Effects of the selective TrkA agonist gambogic amide on pigmentation and growth of human hair follicles in vitro
Fig 4
A: Scheme of different hair follicle bulb compartments. Highly dendritic melanocytes of the pigmentary-unit (yellow) are located above the Auber’s line in contact with the basement membrane. Outside the pigmentary-unit (blue) and in the outer root sheath (green) they do not serve hair pigmentation. In the outer root sheath melanocytes rest as oligo-dendritic cells. Abbreviations: PU—pigmentary-unit. B: Immunohistochemical quantification of melanocytes with c-KIT, a marker for migrating and differentiating melanocytes. Melanocytes are labelled green, c-KIT-immunoreactive cells are labelled red. White boxes indicate origin of high magnification blow-ups. Bars = 15 μm. C: Macroscopic and microscopic analysis of dystrophy development and dendricity of melanocytes in the hair bulb of human hair follicles treated with Gambogic Amide. Graph indicates degree of dystrophy. Photomicrograph examples of one representative hair follicle per group are shown on the right as derived from binocular microscopy of cultured hair follicles as well as hematoxylin&eosin routine staining. A blow-up image of the pigmentary-unit just above the dermal papilla is shown in each micrograph. Bars = 15 μm. D: Macroscopic analysis of hair cycle progression in organ culture. Photomicrograph examples of one representative hair follicle per group routinely stained with hematoxylin&eosin are shown on the right. Note the decreasing diameter of the hair follicle bulb and keratinocyte population in the hair follicle matrix on both sides of the dermal papilla with hair cycle progression in hair follicles treated with 1000 nM Gambogic Amide. Hair follicles treated with lower concentrations of Gambogic Amide kept their anagen-like appearance. Bars = 50 μm. E: Immunohistochemical quantification of melanocytes with p16, a marker for mature and senescent melanocytes. Melanocytes are labelled green, p16-immunoreactive cells are labelled red. White boxes indicate origin of high magnification blow-ups. Bars = 10 μm.