The kinetics and apoptotic profile of circulating endothelial cells in autologous hematopoietic stem cell transplantation in patients with lymphoproliferative disorders

In neoplastic disorders, endothelial cells take part in tumor progression and also influence the recovery of hematopoiesis after high-dose chemotherapy. Measurements of circulating endothelial cells (CEC), their subsets and kinetics were taken in patients with lymphoid malignancies (37 multiple myeloma, ten lymphoma) during autologous hematopoietic stem cell transplantation (HSCT). CEC were evaluated by four-color flow cytometry at different time points. Additionally levels of angiopoietins 1 and 2 were evaluated by ELISA assay. The baseline number of CECs and their subsets in patients were higher than in the control group. The median CEC number dropped significantly after transplantation (from 9.5/μL to 6.2/μL, p < 0.001). Apoptosis of CECs 24 h after chemotherapy was enhanced in comparison to baseline values (median apoptotic CEC number 4.15/μL vs 3.1/μL; p < 0,001). The time for neutrophil engraftment was shorter for patients with a low apoptotic CEC count at baseline as compared to those with a high apoptotic CEC count (median time to engraftment 13 vs. 16 days respectively, p = 0.04). We observed an adverse correlation of progenitor CEC numbers measured 1 h after transplantation with the time to neutrophil engraftment (r = −0.49, p = 0.008). We also found a negative correlation between the number of CECs originating from microvessels measured 1 h after transplantation, and the time to neutrophil engraftment (r = −0.39, p = 0.04). Baseline angiopoietins 1 and 2 concentration did not influence the post-transplant regeneration time. CEC numbers significantly change during autologous HSCT. Our results suggest that progenitor CECs and CECs derived from microvessels both take part in successful engraftment.