ABSTRACT
The preservation of spermatogenesis throughout a man’s adult reproductive life depends on one cell type only: the adult testicular stem cell. Testicular stem cells are undifferentiated cells that give rise to the spermatogenic cells and, finally, the spermatozoa. Even though there is a continual loss of differentiated cells, the spermatogenic cell lineage maintains its cell number thanks to the adult testicular stem cells, which produce both new stem cells (self-renewal) and differentiating cells.
