In vivo MR imaging of bone marrow cells trafficking to atherosclerotic plaques

Purpose: To develop a magnetic resonance imaging (MRI)-based method to monitor in vivo trafficking of bone marrow (BM) cells to atherosclerotic lesions. Materials and Methods: BM cells from LacZ-transgenic mice were labeled with a superparamagnetic iron oxide (Feridex) and then transplanted into ApoE^-/- recipient mice that were fed an atherogenic diet. Twenty-four ApoE^-/- mice were divided into three study groups: 1) group I with Feridex-labeled BM transplantation (BMT) cells (N = 9), 2) group II with unlabeled BMT cells (N = 10), and 3) group III with no BMT cells (N = 5). Migrated Feridex/LacZ-BM cells to atherosclerotic aortic walls were monitored in vivo using a 4.7T MR scanner and correlated with histopathological findings. Results: In group I with Feridex-BMT cells, histology examination displayed plaques in five of nine animals. In four of these five animals, in vivo MRI showed large MR signal voids of the aorta walls (due to the "blooming" effect of migrated Feridex-BM cells in plaques), which were correlated with Feridex- and/or LacZ-positive cells detected in the atherosclerotic lesions. No signal voids could be visualized in the two control animal groups (groups II and III). Conclusion: This study demonstrates the potential use of in vivo MRI to monitor the trafficking of magnetically labeled BM cells to atherosclerotic lesions.