Sertoli cells are the unique source of stem cell factor for spermatogenesis.

Several cell types have been proposed to create the microenvironment for spermatogenesis. However, the expression patterns of the key growth factors produced by these somatic cells have not been systematically studied and no such factor has been conditionally deleted from its primary source(s), raising the question of which cell type(s) are the physiological sources of these growth factors. Here, using single-cell RNA sequencing and a series of fluorescent reporter mice, we found that, Stem cell factor (Scf), one of the essential growth factors for spermatogenesis, was broadly expressed in testicular stromal cells, including Sertoli, endothelial, Leydig, smooth muscle cells and Tcf21-CreER+ stromal cells. Both undifferentiated and differentiating spermatogonia were associated with SCF-expressing Sertoli cells in the seminiferous tubule. Conditional deletion of Scf from Sertoli cells, but not any other SCF-expressing cells, blocked the differentiation of spermatogonia, leading to complete male infertility. Conditional overexpression of Scf in Sertoli cells, but not endothelial cells, significantly increased spermatogenesis. Our data revealed the importance of anatomical localization for Sertoli cells in regulating spermatogenesis. Sertoli cells are the unique source of SCF that is essential for spermatogenesis.