Mixed chimerism: Preclinical studies and clinical applications

AbstractTraditional approaches to allogeneic stem cell transplantation have relied on the use of toxic high-dose conditioning therapy to achieve allogeneic engraftment and control of underlying disease. Preclinical observations have shown that, for engraftment purposes, conditioning regimens can be reduced in intensity, resulting in reduced treatment toxicities. In preclinical canine studies, the use of potent pre- and postgrafting immunosuppression allowed for reduction in conditioning regimens and development of stable mixed chimerism. If these newer approaches using attenuated conditioning regimens can be successfully applied to human transplantation, an improved safety profile will allow potentially curative treatment of patients not currently offered such therapy. Mixed chimerism per se could prove curative of disease manifestation for various nonmalignant disturbances of the hematopoietic and immune systems. For patients with malignancy, infusion of additional donor lymphocytes may be needed to effectively treat underlying disease.Biol Blood Marrow Transplant 1999;5(4):192-203

Graft Failure after Allogeneic Hematopoietic Cell Transplantation

AbstractGraft failure is a significant complication following allogeneic hematopoietic cell transplantation (alloHCT). It may result from rejection caused by recipient T cells, natural killer (NK) cells, or antibodies. It is increased in HLA-mismatched grafts, unrelated grafts, T cell-replete transplants, sensitized patients, and in patients treated with reduced-intensity conditioning (RIC). In recipients of unrelated grafts, graft failure is increased in patients receiving major AB0 blood group mismatched transplants (P = .008). Recent data also suggest that donor-specific antibodies to CD34+/VEGFR-2+ cells may be involved in graft failure after alloHCT. Graft failure may be overcome by more intensified conditioning, increased cell dose, or more effective immunosuppression. With more frequent use of RIC, cord blood grafts and other HLA-mismatched transplants, graft failure is an increasing problem after alloHCT

Denileukin Diftitox as Prophylaxis against Graft-versus-Host Disease in the Canine Hematopoietic Cell Transplantation Model

AbstractDenileukin diftitox (Ontak) was evaluated in combination with methotrexate (MTX) for preventing acute graft-versus-host disease (GVHD) in dogs given 9.2 Gy of total body irradiation and DLA-nonidentical hematopoietic cell grafts. Six dogs were given denileukin diftitox 9 μg/kg/day intravenously (IV) on days 2, 4, 5, 7, 8, and 10, in combination with MTX 0.4 mg/kg/day IV on days 1, 3, 6, and 11 after transplantation. Median survival of the dogs given MTX in combination with denileukin diftitox was 16 days (range, 13-18 days), similar to that of 35 historical controls given MTX alone (median survival, 20 days). Five of the 6 denileukin diftitox–treated dogs had clinical and pathological evidence of 3-system GVHD; 1 dog died of canine herpes virus infection without evidence of GVHD. In conclusion, denileukin diftitox did not prevent, mitigate, or delay acute GVHD in this stringent and predictive (with respect to outcomes in human patients) hematopoietic cell transplantation model

History of hematopoietic cell transplantation: challenges and progress

After more than 60 years of research in allogeneic hematopoietic cell transplantation (HCT), this therapy has advanced from one that was declared dead in the 1960s to a standard treatment of otherwise fatal malignant and non-malignant blood diseases. To date, close to 1.5 million hematopoietic cell transplants have been performed in more than 1,500 transplantation centers worldwide. This review will highlight the enormous efforts by numerous investigators throughout the world who have brought the experimental field of HCT to clinical reality, examine ongoing challenges, and provide insights for the future

G-CSF-mobilized peripheral blood mononuclear cells added to marrow facilitates engraftment in nonmyeloablated canine recipients: CD3 cells are required

AbstractStable mixed donor/host hematopoietic chimerism can be uniformly established in dogs conditioned with 200 cGy TBI before dog leukocyte antigen (DLA)-identical marrow transplantation and immunosuppressed with a short course of mycophenolate mofetil (MMF) and cyclosporine (CSP) after the transplantation. A further decrease in the TBI dose to 100 cGy or the elimination of MMF in this model results in graft rejection. Here we asked whetherthe addition of G-CSF-mobilized peripheral blood mononuclear cells (G-PBMC) to marrow grafts would enhance donor engraftment in dogs conditioned with 100 cGy TBI and given postgrafting immunosuppression with CSP alone. Using this model, 7 of 9 dogs given only marrow cells rejected their grafts within 8 to 17 weeks after transplantation. In contrast, the addition of unmodified G-PBMC to marrow grafts resulted in stable mixed donor/host chimerism in 5 of 8 dogs studied (P = .06). However, addition of the CD3-depleted fraction of G-PBMC, which contained both CD34 cells and CD14 cells, resulted in engraftment in only 1 of 7 recipients. We conclude that adding G-PBMC to marrow grafts replaced the requirement of MMF and 100 cGy of TBI, and that CD3 cells were required to facilitate engraftment of marrow cells in DLA-identical recipients, whereas the additional CD34 cells present in G-PBMC were not sufficient for this effect.Biol Blood Marrow Transplant 2001;7(11):613-9

Hematopoietic cell transplantation provides an immune-tolerant platform for myoblast transplantation in dystrophic dogs.

Duchenne Muscular Dystrophy (DMD) is the most common and severe form of muscular dystrophy in humans. The goal of myogenic stem cell transplant therapy for DMD is to increase dystrophin expression in existing muscle fibers and to provide a source of stem cells for future muscle generation. Although syngeneic myogenic stem cell transplants have been successful in mice, allogeneic transplants of myogenic stem cells were ineffective in several human trials. To determine whether allogeneic muscle progenitor cells can be successfully transplanted in an immune-tolerant recipient, we induced immune tolerance in two DMD-affected (cxmd) dogs through hematopoietic cell transplantation (HCT). Injection of freshly isolated muscle-derived cells from the HCT donor into either fully or partially chimeric xmd recipients restored dystrophin expression up to 6.48% of wild-type levels, reduced the number of centrally located nuclei, and improved muscle structure. Dystrophin expression was maintained for at least 24 weeks. Taken together, these data indicate that immune tolerance to donor myoblasts provides an important platform from which to further improve myoblast transplantation, with the goal of restoring dystrophin expression to patients with DMD

Mesenchymal Stromal Cells Fail to Prevent Acute Graft-versus-Host Disease and Graft Rejection after Dog Leukocyte Antigen-Haploidentical Bone Marrow Transplantation

Mesenchymal stromal cells (MSCs) have been shown to have immunosuppressive effects in vitro. To test the hypothesis that these effects can be harnessed to prevent graft-versus-host disease (GVHD) and graft rejection after hematopoietic cell transplantation (HCT), we administered a combination of 3 different immortalized marrow-derived MSC lines (15-30 × 106 MSCs/kg/day, 2-5 times/week) or third-party primary MSC (1.0 × 106 MSCs/kg/day, 3 times/week) to canine recipients (n = 15) of dog leukocyte antigen–haploidentical marrow grafts prepared with 9.2 Gy of total body irradiation. Additional pharmacological immunosuppression was not given after HCT. Before their in vivo use, the MSC products were shown to suppress alloantigen-induced T cell proliferation in a dose-dependent, major histocompatibility complex–unrestricted, and cell contact–independent fashion in vitro. Among 14 evaluable dogs, 7 (50%) rejected their grafts and 7 engrafted, with ensuing rapidly fatal acute GVHD (50%). These observations were not statistically different from outcomes obtained with historical controls (n = 11) not given MSC infusions (P = .69). Thus, survival curves for MSC-treated dogs and controls were virtually superimposable (median survival, 18 vs 15 days, respectively). Finally, outcomes of dogs given primary MSCs (n = 3) did not appear to be different from those given clonal MSCs (n = 12). In conclusion, our data fail to demonstrate MSC-mediated protection against GVHD and allograft rejection in this model

Inhibition of CD26/DPP-IV enhances donor muscle cell engraftment and stimulates sustained donor cell proliferation

<p>Abstract</p> <p>Background</p> <p>Transplantation of myogenic stem cells possesses great potential for long-term repair of dystrophic muscle. In murine-to-murine transplantation experiments, CXCR4 expression marks a population of adult murine satellite cells with robust engraftment potential in <it>mdx </it>mice, and CXCR4-positive murine muscle-derived SP cells home more effectively to dystrophic muscle after intra-arterial delivery in <it>mdx^5cv</it>mice. Together, these data suggest that CXCR4 plays an important role in donor cell engraftment. Therefore, we sought to translate these results to a clinically relevant canine-to-canine allogeneic transplant model for Duchenne muscular dystrophy (DMD) and determine if CXCR4 is important for donor cell engraftment.</p> <p>Methods</p> <p>In this study, we used a canine-to-murine xenotransplantation model to quantitatively compare canine muscle cell engraftment, and test the most effective cell population and modulating factor in a canine model of DMD using allogeneic transplantation experiments.</p> <p>Results</p> <p>We show that CXCR4 expressing cells are important for donor muscle cell engraftment, yet FACS sorted CXCR4-positive cells display decreased engraftment efficiency. However, diprotin A, a positive modulator of CXCR4-SDF-1 binding, significantly enhanced engraftment and stimulated sustained proliferation of donor cells <it>in vivo</it>. Furthermore, the canine-to-murine xenotransplantation model accurately predicted results in canine-to-canine muscle cell transplantation.</p> <p>Conclusions</p> <p>Therefore, these results establish the efficacy of diprotin A in stimulating muscle cell engraftment, and highlight the pre-clinical utility of a xenotransplantation model in assessing the relative efficacy of muscle stem cell populations.</p