Identification and removal of unexpected proliferative off-target cells emerging after iPSC-derived pancreatic islet cell implantation.

Differentiation of pancreatic endocrine cells from human pluripotent stem cells (PSCs) has been thoroughly investigated for application in cell therapy against diabetes. In the context of induced pancreatic endocrine cell implantation, previous studies have reported graft enlargement resulting from off-target pancreatic lineage cells. However, there is currently no documented evidence of proliferative off-target cells beyond the pancreatic lineage in existing studies. Here, we show that the implantation of seven-stage induced PSC-derived pancreatic islet cells (s7-iPICs) leads to the emergence of unexpected off-target cells with proliferative capacity via in vivo maturation. These cells display characteristics of both mesenchymal stem cells (MSCs) and smooth muscle cells (SMCs), termed proliferative MSC- and SMC-like cells (PMSCs). The frequency of PMSC emergence was found to be high when 108 s7-iPICs were used. Given that clinical applications involve the use of a greater number of induced cells than 108, it is challenging to ensure the safety of clinical applications unless PMSCs are adequately addressed. Accordingly, we developed a detection system and removal methods for PMSCs. To detect PMSCs without implantation, we implemented a 4-wk-extended culture system and demonstrated that putative PMSCs could be reduced by compound treatment, particularly with the taxane docetaxel. When docetaxel-treated s7-iPICs were implanted, the PMSCs were no longer observed. This study provides useful insights into the identification and resolution of safety issues, which are particularly important in the field of cell-based medicine using PSCs.

The potential antioxidant effect of N-acetylcysteine on X-ray ionizing radiation-induced pancreas islet cell toxicity.

PURPOSE: Previous research has highlighted the impact of X-ray irradiation-induced organ damage, on cancer patients after radiation therapy. The ionizing radiation-induced oxidative stress causes injury to the pancreatic islet cells of Langerhans. We used histopathological, immunohistochemical, and biochemical analyses to examine α- and ß-cells in the islets of Langerhans in rats undergoing whole-body x-ray ionizing radiation, a group of which was treated with NAC. MATERIAL AND METHODS: Twenty-four male rats were randomly divided into 3 groups, one control, and two experimental groups. Group I (Control) was administered only saline solution (0.09% NaCl) by oral gavage for 7 days. Group II (IR) was administrated whole body single dose 6 Gray ionizing radiation (IR) and saline solution (0.09% NaCl) by oral gavage for 7 days. Group III (IR + NAC) was administered 300 mg/kg NAC (N-acetylcysteine) by oral gavage for 7 days, 5 days before, and 2 days after 6 Gray IR application. RESULTS: In the X-ray irradiation group, we observed diffuse necrotic endocrine cells in the islets of Langerhans. In addition, we found that Caspase-3, malondialdehyde (MDA) levels increased, and insulin, glucagon, and glutathione (GSH) levels decreased in the IR group compared to the control group. In contrast, we observed a decrease in Caspase-3, and MDA levels in necrotic endocrine cells, and an increase in insulin, glucagon, and GSH levels in the IR + NAC group compared to the IR group. CONCLUSION: This study provides evidence for the beneficial effects of N-acetyl cysteine on islets of Langerhans cells with X-ray ionizing-radiation-induced damage in a rat model.

Single-cell RNA sequencing highlights the roles of C1QB and NKG7 in the pancreatic islet immune microenvironment in type 1 diabetes mellitus.

Single-cell RNA sequencing (scRNA-seq) technology is a powerful tool for characterizing individual cells and elucidating biological mechanisms at the cellular level. Using this technology, this study focuses on the mechanism of C1QB and NKG7 in pancreatic islet immune microenvironment in type 1 diabetes mellitus (T1DM). T1DM-related scRNA-seq data were downloaded from GEO database, followed by batch effect removal, cluster analysis, cell annotation and enrichment analysis. Thereafter, T1DM-related Bulk RNA-seq data were downloaded from GEO database. The infiltrating immune cell abundance was estimated and its correlation with the expression of immune cell marker genes was determined. Functional assays were performed in a constructed rat model of T1DM and cultured monocytes and lymphocytes for further validation. A large number of highly variable genes were found in pancreatic islet samples in T1DM. T1DM islet-derived cells may consist of 14 cell types. Macrophages and T lymphocytes were the major cells in pancreatic islet immune microenvironment. C1QB and NKG7 may be the key genes affecting macrophages and T lymphocytes, respectively. Silencing C1QB inhibited the differentiation of monocytes into macrophages and reduced the number of macrophages. Silencing NKG7 prevented T lymphocyte activation and proliferation. In vivo data confirmed that silencing C1QB and NKG7 reduced the number of macrophages and T lymphocytes in the pancreatic islet of T1DM rats, respectively, and alleviated pancreatic islet ß-cell damage. Overall, C1QB and NKG7 can increase the number of macrophages and T lymphocytes, respectively, causing pancreatic islet ß-cell damage and promoting T1DM in rats.

Procyanidins: A promising anti-diabetic agent with potential benefits on glucose metabolism and diabetes complications.

Diabetes mellitus (DM) is a complex disease with alarming worldwide health implications and high mortality rates, largely due to its complications such as cardiovascular disease, nephropathy, neuropathy, and retinopathy. Recent research has shown that procyanidins (PC), a type of flavonoid, have strong antioxidant and free radical elimination effects, and may be useful in improving glucose metabolism, enhancing pancreatic islet cell activity, and decreasing the prevalence of DM complications. This review article presents a systematic search for peer-reviewed articles on the use of PC in the treatment of DM, without any language restrictions. The article also discusses the potential for PC to sensitise DM medications and improve their efficacy. Recent in vivo and in vitro studies have demonstrated promising results in improving the biological activity and bioavailability of PC for the treatment of DM. The article concludes by highlighting the potential for novel materials and targeted drug delivery methods to enhance the pharmacokinetics and bioactivity of PC, leading to the creation of safer and more effective anti-DM medications in the future.

A Bioartificial Pancreas with "Immune Stealth" and Continuous Oxygen Supply for Islet Transplantation.

Transplantation of microencapsulated islet cells remains a promising strategy for the normalization of glucose metabolism control in type 1 diabetes mellitus. However, vigorous host immunologic rejection, fibrotic overgrowth around the microcapsules, and poor oxygen supply often lead to graft failure. Herein, a bioartificial pancreas is constructed, which incorporates the "stealth effect" based on polyethylene glycol copolymers and the high oxygen-carrying performance of fluorinated nanoparticles. Polycationic poly(l-lysine)-grafted-poly(ethylene glycol) is successfully coated on the surface of alginate microcapsules through electrostatic interaction, which can not only resist fibrinogen adhesion and avoid excessive fibrosis around the microcapsules but also isolate the host immune system from attacking, achieving a "stealth effect" of microencapsulated islet cells. Furthermore, the coloading of fluoride-based O2 nanocarriers gives them enhanced oxygen-carrying and continuous oxygen supply capabilities, thereby effectively prolonging the survival of islet cells. The intracapsular islet cells still display similar cell viability and almost normal insulin secretion function even in long-term culture under hypoxic conditions. Collectively, here a new approach is opened for microencapsulated islets to efficiently evade host immune attack and improve oxygen supply and a promising strategy is provided for islet transplantation in type 1 diabetes mellitus.

Exenatide prevents statin-related LDL receptor increase and improves insulin secretion in pancreatic beta cells (1.1E7) in a protein kinase A-dependent manner.

Statins are primary drugs in the treatment of hyperlipidemias. This group of drugs is known for its beneficial pleiotropic effects (e.g., reduction of inflammatory state). However, a growing body of evidence suggests its diabetogenic properties. The culpable mechanism is not completely understood and might be related to the damage to pancreatic beta cells. Therefore, we conceived an in vitro study to explore the impact of atorvastatin on pancreatic islet beta cells line (1.1.E7). We evaluated the influence on viability, insulin, low-density lipoprotein (LDL) receptor, and proprotein convertase subtilisin/kexin type 9 (PCSK9) expression. A significant drop in mRNA for proinsulin and insulin expression was noted. Concurrently, a rise in LDL receptor at the protein level in cells exposed to atorvastatin was noted. Further experiments have shown that exenatide - belonging to glucagon-like peptide 1 (GLP-1) analogs that are used in a treatment of diabetes and known for its weight reducing properties - can alleviate the observed alterations. In this case, the mechanism of action of exenatide was dependent on a protein kinase A pathway. In conclusion, our results support the hypothesis that statin may have diabetogenic properties, which according to our study is related to reduced insulin expression. The concomitant use of GLP-1 receptor agonist seemed to successfully revert insulin expression.

A New Berberine Preparation Protects Pancreatic Islet Cells from Apoptosis Mediated by Inhibition of Phospholipase A2/p38 MAPK Pathway.

We studied an amorphous solid dispersion of berberine with absorption enhancer sodium caprate (Huang-Gui solid dispersion preparations, HGSD). A therapeutic effect of HGSD was revealed in mice with type 2 diabetes mellitus and palmitate-induced injury to MIN6 ß-cells. HGSD treatment (150 mg/kg) improved glucose metabolism and decreased ß-cell apoptosis in diabetic mice. Furthermore, the effective component of HGSD berberine significantly attenuated the palmitate-induced decrease in MIN6 ß-cells viability and insulin secretion. Moreover, molecular docking analysis and Western blotting showed that berberine decreased cell apoptosis and expression of group VIA phospholipase A2 (iPLA2), p38 mitogen-activated protein kinase (p38 MAPK), and caspase-3. These data suggest that HGSD treatment protected ß-cells via inhibiting the iPLA2/p38 MAPK pathway.

Proteoglycan profiling of human, rat and mouse insulin-secreting cells.

Proteoglycans (PGs) are proteins with glycosaminoglycan (GAG) chains, such as chondroitin sulfate (CS) or heparan sulfate (HS), attached to serine residues. We have earlier shown that prohormones can carry CS, constituting a novel class of PGs. The mapping of GAG modifications of proteins in endocrine cells may thus assist us in delineating possible roles of PGs in endocrine cellular physiology. With this aim, we applied a glycoproteomic approach to identify PGs, their GAG chains and their attachment sites in insulin-secreting cells. Glycopeptides carrying GAG chains were enriched from human pancreatic islets, rat (INS-1 832/13) and mouse (MIN6, NIT-1) insulinoma cell lines by exchange chromatography, depolymerized with GAG lyases, and analyzed by nanoflow liquid chromatography tandem mass spectrometry. We identified CS modifications of chromogranin-A (CgA), islet amyloid polypeptide, secretogranin-1 and secretogranin-2, immunoglobulin superfamily member 10, and protein AMBP. Additionally, we identified two HS-modified prohormones (CgA and secretogranin-1), which was surprising, as prohormones are not typically regarded as HSPGs. For CgA, the glycosylation site carried either CS or HS, making it a so-called hybrid site. Additional HS sites were found on syndecan-1, syndecan-4, nerurexin-2, protein NDNF and testican-1. These results demonstrate that several prohormones, and other constituents of the insulin-secreting cells are PGs. Cell-targeted mapping of the GAG glycoproteome forms an important basis for better understanding of endocrine cellular physiology, and the novel CS and HS sites presented here provide important knowledge for future studies.

Expression of immunoreactive inducible nitric oxide synthase in pancreatic islet cells from newly diagnosed and long-term type 1 diabetic donors is heterogeneous and not disease-associated.

Exposure of isolated human islets to proinflammatory cytokines leads to up-regulation of inducible nitric oxide synthase (iNOS), raised NO, and beta cell toxicity. These findings have led to increasing interest in the clinical utility of iNOS blockade to mitigate beta cell destruction in human type 1 diabetes (T1D). However, recent studies show that iNOS-derived NO may also confer beta cell protection. To investigate this dichotomy, we compared islet cell distributions and intensity of iNOS immunostaining in pancreatic sections, co-stained for insulin and glucagon, from new-onset T1D donors (group 1), with non-diabetic autoantibody-negative (group 2), non-diabetic autoantibody-positive (group 3) and long-term diabetic donors (group 4). The cellular origins of iNOS, its frequency and graded intensities in islets and number in peri-islet, intra-islet and exocrine regions were determined. All donors showed iNOS positivity, irrespective of disease and presence of beta cells, had variable labelling intensities, without significant differences in the frequency of iNOS-positive islets among study groups. iNOS was co-localised in selective beta, alpha and other endocrine cells, and in beta cell-negative islets of diabetic donors. The number of peri- and intra-islet iNOS cells was low, being significantly higher in the peri-islet area. Exocrine iNOS cells also remained low, but were much lower in group 1. We demonstrate that iNOS expression in islet cells is variable, heterogeneous and independent of co-existing beta cells. Its distribution and staining intensities in islets and extra-islet areas do not correlate with T1D or its duration. Interventions to inactivate the enzyme to alleviate disease are currently not justified.

What does it take to consent to islet cell xenotransplantation?: Insights from an interview study with type 1 diabetes patients and review of the literature.

BACKGROUND: The transplantation of porcine islet cells provides a new potential therapy to treat patients with type 1 diabetes mellitus (T1DM). Compared to other biomedical technologies, xenotransplantation stands out in terms of its involvement of animals as graft sources, as well as the possible transmission of infectious diseases. As these aspects are especially relevant for potential xenotransplantation recipients, it is important to assess their opinion regarding this technology, in particular in terms of the requirements that should be met in the informed consent process for xenotransplantation. METHODS: We conducted qualitative interviews with seven T1DM patients to assess their information needs prior to xenotransplantation. Before the interview, the participants received a model informed consent form for a clinical trial with porcine islet cells transplantation. The interviews were transcribed and analysed using qualitative content analysis. RESULTS: In the interviews, we identified several requirements that are crucial for patients with T1DM in order to consider xenotransplantation as a potential treatment option: therapy-related requirements, professional care and supervision, successful behaviour and attitude management, improving quality of life, and managing control/self-determination challenges. Regarding the informed consent form, several of the participants' questions remained open and should be addressed in more detail. The interviewees stressed the importance of personal consultations. CONCLUSIONS: To become a sustainable therapeutic option, patients especially expected an improved diabetes control and a reduction of diabetes-related burdens. Health-related aspects prove to be pivotal for diabetic patients when considering porcine islet cell transplantation. The use of pigs as source for organ retrievals was not considered as problematic.

GATA factors in pancreas development and disease.

There is an urgent need for the development of novel therapeutics options for diabetic patients given the high prevalence of diabetes worldwide and that, currently, there is no cure for this disease. The transplantation of pancreatic islets that contain insulin-producing cells is a promising therapeutic alternative, particularly for type 1 diabetes. However, the shortage of organ donors constitutes a major limitation for this approach; thus, developing alternative sources of insulin-producing cells is of critical importance. In the last decade, our knowledge of the molecular mechanisms controlling embryonic pancreas development has significantly advanced. More importantly, this knowledge has provided the basis for the in vitro generation of insulin-producing cells from stem cells. Recent studies have revealed that GATA transcription factors are involved in various stages of pancreas formation and in the adult ß cell function. Here, we review the fundamental role of GATA transcription factors in pancreas morphogenesis and their association with congenital diseases associated with pancreas.

Interpenetrating Network of Alginate-Human Adipose Extracellular Matrix Hydrogel for Islet Cells Encapsulation.

Transplantation of microencapsulated islet cells holds great potential for the treatment of type 1 diabetes mellitus. However, its clinical translation is hampered by the peri-transplantation loss of islet viability and functionality in the microcapsules. In this work, a novel islet cells biomimetic microencapsulant material that is based on the interpenetrating networks of alginate and extracellular matrix (ECM) hydrogel composite (AEC) is presented. The ECM component is derived from human lipoaspirate. In situ encapsulation of pancreatic ß islet cells (MIN6 ß-cells) can be achieved via ionotropic gelation of the alginate matrix and thermal-induced gelation of the pepsin-solubilized ECM pre-gel. Due to the enhanced cell-matrix interaction, islets encapsulated within the AEC microcapsules (≈640 µm) display sevenfold increase in cell growth over 1 week of culture and characteristic glucose-stimulated insulin response in vitro. The results show that the AEC microcapsule is a potent platform to bioaugment the performance of islet cells.

MKP-5 Relieves Lipotoxicity-Induced Islet ß-Cell Dysfunction and Apoptosis via Regulation of Autophagy.

Mitogen-activated protein kinase phosphatase-5 (MKP-5) is a regulator of extracellular signaling that is known to regulate lipid metabolism. In this study, we found that obesity caused by a high-fat diet (HFD) decreased the expression of MKP-5 in the pancreas and primary islet cells derived from mice. Then, we further investigated the role of MKP-5 in the protection of islet cells from lipotoxicity by modulating MKP-5 expression. As a critical inducer of lipotoxicity, palmitic acid (PA) was used to treat islet ß-cells. We found that MKP-5 overexpression restored PA-mediated autophagy inhibition in Rin-m5f cells and protected these cells from PA-induced apoptosis and dysfunction. Consistently, a lack of MKP-5 aggravated the adverse effects of lipotoxicity. Islet cells from HFD-fed mice were infected using recombinant adenovirus expressing MKP-5 (Ad-MKP-5), and we found that Ad-MKP-5 was able to alleviate HFD-induced apoptotic protein activation and relieve the HFD-mediated inhibition of functional proteins. Notably, HFD-mediated impairments in autophagic flux were restored by Ad-MKP-5 transduction. Furthermore, the autophagy inhibitor 3-methyladenine (3-MA) was used to treat Rin-m5f cells, confirming that the MKP-5 overexpression suppressed apoptosis, dysfunction, inflammatory response, and oxidative stress induced by PA via improving autophagic signaling. Lastly, employing c-Jun amino-terminal kinas (JNK), P38, or extracellular-regulated kinase (ERK) inhibitors, we established that the JNK and P38 MAPK pathways were involved in the MKP-5-mediated apoptosis, dysfunction, and autophagic inhibition observed in islet ß cells in response to lipotoxicity.

Signaling Molecules Regulating Pancreatic Endocrine Development from Pluripotent Stem Cell Differentiation.

Diabetes is one of the leading causes of death globally. Currently, the donor pancreas is the only source of human islets, placing extreme constraints on supply. Hence, it is imperative to develop renewable islets for diabetes research and treatment. To date, extensive efforts have been made to derive insulin-secreting cells from human pluripotent stem cells with substantial success. However, the in vitro generation of functional islet organoids remains a challenge due in part to our poor understanding of the signaling molecules indispensable for controlling differentiation pathways towards the self-assembly of functional islets from stem cells. Since this process relies on a variety of signaling molecules to guide the differentiation pathways, as well as the culture microenvironments that mimic in vivo physiological conditions, this review highlights extracellular matrix proteins, growth factors, signaling molecules, and microenvironments facilitating the generation of biologically functional pancreatic endocrine cells from human pluripotent stem cells. Signaling pathways involved in stepwise differentiation that guide the progression of stem cells into the endocrine lineage are also discussed. The development of protocols enabling the generation of islet organoids with hormone release capacities equivalent to native adult islets for clinical applications, disease modeling, and diabetes research are anticipated.

[Morphometry of adipose tissue for prediction of the outcomes of total pancreatectomy with pancreatic islets autotransplantation in patients with chronic pancreatitis]. / Morfometriya zhirovoi kletchatki dlya prognoza rezul'tatov total'noi pankreatektomii s autotransplantatsiei ostrovkov podzheludochnoi zhelezy u bol'nykh khronicheskim pankreatitom.

OBJECTIVE: To compare different clinical and morphometric features of patients undergoing TPAIT for prediction of postoperative outcomes. MATERIAL AND METHODS: A retrospective review enrolled patients who underwent TPAIT for the period from January 2007 to October 2017. Morphometric parameters were analyzed using preoperative CT scans and patients were grouped to examine association of these characteristics with postoperative morbidity. Sarcopenia was defined as the presence of a TPA in the lowest sex-specific quartile. The impact of sarcopenia on pancreatic islet features, perioperative blood transfusion, ICU- and hospital-stay, complications, repeated admission within 90 days and islet function was assessed. RESULTS: A total of 34 patients were included in this study (12 males and 24 females). At the time of diagnosis, mean age of patients was 43.1 years. Mean body mass index (BMI) in sarcopenic patients was 24.9 kg/m2, mean BMI in those without sarcopenia - 24.8 kg/m2 (p=1.00). Various surgical complications were observed in 11 patients (32.3%). Patients with sarcopenia experienced more complications (83.3%) compared with patients without sarcopenia (50%). However, differences were not significant (p=0.31). Islet characteristics (islet numbers, purity), readmission, ICU- and hospital-stay, incidence of blood transfusion and islet function were also similar in both groups. CONCLUSION: Sarcopenia is not a predictor of postoperative complications and islet cell function in chronic pancreatitis patients following TPAIT.

Use of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells.

This study provides an assessment of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells. The system combines microfluidic technology and nanoliter-scale reactions. We sequenced 622 cells, allowing identification of 341 islet cells with high-quality gene expression profiles. The cells clustered into populations of α-cells (5%), ß-cells (92%), δ-cells (1%), and pancreatic polypeptide cells (2%). We identified cell-type-specific transcription factors and pathways primarily involved in nutrient sensing and oxidation and cell signaling. Unexpectedly, 281 cells had to be removed from the analysis due to low viability, low sequencing quality, or contamination resulting in the detection of more than one islet hormone. Collectively, we provide a resource for identification of high-quality gene expression datasets to help expand insights into genes and pathways characterizing islet cell types. We reveal limitations in the C1 Fluidigm cell capture process resulting in contaminated cells with altered gene expression patterns. This calls for caution when interpreting single-cell transcriptomics data using the C1 Fluidigm system.

Co-Transplantation of Pancreatic Islet Cells and Mesenchymal Bone Marrow Precursors on Titanium Nickelide Scaffolds in Alloxan-Induced Diabetes Mellitus.

We studied therapeutic activity of co-transplantation of allogeneic pancreatic islet cells and mesenchymal bone marrow progenitors on TiNi scaffolds in Wistar rats with experimental alloxan-induced diabetes mellitus. In preliminary experiments with co-culturing of cells in different proportions followed by their transplantation on tissue-engineered constructs, the optimum ratio of these cells was determined - 3:1. Regeneration was assessed by biochemical methods by the blood levels of glucose and glycosylated hemoglobin on days 15, 30, and 5. In the group with combined cell transplantation on TiNi scaffold, normalization of the studied biochemical parameters occurred earlier than after monotherapy with allogenic islet cells and was associated with an increase in animal lifespan. Normalization of the parameters of bone marrow hemopoiesis, in particular, the number of myelokaryocytes and erythroblasts was also noted.

Organ donor pancreases for the study of human islet cell histology and pathophysiology: a precious and valuable resource.

Direct in vivo assessment of pancreatic islet-cells for the study of the pathophysiology of diabetes in humans is hampered by anatomical and technological hurdles. To date, most of the information that has been generated is derived from histological studies performed on pancreatic tissue from autopsy, surgery, in vivo biopsy or organ donation. Each approach has its advantages and disadvantages (as summarised in this commentary); however, in this edition of Diabetologia, Kusmartseva et al ( https://doi.org/10.1007/s00125-017-4494-x ) provide further evidence to support the use of organ donor pancreases for the study of human diabetes. They show that length of terminal hospitalisation of organ donors prior to death does not seem to influence the frequency of inflammatory cells infiltrating the pancreas and the replication of beta cells. These findings are reassuring, demonstrating the reliability of this precious and valuable resource for human islet cells research.

Distribution of IL-1ß immunoreactive cells in pancreatic biopsies from living volunteers with new-onset type 1 diabetes: comparison with donors without diabetes and with longer duration of disease.

AIMS/HYPOTHESIS: Although IL-1ß is considered a key mediator of beta cell destruction, its cellular expression in islets during early type 1 diabetes remains unclear. We compared its expression in rare pancreatic biopsies from new-onset living volunteers with its expression in cadaveric pancreas sections from non-diabetic autoantibody-positive and -negative individuals and those with long-standing disease. METHODS: Pancreatic biopsy sections from six new-onset living volunteers (group 1) and cadaveric sections from 13 non-diabetic autoantibody-negative donors (group 2), four non-diabetic autoantibody-positive donors (group 3) and nine donors with diabetes of longer duration (0.25-12 years of disease; group 4) were triple-immunostained for IL-1ß, insulin and glucagon. Intra- and peri-islet IL-1ß-positive cells in insulin-positive and -negative islets and in random exocrine fields were enumerated. RESULTS: The mean number of IL-1ß-positive cells per islet from each donor in peri- and intra-islet regions was <1.25 and <0.5, respectively. In all study groups, the percentage of islets with IL-1ß cells in peri- and/or intra-islet regions was highly variable and ranged from 4.48% to 17.59% in group 1, 1.42% to 44.26% in group 2, 7.93% to 17.53% in group 3 and 3.85% to 42.86% in group 4, except in a single case where the value was 75%. In 25/32 donors, a higher percentage of islets showed IL-1ß-positive cells in peri-islet than in intra-islet regions. In sections from diabetic donors (groups 1 and 4), a higher mean number of IL-1ß-positive cells occurred in insulin-positive islets than in insulin-negative islets. In group 2, 70-90% of islets in 3/13 sections had weak-to-moderate IL-1ß staining in alpha cells but staining was virtually absent or substantially reduced in the remaining groups. The mean number of exocrine IL-1ß-positive cells in group 1 was lower than in the other groups. CONCLUSIONS/INTERPRETATION: At onset of type 1 diabetes, the low number of islet-associated IL-1ß-positive cells may be insufficient to elicit beta cell destruction. The variable expression in alpha cells in groups 2-4 suggests their cellular heterogeneity and probable physiological role. The significance of a higher but variable number of exocrine IL-1ß-positive cells seen in non-diabetic individuals and those with long-term type 1 diabetes remains unclear.