Configuration of electrofusion-derived human insulin-secreting cell line as pseudoislets enhances functionality and therapeutic utility

Endothelial Cells Promote Pseudo-islet Function Through BTC-EGFR-JAK/STAT Signaling Pathways

Interactions between cells are of fundamental importance in affecting cell function. In vivo, endothelial cells and islet cells are close to each other, which makes endothelial cells essential for islet cell development and maintenance of islet cell function. We used endothelial cells to construct 3D pseudo-islets, which demonstrated better glucose regulation and greater insulin secretion compared to conventional pseudo-islets in both in vivo and in vitro trials. However, the underlying mechanism of how endothelial cells promote beta cell function localized within islets is still unknown. We performed transcriptomic sequencing, differential gene analysis, and enrichment analysis on two types of pseudo-islets to show that endothelial cells can promote the function of internal beta cells in pseudo-islets through the BTC-EGFR-JAK/STAT signaling pathway. Min6 cells secreted additional BTC after co-culture of endothelial cells with MIN6 cells outside the body. After BTC knockout in vitro, we found that beta cells functioned differently: insulin secretion levels decreased significantly, while the expression of key proteins in the EGFR-mediated JAK/STAT signaling pathway simultaneously decreased, further confirming our results. Through our experiments, we elucidate the molecular mechanisms by which endothelial cells maintain islet function in vitro, which provides a theoretical basis for the construction of pseudo-islets and islet cell transplants for the treatment of diabetes mellitus.

Building Fucoidan/Agarose-Based Hydrogels as a Platform for the Development of Therapeutic Approaches against Diabetes

Current management for diabetes has stimulated the development of versatile 3D-based hydrogels as in vitro platforms for insulin release and as support for the encapsulation of pancreatic cells and islets of Langerhans. This work aimed to create agarose/fucoidan hydrogels to encapsulate pancreatic cells as a potential biomaterial for diabetes therapeutics. The hydrogels were produced by combining fucoidan (Fu) and agarose (Aga), marine polysaccharides derived from the cell wall of brown and red seaweeds, respectively, and a thermal gelation process. The agarose/fucoidan (AgaFu) blended hydrogels were obtained by dissolving Aga in 3 or 5 wt % Fu aqueous solutions to obtain different proportions (4:10; 5:10, and 7:10 wt). The rheological tests on hydrogels revealed a non-Newtonian and viscoelastic behavior, while the characterization confirmed the presence of the two polymers in the structure of the hydrogels. In addition, the mechanical behavior showed that increasing Aga concentrations resulted in hydrogels with higher Young's modulus. Further, the ability of the developed materials to sustain the viability of human pancreatic cells was assessed by encapsulation of the 1.1B4HP cell line for up to 7 days. The biological assessment of the hydrogels revealed that cultured pancreatic beta cells tended to self-organize and form pseudo-islets during the period studied.

Assessing membrane material properties from the response of giant unilamellar vesicles to electric fields

Knowledge of the material properties of membranes is crucial to understanding cell viability and physiology. A number of methods have been developed to probe membranes in vitro, utilizing the response of minimal biomimetic membrane models to an external perturbation. In this review, we focus on techniques employing giant unilamellar vesicles (GUVs), model membrane systems, often referred to as minimal artificial cells because of the potential they offer to mimick certain cellular features. When exposed to electric fields, GUV deformation, dynamic response and poration can be used to deduce properties such as bending rigidity, pore edge tension, membrane capacitance, surface shear viscosity, excess area and membrane stability. We present a succinct overview of these techniques, which require only simple instrumentation, available in many labs, as well as reasonably facile experimental implementation and analysis.

Fucoidan-based hydrogels particles as versatile carriers for diabetes treatment strategies

There is a current lack of fully efficient therapies for diabetes mellitus, a chronic disease where the metabolism of blood glucose is severely hindered by a deficit in insulin or cell resistance to this hormone. Therefore, it is crucial to develop new therapeutic strategies to treat this disease, including devices for the controlled delivery of insulin or encapsulation of insulin-producing cells. In this work, fucoidan (Fu) - a marine sulfated polysaccharide exhibiting relevant properties on reducing blood glucose and antioxidant and anti-inflammatory effects - was used for the development of versatile carriers envisaging diabetes advanced therapies. Fu was functionalized by methacrylation (MFu) using 8% and 12% (v/v) of methacrylic anhydride and further photocrosslinked using visible light in the presence of triethanolamine and eosin-y to produce hydrogel particles. Degree of methacrylation varied between 2.78 and 6.50, as determined by ¹HNMR, and the produced particles have an average diameter ranging from 0.63 to 1.3 mm (dry state). Insulin (5%) was added to MFu solution to produce drug-loaded particles and the release profile was assessed in phosphate buffer solution (PBS) and simulated intestinal fluid (SIF) for 24 h. Insulin was released in a sustained manner during the initial 8 h, reaching then a plateau, higher in PBS than in SIF, indicating that lower pH favors drug liberation. Moreover, the ability of MFu particles to serve as templates for the culture of human pancreatic cells was assessed using 1.1B4 cell line during up to 7 days. During the culture period studied, pancreatic beta cells were proliferating, with a global viability over 80% and tend to form pseudo-islets, thus suggesting that the proposed biomaterial could be a good candidate as versatile carrier for diabetes treatment as they sustain the release of insulin and support pancreatic beta cells viability.

Pseudoislet Aggregation of Pancreatic β-Cells Improves Glucose Stimulated Insulin Secretion by Altering Glucose Metabolism and Increasing ATP Production

Appropriate glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells is an essential component of blood glucose homeostasis. Configuration of β-cells as 3D pseudoislets (PI) improves the GSIS response compared to 2D monolayer (ML) culture. The aim of this study was to determine the underlying mechanisms. MIN6 β-cells were grown as ML or PI for 5 days. Human islets were isolated from patients without diabetes. Function was assessed by GSIS and metabolic capacity using the Seahorse bioanalyser. Connexin 36 was downregulated using inducible shRNA. Culturing MIN6 as PI improved GSIS. MIN6 PI showed higher glucose-stimulated oxygen consumption (OCR) and extracellular acidification (ECAR) rates. Further analysis showed the higher ECAR was, at least in part, a consequence of increased glycolysis. Intact human islets also showed glucose-stimulated increases in both OCR and ECAR rates, although the latter was smaller in magnitude compared to MIN6 PI. The higher rates of glucose-stimulated ATP production in MIN6 PI were consistent with increased enzyme activity of key glycolytic and TCA cycle enzymes. There was no impact of connexin 36 knockdown on GSIS or ATP production. Configuration of β-cells as PI improves GSIS by increasing the metabolic capacity of the cells, allowing higher ATP production in response to glucose.

In Vitro Disease Models of the Endocrine Pancreas

The ethical constraints and shortcomings of animal models, combined with the demand to study disease pathogenesis under controlled conditions, are giving rise to a new field at the interface of tissue engineering and pathophysiology, which focuses on the development of in vitro models of disease. In vitro models are defined as synthetic experimental systems that contain living human cells and mimic tissue- and organ-level physiology in vitro by taking advantage of recent advances in tissue engineering and microfabrication. This review provides an overview of in vitro models and focuses specifically on in vitro disease models of the endocrine pancreas and diabetes. First, we briefly review the anatomy, physiology, and pathophysiology of the human pancreas, with an emphasis on islets of Langerhans and beta cell dysfunction. We then discuss different types of in vitro models and fundamental elements that should be considered when developing an in vitro disease model. Finally, we review the current state and breakthroughs in the field of pancreatic in vitro models and conclude with some challenges that need to be addressed in the future development of in vitro models.

Cellulose-based scaffolds enhance pseudoislets formation and functionality

In vitroresearch for the study of type 2 diabetes (T2D) is frequently limited by the availability of a functional model for islets of Langerhans. To overcome the limitations of obtaining pancreatic islets from different sources, such as animal models or human donors, immortalized cell lines as the insulin-producing INS1Eβ-cells have appeared as a valid alternative to model insulin-related diseases. However, immortalized cell lines are mainly used in flat surfaces or monolayer distributions, not resembling the spheroid-like architecture of the pancreatic islets. To generate islet-like structures, the use of scaffolds appeared as a valid tool to promote cell aggregations. Traditionally-used hydrogel encapsulation methods do not accomplish all the requisites for pancreatic tissue engineering, as its poor nutrient and oxygen diffusion induces cell death. Here, we use cryogelation technology to develop a more resemblance scaffold with the mechanical and physical properties needed to engineer pancreatic tissue. This study shows that carboxymethyl cellulose (CMC) cryogels prompted cells to generateβ-cell clusters in comparison to gelatin-based scaffolds, that did not induce this cell organization. Moreover, the high porosity achieved with CMC cryogels allowed us to create specific range pseudoislets. Pseudoislets formed within CMC-scaffolds showed cell viability for up to 7 d and a better response to glucose over conventional monolayer cultures. Overall, our results demonstrate that CMC-scaffolds can be used to control the organization and function of insulin-producingβ-cells, representing a suitable technique to generateβ-cell clusters to study pancreatic islet function.

Development of Donor Recipient Chimeric Cells of bone marrow origin as a novel approach for tolerance induction in transplantation

Background

Cell therapies and chimerism-based strategies are currently the most successful approach for tolerance induction in transplantation. This study aimed to establish and characterize novel Donor Recipient Chimeric Ccell (DRCC) therapy of bone marrow (BM) origin presenting donor-recipient phenotype to support tolerance induction.

Methods

Ex vivo fusions of fully MHC-mismatched BM cells from ACI (RT1^a) and Lewis (RT1^l) rats were performed using polyethylene-glycol (PEG). The creation of rat DRCC was tested by flow cytometry (FC), confocal microscopy and PCR. FC characterized DRCC's phenotype (CD3, CD4, CD8, CD45, CD90, CD11b/c, CD45RA, OX-82, or CD4/CD25) and apoptosis, while mixed lymphocyte reaction assessed DRCC's immunogenicity and colony forming unit assay tested DRCC's differentiation and proliferation. DRCC's polyploidy was evaluated using Hoechst33342 staining and COMET assay tested genotoxicity of fusion procedure. ELISA analyzed the secretion of IL-2, IL-4, IL-10, TGFß1, IFNγ and TNFα by DRCC at day 1, 5 and 14 post-fusion. The DRCC's phenotype after long-term culturing was assessed by reverse-transcription PCR.

Results

The chimeric state of DRCC was confirmed. Fusion did not change the expression of hematopoietic markers compared to BM controls. Although an increased number of early and late apoptotic (Annexin V⁺/Sytox blue^- and Annexin V⁺/Sytox blue⁺, respectively) DRCC was detected at 24h post-fusion, the number significantly decreased at day 5 (38.4%±3.1% and 22.6%±2.5%, vs. 28.3%±2.5% and 13.9%±2.6%, respectively, P<0.05). DRCC presented decreased immunogenicity, increased expression of IL-10 and TGFβ1 and proliferative potential comparable to BM controls. The average percentage of tetraploid DRCC was 3.1%±0.2% compared to 0.96%±0.1% in BM controls. The lack of damage to the DRCC's DNA content supported the DRCC's safety. In culture, DRCC maintained proliferation for up to 28 days while preserving hematopoietic profile.

Conclusions

This study confirmed feasibility of DRCC creation via ex vivo PEG mediated fusion. The created DRCC revealed pro-tolerogenic properties indicating potential immunomodulatory effect of DRCC therapy when applied in vivo to support tolerance induction in solid organ and vascularized composite allograft transplantation.

Islet-on-a-chip: Biomimetic micropillar-based microfluidic system for three-dimensional pancreatic islet cell culture

Type 2 diabetes is currently one of the most common metabolic diseases, affecting all ages worldwide. As the incidence of type 2 diabetes increases, a growing number of studies focus on islets of Langerhans. A three-dimensional research model that maps islet morphology and maintains hormonal balance in vivo is still needed. In this work, we present an Islet-on-a-chip system, specifically a micropillar-based microfluidic platform for three-dimensional pancreatic islet cell culture and analysis. The microfluidic system consisted of two culture chambers that were equipped with 15 circular microtraps each, which were built with seven round micropillars each. Micropillars in the structure of microtraps supported cell aggregation by limiting the growth surface and minimizing wall shear stress, thereby ensuring proper medium diffusion and optimal culture conditions for cell aggregates. Our system is compatible with microwell plate readers and confocal laser scanning microscopes. Because of optimization of the immunostaining method, the appropriate cell distribution and high viability and proliferation up to 72 h of culture were confirmed. Enzyme-linked immunosorbent assays were performed to measure insulin and glucagon secretion after stimulation with different glucose concentrations. To our knowledge, this is the first Lab-on-a-chip system which enables the formation and three-dimensional culture of cell aggregates composed of commercially available α and β pancreatic islet cells. The specific composition and arrangement of cells in the obtained model corresponds to the arrangement of the cells in rodent pancreatic islets in vivo. This Islet-on-a-chip system may be utilized to test pathogenic effectors and future therapeutic agents.

Tissue-engineered islet-like cell clusters generated from adipose tissue-derived stem cells on three-dimensional electrospun scaffolds can reverse diabetes in an experimental rat model and the role of porosity of scaffolds on cluster differentiation

In the current study, three-dimensional (3D) nanofibrous scaffolds with pore sizes in the range of 24-250 μm and 24-190 μm were fabricated via a two-step electrospinning method to overcome the limitation of obtaining three-dimensionality with large pore sizes for islet culture using conventional electrospinning. The scaffolds supported the growth and differentiation of adipose-derived mesenchymal stem cells to islet-like clusters (ILCs). The pore size of the scaffolds was found to influence the cluster size, viability and insulin release of the differentiated islets. Hence, islet clusters of the desired size could be developed for transplantation to overcome the loss of bigger islets due to hypoxia which adversely impacts the outcome of transplantation. The tissue-engineered constructs with ILC diameter of 50 μm reduced glycemic value within 3-4 weeks after implantation in the omental pouch of diabetic rats. Detection of insulin in the serum of implanted rats demonstrates that the tissue-engineered construct is efficient to control hyperglycemia. Our findings prove that the 3D architecture and pore size of scaffolds regulates the morphology and size of islets during differentiation which is critical in the survival and function of ILCs in vitro and in vivo.

Impaired EIF2S3 function associated with a novel phenotype of X-linked hypopituitarism with glucose dysregulation

Background

The heterotrimeric GTP-binding protein eIF2 forms a ternary complex with initiator methionyl-tRNA and recruits it to the 40S ribosomal subunit for start codon selection and thereby initiates protein synthesis. Mutations in EIF2S3, encoding the eIF2γ subunit, are associated with severe intellectual disability and microcephaly, usually as part of MEHMO syndrome.

Methods

Exome sequencing of the X chromosome was performed on three related males with normal head circumferences and mild learning difficulties, hypopituitarism (GH and TSH deficiencies), and an unusual form of glucose dysregulation. In situ hybridisation on human embryonic tissue, EIF2S3-knockdown studies in a human pancreatic cell line, and yeast assays on the mutated corresponding eIF2γ protein, were performed in this study.

Findings

We report a novel hemizygous EIF2S3 variant, p.Pro432Ser, in the three boys (heterozygous in their mothers). EIF2S3 expression was detectable in the developing pituitary gland and pancreatic islets of Langerhans. Cells lacking EIF2S3 had increased caspase activity/cell death. Impaired protein synthesis and relaxed start codon selection stringency was observed in mutated yeast.

Interpretation

Our data suggest that the p.Pro432Ser mutation impairs eIF2γ function leading to a relatively mild novel phenotype compared with previous EIF2S3 mutations. Our studies support a critical role for EIF2S3 in human hypothalamo-pituitary development and function, and glucose regulation, expanding the range of phenotypes associated with EIF2S3 mutations beyond classical MEHMO syndrome. Untreated hypoglycaemia in previous cases may have contributed to their more severe neurological impairment and seizures in association with impaired EIF2S3.

Fund

GOSH, MRF, BRC, MRC/Wellcome Trust and NIGMS funded this study.

Inhibition of SNAT5 Induces Incretin-Responsive State From Incretin-Unresponsive State in Pancreatic β-Cells: Study of β-Cell Spheroid Clusters as a Model

β-Cell-β-cell interactions are required for normal regulation of insulin secretion. We previously found that formation of spheroid clusters (called K20-SC) from MIN6-K20 clonal β-cells lacking incretin-induced insulin secretion (IIIS) under monolayer culture (called K20-MC) drastically induced incretin responsiveness. Here we investigated the mechanism by which an incretin-unresponsive state transforms to an incretin-responsive state using K20-SC as a model. Glutamate production by glucose through the malate-aspartate shuttle and cAMP signaling, both of which are critical for IIIS, were enhanced in K20-SC. SC formed from β-cells deficient for aspartate aminotransferase 1, a critical enzyme in the malate-aspartate shuttle, exhibited reduced IIIS. Expression of the sodium-coupled neutral amino acid transporter 5 (SNAT5), which is involved in glutamine transport, was downregulated in K20-SC and pancreatic islets of normal mice but was upregulated in K20-MC and islets of rodent models of obesity and diabetes, both of which exhibit impaired IIIS. Inhibition of SNAT5 significantly increased cellular glutamate content and improved IIIS in islets of these models and in K20-MC. These results suggest that suppression of SNAT5 activity, which results in increased glutamate production, and enhancement of cAMP signaling endows incretin-unresponsive β-cells with incretin responsiveness.

Bioengineered human pseudoislets form efficiently from donated tissue, compare favourably with native islets in vitro and restore normoglycaemia in mice

AIMS/HYPOTHESIS

Islet transplantation is a treatment option that can help individuals with type 1 diabetes become insulin independent, but inefficient oxygen and nutrient delivery can hamper islet survival and engraftment due to the size of the islets and loss of the native microvasculature. We hypothesised that size-controlled pseudoislets engineered via centrifugal-forced-aggregation (CFA-PI) in a platform we previously developed would compare favourably with native islets, even after taking into account cell loss during the process.

METHODS

Human islets were dissociated and reaggregated into uniform, size-controlled CFA-PI in our microwell system. Their performance was assessed in vitro and in vivo over a range of sizes, and compared with that of unmodified native islets, as well as islet cell clusters formed by a conventional spontaneous aggregation approach (in which dissociated islet cells are cultured on ultra-low-attachment plates). In vitro studies included assays for membrane integrity, apoptosis, glucose-stimulated insulin secretion assay and total DNA content. In vivo efficacy was determined by transplantation under the kidney capsule of streptozotocin-treated Rag1-/- mice, with non-fasting blood glucose monitoring three times per week and IPGTT at day 60 for glucose response. A recovery nephrectomy, removing the graft, was conducted to confirm efficacy after completing the IPGTT. Architecture and composition were analysed by histological assessment via insulin, glucagon, pancreatic polypeptide, somatostatin, CD31 and von Willebrand factor staining.

RESULTS

CFA-PI exhibit markedly increased uniformity over native islets, as well as substantially improved glucose-stimulated insulin secretion (8.8-fold to 11.1-fold, even after taking cell loss into account) and hypoxia tolerance. In vivo, CFA-PI function similarly to (and potentially better than) native islets in reversing hyperglycaemia (55.6% for CFA-PI vs 20.0% for native islets at 500 islet equivalents [IEQ], and 77.8% for CFA-PI vs 55.6% for native islets at 1000 IEQ), and significantly better than spontaneously aggregated control cells (55.6% for CFA-PI vs 0% for spontaneous aggregation at 500 IEQ, and 77.8% CFA-PI vs 33.4% for spontaneous aggregation at 1000 IEQ; p < 0.05). Glucose clearance in the CFA-PI groups was improved over that in the native islet groups (CFA-PI 18.1 mmol/l vs native islets 29.7 mmol/l at 60 min; p < 0.05) to the point where they were comparable with the non-transplanted naive normoglycaemic control mice at a low IEQ of 500 IEQ (17.2 mmol/l at 60 min).

CONCLUSIONS/INTERPRETATION

The ability to efficiently reformat dissociated islet cells into engineered pseudoislets with improved properties has high potential for both research and therapeutic applications.

Cellular models for beta-cell function and diabetes gene therapy

Diabetes is characterized by the destruction and/or relative dysfunction of insulin-secreting beta-cells in the pancreatic islets of Langerhans. Consequently, considerable effort has been made to understand the physiological processes governing insulin production and secretion in these cells and to elucidate the mechanisms involved in their deterioration in the pathogenesis of diabetes. To date, considerable research has exploited clonal beta-cell lines derived from rodent insulinomas. Such cell lines have proven to be a great asset in diabetes research, in vitro drug testing, and studies of beta-cell physiology and provide a sustainable, and in many cases, more practical alternative to the use of animals or primary tissue. However, selection of the most appropriate rodent beta cell line is often challenging and no single cell line entirely recapitulates the properties of human beta-cells. The generation of stable human beta-cell lines would provide a much more suitable model for studies of human beta-cell physiology and pathology and could potentially be used as a readily available source of implantable insulin-releasing tissue for cell-based therapies of diabetes. In this review, we discuss the history, development, functional characteristics and use of available clonal rodent beta-cell lines, as well as reflecting on recent advances in the generation of human-derived beta-cell lines, their use in research studies and their potential for cell therapy of diabetes.

Microphysiological Analysis Platform of Pancreatic Islet β-Cell Spheroids

The hallmarks of diabetics are insufficient secretion of insulin and dysregulation of glucagon. It is critical to understand release mechanisms of insulin, glucagon, and other hormones from the islets of Langerhans. In spite of remarkable advancements in diabetes research and practice, robust and reproducible models that can measure pancreatic β-cell function are lacking. Here, a microphysiological analysis platform (MAP) that allows the uniform 3D spheroid formation of pancreatic β-cell islets, large-scale morphological phenotyping, and gene expression mapping of chronic glycemia and lipidemia development is reported. The MAP enables the scaffold-free formation of densely packed β-cell spheroids (i.e., multiple array of 110 bioreactors) surrounded with a perfusion flow network inspired by physiologically relevant microenvironment. The MAP permits dynamic perturbations on the β-cell spheroids and the precise controls of glycemia and lipidemia, which allow us to confirm that cellular apoptosis in the β-cell spheroid under hyperglycemia and hyperlipidemia is mostly dependent to a reactive oxygen species-induced caspase-mediated pathway. The β-cells' MAP might provide a potential new map in the pathophysiological mechanisms of β cells.

Mimicking Neuroligin-2 Functions in β-Cells by Functionalized Nanoparticles as a Novel Approach for Antidiabetic Therapy

Both pancreatic β-cell membranes and presynaptic active zones of neurons include in their structures similar protein complexes, which are responsible for mediating the secretion of bioactive molecules. In addition, these membrane-anchored proteins regulate interactions between neurons and guide the formation and maturation of synapses. These proteins include the neuroligins (e.g., NL-2) and their binding partners, the neurexins. The insulin secretion and maturation of β-cells is known to depend on their 3-dimensional (3D) arrangement. It was also reported that both insulin secretion and the proliferation rates of β-cells increase when cells are cocultured with clusters of NL-2. Use of full-length NL-2 or even its exocellular domain as potential β-cell functional enhancers is limited by the biostability and bioavailability issues common to all protein-based therapeutics. Thus, based on molecular modeling approaches, a short peptide with the potential ability to bind neurexins was derived from the NL-2 sequence. Here, we show that the NL-2-derived peptide conjugates onto innovative functional maghemite (γ-Fe2O3)-based nanoscale composite particles enhance β-cell functions in terms of glucose-stimulated insulin secretion and protect them under stress conditions. Recruiting the β-cells' "neuron-like" secretory machinery as a target for diabetes treatment use has never been reported before. Such nanoscale composites might therefore provide a unique starting point for designing a novel class of antidiabetic therapeutic agents that possess a unique mechanism of action.

Molecular Mechanisms of Toxicity and Cell Damage by Chemicals in a Human Pancreatic Beta Cell Line, 1.1B4

OBJECTIVES

Mechanisms of toxicity and cell damage were investigated in novel clonal human pancreatic beta cell line, 1.1B4, after exposure to streptozotocin, alloxan, ninhydrin, and hydrogen peroxide.

METHODS

Viability, DNA damage, insulin secretion/content, [Ca]i, and glucokinase/hexokinase, mRNA expression were measured by MTT assay, comet assay, radioimmunoassay, fluorometric imaging plate reader, enzyme-coupled photometry, and real-time polymerase chain reaction, respectively.

RESULTS

Chemicals significantly reduced 1.1B4 cell viability in a time/concentration-dependent manner. Chronic 18-hour exposure decreased cellular insulin, glucokinase, and hexokinase activities. Chemicals decreased transcription of INS, GCK, PCSK1, PCSK2, and GJA1 (involved in secretory function). Insulin release and [Ca]i responses to nutrients and membrane-depolarizing agents were impaired. Streptozotocin and alloxan up-regulated transcription of genes, SOD1 and SOD2 (antioxidant enzymes). Ninhydrin and hydrogen peroxide up-regulated SOD2 transcription, whereas alloxan and hydrogen peroxide increased CAT transcription. Chemicals induced DNA damage, apoptosis, and increased caspase 3/7 activity. Streptozotocin and alloxan decreased transcription of BCL2 while increasing transcription of BAX. Chemicals did not affect transcription of HSPA4 and HSPA5 and nitrite production.

CONCLUSIONS

1.1B4 cells represent a useful model of human beta cells. Chemicals impaired 1.1B4 cell secretory function and activated antioxidant defense and apoptotic pathways without activating endoplasmic reticulum stress response/nitrosative stress.

Mass production of functional human pancreatic β-cells: why and how?

Diabetes (either type 1 or type 2) is due to insufficient functional β-cell mass. Research has, therefore, aimed to discover new ways to maintain or increase either β-cell mass or function. For this purpose, rodents have mainly been used as model systems and a large number of discoveries have been made. Meanwhile, although we have learned that rodent models represent powerful systems to model β-cell development, function and destruction, we realize that there are limitations when attempting to transfer the data to what is occurring in humans. Indeed, while human β-cells share many similarities with rodent β-cells, they also differ on a number of important parameters. In this context, developing ways to study human β-cell development, function and death represents an important challenge. This review will describe recent data on the development and use of convenient sources of human β-cells that should be useful tools to discover new ways to modulate functional β-cell mass in humans.

Aggregation of Engineered Human β-Cells Into Pseudoislets: Insulin Secretion and Gene Expression Profile in Normoxic and Hypoxic Milieu

Innovative treatments to cure type 1 diabetes are being actively researched. Among the different strategies, the replacement of β-cells has given promising results. Classically, islets from cadaveric donors are transplanted into diabetic patients, but recently phase I clinical trials that use stem cell-derived β-cells have been started. Such protocols require either an immunosuppressive treatment or the macroencapsulation of the β-cells. They involve cell aggregation and the exposure of the cells to hypoxia. Using an engineered human β-cell, we have addressed these two problems: a novel human β-cell line called EndoC-βH3 was cultured as single cells or aggregated clusters. EndoC-βH3 cells were also cultured at normal atmospheric oxygen tension (pO₂ = 21%) or hypoxia (pO₂ = 3%) in the presence or absence of modulators of the hypoxia-inducible factor 1α (HIF1α) pathway. Cell aggregation improved glucose-stimulated insulin secretion, demonstrating the benefit of cell-cell contacts. Low oxygen tension decreased β-cell viability and their sensitivity to glucose, but did not alter insulin production nor the insulin secretion capacity of the remaining cells. To investigate the role of HIF1α, we first used a HIF stabilizer at pO₂ = 21%. This led to a mild decrease in cell viability, impaired glucose sensitivity, and altered insulin secretion. Finally, we used a HIF inhibitor on EndoC-βH3 pseudoislets exposed to hypoxia. Such treatment considerably decreased cell viability. In conclusion, aggregation of the EndoC-βH3 cells seems to be important to improve their function. A fraction of the EndoC-βH3 cells are resistant to hypoxia, depending on the level of activity of HIF1α. Thus, these cells represent a good human cell model for future investigations on islet cell transplantation analysis.

Engineering of microscale three-dimensional pancreatic islet models in vitro and their biomedical applications

Diabetes now is the most common chronic disease in the world inducing heavy burden for the people's health. Based on this, diabetes research such as islet function has become a hot topic in medical institutes of the world. Today, in medical institutes, the conventional experiment platform in vitro is monolayer cell culture. However, with the development of micro- and nano-technologies, several microengineering methods have been developed to fabricate three-dimensional (3D) islet models in vitro which can better mimic the islet of pancreases in vivo. These in vitro islet models have shown better cell function than monolayer cells, indicating their great potential as better experimental platforms to elucidate islet behaviors under both physiological and pathological conditions, such as the molecular mechanisms of diabetes and clinical islet transplantation. In this review, we present the state-of-the-art advances in the microengineering methods for fabricating microscale islet models in vitro. We hope this will help researchers to better understand the progress in the engineering 3D islet models and their biomedical applications such as drug screening and islet transplantation.

Modified Adherence Method (MAM) for Electrofusion of Anchorage-Dependent Cells

The artificially induced cell fusion is a useful experimental tool in biology, biotechnology and medicine. The electrofusion is a physical method for cell fusion that applies high-voltage electric pulses. The use of electric pulses causes cell membrane structural changes which bring the cell membrane in the so-called fusogenic state. When such fusogenic membranes are in close contact cell fusion takes place. Physical contact between fusion partners can be achieved by various methods and one of them is modified adherence method (MAM) described in detail here on B16-F1 cell line. The method is based on the fact that living cells form contacts in confluent culture. However, instead of using confluent cell culture, in modified adherence method cells are plated in suitable concentration and allowed to form contacts for only short predetermined period of time. During that time the cells are only slightly attached to the dish surface maintaining the spherical shape. Observed high fusion yields up to 50 % obtained by MAM in situ by dual-color fluorescence microscopy are among the highest in field of electrofusion. The method can be readily adapted to other anchorage-dependent cell lines.

Involvement of RhoA/ROCK in insulin secretion of pancreatic β-cells in 3D culture

Cell-cell contacts and interactions between pancreatic β-cells and/or other cell populations within islets are essential for cell survival, insulin secretion, and functional synchronization. Three-dimensional (3D) culture systems supply the ideal microenvironment for islet-like cluster formation and functional maintenance. However, the underlying mechanisms remain unclear. In this study, mouse insulinoma 6 (MIN6) cells were cultured in a rotating 3D culture system to form islet-like aggregates. Glucose-stimulated insulin secretion (GSIS) and the RhoA/ROCK pathway were investigated. In the 3D-cultured MIN6 cells, more endocrine-specific genes were up-regulated, and GSIS was increased to a greater extent than in cells grown in monolayers. RhoA/ROCK inactivation led to F-actin remodeling in the MIN6 cell aggregates and greater insulin exocytosis. The gap junction protein, connexin 36 (Cx36), was up-regulated in MIN6 cell aggregates and RhoA/ROCK-inactivated monolayer cells. GSIS dramatically decreased when Cx36 was knocked down by short interfering RNA and could not be reversed by RhoA/ROCK inactivation. Thus, the RhoA/ROCK signaling pathway is involved in insulin release through the up-regulation of Cx36 expression in 3D-cultured MIN6 cells.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

miR-25 and miR-92a regulate insulin I biosynthesis in rats

The 3' UTR of insulin has been identified as a critical region that confers mRNA stability, which is crucial for promoting transcription in response to glucose challenge. miRNAs are endogenously encoded non-coding RNAs that function as regulators of gene expression. This regulatory function is generally mediated by complementary binding to the 3'UTR of its mRNA targets that affects subsequent translational process. Genes involved in the regulation of glucose homeostasis, particularly in insulin production, have been found as targets of several miRNAs. Yet, no direct miRNA-based regulators of insulin biosynthesis have been identified. In this study, identification of possible miRNA-based regulators of insulin production is explored. Members of a miRNA family, miR-25 and miR-92a, are found as direct modulators of insulin expression. Overexpression of miR-25 or miR-92a reduced insulin expression while inhibition of miR-25 and miR-92a expression using corresponding antagomiRs promoted insulin expression and ultimately enhanced glucose-induced insulin secretion. Furthermore, suppression of insulin secretion by pre miR-9 could be attenuated by treatment with anti-miR-25 or miR-92a. Interestingly, we found the binding site of miR-25 and miR-92a to overlap with that of PTBP1, an important RNA binding molecule that stabilizes insulin mRNA for translation. Despite the increase in PTBP1 protein in the pancreas of diabetic rats, we observed insulin expression to be reduced alongside upregulation of miR-25 and miR-92a, suggesting an intricate regulation of insulin (bio)synthesis at its mRNA level.

Topographical arrangement of α- and β-cells within neo-islet tissues engineered by islet cell sheet transplantation in mice

BACKGROUND

We established a procedure to engineer therapeutic neo-islets in subcutaneous spaces in mice by transplanting contiguous layers of islet cell sheets. In this study, we investigated the cellular arrangements of α and β within these engineered neo-islets in vivo as a function of time after sheet transplantation.

METHODS AND RESULTS

Temperature-responsive culture dishes optimized for dispersed islet cell culture were prepared by covalently immobilizing a temperature-responsive polymer poly(N-isopropylacrylamide) (PIPAAm) on plastic dishes followed by laminin-5 coating. Dispersed islet cells obtained from Lewis rats were plated onto the PIPAAm dishes. After reaching confluence at day 2, islet cells were harvested as uniformly spread islet cell sheets by lowering the culture temperature from 37°C to 20°C for 20 minutes. Islet sheet transplantation was performed to creat neo-islet tissues in the subcutaneous spaces of SCID mice with streptozotocin-induced diabetes. This neo-islet engineering approach successfully lowered mouse blood glucose levels, achieving euglycemia at day 5 and thereafter. Histologic analyses of samples obtained at day 4 revealed that neo-islet tissues in the subcutaneous spaces showed heterogeneous cellular alignment of α and β cells. In contrast, analyses of samples at days 14 and 60 revealed α and β cells predominantly located at the peripheral and central parts of the engineered tissues, respectively.

CONCLUSIONS

Reassembly of α and β cells occurred in neo-islet tissues engineered by sheet transplantation. The unique cellular arrangements in neo-islet tissues, which were similar to those in naïve pancreatic islets, may contribute to their longevity and long-term function.

Mechanisms of toxicity by proinflammatory cytokines in a novel human pancreatic beta cell line, 1.1B4

BACKGROUND

Molecular mechanisms of toxicity and cell damage were investigated in the novel human beta cell line, 1.1B4, after exposure to proinflammatory cytokines - IL-1β, IFN-γ, TNF-α.

METHODS

MTT assay, insulin radioimmunoassay, glucokinase assay, real time reverse transcription PCR, western blotting, nitrite assay, caspase assay and comet assay were used to investigate mechanisms of cytokine toxicity.

RESULTS

Viability of 1.1B4 cells decreased after 18h cytokine exposure. Cytokines significantly reduced cellular insulin content and impaired insulin secretion induced by glucose, alanine, KCl, elevated Ca(2+), GLP-1 or forskolin. Glucokinase enzyme activity, regulation of intracellular Ca(2+) and PDX1 protein expression were significantly reduced by cytokines. mRNA expression of genes involved in secretory function - INS, GCK, PCSK2 and GJA1 was downregulated in cytokine treated 1.1B4 cells. Upregulation of transcription of genes involved in antioxidant defence - SOD2 and GPX1 was observed, suggesting involvement of oxidative stress. Cytokines also upregulated transcriptions of NFKB1 and STAT1, which was accompanied by a significant increase in NOS2 transcription and accumulation of nitrite in culture medium, implicating nitrosative stress. Oxidative and nitrosative stresses induced apoptosis was evident from increased % tail DNA, DNA fragmentation, caspase 3/7 activity, apoptotic cells and lower BCL2 protein expression.

CONCLUSIONS

This study delineates molecular mechanisms of cytokine toxicity in 1.1B4 cells, which agree with earlier observations using human islets and rodent beta cells.

GENERAL SIGNIFICANCE

This study emphasizes the potential usefulness of this cell line as a human beta cell model for research investigating autoimmune destruction of pancreatic beta cells.

In vitro formation of β cell pseudoislets using islet-derived endothelial cells

β cell pseudoislets (PIs) are used for the in vitro study of β-cells in a three-dimensional (3-D) configuration. Current methods of PI induction require unique culture conditions and extensive mechanical manipulations. Here we report a novel co-culture system consisting of high passage β-cells and islet-derived endothelial cells (iECs) that results in a rapid and spontaneous formation of free-floating PIs. PI structures were formed as early as 72 h following co-culture setup and were preserved for more than 14 d. These PIs, composed solely of β-cells, were similar in size to that of native islets and showed an increased percentage of proinsulin-positive cells, increased insulin gene expression in response to glucose stimulation, and restored glucose-stimulated insulin secretion when compared to β-cells cultured as monolayers. Key extracellular matrix proteins that were absent in β-cells cultured alone were deposited by iECs on PIs and were found in and around the PIs. iEC-induced PIs are a readily available tool for examining β cell function in a native 3-D configuration and can be used for examining β-cell/iEC interactions in vitro.

Immune-mediated β-cell death in type 1 diabetes: lessons from human β-cell lines

Type 1 diabetes (T1D) is a chronic, multifactorial disorder that results from a contretemps of genetic and environmental factors. Autoimmune attack and functional inhibition of the insulin-producing β cells in the pancreas lead to the inability of β cells to metabolize glucose, and thus results the hallmark clinical symptom of diabetes: abnormally high blood glucose levels. Treatment and protection from T1D require a detailed knowledge of the molecular effectors and the mechanism(s) of cell death leading to β-cell demise. Primary islets and surrogate β cells have been utilized in vitro to investigate in isolation-specific mechanisms associated with progression to T1D in vivo. This review focuses on the data obtained from these experiments. Studies using transformed β cells of human sources are described.