#2605 Evaluation of cardiac fetal gene program in experimental uremia

Abstract

Abstract Background and Aims Heart failure (HF) and uremia share several potent cardiac hypertrophic stimuli such as wall stress, sympathetic activation, renin angiotensin system activation and oxidative stress. In heart failure, induction of fetal gene program is one of the major processes through which such stimuli lead to progressive pathological hypertrophy and myocardial dysfunction. The fetal genes are activated by the transcription factor, myocyte enhance factor 2 (MEF2) which is a downstream target of the Ca++- Calmodulin Dependent Kinase II (CAMKII) pathway. The CAMKII pathway has been shown to be the major transduction pathway of the hypertrophic stimuli in HF [1, 2]. We hosphorzed that such mechanisms are also at play in uremic cardiomyopathy and tested the hypothesis in a rodent model of experimental uremia. Method Wistar rats (n = 18) had subtotal nephrectomy (STNx) or sham surgery (sham) and were followed up for 10 weeks. In vivo and in vitro cardiac assessments were performed. Cardiac tissue was extracted, and protein expression of CAMKII and hosphor-CAMKII were quantified using immunoblotting. Protein expression of MEF2 and its target fetal genes were also studied. Histological analyses were performed to quantify myocardial fibrosis. Data was analysed using an independent sample t-test with Welch's correction and expressed as mean± SEM. Results STNx resulted in higher echocardiographic left ventricular mass, heart weight to tibia length ratio and myocardial fibrosis in the STNx group (Fig. 1) demonstrating cardiac pathological hypertrophy. CaMKII signalling was activated and the expression of MEF2 was also increased following STNx (Fig. 1). There was trend towards increased expression of fetal genes (Fig. 1). However, the difference did not reach statistical significance. Conclusion The study shows that experimental uremia induces cardiac pathological hypertrophy along with activation of intracellular pathways involved in fetal gene induction. Further studies evaluating fetal genes at an earlier time course in the evolution of pathological hypertrophy will be worthwhile.