Abstract
Tight junctions between Sertoli cells of the testicular seminiferous epithelium establishes the blood-testis barrier (BTB) and creates a specialized adluminal microenvironment above the BTB that is required for the development of the germ cells that reside there. Actin filament-based anchoring junctions between Sertoli cells and germ cells are important for maintaining close physical contact between these cells as well as regulating the release of mature spermatids into the lumen. Previously, we reported that Sertoli cell injury in rodents after mono-(2-ethylhexyl) phthalate (MEHP) exposure results in the activation of matrix metalloproteinase 2 (MMP2) and increases the sensitivity of germ cells to undergo apoptosis. A disruption in the physical association between Sertoli cells and germ cells and premature loss of germ cells from the seminiferous epithelium has been widely described after phthalate treatment. In this study, we investigate the functional participation of MMP2 in the mechanism underlying MEHP-induced disruption of junction complexes and the resultant loss of germ cells. Exposure of C57BL/6J mice to MEHP (1 g/kg, oral gavage) decreased the expression of occludin in the tight junctions between Sertoli cells and caused gaps between adjacent Sertoli cells as observed by transmission electron microscopy. A reduced expression of laminin-gamma3 and beta1-integrin in apical ectoplasmic specializations between Sertoli cells and germ cells in a time-dependent manner was also observed. Treatment with specific MMP2 inhibitors (TIMP2 and SB-3CT) both in vitro and in vivo significantly suppressed MEHP-induced germ cell sloughing and changes in the expression of these junctional proteins, indicating that MMP-2 plays a primary role in this process. Furthermore, the detachment of germ cells from Sertoli cells appears to be independent of the apoptotic signaling process since MEHP-induced germ cell detachment from Sertoli cells could not be prevented by the addition of a pan-caspase inhibitor (z-VAD-FMK).