BONE MARROW TRANSPLANTION AND ATHEROSCLEROSIS

动脉粥样硬化是老年人发病和死亡的主要原因， 西方世界 动脉粥样硬化的第一个可识别的病变， 条纹，主要由充满胆固醇酯的巨噬细胞（泡沫）组成 细胞）中。 这个项目的目标是利用小鼠 骨髓移植作为一种方法来研究的作用， 巨噬细胞在动脉粥样硬化和脂蛋白代谢中的作用。 第一 设计了一个特定的目的来检验骨转移的假设， 将带有特定遗传标记的骨髓细胞植入经过致命辐射的 在适当的致动脉粥样硬化条件下， 将供体单核细胞递送至动脉内膜， 巨噬细胞来源的泡沫细胞。 ROSA beta-geo 26 具有普遍表达的来自 Lac Z基因将在这些实验中用作骨髓供体， 提供了一个易于检测的遗传标记来跟踪供体的命运， 巨噬细胞 一旦宿主重新繁殖的条件 供体来源的巨噬细胞已经建立，我们将使用这个系统 研究载脂蛋白（apo）E分泌的作用， 巨噬细胞在脂蛋白代谢和动脉粥样硬化中的作用。 血浆脂蛋白中的大多数apoE是肝源性的， 肝外apoE对代谢的相对贡献 血浆脂蛋白不确定。 ApoE是LDL受体的配体 并促进几类脂蛋白从 等离子体 apoE基因靶向破坏的纯合子小鼠 出现严重高脂血症和自发性主动脉和冠状动脉 动脉粥样硬化 在第二个具体目标中， 将来自具有正常apoE基因的小鼠的骨髓移植到apoE缺陷小鼠中， 进行研究肝外apoE的能力，有助于 血浆apoE水平和血浆脂蛋白的清除。 已知巨噬细胞分泌大量载脂蛋白E， 当暴露于体外乙酰化低密度脂蛋白时游离胆固醇。 泡沫细胞 胆固醇的形成可以被看作是胆固醇流入和 流出 巨噬细胞分泌ApoE可能促进胆固醇流出 从巨噬细胞，从而起到保护作用，防止泡沫细胞 阵 apoE缺陷小鼠自发性 动脉粥样硬化，而表达缺陷apoE的转基因小鼠 而肝脏则没有，这表明巨噬细胞apoE的分泌可能确实起到了 在动脉粥样硬化易感性方面的保护作用。 第三 具体目的是，巨噬细胞分泌载脂蛋白E在促进 胆固醇流出将在体外进行测试，骨髓移植 实验将检验巨噬细胞分泌载脂蛋白E的假设， 影响体内动脉粥样硬化的易感性。 测试 假设巨噬细胞不能分泌apoE， 动脉粥样硬化的易感性增加，骨髓中的apoE 将缺陷型小鼠移植到C57 BL/6小鼠中。 此外该 将携带正常apoE基因的小鼠骨髓移植入apo 将测试E缺陷型小鼠作为促进 apoE缺陷小鼠的动脉粥样硬化。

Atherosclerosis is the major cause of morbidity and mortality in the Western World. The first recognizable lesion of atherosclerosis, the fatty streak, consists primarily of cholesteryl ester laden macrophages (foam cells) in the arterial intima. The goal of this project is to use murine bone marrow transplantation as a method to investigate the role of the macrophage in atherosclerosis and lipoprotein metabolism. The first specific aim is designed to test the hypothesis that the transfer of bone marrow cells bearing a specific genetic marker into a lethally irradiated host will result, under the appropriate atherogenic conditions, in the delivery of donor monocytes to the arterial intima and in the development of macrophage-derived foam cells of donor origin. The ROSA beta-geo 26 strain of mice which have ubiquitous expression of beta-galactosidase from the Lac Z gene will be used as bone marrow donors in these experiments, providing an easily detectable genetic marker to track the fate of donor macrophages. Once the conditions for repopulation of the host with macrophages of donor origin have been established, we will use this system to investigate the role of apolipoprotein (apo) E secretion by the macrophage in lipoprotein metabolism nd atherosclerosis. The majority of apoE in the plasma lipoproteins is of hepatic origin, and the relative contribution of extrahepatic apoE to the metabolism of the plasma lipoproteins is uncertain. ApoE is a ligand for the LDL receptor and promotes the clearance of several classes of lipoproteins from the plasma. Mice homozygous for the targeted disruption of the apoE gene develop severe hyperlipidemia and spontaneous aortic and coronary atherosclerosis. in the second specific aim, transplantation of bone marrow from mice with the normal apoE gene into apoE deficient mice will be performed to investigate the ability of extrahepatic apoE to contribute to plasma apoE levels and the clearance of plasma lipoproteins. The macrophage is known to secrete large amounts of apolipoprotein E and free cholesterol when exposed to acetylated-LDL in vitro. Foam cell formation can be viewed as an imbalance between cholesterol influx and efflux. ApoE secretion by the macrophage may facilitate cholesterol efflux from the macrophage, thus serving a protective role by preventing foam cell formation. Observations that apoE deficient mice develop spontaneous atherosclerosis, whereas transgenic mice expressing a defective apoE from the liver do not, suggest that macrophage apoE secretion may indeed play a protective role in regard to atherosclerosis susceptibility. In the third specific aim, the role of apo E secretion by the macrophage in promoting cholesterol efflux will be tested in vitro, and bone marrow transplantation experiments will test the hypothesis that apo E secretion by the macrophage influences susceptibility to atherosclerosis in vivo. To test the hypothesis that the inability of the macrophage to secrete apoE results in an increase in the susceptibility to atherosclerosis, bone marrow from apoE deficient mice will be transplanted into C57BL/6 mice. In addition, the transplantation of bone marrow from mice with the normal apoE gene into apo E deficient mice will be tested as a means of promoting regression of atherosclerosis in apoE deficient mice.