Mature Circulating Endothelial Cells and Progenitors in Patients with Chronic Gvhd

Abstract 4700

Acute and chronic graft-versus-host disease are a common complication of allogeneic stem cell transplantation. In animal models acute GVHD (aGVHD) is associated with increased neovascularization and number of circulating endothelial cells (CECs), while patients with sclerodermatous chronic GVHD (cGVHD) show a significant decrease in the number of circulating endothelial progenitor cells (EPCs) in peripheral blood as compared to patients with non sclerodermatous cGVHD or controls.

In an attempt to evaluate the role of CECs and EPCs in patients with cGVHD, we analysed a total of 15 patients affected by hematological malignancies (3 Non-Hodgkin Lymphoma, 4 Hodgkin Disease, 4 Multiple Myeloma, 2 Myelodisplastic Syndrome, 2 Chronic Lymphocitic Leukemia) having undergone allogeneic stem cell transplantation following reduced intensity conditioning. Donors were HLA identical in 14 patients (12 sibling and 2 matched unrelated donors) and HLA aploidentical in 1.

Acute GVHD and cGVHD were defined on the basis of time of manifestation, ≤100 days for aGVHD and >100 days for cGVHD. At the time of the blood sample collection, 8 patients, median age 42 years (28-51), with a median time after transplant of 177 days (21-1373), had no evidence of GVHD; of those 5/8 were evaluable for aGVHD and cGVHD, 2 only for aGVHD; 4/8 were on post-transplant calcineurin inhibitors immunosuppressive therapy; 7 other patients, median age 51 years (38-64), with a median time after transplant of 844 days (314-1779), were all evaluable for acute and cGVHD and had evidence of cGVHD as follows: sclerodermatous in 3 patients requiring systemic immunosuppressive therapy, oral mucosa lichen in 1 patient taking oral corticosteroid and cutaneous erythematous and dischromic cGVHD in the other 3 patients, with only 1 patient on systemic immunosuppressive therapy. Viable and apoptotic CECs and EPCs were evaluated by six color flow cytometry (Mancuso et al, Clin Cancer Res, 2009). Briefly, CECs were defined as DNA+CD45-CD31+ CD146+, EPCs as CD45- CD34+. The combination of Syto16 and 7-AAD was used to discriminate between viable (syto16bright/7-AAD-) and apoptotic (syto16weakly pos/7-AAD+) endothelial cells, and to exclude from analysis, platelets and endothelial macroparticles.

The results, expressed as median of cells/mL, are summarized in the following table:

These preliminary data indicate a significant reduction in apoptotic circulating mature endothelial cells, likely reflecting a poor vascularization of multiple organs and tissues targeted by cGVHD and a trend towards a decreased number of EPCs in patients with cGVHD. A multicentric study is now planned to confirm these hypotheses and investigate a possible predictive/prognostic role of CEC and EPC counts in cGVHD.