Porcine Islet-Specific Tolerance Induced by the Combination of Anti-LFA-1 and Anti-CD154 mAbs Is Dependent on PD-1.

We previously demonstrated that short-term administration of a combination of anti-LFA-1 and anti-CD154 monoclonal antibodies (mAbs) induces tolerance to neonatal porcine islet (NPI) xenografts that is mediated by regulatory T cells (Tregs) in B6 mice. In this study, we examined whether the coinhibitory molecule PD-1 is required for the induction and maintenance of tolerance to NPI xenografts. We also determined whether tolerance to NPI xenografts could be extended to allogeneic mouse or xenogeneic rat islet grafts since we previously demonstrated that tolerance to NPI xenografts could be extended to second-party NPI xenografts. Finally, we determined whether tolerance to NPI xenografts could be extended to allogeneic mouse or second-party porcine skin grafts. Diabetic B6 mice were transplanted with 2,000 NPIs under the kidney capsule and treated with short-term administration of a combination of anti-LFA-1 and anti-CD154 mAbs. Some of these mice were also treated simultaneously with anti-PD-1 mAb at >150 days posttransplantation. Spleen cells from some of the tolerant B6 mice were used for proliferation assays or were injected into B6 rag(-/-) mice with established islet grafts from allogeneic or xenogeneic donors. All B6 mice treated with anti-LFA-1 and anti-CD154 mAbs achieved and maintained normoglycemia until the end of the study; however, some mice that were treated with anti-PD-1 mAb became diabetic. All B6 rag(-/-) mouse recipients of first- and second-party NPIs maintained normoglycemia after reconstitution with spleen cells from tolerant B6 mice, while all B6 rag(-/-) mouse recipients of allogeneic mouse or xenogeneic rat islets rejected their grafts after cell reconstitution. Tolerant B6 mice rejected their allogeneic mouse or xenogeneic second-party porcine skin grafts while remaining normoglycemic until the end of the study. These results show that porcine islet-specific tolerance is dependent on PD-1, which could not be extended to skin grafts.

Cell-based gene therapy modifies matrix remodeling after a myocardial infarction in tissue inhibitor of matrix metalloproteinase-3-deficient mice.

OBJECTIVE: Cell-based gene therapy can enhance the effects of cell transplantation by temporally and spatially regulating the release of the gene product. The purpose of this study was to evaluate transient matrix metalloproteinase inhibition by implanting cells genetically modified to overexpress a natural tissue inhibitor of matrix metalloproteinases (tissue inhibitor of matrix metalloproteinase-3) into the hearts of mutant (tissue inhibitor of matrix metalloproteinase-3-deficient) mice that exhibit an exaggerated response to myocardial infarction. Following a myocardial infarction, tissue inhibitor of matrix metalloproteinase-3-deficient mice undergo accelerated cardiac dilatation and matrix disruption due to uninhibited matrix metalloproteinase activity. This preliminary proof of concept study assessed the potential for cell-based gene therapy to reduce matrix remodeling in the remote myocardium and facilitate functional recovery. METHODS: Anesthetized tissue inhibitor of matrix metalloproteinase-3-deficient mice were subjected to coronary ligation followed by intramyocardial injection of vector-transfected bone marrow stromal cells, bone marrow stromal cells overexpressing tissue inhibitor of matrix metalloproteinase-3, or medium. Functional, morphologic, histologic, and biochemical studies were performed 0, 3, 7, and 28 days later. RESULTS: Bone marrow stromal cells and bone marrow stromal cells overexpressing tissue inhibitor of matrix metalloproteinase-3 significantly decreased scar expansion and ventricular dilatation 28 days after coronary ligation and increased regional capillary density to day 7. Only bone marrow stromal cells overexpressing tissue inhibitor of matrix metalloproteinase-3 reduced early matrix metalloproteinase activities and tumor necrosis factor alpha levels relative to medium injection. Bone marrow stromal cells overexpressing tissue inhibitor of matrix metalloproteinase-3 were also more effective than bone marrow stromal cells in preventing progressive cardiac dysfunction, preserving remote myocardial collagen content and structure, and reducing border zone apoptosis for at least 28 days after implantation. CONCLUSIONS: Tissue inhibitor of matrix metalloproteinase-3 overexpression enhanced the effects of bone marrow stromal cells transplanted early after a myocardial infarction in tissue inhibitor of matrix metalloproteinase-3-deficient mice by contributing regulated matrix metalloproteinase inhibition to preserve matrix collagen and improve functional recovery.