Transplantation of allogeneic or xenogeneic bone marrow within the donor stromal microenvironment

Successful engraftment of hematopoietic stem cells requires a supportive he matopoietic stromal microenvironment (HSM), Defects in the HSM associated w ith aplastic anemia, myelofibrosis, or caused by intensive ionizing radiati on and chemotherapy generally result in failure of bone marrow (BM) engraft ment. Transplantation of donor BM within donor HSM may therefore provide op timal conditions for allogeneic BM. transplantation. We have transplanted d onor hematopoietic cells together with their own HSM to improve acceptance of allogeneic or xenogeneic BM. The non-myeloablative treatment used induce d tolerance to murine allografts and provided conditions for the lifelong a cceptance of allogeneic HSM, Allogeneic BM transplanted within it's own HSM under the kidney capsule caused less graft-versus-host disease than BM tra nsplanted i.v. Tolerance in mice to xenogeneic (rat) HSM was less complete. Ectopic ossicles were small and contained fewer hematopoietic cells. Howev er, simultaneous transplantation of rat BM and HSM to preconditioned mice i mproved engraftment of rat BM compared with transplantation of BM alone. Do nor hematopoietic cells survived longer on their own HSM than on HSM of rec ipients.