Identification of unique cell type responses in pancreatic islets to stress.

Diabetes involves the death or dysfunction of pancreatic ß-cells. Analysis of bulk sequencing from human samples and studies using in vitro and in vivo models suggest that endoplasmic reticulum and inflammatory signaling play an important role in diabetes progression. To better characterize cell type-specific stress response, we perform multiplexed single-cell RNA sequencing to define the transcriptional signature of primary human islet cells exposed to endoplasmic reticulum and inflammatory stress. Through comprehensive pair-wise analysis of stress responses across pancreatic endocrine and exocrine cell types, we define changes in gene expression for each cell type under different diabetes-associated stressors. We find that ß-, α-, and ductal cells have the greatest transcriptional response. We utilize stem cell-derived islets to study islet health through the candidate gene CIB1, which was upregulated under stress in primary human islets. Our findings provide insights into cell type-specific responses to diabetes-associated stress and establish a resource to identify targets for diabetes therapeutics.

Differential Function and Maturation of Human Stem Cell-Derived Islets After Transplantation.

Insulin-producing stem cell-derived islets (SC-islets) provide a virtually unlimited cell source for diabetes cell replacement therapy. While SC-islets are less functional when first differentiated in vitro compared to isolated cadaveric islets, transplantation into mice has been shown to increase their maturation. To understand the effects of transplantation on maturation and function of SC-islets, we examined the effects of cell dose, transplantation strategy, and diabetic state in immunocompromised mice. Transplantation of 2 and 5, but not 0.75 million SC-islet cells underneath the kidney capsule successfully reversed diabetes in mice with pre-existing diabetes. SQ and intramuscular injections failed to reverse diabetes at all doses and had undetectable expression of maturation markers, such as MAFA and FAM159B. Furthermore, SC-islets had similar function and maturation marker expression regardless of diabetic state. Our results illustrate that transplantation parameters are linked to SC-islet function and maturation, providing ideal mouse models for preclinical diabetes SC therapy research.

Multidimensional analysis and therapeutic development using patient iPSC-derived disease models of Wolfram syndrome.

Wolfram syndrome is a rare genetic disorder largely caused by pathogenic variants in the WFS1 gene and manifested by diabetes mellitus, optic nerve atrophy, and progressive neurodegeneration. Recent genetic and clinical findings have revealed Wolfram syndrome as a spectrum disorder. Therefore, a genotype-phenotype correlation analysis is needed for diagnosis and therapeutic development. Here, we focus on the WFS1 c.1672C>T, p.R558C variant, which is highly prevalent in the Ashkenazi Jewish population. Clinical investigation indicated that patients carrying the homozygous WFS1 c.1672C>T, p.R558C variant showed mild forms of Wolfram syndrome phenotypes. Expression of WFS1 p.R558C was more stable compared with the other known recessive pathogenic variants associated with Wolfram syndrome. Human induced pluripotent stem cell-derived (iPSC-derived) islets (SC-islets) homozygous for WFS1 c.1672C>T variant recapitulated genotype-related Wolfram syndrome phenotypes. Enhancing residual WFS1 function through a combination treatment of chemical chaperones mitigated detrimental effects caused by the WFS1 c.1672C>T, p.R558C variant and increased insulin secretion in SC-islets. Thus, the WFS1 c.1672C>T, p.R558C variant causes a mild form of Wolfram syndrome phenotypes, which can be remitted with a combination treatment of chemical chaperones. We demonstrate that our patient iPSC-derived disease model provides a valuable platform for further genotype-phenotype analysis and therapeutic development for Wolfram syndrome.

Applications of iPSC-derived beta cells from patients with diabetes.

Improved stem cell-derived pancreatic islet (SC-islet) differentiation protocols robustly generate insulin-secreting ß 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 ß 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 ß 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-ß cells and progenitors, encompassing new conclusions involving cells from patients with diabetes and the therapeutic potential of iPSC-ß cells.

Generation of insulin-producing pancreatic ß cells from multiple human stem cell lines.

We detail a six-stage planar differentiation methodology for generating human pluripotent stem cell-derived pancreatic ß cells (SC-ß cells) that secrete high amounts of insulin in response to glucose stimulation. This protocol first induces definitive endoderm by treatment with Activin A and CHIR99021, then generates PDX1+/NKX6-1+ pancreatic progenitors through the timed application of keratinocyte growth factor, SANT1, TPPB, LDN193189 and retinoic acid. Endocrine induction and subsequent SC-ß-cell specification is achieved with a cocktail consisting of the cytoskeletal depolymerizing compound latrunculin A combined with XXI, T3, ALK5 inhibitor II, SANT1 and retinoic acid. The resulting SC-ß cells and other endocrine cell types can then be aggregated into islet-like clusters for analysis and transplantation. This differentiation methodology takes ~34 d to generate functional SC-ß cells, plus an additional 1-2 weeks for initial stem cell expansion and final cell assessment. This protocol builds upon a large body of previous work for generating ß-like cells. In this iteration, we have eliminated the need for 3D culture during endocrine induction, allowing for the generation of highly functional SC-ß cells to be done entirely on tissue culture polystyrene. This change simplifies the differentiation methodology, requiring only basic stem cell culture experience as well as familiarity with assessment techniques common in biology laboratories. In addition to expanding protocol accessibility and simplifying SC-ß-cell generation, we demonstrate that this planar methodology is amenable for differentiating SC-ß cells from a wide variety of cell lines from various sources, broadening its applicability.

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

Transplantation of stem cell-derived ß (SC-ß) 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-ß 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-ß 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.

Targeting the cytoskeleton to direct pancreatic differentiation of human pluripotent stem cells.

Generation of pancreatic ß cells from human pluripotent stem cells (hPSCs) holds promise as a cell replacement therapy for diabetes. In this study, we establish a link between the state of the actin cytoskeleton and the expression of pancreatic transcription factors that drive pancreatic lineage specification. Bulk and single-cell RNA sequencing demonstrated that different degrees of actin polymerization biased cells toward various endodermal lineages and that conditions favoring a polymerized cytoskeleton strongly inhibited neurogenin 3-induced endocrine differentiation. Using latrunculin A to depolymerize the cytoskeleton during endocrine induction, we developed a two-dimensional differentiation protocol for generating human pluripotent stem-cell-derived ß (SC-ß) cells with improved in vitro and in vivo function. SC-ß cells differentiated from four hPSC lines exhibited first- and second-phase dynamic glucose-stimulated insulin secretion. Transplantation of islet-sized aggregates of these cells rapidly reversed severe preexisting diabetes in mice at a rate close to that of human islets and maintained normoglycemia for at least 9 months.

Single-Cell Transcriptome Profiling Reveals ß Cell Maturation in Stem Cell-Derived Islets after Transplantation.

Human pluripotent stem cells differentiated to insulin-secreting ß cells (SC-ß cells) in islet organoids could provide an unlimited cell source for diabetes cell replacement therapy. However, current SC-ß cells generated in vitro are transcriptionally and functionally immature compared to native adult ß cells. Here, we use single-cell transcriptomic profiling to catalog changes that occur in transplanted SC-ß cells. We find that transplanted SC-ß cells exhibit drastic transcriptional changes and mature to more closely resemble adult ß cells. Insulin and IAPP protein secretions increase upon transplantation, along with expression of maturation genes lacking with differentiation in vitro, including INS, MAFA, CHGB, and G6PC2. Other differentiated cell types, such as SC-α and SC-enterochromaffin (SC-EC) cells, also exhibit large transcriptional changes. This study provides a comprehensive resource for understanding human islet cell maturation and provides important insights into maturation of SC-ß cells and other SC-islet cell types to enable future differentiation strategy improvements.

SIX2 Regulates Human ß Cell Differentiation from Stem Cells and Functional Maturation In Vitro.

Generation of insulin-secreting ß cells in vitro is a promising approach for diabetes cell therapy. Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) are differentiated to ß cells (SC-ß cells) and mature to undergo glucose-stimulated insulin secretion, but molecular regulation of this defining ß cell phenotype is unknown. Here, we show that maturation of SC-ß cells is regulated by the transcription factor SIX2. Knockdown (KD) or knockout (KO) of SIX2 in SC-ß cells drastically limits glucose-stimulated insulin secretion in both static and dynamic assays, along with the upstream processes of cytoplasmic calcium flux and mitochondrial respiration. Furthermore, SIX2 regulates the expression of genes associated with these key ß cell processes, and its expression is restricted to endocrine cells. Our results demonstrate that expression of SIX2 influences the generation of human SC-ß cells in vitro.

Gene-edited human stem cell-derived ß cells from a patient with monogenic diabetes reverse preexisting diabetes in mice.

Differentiation of insulin-producing pancreatic ß cells from induced pluripotent stem cells (iPSCs) derived from patients with diabetes promises to provide autologous cells for diabetes cell replacement therapy. However, current approaches produce patient iPSC-derived ß (SC-ß) cells with poor function in vitro and in vivo. Here, we used CRISPR-Cas9 to correct a diabetes-causing pathogenic variant in Wolfram syndrome 1 (WFS1) in iPSCs derived from a patient with Wolfram syndrome (WS). After differentiation to ß cells with our recent six-stage differentiation strategy, corrected WS SC-ß cells performed robust dynamic insulin secretion in vitro in response to glucose and reversed preexisting streptozocin-induced diabetes after transplantation into mice. Single-cell transcriptomics showed that corrected SC-ß cells displayed increased insulin and decreased expression of genes associated with endoplasmic reticulum stress. CRISPR-Cas9 correction of a diabetes-inducing gene variant thus allows for robust differentiation of autologous SC-ß cells that can reverse severe diabetes in an animal model.

Acquisition of Dynamic Function in Human Stem Cell-Derived ß Cells.

Recent advances in human pluripotent stem cell (hPSC) differentiation protocols have generated insulin-producing cells resembling pancreatic ß cells. While these stem cell-derived ß (SC-ß) cells are capable of undergoing glucose-stimulated insulin secretion (GSIS), insulin secretion per cell remains low compared with islets and cells lack dynamic insulin release. Herein, we report a differentiation strategy focused on modulating transforming growth factor ß (TGF-ß) signaling, controlling cellular cluster size, and using an enriched serum-free media to generate SC-ß cells that express ß cell markers and undergo GSIS with first- and second-phase dynamic insulin secretion. Transplantation of these cells into mice greatly improves glucose tolerance. These results reveal that specific time frames for inhibiting and permitting TGF-ß signaling are required during SC-ß cell differentiation to achieve dynamic function. The capacity of these cells to undergo GSIS with dynamic insulin release makes them a promising cell source for diabetes cellular therapy.