Epithelial cell biology最新文献

Although bladder cancers account for almost 5% of all human cancer deaths, little is known about the biochemistry of urothelial differentiation. We have recently identified three major protein subunits ('uroplakins') of asymmetric unit membranes (AUM), which form rigid-looking plaques covering up to 70% of the apical surface of urothelial superficial (umbrella) cells. The ordinary-looking plasma membranes that interconnect these plaques are believed to be functionally specialized, serving as flexible but durable 'hinges'. Whether these hinge membranes are biochemically unique is unknown. Using a new monoclonal antibody (AE32) we have identified an 85-100 kDa glycoprotein (UGP85) which appears to be urothelium-specific. In both normal urothelium and cultured urothelial colonies this cell surface protein is associated mainly with superficial cells, suggesting that its expression is differentiation dependent. Results from in vitro translation experiments indicated that this glycoprotein contains a core polypeptide of about 55 kDa. Using immunogold localization techniques, we showed that in cultured urothelial colonies--which are known to lack mature AUM plaques--UGP85 is distributed relatively uniformly on the apical surface of some differentiated cells. However, in superficial cells of normal urothelium UGP85 is mainly associated with the hinge areas. These results raise the possibility that UGP85 is a plasma membrane component which can be excluded, to varying extents, from the plaque region as 12 nm protein particles are assembled into a tightly packed paracrystalline AUM structure. The identification of UGP85 provides the first evidence that the hinge areas interconnecting the urothelial plaques are biochemically distinguishable from the plasma membranes of the relatively undifferentiated urothelial cells of the lower cell layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Ornithine decarboxylase (ODC) has been shown by biochemical analysis, to be important for cell proliferation and carcinogenesis in a variety of tissues, including the liver. We detected messenger RNA (mRNA) specific for the enzyme ODC in 18 patients with hepatocellular carcinoma by an in situ hybridization technique using a radiolabelled ODC probe on formalin-fixed liver specimens. Adjacent uninvolved liver tissues were used as controls. Among the adjacent uninvolved liver tissues, five showed evidence of cirrhosis. Poorly differentiated hepatocellular carcinoma has significantly higher levels of ODC mRNA than does well-differentiated hepatocellular carcinoma, which in turn has a significantly higher ODC mRNA level than adjacent uninvolved liver tissues; tissues showing evidence of cirrhosis, on the other hand, had a significantly lower ODC mRNA level than adjacent uninvolved liver tissue. This pattern of ODC gene expression in hepatocellular carcinoma is similar to the pattern of expression of other oncogenes in liver tumours. The quantitative detection of ODC mRNA in hepatocellular carcinoma by in situ hybridization may help elucidate the potential role of ODC in hepatocarcinogenesis.

To examine the role of stromal-epithelial interactions in the response of epithelial cells to oestrogens, tissue recombinations were prepared with epithelium (E) and stroma (S) from the vagina (V) and urinary bladder (BL), that is between oestrogen target tissues (VS and VE) and non-target tissues (BLS and BLE). Following 3 weeks of growth in intact female hosts, ovariectomy was performed and 1 week later the hosts subjected to various hormonal treatments. Whereas homotypic vaginal tissue recombinations (VS+VE) exhibited epithelial cornification and mucification (cycling), this activity was not observed in homotypic bladder recombinants (BLS+BLE) or in heterotypic tissue recombinants between vaginal and bladder tissues (VS+BLE and BLS+VE). In BLS+VE recombinants the epithelium remained atrophic and failed to respond to exogenous oestrogen alone or in combination with progesterone. This lack of hormonal responsiveness of vaginal epithelium was completely reconstituted when the epithelium of BLS+VE recombinants was recovered and reassociated with fresh vaginal stroma (VS). Examination of epithelial proliferative activity ([3H]thymidine labelling index) demonstrated a marked oestrogen-induced increase in epithelial proliferation in VS+VE recombinants. BLS+BLE recombinants were unresponsive to oestrogen as were recombinants composed of BLS+VE. However, when bladder epithelium was grown in association with vaginal stroma (VS+BLE) the epithelium exhibited an 8-fold oestrogen-induced increase in labelling index over oil-treated specimens. The lack of an oestrogen-induced proliferative response of vaginal epithelium in BLS+VE recombinants was reversed when the vaginal epithelium of these recombinants was recovered and reassociated with fresh vaginal stroma. These results indicate that the effects of oestrogen and progesterone on both epithelial differentiation and proliferation are critically dependent upon the appropriate stromal environment.

Circadian stage-dependent variations in cell cycle traverse of mouse epidermal cells in vivo were investigated. The fate of cohorts of basal cells pulse-labelled with bromodeoxyuridine (BrdUrd) at different times of the day were studied by bivariate BrdUrd/DNA flow cytometry of isolated epidermal basal cells. Basal cells were tracked through the cell cycle up to 96 h after intraperitoneal injection of BrdUrd at 0800 and 2000, or followed for 6 h after BrdUrd injection at 0400, 1200, 1600 and 2400. The results confirmed our previous assumption that the cell cycle progression through S phase and G2 phase is considerably delayed at night, i.e. from 1600 to 0400, compared with daytime. The results indicate variations in G1 phase as well. The data strongly support the hypothesis that the main parameters responsible for circadian fluctuations in mitotic activity are variations in the S and G2 phase durations. The data are also consistent with the notion of proliferative heterogeneity among basal cells as described by a hierarchical proliferation model.