Migration and Keratinization of Cells in Wool Follicles

Migration of' cells in wool follicles of an adult Merino sheep was studied autoradiographically in skin samples taken at intervals after an intravenous injection of [3Hjthymidine. Fibre arid inner root sheath cells incorporated [3Hjthymidine in a cone-shaped region of the follicle bulb. Labelled inner sheath cells migrated out of the bulb ahead of contemporaneous cells in the fibre and remained in advance, although to a progressively lesser extent, until the inner sheath cells sloughed into the follicle lumen. Outer root sheath cells incorporated [3Hjthymidine along the length of the follicle. Cells in the proximal half of the outer sheath migrated inwards and distally and sloughed into the follicle lumen before contemporaneous inner sheath cells. Other cells in the distal half of the outer sheath migrated past the level where cells from the proximal population were shed and also sloughed into the lumen. In the most distal part of the outer sheath, which formed the epidermis-like lining of the follicle canal, little migration of cells was observed during 8 days of observation.