The Role of Rheology and Transfusion on Microvascular Thrombosis in Sepsis

PROJECT SUMMARY/ABSTRACT Sepsis affects nearly 50 million people worldwide each year and the mortality rate for patients admitted to the intensive care unit (ICU) is between 20 and 30%. There is clinical need to understand this pathophysiology which causes the organ failure and high rates of mortality in order to identify efficacious therapies. Decreased microvascular perfusion and endothelial cell (EC) injury are known to be involved but the mechanisms underlying them remain incompletely studied. EC injury in sepsis promotes a change to a pro-adhesive, pro- thrombotic cell phenotype. Disturbances in microvascular rheology – the biophysical behavior of blood in the smallest blood vessels as a result of red blood cell (RBC) aggregation and cell membrane deformability – have been observed in patients with sepsis and contribute to reduced microvascular perfusion. Given the EC layer’s mechanosensitive nature, the central hypothesis for this project states that changes in microvascular rheology contribute to EC injury and are predictive of organ failure and mortality in patients with sepsis. It is further proposed that through manipulation of patient rheology with RBC and plasma transfusion we can augment this injury specifically to improve perfusion and reduce microvascular thrombosis. Using state of the art microfluidics assays, this project will characterize how RBC aggregation and membrane deformability affect EC expression of adhesion molecules and anti-coagulant factors using whole blood samples from patients admitted to the ICU with sepsis (Aim 1.1). Clinical correlates of these experiments will be defined through unbiased and supervised class analysis modeling using machine learning (ML) approaches to determine the impact of rheology (Aim 1.2). An array of RBC and plasma transfusions will be performed to assess the impact on measured rheologic parameters of patient samples and identify optimal transfusion strategies to reduce the risk of micro-thrombosis formation (Aim 2). The expected finding from this project is that blood from patients showing increased RBC aggregation and reduced RBC membrane deformability will induce greater levels of EC injury and class analysis will identify a group of patients with a hyperinflammatory and disturbed rheology endotype as a high risk group for severe organ injury and mortality. It is also expected that the patient samples which improve in rheologic measurements with transfusion will also demonstrate reduced microvascular thrombosis burden. The long term goal of this project is to facilitate the principal investigator’s career towards becoming an independently funded physician scientist studying microvascular physiology and thrombosis in pulmonary and critical illness. The short term goal is for the principal investigator to gain expertise in EC transcriptomics, transfusion and coagulation medicine, and ML approaches to answer complex clinical questions.