Anchoring complex components laminin-5 and type VII collagen in intestine: Association with migrating and differentiating enterocytes

Anchoring complex component laminin-5 and its subunits laminin (Ln)-alpha 3 and Ln-beta 3 chains, Type VII collagen, and integrin chains alpha 3, alpha 6, and beta 4 were studied in developing and adult human intestine and compared with findings on Ln-alpha 1 and Ln-alpha 2 chains. In adult human duodenum, jejunum, and ileum, Ln-5 detected with a polyclonal antiserum and Ln-alpha 3 and Ln-beta 3 chains, detected with monoclonal antibodies (MAbs), were restricted to the epithelial basement membranes (BMs) of villi, whereas Ln-alpha 2 chain was seen only focally in crypt bottoms. In double labeling experiments, the stretch of crypt BM corresponding to the proliferative cell compartment was found to be devoid of both Ln-alpha 3 and Ln-alpha 2 chains. Double labeling for Ln-5 and proliferating cell nuclear antigen also showed an abrupt onset of Ln-5 expression exactly at the upper edge of the proliferative cell compartment, Type VII collagen was negligible in duodenum and showed a rising duodenal-ileal gradient localizing to villar BMs, Double labeling for Ln-5 and Type VII collagen, however, indicated only partial co-distribution in the intestine. Electron microscopy of ileum revealed both anchoring filaments and anchoring fibrils but no hemidesmosomal plaques. Our results demonstrate the expression of Ln-5 in BMs outside of stratified epithelia and indicate that Ln-5 in the intestine is associated with the compartment of migrating and differentiating enterocytes. Absence of hemidesmosomes and the presence of other anchoring complex components, such as Ln-5, Type VII collagen, and integrin chains alpha 3, alpha 6, and beta 4, suggests unique properties for epithelial cell attachment in the intestine.