The immunohistochemical localization of transforming growth factor-beta 2 in the fetal and neonatal rat testis

The localization of transforming growth factor beta-2 (TGF beta 2) in the fetal and neonatal testis (from day 13.5 of fetal life to postnatal day 9) was investigated by an immunohistochemical staining method employing a specific polyclonal antibody. Immunostaining appeared on fetal day 13.5 in primitive Sertoli cells as they begin to come in contact with each other and surround the germ cells to form the seminiferous cords. Staining in Sertoli cells was still clearly observed until fetal day 16.5 and became faint or undetectable from fetal day 18.5 onwards. In fetal-type Leydig cells, a positive reaction for TGF beta 2 appeared on day 16.5 and became very intense from day 18.5 onwards. In the germ cells, immunoreactivity for TGF beta 2 appeared on fetal day 20.5, rose to a maximum on postnatal day 4 and decreased thereafter. On postnatal day 9, staining was still present in type A spermatogonia and absent in type B spermatogonia. No immunoreactivity was detected in peritubular cells on any day studied. In conclusion, our results are in favour of an autocrine/paracrine role of TGF beta 2 in the differentiation of the testis during the perinatal period. It may be involved in the organization of the seminiferous cords, the regulation of testosterone production and the regulation of the number of germ cells. When compared with the immunolocalization of TGF beta 1 that we have previously reported [1], the present study suggests that the roles of TGF beta 2 in the developing rat testis can be specific but also overlap from those of TGF beta 1.