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Biomedical subjects

F J M F Dor

Publications and source records attributed to F J M F Dor.

13 recordsLinked to original sources
PubMed2005

Troponin T levels in baboons with pig heterotopic heart transplants.

Troponin T levels have been monitored in baboons (n = 8) undergoing pig heterotopic heart transplantation, and correlated with a decrease in graft contractions and graft survival. Pig heart graft survival was from 12 to 139 days (mean 45, median 33), and graft failure was associated with predominant thrombotic microangiopathy and ischemia, with focal hemorrhage, and edema. An increase in troponin T levels 5 to 6 days before graft failure correlated closely with diminished graft contractions. An increase in troponin T was a reliable indicator that graft dysfunction was occurring.

Animals↗
PubMed2005

Lack of cardiac differentiation in c-kit-enriched porcine bone marrow and spleen hematopoietic cell cultures using 5-azacytidine.

The adult spleen is a source of early hematopoietic stem cells (HSC). We therefore studied whether culturing spleen or bone marrow (BM) HSC in medium containing 5-azacytidine could induce a cardiac phenotype. c-kit enrichment and depletion of adult pig spleen and BM mononuclear cells were obtained by magnetic bead separation using biotinylated pig stem cell factor (c-kit ligand). Cells were incubated with 5-azacytidine for 24 h and refreshed with 5-azacytidine-free medium every 48 h. Western blot was used to detect cardiac troponin and myosin heavy chains. Although 5-azacytidine treatment led to the formation of ball-like cell clusters in both c-kit-enriched populations, these clusters showed no rhythmic contractions (beating), as observed by others. Furthermore, neither cardiac troponin nor myosin was detected in cells derived from either source. Our methodology and treatment with 5-azacytidine did not induce cardiac gene expression in porcine HSC derived from either pig spleen or BM.

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PubMed2004

Absence of humoral and cellular alloreactivity in baboons sensitized to pig antigens.

AIM: to study whether sensitization to pig antigens results in humoral and/or cellular sensitization to alloantigens in baboons, and thus increases the risks of organ allotransplantation after xenotransplantation. Serum from baboons that were naive (n = 4), sensitized to Gal alpha 1,3Gal (Gal) antigens (n = 2), or sensitized to Gal + non-Gal pig antigens (n = 2) were tested by flow cytometry for the presence of immunoglobulin G (IgG) and IgM antibodies that bind to pig or baboon peripheral blood mononuclear cells (PBMC). Two allosensitized baboons were used as positive controls. The same 10 sera were tested in a complement-mediated cytotoxicity assay to detect cytotoxic antibodies against pig, allo and self-PBMC. The T-cell responses of the same baboons to allogeneic and pig PBMC stimulators in mixed lymphocyte reaction (MLR) were studied. All baboon sera contained cytotoxic antibodies that bound to pig PBMC. Binding and cytotoxicity were higher in xenosensitized baboons, particularly in those sensitized to Gal + non-Gal antigens (P < 0.001). None of the naive or xenosensitized baboon sera bound to baboon PBMC. Serum from allosensitized baboons showed anti-baboon IgG and IgM binding, but there was no increase in binding to pig PBMC or in cytotoxicity to pig cells. The MLR response to pig stimulators in baboons sensitized to non-Gal pig antigens was greater than that of naive or Gal-sensitized baboons (P < 0.001), but there was no increase in the response to baboon cells. In baboons, no in vitro evidence that a previous pig xenograft might endanger the outcome of a subsequent allograft was documented.

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PubMed2004

Gal alpha 1,3Gal expression on porcine pancreatic islets, testis, spleen, and thymus.

Gal alpha 1,3Gal (Gal) is the first target in antibody-mediated rejection of pig-to-non-human primate xenograft. Its expression may vary between organs and constituents of organs. Gal expression was studied in pancreas, testis, spleen and thymus of 22 pigs, with ages ranging from 1 to 22 months. The immunoperoxidase technique using the biotinylated lectin, Griffonia simplicifolia (IB4), was used. In the pancreas, neither endocrine (islet cells) nor exocrine cells expressed Gal. The Sertoli cells in the testis were negative. The spleen capsule and trabeculae did not stain for Gal, although both splenic T and B lymphocytes expressed Gal (B > T). Thymocytes were weakly positive, whereas thymic epithelial cells were negative for Gal. No age-related differences were seen in any tissues. Porcine islets of Langerhans, Sertoli cells, and the splenic and thymic structural frameworks did not express Gal, and therefore, should be relatively resistant to anti-Gal antibody-mediated rejection. The availability of pigs deficient in Gal as a source of islets may therefore not be beneficial in extending islet graft survival in non-human primate models.

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PubMed2004

Bone marrow transplantation from alpha1,3-galactosyltransferase gene-knockout pigs in baboons.

BACKGROUND: Successful hematopoietic cell allotransplantation results in donor-specific tolerance, but this approach has been unsuccessful in the wild-type pig-to-baboon xenotransplantation model, as pig cells were lost from the circulation within 5 days. However, after cessation of immunosuppressive therapy on day 28, all baboons demonstrated non-specific unresponsiveness on mixed leukocyte reaction (MLR) for at least 30 days. We have now investigated the transplantation of bone marrow (BM) cells from miniature swine homozygous for alpha1,3-galactosyltransferase gene-knockout (GalT-KO). METHODS: Baboons (n = 3) were pre-treated with whole body and thymic irradiation, anti-thymocyte globulin, and splenectomy, and received immunosuppressive and supportive therapy for 28 days. BM was harvested from GalT-KO swine (n = 3). The baboons were monitored for the presence of pig cells by flow cytometry and colony-forming units (CFUs), and for cellular reactivity by MLR. RESULTS: A mean of 11 x 10(8) BM cells/kg was infused into each baboon. The mean absolute numbers and percentages of pig cells detected in the blood at 2 h and on days 1, 2 and 4, respectively, were 641/microl (9.5%), 132/microl (3.4%), 242/microl (3.9%), and 156/microl (2.9%). One baboon died (from accidental hemorrhage) on day 6, at which time chimerism was present in the blood (2.0%) and BM (6.4%); pig cell engraftment in the BM was confirmed by polymerase chain reaction (PCR) of CFUs. In the two other baboons, blood chimerism was lost after day 5 but returned at low levels (<1%) between days 9 to 16 and 7 to 17, respectively, indicating transient BM engraftment. Both surviving baboons showed non-specific unresponsiveness on MLR until they were euthanized on days 85 and 110, respectively. CONCLUSIONS: By using BM cells from GalT-KO pigs, chimerism was detected at levels comparable with previous studies when 30-fold more growth factor-mobilized peripheral blood progenitor cells had been transplanted. In addition, cellular hyporesponsiveness was prolonged. However, long-term engraftment and chimerism were not achieved.

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PubMed2003

Spleen transplantation in miniature swine: surgical technique and results in major histocompatibility complex-matched donor and recipient pairs.

BACKGROUND: Spleen transplantation (Tx) between some strains of rodents can lead to donor-specific tolerance either spontaneously or after a short course of immunosuppression. This study developed a surgical technique for spleen Tx in miniature swine to investigate its immunologic impact in a large animal model. METHODS: The preferred surgical technique of spleen Tx (n=8) involved excision of the donor spleen with its vascular pedicle to the aorta and portal vein. Carrel patches of donor aorta and portal vein were anastomosed to the abdominal aorta and inferior vena cava, respectively, of the (splenectomized) recipient. The results in four major histocompatibility complex-matched pairs that were mismatched for the porcine allelic antigen are reported. Two recipients were untreated, one received a 12-day course of cyclosporine A (CsA) alone, and one received thymic irradiation (700 cGy) and CsA. Hematopoietic cell chimerism was followed by fluorescence-activated cell sorter, and graft survival was assessed by histology. RESULTS: Spleen Tx was technically successful. In two untreated pigs, chimerism was detected in the blood (maximum 5% for 17 and 25 days) and lymph nodes (maximum 6% for 28 and 56 days), but both grafts showed histologic rejection by day 28. In two treated pigs, chimerism was present in the blood for 47 and 57 days, and rejection was prevented, with follow-up for 57 and 217 days, respectively. CONCLUSION: Spleen Tx in major histocompatibility complex-matched pairs treated with CsA+/-thymic irradiation results in prolonged chimerism and is associated with the development of in vivo unresponsiveness to the transplanted spleen.

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PubMed2002

Therapeutic interventions in xenotransplantation.

Xenotransplantation, involving the transplantation of pig organs into humans, would resolve the current shortage of organs. It involves, however, a new therapeutic approach to organ transplantation. The presence of natural antibody in primates directed against Galalpha1,3Gal epitopes on pig vascular endothelium leads to early antibody-mediated rejection. An elicited antibody response against the same target epitopes as well as against nonGal antigens intensifies the immune destruction of the organ. Even the minimal deposition of antibody appears to lead to the development of a consumptive coagulopathy that can be fatal. Approaches being investigated to overcome these barriers include depletion and inhibition of natural antibody and complement, and suppression of the elicited T cell-dependent antibody and cellular responses. In addition, however, physiologic incompatibilities between human and pig, particularly those relating to coagulation, may enhance or complicate the immune process, and may require additional therapeutic measures. Current approaches aimed at achieving successful xenotransplantation also include investigation of agents that prevent potential xenozoonotic infection of the recipient. At present, therefore, the therapeutic interventions required to attempt to overcome the barriers to xenotransplantation are multiple. Work indicating progress in the breeding of pigs that do not express the critical Galalpha1,3Gal epitopes, however, is encouraging. The introduction of these pigs may greatly reduce the therapy required, and may ultimately allow the development of methods to induce tolerance to the transplanted pig organ.

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PubMedDate not supplied

Potential of aspirin to inhibit thrombotic microangiopathy in alpha1,3-galactosyltransferase gene-knockout pig hearts after transplantation in baboons.

Hearts from alpha1,3-Galactosyltransferase gene-knockout (GaIT-KO) pigs were transplanted heterotopically into 8 baboons that received an anti-CD154 monoclonal antibody (mAb)-based immunosuppressive regimen and heparin. Three baboons died or were euthanized with beating grafts on 16, 23, and 56 days, respectively, and the remaining 5 grafts functioned for 59-179 days. Hyperacute rejection did not occur, and classical features of acute humoral xenograft or acute cellular rejection were rare. However, thrombotic microangiopathy (TM) developed in all cases; its onset was delayed in 2 baboons that received aspirin. Function of a pig organ in a baboon for a period approaching 6 months has not been reported previously and lends encouragement that the barriers to xenotransplantation will be overcome, but TM requires investigation.

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