Irradiation Is an Early Determinant of Endothelial Injury During Hematopoietic Stem Cell Transplantation

Objective. We investigated the degree and the time course of endothelial injury in mice pretreated with lethal or reduced-intensity irradiation administered before transplantation. Materials and Methods. Six- to eight-week-old female mice were randomly allocated into three groups: lethal-intensity irradiation (8.5 Gy, group 1), reduced-intensity irradiation (5,0 Gy, group 2), or nonirradiated controls (group 3). After conditioning, circulating endothelial cells (CD31(+), CD133(-), and CD45(low)) and peripheral blood CD4(+) or CD8(+) T-lymphocyte subpopulations were enumerated using flow cytometry at various times. The morphologic changes in endothelium were examined at phase-contrast light microscopy. Results. Circulating endothelial cells showed an earlier and higher peak in the lethal irradiation group compared with the reduced-intensity Irradiation group, Which exhibited a protean elevation in cell numbers. There were no visible histopathologic changes during the early stage of endothelial damage. Conclusions. Lethal and reduced doses of irradiation induced endothelial injury ill a dose-dependent manner. Endothelial damage may occur before graft-vs-host disease and its related complications.