INCREASE IN DERMAL PAPILLA CELLS BY PROLIFERATION DURING DEVELOPMENT OF THE PRIMARY WOOL FOLLICLE

The growth of the demand condensate and dermal papilla of developing primary wool follicles was investigated by counting cells in paraffin of foetal sheep skin. The number of cells in the dermal condensate of prepapilla was found to increase approximately two-fold between follicle initiation and maturation (stages F1 and F8). This increase was not continuous but was interrupted by a no growth period from stages F2a to F6. The proportion of dividing dermal condensate cells, determined by the BrdU/Anti-BrdU technique, was shown to peak during periods of cell number increase. In addition, we were able to demonstrate that the increase in cell number described above could be accounted for entirely by cell proliferation, with no contribution from migration. The developmental modulation of dermal condensate cell proliferation is discussed in relation to both the Reaction-Diffusion theory of hair follicle initiation and morphogenesis and our current knowledge of the transforming growth factor-beta superfamily of proteins.