Abstract 167: Optical Biopsy of Apoptosis in Ischemic Myocardium with Fluorometry
Background: Mitochondrial dysfunction plays an important role in the apoptotic process which contributes to ventricular remodeling and reperfusion injury. Unfortunately this understanding has not translated into therapeutic strategies because of an inability to assess mitochondrial dysfunction effectively in humans. We have developed an optical, catheter device to acquire the fluorescence signals of mitochondrial fluorophores, Nicotinamide Adenine Dinucleotide (NAD) and Flavoprotein (FP). The normalized ratio of these signals (FP/FP+NADH), called the redox ratio, is a measure of steady state metabolism. We hypothesize that our device can be used to quantify mitochondrial dysfunction/apoptosis associated with reperfusion injury in vivo.
Method: Ten rabbits received coronary artery occlusion for 30 minutes followed by 3 hours reperfusion. Prior to ischemia, five animals received an infusion of saline and five cyclosporine A (CsA). Using the fluorometric probe the redox ratio was measured continuously in the area at risk (RA) during the entire experiment. RA and infarct size as a percentage of the RA (IA/RA) were determined using a double staining technique. Myocardium from under the probe was assessed for apoptosis using In Situ Oligo Ligation (ISOL).
Results: The redox ratio (RR) demonstrated a marked oxidative shift after reperfusion in the saline animals. This shift that progressed steadily during reperfusion, is due to uncoupling in the mitochondrial electron transport chain. The administration of CsA significantly reduced IA/RA, apoptosis and the oxidative shift in the redox ratio. ISOL positivity and IA/RA were also highly correlated with terminal redox ratio values (p<0.05).
Conclusion: In vivo measurement of the redox ratio correlates well with reperfusion induced injury and apoptosis. With further study, this technique may be developed into a clinical tool to assess reperfusion injury and ventricular remodeling.