Formation of the Testicular Immunological Barrier through Immunomodulation and ZIP9 Androgen Signaling in Rat Sertoli Cells

Abstract

The blood-testis-barrier (BTB), which is mainly based upon Sertoli cells (SC), divides the seminiferous epithelium into a basal and an adluminal compartment. The main role of the BTB is to form an immunological barrier in order to preserve the meiotic and post-meiotic stages of the germ cells from the immune system. The BTB is composed by a number of tight junction proteins, mainly the claudins family. Disorder of the BTB integrity caused by any internal or external factors might result in male infertility. Our study aims at elucidating the role of different cell combinations (mainly SC and peritubular cells (PC) isolated from adult rats) on the BTB integrity and to elucidate the contribution of each cell type to the testicular immunological barrier (TIB). Furthermore, we treated rat primary SC with particular cytokines and hormones to address their effects in vitro on the TJ proteins and thus the BTB integrity. Our experiments showed that primary SCs are the main constituent of the BTB in vitro. Co-culturing of both rat SCs and PC on Matrigel only had a negligible effect on the tightness of the barrier. Likewise, transmigration assay of polarized rat macrophages (M0-M1-M2) did not show a significant difference of the number of migrated macrophages through a monolayer of SC or through a co-culture of SC and PC. Moreover, treatment of SC with bone morphogenetic protein2 (BMP2), interleukin-6 (IL-6) or transforming growth factor beta-3 (TGF-β3) resulted in a negative effect on the barrier tightness. In contrast, treatment of SC with testosterone upregulated the tight junction proteins zonula occludens-1 (ZO-1), junctional adhesion molecule-3 (JAM-3) and the barrier tightness via the classical or non-classical androgen pathway. SC tight junctions are the main constituent of the BTB in vitro.