EFFECTS OF EPIDERMAL GROWTH-FACTOR AND TRANSFORMING GROWTH-FACTOR-ALPHA ON THE FUNCTION OF WOOL FOLLICLES IN CULTURE

The development of a procedure to culture wool follicles from Merino s heep in serum-free conditions has enabled us to investigate the action s of epidermal growth factor (EGF) and transforming growth factor alph a (TGF alpha) on follicle function, including fibre growth, Follicles grown in the absence of growth factors maintained their anagen morphol ogy for 6 days as determined by light microscopy, During this time the y incorporated [H-3]thymidine into the DNA of the bulb matrix and oute r root sheath (ORS) cells and produced fibre keratins as detected by i mmunohistochemistry, In the presence of EGF and TGF alpha, fibre produ ction ceased after 4 days, as it does following the administration of EGF in vivo, Cessation of fibre growth was not accompanied by regressi on of the follicle bulb which occurs in vivo, Follicle length growth d id not differ significantly from controls and cells in the bulb contin ued to proliferate, Usually, the structure of the dermal papillae rese mbled that in control follicles, which was also in marked contrast to changes reported in vivo, In EGF- and TGF alpha-treated follicles, [H- 3]thymidine continued to be incorporated into DNA of the ORS and bulb after fibre growth ceased, Although wool keratin synthesis ceased, cyt okeratins of the epidermis and ORS continued to be produced in the bul b as detected by immunochemistry, These bulb cells were also positive for the periodic acid-Schiff (PAS) reaction indicating the presence of glycogen, a normal component of ORS cells. The observations that cell proliferation continued in the bulb, that glycogen was present and th at soft keratins were expressed in these cells suggest that the bulb c ell population was induced to differentiate into an ORS phenotype by E GF and TGF alpha.