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The activation of the molecular cascade leading to Ca++ -induced differentiation in cultured epithelial cells might be provided by the establishment of intercellular junctions between cells. In the present paper, we tested the hypothesis that Ca++ concentration would determine morphological and biochemical changes in intercellular junctions of cultured human gingival cells. Triplicate samples of monolayer cultures of human oral gingival cells were grown with two different Ca++ concentrations (0.3 and 1.8 mM), and examined by transmission (TEM) and scanning (SEM) electron microscopy at different time periods. To determine the role of the E-cadherin/beta-catenin complex in intercellular junction formation, oral epithelial cell cultures were grown in 0.3 mM Ca++ in presence of a blocking antibody anti human E-cadherin, stained with antibodies anti human beta-catenin, and examined by confocal laser scanning microscopy (CLSM). By TEM and SEM, cells grown at physiologic Ca++ concentrations (i.e., 1.8 mM) showed a subjective increase of the size of microvilli and of the number of intercellular junctions, which was more evident after 3 days in culture. Desmosome-like junctions were observed in cells grown in 1.8 mM Ca++, not in cells grown in 0.3 mM. By CLSM, development of intercellular adhesion was marked by membranous localization of E-cadherin and beta-catenin within the first hours in both culture types. When cell-cell adhesion was prevented, cells showed round shape and no membranous localization of beta-catenin. Restoring cell adhesion brought about polygonal cell shape and membranous localization of beta-catenin. We can conclude that increased Ca++ concentration may determine biochemical and morphological changes at membranous level in human oral epithelial cells. These changes may facilitate the development of intercellular junctions.
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PMID:Intercellular junctions in oral epithelial cells: ultrastructural and immunological aspects. 1627 58

The armadillo Chaetophractus villosus is a seasonal breeder whose seminiferous epithelium undergoes rapid regression with massive germ cell loss, leaving the tubules with only Sertoli cells and spermatogonia. Here, we addressed the question of whether this regression entails 1) the disassembly of cell junctions (immunolocalization of nectin-3, Cadm1, N-cadherin, and beta-catenin, and transmission electron microscopy [TEM]); 2) apoptosis (immunolocalization of cytochrome c and caspase 3; TUNEL assay); and 3) the involvement of Sertoli cells in germ cell phagocytosis (TEM). We showed a dramatic reduction in the extension of vimentin filaments associated with desmosomelike junctions at the interface between Sertoli and germ cells, and an increased diffusion of the immunosignals of nectin-3, Cadm1, N-cadherin, and beta-catenin. Together, these results suggest loss of Sertoli-germ cell adhesion, which in turn might determine postmeiotic cell sloughing at the beginning of epithelium regression. Then, loss of Sertoli-germ cell adhesion triggers cell death. Cytochrome c is released from mitochondria, but although postmeiotic cells were negative for late apoptotic markers, at advanced regression spermatocytes were positive for all apoptotic markers. Transmission electron microscopy analysis showed cytoplasmic engulfment of cell debris and lipid droplets within Sertoli cells, a sign of their phagocytic activity, which contributes to the elimination of the residual meiocytes still present in the latest regression phases. These findings are novel and add new players to the mechanisms of seminiferous epithelium regression occurring in seasonal breeders, and they introduce the armadillo as an interesting model for studying seasonal spermatogenesis.
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PMID:Loss of Sertoli-germ cell adhesion determines the rapid germ cell elimination during the seasonal regression of the seminiferous epithelium of the large hairy armadillo Chaetophractus villosus. 2445 84