effect of removal of spermatogonial stem cells (sscs) from in vitro culture on gene expression of niche factors in bovine

background: niche cells, regulating spermatogonial stem cells (sscs) fate are believed to have a reciprocal communication with sscs. the present study was conducted to evaluate the effect of ssc elimination on the gene expression of glial cell line-derived neurotrophic factor (gdnf), fibroblast growth factor 2 (fgf2) and kit ligand (kitlg), which are the main growth factors regulating sscs development and secreted by niche cells, primarily sertoli cells. methods: following isolation, bovine testicular cells were cultured for 12 days on extracellular matrix-coated plates. in the germ cell-removed group, the sscs were removed from the in vitro culture using differential plating; however, in the control group, no intervention in the culture was performed. colony formation of sscs was evaluated using an inverted microscope. the gene expression of growth factors and spermatogonia markers were assessed using quantitative real time pcr. results: sscs colonies were developed in the control group but they were rarely observed in the germ cell-removed group; moreover, the expression of spermatogonia markers was detected in the control group while it was not observed in the germ cell-removed group, substantiating the success of sscs removal. the expression of gdnf and fgf2 was greater in the germ cell-removed than control group (p<0.05), whereas the expression of kitlg was lower in the germ cell-removed than control group (p<0.05). conclusion: in conclusion, the results revealed that niche cells respond to sscs removal by upregulation of gdnf and fgf2, and downregulation of kitlg in order to stimulate self-renewal and arrest differentiation.