Expression of peroxisome proliferator activated receptors (PPARs) in humanhair follicles and PPAR alpha involvement in hair growth

Peroxisome proliferator-activated receptors (PPARs), which belong to the nu clear hormone receptor superfamily, have recently been described as potent key regulators of epidermal development. As 1,25-dihydroxyvitamin D-3, reti noic acid and triiodothyronine are known to exert effects on skin and hair follicle growth through similar receptors, we decided to investigate both t he expression pattern of the PPAR alpha, -delta and -gamma subtypes and the ir role in human hair follicles. Using reverse transcriptase-polymerase cha in reaction and immunohistochemistry, we established that PPAR alpha, -delt a and -gamma were expressed in both dermal and epithelial human hair follic le cells. Additionally, we evaluated the dose effect of clofibrate, a PPAR alpha ligand, on the survival of human hair follicles in culture. A benefic ial effect was observed within a narrow range of concentrations.