Mesothelium expression of integrins in vivo and in vitro

OBJECTIVE: To characterize the expression of α subunits of integrin adhesion molecules in peritoneal tissue in vivo and in vitro. METHOD: Peritoneum from the anterior abdominal wall (n = 22) and the serosa of the posterior uterus (n = 11) was obtained from women of reproductive age without endometriosis who were undergoing surgery for benign conditions. Immunohistochemical studies were performed on serial sections of peritoneum from the anterior abdominal wall, the uterine serosa, mesothelial monolayer cultures, and peritoneum explants from the abdominal wall using monoclonal antibodies to α subunits of integrin adhesion molecules. Electron microscopy was performed to localize these adhesion molecules in the mesothelium. RESULTS: The mesothelial expression of α integrin subunits was identical in the anterior peritoneum and uterine serosa. In vivo the mesothelium strongly expressed α₂ and α₂ and variably expressed α₆. In the monolayer cultures there was moderate/strong staining for α₂, α₃, and α₅; there was minimal expression of αν. In the explants there was moderate/strong expression of α₂, α₃, α₅, and α(v) α₆ was variably expressed. The ultrastructure of the mesothelium was unique in the anterior peritoneum, uterine serosa, and the monolayer cultures. The integrin subunits were distributed throughout the cytoplasm, were expressed in the plasma membrane, and were present on the surface (ie, towards the peritoneal cavity) of the mesothelium. CONCLUSION: Integrins are expressed by the mesothelium of the peritoneum. The mesothelium expression of integrins in vivo differs from that of the mesothelium integrin expression in monolayer culture and explant culture.