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Chorioamnionitis is an acute inflammatory reaction associated with the premature rupture of the fetal membranes. It is caused mainly by invasion of bacteria from the vaginal tract that can penetrate the intact membranes and invade the amnion cavity and the decidua. Tight junctions (TJ) and adherent junctions (AJ) are intercellular junctions crucial for epithelia adhesion and permeability regulation in a wide variety of tissues and organs. Our aim is to investigate if TJ and AJ molecules are involved in human chorioamnionitis. We studied the protein expression (by immunohistochemistry and western blotting) and the mRNA levels (by RT-PCR) of some junction proteins such as Zonula Occludens-1 (ZO-1), occludin, VE-cadherin and βcatenin in fetal membranes from women with chorioamnionitis compared to those membranes derived from idiopathic pregnancies. Western blotting and immunohistochemical data established that occludin expression was decreased in amnion with chorioamnionitis compared to amnion from idiopathic pregnancies. Samples tested for ZO-1, VEcadherin and β-catenin (proteins and mRNAs) showed no differences between idiopathic and pathological membranes. One of the most relevant results is the decrease of occludin in membranes with chorioamnionitis. Since we have previously demonstrated that some cytokines, particularly elevated in the chorioamnionitis, cause the disruption of TJs in placental villi, we suggest that the decrease of occludin in amnion may be the first change that leads to the rupture of the amniotic membrane in this pathology.

The aim was to analyze the morphology of normal human macula densa (MD), evaluate the cells that may be responsible for its turnover, and collect quantitative data. Of four samples of normal human renal tissue, two were embedded in resin to measure the longitudinal extension and examine the ultrastructure of the MD, the other two were embedded in paraffin to study apoptosis and cell proliferation. The MD is composed of a monolayer tissue about 40 μm long, which includes 35-40 cells arranged in overlapping rows. Ultrastructurally, MD cells show two polarized portions: an apical end, with sensory features, and a basolateral aspect, with paracrine function. MD cells are connected apically by tight junctions, with/without adherens junctions, which form a barrier between the distal tubule lumen and the interstitium. Cells in degeneration, often associated with macrophages, and undifferentiated cells were found in the MD and adjacent distal tubule. A filamentous mat previously described in proximal tubule scattered tubular cells (STCs) was detected in the basal cytoplasm in undifferentiated cells. The tissue was consistently negative for the proliferation marker Ki67 and for the apoptotic markers caspase-3 and caspase-9. This work confirms our earlier morphological findings and provides new data: (a) MD cells display both apical adherens and tight junctions, the latter forming a tubulo-mesangial barrier; (b) the MD is a monolayer made up of about 40 cells arranged in rows; (c) the simultaneous presence of degenerating (8-13%) and undifferentiated (4-13%) cells reminiscent of STCs suggests a non-negligible cell turnover.