Abstract P2012: Development Of An In Vitro Assay To Model Loss Of Neighbor At The Infarct Border Zone

Abstract

The borderzone (BZ) of the infarcted heart separates poorly-perfused areas of cell death from well-perfused territories of comparatively normal myocardium. The BZ after myocardial infarction is of key importance for the remodeling process that drives heart failure and sudden cardiac death. We recently defined the transcriptional features of the infarct borderzone using single cell RNA-Seq and spatial transcriptomics which revealed prominent upregulation of mechanotransduction transcriptional programs. A similar transcriptional response was inducible by needle trauma alone. To explain these results, we proposed the “Loss of Neighbor” (LON) Hypothesis, where surviving cells neighboring the infarct experience mechanical instability due to the highly asymmetric loss of load, leading to cell signal activation. Here, we develop and validate an in vitro model of loss of neighbor using a mechanical scratch assay to model the biology of the infarct borderzone. We cultured neonatal rat cardiomyocytes and cardiac fibroblasts and subjected them to mechanical “scratch” injury. To evaluate how the mechanical wound altered gene expression, we performed qPCR for genes expressed by cardiomyocytes in the remote zone and the borderzone using RNA isolated from cells with or without exposure to mechanical scratch injury. Compared to non-scratched cultures, scratched cells significantly upregulated BZ-specific genes such as Ankrd1, Nppa, Flnc, and Xirp2 . In addition, scratched cells significantly upregulated expression of interferon-stimulated genes (ISGs) compared to non-scratched cells or scratched cells exposed to anti-IFNAR Ab. This suggests that the interferon-inducible cell (IFNIC) response observed at the infarct borderzone in vivo can be induced by in vitro cardiomyocyte LON. Taken together, our results suggest that the mechanical scratch assay in vitro captures key elements of the transcriptional borderzone in vivo . Overall, this model can guide further elucidation of the transcriptional program states during cardiac remodeling.