Study of Eryptosis in Patients with Renal Disease

Abstract

Eryptosis (erythrocyte programmed cell death) is postulated to be related to the efficacy of erythropoietin (Epo) treatment in chronic kidney disease (CKD) patients. This project was undertaken to determine whether this is the case and if any other factors correlate with eryptosis levels. Red cell microparticle (RCMP) numbers in whole blood were determined as a measure of eryptosis, using flow cytometry adapted from previous methods. Further investigation was performed using a flow loop model involving perfusion of whole blood through intact tumour necrosis factor (TNF) treated and untreated human umbilical arteries. Contrary to expectations, fewer RCMP were observed in CKD patients compared to controls (p=0.0167). Weak positive correlations were found between RCMP numbers and both CRP levels (p=0.0362) and Epo dose (p=0.0014) in the patient group. These results suggest erythrocytes in CKD patients undergo less eryptosis than in control subjects. In vitro investigations imply that erythrocytes in patients are less susceptible to the impact of flow stress and TNF treated endothelium than controls, corroborating this argument. When patients receiving Epo were compared to patients not receiving Epo there were no significant differences in RCMP numbers under all flow conditions. Further investigations are required, including the recruitment of more Epo hyporesponsive patients. This study highlighted the need for better standardisation of methods for measuring not only RCMP, but eryptosis in general, as well as better definitions of RCMP populations.