Functional Beta Cell Mass from Device-Encapsulated hESC-Derived Pancreatic Endoderm Achieving Metabolic Control

From stem cells to pancreatic β-cells: strategies, applications, and potential treatments for diabetes

Loss and functional failure of pancreatic β-cells results in disruption of glucose homeostasis and progression of diabetes. Although whole pancreas or pancreatic islet transplantation serves as a promising approach for β-cell replenishment and diabetes therapy, the severe scarcity of donor islets makes it unattainable for most diabetic patients. Stem cells, particularly induced pluripotent stem cells (iPSCs), are promising for the treatment of diabetes owing to their self-renewal capacity and ability to differentiate into functional β-cells. In this review, we first introduce the development of functional β-cells and their heterogeneity and then turn to highlight recent advances in the generation of β-cells from stem cells and their potential applications in disease modeling, drug discovery and clinical therapy. Finally, we have discussed the current challenges in developing stem cell-based therapeutic strategies for improving the treatment of diabetes. Although some significant technical hurdles remain, stem cells offer great hope for patients with diabetes and will certainly transform future clinical practice.

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.

Encapsulation and immune protection for type 1 diabetes cell therapy

Type 1 Diabetes (T1D) involves the autoimmune destruction of insulin-producing β-cells in the pancreas. Exogenous insulin injections are the current therapy but are user-dependent and cannot fully recapitulate physiological insulin secretion dynamics. Since the emergence of allogeneic cell therapy for T1D, the Edmonton Protocol has been the most promising immunosuppression protocol for cadaveric islet transplantation, but the lack of donor islets, poor cell engraftment, and required chronic immunosuppression have limited its application as a therapy for T1D. Encapsulation in biomaterials on the nano-, micro-, and macro-scale offers the potential to integrate islets with the host and protect them from immune responses. This method can be applied to different cell types, including cadaveric, porcine, and stem cell-derived islets, mitigating the issue of a lack of donor cells. This review covers progress in the efforts to integrate insulin-producing cells from multiple sources to T1D patients as a form of cell therapy.

Differentiation of Uc-MSCs into insulin secreting islet-like clusters by trypsin through TGF-beta signaling pathway

Differentiation of human umbilical cord mesenchymal stem cells (Uc-MSCs) into islet-like clusters which are capable of synthesizing and secreting insulin can potentially serve as donors for islet transplantation in the patient deficiency in islet β cell function both in type 1 or type 2 diabetic patients. Therefore, we developed an easy and higher efficacy approach by trypsinazing the Uc-MSCs and followed culture in differentiation medium to induce of Uc-MSCs differentiation into islet-like clusters, and the potential mechanism that in the early stage of differentiation was also investigated by using RNA-sequencing and bioinformatics. Results show that induction efficacy was reached to 98% and TGF-β signaling pathway may play critical role in the early stage differentiation, it was further confirmed that the retardant effect of differentiation progress either in cell morphology or in islet specific genes expression can be observed upon blocking the activation of TGF-β signaling pathway using specific inhibitor of LY2109761 (TβRI/II kinase inhibitor). Our current study, for the first time, development a protocol for differentiation of Uc-MSCs into islet-like clusters, and revealed the importance of TGF-β signaling pathway in the early stage of differentiation of Uc-MSCs into islet-like clusters. Our study will provide alternative approach for clinical treatment of either type I or type II diabtes mellitus with dysfunctional pancreatic islets.

Encapsulated stem cell-derived β cells exert glucose control in patients with type 1 diabetes

Clinical studies on the treatment of type 1 diabetes with device-encapsulated pancreatic precursor cells derived from human embryonic stem cells found that insulin output was insufficient for clinical benefit. We are conducting a phase 1/2, open-label, multicenter trial aimed at optimizing cell engraftment (ClinicalTrials.gov identifier: NCT03163511 ). Here we report interim, 1-year outcomes in one study group that received 2-3-fold higher cell doses in devices with an optimized membrane perforation pattern. β cell function was measured by meal-stimulated plasma C-peptide levels at 3-month intervals, and the effect on glucose control was assessed by continuous glucose monitoring (CGM) and insulin dosing. Of 10 patients with undetectable baseline C-peptide, three achieved levels ≥0.1 nmol l-1 from month 6 onwards that correlated with improved CGM measures and reduced insulin dosing, indicating a glucose-controlling effect. The patient with the highest C-peptide (0.23 nmol l-1) increased CGM time-in-range from 55% to 85% at month 12; β cell mass in sentinel devices in this patient at month 6 was 4% of the initial cell mass, indicating directions for improving efficacy.

Encapsulation of stem-cell derived β-cells: A promising approach for the treatment for type 1 diabetes mellitus

Type 1 diabetes mellitus is an auto-immune disease causing the T-cell mediated destruction of insulin-producing β-cells, resulting in chronic hyperglycemia. Current treatments such as insulin replacement therapy or the transplantation of pancreas or pancreatic islets present major disadvantages such as the constant need of drugs, as well as a shortage of donor organs. In this review, we discuss a sustainable solution to overcome these limitations combining the use of β-cells, derived from stem cells, and their encapsulation within a protective matrix. This article provides an exhaustive overview of currently investigated stem cell sources including embryonic, mesenchymal as well as induced pluripotent stem cells in combination with various up to date encapsulation methods allowing the formation of immuno-protective devices. In order to identify current limitations of this interdisciplinary therapeutic approach and to find sustainable solutions, it is essential to consider key aspects from all involved domains. This includes biological parameters such as the stem cell origin but also the different aspects of the encapsulation process, the used materials and their physico-chemical properties such as elasticity, porosity and permeability cut-off as well as the best implantation sites allowing efficient and self-autonomous control of glycemia by the transplanted encapsulated cells.

Emerging drugs for the treatment of type 1 diabetes mellitus: a review of phase 2 clinical trials

INTRODUCTION

Despite therapeutic advances in the field of diabetes management since the discovery of insulin 100 years ago, there are still unmet clinical needs for people with type 1 diabetes mellitus (T1DM).

AREAS COVERED

Genetic testing and islet autoantibodies testing allow researchers to design prevention studies. This review discusses the emerging therapy for prevention of T1DM, disease modification therapy in early course of T1DM, and therapies and technologies for established T1DM. We focus on phase 2 clinical trials with promising results, thus avoiding the exhausted list of every new therapy for T1DM.

EXPERT OPINION

Teplizumab has demonstrated potential as a preventative agent for individuals at risk prior to the onset of overt dysglycemia. However, these agents are not without side effects, and there are uncertainties on long-term safety. Technological advances have led a substantial influence on quality of life of people suffering from T1DM. There remains variation in uptake of new technologies across the globe. Novel insulins (ultra-long acting), oral insulin, and inhaled insulin attempt to narrow the gap of unmet needs. Islet cell transplant is another exciting field, and stem cell therapy might have potential to provide unlimited supply of islet cells.

A glucose-blue light AND gate-controlled chemi-optogenetic cell-implanted therapy for treating type-1 diabetes in mice

Exogenous insulin therapy is the mainstay treatment for Type-1 diabetes (T1D) caused by insulin deficiency. A fine-tuned insulin supply system is important to maintain the glucose homeostasis. In this study, we present a designed cell system that produces insulin under an AND gate control, which is triggered only in the presence of both high glucose and blue light illumination. The glucose-sensitive GIP promoter induces the expression of GI-Gal4 protein, which forms a complex with LOV-VP16 in the presence of blue light. The GI-Gal4:LOV-VP16 complex then promotes the expression of UAS-promoter-driven insulin. We transfected these components into HEK293T cells, and demonstrated the insulin was secreted under the AND gate control. Furthermore, we showed the capacity of the engineered cells to improve the blood glucose homeostasis through implantation subcutaneously into Type-1 diabetes mice.

CDK8/19 inhibition plays an important role in pancreatic β-cell induction from human iPSCs

BACKGROUND

Transplantation of differentiated cells from human-induced pluripotent stem cells (hiPSCs) holds great promise for clinical treatments. Eliminating the risk factor of malignant cell transformation is essential for ensuring the safety of such cells. This study was aimed at assessing and mitigating mutagenicity that may arise during the cell culture process in the protocol of pancreatic islet cell (iPIC) differentiation from hiPSCs.

METHODS

We evaluated the mutagenicity of differentiation factors used for hiPSC-derived pancreatic islet-like cells (iPICs). We employed Ames mutagenicity assay, flow cytometry analysis, immunostaining, time-resolved fluorescence resonance energy transfer-based (TR-FRET) cell-free dose-response assays, single-cell RNA-sequencing and in vivo efficacy study.

RESULTS

We observed a mutagenic effect of activin receptor-like kinase 5 inhibitor II (ALK5iII). ALK5iII is a widely used β-cell inducer but no other tested ALK5 inhibitors induced β-cells. We obtained kinase inhibition profiles and found that only ALK5iII inhibited cyclin-dependent kinases 8 and 19 (CDK8/19) among all ALK5 inhibitors tested. Consistently, CDK8/19 inhibitors efficiently induced β-cells in the absence of ALK5iII. A combination treatment with non-mutagenic ALK5 inhibitor SB431542 and CDK8/19 inhibitor senexin B afforded generation of iPICs with in vitro cellular composition and in vivo efficacy comparable to those observed with ALK5iII.

CONCLUSION

Our findings suggest a new risk mitigation approach for cell therapy and advance our understanding of the β-cell differentiation mechanism.

Tissue engineering approaches and generation of insulin-producing cells to treat type 1 diabetes

Tissue engineering (TE) has become a new effective solution to a variety of medical problems, including diabetes. Mesenchymal stem cells (MSCs), which have the ability to differentiate into endodermal and mesodermal cells, appear to be appropriate for this function. The purpose of this review was to evaluate the outcomes of various researches on the insulin-producing cells (IPCs) generation from MSCs with TE approaches to increase efficacy of type 1 diabetes treatments. The search was performed in PubMed/Medline, Scopus and Embase databases until 2021. Studies revealed that MSCs could also differentiate into IPCs under certain conditions. Therefore, a wide range of protocols have been used for this differentiation, but their effectiveness is very different. Scaffolds can provide a microenvironment that enhances the MSCs to IPCs differentiation, improves their metabolic activity and up-regulate pancreatic-specific transcription factors. They also preserve IPCs architecture and enhance insulin production as well as protect against cell death. This systematic review offers a framework for prospective research based on data. In vitro and in vivo evidence suggests that scaffold-based TE can improve the viability and function of IPCs.

Comparison of Omentum and Subcutis as Implant Sites for Device-Encapsulated Human iPSC-Derived Pancreatic Endoderm in Nude Rats

Subcutaneous implants of device-encapsulated stem cell-derived pancreatic endoderm (PE) can establish a functional beta cell mass (FBM) with metabolic control in immune-compromised mice. In a study with human-induced pluripotent stem cell-PE, this outcome was favored by a preformed pouch which allowed lesion-free insertion of devices in a pre-vascularized site. This was not reproduced in nude rats, known to exhibit a higher innate reactivity than mice and therefore relevant as preclinical model: a dense fibrotic capsule formed around subcutis (SC) implants with virtually no FBM formation. Placement in omentum (OM) of nude rats provided a less fibrous, better vascularized environment than SC. It resulted in less donor cell loss (56% recovery at post-transplant-PT week 3 versus 16% in SC) allowing FBM-formation. At PT week 30, 6/13 OM-recipients exhibited glucose-induced plasma hu-C-peptide to 0.1-0.4 ng/ml, versus 0/8 in SC-recipients. These levels are more than 10-fold lower than in a state of metabolic control. This shortcoming is not caused by inadequate glucose responsiveness of the beta cells but by their insufficient number. The size of the formed beta cell mass (0.4 ± 0.2 µl) was lower than that reported in mice receiving the same cell product subcutaneously; the difference is attributed to a lower expansion of pancreatic progenitor cells and to their lower degree of differentiation to beta cells. This study in the nude rat model demonstrates that OM provides a better environment for formation of beta cells in device-encapsulated PE-implants than SC. It also identified targets for increasing their dose-efficacy.

Characterization and reduction of non-endocrine cells accompanying islet-like endocrine cells differentiated from human iPSC

The differentiation of pancreatic endocrine cells from human pluripotent stem cells has been thoroughly investigated for their application in cell therapy against diabetes. Although non-endocrine cells are inevitable contaminating by-products of the differentiation process, a comprehensive profile of such cells is lacking. Therefore, we characterized non-endocrine cells in iPSC-derived pancreatic islet cells (iPIC) using single-cell transcriptomic analysis. We found that non-endocrine cells consist of (1) heterogeneous proliferating cells, and (2) cells with not only pancreatic traits but also liver or intestinal traits marked by FGB or AGR2. Non-endocrine cells specifically expressed FGFR2, PLK1, and LDHB. We demonstrated that inhibition of pathways involving these genes selectively reduced the number of non-endocrine cells in the differentiation process. These findings provide useful insights into cell purification approaches and contribute to the improvement of the mass production of endocrine cells for stem cell-derived cell therapy for diabetes.

Implanted pluripotent stem-cell-derived pancreatic endoderm cells secrete glucose-responsive C-peptide in patients with type 1 diabetes

An open-label, first-in-human phase 1/2 study is being conducted to evaluate the safety and efficacy of pancreatic endoderm cells (PECs) implanted in non-immunoprotective macroencapsulation devices for the treatment of type 1 diabetes. We report an analysis on 1 year of data from the first cohort of 15 patients from a single trial site that received subcutaneous implantation of cell products combined with an immunosuppressive regimen. Implants were well tolerated with no teratoma formation or severe graft-related adverse events. After implantation, patients had increased fasting C-peptide levels and increased glucose-responsive C-peptide levels and developed mixed meal-stimulated C-peptide secretion. There were immunosuppression-related transient increases in circulating regulatory T cells, PD1^high T cells, and IL17A⁺CD4⁺ T cells. Explanted grafts contained cells with a mature β cell phenotype that were immunoreactive for insulin, islet amyloid polypeptide, and MAFA. These data, and associated findings (Shapiro et al., 2021), are the first reported evidence of meal-regulated insulin secretion by differentiated stem cells in patients.

Cell therapy research for Diabetes: Pancreatic β cell differentiation from pluripotent stem cells

Human pluripotent stem cells (PSCs), both embryonic and induced pluripotent stem cells (iPSCs), have been differentiated into pancreatic β isletsin vitrofor more than a decade. The idea is to get enough β cells for cell transplantation for diabetics. Finding a standard cell therapy for diabetes is essential because of the logarithmic increase in the global population of people with diabetes and the insufficient availability of the human cadaveric pancreas. Moreover, with better insights into developmental biology, thein vitroβ cell differentiation protocols have depended on thein vivoβ cell organogenesis. Various protocols for pancreatic β cell differentiation have been developed. Such protocols are based on the modulation of cell signalling pathways with growth factors, small molecules, RNAi approaches, directed differentiation using transcription factors, genome editing. Growth factor free differentiation protocols, epigenetic modulations, 3D differentiation approaches, and encapsulation strategies have also been reported for better glycemic control and endocrine modulations. Here, we have reviewed various aforementionedin vitroβ cell differentiation protocols from human PSCs, their respective comparisons, challenges, past, present, and future. The literature has been reviewed primarily from PubMed from the year 2000 till date using the mentioned keywords.

A therapeutic convection-enhanced macroencapsulation device for enhancing β cell viability and insulin secretion

Islet transplantation for type 1 diabetes treatment has been limited by the need for lifelong immunosuppression regimens. This challenge has prompted the development of macroencapsulation devices (MEDs) to immunoprotect the transplanted islets. While promising, conventional MEDs are faced with insufficient transport of oxygen, glucose, and insulin because of the reliance on passive diffusion. Hence, these devices are constrained to two-dimensional, wafer-like geometries with limited loading capacity to maintain cells within a distance of passive diffusion. We hypothesized that convective nutrient transport could extend the loading capacity while also promoting cell viability, rapid glucose equilibration, and the physiological levels of insulin secretion. Here, we showed that convective transport improves nutrient delivery throughout the device and affords a three-dimensional capsule geometry that encapsulates 9.7-fold-more cells than conventional MEDs. Transplantation of a convection-enhanced MED (ceMED) containing insulin-secreting β cells into immunocompetent, hyperglycemic rats demonstrated a rapid, vascular-independent, and glucose-stimulated insulin response, resulting in early amelioration of hyperglycemia, improved glucose tolerance, and reduced fibrosis. Finally, to address potential translational barriers, we outlined future steps necessary to optimize the ceMED design for long-term efficacy and clinical utility.

Engineering islets from stem cells for advanced therapies of diabetes

Diabetes mellitus is a metabolic disorder that affects more than 460 million people worldwide. Type 1 diabetes (T1D) is caused by autoimmune destruction of β-cells, whereas type 2 diabetes (T2D) is caused by a hostile metabolic environment that leads to β-cell exhaustion and dysfunction. Currently, first-line medications treat the symptomatic insulin resistance and hyperglycaemia, but do not prevent the progressive decline of β-cell mass and function. Thus, advanced therapies need to be developed that either protect or regenerate endogenous β-cell mass early in disease progression or replace lost β-cells with stem cell-derived β-like cells or engineered islet-like clusters. In this Review, we discuss the state of the art of stem cell differentiation and islet engineering, reflect on current and future challenges in the area and highlight the potential for cell replacement therapies, disease modelling and drug development using these cells. These efforts in stem cell and regenerative medicine will lay the foundations for future biomedical breakthroughs and potentially curative treatments for diabetes.

Production and Characterization of a Conditionally Immortalized Dog Beta-Cell Line from Fetal Canine Pancreas

Since the 1970s, rodent and human insulin-secreting pancreatic beta-cell lines have been developed and found useful for studying beta-cell biology. Surprisingly, although the dog has been widely used as a translational model for diabetes, no canine insulin-secreting beta cells have ever been produced. Here, a targeted oncogenesis protocol previously described by some of us for generating human beta cells was adapted to produce canine beta cells. Canine fetal pancreata were obtained by cesarean section between 42 and 55 days of gestation, and fragments of fetal glands were transduced with a lentiviral vector expressing SV40LT under the control of the insulin promoter. Two Lox P sites flanking the sequence allowed subsequent transgene excision by Cre recombinase expression. When grafted into SCID mice, these transduced pancreata formed insulinomas. ACT-164 is the cell line described in this report. Insulin mRNA expression and protein content were lower than reported with adult cells, but the ACT-164 cells were functional, and their insulin production in vitro increased under glucose stimulation. Transgene excision upon Cre expression arrested proliferation and enhanced insulin expression and production. When grafted in SCID mice, intact and excised cells reversed chemically induced diabetes. We have thus produced an excisable canine beta-cell line. These cells may play an important role in the study of several aspects of the cell transplantation procedure including the encapsulation process, which is difficult to investigate in rodents. Although much more work is needed to improve the excision procedure and achieve 100% removal of large T antigen expression, we have shown that functional cells can be obtained and might in the future be used for replacement therapy in diabetic dogs.

A nanofibrous encapsulation device for safe delivery of insulin-producing cells to treat type 1 diabetes

Transplantation of stem cell-derived β (SC-β) cells represents a promising therapy for type 1 diabetes (T1D). However, the delivery, maintenance, and retrieval of these cells remain a challenge. Here, we report the design of a safe and functional device composed of a highly porous, durable nanofibrous skin and an immunoprotective hydrogel core. The device consists of electrospun medical-grade thermoplastic silicone-polycarbonate-urethane and is soft but tough (~15 megapascal at a rupture strain of >2). Tuning the nanofiber size to less than ~500 nanometers prevented cell penetration while maintaining maximum mass transfer and decreased cellular overgrowth on blank (cell-free) devices to as low as a single-cell layer (~3 micrometers thick) when implanted in the peritoneal cavity of mice. We confirmed device safety, indicated as continuous containment of proliferative cells within the device for 5 months. Encapsulating syngeneic, allogeneic, or xenogeneic rodent islets within the device corrected chemically induced diabetes in mice and cells remained functional for up to 200 days. The function of human SC-β cells was supported by the device, and it reversed diabetes within 1 week of implantation in immunodeficient and immunocompetent mice, for up to 120 and 60 days, respectively. We demonstrated the scalability and retrievability of the device in dogs and observed viable human SC-β cells despite xenogeneic immune responses. The nanofibrous device design may therefore provide a translatable solution to the balance between safety and functionality in developing stem cell-based therapies for T1D.

Formation of amyloid in encapsulated human pancreatic and human stem cell-generated beta cell implants

Detection of amyloid in intraportal islet implants of type 1 diabetes patients has been proposed as cause in their functional decline. The present study uses cultured adult human islets devoid of amyloid to examine conditions of its formation. After intraportal injection in patients, amyloid deposits <15 µm diameter were identified in 5%-12% of beta cell containing aggregates, 3-76 months posttransplant. Such deposits also formed in glucose-controlling islet implants in the kidney of diabetic mice but not in failing implants. Alginate-encapsulated islets formed amyloid during culture when functional, and in all intraperitoneal implants that corrected diabetes in mice, exhibiting larger sizes than in functioning nonencapsulated implants. After intraperitoneal injection in a patient, retrieved single capsules presented amyloid near living beta cells, whereas no amyloid occurred in clustered capsules with dead cells. Amyloid was also demonstrated in functional human stem cell-generated beta cell implants in subcutaneous devices of mice. Deposits up to 35 µm diameter were localized in beta cell-enriched regions and related to an elevated IAPP over insulin ratio in the newly generated beta cells. Amyloid in device-encapsulated human stem cell-generated beta cell implants marks the formation of a functional beta cell mass but also an imbalance between its activated state and its microenvironment.

Glucose Response by Stem Cell-Derived β Cells In Vitro Is Inhibited by a Bottleneck in Glycolysis

Stem cell-derived β (SC-β) cells could provide unlimited human β cells toward a curative diabetes treatment. Differentiation of SC-β cells yields transplantable islets that secrete insulin in response to glucose challenges. Following transplantation into mice, SC-β cell function is comparable to human islets, but the magnitude and consistency of response in vitro are less robust than observed in cadaveric islets. Here, we profile metabolism of SC-β cells and islets to quantify their capacity to sense glucose and identify reduced anaplerotic cycling in the mitochondria as the cause of reduced glucose-stimulated insulin secretion in SC-β cells. This activity can be rescued by challenging SC-β cells with intermediate metabolites from the TCA cycle and late but not early glycolysis, downstream of the enzymes glyceraldehyde 3-phosphate dehydrogenase and phosphoglycerate kinase. Bypassing this metabolic bottleneck results in a robust, bi-phasic insulin release in vitro that is identical in magnitude to functionally mature human islets.

Glucose-stimulated insulin secretion is deficient in stem cell-derived β (SC-β) cells in vitro. Davis et al. use metabolomic analysis to define a glycolytic bottleneck inhibiting glucose metabolism and sensing in SC-β cells. Cell-permeable intermediates bypass this bottleneck, as does transplantation in vivo, producing insulin secretion indistinguishable from human islets.

Applications of iPSC-derived beta cells from patients with diabetes

Improved stem cell-derived pancreatic islet (SC-islet) differentiation protocols robustly generate insulin-secreting β cells from patient induced pluripotent stem cells (iPSCs). These advances are enabling in vitro disease modeling studies and the development of an autologous diabetes cell replacement therapy. SC-islet technology elucidates key features of human pancreas development and diabetes disease progression through the generation of pancreatic progenitors, endocrine progenitors, and β cells derived from diabetic and nondiabetic iPSCs. Combining disease modeling with gene editing and next-generation sequencing reveals the impact of diabetes-causing mutations and diabetic phenotypes on multiple islet cell types. In addition, the supply of SC-islets, containing β and other islet cell types, is unlimited, presenting an opportunity for personalized medicine and overcoming several disadvantages posed by donor islets. This review highlights relevant studies involving iPSC-β cells and progenitors, encompassing new conclusions involving cells from patients with diabetes and the therapeutic potential of iPSC-β cells.

Improved differentiation protocols generate pancreatic islet from patient stem cells

Diabetic stem cell-derived islet studies identified key markers for cell function

Gene editing aims to address unmet needs for stem cell therapy field

Stem cell-derived islets are a promising source for diabetes stem cell therapy

The Current Status of Bioartificial Pancreas Devices

Type 1 diabetes mellitus is a common and highly morbid disease for which there is no cure. Treatment primarily involves exogenous insulin administration, and, under specific circumstances, islet or pancreas transplantation. However, insulin replacement alone fails to replicate the endocrine function of the pancreas and does not provide durable euglycemia. In addition, transplantation requires lifelong use of immunosuppressive medications, which has deleterious side effects, is expensive, and is inappropriate for use in adolescents. A bioartificial pancreas that provides total endocrine pancreatic function without immunosuppression is a potential therapy for treatment of type 1 diabetes. Numerous models are in development and take different approaches to cell source, encapsulation method, and device implantation location. We review current therapies for type 1 diabetes mellitus, the requirements for a bioartificial pancreas, and quantitatively compare device function.

Functional maturation of immature β cells: A roadblock for stem cell therapy for type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease caused by the specific destruction of pancreatic islet β cells and is characterized as the absolute insufficiency of insulin secretion. Current insulin replacement therapy supplies insulin in a non-physiological way and is associated with devastating complications. Experimental islet transplantation therapy has been proven to restore glucose homeostasis in people with severe T1DM. However, it is restricted by many factors such as severe shortage of donor sources, progressive loss of donor cells, high cost, etc. As pluripotent stem cells have the potential to give rise to all cells including islet β cells in the body, stem cell therapy for diabetes has attracted great attention in the academic community and the general public. Transplantation of islet β-like cells differentiated from human pluripotent stem cells (hPSCs) has the potential to be an excellent alternative to islet transplantation. In stem cell therapy, obtaining β cells with complete insulin secretion in vitro is crucial. However, after much research, it has been found that the β-like cells obtained by in vitro differentiation still have many defects, including lack of adult-type glucose stimulated insulin secretion, and multi-hormonal secretion, suggesting that in vitro culture does not allows for obtaining fully mature β-like cells for transplantation. A large number of studies have found that many transcription factors play important roles in the process of transforming immature to mature human islet β cells. Furthermore, PDX1, NKX6.1, SOX9, NGN3, PAX4, etc., are important in inducing hPSC differentiation in vitro. The absent or deficient expression of any of these key factors may lead to the islet development defect in vivo and the failure of stem cells to differentiate into genuine functional β-like cells in vitro. This article reviews β cell maturation in vivo and in vitro and the vital roles of key molecules in this process, in order to explore the current problems in stem cell therapy for diabetes.

Building Biomimetic Potency Tests for Islet Transplantation

Diabetes is a disease of insulin insufficiency, requiring many to rely on exogenous insulin with constant monitoring to avoid a fatal outcome. Islet transplantation is a recent therapy that can provide insulin independence, but the procedure is still limited by both the availability of human islets and reliable tests to assess their function. While stem cell technologies are poised to fill the shortage of transplantable cells, better methods are still needed for predicting transplantation outcome. To ensure islet quality, we propose that the next generation of islet potency tests should be biomimetic systems that match glucose stimulation dynamics and cell microenvironmental preferences and rapidly assess conditional and continuous insulin secretion with minimal manual handing. Here, we review the current approaches for islet potency testing and outline technologies and methods that can be used to arrive at a more predictive potency test that tracks islet secretory capacity in a relevant context. With the development of potency tests that can report on islet secretion dynamics in a context relevant to their intended function, islet transplantation can expand into a more widely accessible and reliable treatment option for individuals with diabetes.

A Stem Cell Approach to Cure Type 1 Diabetes

Treatment of type 1 diabetes with insulin injection is expensive, complicated, and insufficient. While cadaveric islet transplantations coupled with immunosuppressants can cure diabetes, the scarcity of acceptable islets is problematic. Developmental research on pancreas formation has informed in vitro differentiation of human pluripotent stem cells into functional islets. Although generating β cells from stem cells offers a potential cure for type 1 diabetes, several challenges remain, including protecting the cells from the immune system.

Lessons from Human Islet Transplantation Inform Stem Cell-Based Approaches in the Treatment of Diabetes

Diabetes mellitus is characterized by the body's inability to control blood glucose levels within a physiological range due to loss and/or dysfunction of insulin producing beta cells. Progressive beta cell loss leads to hyperglycemia and if untreated can lead to severe complications and/or death. Treatments at this time are limited to pharmacologic therapies, including exogenous insulin or oral/injectable agents that improve insulin sensitivity or augment endogenous insulin secretion. Cell transplantation can restore physiologic endogenous insulin production and minimize hyper- and hypoglycemic excursions. Islet isolation procedures and management of transplant recipients have advanced over the last several decades; both tight glycemic control and insulin independence are achievable. Research has been conducted in isolating islets, monitoring islet function, and mitigating the immune response. However, this procedure is still only performed in a small minority of patients. One major barrier is the scarcity of human pancreatic islet donors, variation in donor pancreas quality, and variability in islet isolation success. Advances have been made in generation of glucose responsive human stem cell derived beta cells (sBCs) and islets from human pluripotent stem cells using directed differentiation. This is an emerging promising treatment for patients with diabetes because they could potentially serve as an unlimited source of functional, glucose-responsive beta cells. Challenges exist in their generation including long term survival of grafts, safety of transplantation, and protection from the immune response. This review focuses on the progress made in islet allo- and auto transplantation and how these advances may be extrapolated to the sBC context.

Human Pluripotent Stem Cells to Model Islet Defects in Diabetes

Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.

Engineering precision therapies: lessons and motivations from the clinic

In the past decade, gene- and cell-based therapies have been at the forefront of the biomedical revolution. Synthetic biology, the engineering discipline of building sophisticated 'genetic software' to enable precise regulation of gene activities in living cells, has been a decisive success factor of these new therapies. Here, we discuss the core technologies and treatment strategies that have already gained approval for therapeutic applications in humans. We also review promising preclinical work that could either enhance the efficacy of existing treatment strategies or pave the way for new precision medicines to treat currently intractable human conditions.

Developmentally-Inspired Biomimetic Culture Models to Produce Functional Islet-Like Cells From Pluripotent Precursors

Insulin-producing beta cells sourced from pluripotent stem cells hold great potential as a virtually unlimited cell source to treat diabetes. Directed pancreatic differentiation protocols aim to mimic various stimuli present during embryonic development through sequential changes of in vitro culture conditions. This is commonly accomplished by the timed addition of soluble signaling factors, in conjunction with cell-handling steps such as the formation of 3D cell aggregates. Interestingly, when stem cells at the pancreatic progenitor stage are transplanted, they form functional insulin-producing cells, suggesting that in vivo microenvironmental cues promote beta cell specification. Among these cues, biophysical stimuli have only recently emerged in the context of optimizing pancreatic differentiation protocols. This review focuses on studies of cell–microenvironment interactions and their impact on differentiating pancreatic cells when considering cell signaling, cell–cell and cell–ECM interactions. We highlight the development of in vitro cell culture models that allow systematic studies of pancreatic cell mechanobiology in response to extracellular matrix proteins, biomechanical effects, soluble factor modulation of biomechanics, substrate stiffness, fluid flow and topography. Finally, we explore how these new mechanical insights could lead to novel pancreatic differentiation protocols that improve efficiency, maturity, and throughput.

In Vivo Differentiation of Stem Cell-derived Human Pancreatic Progenitors to Treat Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that results from the loss of the pancreatic β-cells. The autoimmune destruction of the β-cells causes the loss of insulin production from the islets of the pancreas, resulting in the loss of blood glucose regulation. This loss of regulation, if not treated, can lead to a plethora of long-term complications in patients. Subsequently, T1DM patients rely on the administration of exogenous insulin sources to maintain their blood glucose levels. In this review, we summarize the history of T1DM therapy and current treatment options. Although treatments for T1DM have progressed substantially, none of the available treatment options allow the patient to live autonomously. Therefore, the challenge to develop a therapy that will fully reverse the disease still remains. A promising field of T1DM therapies is cell replacement therapies derived from human pluripotent stem cells. Here, we specifically review studies that employ stem-cell derived pancreatic progenitors transplanted for in vivo differentiation/maturation and discuss, in detail, the complications that arise post transplantation, including heterogeneity, graft immaturity, and host foreign bodyresponse. We also discuss efforts to induce human stem cell-derived mature β-cells in vitro and compare strategies regarding transplantation of pancreatic progenitors versus mature β-cells cells. Finally, we review key approaches that address critical limitations of in vivo progenitor differentiation including vascularization, oxygenation, and transplant location. The field of islet replacement therapy has made tremendous progress in the last two decades. If the strengths and limitations of the field continue to be identified and addressed, future studies will lead to an ideal treatment for T1DM. Graphical abstract.

Insulin-Deficient Diabetic Condition Upregulates the Insulin-Secreting Capacity of Human Induced Pluripotent Stem Cell-Derived Pancreatic Endocrine Progenitor Cells After Implantation in Mice

The host environment is a crucial factor for considering the transplant of stem cell-derived immature pancreatic cells in patients with type 1 diabetes. Here, we investigated the effect of insulin (INS)-deficient diabetes on the fate of immature pancreatic endocrine cell grafts and the underlying mechanisms. Human induced pluripotent stem cell-derived pancreatic endocrine progenitor cells (EPCs), which contained a high proportion of chromogranin A⁺ NK6 homeobox 1⁺ cells and very few INS⁺ cells, were used. When the EPCs were implanted under the kidney capsule in immunodeficient mice, INS-deficient diabetes accelerated increase in plasma human C-peptide, a marker of graft-derived INS secretion. The acceleration was suppressed by INS infusion but not affected by partial attenuation of hyperglycemia by dapagliflozin, an INS-independent glucose-lowering agent. Immunohistochemical analyses indicated that the grafts from diabetic mice contained more endocrine cells including proliferative INS-producing cells compared with that from nondiabetic mice, despite no difference in whole graft mass between the two groups. These data suggest that INS-deficient diabetes upregulates the INS-secreting capacity of EPC grafts by increasing the number of endocrine cells including INS-producing cells without changing the graft mass. These findings provide useful insights into postoperative diabetic care for cell therapy using stem cell-derived pancreatic cells.

Stem Cell Therapy for Diabetes: Beta Cells versus Pancreatic Progenitors

Diabetes mellitus (DM) is one of the most prevalent metabolic disorders. In order to replace the function of the destroyed pancreatic beta cells in diabetes, islet transplantation is the most widely practiced treatment. However, it has several limitations. As an alternative approach, human pluripotent stem cells (hPSCs) can provide an unlimited source of pancreatic cells that have the ability to secrete insulin in response to a high blood glucose level. However, the determination of the appropriate pancreatic lineage candidate for the purpose of cell therapy for the treatment of diabetes is still debated. While hPSC-derived beta cells are perceived as the ultimate candidate, their efficiency needs further improvement in order to obtain a sufficient number of glucose responsive beta cells for transplantation therapy. On the other hand, hPSC-derived pancreatic progenitors can be efficiently generated in vitro and can further mature into glucose responsive beta cells in vivo after transplantation. Herein, we discuss the advantages and predicted challenges associated with the use of each of the two pancreatic lineage products for diabetes cell therapy. Furthermore, we address the co-generation of functionally relevant islet cell subpopulations and structural properties contributing to the glucose responsiveness of beta cells, as well as the available encapsulation technology for these cells.

Engineering Strategies to Improve Islet Transplantation for Type 1 Diabetes Therapy

Type 1 diabetes is an autoimmune disease in which the immune system attacks insulin-producing beta cells of pancreatic islets. Type 1 diabetes can be treated with islet transplantation; however, patients must be administered immunosuppressants to prevent immune rejection of the transplanted islets if they are not autologous or not engineered with immune protection/isolation. To overcome biological barriers of islet transplantation, encapsulation strategies have been developed and robustly investigated. While islet encapsulation can prevent the need for immunosuppressants, these approaches have not shown much success in clinical trials due to a lack of long-term insulin production. Multiple engineering strategies have been used to improve encapsulation and post-transplantation islet survival. In addition, more efficient islet cryopreservation methods have been designed to facilitate the scaling-up of islet transplantation. Other islet sources have been identified including porcine islets and stem cell-derived islet-like aggregates. Overall, islet-laden capsule transplantation has greatly improved over the past 30 years and is moving towards becoming a clinically feasible treatment for type 1 diabetes.

Stem Cell Therapies for Treating Diabetes: Progress and Remaining Challenges

Restoration of insulin independence and normoglycemia has been the overarching goal in diabetes research and therapy. While whole-organ and islet transplantation have become gold-standard procedures in achieving glucose control in diabetic patients, the profound lack of suitable donor tissues severely hampers the broad application of these therapies. Here, we describe current efforts aimed at generating a sustainable source of functional human stem cell-derived insulin-producing islet cells for cell transplantation and present state-of-the-art efforts to protect such cells via immune modulation and encapsulation strategies.

Cell Mass Increase Associated with Formation of Glucose-Controlling β-Cell Mass in Device-Encapsulated Implants of hiPS-Derived Pancreatic Endoderm

Device-encapsulated human stem cell-derived pancreatic endoderm (PE) can generate functional β-cell implants in the subcutis of mice, which has led to the start of clinical studies in type 1 diabetes. Assessment of the formed functional β-cell mass (FBM) and its correlation with in vivo metabolic markers can guide clinical translation. We recently reported ex vivo characteristics of device-encapsulated human embryonic stem cell-derived (hES)-PE implants in mice that had established a metabolically adequate FBM during 50-week follow-up. Cell suspensions from retrieved implants indicated a correlation with the number of formed β cells and their maturation to a functional state comparable to human pancreatic β cells. Variability in metabolic outcome was attributed to differences in number of PE-generated β cells. This variability hinders studies on processes involved in FBM-formation. This study reports modifications that reduce variability. It is undertaken with device-encapsulated human induced pluripotent stem cell-derived-PE subcutaneously implanted in mice. Cell mass of each cell type was determined on intact tissue inside the device to obtain more precise data than following isolation and dispersion. Implants in a preformed pouch generated a glucose-controlling β-cell mass within 20 weeks in over 60% of recipients versus less than 20% in the absence of a pouch, whether the same or threefold higher cell dose had been inserted. In situ analysis of implants indicated a role for pancreatic progenitor cell expansion and endocrine differentiation in achieving the size of β- and α-cell mass that correlated with in vivo markers of metabolic control. Stem Cells Translational Medicine 2019;8:1296&1305.

The intraperitoneal space is more favorable than the subcutaneous one for transplanting alginate fiber containing iPS-derived islet-like cells

Introduction

Although immunosuppressants are required for current islet transplantation for type 1 diabetic patients, many papers have already reported encapsulation devices for islets to avoid immunological attack. The aim of this study is to determine the optimal number of cells and optimal transplantation site for human iPS-derived islet-like cells encapsulated in alginate fiber using diabetic model mice.

Methods

We used a suspension culture system for inducing islet-like cells from human iPS cells throughout the islet differentiation process. Islet-like spheroids were encapsulated in the alginate fiber, and cell transplantation experiments were performed with STZ-induced diabetic NOD/SCID mice. We compared the efficacy of transplanted cells between intraperitoneal and subcutaneous administration of alginate fibers by measuring blood glucose and human C-peptide levels serially in mice. Grafts were analyzed histologically, and gene expression in pancreatic β cells was also compared.

Results

We demonstrated the reversal of hyperglycemia in diabetic model mice after intraperitoneal administration of these fibers, but not with subcutaneous ones. Intraperitoneal fibers were easily retrieved without any adhesion. Although we detected human c-peptide in mice plasma after subcutaneous administration of these fibers, these fibers became encased by fibrous tissue.

Conclusions

These results suggest that the intraperitoneal space is favorable for islet-like cells derived from human iPS cells when encapsulated in alginate fiber.

Therapies for Type 1 Diabetes: Current Scenario and Future Perspectives

Type 1 diabetes (T1D) is caused by autoimmune destruction of insulin-producing β cells located in the endocrine pancreas in areas known as islets of Langerhans. The current standard-of-care for T1D is exogenous insulin replacement therapy. Recent developments in this field include the hybrid closed-loop system for regulated insulin delivery and long-acting insulins. Clinical studies on prediction and prevention of diabetes-associated complications have demonstrated the importance of early treatment and glucose control for reducing the risk of developing diabetic complications. Transplantation of primary islets offers an effective approach for treating patients with T1D. However, this strategy is hampered by challenges such as the limited availability of islets, extensive death of islet cells, and poor vascular engraftment of islets post-transplantation. Accordingly, there are considerable efforts currently underway for enhancing islet transplantation efficiency by harnessing the beneficial actions of stem cells. This review will provide an overview of currently available therapeutic options for T1D, and discuss the growing evidence that supports the use of stem cell approaches to enhance therapeutic outcomes.

Macroencapsulated Human iPSC-Derived Pancreatic Progenitors Protect against STZ-Induced Hyperglycemia in Mice

In type 1 diabetes, a renewable source of human pancreatic β cells, in particular from human induced pluripotent stem cell (hiPSC) origin, would greatly benefit cell therapy. Earlier work showed that pancreatic progenitors differentiated from human embryonic stem cells in vitro can further mature to become glucose responsive following macroencapsulation and transplantation in mice. Here we took a similar approach optimizing the generation of pancreatic progenitors from hiPSCs. This work demonstrates that hiPSCs differentiated to pancreatic endoderm in vitro can be efficiently and robustly generated under large-scale conditions. The hiPSC-derived pancreatic endoderm cells (HiPECs) can further differentiate into glucose-responsive islet-like cells following macroencapsulation and in vivo implantation. The HiPECs can protect mice from streptozotocin-induced hyperglycemia and maintain normal glucose homeostasis and equilibrated plasma glucose concentrations at levels similar to the human set point. These results further validate the potential use of hiPSC-derived islet cells for application in clinical settings.

Navigating Two Roads to Glucose Normalization in Diabetes: Automated Insulin Delivery Devices and Cell Therapy

Incredible strides have been made since the discovery of insulin almost 100 years ago. Insulin formulations have improved dramatically, glucose levels can be measured continuously, and recently first-generation biomechanical "artificial pancreas" systems have been approved by regulators around the globe. However, still only a small fraction of patients with diabetes achieve glycemic goals. Replacement of insulin-producing cells via transplantation shows significant promise, but is limited in application due to supply constraints (cadaver-based) and the need for chronic immunosuppression. Over the past decade, significant progress has been made to address these barriers to widespread implementation of a cell therapy. Can glucose levels in people with diabetes be normalized with artificial pancreas systems or via cell replacement approaches? Here we review the road ahead, including the challenges and opportunities of both approaches.

Paving the way for successful islet encapsulation

Type 1 diabetes mellitus (T1DM) is a disorder that decimates pancreatic β-cells which produce insulin. Direct pancreatic islet transplantation cannot serve as a widespread therapeutic modality owing to the need for lifelong immunosuppression and donor shortage. Therefore, several encapsulation techniques have been developed to enclose the islets in semipermeable vehicles that will allow oxygen and nutrient input as well as insulin, other metabolites and waste output, while accomplishing immunoisolation. Although encapsulation technology continues to face significant obstacles, recent advances in material science, stem cell biology and immunology potentially serve as pathways to success. This review summarizes the accomplishments of the past 5 years.

Oxygenation strategies for encapsulated islet and beta cell transplants

Human allogeneic islet transplantation (ITx) is emerging as a promising treatment option for qualified patients with type 1 diabetes. However, widespread clinical application of allogeneic ITx is hindered by two critical barriers: the need for systemic immunosuppression and the limited supply of human islet tissue. Biocompatible, retrievable immunoisolation devices containing glucose-responsive insulin-secreting tissue may address both critical barriers by enabling the more effective and efficient use of allogeneic islets without immunosuppression in the near-term, and ultimately the use of a cell source with a virtually unlimited supply, such as human stem cell-derived β-cells or xenogeneic (porcine) islets with minimal or no immunosuppression. However, even though encapsulation methods have been developed and immunoprotection has been successfully tested in small and large animal models and to a limited extent in proof-of-concept clinical studies, the effective use of encapsulation approaches to convincingly and consistently treat diabetes in humans has yet to be demonstrated. There is increasing consensus that inadequate oxygen supply is a major factor limiting their clinical translation and routine implementation. Poor oxygenation negatively affects cell viability and β-cell function, and the problem is exacerbated with the high-density seeding required for reasonably-sized clinical encapsulation devices. Approaches for enhanced oxygen delivery to encapsulated tissues in implantable devices are therefore being actively developed and tested. This review summarizes fundamental aspects of islet microarchitecture and β-cell physiology as well as encapsulation approaches highlighting the need for adequate oxygenation; it also evaluates existing and emerging approaches for enhanced oxygen delivery to encapsulation devices, particularly with the advent of β-cell sources from stem cells that may enable the large-scale application of this approach.

Increase Functional β-Cell Mass in Subcutaneous Alginate Capsules With Porcine Prenatal Islet Cells but Loss With Human Adult Islet Cells

Alginate (Alg)-encapsulated porcine islet cell grafts are developed to overcome limitations of human islet transplantation. They can generate functional implants in animals when prepared from fetal, perinatal, and adult pancreases. Implants have not yet been examined for efficacy to establish sustained, metabolically adequate functional β-cell mass (FBM) in comparison with human islet cells. This study in immune-compromised mice demonstrates that subcutaneous implants of Alg-encapsulated porcine prenatal islet cells with 4 × 10⁵ β-cells form, over 10 weeks, a FBM that results in glucose-induced plasma C-peptide >2 ng/mL and metabolic control over the following 10 weeks, with higher efficiency than nonencapsulated, while failing in peritoneum. This intracapsular FBM formation involves β-cell replication, increasing number fourfold, and maturation toward human adult β-cells. Subcutaneous Alg-encapsulated human islet cells with similar β-cell number establish implants with plasma C-peptide >2 ng/mL for the first 10 weeks, with nonencapsulated cells failing; their β-cells do not replicate but progressively die (>70%), explaining C-peptide decline and insufficient metabolic control. An Alg matrix thus helps establish β-cell functions in subcutis. It allows formation of sustained metabolically adequate FBM by immature porcine β-cells with proliferative activity but not by human adult islet cells. These findings define conditions for evaluating its immune-protecting properties.

Pluripotent Stem Cell-Derived Pancreatic Progenitors and β-Like Cells for Type 1 Diabetes Treatment

In this review, we focus on the processes guiding human pancreas development and provide an update on methods to efficiently generate pancreatic progenitors (PPs) and β-like cells in vitro from human pluripotent stem cells (hPSCs). Furthermore, we assess the strengths and weaknesses of using PPs and β-like cell for cell replacement therapy for the treatment of Type 1 diabetes with respect to cell manufacturing, engrafting, functionality, and safety. Finally, we discuss the identification and use of specific cell surface markers to generate safer populations of PPs for clinical translation and to study the development of PPs in vivo and in vitro.

Implications of human induced pluripotent stem cells in metabolic disorders: from drug discovery toward precision medicine

Human induced pluripotent stem cells (hiPSCs) enable in vitro high-throughput pharmacological screening assays of diseased tissue. Together with recent genome-wide association studies (GWAS), hiPSCs enable the identification of key mutations for the development of effective treatments based on precise drugs. In concert with CRISPR/Cas9 systems, hiPSC technology can reveal therapeutic targets in metabolic disorders. The ex vivo CRISPR correction of autologous patient-derived hiPSCs has led to the development of replacement cell therapies, providing better patient prognoses.

Transplantation of Macroencapsulated Insulin-Producing Cells

PURPOSE OF REVIEW

There is considerable interest in using macroencapsulation devices as a delivery strategy for transplanting insulin-producing cells. This review aims to summarize recent advances, to highlight remaining challenges, and to provide recommendations for the field.

RECENT FINDINGS

A variety of new device designs have been reported to improve biocompatibility and to provide protection for islet/beta cells from immune destruction while allowing continuous secretion of insulin. Some of these new approaches are in clinical trials, but more research is needed to determine how sufficient beta-cell mass can be transplanted in a clinically applicable device size, and that insulin is secreted with kinetics that will safely provide adequate controls of glucose levels. Macroencapsulation is a potential solution to transplant beta cells without immunosuppression in diabetes patients, but new strategies must be developed to show that this approach is feasible.

Sex differences underlying pancreatic islet biology and its dysfunction

Background

The sex of an individual affects glucose homeostasis and the pathophysiology, incidence, and prevalence of diabetes as well as the response to therapy.

Scope of the review

This review focuses on clinical and experimental sex differences in islet cell biology and dysfunction during development and in adulthood in human and animal models. We discuss sex differences in β-cell and α-cell function, heterogeneity, and dysfunction. We cover sex differences in communication between gonads and islets and islet-cell immune interactions. Finally, we discuss sex differences in β-cell programming by nutrition and other environmental factors during pregnancy.

Major conclusions

Important sex differences exist in islet cell function and susceptibility to failure. These differences represent sex-related biological factors that can be harnessed for gender-based prevention of and therapy for diabetes.