Introduction to spermatogenesis

The testis is the primary organ involved in male germ cell production. It is under the control of the hypothalamus, which regulates the secretion of the pituitary gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH). The testis is composed of numerous thin, tightly coiled ducts known as the seminiferous tubules, which comprise about 90 percent of the testicular mass. The main cell types in the testis are Leydig cells, Sertoli cells, and germ cells. The Leydig cells are located outside the walls of the seminiferous tubules and, in response to LH stimulation, produce steroid hormones. These steroid hormones in conjunction with FSH regulate the Sertoli cells, which form a blood-testis barrier through formation of tight junctions. The Sertoli cells, which are often referred to as “nurse cells”, are regularly distributed within the walls of the seminiferous tubules and provide an environment for germ cells to develop and mature through the production of survival factors. One factor that mediates the survival and differentiation of germ cells is Stem Cell Factor (SCF), also called Kit-ligand (Packer et al., 1995). The Sertoli cells also help transport young germ cells from the periphery of the seminiferous tubule to the lumen (Griswold, 1995).