Cellular activity in the dermis surrounding the hair bulb in alopecia areata.

The metabolic activity of the cells in the connective tissue surrounding the hair bulb has been studied by radioautography in alopecia areata and in normal scalp, using in vitro incorporation of tritiated thymidine, uridine, histidine, leucine and proline. In alopecia areata, the hair bulbs are blocked in the anagen IV stage and DNA, RNA and protein synthesis are restrained. Cells in the papilla, as well as the cellular infiltrate, display a very low rate of metabolic activity. During regrowth in alopecia areata, the activity of endothelial cells is increased in the papillary and peribulbar layers before DNA, RNA and protein synthesis are restored in the epithelial cells of the hair bulb. The dermal and epithelial labelling patterns eventually reach levels comparable to those observed in an induced anagen IV state of a normal scalp. It is concluded that the progression from anagen IV to a further stage represents a critical period in the growth of hair that would closely depend upon an adequate metabolic function of the connective tissue. It is impaired in alopecia areata.