Function of Stem Cell Factor as a Survival Factor of Spermatogonia and Localization of Messenger Ribonucleic Acid in the Rat Seminiferous Epithelium¹

Abstract

To address the possibility that stem cell factor (SCF) is a paracrine regulator of germ cell development in the adult rat testis, stage-specific distribution 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 lowest levels were in stages VII-VIII. Intermediate levels of SCF mRNA were detected in stages IX-XIV-I of the cycle. The expression of the SCF gene was found to be developmentally regulated, and the expression pattern followed the process of Sertoli cell proliferation and differentiation during postnatal life. The effect of mouse recombinant SCF on spermatogonial DNA synthesis was studied using an in vitro tissue culture system for stage-defined seminiferous 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 observation was further confirmed with autoradiographic analyses; almost a 100-fold increase in thymidine incorporation in the SCF-treated (100 ng/ml) tubule segments was observed compared with that in untreated samples. The results of the present study suggest that SCF is a Sertoli cell-produced paracrine regulator and acts as a survival factor for spermatogonia in the adult rat seminiferous epithelium in a stage-specific manner.

Signaling through Extracellular Signal-regulated Kinase Is Required for Spermatogonial Proliferative Response to Stem Cell Factor

“…Pathways-It has been proposed that SCF acts as a survival factor that prevents apoptosis in differentiating spermatogonia (13,19,34). In line with this we observed that during the 24 h of culture, concomitantly with the increase of the metaphase counts, SCF decreased the frequency of cells showing morphologies typical of apoptosis (Fig.…”

“…It has been proposed that SCF acts merely as a survival factor that prevents apoptosis in differentiating spermatogonia, which are assumed to be intrinsically committed to proliferate (13,19,34). We actually found that SCF addition also partially inhibits apoptosis occurring in germ cells from 8-dayold mice after 24 h of culture.…”

“…A loss of spermatogonia during postnatal development is also observed in a peculiar Steel mutation, Sl 17H (3). Finally, in vitro addition of SCF, which is expressed by Sertoli cells (16 -17) under FSH control (17)(18), selectively stimulates DNA synthesis in type A but not in type B spermatogonia (17,19).…”

Differential expression and regulation of the retinoblastoma family of proteins during testicular development and spermatogenesis: roles in the control of germ cell proliferation, differentiation and apoptosis

“…Expression levels and phosphorylation status of pocket proteins in the cultured seminiferous tubules in the presence or absence of SCF When the seminiferous tubules from stage XII of the epithelial cycle were cultured in the presence of SCF (100 ng/ml), the [ 3 H]-thymidine uptake was signi®-cantly elevated after 48 and 72 h culture in vitro in comparison to the controls (Hakovirta et al, 1999). Moreover, in the absence of SCF, the number of apoptotic germ cells was much higher than in the presence of stem cell factor during 8 ± 72 h culture (Yan et al, 2000c).…”

“…Stem cell factor enhances pRb expression and phosphorylation in vitro and blockade of SCF/c-kit interaction in vivo suppresses levels and phosphorylation of pRb: correlation with spermatogonial proliferation and apoptosis It is known that in the presence of stem cell factor (SCF) [ 3 H]-thymidine incorporation of the seminiferous tubules from stage XII was enhanced and apoptosis was suppressed signi®cantly after 48 ± 72 h culture in vitro in comparison to controls (Hakovirta et al, 1999). Recent studies also show that in the presence of SCF both mitotic and meiotic DNA synthesis of germ cells could be maintained in vitro for at least 72 h and germ cells could pass through meiosis and further dierentiate into spermatids (Vincent et al, 1998).…”