Imaging of Atherosclerosis in Apoliprotein E Knockout Mice: Targeting of a Folate-Conjugated Radiopharmaceutical to Activated Macrophages
Imaging of Atherosclerosis in Apoliprotein E Knockout Mice: Targeting of a Folate-Conjugated Radiopharmaceutical to Activated Macrophages
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DOI：
10.2967/jnumed.109.071324
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发表时间：
2010-05-01
影响因子：
9.3
通讯作者：
Low, Philip S.
中科院分区：
文献类型：
--
作者：
Ayala-Lopez, Wilfredo;Xia, Wei;Low, Philip S.
早期发现心脏病对于实施降低心血管事件风险的干预策略至关重要。为此目的已经探索的放射成像方法包括F-18-FDG，其测量代谢活性升高的位点; Tc-99 m-annexin A5，其揭示增强的凋亡和血栓形成的区域;和Tc-99 m标记的抗凝集素样氧化低密度脂蛋白受体1抗体，其检测在多种血管相关细胞上过表达的凝集素样氧化低密度脂蛋白受体1。在这项研究中，我们研究了使用叶酸靶向螯合物的Tc-99 m-EC20，叶酸受体（FR）表达的巨噬细胞，积累在动脉粥样硬化斑块，内化富含胆固醇的脂蛋白颗粒，并演变成泡沫细胞，形成脆弱的动脉粥样硬化病变的组成部分成像。研究方法：将Tc-99 m-EC 20注射到正常或西方（高脂肪）饮食的载脂蛋白E敲除（apoE（-/-））小鼠中25周，并通过γ射线照相术成像。还解剖了处理的小鼠，并通过γ计数和放射自显影术对切除的椎间盘中的放射性进行定量。还通过比较用氯膦酸盐脂质体处理以消耗组织巨噬细胞之前和之后的apoE（-/-）小鼠的图像，比较Tc-99 m-EC20富集的位点与动脉粥样硬化组织的薄切片中巨噬细胞积聚的位点，并通过流式细胞术检查动脉粥样硬化斑块衍生的巨噬细胞上FR的表达，来检查FR表达巨噬细胞在Tc-99 m-EC20摄取中的作用。结果如下：ApoE（-/-）小鼠在进食西方食物后，其动脉粥样硬化病变中99 mTc-EC 20的蓄积量显著高于进食正常食物的小鼠。流式细胞术显示，与正常饮食的apoE（-/-）小鼠相比，西方饮食的apoE（-/-）小鼠的腹腔中FR阳性巨噬细胞数量更多。氯膦酸盐脂质体治疗显著降低了动脉粥样硬化组织中99 mTc-EC 20的蓄积，表明巨噬细胞或单核细胞负责摄取叶酸连接的放射性显像剂。组织切片的组织学和放射自显影分析表明，巨噬细胞蓄积与99 mTc-EC 20摄取区域相关。结论：99 mTc-EC20可选择性靶向FR阳性活化巨噬细胞，用于动脉粥样硬化的显像。
Early detection of heart disease is essential for the implementation of intervention strategies that reduce the risk of cardiovascular events. Radioimaging methods that have been explored for this purpose include F-18-FDG, which measures sites of elevated metabolic activity; Tc-99m-annexin A5, which reveals regions of enhanced apoptosis and thrombosis; and Tc-99m-labeled anti-lectinlike oxidized low-density lipoprotein receptor 1 antibody, which detects the lectinlike oxidized low-density lipoprotein receptor 1 that is overexpressed on a variety of vasculature-associated cells. In this study, we examine the use of a folate-targeted chelate of Tc-99m, termed Tc-99m-EC20, for imaging of folate receptor (FR)-expressing macrophages that accumulate in atherosclerotic plaques, internalize cholesterol-rich lipoprotein particles, and evolve into foam cells that form components of vulnerable atherosclerotic lesions. Methods: Tc-99m-EC20 was injected into apoliprotein E knockout (apoE(-/-)) mice fed a normal or Western (high-fat) diet for 25 wk and imaged by gamma-scintigraphy. Treated mice were also dissected, and radioactivities in excised aortas were quantified by gamma-counting and imaged by autoradiography. The role of FR-expressing macrophages in uptake of Tc-99m-EC20 was also examined by comparing images of apoE(-/-) mice before and after treatment with clodronate liposomes to deplete tissue macrophages, comparing the sites of Tc-99m-EC20 enrichment with sites of macrophage accumulation in thin sections of atherosclerotic tissues, and examining the expression of FRs on atherosclerotic plaque-derived macrophages by flow cytometry. Results: ApoE(-/-) mice on Western chow exhibited significantly greater accumulation of 99mTc-EC20 in atherosclerotic lesions than their counterparts on normal chow. The aortas of apoE(-/-) mice on a Western diet demonstrated greater numbers of FR-positive macrophages by flow cytometry than did those of apoE(-/-) mice on a normal diet. Clodronate liposome treatment significantly reduced the accumulation of 99mTc-EC20 in atherosclerotic tissues, suggesting that macrophages or monocytes are responsible for uptake of the folate-linked radioimaging agent. Histologic and autoradiographic analysis of tissue sections demonstrated that macrophage accumulation correlated with regions of 99mTc-EC20 uptake. Conclusion: 99mTc-EC20 can be used for the imaging of atherosclerosis by selectively targeting FR-positive activated macrophages.