The Effect of Cortisone on Cell Proliferation and Migration in Peripheral Nerves undergoing Wallerian degeneration

T H E effect of cortisone on the proliferation of tissues other than mesenchymal has received little attention. Bullough (1952) showed that cortisone had a marked effect on the mitotic activity of the epidermis in mice, and Leroy (1952) showed a similar effect on immature testes of rats, but no effect on mature ones. McColl & Weston (1953) have studied the influence of cortisone on the process of Wallerian degeneration in peripheral nerve and noted that there was less total cellularity in degenerated nerves from cortisone-treated animals. It was thought useful to undertake a quantitative study of proliferation during Wallerian degeneration in peripheral nerves from cortisone-treated animals because the normal changes in nuclear population during this process have been intensively investigated (Abercrombie & Johnson, 1946; Thomas, 1948), and it is known that different types of cells multiply at different rates. The examination of the simultaneous action of a given dose of cortisone on these different types of cells should be interesting, particularly as some (the Schwann cells) are of ectodermal origin and others (endothelium and smooth muscle of blood-vessels, and perhaps endoneurial and perineurial connective tissue) are of mesodermal origin. The nerve to the medial head of the gastrocnemius muscle in the rabbit was used. Two aspects of Wallerian degeneration were chosen for study: the increase of population in the degenerating nerve in vivo and the outwandering activity of the cells from the nerve in vitro. While the outwandering of cells in vitro is certainly closely connected with the proliferation of cells within the nerve, it is possible that these two processes may be affected independently by cortisone.