Abstract P1116: Genetic Mapping Of Cardiomyocyte Ploidy Phenotypes To Identify Genetic Determinants Of Outcomes After Infarction

Abstract

Outcomes following cardiac injury are influenced by lifestyle and environment, as well as genetic background. Our interest lies in the latter, where very few genes have successfully been linked to heart failure. Contributors to this low success rate include high genetic diversity of patient populations, inability to control for non-genetic factors, and cellular complexities that contribute to outcomes. We propose utilizing the Hybrid Rat Diversity Panel (HRDP) to assess high throughput surrogate phenotypes, which can be predictive of outcomes after injury when measured in the basal state. This approach can offer a solution to the limitations of association studies for complex diseases like heart failure. Our surrogate phenotype of interest is cardiomyocyte ploidy, where high frequency of diploid cardiomyocytes is predictive of ability to regenerate and functional recovery. Conversely, an increased proportion of polyploid (≥8N) cardiomyocytes is associated with adverse ventricular remodeling and dilated cardiomyopathy. Having analyzed 50 of the 96 strains, we see that frequency of the MNDCMs varies from 1.3-20.3% across strains, while frequency of the highly polyploid CMs (≥8N) varies from 0.8-20.9%. Four strains have been selected for myocardial infarction (MI) studies, including M520 (17.4%) and F344 (20.3%) with high MNDCM content and GK (2.8%) and HXB23 (1.8%) with low MNDCM content. Following MI, both M520 and F344 rats exhibit a higher percentage of BrdU+ cardiomyocytes in the border zone region compared to HXB23 rats, supporting the hypothesis that strains with high MNDCM frequency would be better at mounting a proliferative response. This also translated to a greater functional improvement and smaller scars in M520 rats, but not in F344. Additionally, we looked at the size of cardiomyocytes following MI and found that HXB23 rats (20.9% ≥8N CMs) have an increased cross-sectional area in comparison to the other strains, which may be indicative of concentric hypertrophy in response to injury. The HRDP could serve as a powerful tool for mapping traits related to outcomes following MI, allowing us to identify potential gene candidates that may be interrogated further for future use in precision medicine-based therapies. Mapping studies are ongoing.