title: CD44 regulates vascular endothelial barrier integrity via a PECAM-1 dependent mechanism.
abstract: Vascular integrity is a critical parameter in normal growth and development. Loss of appropriate vascular barrier function is present in various immune- and injury-mediated pathological conditions. CD44 is an adhesion molecule expressed by multiple cell types, including endothelial cells (EC). The goal of the present study was to examine how loss of CD44 affected vascular permeability. Using C57BL/6 WT and CD44-KO mice, we found no significant permeability to Evan's Blue in either strain at baseline. However, there was significantly increased histamine-induced permeability in CD44-deficient mice compared to WT counterparts. Similar results were observed in vitro, where CD44-deficient endothelial monolayers were also impermeable to 40kD-FITC dextran in the absence of vasoactive challenge, but exhibited enhanced and prolonged permeability following histamine. However, CD44-KO monolayers have reduced baseline barrier strength by electrical resistance, which correlated with increased permeability, at baseline, to smaller molecular weight 4-kD FITC-dextran, suggesting weakly formed endothelial junctions. The CD44-KO EC displayed several characteristics consistent with impaired barrier function/dysfunctional EC junctions, including differential expression, phosphorylation, and localization of endothelial junction proteins, increased matrix metalloprotease expression, and altered cellular morphology. Reduced platelet endothelial cell adhesion molecule-1 (PECAM-1) expression by CD44-KO EC in vivo and in vitro was also observed. Reconstitution of murine CD44 or PECAM-1 restored these defects to near WT status, suggesting CD44 regulates vascular permeability and integrity through a PECAM-1 dependent mechanism.
authors.affiliation: Department of Pathology, Yale University School of Medicine, 310 Cedar Street LH115, P.O. Box 208023, New Haven, CT 06520-8023, USA.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Flynn
authors.forename: Michael
authors.initials: M
authors.lastname: Michaud
authors.forename: Sandra
authors.initials: S
authors.lastname: Canosa
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Madri
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002199:Capillary Permeability / Q000235:genetics / Q000502:physiology*; D003911:Dextrans; D004730:Endothelium, Vascular / Q000378:metabolism / Q000502:physiology*; D005070:Evans Blue; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism*; D013997:Time Factors
chemical_list: C476399:Cd44 protein, mouse; D003911:Dextrans; D018960:Hyaluronan Receptors; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C015219:fluorescein isothiocyanate dextran; D005070:Evans Blue; D016650:Fluorescein-5-isothiocyanate