Testin Secreted by Sertoli Cells Is Associated with the Cell Surface, and Its Expression Correlates with the Disruption of Sertoli-Germ Cell Junctions but Not the Inter-Sertoli Tight Junction

Abstract

Testin is a testosterone-responsive Sertoli cell secretory product. In the present study, we demonstrated that the amount of testin secreted by Sertoli cells in vitro was comparable with several other Sertoli cell secretory products. However, virtually no testin was found in the luminal fluid and cytosols of the testis and epididymis when the intercellular junctions were not previously disrupted, suggesting that secreted testin may be reabsorbed by testicular cells in vivo. Studies using Sertoli cells with and without a cell surface crosslinker and radioiodination in conjunction with immunoprecipitation illustrated the presence of two polypeptides of 28 and 45 kDa, which constitute a binding protein complex that anchors testin onto the cell surface. The 28-and 45-kDa peptide appear to be residing on and inside the cell surface, respectively. Immunogold EM studies illustrated testin was abundantly localized on the Sertoli cell side of the ectoplasmic specialization (a modified adherens junction) surrounding developing spermatids. In contrast, very few testin gold particles were found at the site of inter-Sertoli tight junctions. When the inter-Sertoli tight junctions were formed or disrupted, no significant change in testin expression was noted. This is in sharp contrast to the disruption of Sertoli-germ cell junctions, which is accompanied by a surge in testin expression. These results demonstrate the usefulness of testin in examining Sertoli-germ cell interactions.

Stage-dependency of apoptosis and the blood-testis barrier in the dogfish shark (Squalus acanthias): cadmium-induced changes as assessed by vital fluorescence techniques

“…Since a single mammalian Sertoli cell simultaneously nurtures four or five different germ cell stages and since each germ cell stage is known to control Sertoli cell secretory activities in a stage-related manner (Jégou et al 1992;Grima et al 1998), in vitro studies aimed at analysing testicular processes stage-by-stage are technically difficult.…”

“…Sertoli, Leydig, and peritubular myoid cells (Jégou et al 1992;Grima et al 1998) and (3) the presence of inter-Sertoli cell tight junctions create an evolutionary conserved blood-testis barrier that sequestrates meiotic and postmeiotic germ cells into a special microenvironment (Dym and Fawcett 1970;Bergmann et al 1984).…”

Coxsackie and adenovirus receptor (CAR) is a product of Sertoli and germ cells in rat testes which is localized at the Sertoli–Sertoli and Sertoli–germ cell interface

“…The establishment of tight junction permeability barrier was assessed by quantifying the TER across the cell epithelium as described [26]. In brief, Sertoli cells were isolated from 20-dayold rats and seeded at a cell density of 0.75 × 10 6 cells/cm 2 .…”

“…The resistance was multiplied by the surface area of the filter to yield the area resistance in ohms.cm 2 . The net value of electrical resistance was then computed by subtracting the background, which was measured on Matrigel-coated cell-free chambers, from values of Sertoli cell-plated chambers [26]. Under these conditions, inter-Sertoli tight junctions were mostly formed at ~2-3 days [23].…”

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…Although this seems to be due to the lack of suitable models that can be used to study tight junction assembly and disassembly, in reality several excellent experimental models are available. In essence, these include 1) culturing Sertoli cells at high density in the presence of calcium to initiate junction assembly, 2) calcium and ATP depletion and repletion experiments, 3) culturing cells in the presence of various factors such as growth factors and cytokines, and 4) detachment of cells from their substrate/ extracellular matrix (Denker and Nigam, 1998;Grima et al, 1998;Ben-Shaul and Ophir, 2001;Siu and Cheng, 2004b;Xia et al, 2005a). However, only a few of these in vitro systems have been used successfully to study tight junction dynamics in the testis (Byers et al, 1986;Janecki et al, 1991;Grima et al, 1992).…”