title: Induction of mixed chimerism through transplantation of CD45-congenic mobilized peripheral blood stem cells after nonmyeloablative irradiation.
abstract: Clinical translation of the mixed-chimerism approach for inducing transplantation tolerance would be facilitated if mobilized peripheral blood stem cells (mPBSCs) could be used instead of bone marrow cells (BMCs). Because the use of mPBSCs for this purpose has not been investigated in nonmyeloablative murine protocols, we explored the engraftment potential of mPBSCs in a CD45-congenic model as a first step. After 2, 1.5, or 1 Gy of total body irradiation, CD45.1 B6 hosts received unseparated granulocyte colony-stimulating factor-mobilized CD45.2 B6 PBSCs or unseparated CD45.2 B6 BMCs. The same total cell numbers, or aliquots of mPBSCs and BMCs containing similar numbers of c-kit+ cells, were transplanted both with and without a short course of rapamycin-based immunosuppression (IS). Transplantation of mPBSCs induced long-term multilineage macrochimerism, but chimerism levels were significantly lower than among recipients of the same number of BMCs. Transplanting aliquots containing similar numbers of c-kit+ cells reduced the difference between mPBSCs and BMCs, but lower levels of chimerism were nonetheless observed in mPBSC recipients. Chimerism levels correlated more closely with the number of transplanted progenitor cells as determined by colony-forming unit assays. IS did not affect chimerism levels, indicating that the donor CD45 isoform or other minor disparities do not pose a major barrier to engraftment. Our findings indicate that under nonmyeloablative conditions, progenitor cells contained in mPBSCs have an engraftment capacity similar to progenitor cells from BMCs, allowing induction of lasting mixed chimerism with moderate cell numbers. On a cell-per-cell basis, unseparated BMCs have some advantages that may be minimized if the number of progenitor cells is equalized. These results are expected to facilitate the development of mPBSC-based allogeneic tolerance protocols.
authors.affiliation: Division of Transplantation, Department of Surgery, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Zvonimir
authors.initials: Z
authors.lastname: Koporc
authors.forename: Sinda
authors.initials: S
authors.lastname: Bigenzahn
authors.forename: Peter
authors.initials: P
authors.lastname: Blaha
authors.forename: Elahi
authors.initials: E
authors.lastname: Fariborz
authors.forename: Edgar
authors.initials: E
authors.lastname: Selzer
authors.forename: Megan
authors.initials: M
authors.lastname: Sykes
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Muehlbacher
authors.forename: Thomas
authors.initials: T
authors.lastname: Wekerle
mesh_terms: D000818:Animals; D005260:Female; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods; D017493:Leukocyte Common Antigens; D051379:Mice; D036102:Peripheral Blood Stem Cell Transplantation / Q000379:methods; D018183:Transplantation Chimera; D019172:Transplantation Conditioning / Q000379:methods; D014184:Transplantation, Homologous; D014916:Whole-Body Irradiation / Q000379:methods
chemical_list: D017493:Leukocyte Common Antigens