CD44 variant expression in inflammatory colonic mucosa is not disease specific but associated with increased crypt cell proliferation.

AIMS: A recent study reported increased epithelial expression of CD44 variants in ulcerative colitis (UC) compared with Crohn's disease (CD). However, the use of CD44 expression for diagnostic purposes in inflammatory bowel disease has been controversial, and the meaning of the appearance of CD44 variants in epithelial colonic cells remains unknown. We investigated the relationship between CD44 isoform expression and crypt cell proliferation in paediatric colitis. METHODS AND
RESULTS: The expression of CD44v3, CD44v6, and MIB1 (proliferation marker) was studied by immunohistochemistry on surgical colonic samples of UC (n = 13), CD (n = 10), colostomy resections with non-specific mucosal inflammation (NSMI) (n = 3), and normal controls (N = 5). The proliferation index (% of MIB1 positive cells) was assessed in both v6 positive and v6 negative crypts. Epithelial expression of CD44v3 and v6, negative in normal controls, was variable and focal in colitis. No preferential expression of CD44 variants was found in UC. The proliferation index was dramatically increased in v6 positive crypts compared with v6 negative crypts in UC, CD and NSMI.
CONCLUSIONS: These data suggest that CD44 variant staining is not a useful marker for distinguishing paediatric UC from CD, and that CD44v6 expression in the inflamed colonic mucosa is not disease specific but is related to crypt cell proliferation.