Actions of Extracellular Matrix on Sertoli Cell Morphology and Function1

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Abstract
Sertoli cells were isolated and cultured in the absence or presence of extracellular matrix (ECM) to determine whether ECM may influence Sertoli cell function on a molecular level. As previously described, a morphological analysis of the cells indicated that ECM allows the expression of a columnar histotype and the formation of junctional complexes. The combined actions of ECM and hormones were found to have a profound effect in promoting the expression of a polarized Sertoli cell morphology. In our investigation of the effects of ECM on Sertoli cells, we used transferrin and androgen-binding protein (ABP) production as biochemical markers of Sertoli cell function. The presence of ECM was found to cause a 25% increase in the basal level of transferrin production; however, ECM had no effect on the basal level of ABP production by Sertoli cells. Regulatory agents such as follicle-stimulating hormone (FSH) and a combination of FSH, insulin, retinol, and testosterone stimulated the production of both transferrin and ABP. The ability of hormones to stimulate these Sertoli cell functions was not influenced by the presence of ECM. Similar results were obtained with 2 .mu.m- or 50-.mu.m-thick ECM and with a seminiferous tubule biomatrix preparation. ECM was found to increase the maintenance of long-term Sertoli cell cultures; however, the decline in Sertoli cell functional integrity, which occurs during cell culture, was not affected by the presence of ECM. An additional functional parameter examined was the radiolabeled proteins secreted by Sertoli cells. ECM did not promote the production or affect the electrophorectic profile of Sertoli cell-secreted proteins under basal or hormonally stimulated conditions. Combined results indicated that although ECM allowed the expression of a normal Sertoli cell histotype, ECM had no major effects on the Sertoli cell functions analyzed nor on the hormonal regulation of these functions. The inability of ECM to affect Sertoli cell function on a molecular level is discussed with regard to environmental as opposed to regulatory cellular interactions. Our observations imply that dramatic effects of ECM on cell morphology do not necessarily correlate to subsequent effects on cellular function.