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

Transforming growth factor betas (TCF beta s) 1, 2, and 3 and their types I and II receptors (TCF beta s 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, TGF beta 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 TGF beta 1 and TGF beta RI staining in the spermatocytes. In the adult testis, TGF beta ligands exhibited a preferential tubular distribution. TGF beta 1 was mainly detected in young spermatocytes, TGF beta 2 in Sertoli cells, and TGF beta 3 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. TGF beta RI was predominant in meiotic and differentiated germ cells and TGF beta RII in somatic cells. Finally, in the adult testis, TCF beta s 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 TGF beta RI was present particularly during meiosis and spermiogenesis. Together, the temporal and spatial distribution of the TGF beta 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.