EXPLORING AND MODELING CARDIAC HYPERTROPHY USING H9C2 VENTRICULAR CELLS EXPOSED TO ANGIOTENSIN-II OR LIPOPOLYSACCHARIDE FOR STUDYING HEME METABOLISM REGULATION

Abstract

Background: Hypertrophy occurs in heart failure with preserved ejection fraction (HFpEF). The extracellular signal-regulated protein kinases (Erk1/2) and heme-regulated inhibitory kinase (HRIK) regulate protein synthesis in hypertrophy. Objective: Explore HFpEF patients for hypertrophy and identify associated disease features that may contribute to molecular mechanisms of interest: hypertrophy, heme metabolism, or estrogen signalling. Affirming these features and mechanisms of interest from a preclinical model public dataset and model hypertrophy in cell culture for hypothesis-testing. Hypotheses: Clinical HFpEF population shows evidence of hypertrophy, features of disease that might cause metabolic, hormonal, or inflammatory stress with males exhibiting higher rates of hypertrophy, and fewer comorbid features than females. Genes regulating heme metabolism, estrogen signaling, or cardiac hypertrophy are evident in pre-clinical rat models of HFpEF. Angiotensin II or lipopolysaccharide induce hypertrophy in H9c2 myoblasts and myotubes. Either hemin or estrogen attenuate H9c2 hypertrophy through Erk1/2, Hrik, or Nfkb signalling. Experimental Approach: 1) Define a cohort of clinical data that identifies patients with HFpEF from a cardiac surgery outcomes database; 2) Identify a preclinical rat model with HFpEF-like comorbid features, such as: diastolic dysfunction with preserved ejection fraction, hypertrophy, evidence of metabolic or inflammatory stress. Conduct a hypothesis-affirming study that identifies genes of interest associated with comorbid features of HFpEF, including, hypertrophy, heme metabolism, estrogen signalling, or inflammation, and 3) Confirm that an in vitro cell model of hypertrophy using H9c2 cells treated with angiotensin-II (hormones stress) and lipopolysaccharide (metabolic-inflammatory stress) can be used for hypothesis testing of treatments (e.g. hemin or estrogen) to limit hypertrophic signalling by western blotting and alter the course of cell size changes measured by immunocytochemistry and flow cytometry. Results/Conclusion: HFpEF patients show a complex comorbid condition that could be time-dependent to acquire/contribute to features of the disease, including hypertrophy. Genes regulating heme or hypertrophy are differentially expressed in pre-clinical conditions of hypertrophy but H9c2 cells are not a reliable model of hypertrophy for hypothesis-testing.