Reciprocal expression of laminin A-chain isoforms along the crypt-villus axis in the human small intestine.
OBJECTIVE
Intestinal epithelial cell proliferation, migration, and differentiation are susceptible to various influences along the crypt-villus axis including compositional changes in the basement membrane and differential expression of receptors for these components. However, laminin has been consistently detected at the epithelial basement membrane without significant variation in relation to the crypt-villus functional unit. The aim of this study was to examine the distribution of individual laminin chains.


METHODS
The patterns of distribution of laminin A, M (an A-chain variant), B1, and B2 chains as well as the integrins alpha 6 beta 1 and alpha 6 beta 4, two laminin receptors, were determined by indirect immunofluorescence in the adult human small intestine.


RESULTS
Markedly distinct patterns of laminin chain expression were observed along the crypt-villus axis. The A chain was found predominantly associated with the differentiated epithelial cells on the villus whereas the M chain was restricted to the basement membrane of crypts. However, both B1 and B2 chains were detected all along the intestinal basement membrane. Furthermore, alpha 6 beta 1 and alpha 6 beta 4 integrins were found to be expressed by all enterocytes.


CONCLUSIONS
These observations show a reciprocal expression of laminin isoforms along the crypt-villus axis and support the concept that the intestinal epithelial basement membrane is subjected to intricate compositional changes.
Beaulieu
J F
JF
Département d'Anatomie et de Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Québec, Canada.
Vachon
P H
PH
D000328:Adult; D000368:Aged; D002454:Cell Differentiation; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D016023:Integrins / Q000378:metabolism; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D007536:Isomerism; D007797:Laminin / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D008875:Middle Aged; D009834:Oligo-1,6-Glucosidase / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism
D016023:Integrins; D007797:Laminin; D009834:Oligo-1,6-Glucosidase; D013393:Sucrase