Transient Sprr1a expression defines a population of border zone cardiomyocytes that survive ischemic injury

Cardiomyocytes in the border zone (BZ) of a myocardial infarction (MI) reside directly adjacent to the ischemic core, a niche characterized by tissue necrosis, immune cell infiltration, and altered mechanical properties. Very few tools exist to study the BZ, limiting the development of strategies to prevent cardiomyocyte death and infarct expansion or promote heart regeneration. Here, we describe two novel mouse lines to visualize, track, and isolate BZ cardiomyocytes, which has revealed their transcriptional signature and surprising longevity. Overall design: We subjected Sprr1a-GFP mice to MI at 12 weeks of age. 5 days after MI, we isolated cardiomyocytes by langendorff digestion. We separated GFP+ border zone myocytes from GFP- remote zone myocytes by flow cytometry using a 130um nozzle and slow flow rate. RNA was isolated from the cell pellets and subjected to RNA-sequencing. n= 5 mice.