Inducible Pluripotent Stem Cells as a Potential Cure for Diabetes

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.

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.

Mitochondrial regulation in human pluripotent stem cells during reprogramming and β cell differentiation

Mitochondria are the powerhouse of the cell and dynamically control fundamental biological processes including cell reprogramming, pluripotency, and lineage specification. Although remarkable progress in induced pluripotent stem cell (iPSC)-derived cell therapies has been made, very little is known about the role of mitochondria and the mechanisms involved in somatic cell reprogramming into iPSC and directed reprogramming of iPSCs in terminally differentiated cells. Reprogramming requires changes in cellular characteristics, genomic and epigenetic regulation, as well as major mitochondrial metabolic changes to sustain iPSC self-renewal, pluripotency, and proliferation. Differentiation of autologous iPSC into terminally differentiated β-like cells requires further metabolic adaptation. Many studies have characterized these alterations in signaling pathways required for the generation and differentiation of iPSC; however, very little is known regarding the metabolic shifts that govern pluripotency transition to tissue-specific lineage differentiation. Understanding such metabolic transitions and how to modulate them is essential for the optimization of differentiation processes to ensure safe iPSC-derived cell therapies. In this review, we summarize the current understanding of mitochondrial metabolism during somatic cell reprogramming to iPSCs and the metabolic shift that occurs during directed differentiation into pancreatic β-like cells.

Stem Cell-Derived Islet Transplantation in Patients With Type 2 Diabetes: Can Diabetes Subtypes Guide Implementation?

Historically, only patients with brittle diabetes or severe recurrent hypoglycemia have been considered for islet transplantation (ITx). This population has been selected to optimize the risk-benefit profile, considering risks of long-term immunosuppression and limited organ supply. However, with the advent of stem cell (SC)-derived ITx and the potential for immunosuppression-free ITx, consideration of a broader recipient cohort may soon be justified. Simultaneously, the classical categorization of diabetes is being challenged by growing evidence in support of a clustering of disease subtypes that can be better categorized by the All New Diabetics in Scania (ANDIS) classification system. Using the ANDIS classification, 5 subtypes of diabetes have been described, each with unique causes and consequences. We evaluate consideration for ITx in the context of this broader patient population and the new classification of diabetes subtypes. In this review, we evaluate considerations for ITx based on novel diabetes subtypes, including their limitations, and we elaborate on unique transplant features that should now be considered to enable ITx in these "unconventional" patient cohorts. Based on evidence from those receiving whole pancreas transplant and our more than 20-year experience with ITx, we offer recommendations and potential research avenues to justify implementation of SC-derived ITx in broader populations of patients with all types of diabetes.

Unlocking the post-transplant microenvironment for successful islet function and survival

Islet transplantation (IT) offers the potential to restore euglycemia for patients with type 1 diabetes mellitus (T1DM). Despite improvements in islet isolation techniques and immunosuppressive regimes, outcomes remain suboptimal with UK five-year graft survivals (5YGS) of 55% and most patients still requiring exogenous insulin after multiple islet infusions. Native islets have a significant non-endocrine component with dense extra-cellular matrix (ECM), important for islet development, cell survival and function. Collagenase isolation necessarily disrupts this complex islet microenvironment, leaving islets devoid of a supporting framework and increasing vulnerability of transplanted islets. Following portal venous transplantation, a liver injury response is potentially induced, which typically results in inflammation and ECM deposition from liver specific myofibroblasts. The impact of this response may have important impact on islet survival and function. A fibroblast response and ECM deposition at the kidney capsule and eye chamber alongside other implantation sites have been shown to be beneficial for survival and function. Investigating the implantation site microenvironment and the interactions of transplanted islets with ECM proteins may reveal therapeutic interventions to improve IT and stem-cell derived beta-cell therapy.

Recent trends and advances in type 1 diabetes therapeutics: A comprehensive review

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by the destruction of pancreatic β-cells, leading to insulin deficiency. Insulin replacement therapy is the current standard of care for T1D, but it has significant limitations. However, stem cell-based replacement therapy has the potential to restore β-cell function and achieve glycaemic control eradicating the necessity for drugs or injecting insulin externally. While significant progress has been made in preclinical studies, the clinical translation of stem cell therapy for T1D is still in its early stages. In continuation, further research is essentially required to determine the safety and efficacy of stem cell therapies and to develop strategies to prevent immune rejection of stem cell-derived β-cells. The current review highlights the current state of cellular therapies for T1D including, different types of stem cell therapies, gene therapy, immunotherapy, artificial pancreas, and cell encapsulation being investigated, and their potential for clinical translation.

C-peptide Targets and Patient-centered Outcomes of Relevance to Cellular Transplantation for Diabetes

BACKGROUND

C-peptide levels are a key measure of beta-cell mass following islet transplantation, but threshold values required to achieve clinically relevant patient-centered outcomes are not yet established.

METHODS

We conducted a cross-sectional retrospective cohort study evaluating patients undergoing islet transplantation at a single center from 1999 to 2018. Cohorts included patients achieving insulin independence without hypoglycemia, those with insulin dependence without hypoglycemia, and those with recurrent symptomatic hypoglycemia. Primary outcome was fasting C-peptide levels at 6 to 12 mo postfirst transplant; secondary outcomes included stimulated C-peptide levels and BETA-2 scores. Fasting and stimulated C-peptide and BETA-2 cutoff values for determination of hypoglycemic freedom and insulin independence were evaluated using receiver operating characteristic curves.

RESULTS

We analyzed 192 patients, with 122 (63.5%) being insulin independent without hypoglycemia, 61 (31.8%) being insulin dependent without hypoglycemia, and 9 (4.7%) experiencing recurrent symptomatic hypoglycemia. Patients with insulin independence had a median (interquartile range) fasting C-peptide level of 0.66 nmol/L (0.34 nmol/L), compared with 0.49 nmol/L (0.25 nmol/L) for those being insulin dependent without hypoglycemia and 0.07 nmol/L (0.05 nmol/L) for patients experiencing hypoglycemia ( P < 0.001). Optimal fasting C-peptide cutoffs for insulin independence and hypoglycemia were ≥0.50 nmol/L and ≥0.12 nmol/L, respectively. Cutoffs for insulin independence and freedom of hypoglycemia using stimulated C-peptide were ≥1.2 nmol/L and ≥0.68 nmol/L, respectively, whereas optimal cutoff BETA-2 scores were ≥16.4 and ≥5.2.

CONCLUSIONS

We define C-peptide levels and BETA-2 scores associated with patient-centered outcomes. Characterizing these values will enable evaluation of ongoing clinical trials with islet or stem cell therapies.

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.

Characterization of stem-cell-derived islets during differentiation and after implantation

Recapitulation of embryonic pancreatic development has enabled development of methods for in vitro islet cell differentiation using human pluripotent stem cells (hPSCs), which have the potential to cure diabetes. Advanced methods for optimal generation of stem-cell-derived islets (SC-islets) has enabled successful diabetes reversal in rodents and shown promising early clinical trial outcomes. The main impediment for use of SC-islets is concern about safety because of off-target growth resulting from contaminated residual cells. In this review, we summarize the different endocrine and non-endocrine cell populations that have been described to emerge throughout β cell differentiation and after transplantation. We discuss the most recent approaches to enrich endocrine populations and remove off-target cells. Finally, we discuss the critical quality control and release criteria testing that we anticipate will be required prior to transplantation to ensure product safety.

Establishment and characterization of a novel human induced pluripotent stem cell line stably expressing the iRFP720 reporter

Stem cell therapy has great potential for replacing beta-cell loss in diabetic patients. However, a key obstacle to cell therapy’s success is to preserve viability and function of the engrafted cells. While several strategies have been developed to improve engrafted beta-cell survival, tools to evaluate the efficacy within the body by imaging are limited. Traditional labeling tools, such as GFP-like fluorescent proteins, have limited penetration depths in vivo due to tissue scattering and absorption. To circumvent this limitation, a near-infrared fluorescent mutant version of the DrBphP bacteriophytochrome, iRFP720, has been developed for in vivo imaging and stem/progenitor cell tracking. Here, we present the generation and characterization of an iRFP720 expressing human induced pluripotent stem cell (iPSC) line, which can be used for real-time imaging in various biological applications. To generate the transgenic cells, the CRISPR/Cas9 technology was applied. A puromycin resistance gene was inserted into the AAVS1 locus, driven by the endogenous PPP1R12C promoter, along with the CAG-iRFP720 reporter cassette, which was flanked by insulator elements. Proper integration of the transgene into the targeted genomic region was assessed by comprehensive genetic analysis, verifying precise genome editing. Stable expression of iRFP720 in the cells was confirmed and imaged by their near-infrared fluorescence. We demonstrated that the reporter iPSCs exhibit normal stem cell characteristics and can be efficiently differentiated towards the pancreatic lineage. As the genetically modified reporter cells show retained pluripotency and multilineage differentiation potential, they hold great potential as a cellular model in a variety of biological and pharmacological applications.

Outcomes Following Extrahepatic and Intraportal Pancreatic Islet Transplantation: A Comparative Cohort Study

BACKGROUND

Preliminary studies show promise for extrahepatic islet transplantation (ITx). However, clinical comparisons with intraportal ITx outcomes remain limited.

METHODS

This single-center cohort study evaluates patients receiving extrahepatic or intraportal ITx between 1999 and 2018. Primary outcome was stimulated C-peptide level. Secondary outcomes were fasting plasma glucose, BETA-2 scores, and fasting C-peptide level. Multivariable logistic modeling evaluated factors independently associated with a composite variable of early graft failure and primary nonfunction within 60 d of ITx.

RESULTS

Of 264 patients, 9 (3.5%) received extrahepatic ITx (gastric submucosal = 2, subcutaneous = 3, omental = 4). Group demographics were similar at baseline (age, body mass index, diabetes duration, and glycemic control). At 1-3 mo post-first infusion, patients receiving extrahepatic ITx had significantly lower stimulated C-peptide (0.05 nmol/L versus 1.2 nmol/L, P < 0.001), higher fasting plasma glucose (9.3 mmol/L versus 7.3 mmol/L, P < 0.001), and lower BETA-2 scores (0 versus 11.6, P < 0.001) and SUITO indices (1.5 versus 39.6, P < 0.001) compared with those receiving intraportal ITx. Subjects receiving extrahepatic grafts failed to produce median C-peptide ≥0.2 nmol/L within the first 60 d after transplant. Subsequent intraportal infusion following extrahepatic transplants achieved equivalent outcomes compared with patients receiving intraportal transplant alone. Extrahepatic ITx was independently associated with early graft failure/primary non-function (odds ratio 1.709, confidence interval 73.8-39 616.0, P < 0.001), whereas no other factors were independently predictive.

CONCLUSIONS

Using current techniques, intraportal islet infusion remains the gold standard for clinical ITx, with superior engraftment, graft function, and glycemic outcomes compared with extrahepatic transplantation of human islets.

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.

Update on islet cell transplantation

PURPOSE OF REVIEW

Chronic diabetes-related complications continue to exert a rapidly growing and unsustainable pressure on healthcare systems worldwide. In type 1 diabetes, glycemic control is particularly challenging, as intensive management substantially increase the risk of severe hypoglycemic episodes. Alternative approaches to address this issue are required. Islet cell transplantation offers the best approach to reduce hypoglycemic risks and glycemic lability, while providing optimal glycemic control. Although ongoing efforts have improved clinical outcomes, the constraints in tissue sources and the need for chronic immunosuppression limit the application of islet cell transplantation as a curative therapy for diabetes. This review provides an update on islet cell transplantation, focusing on recent clinical experience, ongoing research, and future challenges.

RECENT FINDINGS

Current evidence demonstrates advances in terms of long-term glycemic control, improved insulin independence rates, and novel approaches to eliminate chronic immunosuppression requirements after islet cell transplantation. Advances in stem cell-based therapies provide a promising path towards truly personalized regenerative therapies, solving both tissue supply shortage and the need for lifelong immunosuppression, enabling widespread use of this potentially curative treatment. However, as these therapies enter the clinical realm, regional access variability and ethical questions regarding commercialization are becoming increasingly important and require a collaborative solution.

SUMMARY

In this state-of-the-art review, we discuss current clinical evidence and discuss key aspects on the present and future of islet cell transplantation.

Study on the TCM Syndromes Evolution and Chinese Herbal Characteristics of Type 2 Diabetes Patients with Different Courses of Disease in TCM "Heat Stage": A Real-World Study

OBJECTIVE

The purpose of this study is to analyze and summarize the syndrome distribution, syndrome evolution, and Chinese herb medicine characteristics of T2D in heat stage.

METHOD

In this study, 228 heat-stage T2D patients were divided into three groups based on the course of disease. Group 1 (the course of disease ≤5 years) included 118 patients. Group 2 (5< the course of disease ≤10 years) had 73 patients. Group 3 (the course of disease >10 years) consisted of 37 patients. The main methods used in our study were complex network community partitioning algorithms and Sankey diagram visualization, based on the clinical electronic medical record data we collected.

RESULT

In the three groups, the nodes with the highest node degree are all "heat syndrome." Edge weight between "heat" and "dampness," "qi stagnation," "phlegm," "liver," and "stomach" is the largest. During the whole course of treatment, 60.17%, 63.01%, and 62.16% of the patients' syndromes in groups 1, 2, and 3, respectively, were ascribed to the heat stage all the time. The patients' syndromes in groups 1 and 2 easily transformed to the syndrome of deficiency of both qi and yin of the spleen and stomach. In group 3, 27% of the patients' syndromes were easily transformed into kidney yin deficiency and qi deficiency and blood stasis syndrome. The largest Chinese herb communities of the patients whose syndromes did not change after treatment in the three groups were all heat-clearing drugs. The proportion of blood-activating drugs in patients with syndrome changes increased significantly after treatment.

CONCLUSION

(1) The basic syndrome of T2D patients in the heat stage is liver-stomach heat syndrome. (2) T2D patients in the heat stage tend to deteriorate towards the direction of qi and yin deficiency syndrome. However, the longer the course of the disease is, the more likely it is to deteriorate to the direction of kidney yin deficiency syndrome and blood stasis syndrome. (3) Drugs that can help T2D patients in the heat stage to maintain their condition stably are heat-clearing drugs represented by Coptis chinensis, which usually need to be combined with warming interior drugs such as Zingiberis Rhizoma and Pinelliae Rhizoma.