BackgroundIn vitro proliferative and differentiation potential of mesenchymal stromal cells generated from CD271 + bone marrow mononuclear cells (CD271-mesenchymal stromal cells) has been demonstrated in several earlier and recent reports. In the present study we focused, in addition to proliferative and differentiation potential, on in vitro and in vivo immunosuppressive and lymphohematopoietic engraftment-promoting potential of these mesenchymal stromal cells compared to bone marrow-derived mesenchymal stromal cells generated by plastic adherence (plastic adherence-mesenchymal stromal cells). Design and MethodsWe set up a series of experimental protocols in order to determine the phenotype of CD271-mesenchymal stromal cells, and their clonogenic, proliferative, differentiation and immunosuppressive potential. The potential of CD271-mesenchymal stromal cells to improve the engraftment of CD133 + hematopoietic stem cells at co-transplantation was evaluated in immunodeficient NOD/SCID-IL2Rg null mice. ResultsIn vitro studies demonstrated that CD271-mesenchymal stromal cells differentiate along adipogenic, osteogenic and chondrogenic lineages (trilineage potential), produce significantly higher levels of cytokines than plastic adherence-mesenchymal stromal cells, and significantly inhibit the proliferation of allogeneic T-lymphocytes in mixed lymphocyte reaction assays. Elevated levels of prostaglandin E2, but not nitric monoxide, mediated the majority of this immunosuppressive effect. In vivo studies showed that CD271-mesenchymal stromal cells promoted significantly greater lymphoid engraftment than did plastic adherence-mesenchymal stromal cells when co-transplanted with CD133 + hematopoietic stem cells at a ratio of 8:1 in immunodeficient NOD/SCID-IL2Rg null mice. They induced a 10.4-fold increase in the number of T cells, a 2.5-fold increase in the number of NK cells, and a 3.6-fold increase in the number of B cells, indicating a major qualitative difference between these two mesenchymal stromal cell populations. ConclusionsOur results indicate that CD271 antigen provides a versatile marker for prospective isolation and expansion of multipotent mesenchymal stromal cells with immunosuppressive and lymphohematopoietic engraftment-promoting properties. The co-transplantation of such cells together with hematopoietic stem cells in patients with hematologic malignancies may prove valuable in the prevention of impaired/delayed T-cell recovery and graft-versus-host disease.Key words: T-cell recovery, graft-versus-host disease, MSC.Citation: Kuçi S, Kuçi Z, Kreyenberg H, Deak E, Pütsch K, Huenecke S, Amara C, Koller S, Rettinger E, Grez M, Koehl U, Henschler R, Tonn T, von Laer D, Klingebiel T, and Bader P. CD271 antigen defines a subset of multipotent stromal cells with immunosuppressive and lymphohematopoietic engraftment-promoting properties. Haematologica. 2010;95:651-659. doi:10.3324/haematol.2009 This is an open-access paper. © F e r r a t a S t o r t i F o u n d a t i o n CD271 antigen defines a subset of m...

The novel immunosuppressant FTY720 activates sphingosine 1-phosphate receptors (S1PRs) that affect responsiveness of lymphocytes to chemokines such as stromal cell-derived factor 1 (SDF-1), resulting in increased lymphocyte homing to secondary lymphoid organs. Since SDF-1 and its receptor CXCR4 are also involved in bone marrow (BM) homing of hematopoietic stem and progenitor cells (HPCs), we analyzed expression of S1PRs and the influence of FTY720 on SDF-1/ CXCR4-mediated effects in human HPCs. By reverse transcriptase-polymerase chain reaction (RT-PCR), S1PRs were expressed in mobilized CD34 ؉ HPCs, particularly in primitive CD34 ؉ /CD38 ؊ cells. Incubation of HPCs with FTY720 resulted in prolonged SDF-1-induced calcium mobilization and actin polymerization, and substantially increased SDF-1-dependent in vitro transendothelial migration, without affecting VLA-4, VLA-5, and CXCR4 expression. In nonobese diabeticsevere combined immunodeficient (NOD/ SCID) mice, the number of CD34 ؉ /CD38 ؊ cells that homed to the BM after 18 hours was significantly raised by pretreatment of animals and cells with FTY720, tending to result in improved engraftment. In addition, in vitro growth of HPCs (week-5 cobblestone area-forming cells [CAFCs]) was 2.4-fold increased. We conclude that activation of S1PRs by FTY720 increases CXCR4 function in HPCs both in vitro and in vivo, supporting homing and proliferation of HPCs. In the hematopoietic microenvironment, S1PRs are involved in mi IntroductionHoming of hematopoietic stem and progenitor cells (HPCs) to the bone marrow is an active and rapid process that takes place less than one day after transplantation, as demonstrated in the nonobese diabetic-severe combined immunodeficient (NOD/SCID) mouse model 1 as well as in recent in vivo tracking experiments using a bioluminescence technique. 2 In addition to adhesion molecules, proteolytic enzymes, and cytokines, especially chemokines such as stromal cell-derived factor 1 (SDF-1, CXCL12) are involved in HPC trafficking. CXCR4, the receptor for SDF-1, is expressed on HPCs and plays a central role in both progenitor cell homing and mobilization. [3][4][5][6][7][8][9] Blocking of CXCR4 with monoclonal antibodies has been shown to reduce homing of transplanted human progenitors to the bone marrow of NOD/SCID mice. 3 In the adult human bone marrow, SDF-1 was found to be expressed particularly by endothelial cells and along the endosteum region, suggesting SDF-1 mediates both early steps of HPC homing and final lodgement of stem cells in the niches of the bone marrow microenvironment. 10 Stimulation of CXCR4 by SDF-1 also activates adhesion molecules (eg, VLA-4) important for the homing process and may modulate proliferation of progenitors and stem cells. [11][12][13] In addition, there is indirect evidence that the SDF-1/ CXCR4 interaction is important for stem cell homing after transplantation in humans, since the migratory capacity of human progenitor cells in response to SDF-1 is correlated with hematopoietic recovery after stem cell tra...

AC133 (CD133) is a highly conserved antigen expressed on hematopoietic stem cells with unknown function. In order to further characterize CD133(+) progenitor cells, we purified CD133(+) stem cells using the method of magnetic activated cell sorting (MACS) from healthy adult volunteers mobilized with granulocyte colony-stimulating growth factor (G-CSF) to a mean purity of 94%. The purified CD133(+) cells highly engrafted NOD/SCID mice. In addition, unseparated mononuclear cells or CD133(+) stem cells isolated from the bone marrow of transplanted NOD/SCID mice gave rise to engraftment of secondary recipients. Upon ex vivo culture of purified CD133(+) cells with FLT3/Flk2 ligand (FL) and interleukin-6 (IL-6), a plastic-adherent cell population could be observed after 6 weeks in culture. These adherent cells did not express CD34 or CD133 antigens on their surface, nor did they express markers for endothelial, mesenchymal, or dendritic cells. After incubation of these adherent cells with stem cell factor (SCF), non-adherent cells were observed which partially co-expressed CD133, but were negative for CD34. These nonadherent CD34(-) cells showed a high engraftment capacity in NOD/SCID mice. From our results, we conclude that CD133 might be a marker of early progenitors with a high NOD/SCID engraftment potential. The fact that CD133(+) hematopoietic progenitors can give rise to an adherent population which is CD133(-) and CD34(-) and that these cells can again give rise to a CD133(+)CD34(-) stem cell population with high NOD/SCID engraftment potential indicates the plasticity of hematopoietic precursors. CD133(+) stem cells might be useful for research and for clinical application.

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