Wool follicles initiate, develop and produce wool fibres in ovine fetal skin grafts

Abstract

S U M M A R YResearch into the mechanisms that control the initiation and development of wool follicles has been severely hampered by the inaccessibility of fetal skin in utero. The aims of this study were to determine whether ovine fetal skin, when grafted onto the athymic nude mouse (nu/nu), could be maintained outside the uterine environment and, if so, whether it would retain its ability to initiate and develop wool follicles capable of producing wool fibres.Skin was removed from the mid-side region of ovine fetuses on days 45, 55, 65, 75, 85 and 95 of gestation, and transferred to graft beds prepared on anaesthetized nude mice. After developing for 20 days on the recipients, the grafts were excised for histological examination. Control ovine fetal skin was also obtained at the above times and from fetuses on days 105 and 115, and similarly processed for histological examination.Fetal skin at all ages was successfully grafted onto nude mice; 90 % of all grafts were accepted and maintained by the recipients. Follicle initiation and/or development occurred in all grafts, including those formed from day 45 fetal skin, collected and grafted prior to follicle initiation in vivo. The number of follicles in grafted skin was reduced compared to that in control fetal skin of equivalent age; however, follicle development was generally accelerated. Follicle initiation and development occurred predominantly in the peripheral zone of the grafts. Some of the follicles present in the skin at grafting were lost due to the grafting procedure, while others continued to develop and produce wool fibres. Follicle development varied considerably between grafts. All grafted skin exhibited premature loss of the periderm layer and cornification of the epidermis, probably in response to the exposure of the skin surface to the atmosphere. There was a notable absence of both arrector pili muscles and sweat glands associated with graft follicles, and a retardation of sebaceous gland development.The grafting technique developed in this study has enabled ovine fetal skin to be maintained outside the uterine environment for extended periods of time and may provide an improved means for future investigation of wool follicle initiation and development.hampered by the inaccessibility of the fetus and thusThe initiation (beginning of development) of wool Some attempts have been made to maintain ovine follicles and most of their subsequent development fetal skin outside the uterine environment. Hickman occurs prior to birth in the ovine fetus (Hardy & Lyne et al. (1962) and Rudall & Wickham (1965) surgically 1956a. Although many factors have been identified removed skin from fetuses in vivo, stored the skin at a which influence follicle initiation and development sub-zero temperature and then grafted the skin back during this period (Corbett 1979), the precise mechan-onto the respective donor lambs after birth. Although isms that control the processes of initiation and grafting was successful, fetal loss due to surgery was development in the f...