IN-VIVO EFFECTS OF EPIDERMAL GROWTH-FACTOR ON EPIDERMAL PATTERN-FORMATION AND HAIR FOLLICLE INITIATION IN THE MARSUPIAL BANDICOOT ISOODON MACROURUS

The extrauterine development of marsupial pouch young (northern brown bandicoot Isoodon macrourus) has facilitated the study of the effects of murine epidermal growth factor (mEGF) on pattern formation in skin. Hair follicle initiation and development, which in the mouse would oc cur from about Days 13-14 of gestation onward, occurs postnatally. In the present study the effect in vivo of mEGF on developing skin corres ponding to mouse gestational ages from Day 13 onward was examined. Sub cutaneous injections of mEGF (0.5, 1.0 and 2.0 mu g g(-1) body weight) or equivalent volumes of saline (0.9% w/w) were administered daily, b efore and during hair follicle initiation and development. Murine EGF inhibited the formation of hair follicles, hair follicle sweat glands, sebaceous glands and dermal papillae. The pattern of follicle initiat ion was perturbed. The characteristic trio follicle grouping was absen t, and follicle rudiment densities (no. per mm(2) skin surface) were s ignificantly lower in animals treated with mEGE whereas follicle diame ters were increased. These data may reflect a role for the epidermal g rowth factor (EGF) receptor in epidermal pattern formation. The EGF re ceptor and its potential ligands (such as EGF, transforming growth fac tor (TGF-alpha) or other yet-to-be-discovered ligands) perhaps act as parts of a pattern-forming system in vertebrate skin.