LAMININS, TENASCIN AND TYPE-VII COLLAGEN IN COLORECTAL MUCOSA

The distribution of different laminin polypeptides, type VII collagen and tenascin has been studied in adult and foetal colorectal mucosa by using the indirect immunofluorescence technique. Immunoreactivity for laminin al chain was located to basement membranes of epithelia, musc ularis mucosae, and blood vessels, respectively in different segments of adult colon and rectum. Laminin beta 1 and gamma 1 chains were addi tionally expressed in lamina propria. Laminin alpha 2 chain was also f ound in lamina propria around the pericryptal fibroblasts. Immunoreact ivity for laminin beta 2 chain was restricted to basement membranes in the muscularis mucosae and arteries. Laminin alpha 3 and beta 3 chain s, suggestive for laminin-5, were confined especially to surface epith elial basement membranes. Immunoreactivity for type VII collagen was c onfined to basement membrane of surface epithelium in a punctate manne r, while that for tenascin was seen slightly more broadly in the basem ent membrane zone and also in the muscular layer. The distribution of laminin chains in 16-week-foetal colon mostly resembled that of corres ponding adult tissue, although immunoreactivities for laminin alpha 2 and beta 2 chains were lacking. Type VII collagen and the high molecul ar weight isoform of tenascin were also absent from the foetal colon. The results show that the basement membrane of the surface epithelium of colon and rectum express the components of epithelial adhesion comp lex, laminin-5 (alpha 3-beta 3-gamma 2) and type VII collagen, resembl ing in this respect small intestine and stomach while laminin-2 (alpha 2-beta 1-gamma 1) appears to be associated with pericryptal fibroblas ts, and laminin-l (alpha 1-beta 1-gamma 1) widely in most basement mem branes.