Local regulation of spermatogenesis: a living cell approach.

The normal function of the testis is dependent on stimulation by pituitary gonadotrophins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Targets for these hormones are Leydig cells in the interstitial tissue, and Sertoli cells in the seminiferous epithelium, respectively. The effect of LH on the seminiferous epithelium is mediated by testosterone produced by the Leydig cells. Therefore, the two main hormones that influence the function of the seminiferous epithelium directly are FSH and testosterone. The preferential action of FSH in the adult seminiferous epithelium is associated with stages that involve meiotic divisions and early spermiogenesis. The parameters related to androgen action predominate at different stages during which the final maturation of the spermatids, spermiation and the onset of meiosis take place. The stage-dependent variation of the hormone responses in the seminiferous epithelium indicates the presence of local paracrine regulation and cell interaction mechanisms in the seminiferous epithelium, which are dependent on the spermatogenic cells associated with the Sertoli cells. Several growth factors have been suggested as mediators of this interaction. Owing to its highly complex structure, the seminiferous epithelium has been a difficult area for biochemical studies. New in vitro techniques have made these studies possible, and particular advances have been made using recombinant DNA techniques and transgene technology.