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Biomedical subjects

L Bühler

Publications and source records attributed to L Bühler.

At least 19 recordsLinked to original sources
PubMed2006

Sequential kidney/islet transplantation: efficacy and safety assessment of a steroid-free immunosuppression protocol.

The aim of this study was to assess the efficiency and safety of the Edmonton immunosuppression protocol in recipients of islet-after-kidney (IAK) grafts. Fifteen islet infusions were administered to 8 patients with type 1 diabetes and a functioning kidney graft. Immunosuppression was switched on the day of transplantation to a regimen associating sirolimus-tacrolimus-daclizumab. Insulin-independence was achieved in all patients for at least 3 months, with an actual rate of 71% at 1 year after transplantation (5 of 7 patients). After 24-month mean follow-up, five have ongoing insulin independence, 11-34 months after transplantation, with normal HbA1c, fructosamine and mean amplitude of glycemic excursions (MAGE) values. Results of arginine-stimulation tests improved over time, mostly after the second islet infusion. Severe adverse events included bleeding after percutaneous portal access (n=2), severe pneumonia attributed to sirolimus toxicity (n=1), kidney graft loss after immunosuppression discontinuation (n=1), reversible humoral kidney rejection (n=1) and fever of unknown origin (n=1). These data indicate that the Edmonton approach can be successfully applied to the IAK setting. This procedure is associated with significant side effects and only patients with stable function of the kidney graft should be considered. The net harm versus benefit has not yet been established and will require further studies with larger numbers of enrolled subjects.

Adrenal Cortex Hormones↗
PubMed2005

[Nephrology].

Alternative to nephrotoxic calcineurin inhibitors regimens are feasible in renal transplantation. Sirolimus is an effective immunosuppressive drug with less drug-induced nephrotoxicity. Enteric-coated mycophenolate sodium provides a safety and efficacy alternative to mycophenolate mofetil. In peritoneal effluent, cancer antigen 125 (Ca 125) is a mesothelial cell marker and of in vivo biocompatibility of the new dialysis solutions. Longterm PD and peritoneal sclerosis are associated with a low number of mesothelial cells and a low concentration of dialysate Ca 125. Exposure to glucose and degradation products (GDPs) is important in the genesis of mesothelial damage. Short results of the more biocompatible solutions are promising (increasing of Ca 125). In the future, exposure to glucose can be reduced by using combinations of various osmotic agents, each in a low concentration (glycerol and amino acid solution).

Humans↗
PubMed2004

Short-term immunosuppression reduces fibrotic cellular infiltration around barium-M-alginate microbeads injected intraportally.

INTRODUCTION: One of the major barriers affecting the viability of encapsulated islets is pericapsular fibrotic infiltration (PFI). This study aimed to design strategies to reduce PFI around intraportally injected alginate microbeads. METHODS: Empty, highly purified, barium-M-alginate microbeads (400 microm) were injected intraportally into Lewis rats (3000 beads/rat). Rats (n = 9/group) were treated daily with either rapamycine (RAPA; 1 mg/kg/d p.o.), tacrolimus (TAC; 2 mg/kg/d p.o.), a combination of both, or gadolinium-chloride (GdC13, 20 mg/kg/d i.v., at day -1 and day +4). Treatment was discontinued at 10 days. Three rats/group were sacrificed at 3, 7, and 42 days after transplantation. Cellular composition of PFI was evaluated by immunohistochemistry. Severity of the reaction to the beads was determined by measuring the thickness of PFI on histology. RESULTS: The main cellular components of PFI in the liver were macrophages and myofibroblasts. There was a significant (P <.05) reduction in the thickness of PFI in all treated groups, even 6 weeks after transplantation. Encapsulated rat islets showed excellent insulin response to glucose in vitro, with a stimulation index of 3.6 +/- 2.0. CONCLUSION: Combination of highly purified alginate with short-term immunosuppression reduces fibrotic overgrowth around microbeads injected intraportally.

Alginates↗
PubMed2004

Optimization of neutral protease to collagenase activity ratio for islet of Langerhans isolation.

AIM: The optimal neutral protease to collagenase activity ratio has not been determined for islet isolation. We evaluated a new highly purified collagenase that can be blended with predetermined amounts of neutral protease (NP). METHODS: Islets were isolated from 7 groups of Sprague-Dawley rats. In group I, collagenase type XI (Sigma) at 2 mg/mL, and, in group II, Liberase at 0.6 mg/mL (2.4 PZ- U/mL; Roche) were used as controls. In groups III to VII, collagenase NB1 0.6 mg/mL (2.4 PZ-U/mL; Serva Electrophoresis) was used with increasing amounts of added NP. The NP to collagenase activity ratio (DMC-U/PZ-U) increased from 0.5% in group III to 2.0% in group VII. RESULTS: Mean islet equivalent (IE) yields per rat were 1367, 1755, 597, 895, 1712, 1043, and 905 in groups I to VII. IE yields were maximal at DMC-U/PZ-U = 1.2%. Islet morphology was influenced by NP concentration with decreasing numbers of trapped islets and increasing numbers of fragmented islets as NP contents increased. Cytokine release, islet cell apoptosis, and in vitro function were significantly better in groups III to VII as compared with groups I and II. CONCLUSION: NP is a crucial additive to collagenase for islet isolation. Optimization of the NP to collagenase activity ratio (1.2% in this model) improves yields and morphology after islet isolation.

Animals↗
PubMed2004

Islet autotransplantation for the prevention of surgical diabetes after extended pancreatectomy for the resection of benign tumors of the pancreas.

OBJECTIVE: The objective of this article is to report a single-center experience with islet autotransplantation after extensive pancreatic resection for benign tumors of the pancreas. MATERIALS AND METHODS: Seven patients underwent extensive left pancreatectomy for benign lesions located at the neck of the pancreas. Once an unequivocal diagnosis of a benign nature was ascertained, the rest of the specimen was processed and the unpurified pancreatic digest was infused into the portal vein. The results were compared with those of 8 autotransplantations performed for chronic pancreatitis over the same period. RESULTS: Tumors were 4 cystadenomas, 2 insulinomas and 1 neuroendocrine tumor. Mean islet yields were 275,000 islet equivalents (IEQ) versus 129,000 in chronic pancreatitis (P =.04) or 6700 IEQ/g of tissue versus 1900 (P =.002), resulting in transplantation of 4200 IEQ/kg body weight vs 2150 in chronic pancreatitis (P =.03), respectively at 4-month to 7.5-year follow-up, all patients are alive and 6 of 7 are off insulin. All patients off insulin after at least 1 year currently have a normal IVGTT, with K values ranging between -1.19 and -2.36 (normal < -1.00). All patients, including 1 on insulin, display positive basal and glucagon-stimulated C-peptide levels. CONCLUSIONS: Compared with chronic pancreatitis tissue resected for benign tumors is more likely to achieve good islet yields, and thus insulin independence after autotransplantation. Islet autotransplantation should be considered when extensive pancreatectomy is required for resection of a benign tumor, and only if the benign nature of the lesion is demonstrated unequivocally.

Aged↗
PubMed2004

Islet of Langerhans allogeneic transplantation at the University of Geneva in the steroid free era in islet after kidney and simultaneous islet-kidney transplantations.

AIMS: We report a single-center experience of islet allogeneic transplantation in islet after kidney (IAK) and simultaneous islet-kidney (SIK) type 1 diabetic recipients using a steroid-free immunosuppressive regimen. METHODS: Eight patients received 12 islet infusions in 5 IAK and 3 SIK procedures. Median age was 51 years (range, 30-58 years) with a male:female ratio of 2:6. IAK was considered only for patients with a stable kidney function and a creatinine clearance level >60 mL/min. SIK was considered for patients with a counterindication for simultaneous kidney-pancreas transplantation. Immunosuppression was based on sirolimus/tacrolimus combined with daclizumab induction. Two consecutive infusions of >5000 islet equivalents (IEQ)/kg were planned. RESULTS: Five patients completed the transplantation course, whereas 3 patients received only 1 islet infusion. All patients have functional grafts (C-peptide >166 pmol/L) at 6-month median follow-up. Of 5 patients who completed their transplantation course 4 became insulin independent. HbA1c and fructosamine decreased over time, showing improved metabolic control. Severe adverse events were observed in 4 patients. One SIK patient died after OKT-3 treatment of severe kidney rejection. CONCLUSIONS: The Edmonton immunosuppressive protocol can be applied for patients undergoing either IAK or SIK procedures, with a high rate of graft function and insulin independence. Morbidity is higher than among patients undergoing solitary islet transplantation for type 1 brittle diabetes.

Adult↗
PubMed2004

Paraganglioma of the ampulla of Vater: a potentially malignant neoplasm.

Paragangliomas are rare tumours originating from neuroectodermic remnants and are usually considered as benign. We present two cases of paraganglioma of the ampulla of Vater that were treated surgically by pancreaticoduodenectomy. In one case, histopathology revealed malignant characteristics of the tumour with invasion of the pancreas and simultaneous duodenal lymph-node metastases. Both patients had a favourable outcome without disease recurrence at 40 and 44 months postoperatively. Only 21 cases of ampullary paraganglioma have been reported in the literature, 7 of them with malignant characteristics. In conclusion, paragangliomas of the ampulla of Vater have malignant potential. Surgical therapy of these tumours should not be limited to local resection, as disease recurrence and lymph node involvement have been reported. We propose that paragangliomas of the ampulla of Vater should be operated by cephalic pancreaticoduodenectomy, which allows long-term and disease-free survival.

Adult↗
PubMed2003

Statistics in medicine.

Explore the source record for details and available documents.

Data Interpretation, Statistical↗
PubMed2003

A tale of two colons and two cancers. Distinct carcinogenesis and clinical outcome according to location proximal or distal to the splenic flexure.

The central hypothesis explored in this paper is that colorectal cancer (CRC) is a heterogeneous disease. The initial clue to this heterogeneity was provided by genetic findings; however, embryological and physiological data had previously been gathered, showing that proximal (in relation to the splenic flexure) and distal parts of the colon represent distinct entities. Molecular biologists have identified two distinct pathways, microsatellite instability (MSI) and chromosomal instability (CIN), which are involved in CRC progression. In summary, there may be not one, but two colons and two types of colorectal carcinogenesis, with distinct clinical outcome. The implications for the clinicians are two-folds; 1) tumors originating from the proximal colon have a better prognosis due to a high percentage of MSI-positive lesions; and 2) location of the neoplasm in reference to the splenic flexure should be documented before group stratification in future trials of adjuvant chemotherapy in patients with stage II and III colon cancer.

Cell Transformation, Neoplastic↗
PubMed2002

Pig hematopoietic cell chimerism in baboons conditioned with a nonmyeloablative regimen and CD154 blockade.

BACKGROUND: In an attempt to induce mixed hematopoietic chimerism and transplantation tolerance in the pig-to-primate model, we have infused high-dose porcine peripheral blood progenitor cells (PBPC) into baboons pretreated with a nonmyeloablative regimen and anti-CD154 monoclonal antibody (mAb). METHODS: Group 1 baboons (n=2) received a nonmyeloablative regimen including whole body irradiation, pharmacological immunosuppression, porcine hematopoietic growth factors, and immunoadsorption of anti-Galalpha1,3Gal (Gal) antibody before infusion of high doses of PBPC (2.7-4.6x10(10) cells/kg). In group 2 (n=5), cyclosporine was replaced by anti-CD154 mAb. Group 3 (n=3) received the group 1 regimen plus anti-CD154 mAb. RESULTS: In group 1, pig chimerism was detected in the blood by flow cytometry (FACS) for 5 days (with a maximum of 14%), and continuously up to 13 days by polymerase chain reaction (PCR). In group 2, pig chimerism was detectable for 5 days by FACS (maximum 33%) and continuously up to 28 days by PCR. In group 3, initial pig chimerism was detectable for 5 days by FACS (maximum 73%). Two of three baboons showed reappearance of pig cells on days 11 and 16, respectively. In one, in which no anti-Gal IgG could be detected for 30 days, pig cells were documented in the blood by FACS on days 16-22 (maximum 6% on day 19) and pig colony-forming cells were present in the blood on days 19-33, which we interpreted as evidence of engraftment. Microchimerism was continuous by PCR up to 33 days. CONCLUSIONS: These results suggest that there is no absolute barrier to pig hematopoietic cell engraftment in primates, and that this may be facilitated if the return of anti-Gal IgG can be prevented.

Animals↗
PubMed2002

Depletion of anti-gal antibodies in baboons by intravenous therapy with bovine serum albumin conjugated to gal oligosaccharides.

BACKGROUND: Anti-Galalpha 1-3Gal (Gal) antibodies (Ab) play a key role in the rejection of pig cells or organs transplanted into primates. A course of extracorporeal immunoadsorption (EIA) of anti-Gal Ab using an immunoaffinity column of a Gal type 6 oligosaccharide depletes Ab successfully, but Ab returns during the next few days. Although therapy with an anti-CD154 monoclonal antibody (mAb) prevents an induced Ab response to Gal or non-Gal epitopes, T cell-independent natural anti-Gal IgM and IgG return to baseline (pretransplant) levels. We have investigated the capacity of continuous i.v. infusion of bovine serum albumin conjugated to Gal type 6 oligosaccharide (BSA-Gal) to deplete or maintain depletion of circulating anti-Gal Ab. METHODS: Porcine peripheral blood mobilized progenitor cells (PBPC) obtained by leukapheresis from MHC-inbred miniature swine (n=6) were transplanted into baboons. Group 1 baboons (n=4) underwent whole body (300 cGy) and thymic (700 cGy) irradiation, T cell depletion with antithymocyte globulin, complement depletion with cobra venom factor, short courses of anti-CD154 mAb therapy (20 mg/kg i.v. on alternate days), cyclosporine (CyA) (in two baboons only), mycophenolate mofetil, and porcine hematopoietic growth factors. Anti-Gal Ab depletion by EIA was carried out before transplantation of high doses (2-4x 1010 cells/kg) of PBPC. Group 2 baboons (n=3) received the group 1 regimen (including CyA) plus a continuous i.v. infusion of BSA-Gal. To prevent sensitization to BSA, anti-CD154 mAb therapy was continued until BSA-Gal administration was discontinued. RESULTS: In group 1, Gal-reactive Ab returned to pre-PBPC transplant levels within 15-21 days, but no induced Ab to Gal or non-Gal determinants developed while anti-CD154 mAb therapy was being administered. In group 2, anti-Gal Ab was either not measurable or minimally measurable while BSA-Gal was being administered. After discontinuation of BSA-Gal, Ab did not return to pre-PBPC transplant level for more than 40-60 days, and no sensitization developed even when all therapy was discontinued. In one baboon, however, Ab to Gal type 2, but not type 6, returned during BSA-Gal therapy. CONCLUSIONS: Prevention of the induced humoral response to Gal and non-Gal epitopes by anti-CD154 mAb therapy has been reported previously by our group, but our studies are the first to demonstrate a therapy that resulted in an absence of natural anti-Gal Ab for a prolonged period. The combination of BSA-Gal and T cell costimulatory blockade may facilitate survival of pig cells and organs transplanted into primates. The return in one baboon of Ab reactive with the Gal type 2 oligosaccharide, but not type 6, indicates some polymorphism of anti-Gal Ab and suggests that, to be effective in all cases, the infusion of a combination of type 6 and type 2 BSA-Gal may be required.

Animals↗
PubMed2002

Adult porcine islet transplantation in baboons treated with conventional immunosuppression or a non-myeloablative regimen and CD154 blockade.

The aim of the present study was to assess the survival of adult porcine islets transplanted into baboons receiving either (I) conventional triple drug immunosuppressive therapy or (2) a non-myeloablative regimen and an anti-CD154 monoclonal antibody (mAb) aimed at tolerance-induction. Group 1 baboons (n = 3) were pancreatectomized prior to intraportal injection of 10,000 porcine islet equivalents (IE)/kg and immunosuppressed with anti-thymocyte globulin (ATG), cyclosporine and azathioprine. In Group 2 (n = 2), non-pancreatectomized baboons underwent induction therapy with whole body and thymic irradiation, and ATG. Extracorporeal immunoadsorption (EIA) of anti-Galalpha1,3Gal (Gal) antibody was carried out. Maintenance therapy was with cobra venom factor, cyclosporine. mycophenolate mofetil, methylprednisolone and anti-CD154 mAb. Porcine islets were injected intraportally (14,000 and 32,000 IE/kg, respectively) and high-dose pig mobilized peripheral blood progenitor cells (3 x 10(10) cells/kg) were infused into a systemic vein. Porcine islets were also implanted in the sternomastoid muscle to facilitate subsequent biopsies. In both groups. porcine C-peptide was measured, and histological examination of liver or sternomastoid muscle biopsies was performed at regular intervals. In Group 1, total pancreatectomy reduccd human C-peptide to < 0.1 ng/ml and induced insulin-requiring diabetes. The transplantation of porcine islets was followed by normalization of glycemia for 15-24 h. Porcine C-peptide was detected only transiently immediately after porcine islet injection (maximum 0.12 ng/ml). Histological examination of liver biopsies taken between days 2 and 19 did not reveal viable islets, but necrotic cell structures with mononuclear cell infiltrates were identified in portal venules. In Group 2, injection of porcine islets into non-pancreatectomized recipients induced a transient hypoglycemia (2-4 h) requiring concentrated intravenous dextrose administration. Porcine C-peptide was detectable for 5 and 3 days (maximum 2.8 and 1.0 ng/ml), respectively. Baboon #4 died on day 12 from small bowel intussusception. Liver and sternomastoid muscle biopsies showed well-preserved porcine islets, staining positive for insulin and glucacon, without signs of rejection. In baboon #5, viable islets were detected in the sternomastoid muscle biopsy on day 14, but not on day 28 or thereafter. A progressive mononuclear cell and macrophage infiltration was seen in the biopsies. In conclusion, conventional immunosuppression allowed survival of porcine islets in baboons for < 24 h. The non-myeloablative regimen prolonged survival of porcine islets for > 14 days. However, despite depletion of T cells, anti-Gal antibody and complement, and CD154-hlockade, porcine islets were rejected by day 28. These results suggest that powerful innate immune responses are involved in rejection of discordant xenogencic islets.

Animals↗
PubMed2001

Transplantation of islets of Langerhans: new developments.

The clinical results recently reported by the Edmonton group in recipients of allogeneic islet grafts, all of whom achieved at least temporary insulin independence, has rekindled interest in transplantation of islets of Langerhans as a means to cure diabetes. Long-term islet graft survival has been achieved in a non-human primate pre-clinical model with a protocol of T-cell signaling blockade using a new monoclonal antibody. Islet xenotransplantation (namely the use of animal islets, with the aim of transplanting them into humans), or stem cell technology (the controlled differentiation of stem cells to obtain specialised cells for the treatment of diabetes) are other procedures currently being evaluated in animal models. The recent clinical success suggests that, in the near future, diabetes might be treated by islet transplantation early in the clinical course of the disease before the development of complications, and without the risks associated with conventional immunosuppression.

Animals↗
PubMed2001

Pig kidney transplantation in baboons: anti-Gal(alpha)1-3Gal IgM alone is associated with acute humoral xenograft rejection and disseminated intravascular coagulation.

BACKGROUND: Kidneys harvested from miniature swine or pigs transgenic for human decay-accelerating factor (hDAF) were transplanted into baboons receiving an anti-CD154 monoclonal antibody (mAb) and either a whole body irradiation (WBI)- or cyclophosphamide (CPP)-based immunosuppressive regimen. METHODS: Group 1 baboons (n=3) underwent induction therapy with WBI and thymic irradiation, pretransplantation antithymocyte globulin, and immunoadsorption of anti-Gal(alpha)1-3Gal (Gal) antibody (Ab). After transplantation of a miniature swine kidney, maintenance therapy comprised cobra venom factor, mycophenolate mofetil, and an anti-CD154 mAb (for 14-28 days). In group 2 (n=2), WBI was replaced by CPP in the induction protocol. Group 3 (n=3) animals received the group 2 regimen, but underwent transplantation with hDAF pig kidneys. RESULTS: Group 1 and 2 animals developed features of disseminated intravascular coagulation (DIC), with reductions of fibrinogen and platelets and increases of prothrombin time, partial thromboplastin time, and fibrin split products. Graft survival was for 6-13 days. Histology showed mild acute humoral xenograft rejection (AHXR) of the kidneys, but severe rejection of the ureters. Group 3 animals developed features of DIC in two of three cases during the fourth week, with AHXR in the third case. Graft survival was for 28 (n=1) or 29 (n=2) days. Histology of day 15 biopsy specimens showed minimal focal mononuclear cellular infiltrates, with predominantly CD3+ cells. By days 28 and 29, kidneys showed mild-to-moderate features of AHXR. In all groups, the humoral response was manifest by reappearance of anti-Gal IgM below baseline level, with no or low return of anti-Gal IgG. All excised kidneys showed IgM deposition, but no complement and no or minimal IgG deposition. No baboon showed a rebound of anti-Gal Ab immediately after excision of the graft, and anti-Gal Ab increased over pretransplantation levels only when anti-CD154 mAb was discontinued. CONCLUSIONS: DIC was observed with WBI- or CPP-based therapy, and after miniature swine or hDAF kidney transplantation. AHXR+/-DIC was observed in all recipients even in the absence of complement and no or low levels of anti-Gal IgG, but was significantly delayed in the hDAF recipients. These results confirm our earlier observation that CD154 blockade prevents T cell-dependent sensitization in baboons to pig antigens, but that baseline natural anti-Gal Ab production is not inhibited. We suggest that IgM deposition, even in the absence of IgG and complement, leads to endothelial cell activation with the development of DIC, even when there are only minimal histologic changes of AHXR.

Acute Disease↗
PubMed2001

CD40-CD154 pathway blockade requires host macrophages to induce humoral unresponsiveness to pig hematopoietic cells in baboons.

The effect of CD154 blockade and macrophage depletion or inhibition on baboon humoral and cellular immune responses to pig antigens was studied in a pig-to-baboon peripheral blood mobilized progenitor cell (PBPC) transplantation model aimed at inducing tolerance. We infused pig PBPCs in baboons pretreated with a nonmyeloablative regimen along with murine anti-human CD154 monoclonal antibody (mAb) and macrophage-depleting or -inhibiting agents. Group 1 baboons (n=2) underwent a nonmyeloablative regimen and immunoadsorption of anti-Gal(alpha)1,3Gal (Gal) antibody (Ab) before intravenous infusion of high doses (1.3-4.6 x 10(10)cells/kg) of PBPCs. In group 2 (n=5), cyclosporine was replaced by 8 doses of anti-CD154 mAb over 14 days. Group 3 (n=3) received the group 2 regimen plus medronate liposomes (n=2) or commercially available human intravenous immunoglobulin G depleted of anti-Gal Ab (n=1) to deplete/inhibit recipient macrophages. Group 1 developed sensitization to Gal and also developed new Ab to non-Gal porcine antigens within 10 to 20 days. In group 2, no sensitization to Gal or non-Gal determinants was seen, but Gal-reactive antibodies did return to their preleukocyte transplantation levels. CD154 blockade, therefore, induced humoral unresponsiveness to pig cells. In group 3, sensitization to Gal was seen in all three baboons at 20 days, and Abs against new porcine determinants developed in one baboon. The depletion or inhibition of host macrophages, therefore, prevented the induction of humoral unresponsiveness by CD154 blockade. These results suggest that CD154 blockade induces humoral unresponsiveness by a mechanism that involves the indirect pathway of antigen presentation. In vitro investigation of baboon anti-pig mixed lymphocyte reaction confirmed that only the indirect pathway is efficiently blocked by anti-CD154 mAb. The mechanism in which blockade of the CD40-CD154 pathway induces its effect remains to be determined, but it could involve the generation of regulatory cells capable of suppressing the direct pathway.

Animals↗
PubMed2001

Insulin independence and normalization of oral glucose tolerance test after islet cell allotransplantation.

To achieve permanent normoglycemia in patients with type I diabetes, it is necessary to renew the insulin-producing beta-cells by transplantation of either a vascularized pancreatic graft or isolated islets of Langerhans. Presently, about 10% of patients with type I diabetes undergoing islet allotransplantation achieve insulin independence; however, glucose intolerance remains in the majority of cases. We report a case of long-term insulin independence after islet allotransplantation in a type I diabetic patient. Three years after islet transplantation, the patient remains insulin-independent with a normal oral glucose tolerance test (OGTT). The patient therefore no longer meets the World Health Organization criteria for the diagnosis of diabetes mellitus and demonstrates that islet transplantation can cure diabetes in type I diabetic patients.

Adult↗
PubMed2001

Porcine hematopoietic cell xenotransplantation in nonhuman primates is complicated by thrombotic microangiopathy.

Thrombotic microangiopathy (TM) is a serious complication of bone marrow transplantation (BMT) that resembles thrombotic thrombocytopenic purpura (TTP). In attempting to achieve hematopoietic cell chimerism in the pig-to-baboon model, we have observed TM following infusion of high doses (>10(10) cells/kg) of porcine peripheral blood mobilized progenitor cells (PBPC) into baboons. We performed investigations to analyze the pathobiology of this TM and to test therapeutic interventions to ameliorate it. PBPC were obtained by leukapheresis of cytokine-stimulated swine. The initial observations were made in two baboons that underwent a non-myeloablative regimen (NMR) prior to PBPC transplantation (TX) (group 1). We then studied three experimental groups. Group 2 (n = 2) received NMR without PBPC TX. Group 3 (n = 2) received PBPC TX alone. Group 4 (n = 6) received NMR + PBPC TX combined with prostacyclin, low-dose heparin, methylprednisolone, and cyclosporine was replaced by anti-CD40L mAb in five cases. Baboons in groups 1 and 3 developed severe thrombocytopenia (<10,000/mm3), intravascular hemolysis with schistocytosis (>10/high powered field (hpf)), increase in plasma lactate dehydrogenase (LDH) (2500-9000 U/l), transient neurologic changes, renal insufficiency, and purpura. Autopsy on two baboons confirmed extensive platelet thrombi in the microcirculation, and, similar to clinical BMT-associated TM/TTP, no unusually large vWF multimers or changes in vWF protease activity were observed in the plasma of baboons with TM. In group 2, self-limited thrombocytopenia occurred for 10-15 days following NMR. Group 4 baboons developed thrombocytopenia (<20,000/mm3) rarely requiring platelet transfusion, minimal schistocytosis (<3/hpf), minor increase in LDH (<1000 U/l), with no clinical sequelae. We conclude that high-dose porcine PBPC infusion into baboons induces a microangiopathic state with vWF biochemical parameters resembling clinical BMT-associated TM/TTP and that administration of antithrombotic and anti-inflammatory agents can ameliorate this complication.

Animals↗