Removal of Cytokines With Cytosorbents After Inflammatory Response Reaction During Cardiac Surgery and Association of Endothelial Progenitor Cells

Mechanical cardiovascular support procedures are used as part of cardiac surgery. Here, heart-lung machines (HLM) and miniaturized systems such as ECMO (extracorporeal membrane oxygenation) are used to replace cardiac and/or pulmonary function. Contact with non-physiologic artificial surfaces can induce a generalized 'sterile' inflammatory syndrome called SIRS (Systemic Inflammatory Response Syndrome). During SIRS, proinflammatory cytokine release occurs due to complement activation. These massively released, diverse cytokines significantly influence the activation and release of endothelial progenitor cells (EPCs) from the bone marrow during extracorporeal circulation (ECC) and their long-term functionality.

The life-threatening complications of the so-called cytokine storm can potentially be avoided with the help of a cytokine adsorber (CytoSorb®), and the stabilization process after the hyperinflammatory phase can be promoted. However, it is unclear the quantitative and qualitative modification of the cytokine expression pattern by the use of the cytokine adsorber and its influence on the release of EPCs as well as on the clinical course of the patients. Although a therapy extension with cytokine adsorber has a positive impact on the reduction of cytokine levels in the blood, cytokine removal has not been investigated in direct correlation to EPCs.

These interactions are to be investigated within the scope of the proposed project.

This project is a pilot study with a translational science background to clarify the relationship between CD34-positive endothelial progenitor cells and cytokine release in the setting of ECCs using cytokine adsorber. Previous studies have shown a positive association between increased cytokine levels and the number of circulating endothelial progenitor cells. To date, it has not been investigated how this correlation or association changes with the use of cytokine adsorbers. Therefore, due to the specificity of targeted cytokine removal, the findings obtained here may provide essential insights in basic clinical research that could be applied to clinical issues and decision-making processes in the future. Due to the increasingly important role of extracorporeal circulatory support systems, detailed knowledge of the relationship between systemic inflammation and endothelial progenitor cell activation during their use will be increasingly important in the future.

The current project aims to investigate whether an association between the inflammatory response during and after cardiac surgery and the number of stem cells (EPCs) continues to exist when the cytokine adsorber (CytoSorb®) is applied and whether and how the adsorber can influence the functionality, migratory capacity, and differentiation of stem cells. We assume that under these conditions, a direct correlation of EPCs with inflammation does not exist, so a modulation of the SIRS (Systemic Inflammatory Response Syndrome) clinically observed by us could be absent. In addition, we will investigate whether a correlation between the number of circulating endothelial progenitor cells (CD 34+ cells) and the concentration of cytokines can be observed to make a predictive statement regarding the clinical expression of inflammation.