Persistence of recipient-type endothelium after allogeneic hematopoietic stem cell transplantation

The possibility that allogeneic hematopoietic stem cell transplantation performed across the ABO blood group-barrier is associated with an increase of graft-versus-host disease, in particular endothelial damage, has not been elucidated so far. For this reason, we investigated the level of endothelial cell chimerism after allogeneic hematopoietic stem cell transplantation in order to delineate the role of hematopoietic stem cells in endothelial replacement. The frequency of donor-derived endothelial cells was analyzed in 52 hematopoietic stem cell transplant recipients, in 22 normal skin biopsies, in 12 skin samples affected by graft-versus-host disease, various tissues from five autopsies and four secondary solid tumors by ABH immunohistochemistry, XY fluorescence in situ hybridization and short tandem repeat analysis of laser captured endothelial cells. Skin biopsies from two patients transplanted with minor ABO-incompatible grafts (i.e. O in A) showed 3.3% and 0.9% H antigen-positive donor-derived endothelial cells by ABH immunohistochemistry. Tumor biopsies from two recipients showed 1.2% and 2.5% donor-derived endothelial cells by combined immunohistochemistry/ fluorescence in situ hybridization. All other skin samples, heart, liver, bone-marrow, and tumor tissues failed to reveal donor-type endothelial cells up to several years after ABO-incompatible hematopoietic stem cell transplantation. Endothelial cell replacement by bone marrow-derived donor cells after allogeneic hematopoietic stem cell transplantation is a rare event. It does not seem to represent a major mechanism of physiological in vivo blood vessel formation, tumor neoangiogenesis, vascular repair after graft-versus-host disease episodes or acceptance of ABO-incompatible grafts.