EVIDENCE THAT BASEMENT-MEMBRANE PREVENTS APOPTOSIS OF SERTOLI CELLS IN-VITRO IN THE ABSENCE OF KNOWN REGULATORS OF SERTOLI-CELL FUNCTION

Although the role of basement membrane in the morphological and functional differentiation of Sertoli cells has been well characterized, very little is known about its involvement in Sertoli cell survival and maintenance throughout life. When cultured on laminin or Matrigel, 80-90% of Sertoli cells retained their viability. Sertoli cells prevented from attachment and basement membrane deposition by plating on plastic surfaces coated with polyhydroxyethylmethacrylate (poly-HEMA) exhibited a loss of viability by approximately 50% within 24 h. Addition of soluble laminin did not prevent the loss of viability of Sertoli cells, whereas soluble Matrigel enhanced the survival significantly when added at a concentration of 100 mu g/ml or more. The addition of FSH, epidermal growth factor, testosterone, retinoic acid, or a mixture of insulin, transferrin, and selenium had no significant effect on the viability of Sertoli cells cultured on polyHEMA for up to 72 h. When all of these hormones and factors were added together, a significantly higher percentage of cell survival was observed at 24, 48, and 72 h, but the percent survival was significantly lower than that seen on either laminin or Matrigel. The nature of cell death occurring in the Sertoli cells plated on polyHEMA was determined by agarose gel analysis that revealed a ladder of similar to 200-base pair DNA multiple fragments. Flow cytometric analysis of propidium iodide-stained cells indicated that most of the cells were apoptotic. Freshly isolated Sertoli cells and adherent cells on basement membrane did not show internucleosomal DNA breakdown or an apoptotic peak in the flow cytometric analysis. These results suggest that basement membrane plays a crucial role in Sertoli cell survival in vitro when it is used as a solid substratum for culture, and in the absence of basement membrane, FSH and other regulators of Sertoli cell function cannot prevent Sertoli cell apoptosis.