Pluripotent Stem Cells from Testis

1.1 Importance of Spermatogonial Stem Cells (SSCs) Spermatogonial stem cells (SSCs) are undifferentiated germ cells that balance self-renewing and differentiating divisions to maintain spermatogenesis throughout adult life. This is a productive stem cell system that produces millions of spermatozoa each day while also maintaining rigorous quality control to safeguard germline integrity. SSCs are the only adult stem cells that are capable of self renewal and that differentiate to produce haploid cells transmitting genes to next generation. In the recent years, derivation of multipotent embryonic stem (ES)-like cells, which are capable of differentiating to three germinal layers, from SSCs in the testis, has been reported. This is of immense importance in medicine, basic science and animal reproduction and overcomes ethical issues pertaining to the use of human embryos for research. Since the population of SSCs in the testis is very low (< 1%), the identification of markers that are specifically expressed in SSCs aids in their efficient isolation. The characteristics of SSCs and ES-like cells in culture, and differential expression of genes in both these cell types can provide better understanding. In the present chapter, we would describe and compare the expression of SSC-specific markers in vivo and in vitro. We will also review the in vitro culture conditions of SSCs and characteristics of ES-like cells that differentiate from SSCs. This would enhance our perceptive of these special cells that has opened new avenues for stem cell researchers.