Evaluation of Circulating Endothelial Cells (CEC) as a Marker of Endothelial Damage in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation (Allo-HSCT): Correlation With the Occurrence of Graft-versus-Host Disease (GvHD)

The endothelial damage is a characteristic common to several complications of vascular origin that may occur in the course of allo-HSCT (GVHD, IPS, VOD, TMA). The diagnosis of vascular complications represents an interesting challenge, but unfortunately limited by the fact that the markers of endothelial damage are extremely scarce. In particular, the plasmatic dosage of von Willebrand factor, thrombomodulin and adhesion molecules generated results difficult to use for a potential application for routine diagnostics for the high degree of non-specificity and the potential influence on the assay by co-morbid conditions related to the recipient. Much more promising methods appear to be those that are based on the evaluation of microparticles derived from endothelial cells (EMP) or the direct counting of circulating endothelial cells (CEC). Recently, the EMP were assessed by flow cytometry (annexin V-FITC and anti-CD62-PE) in 19 patients undergoing allo-HSCT, showing an increase in patients with acute GvHD grade ≥ I, compared to patients that did not display GvHD. In addition, the evaluation of EMP did not appear to be affected by the radio-chemotherapy conditioning regimen. This method is, however, burdened with a procedural complexity and a certain degree of non-specificity due to the fact that the microparticles can be released by endothelial cells as well as also from platelets, red blood cells and leukocytes.

Currently, the direct counting of the CEC seems to be the most reliable ways to assess the degree of endothelial damage. The finding of elevated numbers of CEC has been shown to reflect the extent of endothelial damage in numerous pathologies of autoimmune nature, but are still preliminary data in the course of allo-HSCT. Woywodt et al. demonstrated in patients with ANCA-positive vasculitis a correlation between the number of CEC and the degree of disease activity and response to treatment. Moreover, the number of CEC correlates, in patients undergoing renal transplantation, with the risk of organ rejection. In the course of allo-HSCT, the same authors have shown a correlation between the number of CEC and endothelial damage induced by radio-chemotherapy conditioning regimen. However, the lack of a standardized method, the use of manual procedures of immunoselection, the lack of consensus on the identification of CEC represent limiting factors for routine application.

The present study takes the form of a prospective study. The primary endpoint is the identification and enumeration of CECs in peripheral blood of patients with hematological disorders undergoing allo-HSCT, as a function of endothelial damage. The secondary endpoint is to define the prognostic and predictive value of CEC counts changes on the diagnosis of GvHD and on the response to treatment.

Peripheral blood (PB) will be drawn before (T1, baseline) and at the end of the conditioning regimen (T2, pre-transplant), upon confirmation of hematopoietic recovery (T3, engraftment) and thereafter at onset of GVHD (GVHD T4) and one week after the start of steroid therapy (T5, post-GvHD) for the control of GvHD. All patients will also be checked for CEC at day + 28.

The peripheral blood for counting CEC will be collected, respectively, in the CellSave Preservative Tube (Veridex, J & J, USA), containing a preservative for the stabilization of the cells at room temperature, for counting with the CellSearch® System and in CBC tube containing K2EDTA, for counting by flow cytometry.