and impaired barrier function. To determine whether rapamycin, an FDA-approved drug targeting the mechanistic target of rapamycin (mTOR) complex, can reduce senescence and markers of aging in human skin, an exploratory, placebo-controlled, interventional trial was conducted in a clinical dermatology setting. Participants were greater than 40 years of age with evidence of age-related photoaging and dermal volume loss and no major morbidities. Thirty-six participants were enrolled in the study, and nineteen discontinued or were lost to follow-up. A significant (P = 0.008) reduction in p16^INK4A protein levels and an increase in collagen VII protein levels (P = 0.0077) were observed among participants at the end of the study. Clinical improvement in skin appearance was noted in multiple participants, and immunohistochemical analysis revealed improvement in histological appearance of skin tissue. Topical rapamycin reduced the expression of the p16^INK4A protein consistent with a reduction in cellular senescence. This change was accompanied by relative improvement in clinical appearance of the skin and histological markers of aging and by an increase in collagen VII, which is critical to the integrity of the basement membrane. These results indicate that rapamycin treatment is a potential anti-aging therapy with efficacy in humans.Trial registration ClinicalTrials.gov Identifier: NCT03103893.

Keywords: aging; keratoses; mTOR; photoaging; rapamycin; senescence.

Fig. 1

a Topical rapamycin treatment reduces expression of the senescence regulator p16^INK4A. Human skin was treated with a formulation of 10 μM rapamycin or an identical formulation containing a vehicle control for 6–8 months; 0.5 cc of formulation was applied daily. Skin biopsies (n = 8) were taken at end of study and processed for immunohistochemistry as described in “Methods” section. Nuclear p16^INK4A was quantified using the Leica Aperio software system with a nuclear stain algorithm. b Topical rapamycin reduces signs of photoaging. Hematoxylin-eosin stain of human skin biopsies from the dorsal hands following application of topical cream containing rapamycin (10 μM) or placebo as in a. Histologic evidence of photoaging-actinic (solar) elastosis is indicated with an arrow. A reduction in the presence of these histologic markers of age-damaged skin was noted in multiple patient biopsies treated with rapamycin. c Topical rapamycin improves cytokeratin 5/6 distribution in human skin. Human skin biopsies from the dorsal hands of subjects following application of topical cream containing rapamycin or placebo as in a were stained with antibodies recognizing cytokeratin 5/6 (brown staining), a marker for basal cells in the epidermis. Note that staining in rapamycin-treated skin is more focally located in the basal layer of the skin while skin receiving placebo shows cytokeratin 5/6 staining in the stratum granulosum indicative of incomplete differentiation typical of aged skin

Fig. 2

Topical rapamycin increases collagen VII in the basement membrane of human skin. Biopsies from patients (n = 6), placebo- and rapamycin-treated skin were processed for immunohistochemistry and stained using antibodies specific for the collagen VII protein

Fig. 3

Rapamycin treatment improves clinical signs of aging in the skin. Clinical improvement in a 65-year-old woman (a) and a 67-year-old woman (b) following application of 10 μM rapamycin cream for 6–8 months. The placebo-treated hand is provided for comparison. in c, overall clinical improvement on 3 scales, the Glogau Classification of Photoaging, wrinkling measured on a 1-4 Likert scale, and the Merz Hand Grading Scale for aging skin, is presented for all subjects completing the study. Lower score on all scales correlates with reduced clinical severity