The effects of exogenous melatonin and prolactin on wool follicle development in ovine foetal skin grafts

Abstract

The fleece of the Merino sheep is composed predominantly of wool fibres grown from secondary wool follicles. This study investigates the effects of melatonin and prolactin on the development of secondarv follicles in grafted ovine foetal skin. Skin from day 85 ovine foetuses was grafted onto nude mice, developed for 40 days and then excised. Mice received either 30 8g prolactin ip mouse-1 day-1 (P), one melatonin implant (Regulin«) sc mouse -1 (M), commencing at grafting or no further treatment (C). Wool follicle density and development were assessed in grafted skin and compared with day 125 control foetal skin. Cuticle structure of graft fibres was also examined and compared with those of day 125 foetuses. Total follicle density and the rate of follicle initiation were reduced in the grafts compared with control foetal skin. Total follicle density did not vary significantly between treatments, but the number of derived secondary follicles was greater in grafts from mice receiving prolactin (group P). Follicles in grafted skin were larger, produced medullated fibres, and were not grouped, in comparison with follicles in the control foetal skin. Epidermal thickness was greater in grafts than in control foetal skin. The cuticle structure of graft fibres from all groups was similar to the control wool fibres. These findings indicate that prolactin, but not melatonin, may be involved in the regulation of derived secondary follicle development.