Activation of the GFRa1/NCAM pathway stimulates Sertoli cell proliferation in vitro

The proliferation and final density of Sertoli cells in the testis are regulated by hormones and local growth factors. Glial cell line-derived neurotrophic factor (GDNF), a distantly related member of the transforming growth factor-P (TGF-(a) over cap) Superfamily, and its receptor components: GFR alpha 1, Ret and neural cell adhesion molecule (NCAM) have been recently reported to be expressed in the testis and to be involved in the proliferation regulation of immature Sertoli cells. However, the number of the reports is very low, and the signalling pathways have not been well characterized. In the present study, we used purified Sertoli cell cultures from 4- to 5-day-old mouse testis to detect the expression of GDNF, to examine the effect of GDNF on Sertoli cell proliferation and possible signalling pathways mediating such effect. GDNF expression in mouse Sertoli cells was detected at both RNA and protein levels by RT-PCR and immunocytochemistry methods. The expression was up-regulated by FSH. GDNF stimulated the proliferation of Sertoli cells and synergized with FSH to promote the proliferation to a higher level. GFR alpha 1/Ret and GFR alpha 1/ NCAM are two receptor complexes for GDNF. As GFR alpha 1 and NCAM not Ret were expressed in cultured Sertoli cells, we proposed that the stimulatory effect of GDNF on Sertoli cell proliferation was through pathways initiating from the GFR alpha 1/INCAM receptor. This proposition was supported by the fact that the stimulatory effect of GDNF was significantly reduced by anti-NCAM antibody.