TRANSCRIPTOMIC ANALYSIS IN SEPTIC SHOCK PATIENTS

Introduction Septic shock, also defined as distributive shock, is a complication of sepsis, characterized by pronounced hypotension, followed by anomalous distribution of blood at vessels, organs and tissues. The hemodynamic, cellular and metabolic alterations described in septic shock patients lead to a mortality that is at present around 40%. Septic shock patients develop dysfunctions or failure to multiple organs (MOF) but the molecular mechanisms triggering tissue injury remain largely undetermined and a specific treatment for septic shock is still not available. Aim This work is part of the European Project ShockOmics, a multicentric, prospective, observational study, whose aim is to identify with a multiscale approach, molecular biomarkers in septic shock patients who develop acute heart failure. The specific aim of the present Research project is to investigate the modifications induced by septic shock on transcriptional profile, using blood cells as RNA source. This investigation is performed at different timepoints starting from admission of the patient to the intensive care unit (ICU). Materials and Methods Septic shock patients were recruited in the ICUs of Geneva and Bruxelles University Hospitals, that are Partners of ShockOmics Project. Blood samples were collected in the acute phase of the disease at ICU admission (T1), after the appropriate pharmacological intervention (T2 ) and at steady state on day 7 of the ICU stay (T3). RNA was extracted from whole blood and RNA sequencing was used to evaluate the expression level of genes, long non coding RNAs and microRNAs. We explored the dataset using PCA and unsupervised hierarchical clustering and we identified differentially expressed genes and microRNAs across conditions. Gene Ontology analysis was used to identify relevant biological processes involved in shock. We identified microRNA regulatory targets with an in silico target prediction. Results We identified two main gene expression profiles corresponding to the acute phase of shock and to the condition of steady state. Between the acute phase of shock (day 1) and the steady state condition (day 7) we observed in patients at day 7 a downregulation of pathways of the innate immune response (Toll-like receptor and C-type lectin receptors pathways) and of acute inflammation (IL-1 receptor family and alarmins) and the upregulation in the same patients of genes of the adaptive immunity related to B and T lymphocytes activation. A transcriptional regulation was observed also for genes with antimicrobial function and protease activity and for genes involved in carbohydrate metabolism, lipid inflammatory pathway, transport of vesicles and protein synthesis. miR-125a-5p and miR-150-5p, with a predicted regulatory role in the MAPK pathway, and miR-193a-3p were differentially expressed in the acute and steady state condition. Conclusion We observed a significant modulation of multiple classes of genes involved in defense response to pathogens, immunity, inflammation and metabolism. From these results it appears that in septic shock a relevant change in the transcriptomic profile of blood cells is induced, in order to counteract the pathogens and as a consequence of the hemodynamic changes underlying the circulatory failure. The transcriptomic profile of septic shock patients showed inter patient variability reflecting the complexity of the shock condition and of the individual response to treatment. Specific signatures could turn out by combining clinical data and expression profile and could be used to better classify septic shock patients.