Ex Vivo Culture of Human Cord Blood Hematopoietic Stem/Progenitor Cells Adversely Influences Their Distribution to Other Bone Marrow Compartments after Intra-bone Marrow Transplantation

¹ Department of Hematology and Oncology, Mie University Graduate School of Medicine, Mie, Japan
² Blood Transfusion Service, Mie University Hospital, Mie, Japan

^* To whom correspondence should be addressed. E-mail: koishi{at}clin.medic.mie-u.ac.jp.

	Abstract

Intra-bone marrow injection is a novel strategy for hematopoietic stem cell transplantation. Here, we investigated whether ex vivo culture of cord blood hematopoietic stem/progenitor cells influences their reconstitution in bone marrow after intra-bone marrow transplantation. Freshly isolated AC133⁺ cells or cells derived from AC133⁺ cells cultured with cytokines (stem cell factor, flt-3 ligand and thrombopoietin) for 5 days were injected into the bone marrow of the left tibia in irradiated NOD/SCID mice. In the bone marrow of the injected left tibia, the engraftment levels of human CD45⁺ cells at 6 weeks after transplantation did not differ considerably between transplantation of noncultured and cytokine-cultured cells. However, the migration and distribution of transplanted cells to the bone marrow of other noninjected bones were extremely reduced for cytokine-treated cells compared with noncultured cells. Similar findings were observed for engraftment of CD34⁺ cells. Administration of granulocyte colony-stimulating factor to mice after transplantation induced the migration of cytokine-cultured cells to the bone marrow of previously-aspirated bone but not to other intact bones. These data suggest that ex vivo manipulation of hematopoietic progenitor/stem cells significantly affects their migration properties to other bone marrow compartments after intra-bone marrow transplantation. Our data raise caution for future clinical applications of the intra-bone marrow transplantation method using ex vivo-manipulated hematopoietic stem cells.