Non-myeloablative stem cell transplantation in newly established donor stromal microenvironment for facilitation of hematopoietic reconstitution

Following allogeneic stem cell transplantation (SCT) migrate to the hematopoietic microenvironment in bones, but the stroma remains of host origin. We hypothesized that replacement of host with donor stromal microenvironment supporting and regulating hematopoiesis may enhance engraftment and differentiation of bone marrow cells (BMC), especially in patients with myelofibrosis. Our earlier work suggested that SCT with donor stromal microenvironment modifies GVHD. We have recently documented that transplantation of BMC mixed with demineralized bone matrix (DBM) may be sufficient for formation of new bone and hematopoietic mircoenvironment. Tested in rats, implantation of DBM/BMC composite intraosseously or under the kidney capsule resulted in new bone formation containing donor hematopoietic tissue. Based on the murine data, we introduced the use of intra-osseous transplantation of DBM/BMC for patients with existing or anticipated marrow failure, such as myelofibrosis, following non-myeloablative conditioning (NST). Our 1st patient was 54 yrs old woman with RAEB-T and myeloid fibrosis, with no hematologic reconstitution following NST (fludarabine, busulfex & ATG) until week +4. Intraosseous (femora and pelvis) transplantation of DBM/BMC was accomplished with no further conditioning from the same donor, assuming the problem was engraftment failure rather than rejection. Early 3-lineage reconstitution of donor (male) cells was confirmed within one week. Currently, the patient is more than 2 years out with mild chronic GVHD, with 100 percent normal male karyotype. Bone biopsy, laser capture microdissection and PCR revealed 100 percent donor-derived blood cells, stroma and bone cells. Two additional patients underwent successful intra-osseous DBM/BMC transplantation into one femur following NST, with fast 3-lineage engraftment. Procedures were uneventful. All patients are disease free, with 100 percent donor type cells. Considering our experimental and clinical experience, intra-osseous transplantation of DBM/BMC may provide a new tool for enhancing allogeneic hematopoietic reconstitution, especially for patients with myelofibrosis.