Effect of thyroxine, cortisol and epidermal growth factor on fibre growth in vitro

Abstract

Pr-oc. Am-t. Sot. Atzim. Prod. I994 Vol. 20 EFFECT OF THYROXINE, CORTISOL AND EPIDERMAL GROWTH FACTOR ON FIBRE GROWTH IN VITRO P.I. HYND, F.A. SIMMS and H. ANSARI-RENANI Dept of Animal Science, University of Adelaide, Waite Campus, Glen Osmond S.A. 5064 The recent development of a wool follicle culture system (Hynd et al. 1992) now allows us to determine the direct effects of hormones and growth factors on follicle function. The effects of thyroxine (T,), triiodothyronine (T;), and cortisol, which are known to have large effects on fibre growth when manipulated systemically, were examined using the in vitro system. The opportunity was also taken to examine the effects of very low concentrations of epidermal growth factor (EGF) on fibre growth. Follicles (n = 12/treatment) were dissected from thin strips of skin taken from Tukidale sheep and cultured in 500 ,uL of Williams E media in individual wells. Hormone or growth factor was added daily to the cultures in 20 PL of media for a period of 4 days. Follicle length was measured daily by image analysis at 100x magnification. Fibre growth rate was estimated as the slope of the regression of follicle length on time. The treatments were: Control, T3 (5 ng/mL), or T, (100 ng/mL) in media supplemented with 5% fetal calf serum (FCS) or zero FCS; Cortisol at 0, 10, 50 or 1000 ng/mL; and EGF at 0, 0.125, 0.25, 1.0, 25.0 and 50.0 ng/mL. Neither T; nor T, had any significant effect on fibre growth in vitro (Table 1). Addition of 5% FCS also had no significant effect although there was a tendency for FCS-treated follicles to grow slightly (18%) faster (P = 0.10) than follicles incubated in zero FCS. There was no significant interaction between FCS and thyroid hormone response (P = 0.69). Cortisol likewise had no significant effect on fibre growth (399 t 57, 440 + 57, 446 ? 54 and 367 5 52 pm/day (P = 0.72) for the 0, 10, 50, and 100 ng/mL treatments respectively). The EGF at concentrations greater than 0.25 ng/mL significantly (P = 0.009) reduced fibre growth (Table 2). Table 1. Mean (5 se) effects of T, and T, on fibre growth &m/day) in vitro with and without foetal calf serum (FCS) Table 2. Mean (k se) effect of epidermal growth factor (EGF) dose on fibre growth @m/day) in vitro The inhibitory effects of EGF confirm previous findings but the lack of effect of the thyroid hormones and cortisol was unexpected. It appears these hormones do not act directly on the follicle. HYND, PI., WINDER, L.M., JAHODA, C.A.B. and BICKERSTAFFE, R. (1992). Wool Tec~hml. and Sheep Breed. 40: 102-5. 460