LEUKEMIA INHIBITORY FACTOR AND CILIARY NEUROTROPIC FACTOR PROMOTE THESURVIVAL OF SERTOLI CELLS AND GONOCYTES IN A COCULTURE SYSTEM

Leukemia inhibitory factor (LIF) and ciliary neurotropic factor (CNTF) were found to be pleiotropic modulators of Sertoli cell and gonocyte development (both isolated from the neonatal rat testis) in a cocultur e system, whereas IL-6, another member of this cytokine family, had no effect on these cells. LIF and CNTF significantly enhanced the surviv al of the Sertoli cells in a dose- and time-dependent manner. The effe ct of LIF on the Sertoli cells was significant at a concentration of 1 ng/ml after 3 or 6 days of culture, whereas CNTF had a significant ef fect at 10 ng/ml. Neither LIF nor CNTF had an effect on Sertoli cell p roliferation. The survival of proliferating gonocytes (isolated from 5 -day-old rats testes) was also significantly higher in cultures to whi ch LIF (7.5 ng/ml) or CNTF (10 ng/ml) was added. No effect of these cy tokines was found on the mitotic activity of proliferating gonocytes. However, LIF (7.5 ng/ml) stimulated the proliferation of quiescent gon ocytes (isolated from day 1 testes) after 3 days of culture. Combinati ons of LIF (or CNTF) with fibroblast growth factor 2 (10 ng/ml) and st eel factor (50 ng/ml) did not further improve the long term culture of the gonocytes. LIF- and CNTF-like proteins of the expected molecular masses (32,000 and 22,000 daltons, respectively, under reducing condit ions) were found by Western blotting in testicular extracts of 3-day-o ld rats. Taken together, these results indicate that LIF or CNTF may p lay a role at the start of the spermatogenesis. The characterization o f receptors for LIF or CNTF on the gonocytes and/or neonatal Sertoli c ells will aid in a better understanding of the physiological role of t hese cytokines in the reproductive system.