Circulating Endothelial Progenitor Cells and Their Relation to Thrombosis in Paroxysmal Nocturnal Hemoglobinuria and Aplastic Anemia.

Thrombosis is a leading cause of morbidity and mortality in paroxysmal nocturnal hemoglobinuria (PNH). Multiple factors are responsible for the thrombotic tendency in these patients. Endothelial progenitorcells (EPCs) originate from primitive hematopoietic stem cells. The EPC count is considered indicative of potential damage and restoration capacity in vascular disease; lower EPC counts are deemed as a risk factor in cardiovascular diseases. We aimed to investigate the count of circulating EPCs in PNH and aplastic anemia (AA) patients receiving eculizumab treatment or not receiving treatment and their relationship with thrombosis. Seventeen PNH patients, 18 AA patients, and 10 healthy volunteers were included in the study. The CD309, CD133, and CD34 antibodies were used to determine counts of circulating EPCs using flowcytometry. EPC levels were compared between the PNH, AA, and healthy control groups. Kolmogorov-Smirnov test. ANOVA, Kruskal-Wallis, and Mann-Whitney U testswereperformedto analyze the quantitative data, while χ2 testing was performed to analyze the qualitative data. Therewasnosignificantdifference in EPC levelsbetweenpatientswithandwithout a history of thrombosis (P > 0.05). Further, therewasnosignificantdifference in thelevels of EPCsbetweenthe AA and PNH groups (P  > 0.05). However, there was a significant positive correlation between levels of EPCs and lactate dehydrogenase (LDH) in multivariate analysis (P < 0.05). The study findings suggest that hemolysis promotes vascular endothelial and new blood vessel formation. Increased EPCs in PNH may indirectly indicatevascular endothelial damage in PNH. © Indian Society of Hematology and Blood Transfusion 2021.