Endoglin, a TGF-beta receptor-associated protein, is expressed by smooth muscle cells in human atherosclerotic plaques

Endoglin is a transmembrane protein that is found in association with trans forming growth factor-beta (TGF-beta) superfamily receptor complexes and ha s an expression pattern that appears to be restricted primarily to endothel ial cells, activated macrophages, trophoblasts, and fibroblasts, Since muta tions in endoglin have been shown to be linked to hereditary hemorrhagic te langiectasia type 1, a disease manifested as vascular malformations charact erized by excessive layers of vascular smooth muscle cells (VSMC), the expr ession of endoglin was investigated in VSMC. In vivo, the majority of SMC i n human atherosclerotic plaques expressed high levels of endoglin, while en doglin was not detected in SMC from samples of the normal arterial wall. In vitro studies demonstrate that human aortic smooth muscle cells (HASMC) ex press the L-isoform of endoglin. Like endothelial cells, HASMC express endo glin protein as a dimer on the cell surface that binds TGF-beta1. In vitro, endoglin expression by HASMC is upregulated in response to TGF-beta1, sugg esting that the presence of this factor in the atherosclerotic plaque might be responsible for the increased expression of endoglin. The demonstration of increased levels of endoglin in VSMC in human atherosclerotic plaques s uggests a role for SMC endoglin in the maintenance of vascular integrity an d in the response of the vessel wall to injury. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.