Vascular rhexis in mice subjected to non-sustained myocardial ischemia and its therapeutic implications

We previously described the death of vascular cells (vascular rhexis) following persistent coronary occlusion. The present study was designed to determine whether non-sustained ischemia can initiate vascular rhexis and if so, whether relatively brief ischemic insults are sufficient. C57BL6 mice were subjected to coronary ligation for 15 min or 3 h followed by reperfusion. Soluble fractions of left ventricular (LV) homogenates were obtained 48 h after the onset of transitory coronary occlusion. They were assayed by Western blotting for quantification of alpha smooth muscle actin (alpha-SMA) and smooth muscle myosin heavy chain (SM-MHC) that we have shown reflect vascular rhexis delineated immunohistochemically. Non-sustained coronary occlusion for 3 h initiated vascular rhexis evident 45 h after reperfusion, but not earlier, as judged from Western blotting of alpha-SMA and SM-MHC. The number of small- and medium-sized vessels in the previously ischemic zones was reduced at 45 h after reperfusion as well. Thus, vascular rhexis occurs after ischemia as brief as 3 h but evolves slowly and is not evident for 45 h. The delayed disintegration of the vasculature makes it likely that it can be ameliorated by interventions initiated after non-sustained ischemia, rendering it an attractive target for diminution of phenomena such as late negative LV remodeling, and 'no reflow.'