Leukemia inhibitory factor and ciliary neurotropic factor promote the survival 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 coculture system, whereas IL-6, another member of this cytokine family, had no effect on these cells. LIF and CNTF significantly enhanced the survival of the Sertoli cells in a dose- and time-dependent manner. The effect 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 effect at 10 ng/ml. Neither LIF nor CNTF had an effect on Sertoli cell proliferation. The survival of proliferating gonocytes (isolated from 5-day-old rats testes) was also significantly higher in cultures to which LIF (7.5 ng/ml) or CNTF (10 ng/ml) was added. No effect of these cytokines was found on the mitotic activity of proliferating gonocytes. However, LIF (7.5 ng/ml) stimulated the proliferation of quiescent gonocytes (isolated from day 1 testes) after 3 days of culture. Combinations of LIF (or CNTF) with fibroblast growth factor 2 (10 ng/ml) and steel 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 conditions) were found by Western blotting in testicular extracts of 3-day-old rats. Taken together, these results indicate that LIF or CNTF may play a role at the start of the spermatogenesis. The characterization of receptors for LIF or CNTF on the gonocytes and/or neonatal Sertoli cells will aid in a better understanding of the physiological role of these cytokines in the reproductive system.