Transforming Growth Factor-β2 Mediates Mesenchymal-Epithelial Interactions of Testicular Somatic Cells*†

Abstract

Transforming growth factor-β2 (TGFβ2) is an important mediator of growth and differentiation. We here describe for the first time the complete sequence of the TGFβ2 complementary DNA derived from peritubular myoid cells of the rat testis. The size of the rat TGFβ2 complementary DNA was 1245 bp, and the deduced protein sequence contained 414 amino acids. Sequence comparison with the human and mouse amino acid sequences demonstrated 96.4% and 97.9% sequence identities, respectively. To elucidate the functional role of TGFβ2 in testicular somatic cells, we studied its secretion in vitro in monocultures and cocultures of mesenchymal peritubular and epithelial Sertoli cells. The highest amounts of TGFβ2 protein were secreted in the cocultures and by peritubular cells, whereas Sertoli cells secreted only minor amounts. Stimulation experiments with FSH revealed a reduced secretion of TGFβ2 in cocultures, probably mediated by a paracrine interaction of the FSH-responsive Sertoli cells. In contrast, TGFβ2 secretion by peritubular cells was increased after stimulation with glucocorticoids and after addition of recombinant TGFβ2, indicating an autoregulation of TGFβ2. Furthermore, application of recombinant TGFβ2 to cocultures resulted in an enhanced aggregation and cell clustering of Sertoli cells, pointing to an important role of TGFβ2 in the paracrine interaction of peritubular and Sertoli cells of the developing rat testis.