# Oxidation–reduction imaging of myoglobin reveals two-phase oxidation in the reperfused myocardium

## TL;DR

This study uses myoglobin's oxidation states to track heart damage after blood flow is restored, offering a new imaging method for early myocardial infarction assessment.

## Contribution

A novel imaging pipeline is developed to analyze myoglobin's redox states in the reperfused myocardium as a potential biomarker for myocardial infarction.

## Key findings

- Myoglobin's fluorescence contributes to the myocardium's spectral signature under ischemia–reperfusion.
- Oxidized myoglobin signal peaks 3 hours post-reperfusion and decreases with cardioprotection.
- Early infarct size measured by oxidation–reduction imaging correlates with MRI results at 24 hours post-reperfusion.

## Abstract

Myocardial infarction (MI) is a serious acute cardiovascular syndrome that causes myocardial injury due to blood flow obstruction to a specific myocardial area. Under ischemic–reperfusion settings, a burst of reactive oxygen species is generated, leading to redox imbalance that could be attributed to several molecules, including myoglobin. Myoglobin is dynamic and exhibits various oxidation–reduction states that have been an early subject of attention in the food industry, specifically for meat consumers. However, rarely if ever have the myoglobin optical properties been used to measure the severity of MI. In the current study, we develop a novel imaging pipeline that integrates tissue clearing, confocal and light sheet fluorescence microscopy, combined with imaging analysis, and processing tools to investigate and characterize the oxidation–reduction states of myoglobin in the ischemic area of the cleared myocardium post-MI. Using spectral imaging, we have characterized the endogenous fluorescence of the myocardium and demonstrated that it is partly composed by fluorescence of myoglobin. Under ischemia–reperfusion experimental settings, we report that the infarcted myocardium spectral signature is similar to that of oxidized myoglobin signal that peaks 3 h post-reperfusion and decreases with cardioprotection. The infarct size assessed by oxidation–reduction imaging at 3 h post-reperfusion was correlated to the one estimated with late gadolinium enhancement MRI at 24 h post-reperfusion. In conclusion, this original work suggests that the redox state of myoglobin can be used as a promising imaging biomarker for characterizing and estimating the size of the MI during early phases of reperfusion.

The online version contains supplementary material available at 10.1007/s00395-024-01040-6.