TGFβs Modulate Permeability of the Blood-Epididymis Barrier in an In Vitro Model

Abstract

The blood-epididymis barrier (BEB) is formed by epithelial tight junctions mediating selective permeability of the epididymal epithelium. Defective barrier function can disturb the balance of the epididymal milieu, which may result in infertility. The stroma of the epididymis contains high amounts of cytokines of the TGFβ family of unknown function. We screened possible effects of all three TGFβ isoforms on paracellular tightness in a BEB in vitro model based on the strongly polarized mouse epididymal epithelial MEPC5 cells in the transwell system. In this model we found a robust transepithelial electrical resistance (TER) of about 840 Ω x cm2. Effects on the paracellular permeability were evaluated by two methods, TER and FITC-Dextran-based tracer diffusion assays. Both assays add up to corresponding results indicating a time-dependent disturbance of the BEB differentially for the three TGFβ isoforms (TGFβ3>TGFβ1>TGFβ2) in a TGFβ-recetor-1 kinase- and Smad-dependent manner. The tight junction protein claudin-1 was found to be reduced by the treatment with TGFβs, whereas occludin was not influenced. Epididymal epithelial cells are predominantly responsive to TGFβs from the basolateral side, suggesting that TGFβ may have an impact on the epididymal epithelium from the stroma in vivo. Our data show for the first time that TGFβs decrease paracellular tightness in epididymal epithelial cells, thus establishing a novel mechanism of regulation of BEB permeability, which is elementary for sperm maturation and male fertility.

HNF1 regulates critical processes in the human epididymis epithelium

“…TEAD1 is involved in the Hippo signaling pathway, which dictates organ size (37). SMAD4 is an important downstream effector of TGF-β signaling that regulates many cellular functions (38) including blood epididymis barrier permeability (39). ELF3 is thought to participate in epithelial cell differentiation and tumorigenesis (reviewed in (40)).…”

Cardiotonic steroid ouabain stimulates expression of blood–testis barrier proteins claudin-1 and -11 and formation of tight junctions in Sertoli cells

“…The experiments were performed in analogy to a previously published protocol (Stammler et al, 2013). A total of 2.5 × 10 4 cells were seeded in ThinCert inserts of 0.4 μm pore diameter for use with 12-well plates (both from Greiner, Frickenhausen, Germany) and grown in 1 ml of DMEM/Ham's F-12 containing 10% FCS and 1% PS until they reached confluence.…”

The blood-epididymis barrier and inflammation

“…It is likely that these functions are achieved by MMPs via their regulation of some signaling pathways, via enzyme cascades and by generating some cytokines, growth factors, and adhesion molecules (NIH). Curiously, a recent study by Stammler et al 76 reported that the permeability of the BEB could be modulated by the TGF-b group of cytokines. Using an in vitro murine epididymal cell line, they showed that addition of TGFb-1,-2, or -3 to the cell medium was sufficient to reduce Cldn1 protein levels, and significantly increase paracellular permeability, with TGFb3 having the greatest effect.…”

“…[78][79][80] Similar effects of TGFb-3 have been observed on the blood-testis barrier. 81,82 Stammler et al 76 suggested that the role of TGFbs, under certain conditions such as infection or inflammation, could be to permit loosening of the BEB for dendritic cell migration into the epididymal epithelium. Dendritic cells, derived from monocytes, are specialized antigen-presenting cells and play a role in regulation of the immune system.…”