Cellular distribution of transforming growth factor betas 1, 2, and 3 and their types I and II receptors during postnatal development and spermatogenesis in the boar testis

Abstract

Transforming growth factor betas (TGFβs) 1, 2, and 3 and their types I and II receptors (TGFβs RI and RII) were immunolocalized 1) during testicular development from the perinatal to the adult period and 2) in maturing germ cell populations at successive seminiferous epithelium stages. In the perinatal testis, TGFβ isoforms and receptors were both preponderant in Leydig cells and in spermatogonia. At prepuberty, their expression appeared in Sertoli cells, while germ cells showed specific TGFβ1 and TGFβRI staining in the spermatocytes. In the adult testis, TGFβ ligands exhibited a preferential tubular distribution. TGFβ1 was mainly detected in young spermatocytes, TGFβ2 in Sertoli cells, and TGFβ3 in Sertoli and premeiotic germ cells. Although the two receptors were systematically observed together in various cells, our data indicate a predominance of one in comparison with the other depending on the cell type. TGFβRI was predominant in meiotic and differentiated germ cells and TGFβRII in somatic cells. Finally, in the adult testis, TGFβs 1, 3, and RI showed a germ-cell pattern that depended upon the stage of the seminiferous epithelium cycle. Specifically, staining for the ligands was predominant before meiosis, and TGFβRI was present particularly during meiosis and spermiogenesis. Together, the temporal and spatial distribution of the TGFβ system components suggests that these signaling molecules may play a crucial role during specific steps of testicular development and during different waves of seminiferous epithelium maturation leading to spermatogenesis.