Fig. 1.
a Topical rapamycin treatment reduces expression of the senescence regulator p16INK4A. 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 p16INK4A 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