Adult mammalian Sertoli cells (SCs) have been considered to be quiescent terminal differentiated cells for many years, but recently, proliferation of adult SCs was demonstrated in vitro and in vivo. We further examined mouse SC behavior in culture and found that there are two populations of adult SCs. The first population is SCs from seminiferous tubules that hardly proliferate in vitro. The second population is small and consists of SCs with atypical nuclear morphology from the terminal segments of seminiferous tubules, a transitional zone (TZ). TZ SCs multiply in culture and form colonies, display mixture of mature and immature SC characteristics, and generate cord-like structures in a collagen matrix. The specific features of TZ SCs are ACTA2 expression in vitro and DMRT1 low levels in vivo and in vitro. Although the in vivo function of TZ SCs still remains unclear, this finding has significant implications for our understanding of SC differentiation and functioning in adult mammals.
Andrey Yu Kulibin and Ekaterina A Malolina
Ekaterina A Malolina and Andrey Yu Kulibin
Sertoli cells (SCs) are supporting cells in the mammalian testis that proliferate throughout fetal and postnatal development but exit the cell cycle and differentiate at puberty. In our previous study, we isolated a population of highly proliferative Sertoli-like cells (SLCs) from the region of the adult mouse testis containing the rete testis and adjacent seminiferous tubules. Here RNA-seq of the adult SLC culture as well as qPCR analysis and immunofluorescence of the adult and immature (6 dpp) SLC cultures were performed that allowed us to identify SLC-specific genes, including Pax8, Cdh1, and Krt8. Using these, we found that SLCs are mostly localized in the rete testis epithelium; however, some contribution of transitional zones of seminiferous tubules could not be excluded. The main feature of SLCs indicating their relationship to SCs is DMRT1 expression. More than 40% of both adult and immature SLCs expressed DMRT1 at different levels in culture. Only rare DMRT1+ cells were detected in the adult rete testis, whereas more than 40% of cells were positively stained for DMRT1 in the immature rete testis. One more SC protein, AMH, was found in some rete cells of the immature testis. It was also demonstrated that SLCs expressed such SC genes as Nr5a1, Dhh, Gdnf, and Kitl and interacted with germ cells in 3D co-culture with immature testicular cells. All these similarities between SLCs and rete cells on one the hand and SCs on the other, suggest that rete cells could share a common origin with SCs.