TESTICULAR DEVELOPMENT INVOLVES THE SPATIOTEMPORAL CONTROL OF PDGFS AND PDGF RECEPTORS GENE-EXPRESSION AND ACTION

Platelet-derived growth factors (PDGFs) are growth-regulatory molecule s that stimulate chemotaxis, proliferation and metabolism primarily of cells of mesenchymal origin. In this study, we found high levels of P DGFs and PDGFs receptors (PDGFRs) mRNAs, and specific immunostaining f or the corresponding proteins in the rat testis. PDGFs and PDGFRs expr ession was shown to be developmentally regulated and tissue specific. Expression of PDGFs and PDGFRs genes was observed in whole testis RNA 2 d before birth, increased through postnatal day 5 and fell to low le vels in adult, The predominant cell population expressing transcripts of the PDGFs and PDGFRs genes during prenatal and early postnatal peri ods were Sertoli cells and peritubular myoid cells (PMC) or their prec ursors, respectively, while in adult animals PDGFs and PDGFRs were con fined in Leydig cells. We also found that early postnatal Sertoli cell s produce PDGF-like substances and that this production is inhibited d ose dependently by follicle-stimulating hormone (FSH). The expression of PDGFRs by PMC and of PDGFs by Sertoli cells corresponds in temporal sequence to the developmental period of PMC proliferation and migrati on from the interstitium to the peritubulum. Moreover, we observed tha t all the PDGF isoforms and the medium conditioned by early postnatal Sertoli cells show a strong chemotactic activity for PMC which is inhi bited by anti-PDGF antibodies. These data indicate that, through the s patiotemporal pattern of PDGF ligands and receptors expression, PDGF m ay play a role in testicular development and homeostasis.