Abstract 2895: Targeted Ultrasound Imaging of Apoptosis with Annexin-A5 Microbubbles in Acute Doxorubicin-induced Cardiotoxicity
Background Recently, apoptosis has been suggested as a common mechanism of myocardial loss in doxorubicin-induced cardiomyopathy. The aim of this study was to assess the feasibility of targeted ultrasound imaging of apoptosis with annexin-A5 microbubbles (A5MB) in acute doxorubicin-induced cardiotoxicity.
Method Avidinated and octafluoropropan-filled phospholipid microbubbles were conjugated with biotinylated annexin-A5. To confirm the specific binding ability of A5MB, flow cytometry was performed with hydrogen peroxide induced apoptosis of rat aorta smooth muscle cells incubated with FITC-labeled annexin-A5 and A5MB. Adult male rats were injected with 5mg/kg doxorubicin IP weekly for 3 weeks (n=5). Control rats were injected with normal saline (n=2). At 24h after the final treatment, triggering imaging was done at a MI of 0.8 using 15MHz linear probe 15 minutes after IV bolus injection of A5MB for wash-out of freely circulating microbubbles. After the contrast echocardiography, the heart was isolated for histological detection of apoptosis (TUNEL assay).
Result In in vitro test, fluorescence intensity was low for the healthy cells and high for the apoptotic cells when incubated with FITC-labeled annexin A5 and A5MB. Rats treated with doxorubicin showed significant contrast opacification of myocardium in contrast echocardiography using A5MB (Fig A, B⇓). However, no opacification was observed in control rats (Fig C, D⇓). Late apoptosis was confirmed by TUNEL assay in doxorubicin treated rats.
Conclusion Acute doxorubicin induced cardiomyopathy based on early apoptosis can be assessed and imaged with targeted ultrasound imaging using A5MB in rats.