Is the adult sertoli cell terminally differentiated?

New data have challenged the convention that the adult Sertoli cell population is fixed and unmodifiable. The Sertoli cell has two distinct functions: 1) formation of the seminiferous cords and 2) provision of nutritional and structural support to developing germ cells. For these to occur successfully, Sertoli cells must undergo many maturational changes between fetal and adult life, the main switches occurring around puberty, including the loss of proliferative activity and the formation of the blood-testis barrier. Follicle-stimulating hormone plays a key role in promoting Sertoli cell proliferation, while thyroid hormone inhibits proliferative activity in early postnatal life. Together these regulate the Sertoli-germ cell complement and sperm output in adulthood. By puberty, the Sertoli cell population is considered to be stable and unmodifiable by hormones. But there is mounting evidence that the size of the adult Sertoli cell population and its maturational status is modifiable by hormones and that Sertoli cells can gain proliferative ability in the spermatogenically disrupted hamster and human model. This new information demonstrates that the adult Sertoli cell population, at least in the settings of testicular regression in the hamster and impaired fertility in humans in vivo and from mice and men in vitro, is not a terminally differentiated population. Data from the hamster now show that the adult Sertoli cell population size is regulated by hormones. This creates exciting prospects for basic and clinical research in testis biology. The potential to replenish an adult Sertoli-germ cell complement to normal in a setting of infertility may now be realized.     

Development of sertoli cell junctions in vitro—A freeze-fracture study

Summary Seminiferous tubules of 1-day-old rats were maintained in organ culture for up to 40 days. Five classes of intercellular junctions between Sertoli cells were observed by the freeze-fracture method as the tissue aged: (a) typical gap junctions; (b) focal tight junctions; (c) macular tight junctions; (d) meandering tight junctions; and (e) extensive tight junctions. The relative proportions of these types of Sertoli cell junctions were quantitated as the organ cultures progressed. The junctional structures observed and classified in organ culture were identical to those seen in vivo, but the timing of their appearance and/or disappearance, as well as their relative proportions, was different from that observed in the developing animal. Extensive tight junctions, with numerous parallel strands, were observed in the 40-day cultures; however, their oblique orientation with respect to the myoid layer was in contrast to the parallel orientation observed in vivo. This study was supported by Grant 801D185 (Dr. Posalaky) from the Medical Education and Research Foundation, St. Paul-Ramsey Hospital.