Background. Decreased production of erythropoietin (EPO) is a major cause of anemia associated with chronic kidney disease (CKD). Treatment with recombinant human EPO (rHuEPO) improves patients` quality of life and survival, yet, there is a marked variability in response to rHuEPO. At present, there is no available laboratory test which can evaluate responsiveness to EPO treatment. The aim of the present study was to exploit an in vitro bioassay for estimating the inhibitory effect of uremic environment on EPO-dependent erythroid cell proliferation.
Methods. EPO-dependent human erythroleukemia cells (UT-7) were incubated with exogenous EPO (2u/ml) and sera obtained from 60 pediatric patients (age 1-23 years). Three groups were studied: 1) 12 children on dialysis (4 peritoneal, 8 hemodialysis), 2) 28 patients with CKD1-5 (not on dialysis) and 3) 20 healthy children.
Results. Sera from dialysis patients inhibited UT-7 cell growth in comparison to the CKD group and healthy controls at 48 hours (p=0.003 and p=0.04, respectively) and at 72h (p=0.02 and p=0.07, respectively). In 18 patients treated with rHuEPO, a significant inverse correlation was found between the EPO resistance index and cell proliferation at 48 (p=0.007, r=-0.63) and 72 hours (p=0.03, r=-0.52).
Conclusions. Our findings support the presence of erythropoiesis inhibitory substances in uremic sera. EPO/EPO-R dependent mechanisms may play a role in inhibiting erythropoiesis. The in vitro bioassay described herein may serve as an indicator of rHuEPO responsiveness and enable further investigation of underlying mechanisms of EPO resistance.
