Adult Stem Cells in the Human Testis

Ellen Goossens, PhD, MSc; Herman Tournaye, MD, PhD, MSc


Semin Reprod Med. 2013;31(1):39-48. 

In This Article

Spermatogonial Stem Cell Progenitors Populate the Testes During Fetal Development

Early in fetal development, the extraembryonic ectoderm expresses bone morphogenetic protein 4 and bone morphogenetic protein 8b, two growth factors indispensable for the development of primordial germ cells (PGCs).[1,2] In mice, PGCs are first observed 1 week postcoitum in the embryonal epiblast as a small cluster of alkaline phosphatase-positive cells.[3] During the formation of the allantois, the PGCs passively leave the embryo and start migrating via the hindgut to the genital ridges. During their journey, PGCs are proliferating. Migration, cell proliferation, and survival of PGCs all depend on the Kit-stem cell factor (SCF) system. PGCs, expressing the c-Kit receptor, are attracted by cells, producing SCF all along the migratory path.[4] Approximately 3000 PGCs will colonize the genital ridges.[5] These germ cells differ morphologically from the migratory PGCs and are therefore called gonocytes.[6] These gonocytes become enclosed in testicular cords formed by Sertoli cell precursors and peritubular myoid cells. Initially, gonocytes are located in the center of the testicular cords, away from the basal membrane. In rats and mice, gonocytes proliferate for a few days and then become quiescent in the G0/G1 phase of the cell cycle.[7–9] Shortly after birth, they migrate to the basement membrane and resume their proliferation giving rise to As-spermatogonia or spermatogonial stem cells (SSCs).[10,11]