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R V Rajotte

Publications and source records attributed to R V Rajotte.

At least 19 recordsLinked to original sources
PubMed2004

Improved survival of microencapsulated islets during in vitro culture and enhanced metabolic function following transplantation.

AIMS/HYPOTHESIS: The aim of this study was to determine whether a simple alginate capsule can prolong islet survival and function during long-term tissue culture. We also wanted to observe the ability of these encapsulated islets to restore glucose responsiveness to diabetic recipients, along with the quantity of islets required to do so. METHODS: We compared the recovery and metabolic function of encapsulated canine islets with that of non-encapsulated canine islets following 1, 2 or 3 weeks of tissue culture. These culture preparations were also transplanted into diabetic nude mice and compared for their ability to reverse diabetes. Furthermore, short-term cultured encapsulated and non-encapsulated islets were transplanted in varying numbers to determine the minimum dose required to normalise blood glucose and prolong recipient survival. RESULTS: Islet recovery following 1, 2 and 3 weeks of tissue culture was significantly higher when islets were encapsulated. When these islets were recovered at 1, 2 and 3 weeks and transplanted into diabetic nude mice, survival at 100 days was 100% for all encapsulated groups, versus 66%, 33% and 33% respectively for the non-encapsulated islets. Additionally, substantially fewer short-term cultured islets were required to normalise blood glucose when the islets were encapsulated. Recipients of encapsulated islets also had significantly longer survival times than recipients of non-encapsulated preparations. CONCLUSIONS/INTERPRETATION: This study demonstrates that encapsulation of islets with purified alginate improves islet survival and function in vitro and in vivo.

Animals↗
PubMed2004

Genetically engineered Sertoli cells are able to survive allogeneic transplantation.

The immunoprotective nature of the testis has led to numerous investigations for its ability to protect cellular grafts. Sertoli cells (SCs) are at least partially responsible for this immunoprotective environment and survive allogeneic and xenogeneic transplantation. The ability of SCs to survive transplantation leads to the possibility that they could be engineered to deliver therapeutic proteins. As a model to test this hypothesis, we examined the ability of SCs that produce green fluorescent protein (GFP) to survive transplantation and continue expressing GFP. SCs were isolated from transgenic mice engineered to express GFP and transplanted as aggregates under the kidney capsule of severe combined immunodeficient (SCID) and Balb/c mice. Using this paradigm, it was possible to compare the survival of transgenic SCs directly in both immunodeficient and immunocompetent recipients. Fluorescence microscopy of the kidney capsule and immunohistochemistry of the grafts for GFP and GATA-4 revealed the presence of GFP-expressing SCs under the kidney capsule of SCID and Balb/c mice at both 30 and 60 days post-transplantation. In contrast, islets transplanted to Balb/c mice were rejected. Thus, SCs survive transplantation and continue to express GFP raising the possibility that SCs can be engineered using transgenic technology to produce proteins, such as insulin, factor VIII, or dopamine for the treatment of diabetes, hemophilia or Parkinson's disease, respectively.

Animals↗
PubMed2004

Heterogenous expression of nestin in human pancreatic tissue precludes its use as an islet precursor marker.

The discovery of a pancreatic adult stem cell would have significant implications for cell-based replacement therapies for type 1 diabetes mellitus. Nestin, a marker for neural precursor cells, has been suggested as a possible marker for islet progenitor cells. We have characterized the expression and localization of nestin in both the intact human pancreas and clinical human pancreatic islet grafts. Nestin was found to be expressed at different levels in the acinar component of human pancreatic biopsies depending on donor, as well as in ductal structures and islets to some degree. In islets, insulin-producing beta-cells rarely co-expressed the protein, and in the ducts a small percentage (1-2%) of cells co-expressed nestin and cytokeratin 19 (CK19) while most expressed only CK19 (90%) or nestin (5-10%) alone. Assessment of nestin expression in neonatal pancreatic sections revealed an increased number of islet-associated positive cells as compared with adult islets. Nestin immunoreactivity was also found in cells of the pancreatic vasculature and mesenchyme as evidenced by co-localization with smooth muscle actin and vimentin. Samples from post-islet isolation clinical islet grafts revealed a pronounced heterogeneity in the proportion of nestin-positive cells (<1-72%). Co-localization studies in these grafts showed that nestin is not co-expressed in endocrine cells and rarely (<5%) with cytokeratin-positive ductal cells. However, relatively high levels of co-expression were found with acinar cells and cells expressing the mesenchymal marker vimentin. In conclusion we have shown a diffuse and variable expression of nestin in human pancreas that may be due to a number of different processes, including post-mortem tissue remodeling and cellular differentiation. For this reason nestin may not be a suitable marker solely for the identification of endocrine precursor cells in the pancreas.

Analysis of Variance↗
PubMed2003

In vitro and in vivo expression of Galalpha-(1,3)Gal on porcine islet cells is age dependent.

The expression of Galalpha-(1,3)Gal (alphaGal) on porcine islet cells remains controversial. Several groups have reported that porcine islet endocrine cells do not express alphaGal while we have shown in neonatal porcine islets (NPI) that beta cells do express this antigen. We hypothesize that endocrine cells expressing alphaGal on NPI are less mature cells that may have originated from ductal cells and that expression of this antigen disappears as they develop into fully mature beta cells. Thus, we further examined alphaGal expression on various porcine islet cell preparations and correlated this with the proportion of cytokeratin 7 (CK7)-positive ductal cells. In vitro and in vivo expression of alphaGal and CK7 was significantly (P<0.05) higher in less mature NPI cells compared with matured NPI and adult porcine islet cells while the reverse was observed in the proportion of beta cells. Moreover, a significantly higher proportion of CK7-positive cells was detected in the Gal-expressing population compared with non-expressing cells. In contrast, a higher proportion of beta cells was observed in the Gal-negative population compared with the Gal-positive population. These data showed a reduced expression of alphaGal and CK7 as porcine islet cells mature into beta cells suggesting a possible role for alphaGal in the maturation of pancreatic endocrine beta cells.

Animals↗
PubMed2001

Novel approaches to cryopreservation of human pancreatic islets.

BACKGROUND: Optimized conditions for survival and function of human islets must be defined if sufficient islets are to be recovered from a single human donor pancreas to reverse type-1 diabetes after isolation, cryopreservation, and transplantation. The objective of this study was to compare the cryoprotective effect of ethylene glycol (EG) with the standard cryoprotectant, dimethyl sulfoxide (DMSO), on isolated human islet survival and function. Furthermore, the effect of different addition protocols and equilibrium concentrations of the cryoprotectants were studied. METHODS: Islets were isolated from human pancreata by using standard techniques of collagenase digestion and discontinuous Ficoll gradient purification. Aliquots of freshly isolated human islets were cryopreserved in six groups by using DMSO or EG. Cryoprotectants were added stepwise to produce a final concentration of 1.5 or 2.0 M, or added in a single step to a concentration of 1.5 M. Islets were cryopreserved by using established protocols and cultured for 48 hr at 37 degrees C before assessment of percentage of recovery and in vitro viability. RESULTS: After cryopreservation, percentage of recovery of islets was significantly higher in the group treated with 1.5 M of DMSO added in a stepwise protocol (74+/-3%, mean+/-SEM) compared with the standard 2.0 M of DMSO (62+/-4%) (P<0.05, unpaired t test, n=6). There was no difference between the recovery of islets cryopreserved with either 1.5 M of DMSO stepwise (74+/-3%) or 1.5 M of DMSO one-step (69+/-3%). Islet recovery was higher in groups treated with DMSO compared with EG, regardless of concentration of cryoprotectant or addition protocol, although the difference was significant only when comparing DMSO and EG 1.5 M one-step. Furthermore, islets treated with 1.5 M of DMSO, added either stepwise (6.0+/-0.4) or in one-step (6.5+/-0.8), had significantly higher stimulation indices compared with islets treated with the standard cryoprotectant for human islets, 2.0 M of DMSO (4.5+/-0.5) (P<0.05). CONCLUSIONS: These results demonstrate that a lower concentration of DMSO (1.5 M) allows for the cryopreservation of human islets with superior survival and preservation of function post-culture compared with 2.0 M of DMSO and various concentrations of EG.

Cryopreservation↗
PubMed2001

Serine-protease inhibition during islet isolation increases islet yield from human pancreases with prolonged ischemia.

BACKGROUND: Islet isolation from the pancreatic tissue matrix remains highly variable. Recent evidence suggests that intrinsic human pancreatic proteases, including trypsin, may inhibit effective collagenase enzymatic activity during islet isolation, thereby impairing the isolation success. In this study we have hypothesized that serine protease inhibition applied during pancreatic digestion, could improve yield and/or functional viability of islets isolated from human pancreases. METHODS: Twelve organ donor pancreases with 12.9+/-0.6 hr cold storage (mean+/-SEM) were perfused via their ducts with Liberase-HI enzyme in the presence (n=6) or absence (n=6) of 0.4 mM Pefabloc. All were then gently dissociated and their purified islets separated with Ficoll density gradient centrifugation. RESULTS: Donor-related factors (age, gender, cold storage time, body mass index, and pancreas weight) did not differ significantly between the two experimental groups. Pefabloc supplementation did not affect the digestion time, islets remaining trapped in exocrine tissue, or final islet purity. Islet recovery was increased in the Pefabloc-treated group (mean+/-SEM yield 323.8+/-80.8 x 10(3) islet equivalents vs. 130.8+/-13.6 x 10(3) islet equivalents, P<0.05). Cellular composition, DNA and insulin content, and insulin secretory activity of the isolated islets was similar. CONCLUSIONS: Inhibition of intrinsic protease activity within pancreases after prolonged cold storage improves isolation of viable islets.

Adolescent↗
PubMed2001

Novel approaches toward early diagnosis of islet allograft rejection.

BACKGROUND: The inability to diagnose early rejection of an islet allograft has previously proved to be a major impediment to progress in clinical islet transplantation. The need to detect early rejection will become even more relevant as new tolerance-inducing protocols are evaluated in the clinic. We explored three novel approaches toward development of early diagnostic markers of islet rejection after islet allotransplantation. METHODS: (a) Canine islet allograft transplant recipients were immunosuppressed for 1 month, then therapy was withdrawn. Serum glutamic acid decarboxylase antigen (GAD65), an endogenous islet protein, was monitored daily with a CO2 release assay. (b) Rodent islets were genetically engineered to express a unique foreign protein (beta-galactosidase) by using adenoviral vectors, and after allograft transplantation, the viral-specific protein was measured in serum using optical luminescence. (c) Rodents receiving islet allografts were immunosuppressed temporarily, and daily glucose tolerance tests were followed until graft failure occurred. RESULTS: (a) Although serum monitoring of GAD65 antigen demonstrated elevated levels preceding loss of graft function in preliminary studies, the effect was not reproducible in all animals. (b) Genetically engineered rodent islets demonstrated normal insulin kinetics in vitro (insulin stimulation index 2.57+/-0.2 vs. 2.95+/-0.3 for control islets, P=ns), and purified viral protein products had a stable half-life of 8 hr in vivo. After islet allotransplantation, there were two peak elevations in serum viral proteins, confirming that an intra-islet "sentinel signal" could be detected serologically during acute rejection. There was no lead-time ahead of hyperglycemia, however. (c) Daily sequential intravenous glucose tolerance (IVGT) tests demonstrated evidence of allograft dysfunction (decline in KG) with a 2-day lead time to hyperglycemia (2.58+/-0.3 vs. 1.63+/-0.2%/min, respectively, P<0.001), with an accuracy of 89%, sensitivity of 78%, and specificity of 95%. CONCLUSIONS: Of the three diagnostic tests, metabolic assessment with an abbreviated IVGT was the most effective method of demonstrating early islet dysfunction due to rejection.

Animals↗
PubMed2001

Peroxynitrite is a mediator of cytokine-induced destruction of human pancreatic islet beta cells.

The proinflammatory cytokines, interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), and interferon gamma (IFNgamma), are cytotoxic to pancreatic islet beta cells, possibly by inducing nitric oxide and/or oxygen radical production in the beta cells. Peroxynitrite, the reaction product of nitric oxide and the superoxide radical, is a strong oxidant and cytotoxic mediator; therefore, we hypothesized that peroxynitrite might be a mediator of cytokine-induced islet beta-cell destruction. To test this hypothesis we incubated islets isolated from human pancreata with the cytokine combination of IL-1beta, TNFalpha, and IFNgamma. We found that these cytokines induced significant increases in nitrotyrosine, a marker of peroxynitrite, in islet beta cells, and the increase in nitrotyrosine preceded islet-cell destruction. Peroxynitrite mimicked the effects of cytokines on nitrotyrosine formation and islet beta-cell destruction. L-N(G)-monomethyl arginine, an inhibitor of nitric oxide synthase, prevented cytokine-induced nitric oxide production but not hydrogen peroxide production, nitrotyrosine formation, or islet beta-cell destruction. In contrast, guanidinoethyldisulphide, an inhibitor of inducible nitric oxide synthase and scavenger of peroxynitrite, prevented cytokine-induced nitric oxide and hydrogen peroxide production, nitrotyrosine formation, and islet beta-cell destruction. These results suggest that cytokine-induced peroxynitrite formation is dependent upon increased generation of superoxide (measured as hydrogen peroxide) and that peroxynitrite is a mediator of cytokine-induced destruction of human pancreatic islet beta cells.

Cell Death↗
PubMed2001

Clinical outcomes and insulin secretion after islet transplantation with the Edmonton protocol.

Islet transplantation offers the prospect of good glycemic control without major surgical risks. After our initial report of successful islet transplantation, we now provide further data on 12 type 1 diabetic patients with brittle diabetes or problems with hypoglycemia previous to 1 November 2000. Details of metabolic control, acute complications associated with islet transplantation, and long-term complications related to immunosuppression therapy and diabetes were noted. Insulin secretion, both acute and over 30 min, was determined after intravenous glucose tolerance tests (IVGTTs). The median follow-up was 10.2 months (CI 6.5-17.4), and the longest was 20 months. Glucose control was stable, with pretransplant fasting and meal tolerance-stimulated glucose levels of 12.5+/-1.9 and 20.0+/-2.7 mmol/l, respectively, but decreased significantly, with posttransplant levels of 6.3+/-0.3 and 7.5+/-0.6 mmol/l, respectively (P < 0.006). All patients have sustained insulin production, as evidenced by the most current baseline C-peptide levels 0.66+/-0.06 nmol/l, increasing to 1.29+/-0.25 nmol/l 90 min after the meal-tolerance test. The mean HbA1c level decreased from 8.3+/-0.5% to the current level of 5.8+/-0.1% (P < 0.001). Presently, four patients have normal glucose tolerance, five have impaired glucose tolerance, and three have post-islet transplant diabetes (two of whom need oral hypoglycemic agents and low-dose insulin (<10 U/day). Three patients had a temporary increase in their liver-function tests. One patient had a thrombosis of a peripheral branch of the right portal vein, and two of the early patients had bleeding from the hepatic needle puncture site; but these technical problems were resolved. Two patients had transient vitreous hemorrhages. The two patients with elevated creatinine levels pretransplant had a significant increase in serum creatinine in the long term, although the mean serum creatinine of the group was unchanged. The cholesterol increased in five patients, and lipid-lowering therapy was required for three patients. No patient has developed cytomegalovirus infection or disease, posttransplant lymphoproliferative disorder, malignancies, or serious infection to date. None of the patients have been sensitized to donor antigen. In 11 of the 12 patients, insulin independence was achieved after 9,000 islet equivalents (IEs) per kilogram were transplanted. The acute insulin response and the insulin area under the curve (AUC) after IVGTT were consistently maintained over time. The insulin AUC from the IVGTT correlated to the number of islets transplanted, but more closely correlated when the cold ischemia time was taken into consideration (r = 0.83, P < 0.001). Islet transplantation has successfully corrected labile type 1 diabetes and problems with hypoglycemia, and our results show persistent insulin secretion. After a minimum of 9,000 IEs per kilogram are provided, insulin independence is usually attained. An elevation of creatinine appears to be a contraindication to this immunosuppressive regimen. For the subjects who had labile type 1 diabetes that was difficult to control, the risk-to-benefit ratio is in favor of islet transplantation.

Adult↗
PubMed2001

Islet cryopreservation using intracellular preservation solutions.

Cryopreservation of islets adds great flexibility to clinical islet transplant programs. Methods of islet cryopreservation have traditionally utilized permeating cryoprotectants contained within isotonic solutions without specifically addressing issues of ionic balances, buffering capacity, or oxygen free radicals that occur during hypothermic stresses. These factors may become significant issues during low-temperature storage and during the freezing and thawing process. Since its development in the early 1980s, the University of Wisconsin (UW) organ preservation solution has become the standard vascular flush and preservation solution. Recently, Hypothermosol preservation solution (HTS) was developed as a hypothermic blood substitute. The unique characteristics and composition of these preservation solutions may be important when developing solutions specific for the cryopreservation of cells and tissues. It was the aim of this study to evaluate these two hypothermic preservation solutions as the media used in cryopreservation of islets. Groups of canine islets [5000 islet equivalents (IE)/group] were cryopreserved using the standard protocol of stepwise addition of dimethyl sulfoxide (DMSO) to 2 M, controlled nucleation, slow cooling (0.25 degrees C/min), and rapid thawing (200 degrees C/min). The cryopreservation solutions were made with 1) UW solution, 2) HTS solution, or 3) Medium 199 solution with 10% fetal calf serum (FCS). Additional control groups included islets cryopreserved using 4) HTS, 5) UW solution, and 6) Medium 199 alone, without DMSO. Recovery of islets immediately following thawing was equivalent between the groups with the exception of the islets cryopreserved without DMSO (groups 4-6, p < 0.05). After 48 h of postcryopreservation tissue culture, islet recovery was highest in the groups frozen with UW and HTS (mean +/- SEM) (79.8 +/- 1.9% and 82.5 +/- 1.5%, p < 0.05 vs. group 3, 69.1 +/- 3.3%, p < 0.05, ANOVA). Less than 15% of the islets were recovered when they were cryopreserved without the cryoprotectant DMSO (groups 4-6). Functional viability was assessed by measuring the glucose-stimulated insulin secretion during static incubation after 48-h culture. The stimulation indexes were 4.6 +/- 1.0, 4.2 +/- 0.8, 3.6 +/- 1.2, 0.6 +/- 0.5, and 0.4 +/- 0.2 for islets in groups 1-5, respectively. This study demonstrates that postcryopreservation survival can be improved using intracellular-based preservation solutions, including UW or HTS, in conjunction with DMSO.

Animals↗
PubMed2001

Osmotic and cryoprotectant permeation characteristics of islet cells isolated from the newborn pig pancreas.

The development of effective protocols for the low-temperature banking of pancreatic islets is an important step in islet transplantation for the treatment of type I diabetes mellitus. We have been exploring the use of islets from the newborn pig as an alternative source of tissue for transplantation. Current cryopreservation protocols are empirically derived, but may be optimized by modeling osmotic responses during the cryopreservation process. This study determined the osmotic and cryoprotectant permeability parameters of cells isolated from the pancreas of newborn pigs. Key parameters are: the osmotically inactive fraction of cell volume, hydraulic conductivity, the permeability coefficients of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) at varying temperatures, and the activation energies of these transport processes. Newborn pig islets were dispersed into single cells and kinetic and equilibrium cell volumes were recorded during osmotic excursions using an electronic particle counter interfaced to a computer. Data were fitted to theoretical descriptions of the osmotic responses of cells, based on the Kedem-Katchalsky approach. The hydraulic conductivity (Lp) in the absence of cryoprotectant was calculated as 0.050 +/- 0.005, 0.071 +/- 0.006, and 0.300 +/- 0.016 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively (mean +/- SEM, n = 7, 6, or 9). These values give an activation energy value of 16.69 kcal/mol when put into an Arrhenius plot. The solute permeability (Ps) values for 1 M DMSO were 0.89 +/- 0.12, 1.86 +/- 0.28, and 5.33 +/- 0.26 microm/min at 4 degrees C, 10 degrees C, and 22 degrees C, respectively (n = 11, 8, or 10) giving an activation energy of 15.98 kcal/mol. The Lp values for cells exposed to 1 M DMSO were 0.071 +/- 0.006, 0.084 +/- 0.008, and 0.185 +/- 0.014 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively. The activation energy for these values was 8.95 kcal/mol. The Ps values for 2 M DMSO were 1.11 +/- 0.13, 1.74 +/- 0.19, and 7.68 +/- 0.12 microm/min for the same temperatures, with a calculated activation energy of 17.89 kcal/mol. The Lp values in the presence of 2 M DMSO were 0.070 +/- 0.006, 0.085 +/- 0.008, and 0.192 +/- 0.009 microm/min/atm at 4 degrees C, 10 degrees C, and 22 degrees C, respectively, with an activation energy of 9.40 kcal/mol. Solutions of 1 M EG gave Ps values of 1.01 +/- 0.13, 1.45 +/- 0.25, and 4.90 +/- 0.48 microm/min at the three test temperatures. The resulting activation energy was 14.60 kcal/mol. The corresponding Lp values were 0.071 +/- 0.007, 0.068 +/- 0.006, and 0.219 +/- 0.012 microm/min/atm with an activation energy of 10.96 kcal/mol. The solute permeabilities in the presence of 2 M EG for newborn pig islet cells were 1.03 +/- 0.15, 1.42 +/- 0.23, and 5.56 +/- 0.22 microm/min; the activation energy was 15.70. The Lp values for cells in the presence of 2 M EG were 0.068 +/- 0.008, 0.071 +/- 0.006, and 0.225 +/- 0.010 microm/min/atm; the activation energy for these values was 11.49 kcal/mol. These key cryobiological parameters permit the mathematical modeling of osmotic responses of intact islets during the cryopreservation process, which may lead to further improvements in the low temperature storage of islets from newborn pigs.

Animals↗
PubMed2000

Glucose-dependent insulin release from genetically engineered K cells.

Genetic engineering of non-beta cells to release insulin upon feeding could be a therapeutic modality for patients with diabetes. A tumor-derived K-cell line was induced to produce human insulin by providing the cells with the human insulin gene linked to the 5'-regulatory region of the gene encoding glucose-dependent insulinotropic polypeptide (GIP). Mice expressing this transgene produced human insulin specifically in gut K cells. This insulin protected the mice from developing diabetes and maintained glucose tolerance after destruction of the native insulin-producing beta cells.

Animals↗
PubMed2000

Single injection of insulin delays the recurrence of diabetes in syngeneic islet-transplanted diabetic NOD mice.

BACKGROUND: Insulin has been implicated in the pathogenesis of type 1 diabetes and oral administration of insulin has been shown to delay the onset of diabetes in NOD mice. In this study we determined whether a single footpad injection of insulin will protect syngeneic islet grafts from autoimmune destruction when placed under the kidney capsule of diabetic NOD mice. METHODS: Five hundred islets were transplanted under the kidney capsule of diabetic female NOD mice in conjunction with a single footpad injection of either pork insulin in saline or mixed with incomplete Freund's adjuvant (IFA). Control groups received either IFA or saline alone. RESULTS: Seven of 11 animals (63.6%) given insulin in IFA exhibit long-term graft survival (>75 days; mean +/- SEM >85.4+/-16.1) whereas only 3 of 12 animals (25.0%) in the IFA group had graft survival longer than 75 days (mean +/- SEM >41.9+/-12.8 days). In contrast, none of the animals that received insulin in saline (17.3+/-2.5 days) and saline only (16.1+2.0 days) exhibit prolonged graft survival. CONCLUSION: These results suggest that a single footpad injection of insulin can protect the islet graft from immune attack in NOD mice.

Animals↗
PubMed2000

Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen.

BACKGROUND: Registry data on patients with type 1 diabetes mellitus who undergo pancreatic islet transplantation indicate that only 8 percent are free of the need for insulin therapy at one year. METHODS: Seven consecutive patients with type 1 diabetes and a history of severe hypoglycemia and metabolic instability underwent islet transplantation in conjunction with a glucocorticoid-free immunosuppressive regimen consisting of sirolimus, tacrolimus, and daclizumab. Islets were isolated by ductal perfusion with cold, purified collagenase, digested and purified in xenoprotein-free medium, and transplanted immediately by means of a percutaneous transhepatic portal embolization. RESULTS: All seven patients quickly attained sustained insulin independence after transplantation of a mean (+/-SD) islet mass of 11,547+/-1604 islet equivalents per kilogram of body weight (median follow-up, 11.9 months; range, 4.4 to 14.9). All recipients required islets from two donor pancreases, and one required a third transplant from two donors to achieve sustained insulin independence. The mean glycosylated hemoglobin values were normal after transplantation in all recipients. The mean amplitude of glycemic excursions (a measure of fluctuations in blood glucose concentrations) was significantly decreased after the attainment of insulin independence (from 198+/-32 mg per deciliter [11.1+/-1.8 mmol per liter] before transplantation to 119+/-37 mg per deciliter [6.7+/-2.1 mmol per liter] after the first transplantation and 51+/-30 mg per deciliter [2.8+/-1.7 mmol per liter] after the attainment of insulin independence; P<0.001). There were no further episodes of hypoglycemic coma. Complications were minor, and there were no significant increases in lipid concentrations during follow-up. CONCLUSIONS: Our observations in patients with type 1 diabetes indicate that islet transplantation can result in insulin independence with excellent metabolic control when glucocorticoid-free immunosuppression is combined with the infusion of an adequate islet mass.

Adult↗
PubMed2000

Microencapsulation of neonatal porcine islets: protection from human antibody/complement-mediated cytolysis in vitro and long-term reversal of diabetes in nude mice.

BACKGROUND: Recently, we have developed a simple and reliable method to efficiently isolate large numbers of neonatal porcine islets (NPI). We and others have shown that NPI are susceptible to cytolysis by the activation of human complement in vitro. Microencapsulation of islets may be one strategy to protect NPI from this form of rejection. We examined whether microencapsulation can prevent lysis of NPI induced by human antibody and complement in vitro and also assessed their ability to reverse hyperglycemia in diabetic nude mice. METHODS: NPI were microencapsulated with purified alginate, cultured for 2 days, then tested for sensitivity to fresh human serum using an established in vitro cytotoxicity assay or transplanted into alloxan-induced diabetic nude mice. RESULTS: Incubation of nonencapsulated NPI for 24 hr in the presence of fresh human serum resulted in a 53% loss of cellular insulin content, a 51% reduction in recoverable DNA content, and a marked reduction of insulin secretory responsiveness when compared with controls cultured in heat-inactivated human serum. In contrast, exposure of encapsulated islets to fresh human serum had no cytotoxic effect on the islets. Transplantation of 2000 encapsulated NPI i.p. into diabetic nude mice (n=16) corrected hyperglycemia in all mice within 8 weeks. Similar results were obtained when 2000 nonencapsulated NPI were implanted under the kidney capsule (n=10); however recipients of nonencapsulated NPI placed i.p. failed to obtain euglycemia and survived for only 3 weeks posttransplantation. CONCLUSION: Microencapsulation protects NPI from the cytotoxic effects of human antibody and complement and allows for long-term reversal of diabetes in nude mice.

Animals↗