DISTRIBUTION OF ACIDIC AND BASIC FIBROBLAST GROWTH-FACTORS IN OVINE SKIN DURING FOLLICLE MORPHOGENESIS

Acidic and basic fibroblast growth factors (aFGF and bFGF) have been l ocalized by immunochemistry in ovine skin during wool follicle morphog enesis. At 40 days of gestation, prior to the appearance of follicle p rimordia, bFGF immunoreactivity was detected in the intermediate and p eriderm layers of the epidermis and at the dermal-epidermal junction. Antibodies to aFGF did not bind to skin at this age. During early foll icle formation, at 76 days of gestation, both FGFs were found in the e pidermis and associated with the follicle primordia. Antibodies to aFG F, in particular, bound to the basal cells of the epidermis and the fo llicle cell aggregations. With the development of epidermal plugs, bFG F was confined to the intermediate layers of the epidermis and the der mal-epidermal junction, whereas aFGF staining was associated with the cells of the epidermis and the plugs. At 90 days, when many different stages of follicle development were in evidence, immunoreactivity for both FGFs was associated with the cells of the elongating epidermal co lumn, particularly those adjacent to the dermal-epidermal junction. Du ring follicle maturation, bFGF was found in the suprabasal layer of th e epidermis, in the outer root sheath of the follicle and in the basem ent membrane zone surrounding the bulb matrix. Conversely, strong stai ning for aFGF was observed in the epidermis and pilary canal contiguou s with the epidermis, and in cells of the upper bulb matrix of the fol licle in the region of the keratogenous zone. Western blotting of extr acts of mature follicles that had been isolated from the skin showed t he presence of a major aFGF immunoreactive band with an apparent molec ular mass of 27 kDa. The distributions of aFGF and bFGF, particularly around the dermal-epidermal junction during follicle development, demo nstrate that these growth factors may have related functions in local tissue remodelling during follicle morphogenesis. However, in adult sk in, the presence of bFGF adjacent to the proliferative zone of the fol licle suggests its involvement in regulating the mitotic activity in t he follicle bulb. By contrast, the localization of aFGF to the cells o f the upper follicle bulb, in the zone of keratinization, implicates t his growth factor in cellular differentiation.