Vitamin A modulation of basement membrane production by purified testicular myoid cells

Purified myoid cells, isolated from prepubertal rat testes, cultured in a chemically defined medium for up to I week do not change their metabolic activities, evaluated as protein synthesis and secretion, during the culture time. We report that fibronectin, collagen IV, and laminin are synthesized and secreted by myoid cells as demonstrated by immunocytochemical and biochemical methods. The deposition of all three proteins was spotty, with different regional localizations. The effect of vitamin A on the synthesis and the secretion of the basement membrane components was also evaluated. Retinol supplementation induces a higher synthesis of fibronectin and laminin, whereas it does not change collagen IV synthesis and secretion. The secretion of the other two molecules is differentially regulated by retinol; in fact fibronectin secretion is increased, whereas laminin secretion is reduced. Similar results were obtained utilizing retinoic acid. The data we report in this paper show, for the first time, that purified testicular myoid cells synthesize and secrete fibronectin, collagen IV, and laminin and that synthesis and secretion of these components of the basement membrane are regulated by retinol. These findings reveal a new effect of vitamin A in the regulation of mammalian spermatogenesis.