Evaluation of adenosine preconditioning with 99mTc-His10-annexin V in a porcine model of myocardium ischemia and reperfusion injury: preliminary study

Abstract

Purpose: The goal of this study was to evaluate the feasibility of (99m)Tc-His(10)-annexin V for the detection of acute myocardial cell death and to assess the effect of adenosine preconditioning in a porcine model of myocardium ischemia and reperfusion injury (RI).

Materials and methods: (99m)Tc-His(10)-annexin V was prepared by one-step direct labeling, and RCP and radiostability were tested. The binding of (99m)Tc-His(10)-annexin V to apoptosis was validated in vitro using camptothecin-induced Jurkat cells. In vivo biodistribution was determined in mice by the dissection method. Ischemia of 20-30 min was induced by balloon occlusion of the epicardial coronary artery of the porcine model (n=14). Adenosine was infused intravenously in six pigs before coronary occlusion. (99m)Tc-His(10)-annexin V (n=12) was injected intravenously at 1 h after reperfusion. SPECT/CT was acquired at 3 h postinjection. Myocardial perfusion imaging (MPI) with (99m)Tc-MIBI was also performed 1 day after His(10)-annexin V imaging. Cardiac tissues were analyzed postmortem using hematoxylin-and-eosin and TUNEL staining. Caspase-3 activity was measured to confirm the presence of apoptosis.

Results: (99m)Tc-His(10)-annexin V had a RCP >98% and high stability 2 h after radiolabeling; it could bind to apoptotic cells with high affinity. Biodistribution of (99m)Tc-His(10)-annexin V showed a predominant uptake in the kidney and relatively low uptake in the myocardium, liver and gastrointestinal tract; rapid clearance from blood and kidney was observed. In the untreated group, intense uptake of His(10)-annexin V was visualized in the defect which was shown in MPI, whereas in the adenosine group a mild uptake of (99m)Tc-His(10)-annexin was found in the risk area which showed no defects in the (99m)Tc-MIBI image. TUNEL staining and activated caspase-3 confirmed the ongoing apoptosis in RI. Adenosine preconditioning significantly diminished the level of apoptosis. Uptake of His(10)-annexin V in RI correlated with TUNEL-positive nuclei.

Conclusion: This study addresses the feasibility of imaging of myocardial cell death in acute ischemia and RI in pigs with (99m)Tc-His(10)-annexin V; it holds prospect for the detection of myocardial cell death in clinical practice. Adenosine preconditioning could attenuate the myocardial apoptosis; its cardioprotective effect might partially be fulfilled by suppressing the ongoing apoptosis in ischemia and reperfusion. Further study is warranted.