Positron Emission Tomography in Clinical Islet Transplantation

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants. A fraction of the islets (23%) were labeled with 18F‐fluorodeoxyglucose ([¹⁸F]FDG) and carefully mixed with unlabeled islets just prior to intraportal transplantation. The peak radioactivity concentration in the liver was found at 19 min after start of islet infusion and corresponded to only 75% of what was expected, indicating that islets are lost during the transplantation procedure. No accumulation of radioactivity was found in the lungs. A nonphysiological peak of C‐peptide was found in plasma during and immediately after transplantation in all subjects. Distribution in the liver was heterogeneous with wide variations in location and concentration. Islets found in areas with concentrations of >400 IEQ/cc liver tissue varied between 1% and 32% of the graft in different subjects. No side effects attributed to the PET/CT procedure were found. Clinical outcome in all patients was comparable to that previously observed indicating that the [¹⁸F]FDG labeling procedure did not harm the islets. The technique has potential to be used to assess approaches to enhance islet survival and engraftment in clinical transplantation.     

Serum Amyloid A and P Protein Levels are Lowered by Dextran Sulfate Cellulose Low-Density Lipoprotein Apheresis

The present study describes the short-term effect of dextran sulfate cellulose (DSC) low-density lipoprotein (LDL) apheresis using a plasma separator equipped with a polysulfone (PS) membrane filter (PS/DSC-LDL apheresis) on the serum amyloid A (SAA) and P (SAP) protein levels during treatment in a patient with familial hypercholesterolemia (type IIa, heterozygote). PS/DSC-LDL apheresis markedly lowered both the SAA (reduction percentage, 84.1 ± 8.2%) and SAP (91.4 ± 5%) levels, which returned to their respective initial levels within 4 days. Experimentally, the levels of both proteins also decreased on passage through the DSC minicolumn without a PS membrane, indicating that the DSC resin had an affinity to both proteins. These results suggest that PS/DSC-LDL apheresis may be advantageous for amyloid protein accumulating disorders, including amyloidosis and atherosclerosis.     

Heparin–Induced Extracorporeal Low–Density Lipoprotein Precipitation and Low–Density Lipoprotein Chemoadsorption onto Dextran Sulfate: A Comparison

Abstract: Both heparin–induced extracorporeal low–density lipoprotein precipitation (HELP) and dextran sulfate (DS) apheresis are potent tools for acute and long–term risk factor reduction in the secondary prevention treatment of coronary patients suffering from recalcitrant hypercholesterolemia. They combine high efficacy and selectivity of risk factor removal. Whereas LDL cholesterol and lipoprotein (a) adsorption onto DS offers the advantage of an unlimited treatable plasma volume and somewhat easier handling, HELP reduces fibrinogen more effectively and does not interfere with angiotension converting enzyme (ACE) inhibitors. Both systems can improve blood rheology and induce regression or stabilize coronary lesions. In an uncontrolled trial, HELP reduced the incidence of myocardial infarction. To date, no controlled prospective trials have been performed comparing the two systems with respect to their long–term risk factor reduction and their effect on coronary lesions, morbidity, and mortality.     

Endothelial Cell Protection by Dextran Sulfate: A Novel Strategy to Prevent Acute Vascular Rejection in Xenotransplantation

We showed recently that low molecular weight dextran sulfate (DXS) acts as an endothelial cell (EC) protectant and prevents human complement- and NK cell-mediated cytotoxicity towards porcine cells in vitro. We therefore hypothesized that DXS, combined with cyclosporine A (CyA), could prevent acute vascular rejection (AVR) in the hamster-to-rat cardiac xenotransplantation model. Untreated, CyA-only, and DXS-only treated rats rejected their grafts within 4-5 days. Of the hearts grafted into rats receiving DXS in combination with CyA, 28% survived more than 30 days. Deposition of anti-hamster antibodies and complement was detected in long-term surviving grafts. Combined with the expression of hemoxygenase 1 (HO-1) on graft EC, these results indicate that accommodation had occurred. Complement activity was normal in rat sera after DXS injection, and while systemic inhibition of the coagulation cascade was observed 1 h after DXS injection, it was absent after 24 h. Moreover, using a fluorescein-labeled DXS (DXS-Fluo) injected 1 day after surgery, we observed a specific binding of DXS-Fluo to the xenograft endothelium. In conclusion, we show here that DXS + CyA induces long-term xenograft survival and we provide evidence that DXS might act as a local EC protectant also in vivo.     

Changes in Renal Function after Clinical Islet Transplantation: Four-Year Observational Study

Tight glycemic control can reduce progression of diabetic nephropathy (DN) while the histological changes may regress after pancreas transplantation. Clinical islet transplantation (CIT) can restore euglycemia but the effects of CIT and concomitant immunosuppression on renal function are not known. Renal function (modification of diet in renal disease estimated glomerular filtration rate [GFR]) is reported in 41 type 1 diabetes subjects followed for 29.8 (6-57) months after CIT who received sirolimus and tacrolimus. HbA(1c) improved by 3 months (6.1 +/- 0.5 vs. 8.1 +/- 1.3%, p < 0.001) and was sustained. Over 4 years estimated GFR (eGFR) declined (repeated measures ANOVA: p = 0.0011). The median rate of change in eGFR was -0.39 mL/min/1.73 m(2)/month but was highly variable (range: +1.62 to -2.79 mL/min/1.73 m(2)/month). Progression of albuminuria was observed in ten individuals while regression of microalbuminuria was observed in only one (chi square = 22.51, df = 4, p = 0.0002). Despite improved glycemia, CIT and concomitant immunosuppression, was associated with a fall in eGFR and progression of albuminuria over 4 years of observation. The rate of decline in eGFR was extremely variable and difficult to predict. The risk of progressive nephrotoxicity with decline in eGFR should be discussed with prospective CIT candidates and the risk: benefit ratio carefully considered in individuals with pre-existing renal impairment.     

Low Plasma Dehydroepiandrosterone Sulfate Level and its Relationship to Adiponectin in Hemodialysis Patients

The aim of the present study was to assess the relationship between plasma DHEA-S and adiponectin concentrations in hemodialyses patients (HD). Plasma adiponectin, DHEA-S, cholesterol, and albumin levels were estimated in 94 HD and 46 healthy subjects (HS). In HD, a significantly lower plasma DHEA-S concentration (2.5±0.2 vs. 4.7±0.4 μmol/L respectively; p?=?0.002) but significantly higher plasma adiponectin level (15.0±0.7 vs. 8.7±0.8 μg/mL respectively; p?=?0.004) than in HS were found. Only in uremic patients was a significant negative correlation found between plasma adiponectin and DHEA-S concentrations (tau?=?–0.210; p?=?0.001). Decreased plasma DHEA-S level is associated with increased adiponectinemia in uremic patients.     

Composite Islet-Endothelial Cell Grafts: A Novel Approach to Counteract Innate Immunity in Islet Transplantation

An instant blood-mediated inflammatory reaction (IBMIR) is elicited when islets come in contact with blood after intraportal transplantation. In contrast, endothelial cells (EC) readily tolerate contact with blood. A conceivable strategy to overcome IBMIR would be to create composite islet-EC grafts. Human islets were co-cultured with primary human aortic endothelial cells (HAEC) for 2-7 days to obtain 50-90% coverage. HAEC-coated islets were exposed to ABO-identical blood and analyzed with regard to clotting time, signs of inflammation and cell infiltration. Composite islet-HAEC graft survival was assessed after transplantation to athymic (nu/nu) nude mice. Exposed to blood, HAEC-coated islets induced less activation of coagulation and complement compared to control islets. Also, platelet and leukocyte consumption in blood was decreased. Clots with entrapped HAEC-coated islets showed less infiltration of CD11b+ cells. The extent of protection correlated to the level of HAEC coverage. Transplanted composite grafts stained positive for insulin and PECAM-1 demonstrating presence of both islets and HAEC within the islet graft 7 weeks after transplantation. Composite islet-HAEC grafts reduce all components of IBMIR. Refinement of the technique will allow introduction of composite islet-EC grafts in clinical islet transplantation, using autologous EC expanded in vitro and kept frozen until allogeneic islets become available for that specific recipient.     

低分子肝素钠股动脉注射治疗糖尿病下肢血管病变疗效观察

目的观察低分子肝素钠股动脉注射治疗糖尿病下肢血管病变的疗效。方法对40例糖尿病下肢血管病变患者在治疗糖尿病的基础上给予低分子肝素钠股动脉注射。观察治疗后临床症状、血液流变学以及血流动力学改善情况。结果治疗后患者临床症状、血液流变学以及血流动力学改善明显,治疗前后比较,差异有显著性意义(P<0.05,P<0.01);未发现不良反应。结论低分子肝素钠股动脉注射对糖尿病下肢血管病变疗效显著,安全。     

A Comparison of Low Molecular Weight Heparin and Low Dose Unfractionated Heparin Prophylaxis in Subacute Myelopathy

Abstract

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are common life threatening complications of acute myelopathy. Prophylaxis with low dose unfractionated heparin (LDUH) has been the standard of care. Studies suggest that low molecular weight heparin (LMWH) has superior efficacy, but advantages may be offset by higher expense. Since LMWH (enoxaparin sodium) became available, standard practice at our institution has been to treat all inpatients with myelopathy with LMWH. To examine the impact of this practice, all inpatients diagnosed with myelopathy and treated with LMWH were sequentially matched by diagnosis and compared in a retrospective review with inpatients treated with LDUH. In each group, 11 patients had traumatic injury, four had transverse myelitis, four had neoplasms and five had spinal stenosis. Characteristics of the LMWH/LDUH groups were: mean age - 48.5/50.4; spinal level - cervical 13/7, thoracic 9/12, lumbar 2/5; American Spinal Injury Association impairment scale - A, 8/9; B, 2/2; C, 8/5; D, 6/8. There were five DVTs and two PEs in five patients taking LDUH; there were no cases of DVT or of PE in the LMWH group (p=0.04, two-tailed chi-square test). Isolated DVTs occurred in two patients with traumatic injuries and in one patient with transverse myelitis; PE + DVT occurred in one patient with a primary and one patient with a metastatic tumor. All developed within 3.5 months of the onset of spinal dysfunction. One patient with a traumatic injury on ibuprofen and dexamethasone had a gastrointestinal hemorrhage while receiving LMWH. The cost of administration of LMWH was $24,499 compared with $5,700 for LDUH. The LDUH group spent a total of 57 days in an acute care facility, costing $57,000.00 and patients treated with LMWH spent nine days, costing $9,000.00. We conclude that treatment with LMWH was associated with a significant decrease in incidence of DVT/PE and an overall decline in health care costs of approximately $30,000 or approximately $1,250 per patient. (J Spinal Cord Med 1997;20:402-405)     

Incomplete Reversal of Enoxaparin Toxicity by Protamine: Implications of Renal Insufficiency,Obesity, and Low Molecular Weight Heparin Sulfate Content

The use of low molecular weight heparin (LMWH) is increasing throughout North America and Europe for a number of reasons: 1) ease of use; 2) predictable dose response; 3) less heparin associated thrombocytopenia. However, aside from increased costs, LMWH has significant potential drawbacks: 1) poor reversibility; 2) tendency to accumulate in renal insufficiency; 3) less experience in subset patient groups such as morbid obesity. We report a case of a postoperative morbidly obese patient who developed enoxaparin toxicity secondary to acute renal failure that did not reverse with protamine sulfate infusion. In addition, we review the use of LMWH in renal insufficiency, dosing in obese patients,and the importance of sulfate content in the efficacy of protamine sulfate as a reversing agent for LMWH.     

Clinical and Experimental Pancreatic Islet Transplantation to Striated Muscle: Establishment of a Vascular System Similar to That in Native Islets

OBJECTIVE

Curing type 1 diabetes by transplanting pancreatic islets into the liver is associated with poor long-term outcome and graft failure at least partly due to inadequate graft revascularization. The aim of the current study was to evaluate striated muscle as a potential angiogenic site for islet transplantation.

RESEARCH DESIGN AND METHODS

The current study presents a new experimental model that is found to be applicable to clinical islet transplantation. Islets were implanted into striated muscle and intraislet vascular density and blood flow were visualized with intravital and confocal microscopy in mice and by magnetic resonance imaging in three autotransplanted pancreatectomized patients. Mice were rendered neutropenic by repeated injections of Gr-1 antibody, and diabetes was induced by alloxan treatment.

RESULTS

Contrary to liver-engrafted islets, islets transplanted to mouse muscle were revascularized with vessel densities and blood flow entirely comparable with those of islets within intact pancreas. Initiation of islet revascularization at the muscular site was dependent on neutrophils, and the function of islets transplanted to muscle was proven by curing diabetic mice. The experimental data were confirmed in autotransplanted patients where higher plasma volumes were measured in islets engrafted in forearm muscle compared with adjacent muscle tissue through high-resolution magnetic resonance imaging.

CONCLUSIONS

This study presents a novel paradigm in islet transplantation whereby recruited neutrophils are crucial for the functionally restored intraislet blood perfusion following transplantation to striated muscle under experimental and clinical situations.Transplantation of pancreatic tissue is today the only curative treatment for type 1 diabetes. Clinically, either the entire pancreas is transplanted into the abdominal cavity or isolated insulin producing islets of Langerhans are implanted into the liver through infusion via the portal vein. The former procedure is highly successful; the graft functions well following transplantation. However, it requires extensive surgery, whereas the latter procedure is attractive because only minor surgery is required in conscious recipients. Unfortunately, both function and survival of intrahepatically transplanted islets deteriorate with time (1). Delayed and insufficient islet revascularization (2), gluco- and lipotoxicity (3), presence of an instant blood-mediated inflammatory reaction (4,5), and toxicity of the immunosuppressive drugs present in high concentrations in the portal blood (6,7) are all factors believed to contribute to graft failure at this site.Native islets are highly vascularized, with blood perfusions ten times higher than in the exocrine pancreas (8,9). The islet microvasculature consists of a dense glomerular-like capillary network. A specific perfusion order of the different endocrine cell types has been shown in islets of Langerhans (10–15), enabling intraislet cell communication and further demonstrating the importance of a refined and adequate intraislet blood flow for normal islet function.Many of the factors contributing to poor islet function are associated with the liver as the site for engraftment (3,5,6,16,17), and for this reason other sites are now being investigated. The intramuscular site has attracted recent interest as a result of positive long-term outcome of autotransplantation of parathyroid glands to the brachioradialis muscle (18). Indeed, in a recent case report, we documented a successful 2-years follow-up of a child receiving autotransplanted islets into muscle (19).Myeloid-derived leukocytes have recently been shown to be involved in muscle healing and regeneration including angiogenesis (20,21); we therefore hypothesized that leukocytes may also be involved in the engraftment and revascularization of transplanted islets to muscle. To address this hypothesis, in addition to evaluation of striated muscle as a potential angiogenic site for islet transplantation, an in vivo mouse model was developed that enables studies of leukocyte–endothelial cell interactions and blood flow during revascularization of transplanted islets by intravital and confocal microscopy. Long-term islet function and survival following transplantation to muscle were evaluated in diabetic recipients. The results achieved in the experimental model were thereafter validated in patients receiving islets autotransplanted to muscle following pancreatectomy with a sophisticated magnetic resonance imaging technique.     

Heparin-Induced Hyperkalemia in Chronic Hemodialysis Patients: Comparison of Low Molecular Weight and Unfractionated Heparin

Abstract: Aldosterone suppression and subsequent hyperkalemia are well described reversible side effects of prolonged treatment with heparin. This study was designed to examine whether the discontinuous use of heparin three times a week to prevent thrombosis formation during hemodialysis sessions could also induce hypoaldosteronism and might contribute to increased predialysis kalemia in hemodialysis patients. Two different heparinization regimens were prospectively compared in a crossover study of 11 chronic hemodialysis patients. During 2 consecutive weeks, the patients were dialyzed each week with either their usual doses of unfractionated heparin (UH) (6,160 IU ± 1,350 IU) or low molecular weight heparin (LMWH) (15 anti-Xa activity [aXa] U/kg + 5 aXa U/kg/h). In all but 2 patients, the predialysis level of plasma K⁺ was higher with UH than with LMWH, and the mean value was higher (5.66 ± 0.83 versus 5.15 ± 0.68 mM, p = 0.01) while no differences in the predialysis plasma concentrations of creatinine, phosphate, urea, and bicarbonate were observed, excluding the potential role of differences in diet and dialysis efficacy in explaining the higher plasma K⁺ concentration with UH. The mean plasma aldosterone to plasma renin activity (pRA) ratio was higher with LMWH than with UH (149.54 ± 123.1 versus 111.91 ± 86.22 pg/ng/h, p < 0.05). Individual plasma aldosterone values were found to be correlated to pRAs both during the UH period and the LMWH period, and the slope of the positive linear relation between plasma aldosterone and pRA was lower during the UH treatment period (63 versus 105 pg/ng/h). Finally, a negative linear correlation was found between the differences in individual predialysis plasma K⁺ observed during the 2 protocols and the differences in the corresponding plasma aldosterone levels, suggesting a link between the higher kalemia and the lower aldosterone responsiveness to angiotensin with unfractionated heparin. Although it cannot be concluded whether or not LMWH inhibits aldosterone synthesis, should LMWH decrease aldosterone production, this side effect is 33% less marked than that of UH so that the predialysis plasma K⁺ levels are 10% lower. This property makes LMWH use preferable to that of UH in patients with elevated predialysis kalemia.     

A Comparison of Two Different Prophylactic Dose Regimens of Low Molecular Weight Heparin in Bariatric Surgery

Background: Deep venous thrombosis (DVT) is a significant risk in patients undergoing surgery for morbid obesity and may be associated with significant morbidity and mortality. In a consecutive group of patients in one bariatric surgery practice, the initial group of patients who received prophylaxis for DVT was given enoxaparin 30 mg q12h while the later group was given enoxaparin 40 mg q12h. Methods: 481 patients who underwent primary and revisional bariatric surgery over 38 months (October 1997 - December 2000) were evaluated. All patients received a multi-modality DVT prophylaxis protocol that included: early ambulation, graduated compression stockings, intermittent pneumatic compression, and enoxaparin (LMWH) in two dosage groups. The first 92 patients (19%) in the series (Group I) received LMWH 30 mg q12h while the subsequent 389 patients (81%) (Group II) received LMWH 40 mg q12h. Results: Group I patients were not different from Group II patients in body mass index (BMI) (51.7 vs 50.3 kg/m²), age (43.7 vs 44.3 yrs), sex (men 20.2% vs 15.8%) or history of previous DVT (3.2% vs 3.9%). Group I patients did have significantly longer procedure times (213 vs 175 min, p<0.05) and hospital stays (5.67 d vs 3.81 d, p<0.05) than Group II. There were a total of 7 (1.4%) postoperative DVT complications. 5 DVT complications occurred in Group I (5.4%) compared with 2 DVT complications in Group II (0.6%) (p < 0.01 by Fisher Exact Test two-tailed). One patient in each group required treatment for hemorrhage. Conclusion: A multi-modality prophylaxis treatment protocol in patients undergoing bariatric surgery is feasible and achieves a low incidence of postoperative DVT complications. The use of a higher dose of enoxaparin, 40 mg q12h, may reduce the incidence of DVT complications in patients following bariatric surgery without an increase in bleeding complications.     

Weight Gain and Acute Rejection in Patients Submitted to Pulmonary Transplantation: A Retrospective Cohort of 10 Years

Objective

Acute rejection is one of the most common complications after pulmonary transplantation. The aim of this work was to verify the association of nutritional status and weight gain with acute rejection in the recipient during the 1st year after pulmonary transplantation.

Long-term Treatment of Deep Venous Thrombosis with a Low Molecular Weight Heparin (Tinzaparin): A Prospective Randomized Trial

OBJECTIVES: Evaluation of the effectiveness and safety of the low molecular weight heparin (LMWH) tinzaparin versus unfractionated heparin (UFH) followed by acenocoumarol in proximal deep venous thrombosis (DVT). DESIGN: Prospective, randomized clinical trial. MATERIAL AND METHODS: Consecutive patients (n=108) with acute leg DVT, confirmed by duplex, were randomized to either tinzaparin alone or UFH and acenocoumarol for 6 months. Patients were evaluated ultrasonographically at entry, 1, 3, 6 and 12 months. Thrombus regression, reflux distribution and the incidence of complications were studied. A cost-analysis, comparing the two treatments, was performed. RESULTS: The overall incidence of major events (mortality, DVT recurrence, pulmonary embolism, major bleeding, heparin-induced thrombocytopenia) was significantly different (p=0.035) in favor of tinzaparin (7 versus 17 events). The ultrasonographic clot volume score (an index of recanalization) decreased significantly in both treatment groups. However, tinzaparin produced significantly more extended overall recanalization from 3 months onwards (p<0.02). Thrombus regression was equivalent or in favor of tinzaparin in the different DVT subgroups and venous segments, but the statistical significance varied. Reflux showed non-significant differences overall or in subgroups. A cost-analysis resulted in favor of LMWH. CONCLUSIONS: A fixed daily dose of tinzaparin for 6 months was at least as effective and safe as UFH and acenocoumarol. Regarding major events and recanalization, there was a significant benefit in favor of tinzaparin. Long-term DVT treatment with tinzaparin could represent an alternative to conventional treatment.     

Combined Islet and Hematopoietic Stem Cell Allotransplantation: A Clinical Pilot Trial to Induce Chimerism and Graft Tolerance

To prevent graft rejection and avoid immunosuppression-related side-effects, we attempted to induce recipient chimerism and graft tolerance in islet transplantation by donor CD34+hematopoietic stem cell (HSC) infusion. Six patients with brittle type 1 Diabetes Mellitus received a single-donor allogeneic islet transplant (8611 ± 2113 IEQ/kg) followed by high doses of donor HSC (4.3 ± 1.9 × 10⁶ HSC/kg), at days 5 and 11 posttransplant, without ablative conditioning. An 'Edmonton-like' immunosuppression was administered, with a single dose of anti-TNFα antibody (Infliximab) added to induction. Immunosuppression was weaned per protocol starting 12 months posttransplant. After transplantation, glucose control significantly improved, with 3 recipients achieving insulin-independence for a short time (24 ± 23 days). No severe hypoglycemia or protocol-related adverse events occurred. Graft function was maximal at 3 months then declined. Two recipients rejected within 6 months due to low immunosuppressive trough levels, whereas 4 completed 1-year follow-up with functioning grafts. Graft failure occurred within 4 months from weaning (478 ± 25 days posttransplant). Peripheral chimerism, as donor leukocytes, was maximal at 1-month (5.92 ± 0.48%), highly reduced at 1-year (0.20 ± 0.08%), and was undetectable at graft failure. CD25+T-lymphocytes significantly decreased at 3 months, but partially recovered thereafter. Combined islet and HSC allotransplantation using an 'Edmonton-like' immunosuppression, without ablative conditioning, did not lead to stable chimerism and graft tolerance.     

Pancreas‐After‐Islet Transplantation in Nonuremic Type 1 Diabetes: A Strategy for Restoring Durable Insulin Independence

Islet transplantation offers a minimally invasive approach for β cell replacement in diabetic patients with hypoglycemic unawareness. Attempts at insulin independence may require multiple islet reinfusions from distinct donors, increasing the risk of allogeneic sensitization. Currently, solid organ pancreas transplant is the only remaining surgical option following failed islet transplantation in the United States; however, the immunologic impact of repeated exposure to donor antigens on subsequent pancreas transplantation is unclear. We describe a case series of seven patients undergoing solid organ pancreas transplant following islet graft failure with long‐term follow‐up of pancreatic graft survival and renal function. Despite highly variable panel reactive antibody levels prior to pancreas transplant (mean 27 ± 35%), all seven patients achieved stable and durable insulin independence with a mean follow‐up of 6.7 years. Mean hemoglobin A1c values improved significantly from postislet, prepancreas levels (mean 8.1 ± 1.5%) to postpancreas levels (mean 5.3 ± 0.1%; p = 0.0022). Three patients experienced acute rejection episodes that were successfully managed with thymoglobulin and methylprednisolone, and none of these preuremic type 1 diabetic recipients developed stage 4 or 5 chronic kidney disease postoperatively. These results support pancreas‐after‐islet transplantation with aggressive immunosuppression and protocol biopsies as a viable strategy to restore insulin independence after islet graft failure.