Epigenetic modulation of tenascin C in the heart: implications on myocardial ischemia, hypertrophy and metabolism

BACKGROUND Tenascin C (TN-C) is considered to play a pathophysiological role in maladaptive left ventricular remodeling. Yet, the mechanism underlying TN-C-dependent cardiac dysfunction remains elusive. METHOD The present study was designed to investigate the effect of hypoxia and hypertrophic stimuli on TN-C expression in H9c2 cells and its putative regulation by epigenetic mechanisms, namely DNA promoter methylation and microRNAs. In addition, rats subjected to myocardial infarction (MI) were investigated. H9c2 cells were subjected to oxygen and glucose deprivation; incubated with angiotensin II (Ang II); or human TN-C (hTN-C) purified protein. Hypertrophic and fibrotic markers, TN-C promoter methylation as well as mir-335 expression were assessed by reverse transcription and quantitative polymerase chain reaction while TN-C protein levels were assessed by ELISA. RESULTS Tn-C mRNA expression was markedly increased by both oxygen and glucose deprivation and Ang II (P < 0.01, respectively). In addition, Ang-II-dependent TN-C upregulation was explained by reduced promoter methylation (P < 0.05). Cells treated with hTN-C displayed upregulation of Bnp, Mmp2, β-Mhc, integrin α6 and integrin β1. Furthermore, hTN-C treated cells showed a significant reduction in adenosine monophosphate and adenosine triphosphate levels. In vivo, plasma and myocardial TN-C levels were increased 7 days post MI (P < 0.05, respectively). This increment in TN-C was accompanied by upregulation of mir-335 (P < 0.01). In conclusion, both hypoxic and hypertrophic stimuli lead to epigenetically driven TN-C upregulation and subsequent impairment of cellular energy metabolism in cardiomyoblasts. CONCLUSION These findings might enlighten our understanding on maladaptive left ventricular remodeling and direct towards a strong involvement of TN-C.