Spermatogonial Stem Cell Technology and Regenerative Medicine

Germ cell development begins with the characteristics of the primordial germ cells (PGCs) early in human fetal life. PGCs arise from the proximal epiblast and will replace to the extra embryonic mesoderm during the fourth and fifth week of embryonic development. By the finish of the fifth week to early sixth week, PGCs will embark for a second immigration via the dorsal mesenterium of the gut to the gonadal ridge. During their immigration, PGCs proliferate but once they has arrived the gonadal ridge, they enter into a mitotic arrest while differentiating into gonocytes. Shortly after birth these gonocytes put on the basal membrane of the seminiferous tubules where mitosis is reinitiated. From then on, they are called spermatogonial stem cells or SSCs [1]. Spermatogonial stem cells (SSCs) are a subpopulation of unspecialized stem cells that lie along the basement membrane of the seminiferous tubules of the testis and give rise to the germ line lineage in males. In the adult testis, only 0.03% of all germ cells are spermatogonial stem cells [2]. Testicular SSCs are typically unipotent and are only capable of giving rise to the germ cell lineage and ultimately spermatozoa.