Transcriptional and Free Radical Responses to LVAD Therapy

Abstract

Background: Myocardial recovery with Left ventricular assistant device (LVAD) therapy is dichotomous with some patients obtaining remission from end-stage heart failure whereas most require transplantation or remain on pump support long term. Our goal was to determine transcriptional and free radical responses to LVAD treatment. Methods: Tissues were collected from patients before and after LVAD placement in non-ischemic dilated cardiomyopathy patients (n=14) along with controls (n=3). RNA sequencing (RNASeq) analysis quantified transcriptional profiles by using a custom targeted panel of heart failure related genes on the PGM sequencer. The differential expression analysis between groups was conducted using edgeR (Empirical analysis of digital gene expression data in R) package in Bioconductor. Ingenuity Pathway Analysis (IPA) was carried out on differentially expressed genes to understand the biological pathways involved. Electron Paramagnetic Resonance (EPR) Spectroscopy was utilized to measure levels of free radicals in whole blood collected pre- and post-LVAD implantation (n=16). Results: 35 genes were differentially expressed in pre-LVAD failing hearts compared to controls. In response to LVAD therapy, only Pyruvate dehydrogenase kinase 4 (PDK4) and period circadian protein homolog 1 (PER1) were altered with 34 heart failure related genes still differentially expressed post-LVAD compared to controls. IPA showed that DNA methylation-related genes were upregulated in both pre- and post-LVAD and was persistent with a Z-score of 2.00 and 2.36 for DNA Methyltransferase 3A (DNMT3A) and DNA methyltransferase 3B (DNMT3B), respectively. Inhibition of micro RNA21 (mir21) was also significant on pathway analysis in the post-LVAD population with a Z-score of -2.00. Levels of free radicals in blood of pre- and post-LVAD patients did not change significantly. Conclusion: LVAD therapy does not reverse many of the transcriptional changes associated with heart failure. Persistent changes in gene expression may be related to ongoing oxidative stress, continued DNA methylation, or changes in metabolism. PDK4 is a key regulator of glucose metabolism and its increased expression by LVAD therapy inhibited pyruvate metabolism.