Maturation of human embryonic stem cell-derived pancreatic progenitors into functional islets capable of treating pre-existing diabetes in mice

Glucose Transporters Are Key Components of the Human Glucostat

Mouse models are extensively used in metabolic studies. However, inherent differences between the species, notably their blood glucose levels, hampered data translation into clinical settings. In this study, we confirmed GLUT1 to be the predominantly expressed glucose transporter in both adult and fetal human β-cells. In comparison, GLUT2 is detected in a small yet significant subpopulation of adult β-cells and is expressed to a greater extent in fetal β-cells. Notably, GLUT1/2 expression in INS+ cells from human stem cell-derived islet-like clusters (SC-islets) exhibited a closer resemblance to that observed in fetal islets. Transplantation of primary human islets or SC-islets, but not murine islets, lowered murine blood glucose to the human glycemic range, emphasizing the critical role of β-cells in establishing species-specific glycemia. We further demonstrate the functional requirements of GLUT1 and GLUT2 in glucose uptake and insulin secretion through chemically inhibiting GLUT1 in primary islets and SC-islets and genetically disrupting GLUT2 in SC-islets. Finally, we developed a mathematical model to predict changes in glucose uptake and insulin secretion as a function of GLUT1/2 expression. Collectively, our findings illustrate the crucial roles of GLUTs in human β-cells, and identify them as key components in establishing species-specific glycemic set points.

ARTICLE HIGHLIGHTS

Scalable Bioreactor-based Suspension Approach to Generate Stem Cell-derived Islets From Healthy Donor-derived iPSCs

BACKGROUND

Induced pluripotent stem cells (iPSCs) offer the potential to generate autologous iPSC-derived islets (iPSC islets), however, remain limited by scalability and product safety.

METHODS

Herein, we report stagewise characterization of cells generated following a bioreactor-based differentiation protocol. Cell characteristics were assessed using flow cytometry, quantitative reverse transcription polymerase chain reaction, patch clamping, functional assessment, and in vivo functional and immunohistochemistry evaluation. Protocol yield and costs are assessed to determine scalability.

RESULTS

Differentiation was capable of generating 90.4% PDX1+/NKX6.1+ pancreatic progenitors and 100% C-peptide+/NKX6.1+ iPSC islet cells. However, 82.1%, 49.6%, and 0.9% of the cells expressed SOX9 (duct), SLC18A1 (enterochromaffin cells), and CDX2 (gut cells), respectively. Explanted grafts contained mature monohormonal islet-like cells, however, CK19+ ductal tissues persist. Using this protocol, semi-planar differentiation using 150 mm plates achieved 5.72 × 104 cells/cm2 (total 8.3 × 106 cells), whereas complete suspension differentiation within 100 mL Vertical-Wheel bioreactors significantly increased cell yield to 1.1 × 106 cells/mL (total 105.0 × 106 cells), reducing costs by 88.8%.

CONCLUSIONS

This study offers a scalable suspension-based approach for iPSC islet differentiation within Vertical-Wheel bioreactors with thorough characterization of the ensuing product to enable future protocol comparison and evaluation of approaches for off-target cell elimination. Results suggest that bioreactor-based suspension differentiation protocols may facilitate scalability and clinical implementation of iPSC islet therapies.

Diabetes current and future translatable therapies

Diabetes is one of the major diseases and concerns of public health systems that affects over 200 million patients worldwide. It is estimated that 90% of these patients suffer from diabetes type 2, while 10% present diabetes type 1. This type of diabetes and certain types of diabetes type 2, are characterized by dysregulation of blood glycemic levels due to the total or partial depletion of insulin-secreting pancreatic β-cells. Different approaches have been proposed for long-term treatment of insulin-dependent patients; amongst them, cell-based approaches have been the subject of basic and clinical research since they allow blood glucose level sensing and in situ insulin secretion. The current gold standard for insulin-dependent patients is on-demand exogenous insulin application; cell-based therapies aim to remove this burden from the patient and caregivers. In recent years, protocols to isolate and implant pancreatic islets from diseased donors have been developed and tested in clinical trials. Nevertheless, the shortage of donors, along with the need of immunosuppressive companion therapies, have pushed researchers to focus their attention and efforts to overcome these disadvantages and develop alternative strategies. This review discusses current tested clinical approaches and future potential alternatives for diabetes type 1, and some diabetes type 2, insulin-dependent patients. Additionally, advantages and disadvantages of these discussed methods.

Ameliorating and refining islet organoids to illuminate treatment and pathogenesis of diabetes mellitus

Diabetes mellitus, a significant global public health challenge, severely impacts human health worldwide. The organoid, an innovative in vitro three-dimensional (3D) culture model, closely mimics tissues or organs in vivo. Insulin-secreting islet organoid, derived from stem cells induced in vitro with 3D structures, has emerged as a potential alternative for islet transplantation and as a possible disease model that mirrors the human body's in vivo environment, eliminating species difference. This technology has gained considerable attention for its potential in diabetes treatment. Despite advances, the process of stem cell differentiation into islet organoid and its cultivation demonstrates deficiencies, prompting ongoing efforts to develop more efficient differentiation protocols and 3D biomimetic materials. At present, the constructed islet organoid exhibit limitations in their composition, structure, and functionality when compared to natural islets. Consequently, further research is imperative to achieve a multi-tissue system composition and improved insulin secretion functionality in islet organoid, while addressing transplantation-related safety concerns, such as tumorigenicity, immune rejection, infection, and thrombosis. This review delves into the methodologies and strategies for constructing the islet organoid, its application in diabetes treatment, and the pivotal scientific challenges within organoid research, offering fresh perspectives for a deeper understanding of diabetes pathogenesis and the development of therapeutic interventions.

Remodeling ceramide homeostasis promotes functional maturation of human pluripotent stem cell-derived β cells

Human pluripotent stem cell-derived β cells (hPSC-β cells) show the potential to restore euglycemia. However, the immature functionality of hPSC-β cells has limited their efficacy in application. Here, by deciphering the continuous maturation process of hPSC-β cells post transplantation via single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq), we show that functional maturation of hPSC-β cells is an orderly multistep process during which cells sequentially undergo metabolic adaption, removal of negative regulators of cell function, and establishment of a more specialized transcriptome and epigenome. Importantly, remodeling lipid metabolism, especially downregulating the metabolic activity of ceramides, the central hub of sphingolipid metabolism, is critical for β cell maturation. Limiting intracellular accumulation of ceramides in hPSC-β cells remarkably enhanced their function, as indicated by improvements in insulin processing and glucose-stimulated insulin secretion. In summary, our findings provide insights into the maturation of human pancreatic β cells and highlight the importance of ceramide homeostasis in function acquisition.

Pancreatic islet transplantation: current advances and challenges

Diabetes is a prevalent chronic disease that traditionally requires severe reliance on medication for treatment. Oral medication and exogenous insulin can only temporarily maintain blood glucose levels and do not cure the disease. Most patients need life-long injections of exogenous insulin. In recent years, advances in islet transplantation have significantly advanced the treatment of diabetes, allowing patients to discontinue exogenous insulin and avoid complications.Long-term follow-up results from recent reports on islet transplantation suggest that they provide significant therapeutic benefit although patients still require immunotherapy, suggesting the importance of future transplantation strategies. Although organ shortage remains the primary obstacle for the development of islet transplantation, new sources of islet cells, such as stem cells and porcine islet cells, have been proposed, and are gradually being incorporated into clinical research. Further research on new transplantation sites, such as the subcutaneous space and mesenteric fat, may eventually replace the traditional portal vein intra-islet cell infusion. Additionally, the immunological rejection reaction in islet transplantation will be resolved through the combined application of immunosuppressant agents, islet encapsulation technology, and the most promising mesenchymal stem cells/regulatory T cell and islet cell combined transplantation cell therapy. This review summarizes the progress achieved in islet transplantation, and discusses the research progress and potential solutions to the challenges faced.

GLP-1 Analogue-Loaded Glucose-Responsive Nanoparticles as Allies of Stem Cell Therapies for the Treatment of Type I Diabetes

Type 1 diabetes (T1D) is characterized by insufficient insulin secretion due to β-cell loss. Despite exogenous insulin administration being a lifesaving treatment, many patients still experience severe glycemic lability. For these patients, a β-cell replacement strategy through pancreas or pancreatic islet transplantation is the most physiological approach. However, donors' scarcity and the need for lifelong immunosuppressive therapy pose some challenges. This study proposes an innovative biomimetic pancreas, comprising β- and α-cells differentiated from human induced pluripotent stem cells (hiPSCs) embedded in a biofunctional matrix with glucose-responsive nanoparticles (NPs) encapsulating a glucagon-like peptide 1 (GLP-1) analogue, which aims to enhance the glucose responsiveness of differentiated β-cells. Herein, glucose-sensitive pH-responsive NPs encapsulating exenatide or semaglutide showed an average size of 145 nm, with 40% association efficiency for exenatide-loaded NPs and 55% for semaglutide-loaded NPs. Both peptides maintained their secondary structure after in vitro release and showed a similar effect on INS-1E cells' insulin secretion. hiPSCs were differentiated into β- and α-cells, and insulin-positive cells were obtained (82%), despite low glucose responsiveness, as well as glucagon-positive cells (17.5%). The transplantation of the developed system in diabetic mice showed promising outcomes since there was an increase in the survival rate of those animals. Moreover, diabetic mice transplanted with cells and exenatide showed a decrease in their glucose levels. Overall, the biomimetic pancreas developed in this work showed improvements in diabetic mice survival rate, paving the way for new cellular therapies for T1D that explore the synergy of nanomedicines and stem cell-based approaches.

The efficiency of stem cell differentiation into functional beta cells for treating insulin-requiring diabetes: Recent advances and current challenges

In recent years, the potential of stem cells (SCs) to differentiate into various types of cells, including β-cells, has led to a significant boost in development. The efficiency of this differentiation process and the functionality of the cells post-transplantation are crucial factors for the success of stem cell therapy in diabetes. Herein, this article reviews the current advances and challenges faced by stem cell differentiation into functional β-cells for diabetes treatment. In vitro, researchers have sought to enhance the differentiation efficiency of functional β-cells by mimicking the normal pancreatic development process, using gene manipulation, pharmacological and culture conditions stimulation, three-dimensional (3D) and organoid culture, or sorting for functional β-cells based on mature islet cell markers. Furthermore, in vivo studies have also looked at suitable transplantation sites, the enhancement of the transplantation microenvironment, immune modulation, and vascular function reconstruction to improve the survival rate of functional β-cells, thereby enhancing the treatment of diabetes. Despite these advancements, developing stem cells to produce functional β-cells for efficacious diabetes treatment is a continuous research endeavor requiring significant multidisciplinary collaboration, for the stem-cell-derived beta cells to evolve into an effective cellular therapy.

Advances and challenges of the cell-based therapies among diabetic patients

Diabetes mellitus is a significant global public health challenge, with a rising prevalence and associated morbidity and mortality. Cell therapy has evolved over time and holds great potential in diabetes treatment. In the present review, we discussed the recent progresses in cell-based therapies for diabetes that provides an overview of islet and stem cell transplantation technologies used in clinical settings, highlighting their strengths and limitations. We also discussed immunomodulatory strategies employed in cell therapies. Therefore, this review highlights key progresses that pave the way to design transformative treatments to improve the life quality among diabetic patients.

IAPP Marks Mono-hormonal Stem-cell Derived β Cells that Maintain Stable Insulin Production in vitro and in vivo

Islet transplantation for treatment of diabetes is limited by availability of donor islets and requirements for immunosuppression. Stem cell-derived islets might circumvent these issues. SC-islets effectively control glucose metabolism post transplantation, but do not yet achieve full function in vitro with current published differentiation protocols. We aimed to identify markers of mature subpopulations of SC-β cells by studying transcriptional changes associated with in vivo maturation of SC-β cells using RNA-seq and co-expression network analysis. The β cell-specific hormone islet amyloid polypeptide (IAPP) emerged as the top candidate to be such a marker. IAPP+ cells had more mature β cell gene expression and higher cellular insulin content than IAPP- cells in vitro. IAPP+ INS+ cells were more stable in long-term culture than IAPP- INS+ cells and retained insulin expression after transplantation into mice. Finally, we conducted a small molecule screen to identify compounds that enhance IAPP expression. Aconitine up-regulated IAPP and could help to optimize differentiation protocols.

LINC MIR503HG Controls SC-β Cell Differentiation and Insulin Production by Targeting CDH1 and HES1

Stem cell-derived pancreatic progenitors (SC-PPs), as an unlimited source of SC-derived β (SC-β) cells, offers a robust tool for diabetes treatment in stem cell-based transplantation, disease modeling, and drug screening. Whereas, PDX1+/NKX6.1+ PPs enhances the subsequent endocrine lineage specification and gives rise to glucose-responsive SC-β cells in vivo and in vitro. To identify the regulators that promote induction efficiency and cellular function maturation, single-cell RNA-sequencing is performed to decipher the transcriptional landscape during PPs differentiation. The comprehensive evaluation of functionality demonstrated that manipulating LINC MIR503HG using CRISPR in PP cell fate decision can improve insulin synthesis and secretion in mature SC-β cells, without effects on liver lineage specification. Importantly, transplantation of MIR503HG-/- SC-β cells in recipients significantly restored blood glucose homeostasis, accompanied by serum C-peptide release and an increase in body weight. Mechanistically, by releasing CtBP1 occupying the CDH1 and HES1 promoters, the decrease in MIR503HG expression levels provided an excellent extracellular niche and appropriate Notch signaling activation for PPs following differentiation. Furthermore, this exhibited higher crucial transcription factors and mature epithelial markers in CDH1High expressed clusters. Altogether, these findings highlighted MIR503HG as an essential and exclusive PP cell fate specification regulator with promising therapeutic potential for patients with diabetes.

Clinical translation of pluripotent stem cell-based therapies: successes and challenges

The translational stem cell research field has progressed immensely in the past decade. Development and refinement of differentiation protocols now allows the generation of a range of cell types, such as pancreatic β-cells and dopaminergic neurons, from human pluripotent stem cells (hPSCs) in an efficient and good manufacturing practice-compliant fashion. This has led to the initiation of several clinical trials using hPSC-derived cells to replace lost or dysfunctional cells, demonstrating evidence of both safety and efficacy. Here, we highlight successes from some of the hPSC-based trials reporting early signs of efficacy and discuss common challenges in clinical translation of cell therapies.

Bioengineering and vascularization strategies for islet organoids: advancing toward diabetes therapy

Diabetes presents a pressing healthcare crisis, necessitating innovative solutions. Organoid technologies have rapidly advanced, leading to the emergence of bioengineering islet organoids as an unlimited source of insulin-producing cells for treating insulin-dependent diabetes. This advancement surpasses the need for cadaveric islet transplantation. However, clinical translation of this approach faces two major limitations: immature endocrine function and the absence of a perfusable vasculature compared to primary human islets. In this review, we summarize the latest developments in bioengineering functional islet organoids in vitro and promoting vascularization of organoid grafts before and after transplantation. We highlight the crucial roles of the vasculature in ensuring long-term survival, maturation, and functionality of islet organoids. Additionally, we discuss key considerations that must be addressed before clinical translation of islet organoid-based therapy, including functional immaturity, undesired heterogeneity, and potential tumorigenic risks.

Current status of stem cell therapy for type 1 diabetes: a critique and a prospective consideration

Over the past decade, there had been progress in the development of cell therapy for insulin-dependent diabetes. Nevertheless, important hurdles that need to be overcome still remain. Protocols for the differentiation of pluripotent stem cells into pancreatic progenitors or fully differentiated β-cells have been developed. The resulting insulin-producing cells can control chemically induced diabetes in rodents and were the subject of several clinical trials. However, these cells are immunogenic and possibly teratogenic for their transplantation, and an immunoisolation device and/or immunosuppression is needed. A growing number of studies have utilized genetic manipulations to produce immune evasive cells. Evidence must be provided that in addition to the expected benefit, gene manipulations should not lead to any unforeseen complications. Mesenchymal stem/stromal cells (MSCs) can provide a viable alternative. MSCs are widely available from many tissues. They can form insulin-producing cells by directed differentiation. Experimentally, evidence has shown that the transplantation of allogenic insulin-producing cells derived from MSCs is associated with a muted allogeneic response that does not interfere with their functionality. This can be explained by the immunomodulatory functions of the MSC subpopulation that did not differentiate into insulin-producing cells. Recently, exosomes derived from naive MSCs have been used in the experimental domain to treat diabetes in rodents with varying degrees of success. Several mechanisms for their beneficial functions were proposed including a reduction in insulin resistance, the promotion of autophagy, and an increase in the T regulatory population. However, euglycemia was not achieved in any of these experiments. We suggest that exosomes derived from β-cells or insulin-producing cells (educated) can provide a better therapeutic effect than those derived from undifferentiated cells.

Thyroid Hormone Levels Correlate With the Maturation of Implanted Pancreatic Endoderm Cells in Patients With Type 1 Diabetes

BACKGROUND

Macroencapsulated pancreatic endoderm cells (PECs) can reverse diabetes in rodents and preclinical studies revealed that thyroid hormones in vitro and in vivo bias PECs to differentiate into insulin-producing cells. In an ongoing clinical trial, PECs implanted in macroencapsulation devices into patients with type 1 diabetes were safe but yielded heterogeneous outcomes. Though most patients developed meal responsive C-peptide, levels were heterogeneous and explanted grafts had variable numbers of surviving cells with variable distribution of endocrine cells.

METHODS

We measured circulating triiodothyronine and thyroxine levels in all patients treated at 1 of the 7 sites of the ongoing clinical trial and determined if thyroid hormone levels were associated with the C-peptide or glucagon levels and cell fate of implanted PECs.

RESULTS

Both triiodothyronine and thyroxine levels were significantly associated with the proportion of cells that adopted an insulin-producing fate with a mature phenotype. Thyroid hormone levels were inversely correlated to circulating glucagon levels after implantation, suggesting that thyroid hormones lead PECs to favor an insulin-producing fate over a glucagon-producing fate. In mice, hyperthyroidism led to more rapid maturation of PECs into insulin-producing cells similar in phenotype to PECs in euthyroid mice.

CONCLUSION

These data highlight the relevance of thyroid hormones in the context of PEC therapy in patients with type 1 diabetes and suggest that a thyroid hormone adjuvant therapy may optimize cell outcomes in some PEC recipients.

Metabolic switching, growth kinetics and cell yields in the scalable manufacture of stem cell-derived insulin-producing cells

BACKGROUND

Diabetes is a disease affecting over 500 million people globally due to insulin insufficiency or insensitivity. For individuals with type 1 diabetes, pancreatic islet transplantation can help regulate their blood glucose levels. However, the scarcity of cadaveric donor islets limits the number of people that could receive this therapy. To address this issue, human pluripotent stem cells offer a potentially unlimited source for generating insulin-producing cells through directed differentiation. Several protocols have been developed to make stem cell-derived insulin-producing cells. However, there is a lack of knowledge regarding the bioprocess parameters associated with these differentiation protocols and how they can be utilized to increase the cell yield.

METHODS

We investigated various bioprocess parameters and quality target product profiles that may influence the differentiation pipeline using a seven-stage protocol in a scalable manner with CellSTACKs and vertical wheel bioreactors (PBS-Minis).

RESULTS

Cells maintained > 80% viability through all stages of differentiation and appropriately expressed stage-specific markers. During the initial four stages leading up to the development of pancreatic progenitors, there was an increase in cell numbers. Following pancreatic progenitor stage, there was a gradual decrease in the percentage of proliferative cells, as determined by Ki67 positivity, and a significant loss of cells during the period of endocrine differentiation. By minimizing the occurrence of aggregate fusion, we were able to enhance cell yield during the later stages of differentiation. We suggest that glucose utilization and lactate production are cell quality attributes that should be considered during the characterization of insulin-producing cells derived from stem cells. Our findings also revealed a gradual metabolic shift from glycolysis, during the initial four stages of pancreatic progenitor formation, to oxidative phosphorylation later on during endocrine differentiation. Furthermore, the resulting insulin-producing cells exhibited a response to several secretagogues, including high glucose.

CONCLUSION

This study demonstrates process parameters such as glucose consumption and lactate production rates that may be used to facilitate the scalable manufacture of stem cell-derived insulin-producing cells.

Neural Stem Cell-based Regenerative Therapy: A New Approach to Diabetes Treatment

Diabetes mellitus (DM) is the most common metabolic disorder that occurs due to the loss, or impaired function of insulin-secreting pancreatic beta cells, which are of two types - type 1 (T1D) and type 2 (T2D). To cure DM, the replacement of the destroyed pancreatic beta cells of islet of Langerhans is the most widely practiced treatment. For this, isolating neuronal stem cells and cultivating them as a source of renewable beta cells is a significant breakthrough in medicine. The functions, growth, and gene expression of insulin-producing pancreatic beta cells and neurons are very similar in many ways. A diabetic patient's neural stem cells (obtained from the hippocampus and olfactory bulb) can be used as a replacement source of beta cells for regenerative therapy to treat diabetes. The same protocol used to create functional neurons from progenitor cells can be used to create beta cells. Recent research suggests that replacing lost pancreatic beta cells with autologous transplantation of insulin-producing neural progenitor cells may be a perfect therapeutic strategy for diabetes, allowing for a safe and normal restoration of function and a reduction in potential risks and a long-term cure.

Therapeutic approaches for Type 1 Diabetes: Promising cell-based approaches to achieve ultimate success

Type 1 Diabetes mellitus (T1DM) is a chronic metabolic disorder characterized by pancreatic β-cells destruction. Despite substantial advances in T1DM treatment, lifelong exogenous insulin administration is the mainstay of treatments, and constant control of glucose levels is still a challenge. Endogenous insulin production by replacing insulin-producing cells is an alternative, but the lack of suitable donors is accounted as one of the main obstacles to its widespread application. The research and trials overview demonstrates that endogenous production of insulin has started to go beyond the deceased-derived to stem cells-derived insulin-producing cells. Several protocols have been developed over the past couple of years for generating insulin-producing cells (IPCs) from various stem cell types and reprogramming fully differentiated cells. A straightforward and quick method for achieving this goal is to investigate and apply the β-cell specific transcription factors as a direct strategy for IPCs generation. In this review, we emphasize the significance of transcription factors in IPCs development from different non-beta cell sources, and pertinent research underlies the marked progress in the methods for generating insulin-producing cells and application for Type 1 Diabetes treatment.

Analysis of the effects of bench-scale cell culture platforms and inoculum cell concentrations on PSC aggregate formation and culture

Introduction: Human pluripotent stem cells (hPSCs) provide many opportunities for application in regenerative medicine due to their ability to differentiate into cells from all three germ layers, proliferate indefinitely, and replace damaged or dysfunctional cells. However, such cell replacement therapies require the economical generation of clinically relevant cell numbers. Whereas culturing hPSCs as a two-dimensional monolayer is widely used and relatively simple to perform, their culture as suspended three-dimensional aggregates may enable more economical production in large-scale stirred tank bioreactors. To be more relevant to this biomanufacturing, bench-scale differentiation studies should be initiated from aggregated hPSC cultures. Methods: We compared five available bench-scale platforms for generating undifferentiated cell aggregates of human embryonic stem cells (hESCs) using AggreWell™ plates, low attachment plates on an orbital shaker, roller bottles, spinner flasks, and vertical-wheel bioreactors (PBS-Minis). Thereafter, we demonstrated the incorporation of an hPSC aggregation step prior to directed differentiation to pancreatic progenitors and endocrine cells. Results and discussion: The AggreWell™ system had the highest aggregation yield. The initial cell concentrations had an impact on the size of aggregates generated when using AggreWell™ plates as well as in roller bottles. However, aggregates made with low attachment plates, spinner flasks and PBS-Minis were similar regardless of the initial cell number. Aggregate morphology was compact and relatively homogenously distributed in all platforms except for the roller bottles. The size of aggregates formed in PBS-Minis was modulated by the agitation rate during the aggregation. In all cell culture platforms, the net growth rate of cells in 3D aggregates was lower (range: -0.01-0.022 h-1) than cells growing as a monolayer (range: 0.039-0.045 h-1). Overall, this study describes operating ranges that yield high-quality undifferentiated hESC aggregates using several of the most commonly used bench-scale cell culture platforms. In all of these systems, methods were identified to obtain PSC aggregates with greater than 70% viability, and mean diameters between 60 and 260 mm. Finally, we showed the capacity of hPSC aggregates formed with PBS-Minis to differentiate into viable pancreatic progenitors and endocrine cell types.

A critical review on therapeutic approaches of CRISPR-Cas9 in diabetes mellitus

Diabetes mellitus (D.M.) is a common metabolic disorder caused mainly by combining two primary factors, which are (1) defects in insulin production by the pancreatic β-cells and (2) responsiveness of insulin-sensitive tissues towards insulin. Despite the rapid advancement in medicine to suppress elevated blood glucose levels (hyperglycemia) and insulin resistance associated with this hazard, a demand has undoubtedly emerged to find more effective and curative dimensions in therapeutic approaches against D.M. The administration of diabetes treatment that emphasizes insulin production and sensitivity may result in unfavorable side effects, reduced adherence, and potential treatment ineffectiveness. Recent progressions in genome editing technologies, for instance, in zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeat (CRISPR-Cas)-associated nucleases, have greatly influenced the gene editing technology from concepts to clinical practices. Improvements in genome editing technologies have also opened up the possibility to target and modify specific genome sequences in a cell directly. CRISPR/Cas9 has proven effective in utilizing ex vivo gene editing in embryonic stem cells and stem cells derived from patients. This application has facilitated the exploration of pancreatic beta-cell development and function. Furthermore, CRISPR/Cas9 enables the creation of innovative animal models for diabetes and assesses the effectiveness of different therapeutic strategies in treating the condition. We, therefore, present a critical review of the therapeutic approaches of the genome editing tool CRISPR-Cas9 in treating D.M., discussing the challenges and limitations of implementing this technology.

The role of noncoding RNAs in pancreatic birth defects

Congenital defects in the pancreas can cause severe health issues such as pancreatic cancer and diabetes which require lifelong treatment. Regenerating healthy pancreatic cells to replace malfunctioning cells has been considered a promising cure for pancreatic diseases including birth defects. However, such therapies are currently unavailable in the clinic. The developmental gene regulatory network underlying pancreatic development must be reactivated for in vivo regeneration and recapitulated in vitro for cell replacement therapy. Thus, understanding the mechanisms driving pancreatic development will pave the way for regenerative therapies. Pancreatic progenitor cells are the precursors of all pancreatic cells which use epigenetic changes to control gene expression during differentiation to generate all of the distinct pancreatic cell types. Epigenetic changes involving DNA methylation and histone modifications can be controlled by noncoding RNAs (ncRNAs). Indeed, increasing evidence suggests that ncRNAs are indispensable for proper organogenesis. Here, we summarize recent insight into the role of ncRNAs in the epigenetic regulation of pancreatic development. We further discuss how disruptions in ncRNA biogenesis and expression lead to developmental defects and diseases. This review summarizes in vivo data from animal models and in vitro studies using stem cell differentiation as a model for pancreatic development.

AT7867 promotes pancreatic progenitor differentiation of human iPSCs

Generation of pure pancreatic progenitor (PP) cells is critical for clinical translation of stem cell-derived islets. Herein, we performed PP differentiation with and without AKT/P70 inhibitor AT7867 and characterized the resulting cells at protein and transcript level in vitro and in vivo upon transplantation into diabetic mice. AT7867 treatment increased the percentage of PDX1+NKX6.1+ (-AT7867: 50.9% [IQR 48.9%-53.8%]; +AT7867: 90.8% [IQR 88.9%-93.7%]; p = 0.0021) and PDX1+GP2+ PP cells (-AT7867: 39.22% [IQR 36.7%-44.1%]; +AT7867: 90.0% [IQR 88.2%-93.6%]; p = 0.0021). Transcriptionally, AT7867 treatment significantly upregulated PDX1 (p = 0.0001), NKX6.1 (p = 0.0005), and GP2 (p = 0.002) expression compared with controls, while off-target markers PODXL (p < 0.0001) and TBX2 (p < 0.0001) were significantly downregulated. Transplantation of AT7867-treated PPs resulted in faster hyperglycemia reversal in diabetic mice compared with controls (time and group: p < 0.0001). Overall, our data show that AT7867 enhances PP cell differentiation leading to accelerated diabetes reversal.

Stem cells therapy for diabetes: from past to future

Diabetes mellitus is a chronic disease of carbohydrate metabolism characterized by uncontrolled hyperglycemia due to the body's impaired ability to produce or respond to insulin. Oral or injectable exogenous insulin and its analogs cannot mimic endogenous insulin secreted by healthy individuals, and pancreatic and islet transplants face a severe shortage of sources and transplant complications, all of which limit the widespread use of traditional strategies in diabetes treatment. We are now in the era of stem cells and their potential in ameliorating human disease. At the same time, the rapid development of gene editing and cell-encapsulation technologies has added to the wings of stem cell therapy. However, there are still many unanswered questions before stem cell therapy can be applied clinically to patients with diabetes. In this review, we discuss the progress of strategies to obtain insulin-producing cells from different types of stem cells, the application of gene editing in stem cell therapy for diabetes, as well as summarize the current advanced cell encapsulation technologies in diabetes therapy and look forward to the future development of stem cell therapy in diabetes.

The functional maturity of grafted human pluripotent stem cell derived-islets (hSC-Islets) evaluated by the glycemic set point during blood glucose normalizing process in diabetic mice

Human pluripotent stem cell (hPSCs) derived-pancreatic islets (hSC-islets) are good candidates for cell replacement therapy for patients with diabetes as substitutes for deceased donor-derived islets, because they are pluripotent and have infinite proliferation potential. Grafted hSC-islets ameliorate hyperglycemia in diabetic mice; however, several weeks are needed to normalize the hyperglycemia. These data suggest hSC-islets require maturation, but their maturation process in vivo is not yet fully understood. In this study, we utilized two kinds of streptozotocin (STZ)-induced diabetes model mice by changing the administration timing in order to examine the time course of maturation of hSC-islets and the effects of hyperglycemia on their maturation. We found no hyperglycemia in immune-compromised mice when hSC-islets had been transplanted under their kidney capsules in advance, and STZ was administered 4 weeks after transplantation. Of note, the blood glucose levels of those mice were stably maintained under 100 mg/dl 10 weeks after transplantation; this is lower than the mouse glycemic set point (120-150 mg/dl), suggesting that hSC-islets control blood glucose levels to the human glycemic set point. We confirmed that gene expression of maturation markers of pancreatic beta cells tended to upregulate during 4 weeks after transplantation. Periodical histological analysis revealed that revascularization was observed as early as 1 week after transplantation, but reinnervation in the grafted hSC-islets was not detected at all, even 15 weeks after transplantation. In conclusion, our hSC-islets need at least 4 weeks to mature, and the human glycemic set point is a good index for evaluating ultimate maturity for hSC-islets in vivo.

iPSC-Derived Glioblastoma Cells Have Enhanced Stemness Wnt/β-Catenin Activity Which Is Negatively Regulated by Wnt Antagonist sFRP4

Growing evidence indicates that cancer stem cells (CSCs) endow the tumor with stem-like properties. Recently, induced pluripotent stem cells (iPSCs) have gained increased attention because of their easy derivation and availability and their potential to differentiate into any cell type. A CSC model derived from iPSCs of human origin would help understand the driving force of tumor initiation and early progression. We report the efficient generation of feeder-free SSEA4, TRA-1-60 and TRA-1-81 positive iPSCs from amniotic membrane-derived mesenchymal stem cells (AMMSCs), which successfully differentiated into three germ layers. We then developed human iPSC-derived glioblastoma multiforme (GBM) model using conditioned media (CM) from U87MG cell line and CSCs derived from U87MG, which confer iPSCs with GBM and GSC-like phenotypes within five days. Both cell types overexpress MGMT and GLI2, but only GSCs overexpress CD133, CD44, ABCG2 and ABCC2. We also observed overexpression of LEF1 and β-catenin in both cell types. Down-regulation of Wnt antagonist secreted frizzled-related protein 4 (sFRP4) in GBM and GSCs, indicating activation of the Wnt/β-catenin pathway, which could be involved in the conversion of iPSCs to CSCs. From future perspectives, our study will help in the creation of a rapid cell-based platform for understanding the complexity of GBM.

Enrichment of stem cell-derived pancreatic beta-like cells and controlled graft size through pharmacological removal of proliferating cells

Transplantation of limited human cadaveric islets into type 1 diabetic patients results in ∼35 months of insulin independence. Direct differentiation of stem cell-derived insulin-producing beta-like cells (sBCs) that can reverse diabetes in animal models effectively removes this shortage constraint, but uncontrolled graft growth remains a concern. Current protocols do not generate pure sBCs, but consist of only 20%-50% insulin-expressing cells with additional cell types present, some of which are proliferative. Here, we show the selective ablation of proliferative cells marked by SOX9 by simple pharmacological treatment in vitro. This treatment concomitantly enriches for sBCs by ∼1.7-fold. Treated sBC clusters show improved function in vitro and in vivo transplantation controls graft size. Overall, our study provides a convenient and effective approach to enrich for sBCs while minimizing the presence of unwanted proliferative cells and thus has important implications for current cell therapy approaches.

Protocol development to further differentiate and transition stem cell-derived pancreatic progenitors from a monolayer into endocrine cells in suspension culture

The generation of functional β-cells from human pluripotent stem cells (hPSCs) for cell replacement therapy and disease modeling of diabetes is being investigated by many groups. We have developed a protocol to harvest and aggregate hPSC-derived pancreatic progenitors generated using a commercially available kit into near uniform spheroids and to further differentiate the cells toward an endocrine cell fate in suspension culture. Using a static suspension culture platform, we could generate a high percentage of insulin-expressing, glucose-responsive cells. We identified FGF7 as a soluble factor promoting aggregate survival with no inhibitory effect on endocrine gene expression. Notch inhibition of pancreatic progenitor cells during aggregation improved endocrine cell induction in vitro and improved graft function following implantation and further differentiation in mice. Thus we provide an approach to promote endocrine formation from kit-derived pancreatic progenitors, either through extended culture or post implant.

Differentiation of stem cell-derived pancreatic progenitors into insulin-secreting islet clusters in a multiwell-based static 3D culture system

Orbital shaker-based suspension culture systems have been in widespread use for differentiating human pluripotent stem cell (hPSC)-derived pancreatic progenitors toward islet-like clusters during endocrine induction stages. However, reproducibility between experiments is hampered by variable degrees of cell loss in shaking cultures, which contributes to variable differentiation efficiencies. Here, we describe a 96-well-based static suspension culture method for differentiation of pancreatic progenitors into hPSC-islets. Compared with shaking culture, this static 3D culture system induces similar islet gene expression profiles during differentiation processes but significantly reduces cell loss and improves cell viability of endocrine clusters. This static culture method results in more reproducible and efficient generation of glucose-responsive, insulin-secreting hPSC-islets. The successful differentiation and well-to-well consistency in 96-well plates also provides a proof of principle that the static 3D culture system can serve as a platform for small-scale compound screening experiments as well as facilitating further protocol development.

Extrahepatic transplantation of 3D cultured stem cell-derived islet organoids on microporous scaffolds

Stem cell differentiation methods have been developed to produce cells capable of insulin secretion which are showing promise in clinical trials for treatment of type-1 diabetes. Nevertheless, opportunities remain to improve cell maturation and function. Three-dimensional (3D) culture has demonstrated improved differentiation and metabolic function in organoid systems, with biomaterial scaffolds employed to direct cell assembly and facilitate cell-cell contacts. Herein, we investigate 3D culture of human stem cell-derived islet organoids, with 3D culture initiated at the pancreatic progenitor, endocrine progenitor, or immature β-cell stage. Clusters formed by reaggregation of immature β-cells could be readily seeded into the microporous poly(lactide-co-glycolide) scaffold, with control over cell number. Culture of islet organoids on scaffolds at the early to mid-stage beta cell progenitors had improved in vitro glucose stimulated insulin secretion relative to organoids formed at the pancreatic progenitor stage. Reaggregated islet organoids were transplanted into the peritoneal fat of streptozotocin-induced diabetic mice, which resulted in reduced blood glucose levels and the presence of systemic human C-peptide. In conclusion, 3D cell culture supports development of islet organoids as indicated by insulin secretion in vitro and supports transplantation to extrahepatic sites that leads to a reduction of hyperglycemia in vivo.

Developments in stem cell-derived islet replacement therapy for treating type 1 diabetes

The generation of islet-like endocrine clusters from human pluripotent stem cells (hPSCs) has the potential to provide an unlimited source of insulin-producing β cells for the treatment of diabetes. In order for this cell therapy to become widely adopted, highly functional and well-characterized stem cell-derived islets (SC-islets) need to be manufactured at scale. Furthermore, successful SC-islet replacement strategies should prevent significant cell loss immediately following transplantation and avoid long-term immune rejection. This review highlights the most recent advances in the generation and characterization of highly functional SC-islets as well as strategies to ensure graft viability and safety after transplantation.

Construction of PLGA Porous Microsphere-Based Artificial Pancreatic Islets Assisted by the Cell Centrifugation Perfusion Technique

Pancreatic islet transplantation is a promising treatment that could potentially reverse diabetes, but its clinical applicability is severely limited by a shortage of organ donors. Various cell loading approaches using polymeric porous microspheres (PMs) have been developed for tissue regeneration; however, PM-based multicellular artificial pancreatic islets' construction has been scarcely reported. In this study, MIN6 (a mouse insulinoma cell line) and MS1 (a mouse pancreatic islet endothelial cell line) cells were seeded into poly(lactic-co-glycolic acid) (PLGA) PMs via an upgraded centrifugation-based cell perfusion seeding technique invented and patented by our group. Cell morphology, distribution, viability, migration, and proliferation were all evaluated. Results from glucose-stimulated insulin secretion (GSIS) assay and RNA-seq analysis suggested that MIN6 and MS1-loaded PLGA PMs exhibited better glucose responsiveness, which is partly attributable to vascular formation during PM-dependent islet construction. The present study suggests that the PLGA PM-based artificial pancreatic islets may provide an alternative strategy for the potential treatment of diabetes in the future.

Cellular therapies in liver and pancreatic diseases

Over the past two decades, developments in regenerative medicine in gastroenterology have been greatly enhanced by the application of stem cells, which can self-replicate and differentiate into any somatic cell. The discovery of induced pluripotent stem cells has opened remarkable perspectives on tissue regeneration, including their use as a bridge to transplantation or as supportive therapy in patients with organ failure. The improvements in DNA manipulation and gene editing strategies have also allowed to clarify the physiopathology and to correct the phenotype of several monogenic diseases, both in vivo and in vitro. Further progress has been made with the development of three-dimensional cultures, known as organoids, which have demonstrated morphological and functional complexity comparable to that of a miniature organ. Hence, owing to its protean applications and potential benefits, cell and organoid transplantation has become a hot topic for the management of gastrointestinal diseases. In this review, we describe current knowledge on cell therapies in hepatology and pancreatology, providing insight into their future applications in regenerative medicine.

Human pluripotent stem cell-derived β cells: Truly immature islet β cells for type 1 diabetes therapy?

A century has passed since the Nobel Prize winning discovery of insulin, which still remains the mainstay treatment for type 1 diabetes mellitus (T1DM) to this day. True to the words of its discoverer Sir Frederick Banting, “insulin is not a cure for diabetes, it is a treatment”, millions of people with T1DM are dependent on daily insulin medications for life. Clinical donor islet transplantation has proven that T1DM is curable, however due to profound shortages of donor islets, it is not a mainstream treatment option for T1DM. Human pluripotent stem cell derived insulin-secreting cells, pervasively known as stem cell-derived β cells (SC-β cells), are a promising alternative source and have the potential to become a T1DM treatment through cell replacement therapy. Here we briefly review how islet β cells develop and mature in vivo and several types of reported SC-β cells produced using different ex vivo protocols in the last decade. Although some markers of maturation were expressed and glucose stimulated insulin secretion was shown, the SC-β cells have not been directly compared to their in vivo counterparts, generally have limited glucose response, and are not yet fully matured. Due to the presence of extra-pancreatic insulin-expressing cells, and ethical and technological issues, further clarification of the true nature of these SC-β cells is required.

Human Hematopoietic Stem/Progenitor Cells in Type One Diabetes Mellitus Treatment: Is There an Ideal Candidate?

Type 1 diabetes mellitus (T1DM) is a highly prevalent autoimmune disease causing the destruction of pancreatic islet β-cells. The resulting insulin production deficiency leads to a lifelong need for insulin re-placement therapy, systemic complications, and reduced life quality and expectancy. Cell therapy has been extensively attempted to restore insulin independence (IID), and autologous nonmyeloablative hematopoietic stem cell transplantation (AHST) has appeared to give the most promising results, but with a highly variable quote of patients achieving IID across the studies. We performed a comprehensive review of the trials involving stem cells, and in particular AHST, for the treatment of T1DM. We then pooled the patients enrolled in the different trials and looked for the patient characteristics that could be associated with the achievement of IID. We found a significantly higher probability of achieving IID in older patients (OR 1.17, 95%CI 1.06–1.33, p = 0.002) and a significantly lower probability in patients with a history of ketoacidosis (OR 0.23, 95%CI 0.06–0.78, p = 0.023). This suggests that there could be a population of patients more likely to benefit from AHST, but further data would be required to depict the profile of the ideal candidate.

Direct reprogramming of human fibroblasts into insulin-producing cells using transcription factors

Direct lineage reprogramming of one somatic cell into another without transitioning through a progenitor stage has emerged as a strategy to generate clinically relevant cell types. One cell type of interest is the pancreatic insulin-producing β cell whose loss and/or dysfunction leads to diabetes. To date it has been possible to create β-like cells from related endodermal cell types by forcing the expression of developmental transcription factors, but not from more distant cell lineages like fibroblasts. In light of the therapeutic benefits of choosing an accessible cell type as the cell of origin, in this study we set out to analyze the feasibility of transforming human skin fibroblasts into β-like cells. We describe how the timed-introduction of five developmental transcription factors (Neurog3, Pdx1, MafA, Pax4, and Nkx2-2) promotes conversion of fibroblasts toward a β-cell fate. Reprogrammed cells exhibit β-cell features including β-cell gene expression and glucose-responsive intracellular calcium mobilization. Moreover, reprogrammed cells display glucose-induced insulin secretion in vitro and in vivo. This work provides proof-of-concept of the capacity to make insulin-producing cells from human fibroblasts via transcription factor-mediated direct reprogramming.

Single-cell analyses reveal distinct expression patterns and roles of long non-coding RNAs during hESC differentiation into pancreatic progenitors

BACKGROUND

Deep understanding the differentiation process of human embryonic stem cells (hESCs) is essential for developing cell-based therapeutic strategy. Substantial efforts have been made to investigate protein-coding genes, yet it remains lacking comprehensive characterization of long non-coding RNAs (lncRNAs) during this process.

METHODS

hESCs were passaged every 5-6 days and had maintained stable karyotype even until the 50th generation. Pancreatic progenitor specification of in vitro differentiation from hESCs was performed and modified. The nuclei were stained with 4,6-Diamidino-2-phenylindole (DAPI). Droplet-based platform (10X Genomics) was applied to generate the single-cell RNA sequencing (scRNA-seq) data. The quality of the filtered read pairs was evaluated by using FastQC. Batch effects were removed using the size factor method. Dimension reduction and unsupervised clustering analyses were performed using Seurat R package. The Monocle 2 and MetaCell algorithms were used to order single cells on a pseudotime course and partition the scRNA-seq data into metacells, respectively. Co-expression network was constructed using WGCNA. Module- and hub-based methods were adopted to predict the functions of lncRNAs.

RESULTS

A total of 77,382 cells during the differentiation process of hESCs toward pancreatic progenitors were sequenced. According to the single-cell map, the cells from different time points were authenticated to constitute a relatively homogeneous population, in which a total of 7382 lncRNAs could be detected. Through further analyzing the time course data, conserved and specific expression features of lncRNAs during hESC differentiation were revealed. Based upon pseudotime analysis, 52 pseudotime-associated lncRNAs that grouped into three distinct expression patterns were identified. We also implemented MetaCell algorithm and network-based methods to explore the functional mechanisms of these lncRNAs. Totally, 464 lncRNAs, including 49 pseudotime-associated lncRNAs were functionally annotated by either module-based or hub-based methods. Most importantly, we demonstrated that the lncRNA HOTAIRM1, which co-localized and co-expressed with several HOX genes, may play crucial role in the generation of pancreatic progenitors through regulation of exocytosis and retinoic acid receptor signaling pathway.

CONCLUSIONS

Our single-cell analyses provide valuable data resources for biological researchers and novel insights into hESC differentiation processes, which will guide future endeavors to further elucidate the roles of lncRNAs.

Cell Replacement Therapy for Type 1 Diabetes Patients: Potential Mechanisms Leading to Stem-Cell-Derived Pancreatic β-Cell Loss upon Transplant

Cell replacement therapy using stem-cell-derived insulin-producing β-like cells (sBCs) has been proposed as a practical cure for patients with type one diabetes (T1D). sBCs can correct diabetes in preclinical animal models, demonstrating the promise of this stem cell-based approach. However, in vivo studies have demonstrated that most sBCs, similarly to cadaveric human islets, are lost upon transplantation due to ischemia and other unknown mechanisms. Hence, there is a critical knowledge gap in the current field concerning the fate of sBCs upon engraftment. Here we review, discuss effects, and propose additional potential mechanisms that could contribute toward β-cell loss in vivo. We summarize and highlight some of the literature on phenotypic loss in β-cells under both steady, stressed, and diseased diabetic conditions. Specifically, we focus on β-cell death, dedifferentiation into progenitors, trans-differentiation into other hormone-expressing cells, and/or interconversion into less functional β-cell subtypes as potential mechanisms. While current cell replacement therapy efforts employing sBCs carry great promise as an abundant cell source, addressing the somewhat neglected aspect of β-cell loss in vivo will further accelerate sBC transplantation as a promising therapeutic modality that could significantly enhance the life quality of T1D patients.

Repopulation of decellularized organ scaffolds with human pluripotent stem cell-derived pancreatic progenitor cells

Diabetes is an emerging global epidemic that affects more that 285 million people worldwide. Engineering of endocrine pancreas tissue holds great promise for the future of diabetes therapy. Here we demonstrate the feasibility of re-engineering decellularized organ scaffolds using regenerative cell source. We differentiated human pluripotent stem cells (hPSC) toward pancreatic progenitor (PP) lineage and repopulated decellularized organ scaffolds with these hPSC-PP cells. We observed that hPSCs cultured and differentiated as aggregates are more suitable for organ repopulation than isolated single cell suspension. However, recellularization with hPSC-PP aggregates require a more extensive vascular support, which was found to be superior in decellularized liver over the decellularized pancreas scaffolds. Upon continued culture for nine days with chemical induction in the bioreactor, the seeded hPSC-PP aggregates demonstrated extensive and uniform cellular repopulation and viability throughout the thickness of the liver scaffolds. Furthermore, the decellularized liver scaffolds was supportive of the endocrine cell fate of the engrafted cells. Our novel strategy to engineer endocrine pancreas construct is expected to find potential applications in preclinical testing, drug discovery and diabetes therapy.

The future treatment for type 1 diabetes: Pig islet- or stem cell-derived β cells?

Replacement of β cells is only a curative approach for type 1 diabetes (T1D) patients to avoid the threat of iatrogenic hypoglycemia. In this pursuit, islet allotransplantation under Edmonton's protocol emerged as a medical miracle to attain hypoglycemia-free insulin independence in T1D. Shortage of allo-islet donors and post-transplantation (post-tx) islet loss are still unmet hurdles for the widespread application of this therapeutic regimen. The long-term survival and effective insulin independence in preclinical studies have strongly suggested pig islets to cure overt hyperglycemia. Importantly, CRISPR-Cas9 technology is pursuing to develop "humanized" pig islets that could overcome the lifelong immunosuppression drug regimen. Lately, induced pluripotent stem cell (iPSC)-derived β cell approaches are also gaining momentum and may hold promise to yield a significant supply of insulin-producing cells. Theoretically, personalized β cells derived from a patient's iPSCs is one exciting approach, but β cell-specific immunity in T1D recipients would still be a challenge. In this context, encapsulation studies on both pig islet as well as iPSC-β cells were found promising and rendered long-term survival in mice. Oxygen tension and blood vessel growth within the capsules are a few of the hurdles that need to be addressed. In conclusion, challenges associated with both procedures, xenotransplantation (of pig-derived islets) and stem cell transplantation, are required to be cautiously resolved before their clinical application.

Single-cell profiling of GP2-enriched pancreatic progenitors to simultaneously create acinar, ductal, and endocrine organoids

Rationale: Pancreatic lineage specification follows the formation of tripotent pancreatic progenitors (PPs). Current protocols rebuilding PPs in vitro have an endocrine lineage bias and are mostly based on PDX1/NKX6-1 coexpression neglecting other markers decisive for PP heterogeneity and lineage potential. However, true tripotent PPs are of utmost interest to study also exocrine disorders such as pancreatic cancer and to simultaneously generate all three pancreatic lineages from the same ancestor. Methods: Here, we performed a comprehensive compound testing to advance the generation of multipotent progenitors, which were further characterized for their trilineage potential in vitro and in vivo. The heterogeneity and cell-cell communication across the PP subpopulations were analyzed via single-cell transcriptomics. Results: We introduce a novel PP differentiation platform based on a comprehensive compound screening with an advanced design of experiments computing tool to reduce impurities and to increase Glycoprotein-2 expression and subsequent trilineage potential. Superior PP tripotency was proven in vitro by the generation of acinar, endocrine, and ductal cells as well as in vivo upon orthotopic transplantation revealing all three lineages at fetal maturation level. GP2 expression levels at PP stage ascribed varying pancreatic lineage potential. Intermediate and high GP2 levels were superior in generating endocrine and duct-like organoids (PDLO). FACS-based purification of the GP2^high PPs allowed the generation of pancreatic acinar-like organoids (PALO) with proper morphology and expression of digestive enzymes. scRNA-seq confirmed multipotent identity, positioned the GP2/PDX1/NKX6-1^high population next to human fetal tip and trunk progenitors and identified novel ligand-receptor (LR) interactions in distinct PP subpopulations. LR validation experiments licensed midkine and VEGF signaling to increase markers labelling the single cell clusters with high GP2 expression. Conclusion: In this study, we guide human pluripotent stem cells into multipotent pancreatic progenitors. This common precursor population, which has the ability to mature into acinar, ductal and functional β-cells, serves as a basis for studying developmental processes and deciphering early cancer formation in a cell type-specific context. Using single-cell RNA sequencing and subsequent validation studies, we were able to dissect PP heterogeneity and specific cell-cell communication signals.

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.

Determinants and dynamics of pancreatic islet architecture

The islets of Langerhans are highly organized structures that have species-specific, three-dimensional tissue architecture. Islet architecture is critical for proper hormone secretion in response to nutritional stimuli. Islet architecture is disrupted in all types of diabetes mellitus and in cadaveric islets for transplantation during isolation, culture, and perfusion, limiting patient outcomes. Moreover, recapitulating native islet architecture remains a key challenge for in vitro generation of islets from stem cells. In this review, we discuss work that has led to the current understanding of determinants of pancreatic islet architecture, and how this architecture is maintained or disrupted during tissue remodeling in response to normal and pathological metabolic changes. We further discuss both empirical and modeling data that highlight the importance of islet architecture for islet function.

Fas Ligand-Modified Scaffolds Protect Stem Cell Derived β-Cells by Modulating Immune Cell Numbers and Polarization

Stem cell derived β-cells have demonstrated the potential to control blood glucose levels and represent a promising treatment for Type 1 diabetes (T1D). Early engraftment post-transplantation and subsequent maturation of these β-cells are hypothesized to be limited by the initial inflammatory response, which impacts the ability to sustain normoglycemia for long periods. We investigated the survival and development of immature hPSC-derived β-cells transplanted on poly(lactide-co-glycolide) (PLG) microporous scaffolds into the peritoneal fat, a site being considered for clinical translation. The scaffolds were modified with biotin for binding of a streptavidin-FasL (SA-FasL) chimeric protein to modulate the local immune cell responses. The presence of FasL impacted infiltration of monocytes and neutrophils and altered the immune cell polarization. Conditioned media generated from SA-FasL scaffolds explanted at day 4 post-transplant did not impact hPSC-derived β-cell survival and maturation in vitro, while these responses were reduced with conditioned media from control scaffolds. Following transplantation, β-cell viability and differentiation were improved with SA-FasL modification. A sustained increase in insulin positive cell ratio was observed with SA-FasL-modified scaffolds relative to control scaffolds. These results highlight that the initial immune response can significantly impact β-cell engraftment, and modulation of cell infiltration and polarization may be a consideration for supporting long-term function at an extrahepatic site.

Genetic Engineering of Immune Evasive Stem Cell-Derived Islets

Genome editing has the potential to revolutionize many investigative and therapeutic strategies in biology and medicine. In the field of regenerative medicine, one of the leading applications of genome engineering technology is the generation of immune evasive pluripotent stem cell-derived somatic cells for transplantation. In particular, as more functional and therapeutically relevant human pluripotent stem cell-derived islets (SCDI) are produced in many labs and studied in clinical trials, there is keen interest in studying the immunogenicity of these cells and modulating allogeneic and autoimmune immune responses for therapeutic benefit. Significant experimental work has already suggested that elimination of Human Leukocytes Antigen (HLA) expression and overexpression of immunomodulatory genes can impact survival of a variety of pluripotent stem cell-derived somatic cell types. Limited work published to date focuses on stem cell-derived islets and work in a number of labs is ongoing. Rapid progress is occurring in the genome editing of human pluripotent stem cells and their progeny focused on evading destruction by the immune system in transplantation models, and while much research is still needed, there is no doubt the combined technologies of genome editing and stem cell therapy will profoundly impact transplantation medicine in the future.

Using single-cell multi-omics screening of human fetal pancreas to identify novel players in human beta cell development

Islet transplantation from organ donors can considerably improve glucose homeostasis and well-being in individuals with type 1 diabetes, where the beta cells are destroyed by the autoimmune attack, but there are insufficient donor islets to make this a widespread therapy. Strategies are therefore being developed to generate unlimited amounts of insulin-producing beta cells from pluripotent stem cells, with the aim that they will be transplanted to treat diabetes. Whilst much progress has been made in recent years in the directed differentiation of pluripotent stem cells to beta-like cells, essential gaps still exist in generating stem cell-derived beta cells that are fully functional in vitro. This short review provides details of recent multi-'omics' studies of the human fetal pancreas, which are revealing granular information on the various cell types in the developing pancreas. It is anticipated that this fine mapping of the pancreatic cells at single-cell resolution will provide additional insights that can be utilised to reproducibly produce human beta cells in vitro that have the functional characteristics of beta cells within native human islets.

Optimizing Generation of Stem Cell-Derived Islet Cells

Islet transplantation is a highly effective treatment for select patients with type 1 diabetes. Unfortunately, current use is limited to those with brittle disease due to donor limitations and immunosuppression requirements. Discovery of factors for induction of pluripotent stem cells from adult somatic cells into a malleable state has reinvigorated the possibility of autologous-based regenerative cell therapies. Similarly, recent progress in allogeneic human embryonic stem cell islet products is showing early success in clinical trials. Describing safe and standardized differentiation protocols with clear pathways to optimize yield and minimize off-target growth is needed to efficiently move the field forward. This review discusses current islet differentiation protocols with a detailed break-down of differentiation stages to guide step-wise controlled generation of functional islet products.

Importance of multiple endocrine cell types in islet organoids for type 1 diabetes treatment

Almost 50 years ago, scientists developed the bi-hormonal abnormality hypothesis, stating that diabetes is not caused merely by the impaired insulin signaling. Instead, the presence of inappropriate level of glucagon is a prerequisite for the development of type 1 diabetes (T1D). It is widely understood that the hormones insulin and glucagon, secreted by healthy β and α cells respectively, operate in a negative feedback loop to maintain the body's blood sugar levels. Despite this fact, traditional T1D treatments rely solely on exogenous insulin injections. Furthermore, research on cell-based therapies and stem-cell derived tissues tends to focus on the replacement of β cells alone. In vivo, the pancreas is made up of 4 major endocrine cell types, that is, insulin-producing β cells, glucagon-producing α cells, somatostatin-producing δ cells, and pancreatic polypeptide-producing γ cells. These distinct cell types are involved synergistically in regulating islet functions. Therefore, it is necessary to produce a pancreatic islet organoid in vitro consisting of all these cell types that adequately replaces the function of the native islets. In this review, we describe the unique function of each pancreatic endocrine cell type and their interactions contributing to the maintenance of normoglycemia. Furthermore, we detail current sources of whole islets and techniques for their long-term expansion and culture. In addition, we highlight a vast potential of the pancreatic islet organoids for transplantation and diabetes research along with updated new approaches for successful transplantation using stem cell-derived islet organoids.

Protocol-Dependent Morphological Changes in Human Embryonic Stem Cell Aggregates during Differentiation toward Early Pancreatic Fate

Cell therapy is one of the promising approaches used against type 1 diabetes. Efficient generation of human embryonic stem cell (hESC)-derived pancreatic progenitors (PPs) is of great importance. Since signaling pathways underlying human pancreas development are not yet fully understood, various differentiation protocols are conducted, each considering variable duration, timing, and concentrations of growth factors and small molecules. Therefore, we compared two PP differentiation protocols in static suspension culture. We tested modified protocols developed by Pagliuca et al. (protocol 1) and Royan researchers (protocol 2) until early PP stage. The morphological changes of hESC aggregates during differentiation, and also gene and protein expression after differentiation, were evaluated. Different morphological structures were formed in each protocol. Quantitative gene expression analysis, flow cytometry, and immunostaining revealed a high level of PDX1 expression on day 13 of Royan's differentiation protocol compared to protocol 1. Our data showed that using protocol 2, cells were further differentiated until day 16, showing higher efficiency of early PPs. Moreover, protocol 2 is able to produce hESCs-PPs in a static suspension culture. Since protocol 2 is inexpensive in terms of media, growth factors, and chemicals, it can be used for massive production of PPs using static and dynamic suspension cultures.