mRNA Profiling for Myocardial Injury In Experimental Cardiac Arrest Models

Introduction: Cardiac arrest has a very poor prognosis and survival rate after restoration of spontaneous circulation (ROSC). Resuscitation techniques are one of the most significant contributors to the clinical outcome after cardiac arrest. Resuscitation aims for avoiding and/or alleviating the brain damage, myocardial function decline, and multi-organ failure due to ischemia/hypoxia during the event of cardiac arrest. Despite clinical research efforts to answer questions related to resuscitation techniques and the value of different resuscitation strategies, the 30-day mortality after an event of cardiac arrest is still high. Some of the great advancement of resuscitation techniques are Extracorporeal Life Support (ECLS) and Extracorporeal Membrane Oxygenator (ECMO) which provide means for restoring tissue perfusion, oxygenation, drug delivery and temperature control until cardiac function is restored. Several protocols that used ECLS and ECMO for neuroprotection and cardioprotection have been tested, including hypothermia and supplementation of different drugs. However, the results of such studies are not conclusive which can be attributed to lack of understanding of the molecular events associated with these protocols. Therefore, in this study we will investigate the genetic and molecular remolding associated with two models of post cardiac arrest resuscitation. Scope of the study: This study was conducted to assess the genetic and molecular changes associated with two different models of resuscitation in the sitting of cardiac arrest. First model is hypothermic arrest followed by different rate of rewarming. Second model is a cardiac arrest followed by cardiopulmonary bypass (CPB) resuscitation with NO supplementation using ECMO. This study is conducted to fulfill the requirements for doctoral degree in cardiovascular sciences at the university of Verona. Materials and methods: Male Sprague Dawley rats weighing around 400±50 g were used. Two main models of resuscitation in the sitting of cardiac arrest were used; the model of hypothermic cardiac arrest followed by different rates of rewarming using ECLS, and the model of experimental cardiac arrest and resuscitation using NO supplied through the ECMO. Cardiac tissues were collected after the experiment for molecular analysis. RNA sequencing was used to detect transcriptomic changes. The apoptosis was assessed using Tunnel assay Results: First our results highlight the effect of different rates of rewarming post cardiac arrest. Slow rewarming showed a significant lower level of myocardial apoptosis compared to rapid rewarming. Rapid rewarming was associated transcriptomic derangement involving pathways related to lipid metabolism, inflammatory and apoptotic pathways, and calcium handling. Second our results showed that resuscitation using nitric oxide (NO) has a deleterious effect of on the myocardium as indicated by a significant increase in the apoptosis. The known beneficial effects of NO include inhibition of the sympathetic signaling, and smooth muscle relaxation couldn’t overcome the complex metabolic derangement, and profound activation of inflammatory and apoptotic pathways. Conclusions: Our study explained the beneficial effect of the slow rewarming over the fast rewarming after hypothermic arrest at the molecular and genetic level. We also challenged the idea of using NO as a protective agent during resuscitation. NO has a deteriorating effect on the myocardium. This study highlights the genetic remodeling associated with resuscitation in the sitting of cardiac arrest which would guide clinical decisions. In addition, this study spots the light on the possible molecular pathways that could be targeted to improve resuscitation process post-cardiac arrest and would results in improving the survival rate post-cardiac arrest.