Function of stem cell factor as a survival factor of spermatogonia and localization of messenger ribonucleic acid in the rat seminiferous epithelium

To address the possibility that stem cell factor (SCF) is a paracrine regul ator of germ cell development in the adult rat testis, stage-specific distr ibution of SCF messenger RNA (mRNA) was investigated with Northern blot and in situ hybridization analyses. The highest levels of SCF mRNA were found in stages II-VI of the rat seminiferous epithelial cycle, whereas the lowes t levels were in stages VII-VIII. Intermediate levels of SCF mRNA were dete cted in stages IX-XIV-I of the cycle. The expression of the SCF gene was fo und to be developmentally regulated, and the expression pattern followed th e process of Sertoli cell proliferation and differentiation during postnata l life. The effect of mouse recombinant SCF on spermatogonial DNA synthesis was studied using an in vitro tissue culture system for stage-defined semi niferous tubules. A significant increase in DNA synthesis in spermatogonia could be detected when tubule segments from stage XII were cultured in the presence of 100 ng/ml SCF for 48 h (P < 0.05) and 72 h (P < 0.01). This obs ervation was further confirmed with autoradiographic analyses; almost a 100 -fold increase in thymidine incorporation in the SCF-treated (100 ng/ml) tu bule segments was observed compared with that in untreated samples. The res ults of the present study suggest that SCF is a Sertoli cell-produced parac rine regulator and acts as a survival factor for spermatogonia in the adult rat seminiferous epithelium in a stage-specific manner.