LDHB contributes to the regulation of lactate levels and basal insulin secretion in human pancreatic ß cells.

Using 13C6 glucose labeling coupled to gas chromatography-mass spectrometry and 2D 1H-13C heteronuclear single quantum coherence NMR spectroscopy, we have obtained a comparative high-resolution map of glucose fate underpinning ß cell function. In both mouse and human islets, the contribution of glucose to the tricarboxylic acid (TCA) cycle is similar. Pyruvate fueling of the TCA cycle is primarily mediated by the activity of pyruvate dehydrogenase, with lower flux through pyruvate carboxylase. While the conversion of pyruvate to lactate by lactate dehydrogenase (LDH) can be detected in islets of both species, lactate accumulation is 6-fold higher in human islets. Human islets express LDH, with low-moderate LDHA expression and ß cell-specific LDHB expression. LDHB inhibition amplifies LDHA-dependent lactate generation in mouse and human ß cells and increases basal insulin release. Lastly, cis-instrument Mendelian randomization shows that low LDHB expression levels correlate with elevated fasting insulin in humans. Thus, LDHB limits lactate generation in ß cells to maintain appropriate insulin release.

GLP1R and GIPR expression and signaling in pancreatic alpha cells, beta cells and delta cells.

Glucagon-like peptide-1 receptor (GLP1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) are transmembrane receptors involved in insulin, glucagon and somatostatin secretion from the pancreatic islet. Therapeutic targeting of GLP1R and GIPR restores blood glucose levels in part by influencing beta cell, alpha cell and delta cell function. Despite the importance of the incretin-mimetics for diabetes therapy, our understanding of GLP1R and GIPR expression patterns and signaling within the islet remain incomplete. Here, we present the evidence for GLP1R and GIPR expression in the major islet cell types, before addressing signaling pathway(s) engaged, as well as their influence on cell survival and function. While GLP1R is largely a beta cell-specific marker within the islet, GIPR is expressed in alpha cells, beta cells, and (possibly) delta cells. GLP1R and GIPR engage Gs-coupled pathways in most settings, although the exact outcome on hormone release depends on paracrine communication and promiscuous signaling. Biased agonism away from beta-arrestin is an emerging concept for improving therapeutic efficacy, and is also relevant for GLP1R/GIPR dual agonism. Lastly, dual agonists exert multiple effects on islet function through GIPR > GLP1R imbalance, increased GLP1R surface expression and cAMP signaling, as well as beneficial alpha cell-beta cell-delta cell crosstalk.

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.

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

Cell replacement therapy using stem-cell-derived insulin-producing ß-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 ß-cell loss in vivo. We summarize and highlight some of the literature on phenotypic loss in ß-cells under both steady, stressed, and diseased diabetic conditions. Specifically, we focus on ß-cell death, dedifferentiation into progenitors, trans-differentiation into other hormone-expressing cells, and/or interconversion into less functional ß-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 ß-cell loss in vivo will further accelerate sBC transplantation as a promising therapeutic modality that could significantly enhance the life quality of T1D patients.

Stem-Cell-Derived ß-Like Cells with a Functional PTPN2 Knockout Display Increased Immunogenicity.

Type 1 diabetes is a polygenic disease that results in an autoimmune response directed against insulin-producing beta cells. PTPN2 is a known high-risk type 1 diabetes associated gene expressed in both immune- and pancreatic beta cells, but how genes affect the development of autoimmune diabetes is largely unknown. We employed CRISPR/Cas9 technology to generate a functional knockout of PTPN2 in human pluripotent stem cells (hPSC) followed by differentiating stem-cell-derived beta-like cells (sBC) and detailed phenotypical analyses. The differentiation efficiency of PTPN2 knockout (PTPN2 KO) sBC is comparable to wild-type (WT) control sBC. Global transcriptomics and protein assays revealed the increased expression of HLA Class I molecules in PTPN2 KO sBC at a steady state and upon exposure to proinflammatory culture conditions, indicating a potential for the increased immune recognition of human beta cells upon differential PTPN2 expression. sBC co-culture with autoreactive preproinsulin-reactive T cell transductants confirmed increased immune stimulations by PTPN2 KO sBC compared to WT sBC. Taken together, our results suggest that the dysregulation of PTPN2 expression in human beta cell may prime autoimmune T cell reactivity and thereby contribute to the development of type 1 diabetes.

From the dish to humans: A stem cell recipe for success.

Islet transplantation has proven to be an effective treatment for type 1 diabetes (T1D) yet is hampered by the shortage of available tissue. Recently, two reports from a Viacyte multicenter clinical trial demonstrate the feasibility, safety, and potential efficacy of transplanting macro-encapsulated human stem cell-derived pancreatic endoderm cells into patients with T1D, highlighting the promise of a stem cell-based therapeutic approach.

Generation of functional human thymic cells from induced pluripotent stem cells.

BACKGROUND: The thymus is a glandular organ that is essential for the formation of the adaptive immune system by educating developing T cells. The thymus is most active during childhood and involutes around the time of adolescence, resulting in a severe reduction or absence of naive T-cell output. The ability to generate a patient-derived human thymus would provide an attractive research platform and enable the development of novel cell therapies. OBJECTIVES: This study sought to systematically evaluate signaling pathways to develop a refined direct differentiation protocol that generates patient-derived thymic epithelial progenitor cells from multiple induced pluripotent stem cells (iPSCs) that can further differentiate into functional patient-derived thymic epithelial cells on transplantation into athymic nude mice. METHODS: Directed differentiation of iPSC generated TEPs that were transplanted into nude mice. Between 14 and 19 weeks posttransplantation, grafts were removed and analyzed by flow cytometry, quantitative PCR, bulk RNA sequencing, and single-cell RNA sequencing for markers of thymic-cell and T-cell development. RESULTS: A direct differentiation protocol that allows the generation of patient-derived thymic epithelial progenitor cells from multiple iPSC lines is described. On transplantation into athymic nude mice, patient-derived thymic epithelial progenitor cells further differentiate into functional patient-derived thymic epithelial cells that can facilitate the development of T cells. Single-cell RNA sequencing analysis of iPSC-derived grafts shows characteristic thymic subpopulations and patient-derived thymic epithelial cell populations that are indistinguishable from TECs present in primary neonatal thymus tissue. CONCLUSIONS: These findings provide important insights and resources for researchers focusing on human thymus biology.

ENTPD3 Marks Mature Stem Cell-Derived ß-Cells Formed by Self-Aggregation In Vitro.

Stem cell-derived ß-like cells (sBC) carry the promise of providing an abundant source of insulin-producing cells for use in cell replacement therapy for patients with diabetes, potentially allowing widespread implementation of a practical cure. To achieve their clinical promise, sBC need to function comparably with mature adult ß-cells, but as yet they display varying degrees of maturity. Indeed, detailed knowledge of the events resulting in human ß-cell maturation remains obscure. Here we show that sBC spontaneously self-enrich into discreet islet-like cap structures within in vitro cultures, independent of exogenous maturation conditions. Multiple complementary assays demonstrate that this process is accompanied by functional maturation of the self-enriched sBC (seBC); however, the seBC still contain distinct subpopulations displaying different maturation levels. Interestingly, the surface protein ENTPD3 (also known as nucleoside triphosphate diphosphohydrolase-3 [NDPTase3]) is a specific marker of the most mature seBC population and can be used for mature seBC identification and sorting. Our results illuminate critical aspects of in vitro sBC maturation and provide important insights toward developing functionally mature sBC for diabetes cell replacement therapy.

Amylin, Aß42, and Amyloid in Varicella Zoster Virus Vasculopathy Cerebrospinal Fluid and Infected Vascular Cells.

BACKGROUND: Varicella zoster virus (VZV) vasculopathy is characterized by persistent arterial inflammation leading to stroke. Studies show that VZV induces amyloid formation that may aggravate vasculitis. Thus, we determined if VZV central nervous system infection produces amyloid. METHODS: Aß peptides, amylin, and amyloid were measured in cerebrospinal fluid (CSF) from 16 VZV vasculopathy subjects and 36 stroke controls. To determine if infection induced amyloid deposition, mock- and VZV-infected quiescent primary human perineurial cells (qHPNCs), present in vasculature, were analyzed for intracellular amyloidogenic transcripts/proteins and amyloid. Supernatants were assayed for amyloidogenic peptides and ability to induce amyloid formation. To determine amylin's function during infection, amylin was knocked down with small interfering RNA and viral complementary DNA (cDNA) was quantitated. RESULTS: Compared to controls, VZV vasculopathy CSF had increased amyloid that positively correlated with amylin and anti-VZV antibody levels; Aß40 was reduced and Aß42 unchanged. Intracellular amylin, Aß42, and amyloid were seen only in VZV-infected qHPNCs. VZV-infected supernatant formed amyloid fibrils following addition of amyloidogenic peptides. Amylin knockdown decreased viral cDNA. CONCLUSIONS: VZV infection increased levels of amyloidogenic peptides and amyloid in CSF and qHPNCs, indicating that VZV-induced amyloid deposition may contribute to persistent arterial inflammation in VZV vasculopathy. In addition, we identified a novel proviral function of amylin.