Alterations of circulating endothelial cells after apheresis in patients with sickle cell disease: a potential clue for restoration of pathophysiology.

Objectives: The potential influence of automated red cell exchange (ARCE) on endothelial activation is not well established. This study was intended to assess whether ARCE influences circulating endothelial cells (CECs) in patients with sickle cell disease.

Background: Automated red cell exchange (ARCE) has been used to protect the patient from complications of sickle cell disease. However, the expected benefits vary in different patients. CECs reflect endothelial activation. We hypothesize that suppression of endothelial activation may be an important mechanism of ARCE.

Methods: The study included 20 patients with sickle cell disease who underwent 30 apheresis procedures. We used flow cytometry to directly compare pre- and post-apheresis CEC number (prior to ARCE and 5 days after ARCE) during the steady state and painful crisis. We also determined if independent variables (the level of plasma nitrite concentration, the percentage of circulating hemoglobin S, and painful crisis) significantly contributed to the CEC level.

Results: The mean CEC number decreased (P = 0.04), while progenitor CECs did not change in patients with sickle cell disease after ARCE compared with pre-ARCE values (P>0.05). Clinical factors such as the volume of replacement fluid and the citrate infusion rate did not correlate with post-apheresis CECsand progenitor CEC numbers. The independent variables were not significantly associated with CEC and progenitor CEC numbers.

Conclusions: ARCE can alter the CEC number, suggesting the possibility of suppression of endothelial activation. This may highlight the efficacy of ARCE for prevention or management of sickle cell vaso-occlusive crisis.