Objectives-During inflammation, cell adhesion molecules are modulated or redistributed for leukocyte transmigration.Among molecules at the interendothelial junction, CD146 is involved in cell-cell cohesion and permeability, but its role in monocyte transmigration is unknown. Methods and Results-TNF enhanced CD146 expression at the junction and apical membrane of human umbilical veins endothelial cells (HUVECs) through CD146 synthesis and intracellular store redistribution. In addition, TNF increased the release of a soluble form (sCD146) through a metalloproteinase-dependent mechanism. The redistribution of CD146 to the junction led us to investigate its role in monocyte transmigration using THP1 and freshly isolated monocytes.Evidence that CD146 contributes to monocyte transmigration was provided by inhibition experiments using anti-CD146 antibodies and CD146 siRNA in HUVECs. In addition, sCD146 specifically bound both monocytes and HUVECs and dose-dependently increased monocyte transmigration. Assessment of sCD146 binding on immobilized CD146 failed to evidence any homophilic interaction. Together, our data suggest endothelial CD146 binds heterophilically with a yet unknown ligand on monocytes. Conclusions-Our results demonstrate that CD146 is regulated by the inflammatory cytokine TNF and that CD146 and sCD146 are both involved in monocyte transendothelial migration during inflammation. Key Words: endothelial cells Ⅲ inflammation Ⅲ cytokines Ⅲ human Ⅲ adhesion molecules T he endothelial junctions play a fundamental role in endothelial integrity, vascular permeability, and cellular traffic. 1 At least 2 types of cell-to-cell junctional structures have been identified in the endothelium: adherens junctions (AJ) and tight junctions (TJ). 2 These junctions are tightly regulated structures composed of several adhesion molecules interacting with cytoskeletal proteins. 3 Among the adhesive molecules, endothelial VE-cadherin 4 is localized in AJ and junctional adhesion molecule (JAM) 5 in TJ, whereas other molecules such as PECAM-1/CD31 (platelet endothelial cell adhesion molecule-1) and CD99 are not restricted to 1 type of junctional structure. 6 The inflammatory response is characterized by leukocyte infiltration from the circulation toward the tissues, after a multistep process in which proinflammatory endothelial activation results in increased vascular permeability and then in leukocyte adhesion and transmigration. 7 Endothelial activation is mediated by several inflammatory cytokines. Among them, TNF␣ increases the expression of cell adhesion molecules like ICAM-1 or VCAM-1 and induces the redistribution of junctional adhesion molecules such as PECAM-1, JAM, VE-cadherin, and CD99 which, in turn, promote the transendothelial migration of leukocytes. 8 We have previously shown that CD146 (S-Endo1 Ag) is a component of the endothelial junction localized outside defined junctional structures. 9 CD146, also referred to as MUC18, is a member of the immunoglobulin superfamily (IgSF) constitutively expressed in all typ...

CD146, an endothelial molecule involved in permeability and monocyte transmigration, has recently been reported to promote vessel growth. As CD146 is also detectable as a soluble form (sCD146), we hypothesized that sCD146 could stimulate angiogenesis. Experiments of Matrigel plugs in vivo showed that sCD146 displayed chemotactic activity on endogenous endothelial cells, and exogenously injected late endothelial progenitor cells (EPCs) . IntroductionCD146 is a component of the endothelial junction primarily expressed in endothelial cells. It is involved in the control of cell and tissue architecture, as demonstrated by the regulation of its expression during endothelium monolayer formation, its involvement in the control of paracellular permeability, and its colocalization with the actin cytoskeleton. 1 Besides its structural role, CD146 is also involved in cell signaling. 2,3 We have recently demonstrated that CD146 is involved in the regulation of monocyte transendothelial migration. 4 Recent findings indicate that CD146 displays angiogenic properties. In one study, the authors showed that an anti-CD146 antibody, mAb AA98, displayed antiangiogenic properties in chicken chorioallantoic membrane assays and inhibited tumor growth in different xenografted human tumor models in mice. In a model of human umbilical vein endothelial cells (HUVECs), it was also shown that silencing CD146 with specific siRNA inhibited the proliferation and migration of the cells. [5][6][7] Of interest, we have established that CD146 also exists in a soluble form (sCD146) as the result of metalloprotease-dependent shedding of membrane CD146. 4,8 sCD146 is detectable in the human serum, and its level is modulated in different pathologies, such as inflammatory bowel diseases, 9 pathologic pregnancies, 10 and chronic renal failure. 11 However, its exact role is still largely unknown.Postischemic neovascularization occurs as a result of 2 mechanisms: angiogenesis, which relies on mature endothelial cells already present at the ischemic site; and vasculogenesis, which involves the homing and endothelial differentiation of endothelial progenitor cells (EPCs) mobilized from the bone marrow. 12,13 Different angiogenic factors have been shown to trigger angiogenesis and/or vasculogenesis by directly or indirectly stimulating proliferation, differentiation, and migration of mature or precursor cells. Among these factors, the more effective are fibroblast growth factors (FGFs), vascular endothelial growth factor (VEGF), and angiopoietins (Ang). FGF-1 has been shown to stimulate the proliferation and differentiation of all cell types necessary for the constitution of an arterial vessel, including endothelial cells and smooth muscle cells. FGF-2 also promotes endothelial cell proliferation and organization of endothelial cells into capillary-like structures. 14 In vitro studies have clearly demonstrated that VEGF is a potent stimulator of angiogenesis, stimulating endothelial cell mitogenesis and migration, 15 and numerous clinical trials have been co...

Rationale: CD146, a transmembrane immunoglobulin mainly expressed at the intercellular junction of endothelial cells, is involved in cell-cell cohesion, paracellular permeability, monocyte transmigration and angiogenesis. CD146 exists as 2 isoforms, short (sh) and long (lg), but which isoform is involved remains undefined. Objective: The recently described role of CD146 in angiogenesis prompted us to investigate which isoform was involved in this process in human late endothelial progenitors (EPCs), with the objective of increasing their proangiogenic potential. Methods and Results: Immunofluorescence experiments showed that, in subconfluent EPCs, shCD146 was localized in the nucleus and at the migrating edges of the membrane, whereas lgCD146 was intracellular. In confluent cells, shCD146 was redistributed at the apical membrane and lgCD146 was directed toward the junction. In contrast to lgCD146, shCD146 was overexpressed in EPCs as compared to mature endothelial cells and upregulated by vascular endothelial growth factor and SDF-1 (stromal cell-derived factor 1). Study of the properties of both isoforms in vitro provided evidence that shCD146 was involved in EPC adhesion to activated endothelium, migration, and proliferation, with a paracrine secretion of interleukin-8 or angiopoietin 2, whereas lgCD146 was implicated in stabilization of capillary-like structures in Matrigel and transendothelial permeability. In an animal model of hindlimb ischemia, transplantation of shCD146-modified EPCs selectively promoted both EPC engraftment and blood flow. Conclusions: Altogether, these findings establish that CD146 isoforms display distinct functions in vessels regeneration.Selective improvement of therapeutic angiogenesis by shCD146 overexpression suggests a potential interest of shCD146-transduced EPCs for the treatment of peripheral ischemic disease. (Circ Res. 2010;107:66-75.)Key Words: CD146 Ⅲ endothelial progenitor Ⅲ angiogenesis Ⅲ ischemia Ⅲ peripheral artery disease C D146 is a cell adhesion molecule belonging to the immunoglobulin superfamily. It has been described as a component of the endothelial junction involved in the control of cell cohesion, permeability, and monocyte transmigration. 1,2 Initially described as a marker of tumor growth and metastasis in human melanoma, 3 CD146 has recently been shown to be involved in angiogenesis. Thus, it was reported that anti-CD146 antibodies inhibited proliferation and migration of HUVECs, 4 and also inhibited angiogenesis in chicken chorioallantoic membrane assays and tumor growth in mice. 5 Two different isoforms of gicerin, the chicken homolog of CD146, have been described by Dunon and colleagues.These 2 isoforms are generated by alternative splicing and differ at the end of their cytoplasmic region. 6 -8 The short isoform of gicerin exhibits a putative PDZ binding domain, which could mediate its anchoring to the cytoskeleton, whereas the long isoform contains a putative endocytosis motif. 6 Recently it was shown that, under shear stress conditions, transfection...