Migration and Keratinization of Cells in Wool Follicles

Abstract

. .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.The specific activity of tritium in fibres plucked from the same sheep at intervals after the intravenous injection of [3Hjthymidine was determined by scintillation counting and assessed in terms of cell migration and hardening of the fibres. The time at which the specific activity of solventdegreased fibres reached a maximum was found to give an estimate of the time for cells in the fibre to migrate to the upper limit of the keratogenous zone. When the plucked fibres were extracted with 8 M urea the times of the maximum specific activities of the urea-dispersible and urea-insoluble material provided respectively estimates of the times at which hardening of the fibres began and ended.The effects of different planes of nutrition were examined in two other Merino sheep by radioassay· of fibres plucked after intravenous injections of [3Hjthymidine given after an equilibration period of at least 2 months on each level of feeding. A high plane of nutrition increased the rate of cell migration and hastened the onset of hardening of the fibres, but prolonged the hardening process. The prolongation of the hardening process was confirmed by the specific activities of fibres plucked after intravenous inje,<tions of [3 5 Sjcystine.

Plasma concentrations and urinary excretion of mouse epidermal growth factor associated with the inhibition of food consumption and of wool growth in Merino wethers

“…Proliferative activity in bulbar matrix cells which sustains wool growth (Chapman, Downes & Wilson, 1980) was clearly disrupted and wool fibres shed when more than 2 mg mEGF was given s.c. for the times described here, and where plasma concentrations in the range 30-120ng/ml (0-5-2 10~8mol/l) were maintained for several hours. The i.v.…”

Basonuclin as a cell marker in the formation and cycling of the murine hair follicle

“…Throughout the hair cycle, the cell population possessing nuclear basonuclin includes cells with the ability to multiply [2,3,5,10,32,44,48]. In their capacity to [6,13,14,20,23,[28][29][30]42], the basal cells of the follicle resemble the basal keratinocytes of the epidermis.…”

Expression of keratin K14 in the epidermis and hair follicle: insights into complex programs of differentiation.

“…In contrast, cells of the upper portion of the ORS migrate predominantly inwards as they differentiate. Moreover, pH]thymidine labeling of sheep follicles has indicated that cells in the upper portion of the follicle seem to be less active mitotically (Chapman et al, 1980). Despite these differences, both populations of mitotically active ORS cells seem to have the capacity to regenerate epidermis during wound-healing.…”

“…Most of the ORS originates from one to two layers of cells on the surface of the mid-region of the hair bulb (Birbeck and Mercer, 1957;Pinkus, 1958;Hashimoto and Shibazaki, 1975;Montagna, 1976;Ito et al, 1986). At the beginning of each hair cycle, these progenitor ORS cells divide rapidly and give rise to a population of self-propagating cells that extend along the outer surface of the ORS to approximately half way up the follicle (Bullough and Laurence, 1958;Chapman et al, 1980;Clausen et al, 1982). ORS cells in this lower region seem to migrate both upwards and inwards as they differentiate.…”