Transforming growth factor-beta 2 mediates mesenchymal-epithelial interactions of testicular somatic cells

Transforming growth factor-beta 2 (TGF beta 2) is an important mediator of growth and differentiation. We here describe for the first time the complet e sequence of the TGF beta 2 complementary DNA derived from peritubular myo id cells of the rat testis. The size of the rat TGF beta 2 complementary DN A was 1245 bp, and the deduced protein sequence contained 414 amino acids. Sequence comparison with the human and mouse amino acid sequences demonstra ted 96.4% and 97.9% sequence identities, respectively. To elucidate the fun ctional role of TGF beta 2 in testicular somatic cells, we studied its secr etion in vitro in monocultures and cocultures of mesenchymal peritubular an d epithelial Sertoli cells. The highest amounts of TGF beta 2 protein were secreted in the cocultures and by peritubular cells, whereas Sertoli cells secreted only minor amounts. Stimulation experiments with FSH revealed a re duced secretion of TGF beta 2 in cocultures, probably mediated by a paracri ne interaction of the FSH-responsive Sertoli cells. In contrast, TGF beta 2 secretion by peritubular cells was increased after stimulation with glucoc orticoids and after addition of recombinant TGF beta 2, indicating an autor egulation of TGF beta 2. Furthermore, application of recombinant TGF beta 2 to cocultures resulted in an enhanced aggregation and cell clustering of S ertoli cells, pointing to an important role of TGF beta 2 in the paracrine interaction of peritubular and Sertoli cells of the developing rat testis.