Allogeneic Non-Adherent Bone Marrow Cells Facilitate Hematopoietic Recovery but Do Not Lead to Allogeneic Engraftment Stephan Fricke 1,2 *, Manuela Ackermann 3 , Alexandra Stolzing 1 , Christoph Schimmelpfennig 1 , Nadja Hilger 1 , Jutta Jahns 4 , Guido Hildebrandt 5 , Frank Emmrich 1,2,3 , Peter Ruschpler 1 , Claudia Po ¨ sel 1 , Manja Kamprad 1,2. , Ulrich Sack 1,2,3. 1 Fraunhofer Institute for Cell Therapy and Immunology (IZI), Leipzig, Germany, 2 Institute of Clinical Immunology and Transfusion Medicine, University of Leipzig, Leipzig, Germany, 3 Translational Centre for Regenerative Medicine, University of Leipzig, Leipzig, Germany, 4 Clinic for Radiation Therapy and Radiation Oncology, University of Leipzig, Leipzig, Germany, 5 Clinic for Radiation Therapy, University of Rostock, Rostock, Germany Abstract Background: Non adherent bone marrow derived cells (NA-BMCs) have recently been described to give rise to multiple mesenchymal phenotypes and have an impact in tissue regeneration. Therefore, the effects of murine bone marrow derived NA-BMCs were investigated with regard to engraftment capacities in allogeneic and syngeneic stem cell transplantation using transgenic, human CD4 + , murine CD4 2/2 , HLA-DR3 + mice. Methodology/Principal Findings: Bone marrow cells were harvested from C57Bl/6 and Balb/c wild-type mice, expanded to NA-BMCs for 4 days and characterized by flow cytometry before transplantation in lethally irradiated recipient mice. Chimerism was detected using flow cytometry for MHC-I (H-2D[b], H-2K[d]), mu/huCD4, and huHLA-DR3). Culturing of bone marrow cells in a dexamethasone containing DMEM medium induced expansion of non adherent cells expressing CD11b, CD45, and CD90. Analysis of the CD45 + showed depletion of CD4 + , CD8 + , CD19 + , and CD117 + cells. Expanded syngeneic and allogeneic NA-BMCs were transplanted into triple transgenic mice. Syngeneic NA-BMCs protected 83% of mice from death (n = 8, CD4 + donor chimerism of 5.862.4% [day 40], P,.001). Allogeneic NA-BMCs preserved 62.5% (n = 8) of mice from death without detectable hematopoietic donor chimerism. Transplantation of syngeneic bone marrow cells preserved 100%, transplantation of allogeneic bone marrow cells 33% of mice from death. Conclusions/Significance: NA-BMCs triggered endogenous hematopoiesis and induced faster recovery compared to bone marrow controls. These findings may be of relevance in the refinement of strategies in the treatment of hematological malignancies. Citation: Fricke S, Ackermann M, Stolzing A, Schimmelpfennig C, Hilger N, et al. (2009) Allogeneic Non-Adherent Bone Marrow Cells Facilitate Hematopoietic Recovery but Do Not Lead to Allogeneic Engraftment. PLoS ONE 4(7): e6157. doi:10.1371/journal.pone.0006157 Editor: Graham Pockley, University of Sheffield, United Kingdom Received February 11, 2009; Accepted June 15, 2009; Published July 7, 2009 Copyright: ß 2009 Fricke et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was supported in part by research funding from German Federal Ministry for Education and Research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors declare no competing financial interests. S.F. and A.S. delivered parts of this work as European Patent Application. * E-mail: stephan.fricke@izi.fraunhofer.de . These authors contributed equally to this work. Introduction Today, allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for many patients with hematological malignancies [1]. Bone marrow [2], peripheral mobilized stem cells [3] and umbilical cord blood [4] are the common sources for HSCT. Despite the use of highly sophisticated therapeutic approaches, HSCT is still associated with a considerable mortality caused by a number of complications such as graft versus host disease (GVHD) [5], infectious diseases [6], veno-occlusive disease [7], donor graft rejection [8], and relapses of the underlying diseases [9]. Therefore, the investigation of alternative therapeutic approaches including the use of new stem cell sources and the optimization of treatment strategies are still in need. Thus, mesenchymal stem cells (MSCs) are used in clinical hematopoietic stem cell transplantation to support hematopoi- esis. Previous studies indicate that co-transplantation of mesenchymal stem cells results in faster engraftment of hematopoietic cells [10,11]. MSCs as well as MSC derived cells provide growth factors essential for hematopoiesis [12–14]. These cells are a very promising stem cell type for transplan- tation because MSCs are easy available and modest regarding their requirements for in vitro expansion. Furthermore, MSCs show no spontaneous transformations [15] and are character- ized as highly adherent fibroblastic cells (counted as CFU-f) [16,17], which attach within 24 hours [16]. It has also been shown that there are other cells derived from CFU-f, which are able to transform into mesenchymal cells, but also into cells of other lineages [18]. PLoS ONE | www.plosone.org 1 July 2009 | Volume 4 | Issue 7 | e6157