Abstract
Development of the mammalian testis begins with sex specific differentiation of the bipotential gonad during fetal development, continues after birth with proliferation and differentiation of testicular somatic cells, and culminates at puberty with germ cell differentiation, meiotic divisions and production of sperm that continues throughout the adult life of the male. Recently, it was demonstrated that functional testicular tissue formed de novo when cells isolated from neonatal porcine or rodent testes were grafted ectopically to mouse hosts. The spermatogenic and interstitial compartments of the testis were regenerated form transplanted cells in a cell autonomous fashion and supported the production of functional haploid germ cells. This fascinating ability of testis cells to recreate the necessary structural and cellular associations to support tissue maturation and germ cell differentiation can now be harnessed to study aspects of mammalian spermatogenesis and testicular morphogenesis in an accessible in vivo system.