CD44 isoforms, including the CD44 V3 variant, are expressed on endothelium, suggesting a role for CD44 in the immobilization of growth factors and the regulation of the local immune response

Endothelium plays a central role in the regulation of site and inflammation specific leukocyte migration. Some of the mediators involved in leukocyte migration, such as chemokines, can bind to heparan sulfate on the endothelium resulting in immobilization near their sites of production. Because CD44 variants expressing V3 have been shown to carry heparan sulfate side chains and to interact through these side chains with heparan sulfate binding growth factors, we investigated the expression of CD44 variants on endothelium. We found a strong expression of V5, V7-8 and V10 CD44 variants and a weaker expression of V3 and V6 CD44 variants on endothelium by using immuno-histochemistry and by FACS analysis. Expression of CD44 V3 variants was confirmed at both the protein and mRNA levels by Western blotting and by reverse transcriptase-PCR respectively. Expression of CD44 variants was unaffected by IL-1beta, IL-8, TNFalpha, IFNgamma or IL-4 treatment, indicating either constitutive expression of these variants or involvement of other cytokines in their regulation