Activation of c-Jun NH2-terminal kinase during islet isolation

Cordycepin protects islet β-cells against glucotoxicity and lipotoxicity via modulating related proteins of ROS/JNK signaling pathway

Type 2 diabetes mellitus (T2DM) is a common and multiple endocrine metabolic disease. When pancreatic β cell in case of dysfunction, the synthesis and secretion of insulin are reduced. This study is to explore the effect of cordycepin (the molecular formula C₁₀H₁₃N₅O₃), a natural adenosine isolated from Cordyceps militaris, on high glucose/lipid-induced glucotoxicity and lipotoxicity in INS-1 cells. Our results showed that cordycepin improved cell viability, improved cell energy metabolism and promoted insulin synthesis and secretion. The mechanism may be related to that cordycepin reduces intracellular reactive oxygen species (ROS), increases ATP content in cells, causes membrane depolarization and balances the steady state of Ca²⁺ concentration, cordycepin inhibits cell apoptosis, which may be related to the downregulation of proteins level of c-Jun N-terminal kinases (JNK) phosphorylation, cytochrome c (Cyt-c), Cleaved Capase-3, the mRNA level of JNK, Cyt-c, Capase-3 and upregulation of proteins/mRNA level of pancreatic and duodenal homeobox factor-1 (PDX-1). These results suggest that cordycepin can inhibit cell apoptosis and protect cell number by downregulating ROS/JNK mitochondrial apoptosis pathway under high glucose/lipid environment, thereby improving the function of pancreatic islet cells, providing a theoretical basis for the related research on the prevention and control of cordycepin on T2DM.

High Concentrations of Etanercept Reduce Human Islet Function and Integrity

Background

Most islet transplant groups worldwide routinely use the TNFα inhibitor Etanercept in their peri-transplant protocols. Surprisingly, there have been no published dose-response studies on the effects of Etanercept on human islets. Our study aimed to address this by treating cultured human islets with increasing concentrations of Etanercept.

Materials and Methods

Isolated human islets were cultured for 3–4 days in normoxic (21% oxygen) or in hypoxic (2% oxygen) atmosphere using Etanercept dissolved in a range of 2.5–40 µg/mL prior to islet characterisation.

Results

In normoxic atmosphere, it was found that 5 µg/mL is the most efficient dose to preserve islet morphological and functional integrity during culture. Increasing the dose to 10 µg/mL or more resulted in detrimental effects with respect to viability and glucose-stimulated insulin release. When human islets were cultured for 3 to 4 days in clinically relevant hypoxia and treated with 5 µg/mL Etanercept, post-culture islet survival (P < 0.001) and in vitro function (P < 0.01) were significantly improved. This correlated with a substantially reduced cytokine production (P < 0.05), improved mitochondrial function (P < 0.01), and reduced production of reactive oxygen species (P < 0.001) in hypoxia-exposed islets.

Conclusion

These findings suggest that the therapeutic window of Etanercept is very narrow and that this should be considered when optimising the dosage and route of Etanercept administration in islet-transplant recipients or when designing novel drug-delivering islet scaffolds.

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.

Cytokines in adipose-derived mesenchymal stem cells promote the healing of liver disease

Adipose-derived mesenchymal stem cells (ADSCs) are a treatment cell source for patients with chronic liver injury. ADSCs are characterized by being harvested from the patient's own subcutaneous adipose tissue, a high cell yield (i.e., reduced immune rejection response), accumulation at a disease nidus, suppression of excessive immune response, production of various growth factors and cytokines, angiogenic effects, anti-apoptotic effects, and control of immune cells via cell-cell interaction. We previously showed that conditioned medium of ADSCs promoted hepatocyte proliferation and improved the liver function in a mouse model of acute liver failure. Furthermore, as found by many other groups, the administration of ADSCs improved liver tissue fibrosis in a mouse model of liver cirrhosis. A comprehensive protein expression analysis by liquid chromatography with tandem mass spectrometry showed that the various cytokines and chemokines produced by ADSCs promote the healing of liver disease. In this review, we examine the ability of expressed protein components of ADSCs to promote healing in cell therapy for liver disease. Previous studies demonstrated that ADSCs are a treatment cell source for patients with chronic liver injury. This review describes the various cytokines and chemokines produced by ADSCs that promote the healing of liver disease.

Modified cell-permeable JNK inhibitors efficiently prevents islet apoptosis and improves the outcome of islet transplantation

We previously reported that treatment with a JNK inhibitory peptide (11R-JNKI) prevents islet apoptosis and enhances the islet function in vivo. In the present study, we explored more efficient JNK inhibitors. The inhibition of the JNK activity by five types of deletion peptides in 11R-JNKI was investigated. One of the peptides, 8R-sJNKI(-9), significantly prevented JNK activation. At a concentration of 1 µM, 8R-sJNKI(-9) inhibited JNK activity similarly to 10 µM 11R-JNKI and the inhibition of the JNK activity by 10 µM 8R-sJNKI(-9) was significantly greater than that by 10 µM 11R-JNK. To evaluate the effects of 8R-sJNKI(-9), porcine islets were cultured with 1 µM of 8R-sJNKI(-9) or 8R-mutant sJNKI(-9) (8R-mJNKI(-9)). After 1 day of culture, the numbers of islets in the 8R-sJNKI(-9)-treated group was significantly higher than that in the 8R-mJNKI(-9)-treated group. After islet transplantation, the blood glucose levels reached the normoglycemic range in 58.3% of streptozotocin-induced diabetic mice in the 8R-sJNKI(-9) group and 0% of the mice in the 8R-mJNKI(-9)-treated group. These data suggest that 8R-sJNKI(-9) inhibits islet apoptosis and improves islet function.

Low-adhesive ethylene vinyl alcohol-based packaging to xenogeneic islet encapsulation for type 1 diabetes treatment

Transplantation of encapsulated porcine islets is proposed to treat type 1 diabetes. However, the envelopment of fibrous tissue and the infiltration of immune cells impair islet function and eventually cause implant failure. It is known that hemodialysis using an ethylene vinyl alcohol (EVOH) membrane results in minor tissue responses. Therefore, we hypothesized that using a low-adhesive EVOH membrane for encapsulation may prevent host cell accumulation and fibrous capsule formation. In this study, rat islets suspended in chitosan gel were encapsulated in bags made from highly porous EVOH membranes, and their in vitro insulin secretion function as well as in vivo performance was evaluated. The results showed that the EVOH bag did not affect islet survival or glucose-stimulated insulin secretion. Whereas naked islets were dysfunctional after 7 days of culture in vitro, islets within the EVOH bag produced insulin continuously for 30 days. Streptozotocin-induced diabetic mice were given islets-chitosan gel-EVOH implants intraperitoneally (650-800 islets equivalent) and exhibited lower blood glucose levels and regained body weight during a 4-week observation period. The transplanted mice had higher levels of serum insulin and C-peptide, with an improved blood glucose disappearance rate. Retrieved implants had minor tissue adhesion, and histology showed a limited number of mononuclear cells and fibroblasts surrounding the implants. No invasion of host cells into the EVOH bags was noticed, and the encapsulated islets were intact and positive for insulin-glucagon immunostaining. In conclusion, an EVOH bag can protect encapsulated islets, limit fibrous capsule formation, and extend graft function.

Islet autotransplantation and total pancreatectomy

The goal of IAT is the preservation of beta-cell mass at the time of pancreatectomy. The majority of recipients have significant endogenous beta-cell function with positive blood C-peptide after surgery, even if only approximately one third achieve insulin independence. In appropriately selected patients, total pancreatectomy combined with IAT achieves relief of pain and improves quality of life with relatively easier-to-manage glycemic control and avoidance of hyper- and hypoglycemic episodes. Current research is focused on improving techniques of islet isolation and engraftment as well as long-term survival of autografted islets.

No islets left behind: islet autotransplantation for surgery-induced diabetes

For patients with severe chronic pancreatitis refractory to medical interventions, total pancreatectomy can be considered to relieve the root cause of pain. The goal of a simultaneous islet autotransplant is to prevent or minimize the otherwise inevitable surgical diabetes. Islet autotransplant can successfully preserve some endogenous islet function in the majority of recipients, which mediates protection against brittle diabetes. Most maintain reasonably good glycemic control, while 30 %-40 % successfully discontinue insulin therapy. With islet autotransplants reaching a wider clinical audience, refinements in islet isolation techniques and strategies to protect islet grafts post-transplant may further improve the success of this procedure.

Surgical protocol involving the infusion of paramagnetic microparticles for preferential incorporation within porcine islets

INTRODUCTION

Despite significant advances, widespread applicability of islet cell transplantation remains elusive. Refinement of current islet isolation protocols may improve transplant outcomes. Islet purification by magnetic separation has shown early promise. However, surgical protocols must be optimized to maximize the incorporation of paramagnetic microparticles (MP) within a greater number of islets. This study explores the impact of MP concentration and infusion method on optimizing MP incorporation within islets.

METHODS

Five porcine pancreata were procured from donors after cardiac death. Splenic lobes were isolated and infused with varying concentrations of MP (8, 16, and 32 × 10(8) MP/L of cold preservation solution) and using one of two delivery techniques (hanging bag versus hand-syringe). After procurement and infusion, pancreata were stored at 0°C to 4°C during transportation (less than 1 hour), fixed in 10% buffered formalin, and examined by standard magnetic resonance imaging (MRI) and histopathology.

RESULTS

T2*-weighted MRI showed homogeneous distribution of MP in all experimental splenic lobes. In addition, histologic analysis confirmed that MP were primarily located within the microvasculature of islets (82% to 85%), with few MP present in acinar tissue (15% to 18%), with an average of five to seven MP per islet (within a 5-μm thick section). The highest MP incorporation was achieved at a concentration of 16 × 10(8) MP/L using the hand-syringe technique.

CONCLUSION

This preliminary study suggests that optimization of a surgical protocol, MP concentrations, and applied infusion pressures may enable more uniform distribution of MP in the porcine pancreas and better control of MP incorporation within islets. These results may have implications in maximizing the efficacy of islet purification by magnetic separation.

Similar islet function in islet allotransplant and autotransplant recipients, despite lower islet mass in autotransplants

BACKGROUND

Despite high initial rates of insulin independence after islet allotransplant for type 1 diabetes, long-term islet function is suboptimal. Possible contributing factors include autoimmune recurrence, alloimmune rejection, or immunosuppressant medication toxicity. In contrast, islet autografts, infused at the time of pancreatectomy for chronic pancreatitis, are not subject to these variables. Islet function was compared in autograft and allograft recipients.

METHODS

Eight autograft and eight allograft recipients, insulin independent or requiring minimal insulin, were matched for similar duration posttransplant (mean 2.1±1.2 years). Eleven healthy control subjects were also enrolled. Subjects underwent oral and intravenous glucose tolerance testing and arginine stimulation testing.

RESULTS

Age, gender, body mass index, duration posttransplant, and hemoglobin A1c levels were similar between groups. Glucose tolerance was worse in transplant recipients compared with controls. Alloislet recipients received significantly more islet equivalents per kg body weight (IE/kg) than autograft recipients (9958±6229 IE/kg vs. 4589±1232 IE/kg, P=0.03). However, the glycemic response to oral glucose tolerance testing, the acute insulin response to glucose, and the acute insulin response to arginine did not differ significantly between islet allograft and autograft recipients.

CONCLUSIONS

Insulin secretion and glucose excursion were similar in allograft and autograft recipients, despite the latter group receiving less than half as many islets. Better preservation of islet mass in the autograft setting is likely related to the lack of autoimmunity, alloimmunity, and immunosuppressive drug toxicity, highlighting the potential for better outcomes in islet allotransplant for type 1 diabetes mellitus with refinements in immunosuppression.

Ductal injection of JNK inhibitors before pancreas preservation prevents islet apoptosis and improves islet graft function

Human islet isolation to obtain high-quality islets is still challenging. This study investigates how c-Jun NH2- terminal kinase (JNK ) is activated during human and porcine islet isolation. We also investigated whether ductal injection of preservation solution with JNK inhibitors improves islet isolation results by preventing apoptosis of islet cells. A low molecular weight inhibitor (SP600125) and a cell-permeable peptide inhibitor, the latter introduced by protein transduction technology, were used in porcine and human studies, respectively. JNK activity progressively increased during the isolation procedure. The addition of 10 microM JNK inhibitors into the ductal preservation solution prevented JNK activation during the isolation procedure and prevented islet apoptosis immediately after isolation. We incubated islets (2000 islet equivalents) for 24-48 hr and then transplanted them below the kidney capsule of streptozotocin-induced diabetic mice. The blood glucose levels reached normoglycemia in more than 80% of the JNK inhibitor-positive group, whereas less than 20% of the JNK inhibitor-negative group achieved normoglycemia. These findings suggest that the JNK pathway is the major mediator of islet deterioration during/immediately after isolation and that JNK inhibition before islet isolation could improve outcomes after pancreatic islet transplantation.

Pancreas preservation by the two-layer method: does it have a beneficial effect compared with simple preservation in University of Wisconsin solution?

A large number of reports have shown that the two-layer method (TLM), which employs oxygenated perfluorochemical (PFC) and University of Wisconsin (UW) solution, is superior to simple cold storage in UW in islet transplantation. However, two recent large-scale studies showed no beneficial effect of TLM compared with UW storage in human islet transplantation. We reevaluated the effect of TLM by following three groups: group 1: UW simple storage; group 2: TLM performed by multiorgan procurement teams (not specialists of islet isolation); and group 3: TLM performed by specialists of islet isolation (Noguchi and Matsumoto). There were no significant differences between groups 1 and 2, whereas islet yields were significantly higher in group 3 compared with either group 1 or 2. Our data suggest that exact, complete performance of TLM could improve the outcome of islet isolation and transplantation. In this review, we describe the mechanisms of the TLM, the procedure of preoxygenated TLM, and the several possibilities for the reasons of the discrepancy.

Impact of pancreatic cold preservation on rat islet recovery and function

BACKGROUND

Islet transplantation success depends on the number and quality of islets transplanted. This study aimed at exploring the molecular mechanisms associated with cold pancreas preservation and their impact on islet cell survival and function.

METHODS

Rat pancreata were stored in cold University of Wisconsin preservation solution for short (3 hr; control) or long (18 hr) cold ischemia times (CIT).

RESULTS

Pancreata exposed to long CIT yielded lower islet numbers and showed reduced cellular viability; isolated islets displayed higher levels of phosphorylated stress-activated protein kinase (c-jun N-terminal Kinase and Mitogen-Activated Protein Kinase-p38), and chemokine (C-C) ligand-3, and lower levels of vascular endothelial growth factor, interleukins (IL)-9 and IL-10. Islets obtained from long-CIT pancreata were functionally impaired after transplantation. Differential proteomic expression in pancreatic tissue after CIT included increased eukaryotic translation elongation factor-1-alpha-1 (apoptosis related) and reduced Clade-B (serine protease inhibitor).

CONCLUSIONS

Our study indicates that cold ischemia stimulates inflammatory pathways (chemokine (c-c)ligand-3, phosphorylation of c-jun N-terminal Kinase and mitogen-activated protein kinase-p38, and eukaryotic translation elongation factor-1-alpha-1) and decreases repair/cytoprotective pathways (IL-10, vascular endothelial growth factor, and Clade-B), all of which may negatively affect the quality and mass of islets obtained from a donor pancreas.

Recombinant Sendai Virus-Mediated Gene Transfer to Mouse Pancreatic Stem Cells

Efficient gene transfer into stem cells is essential for the basic research and for therapeutic applications in gene-modified regenerative medicine. Adenovirus (AdV) vectors, one of the most commonly used types of vectors, can mediate high, albeit transient, levels of expression of the transgene in pancreatic stem/progenitor cells. However, high multiplicity of infection (MOI) with AdV vectors can result in cellular toxicity. Therefore, AdV vectors have been of limited usefulness in clinical applications. In this study, we investigated the in vitro gene transfer efficiency of Sendai virus (SeV) vectors, a paramyxovirus vector that can efficiently introduce foreign genes without toxicity into several cell types, including pancreatic stem cells. The dose-dependent GFP expression of pancreatic stem cells transfected with SeV vectors after 48 h of culture at 37°C was observed. The transfection of pancreatic stem cells with SeV vectors and AdV vectors results in equal expression of the transgene (GFP expression) in the cells after 48 h of culture at 37°C. Although the transfection of pancreatic stem cells with AdV vectors at high MOIs was cytotoxic, transfection with SeV vectors at high MOIs was rarely cytotoxic. In addition, pancreatic stem cells transfected with SeV maintained their differentiation ability. These data suggest that SeV could provide advantages with respect to safety issues in gene-modified regenerative medicine.

Differential Ability of Somatic Stem Cells

Somatic stem cells can be isolated from a variety of sources. Although some studies have suggested that somatic stem cells may represent a cell population that is very similar to embryonic stem (ES) cells, it remains unclear whether somatic stem cells retain the potential to differentiate into any cell type derived from the three germ layers. In this study, we investigated the transdifferentiation potential of somatic stem cells using adipose tissue-derived stem/progenitor cells (ASCs; mesodermal stem cells) and pancreatic stem cells (endodermal stem cells). Previous reports from other groups describe the protocol that has been used to differentiate ASCs or mesenchymal stem cells (MSCs) in bone marrow into insulin-producing cells. Induction 1: ASCs were cultured for 3 days in ultra-low attachment plates under serum-free conditions. Induction 2: ASCs were cultured for 24 h with L-DMEM, and reinduced with serum-free H-DMEM for another 10 h. Unlike previous reports, we did not get ASCs to express any pancreas-specific genes, including insulin-1 or insulin-2. Pancreatic stem cells were induced to differentiate into adipo/osteogenic by the following protocols. Induction protocol 1: ACSs were cultured for 7 days with medium containing indometacin, dexamethasone, hydrocortisone, and insulin for adipogenic differentiation. Induction protocol 2: The cells were cultured for 7 days with medium containing dexamethasone, ascorbate-2-phosphate, and β-glycerophosphate for osteogenic differentiation. Although these approaches have been widely used for adipo/osteogenic differentiation from MSCs, adipo/osteogenic differentiation from pancreatic stem cells was not observed. These data suggest that it is not easy for somatic stem cells to transdifferentiate into other germ cell types, at least, under these conditions.

The effect of isolation methods and the use of different enzymes on islet yield and in vivo function

The ability to isolate high-yield pure and viable islets from human cadaver pancreas donors is dependent on donor factor as well as isolation factors. The aim of this study was to examine factors influencing islets recovery and in vivo function with an emphasis on donor and isolation methods as well as to compare the effectiveness of Liberase, widely used in clinical islet isolation, with Serva for the isolation of pure functional islets. The results of 123 islet isolations using Liberase for digestion were compared with those of 113 isolations with Serva. Islet equivalents per gram of tissue were similar between Liberase and Serva (3620 +/- 1858 vs. 4132 +/- 2104, p < 0.2) as well as the percent purity (75 +/- 16 vs. 74 +/- 15, p < 0.9). In vivo function of islets from 71 isolations (Liberase = 45, Serva = 26) were further tested by transplantation into NOD-SCID mice following short-term culture (< 6 days, n = 71). Our data show that both Liberase- and Serva-isolated islets showed similar function results following short-term culture. These data demonstrate that there is no difference in islet yield, purity, and function between the two enzymes. However, when these 71 isolations were analyzed for in vivo function with emphasis on donor factors, cold ischemia time (12.0 +/- 5.3 vs. 15.0 +/- 5.7, p < 0.04), islet integrity (1.6 +/- 0.7 vs. 1.3 +/- 0.5, p < 0.05), and female gender were the only factors that correlated with in vivo function. We also compared the mechanical-shaking method for islets isolation with hand-shaking methods. Our results show that although there is no different in islet yield, purity, and integrity between different enzymes using the same method, hand-shaking method yields more islets with better integrity than mechanical-shaking method.

Inducible nitric oxide synthase-nitric oxide plays an important role in acute and severe hypoxic injury to pancreatic beta cells

BACKGROUND

Islet transplantation is a potential strategy to cure type 1 diabetes mellitus. However, a substantial part of the islet graft becomes nonfunctional due to several factors including hypoxia. However, the precise mechanism of cell damage is largely unknown in hypoxic exposure to pancreatic beta cells. The aim of the present study was to investigate whether acute and severe hypoxic injury could involve inducible nitric oxide synthase (iNOS)-nitric oxide (NO) signaling in beta cells.

METHODS

The rat beta cell line (INS-1) and primary rat islets were incubated in an anoxic chamber. Cell viability was determined by propium iodide staining or cell counting kit. The expression of iNOS mRNA and protein was examined using reverse-transcription polymerase chain reaction and Western blot analysis. NO production was measured as nitrite accumulation by Griess reagent method.

RESULTS

After hypoxic exposure, marked cell death occurred in INS-1 cells and rat islets, accompanied by increase in activated caspase-3 expression. NO production was increased in the culture medium in a time-dependent manner. Increase in expression of iNOS mRNA and protein was found. Pretreatment with a selective iNOS inhibitor, 1400W, significantly prevented cell death during hypoxia. In addition, hypoxia activated c-Jun N-terminal kinase (JNK) significantly, but the addition of 1400W inhibited hypoxia-induced JNK phosphorylation.

CONCLUSIONS

Our data suggest that iNOS-NO plays an important role in acute and severe hypoxic injury to pancreatic beta cells. Therefore, iNOS-NO might be a potential therapeutic target for preserving beta cell survival in islet transplantation through prevention of hypoxia-mediated cell death.

Islet transplantation at the Diabetes Research Institute Japan

Since the Edmonton Protocol was announced, more than 600 patients with type 1 diabetes at more than 50 institutions have received islet transplantation to treat their disease. We recently established a new islet isolation protocol, called the Kyoto Islet Isolation Method, based on the Ricordi method. It includes an in-situ cooling system for pancreas procurement, pancreatic ductal protection, a modified two-layer (M-Kyoto /perfluorochemical [PFC]) method of pancreas preservation, and a new islet purification solution (Iodixanol-based solution). Using this islet isolation method, we isolated islets from 19 human pancreata of non-heart-beating donors and transplanted 16 preparations into seven patients with type 1 diabetes between April 7, 2004 and November 18, 2005. The percentage of those meeting the release criteria of the Edmonton Protocol was more than 80%. We also performed living-donor transplantation of islets for unstable diabetes on January 19, 2005. Establishment of this method enables us to make diabetic patients insulin-independent, using islets not only from two or three pancreata of non-heart-beating donors but also using islets from half a pancreas from a living donor.