An immunostaining-based approach for assessing myocardial viability in the infarcted mouse hearts.

INTRODUCTION: With the growing need for reliable and precise detection of cell viability in spatial biology, we introduce an antibody-based staining of cardiac troponin I (cTnI) as a simple yet valuable tool for delineating cardiomyocyte viability in the early stages of myocardial infarction (MI). METHODS & RESULTS: In circulation, cTnI was found to be the most abundantly released biomarker within the first 24†h after MI. In heart sections, partial depletion of cTnI staining was observed within dying cardiomyocytes as early as 6†h, with almost absence by 24†h despite of preserved membrane integrity. In contrast, staining for other sarcomeric proteins, such as troponin T and α-actinin, remained detectable for several days until immune cells infiltration occurred. We further validated the rapid loss of cTnI staining by cross-verifying in-vivo and ex-vivo measurements. Notably, cTnI-stained sections showed precise overlap with TTC-stained images at the cellular level and showed a highly consistent pattern of cardiomyocyte distribution and infarct area (r² = 0.96) when compared to in-vivo measurements using manganese-enhanced magnetic resonance imaging (MEMRI). CONCLUSION: These findings highlight the coordinated, stepwise breakdown of sarcomeric proteins following ischemic injury in the mouse heart and underscore the utility of antibody-based cTnI staining as a valuable tool for early myocardial viability assessment and infarct area detection with high spatial resolution.