Improvement of canine islet yield by donor pancreas infusion with a p38MAPK inhibitor

Nrf2: Therapeutic target of islet function protection in diabetes and islet transplantation

Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been reported as a major intracellular regulator of antioxidant stress, notably in islet β cells with low antioxidant enzyme content. Nrf2 is capable of regulating antioxidant function, while it can also regulate insulin secretion, proliferation, and differentiation of β cells, ER stress, as well as mitochondrial function. Thus, Nrf2 pharmacological activators have been employed in the laboratory for the treatment of diabetic mice. Islet cells are exposed to oxidative environment when islet is being transplanted. Accordingly, less than 50% of islet cells are well transplanted, and their normal function is maintained. The pharmacological activation of Nrf2 has been confirmed to protect islet cells at different stages of transplantation stages during experiments for islet transplantation.

Pancreas Preservation with a Neutrophil Elastase Inhibitor, Alvelestat, Contributes to Improvement of Porcine Islet Isolation and Transplantation

For pancreatic islet transplantation, pancreas procurement, preservation, and islet isolation destroy cellular and non-cellular components and activate components such as resident neutrophils, which play an important role in the impairment of islet survival. It has been reported that inhibitors of neutrophil elastase (NE), such as sivelestat and α1-antitrypsin, could contribute to improvement of islet isolation and transplantation. In this study, we investigated whether pancreatic preservation with alvelestat, a novel NE inhibitor, improves porcine islet yield and function. Porcine pancreata were preserved with or without 5 μM alvelestat for 18 h, and islet isolation was performed. The islet yields before and after purification were significantly higher in the alvelestat (+) group than in the alvelestat (−) group. After islet transplantation into streptozotocin-induced diabetic mice, blood glucose levels reached the normoglycemic range in 55% and 5% of diabetic mice in the alvelestat (+) and alvelestat (−) groups, respectively. These results suggest that pancreas preservation with alvelestat improves islet yield and graft function and could thus serve as a novel clinical strategy for improving the outcome of islet transplantation.

p38MAPK Signaling Pathway in Osteoarthritis: Pathological and Therapeutic Aspects

Osteoarthritis (OA) is an aging-related joint disease, pathologically featured with degenerated articular cartilage and deformation of subchondral bone. OA has become the fourth major cause of disability in the world, imposing a huge economic burden. At present, the pathogenesis and pathophysiology of OA are still unclear. Complex regulating networks containing different biochemical signaling pathways are involved in OA pathogenesis and progression. The p38MAPK signaling pathway is a member of the MAPK signaling pathway family, which participates in the induction of cellular senescence, the differentiation of chondrocytes, the synthesis of matrix metalloproteinase (MMPs) and the production of pro-inflammatory factors. In recent years, studies on the regulating role of p38MAPK signaling pathway and the application of its inhibitors have attracted growing attention, with an increasing number of in vivo and in vitro studies. One interesting finding is that the inhibition of p38MAPK could suppress chondrocyte inflammation and ameliorate OA, indicating its therapeutic role in OA treatment. Based on this, we reviewed the mechanisms of p38MAPK signaling pathway in the pathogenesis of OA, hoping to provide new ideas for future research and OA treatment.

A comparison of the inflammatory response following autologous compared with allogenic islet cell transplantation

Background

The initial response to islet transplantation and the subsequent acute inflammation is responsible for significant attrition of islets following both autologous and allogenic procedures. This multicentre study compares this inflammatory response using cytokine profiles and complement activation.

Methods

Inflammatory cytokine and complement pathway activity were examined in two cohorts of patients undergoing total pancreatectomy followed either by autologous (n=11) or allogenic (n=6) islet transplantation. Two patients who underwent total pancreatectomy alone (n=2) served as controls.

Results

The peak of cytokine production occurred immediately following induction of anaesthesia and during surgery. There was found to be a greater elevation of the following cytokines: TNF-alpha (P<0.01), MCP-1 (P=0.0013), MIP-1α (P=0.001), MIP-1β (P=0.00020), IP-10 (P=0.001), IL-8 (P=0.004), IL-1α (P=0.001), IL-1ra (0.0018), IL-10 (P=0.001), GM-CSF (P=0.001), G-CSF (P=0.0198), and Eotaxin (P=0.01) in the allogenic group compared to autografts and controls. Complement activation and consumption was observed in all three pathways, and there were no significant differences in between the groups although following allogenic transplantation ∆IL-10 and ∆VEGF levels were significantly elevated those patients who became insulin-independent compared with those who were insulin-dependent.

Conclusions

The cytokine profiles following islet transplantation suggests a significantly greater acute inflammatory response following allogenic islet transplantation compared with auto-transplantation although a significant, non-specific inflammatory response occurs following both forms of islet transplantation.

Pancreas preservation in extracellular-type p38 inhibitor-containing solution improves islet yield for porcine islet isolation

BACKGROUND

For islet transplantation, pancreas preservation and islet isolation activate p38, which is a member of the stress-activated group of mitogen-activated protein kinases (MAPKs). In this study, we evaluated an extracellular-type p38 inhibitor-containing (EP) solution with University of Wisconsin (UW) solution, the gold standard for organ preservation. The EP solution has high sodium-low potassium composition with low viscosity compared to UW solution. Moreover, EP solution contains a recently developed p38 inhibitor (11R-p38I₁₁₀ ) from our laboratory.

METHODS

Porcine pancreata were preserved in UW, EP, or EP-P solution (EP solution without 11R-p38I₁₁₀ ), and then islet isolation was performed. An optimized number (1500 IE) of isolated islets from each group were transplanted into streptozotocin-induced diabetic mice.

RESULTS

The islet yield before and after purification was significantly higher in the EP group than in the UW group. The islet yield before and after purification was not significantly different between the EP and EP-P groups; however, the EP solution prevented a reduction in the number of islets during culture. Western blot analysis showed that p38 activation was attenuated by EP solution. For islet transplantation into streptozotocin-induced diabetic mice, pancreas preservation in EP solution improved the outcome of islet transplantation.

CONCLUSIONS

Pancreas preservation with EP solution preserved islet function better than with UW solution. The advantages of EP solution over UW solution may include the inhibition of p38 activity as well as the composition of the solution.

Novel cell-permeable p38-MAPK inhibitor efficiently prevents porcine islet apoptosis and improves islet graft function

During islet transplantation, mitogen-activated protein kinase (MAPK) p38 is preferentially activated in response to the isolation of islets and the associated inflammation. Although therapeutic effects of p38 inhibitors are expected, the clinical application of small-molecule inhibitors of p38 is not recommended because of their serious adverse effects on the liver and central nervous system. Here we designed peptides to inhibit p38, which were derived from the sites on p38 that mediate binding to proteins such as MAPK kinases. Peptide 11R-p38I₁₁₀ significantly inhibited the activation of p38. To evaluate the effects of 11R-p38I₁₁₀ , porcine islets were incubated with 10 µmol/L 11R-p38I₁₁₀ or a mutant form designated 11R-mp38I₁₁₀ . After islet transplantation, blood glucose levels reached the normoglycemic range in 58.3% and 0% of diabetic mice treated with 11R-p38I₁₁₀ or 11R-mp38I₁₁₀ , respectively. These data suggest that 11R-p38I₁₁₀ inhibited islet apoptosis and improved islet function. Peptide p38I₁₁₀ is a noncompetitive inhibitor of ATP and targets a unique docking site. Therefore, 11R-p38I₁₁₀ specifically inhibits p38 activation, which may avoid the adverse effects that have discouraged the clinical use of small-molecule inhibitors of p38. Moreover, our methodology to design "peptide inhibitors" could be used to design other inhibitors derived from the binding sites of proteins.

Potential Benefits of Nrf2/Keap1 Targeting in Pancreatic Islet Cell Transplantation

Permanent pancreatic islet cell destruction occurs in type 1 diabetes mellitus (T1DM) through the infiltration of inflammatory cells and cytokines. Loss of β-cell integrity secondary to oxidation leads to an inability to appropriately synthesize and secrete insulin. Allogenic islet cell transplantation (ICT) has risen as a therapeutic option to mitigate problematic hypoglycemia. Nevertheless, during the process of transplantation, islet cells are exposed to oxidatively caustic conditions that severely decrease the islet cell yield. Islet cells are at a baseline disadvantage to sustain themselves during times of metabolic stress as they lack a robust anti-oxidant defense system, glycogen stores, and vascularity. The Nrf2/Keap1 system is a master regulator of antioxidant genes that has garnered attention as pharmacologic activators have shown a protective response and a low side effect profile. Herein, we present the most recently studied Nrf2/Keap1 activators in pancreas for application in ICT: Dh404, dimethyl fumarate (DMF), and epigallocatechin gallate (EGCG). Furthermore, we discuss that Nrf2/Keap1 is a potential target to ameliorate oxidative stress at every step of the Edmonton Protocol.

Inflammatory biomarkers in the blood and pancreatic tissue of organ donors that predict human islet isolation success and function

The pancreas of brain-dead donors is the primary source of islets for transplantation. However, brain death mediates systemic inflammation, which may affect the quantity and quality of isolated islets. Our aim was to identify inflammatory biomarkers in donor blood and/or pancreatic tissue capable of predicting islet isolation success. Blood samples were collected from 21 pancreas donors and 14 healthy volunteers. Pancreatic tissue samples were also collected from the corresponding donor during organ procurement. Six serum cytokines were measured by a fluorescent bead-based immunoassay, and the expression of fifteen inflammatory target genes was quantified by quantitative reverse transcription polymerase chain reaction (RT-qPCR). There was no correlation between serum inflammatory cytokines and mRNA expression of the corresponding genes in peripheral blood mononuclear cells (PBMCs) or pancreatic tissue. The IL6 expression in pancreatic tissue correlated negatively with post-isolation islet yield. Islets isolated from donors highly expressing IFNG in PBMCs and MAC1 in pancreatic tissue functioned poorly in vivo when transplanted in diabetic NODscid mice. Furthermore, the increased MAC1 in pancreatic tissue was positively correlated with donor hospitalization time. Brain death duration positively correlated with higher expression of IL1B in PBMCs and TNF in both PBMCs and pancreatic tissue but failed to show a significant correlation with islet yield and in vivo function. The study indicates that the increased inflammatory genes in donor pancreatic tissues may be considered as biomarkers associated with poor islet isolation outcome.

Regulation of c-Jun NH2-Terminal Kinase for Islet Transplantation

Islet transplantation has been demonstrated to provide superior glycemic control with reduced glucose lability and hypoglycemic events compared with standard insulin therapy. However, the insulin independence rate after islet transplantation from one donor pancreas has remained low. The low frequency of islet grafting is dependent on poor islet recovery from donors and early islet loss during the first hours following grafting. The reduction in islet mass during pancreas preservation, islet isolation, and islet transplantation leads to β-cell death by apoptosis and the prerecruitment of intracellular death signaling pathways, such as c-Jun NH₂-terminal kinase (JNK), which is one of the stress groups of mitogen-activated protein kinases (MAPKs). In this review, we show some of the most recent contributions to the advancement of knowledge of the JNK pathway and several possibilities for the treatment of diabetes using JNK inhibitors.

Attenuation of high glucose induced apoptotic and inflammatory signaling pathways in RIN-m5F pancreatic β cell lines by Hibiscus rosa sinensis L. petals and its phytoconstituents

ETHNOPHARMACOLOGICAL RELEVANCE

Hibiscus rosa sinensis petals possess wide range of pharmacological properties, with remarkable nutritional values. Diabetes is one of the most devastating diseases affecting the world today. A few side effects associated with the use of insulin and oral hypoglycemic agents prompted us to search new bioactive principles from antidiabetic plants used in traditional medicine.

AIM OF THE STUDY

The anti-diabetic therapeutic potential of the flavonoids rich ethyl acetate fraction of Hibiscus rosa sinensis petals (EHRS) was evaluated.

MATERIALS AND METHODS

High glucose (25 mM) induced apoptotic model of diabetes in RIN-m5F pancreatic β-cells was used for the study.

RESULTS

EHRS elevated the release of insulin in pancreatic cells and modulated apoptotic signaling cascades. It significantly reduced NF-κB nuclear translocation, thereby down-regulated the expressions of major inflammatory cytokines and up-regulated expressions of pancreatic β-cell functional genes such as, foxO-1, Ucn-3, Pdx-1, MafA and Nkx6.1. On comparison with its constituent phytochemicals, superior protective effect shown by EHRS may be due to the additive action of these phytoconstituents.

CONCLUSIONS

Results of the present study suggest hibiscus petals as a natural source and functional food of potential therapeutics to protect pancreatic β-cells in experimental diabetes mellitus.

Positron Emission Tomography and Autoradiography of (18)F-Fluorodeoxyglucose Labeled Islets With or Without Warm Ischemic Stress in Portal Transplanted Rats

OBJECTIVE

The use of positron-emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) -labeled islets has been considered to be a potential modality to visualize and quantify early engraftment of islet transplantation. The objective of this study was to evaluate the early islets' survival of the FDG-labeled islets with or without warm ischemic stress in portal transplanted rats using PET and autoradiography.

METHODS

Islets were isolated from Lewis rat pancreata with or without 30-minute warm ischemia times (WITs). For islets' labeling, 300 islets were incubated with 3 MBq FDG for 60 minutes. FDG-labeled islets were transplanted into the liver via portal vein. In in vivo study, a PET study was scanned for 90 minutes and the FDG uptake was expressed as percentage of liver injection dose (ID). In ex vivo study, the liver was exposed for 30 minutes with single fluorescence autoradiography.

RESULTS

In the PET study, the percentage of liver ID of the islets without WIT was 27.8 and that of the WIT islets was 20.1 at the end of islet transplantation. At 90 minutes after transplantation, the percentage of liver ID was decreased to 14.7 in the islets without WIT and 10.1 in the WIT islets. In the autoradiogram, the number of hot spots was more obviously visualized in the liver transplanted without WIT islets than in the liver transplanted with WIT islets.

CONCLUSION

Almost 50% of the islets were immediately lost in both the islets without WIT and those with WIT transplantation in the early period. However, islet survival was 1.4 times higher in the islets without WIT than that in those with WIT in the early engraftment phase.

Involvement of a proapoptotic gene (BBC3) in islet injury mediated by cold preservation and rewarming

Long-term pancreatic cold ischemia contributes to decreased islet number and viability after isolation and culture, leading to poor islet transplantation outcome in patients with type 1 diabetes. In this study, we examined mechanisms of pancreatic cold preservation and rewarming-induced injury by interrogating the proapoptotic gene BBC3/Bbc3, also known as Puma (p53 upregulated modulator of apoptosis), using three experimental models: 1) bioluminescence imaging of isolated luciferase-transgenic ("Firefly") Lewis rat islets, 2) cold preservation of en bloc-harvested pancreata from Bbc3-knockout (KO) mice, and 3) cold preservation and rewarming of human pancreata and isolated islets. Cold preservation-mediated islet injury occurred during rewarming in "Firefly" islets. Silencing Bbc3 by transfecting Bbc3 siRNA into islets in vitro prior to cold preservation improved postpreservation mitochondrial viability. Cold preservation resulted in decreased postisolation islet yield in both wild-type and Bbc3 KO pancreata. However, after culture, the islet viability was significantly higher in Bbc3-KO islets, suggesting that different mechanisms are involved in islet damage/loss during isolation and culture. Furthermore, Bbc3-KO islets from cold-preserved pancreata showed reduced HMGB1 (high-mobility group box 1 protein) expression and decreased levels of 4-hydroxynonenal (4-HNE) protein adducts, which was indicative of reduced oxidative stress. During human islet isolation, BBC3 protein was upregulated in digested tissue from cold-preserved pancreata. Hypoxia in cold preservation increased BBC3 mRNA and protein in isolated human islets after rewarming in culture and reduced islet viability. These results demonstrated the involvement of BBC3/Bbc3 in cold preservation/rewarming-mediated islet injury, possibly through modulating HMGB1- and oxidative stress-mediated injury to islets.

Pancreatic islet transplantation: from dogs to humans and back again

Pancreatic islet transplantation is a cell-based therapy that provides a potential cure for type 1 diabetes mellitus. After the introduction of an automated method for islet isolation and steroid-free immunosuppressive protocols, reversal of diabetes by islet transplantation is now performed at major human medical centers around the world. Despite extensive use of animal models in islet transplantation research, practical concerns have slowed the introduction of the technique into clinical veterinary practice and only a small number of studies have reported results of transplantation in dogs with spontaneously occurring diabetes mellitus; however, recent advances in islet isolation and encapsulation may make it possible to perform islet transplantation without immunosuppression in companion animals. This review summarizes experimental and clinical studies of pancreatic islet transplantation in dogs, including future directions for cell therapy in animals with naturally occurring disease.

Mesobiliverdin IXα Enhances Rat Pancreatic Islet Yield and Function

The aims of this study were to produce mesobiliverdin IXα, an analog of anti-inflammatory biliverdin IXα, and to test its ability to enhance rat pancreatic islet yield for allograft transplantation into diabetic recipients. Mesobiliverdin IXα was synthesized from phycocyanobilin derived from cyanobacteria, and its identity and purity were analyzed by chromatographic and spectroscopic methods. Mesobiliverdin IXα was a substrate for human NADPH biliverdin reductase. Excised Lewis rat pancreata infused with mesobiliverdin IXα and biliverdin IXα-HCl (1-100 μM) yielded islet equivalents as high as 86.7 and 36.5%, respectively, above those from non-treated controls, and the islets showed a high degree of viability based on dithizone staining. When transplanted into livers of streptozotocin-induced diabetic rats, islets from pancreata infused with mesobiliverdin IXα lowered non-fasting blood glucose (BG) levels in 55.6% of the recipients and in 22.2% of control recipients. In intravenous glucose tolerance tests, fasting BG levels of 56 post-operative day recipients with islets from mesobiliverdin IXα infused pancreata were lower than those for controls and showed responses that indicate recovery of insulin-dependent function. In conclusion, mesobiliverdin IXα infusion of pancreata enhanced yields of functional islets capable of reversing insulin dysfunction in diabetic recipients. Since its production is scalable, mesobiliverdin IXα has clinical potential as a protectant of pancreatic islets for allograft transplantation.

Development of pancreas storage solutions: Initial screening of cytoprotective supplements for β-cell survival and metabolic status after hypothermic storage

Insulin-dependent diabetes mellitus is one of the leading causes of death world-wide. Donor-derived pancreas and Islet of Langerhans transplantation are potential cures; however, postmortem ischemia impacts islet quality. The murine βt3 cell line was employed as a model to study cell viability and proliferation after hypothermic storage by comparing Belzer's Machine Perfusion Solution with Unisol™ Solution. The objective was to determine which of these solutions provided the best base line support for βt3 cells and to screen potential cytoprotective additives to the solutions. Initial βt3 cell viability was similar in the two storage solutions; however, better proliferation was observed after storage in Unisol Solution. The caspase inhibitor, Q-VD-OPH, and α-tocopherol improved viability in both storage solutions, suggesting that apoptotic pathways may be responsible for cell death during hypothermic storage of βt3 cells. Analysis of apoptosis markers, caspase activity, and DNA laddering showed a reduction in apoptosis when these additives were included. The effects of Q-VD-OPH and α-tocopherol were also synergistic when employed together during either hypothermic exposure, post-hypothermic physiologic incubation, or combinations of hypothermic exposure and physiologic incubation. These results suggest that both supplements should be included in pancreas hypothermic storage solutions and in islet culture media during post-isolation culture prior to transplantation.

Significant improvement in islet yield and survival with modified ET-Kyoto solution: ET-Kyoto/Neutrophil elastase inhibitor

Although islet transplantation can achieve insulin independence in patients with type 1 diabetes, sufficient number of islets derived from two or more donors is usually required to achieve normoglycemia. Activated neutrophils and neutrophil elastase (NE), which is released from these neutrophils, can directly cause injury in islet grafts. We hypothesized that inhibition of NE improves islet isolation and islet allograft survival. We tested our hypothesis by examining the effects of modified ET-Kyoto solution supplemented with sivelestat, a NE inhibitor (S-Kyoto solution), on islet yield and viability in islet isolation and the effect of intraperitoneally injected sivelestat on islet graft survival in a mouse allotransplant model. NE and proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 increased markedly at the end of warm digestion during islet isolation and exhibited direct cytotoxic activity against the islets causing their apoptosis. The use of S-Kyoto solution significantly improved islet yield and viability. Furthermore, treatment with sivelestat resulted in significant prolongation of islet allograft survival in recipient mice. Furthermore, serum levels of IL-6 and TNF-α at 1 and 2 weeks posttransplantation were significantly higher in islet recipients than before transplantation. Our results indicated that NE released from activated neutrophils negatively affects islet survival and that its suppression both in vitro and in vivo improved islet yield and prolonged islet graft survival. The results suggest that inhibition of NE activity could be potentially useful in islet transplantation for patients with type 1 diabetes mellitus.

Laser scanning cytometry: principles and applications-an update

Laser scanning cytometer (LSC) is the microscope-based cytofluorometer that offers a plethora of unique analytical capabilities, not provided by flow cytometry (FCM). This review describes attributes of LSC and covers its numerous applications derived from plentitude of the parameters that can be measured. Among many LSC applications the following are emphasized: (a) assessment of chromatin condensation to identify mitotic, apoptotic cells, or senescent cells; (b) detection of nuclear or mitochondrial translocation of critical factors such as NF-κB, p53, or Bax; (c) semi-automatic scoring of micronuclei in mutagenicity assays; (d) analysis of fluorescence in situ hybridization (FISH) and use of the FISH analysis attribute to measure other punctuate fluorescence patterns such as γH2AX foci or receptor clustering; (e) enumeration and morphometry of nucleoli and other cell organelles; (f) analysis of progeny of individual cells in clonogenicity assay; (g) cell immunophenotyping; (h) imaging, visual examination, or sequential analysis using different probes of the same cells upon their relocation; (i) in situ enzyme kinetics, drug uptake, and other time-resolved processes; (j) analysis of tissue section architecture using fluorescent and chromogenic probes; (k) application for hypocellular samples (needle aspirate, spinal fluid, etc.); and (l) other clinical applications. Advantages and limitations of LSC are discussed and compared with FCM.

mRNA of the pro-apoptotic gene BBC3 serves as a molecular marker for TNF-α-induced islet damage in humans

AIMS/HYPOTHESIS

TNF-α plays important roles in the pathogenesis of type 1 and type 2 diabetes mellitus. In light of this, we examined the involvement of a pro-apoptotic gene, BBC3 (also known as PUMA), in TNF-α-mediated beta cell dysfunction and destruction in human islets.

METHODS

Human islets were exposed in vitro to TNF-α alone or in combination with IFN-γ. Gene expression was assessed by RT-PCR using a set of single islets. Protein abundance and cellular localisation of BBC3 were assessed by immunoblot and immunohistochemistry. A marginal number of islets were transplanted into diabetic NODscid mice to correlate in vivo islet function with BBC3 expression.

RESULTS

BBC3 and IL8 mRNA were upregulated in TNF-α-stimulated islets in a dose-dependent manner and enhanced through addition of IFN-γ, but not upregulated by IFN-γ alone. Immunohistochemistry revealed that TNF-α in combination with IFN-γ upregulated basal BBC3 abundance in the cytoplasm of beta cells along with the perinuclear clustering of mitochondria partially co-localised with BBC3. TNF-α alone did not induce beta cell death, but did abrogate preproinsulin precursor mRNA synthesis in response to high glucose stimulation, which was inversely associated with upregulation of BBC3 mRNA expression by TNF-α. Higher BBC3 mRNA expression in islets correlated with decreased graft function in vivo.

CONCLUSIONS/INTERPRETATION

These results suggest that BBC3 mRNA can serve as a molecular marker to detect early TNF-α-induced beta cell stress and may help identify islet-protective compounds for the treatment of diabetes.

Pancreatic islet allograft in spleen with immunosuppression with cyclosporine. Experimental model in dogs

PURPOSE

To study the functional behavior of the allograft with immunosuppression of pancreatic islets in the spleen.

METHODS

Five groups of 10 Mongrel dogs were used: Group A (control) underwent biochemical tests; Group B underwent total pancreatectomy; Group C underwent total pancreatectomy and pancreatic islet autotransplant in the spleen; Group D underwent pancreatic islet allograft in the spleen without immunosuppressive therapy; Group E underwent pancreatic islet allograft in the spleen and immunosuppression with cyclosporine. All of the animals with grafts received pancreatic islets prepared by the mechanical-enzymatic method - stationary collagenase digestion and purification with dextran discontinuous density gradient, implanted in the spleen.

RESULTS

The animals with autotransplant and those with allografts with immunosuppression that became normoglycemic showed altered results of intravenous tolerance glucose (p < 0.001) and peripheral and splenic vein plasmatic insulin levels were significantly lower (p < 0.001) in animals that had allografts with immunosuppression than in those with just autotransplants.

CONCLUSIONS

In the animals with immunosuppression with cyclosporine subjected to allograft of pancreatic islets prepared with the mechanical-enzymatic preparation method (stationary collagenase digestion and purification with dextran discontinuous density gradient), the production of insulin is decreased and the response to intravenous glucose is altered.

P38alpha-selective mitogen-activated protein kinase inhibitor for improvement of cultured human islet recovery

OBJECTIVES

We investigated whether the recovery of cultured human islets is improved through the addition of a p38alpha-selective mitogen-activated protein kinase inhibitor, SD-282, to clinically used serum-free culture medium.

METHODS

Immediately after isolation, islets were cultured for 24 hours in medium alone (control) or medium containing dimethyl sulfoxide, 0.1 microM SD-282, or 0.3 microM SD-282. Cytokine expression, apoptotic beta-cell percentage, and islet function were assessed postculture.

RESULTS

Expression of p38 and phosphorylated p38 in islets increased during culture. Interleukin 6 mRNA expression in cultured islets, as well as IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor released into the medium, was significantly reduced by adding SD-282. The apoptotic beta-cell percentage was significantly lower in islets cultured with 0.1 microM SD-282, but not 0.3 microM, as compared with the control. Stimulation indices measured in vitro were higher but without significance (P = 0.06); the function of transplanted islets in diabetic NOD-scid mice was also better in 0.1-microM SD-282 group as compared with control.

CONCLUSIONS

Better islet function was obtained by adding 0.1 microM SD-282 to the serum-free culture medium. This improvement was associated with suppression of cytokine production and prevention of beta-cell apoptosis. However, this beneficial effect was diminished at a higher concentration.

Microassay for glucose-induced preproinsulin mRNA expression to assess islet functional potency for islet transplantation

BACKGROUND

The capacity for insulin synthesis in islets is important for islet transplantation to succeed. We developed a microassay that evaluates the potency of human islets by measuring changes in glucose-induced human insulin gene (INS) expression using a single islet in octuplicate samples.

METHODS

Poly (A) messenger RNA (mRNA) was purified from a set of single handpicked human islets. Glucose-induced mature (postspliced) and premature (prespliced) insulin mRNA were quantified by reverse-transcriptase polymerase chain reaction using several insulin mRNA primers designed at different locations including, intron, exon, and an exon-intron junction.

RESULTS

The synthesis of premature INS mRNA was significantly increased in islets exposed to high glucose for 16 vs. 4 hr (P<0.01), whereas mature INS mRNA showed no difference. Glucose-induced premature INS mRNA synthesis was attenuated in heat-damaged islets. Stimulation index (SI) calculated by normalizing premature by mature INS mRNA (SI_INS mRNA) positively correlated with SI of insulin release (SI_16h insulin) from the same set of islets during 16-hr incubation in high or low glucose media, and SI of glucose-mediated insulin release obtained from the same islet lot in a perifusion system (n=12). Furthermore, linear multiple regression analysis using SI_INS mRNA and SI_16h insulin predicted islet transplantation outcome in nonobese diabetic (NOD) scid mice (n=8).

CONCLUSION

The measurement of glucose-induced premature INS mRNA normalized by mature INS mRNA can be used to assess the functional quality of human islets and may predict islet function after transplantation in type 1 diabetic patients.