RESUMO
RATIONALE: Tissue factor pathway inhibitor (TFPI) is a potent regulator of the tissue factor pathway and is found in plasma in association with lipoproteins. OBJECTIVE: To determine the role of TFPI in the development of atherosclerosis, we bred mice which overexpress TFPI into the apolipoprotein E-deficient (apoE(-/-)) background. METHODS AND RESULTS: On a high-fat diet, smooth muscle 22alpha (SM22alpha)-TFPI/apoE(-/-) mice were shown to have less aortic plaque burden compared to apoE(-/-) mice. Unexpectedly, SM22alpha-TFPI/apoE(-/-) had lower plasma cholesterol levels compared to apoE(-/-) mice. Furthermore, SM22alpha-TFPI mice fed a high-fat diet had lower cholesterol levels than did wild-type mice. Because TFPI is associated with lipoproteins and its carboxyl terminus (TFPIct) has been shown to be a ligand for the very-low-density lipoprotein (VLDL) receptor, we hypothesized that TFPI overexpression may regulate lipoprotein distribution. We quantified VLDL binding and uptake in vitro in mouse aortic smooth muscle cells from SM22alpha-TFPI and wild-type mice. Mouse aortic smooth muscle cells from SM22alpha-TFPI mice demonstrated higher VLDL binding and internalization compared to those from wild-type mice. Because SM22alpha-TFPI mice have increased circulating levels of TFPI antigen, we examined whether TFPIct may act to alter lipoprotein distribution. In vitro, TFPIct increased VLDL binding, uptake, and degradation in murine embryonic fibroblasts. Furthermore, this effect was blocked by heparinase treatment. In vivo, systemic administration of TFPIct reduced plasma cholesterol levels in apoE(-/-) mice. CONCLUSIONS: These studies suggest that overexpression of TFPI lowers plasma cholesterol through the interaction of its carboxyl terminus with lipoproteins and heparan sulfate proteoglycans.
Assuntos
Apolipoproteínas E/deficiência , Aterosclerose/prevenção & controle , Colesterol na Dieta/sangue , Lipoproteínas/metabolismo , Músculo Liso Vascular/metabolismo , Animais , Aorta/metabolismo , Apolipoproteínas E/genética , Aterosclerose/genética , Aterosclerose/metabolismo , Aterosclerose/patologia , Transporte Biológico , Células Cultivadas , Modelos Animais de Doenças , Proteoglicanas de Heparan Sulfato/metabolismo , Heparina Liase/metabolismo , Humanos , Lipoproteínas/genética , Lipoproteínas VLDL/sangue , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Proteínas dos Microfilamentos/genética , Proteínas Musculares/genética , Músculo Liso Vascular/patologia , Interferência de RNA , Receptores de LDL/genética , Receptores de LDL/metabolismo , Fatores de Tempo , Transfecção , Triglicerídeos/sangue , Regulação para CimaRESUMO
Cells with an endothelial phenotype can be cultured from peripheral blood. These cells include cells of a monocytic origin with endothelial features (culture-modified mononuclear cells, CMMCs) and, at later time points, blood outgrowth endothelial cells (BOECs). Both are promising candidates for systemic cell-based cardiovascular therapies and each may have unique capabilities. Indeed, the combined use of both cell types has been shown to have synergistic therapeutic features requiring simultaneous delivery. However, the majority of preclinical studies of cell delivery have used splenectomized animals to increase systemic distribution. The goal of this study was to directly compare the distribution of these two cell types following systemic delivery in an intact animal model. A similar pattern of delivery was seen following delivery of both cell types with detection in the lung, liver, bone marrow, and spleen. Taken together, the data suggest that strategies using systemic delivery of circulation-derived cells must consider the distribution and efficiency of delivery in intact animals.
