The Sertoli cell as the orchestra conductor of spermatogenesis: spermatogenic cells dance to the tune of testosterone.

Spermatogenesis is contingent upon hormones and growth factors acting through endocrine and paracrine pathways either in vivo or in vitro. Sertoli cells (SCs) furnish essential factors for the successful advancement of spermatogenesis and spermiogenesis. Moreover, receptors for follicle stimulating hormone (FSH) and testosterone, which are the main hormonal regulators of spermatogenesis, are identified on SCs. Testosterone, FSH and luteinizing hormone are known to determine the destiny of germ cells and in their absence germ cells undergo apoptosis. Bcl-2 family proteins determine one signaling pathway which seems to be crucial for the homeostasis of male gametes. In addition to paracrine signals, germ cell development also relies on signals generated by SCs via direct membrane contact. The regulatory peptide somatostatin has an important role in the regulation of the proliferation of the male germ cells. Activin A, follistatin and FSH control germ cell development. In vitro culture systems have provided initial evidence supporting the achievement of the completion of the first and second male meiotic division in vitro. This review article provides an overview of the literature regarding the hormonal pathways governing spermatogenesis and spermiogenesis.