Abstract 2243: In Vivo 3D MR Angiography Reveals Accelerated Collateral Vessel Growth in CD73−/− Mice after Hindlimb Ischemia
Adenosine is a potent stimulator of angiogenesis, however, its role in arteriogenesis is not yet known. To address this issue we induced severe hindlimb ischemia in a mouse mutant lacking CD73 (ecto-5′-nucleotidase) which shows enhanced monocyte adhesion to the endothelium, considered to be an important initial trigger for arteriogenesis. For serial comparison of blood flow recovery and direct visualization of newly developed collateral vessels in wild-type (WT) and CD73−/− mice we established a high resolution 3D MR angiography (MRA) protocol. MRA images (field of view 2.56x2.56x1.92 cm3, matrix 256x256x192, voxel size 1 nl) of murine hindlimbs were recorded at 9.4 T within a reasonable acquisition time of approximately 30 min and were subsequently segmented and quantified using in-house-developed software. Collateral flow was detected as early as 3 d after ligation reaching a transient maximum 7 d after occlusion. At this time the extent of collateralization in the ischemic area was substantially enlarged in CD73−/− mice (+70% vs. WT, p<0.05, n=6). The improved blood supply was also reflected in a faster recovery of hindlimb muscle energetics in the mutant compared with WT controls as assessed by 31P MR spectroscopy in vivo. Histology confirmed the enhanced development of collaterals in CD73−/− mice. In conclusion, our protocol allows the quantitative assessment of growing collateral vessels in mice. We found that lack of CD73-derived adenosine promotes arteriogenesis. Fig. 1⇓: MRA from hindlimbs of CD73−/− mice 7 d after ligation of the femoral artery. Newly developed collateral vessels are colored in green. Insert shows the typical “corkscrew morphology” of the collaterals.