Islet Cell Differentiation Research Articles

348-OR: Differentiation of Adult Islet Cell Precursors into ß- and α-like Cells for Islet Transplantation

Advances in protocols to convert human embryonic and inducible pluripotent stem cells (hESCs and iPSCs) into pancreatic β cells has allowed us to generate islet cell organoids in culture for potential use in islet cell transplantation. Here, we demonstrate that dedifferentiated β cells and/or NGN-/RGS16+ islet cell precursors (ICPs) can be harvested from adult pancreatic tissue and converted into β- and α-like cells. In this study, we used ICPs derived from COBE bag pancreatic tissue remnants from organ donors to produce islet cell organoids capable of releasing both insulin and glucagon in response to high (16.7 mM) and low (2.8 mM) glucose conditions, respectively. These organoids displayed zinc-containing granule staining by dithizone and exhibited GSIS with stimulation indices comparable to human islets. ICPs produced genetic profiles similar to hESC-derived endocrine progenitor cells at stages 5-7 (S5-7). Using small molecule ISX9 and GSK/DYRK inhibitors GNF and harmine to induce and activate calcineurin (CN)/NFAT signaling, we were able to expand and differentiate ICPs into β- and α-like cells. CN/NFAT upregulated genes that promote cell cycle and proliferation (S5) and islet cell differentiation genes (S5-7). Islet cell type fate and function could be modulated by hedgehog/GLI signaling. Whereas introduction of sonic hedgehog (Shh) inhibitor SANT-1 at S5 favored production of β-like cells, Shh signaling agonists promoted differentiation to α-like cells up to S7. Overall, these results indicate that adult ICPs can be harvested from donor tissue and expanded for differentiation into functional β- and α-like cells. The capability to expand and differentiate adult ICPs could potentially provide an unlimited supply of islet organoid tissue for islet cell transplantation. Disclosure C.Darden: None. J.Kuncha: None. J.D.Mattke: None. B.Naziruddin: None. M.C.Lawrence: None. Funding Baylor Scott & White Health

Improving stem cell-derived pancreatic islets using single-cell multi-inferred regulomes.

In this issue of Developmental Cell, Zhu etal. provide integrated data from single-cell/nuclei RNAseq and chromatin accessibility (ATAC) across both a multistaged differentiation protocol-deriving pancreatic islets from hESCs and primary islets. This important resource could be leveraged for optimizing the differentiation and maturation of pancreatic islet cells from hESCs.

Transplantation of insulin-producing cells derived from human MSCs to treat diabetes in a non-human primate model.

Islet cell transplantation is an emerging therapy in the treatment of diabetes mellitus. Differentiation of islet cells from mesenchymal stem cells (MSCs) is a potential solution to the challenge of insufficient donor sources. This study investigated whether human umbilical cord-derived MSCs could effectively differentiate into insulin-producing cells (IPCs) and evaluated the therapeutic efficacy of IPCs in treating diabetes. IPCs were induced from MSCs by a two-step protocol. IPC expression products were evaluated by western blot and real-time PCR. IPC insulin secretion was evaluated by ELISA. The viability of IPCs was measured by FDA/PI and dithizone staining. The non-human primate tree shrew was used as a diabetes model. After a single STZ induction into a diabetes model, a single intraportal transplantation of IPCs, MSCs, or normal saline was performed (n = 6 per group). Blood glucose was monitored for 3 weeks, then the animals were euthanized and the distribution of IPCs in the liver was examined pathologically. After about 3 weeks of in vitro induction, IPCs formed microspheres of 100-200 μm, with >95% viable cells that were dithizone stain positive. IPCs expressed islet-related genes and proteins and secreted high levels of insulin whether stimulated by low or high levels of glucose. After transplantation of IPCs into diabetic tree shrews, blood glucose levels decreased rapidly to near normal and were significantly lower than the MSC or saline groups for 3 weeks thereafter. We present the novel discovery that IPCs derived from human umbilical cord MSCs exert a therapeutic effect in a non-human primate model of diabetes. This study provides a preliminary experimental basis for the use of autologous MSC-derived IPCs in the treatment of human diabetes.

Lama2 And Samsn1 Mediate the Effects of Brn4 on Hippocampal Neural Stem Cell Proliferation and Differentiation.

The transcription factor Brn4 exhibits vital roles in the embryonic development of the neural tube, inner ear, pancreas islet, and neural stem cell differentiation. Our previous studies have shown that Brn4 promotes neuronal differentiation of hippocampal neural stem cells (NSCs). However, its mechanism is still unclear. Here, starting from the overlapping genes between RNA-seq and ChIP-seq results, we explored the downstream target genes that mediate Brn4-induced hippocampal neurogenesis. There were 16 genes at the intersection of RNA-seq and ChIP-seq, among which the Lama2 and Samsn1 levels can be upregulated by Brn4, and the combination between their promoters and Brn4 was further determined using ChIP and dual luciferase reporter gene assays. EdU incorporation, cell cycle analysis, and CCK-8 assay indicated that Lama2 and Samsn1 mediated the inhibitory effect of Brn4 on the proliferation of hippocampal NSCs. Immunofluorescence staining, RT-qPCR, and Western blot suggested that Lama2 and Samsn1 mediated the promoting effect of Brn4 on the differentiation of hippocampal NSCs into neurons. In conclusion, our study demonstrates that Brn4 binds to the promoters of Lama2 and Samsn1, and they partially mediate the regulation of Brn4 on the proliferation inhibition and neuronal differentiation promotion of hippocampal NSCs.

Prolactin receptor signaling: A novel target for cancer treatment - Exploring anti-PRLR signaling strategies.

Prolactin (PRL) is a peptide hormone mainly secreted from the anterior pituitary gland. PRL is reported to play a role in pregnancy, mammary gland development, immune modulation, reproduction, and differentiation of islet cells. PRL binds to its receptor PRLR, which belongs to a superfamily of the class I cytokine receptor that has no intrinsic kinase activity. In canonical signaling, PRL binding to PRLR induces downstream signaling including JAK-STAT, AKT and MAPK pathways. This leads to increased cell proliferation, stemness, migration, apoptosis inhibition, and resistance to chemotherapy. PRL-signaling is upregulated in numerous hormone-dependent cancers including breast, prostate, ovarian, and endometrial cancer. However, more recently, the pathway has been reported to play a tumor-promoting role in other cancer types such as colon, pancreas, and hepatocellular cancers. Hence, the signaling pathway is an attractive target for drug development with blockade of the receptor being a potential therapeutic approach. Different strategies have been developed to target this receptor including modification of PRL peptides (Del1-9-G129R-hPRL, G129R-Prl), growth hormone receptor/prolactin receptor bispecific antibody antagonist, neutralizing antibody LFA102, an antibody-drug conjugate (ABBV-176) of the humanized antibody h16f (PR-1594804) and pyrrolobenzodiazepine dimer, a bispecific antibody targeting both PRLR and CD3, an in vivo half-life extended fusion protein containing PRLR antagonist PrlRA and albumin binding domain. There have also been attempts to discover and develop small molecular inhibitors targeting PRLR. Recently, using structure-based virtual screening, we identified a few antipsychotic drugs including penfluridol as a molecule that inhibits PRL-signaling to inhibit PDAC tumor progression. In this review, we will summarize the recent advances in the biology of this receptor in cancer and give an account of PRLR antagonist development for the treatment of cancer.

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

BackgroundTransplantation of differentiated cells from human-induced pluripotent stem cells (hiPSCs) holds great promise for clinical treatments. Eliminating the risk factor of malignant cell transformation is essential for ensuring the safety of such cells. This study was aimed at assessing and mitigating mutagenicity that may arise during the cell culture process in the protocol of pancreatic islet cell (iPIC) differentiation from hiPSCs.MethodsWe evaluated the mutagenicity of differentiation factors used for hiPSC-derived pancreatic islet-like cells (iPICs). We employed Ames mutagenicity assay, flow cytometry analysis, immunostaining, time-resolved fluorescence resonance energy transfer-based (TR-FRET) cell-free dose–response assays, single-cell RNA-sequencing and in vivo efficacy study.ResultsWe observed a mutagenic effect of activin receptor-like kinase 5 inhibitor II (ALK5iII). ALK5iII is a widely used β-cell inducer but no other tested ALK5 inhibitors induced β-cells. We obtained kinase inhibition profiles and found that only ALK5iII inhibited cyclin-dependent kinases 8 and 19 (CDK8/19) among all ALK5 inhibitors tested. Consistently, CDK8/19 inhibitors efficiently induced β-cells in the absence of ALK5iII. A combination treatment with non-mutagenic ALK5 inhibitor SB431542 and CDK8/19 inhibitor senexin B afforded generation of iPICs with in vitro cellular composition and in vivo efficacy comparable to those observed with ALK5iII.ConclusionOur findings suggest a new risk mitigation approach for cell therapy and advance our understanding of the β-cell differentiation mechanism.

Role of poly(ADP-ribose) polymerase-1 in regulating human islet cell differentiation

Poly(ADP-ribose) polymerase-1 (PARP1), a fundamental DNA repair enzyme, is known to regulate β cell death, replication, and insulin secretion. PARP1 knockout (KO) mice are resistant to diabetes, while PARP1 overactivation contributes to β cell death. Additionally, PARP1 inhibition (PARPi) improves diabetes complications in patients with type-2 diabetes. Despite these beneficial effects, the use of PARP1 modulating agents in diabetes treatment is largely neglected, primarily due to the poorly studied mechanistic action of PARP1 catalytic function in human β cell development. In the present study, we evaluated PARP1 regulatory action in human β cell differentiation using the human pancreatic progenitor cell line, PANC-1. We surveyed islet census and histology from PARP1 wild-type versus KO mice pancreas in a head-to-head comparison with PARP1 regulatory action for in-vitro β cell differentiation following either PARP1 depletion or its pharmacological inhibition in PANC-1-differentiated islet cells. shRNA mediated PARP1 depleted (SiP) and shRNA control (U6) PANC-1 cells were differentiated into islet-like clusters using established protocols. We observed complete abrogation of new β cell formation with absolute PARP1 depletion while its inhibition using the potent inhibitor, PJ34, promoted the endocrine β cell differentiation and maturation. Immunohistochemistry and immunoblotting for key endocrine differentiation players along with β cell maturation markers highlighted the potential regulatory action of PARP1 and augmented β cell differentiation due to direct interaction of unmodified PARP1 protein elicited p38 MAPK phosphorylation and Neurogenin-3 (Ngn3) re-activation. In summary, our study suggests that PARP1 is required for the proper development and differentiation of human islets. Selective inhibition with PARPi can be an advantage in pushing more insulin-producing cells under pathological conditions and delivers a potential for pilot clinical testing for β cell replacement cell therapies for diabetes.

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

Recapitulation of embryonic pancreatic development has enabled development of methods for invitro 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.

183-OR: Overcoming Immunological Barriers for “Off-the-Shelf” iPSC-Derived Islets

Improved differentiation protocols allow large-scale generation of induced pluripotent stem cell (iPSC) -derived islets. In order to make allogeneic “off-the-shelf” islets clinically useful and avoid rejection absent immunosuppression (IS) , they need to evade host immune responses, a property we refer to as being “hypoimmune.” Rhesus macaque (NHP) iPSCs were engineered to knock-out function of MHC class I and II and overexpress CD47 (HIP iPSCs) . HIP iPSCs and unedited iPSCs (wt iPSCs) were transduced to express luciferase and transplanted IM into four allogeneic NHPs per group. There was a strong IFN-γ ELISpot T cell response 1 week after wt iPSC transplantation, and increased production of wt-iPSC specifc IgM antibodies (Ab) and IgG Abs. At all time points tested (up to 12 weeks) , PBMCs killed wt iPSCs via direct and Ab-mediated cellular cytotoxicity. Furthermore, serum from NHPs killed wt iPSCs via complement-dependent cytotoxicity. In contrast, NHPs that received HIP iPSCs showed no measurable immune response against HIP iPSCs at all time points. After 6 weeks, NHPs initially receiving wt iPSCs were injected with HIP iPSCs. Although the NHPs maintained their strong immune response against wt iPSCs, they did not mount any response against HIP iPSCs. NHPs receiving HIP iPSCs first developed a strong cellular and Ab-response against the subsequently injected wt iPSCs but continued to have no reactivity against HIP iPSCs. Bioluminescence imaging in vivo revealed rejection of all wt iPSC grafts in both groups within 2-3 weeks after transplantation, while all HIP iPSC grafts survived the study period of 16 weeks. As a step to extending these studies to human iPSCs, we created human HIP iPSCs. We were able to differentiate these human HIP iPSCs into functional HIP islet cells that evaded host immune responses. This work suggests that HIP modifications do not impact islet cell differentiation or function. These data support the development of allogeneic HIP islets for the treatment of patients with T1DM. Disclosure X.Hu: None. F.Wells: None. T.Mcgill: Employee; Sana Biotechnology Inc. M.Rukstalis: Employee; Sana Biotechnology Inc. C.Gattis: None. R.Basco: None. J.R.Millman: Consultant; Sana Biotechnology Inc., Other Relationship; Sana Biotechnology Inc., Vertex Pharmaceuticals Incorporated, Research Support; Sana Biotechnology Inc., Stock/Shareholder; Salentra Biosciences. S.Schrepfer: Other Relationship; Sana Biotechnology Inc. K.White: None. A.G.Olroyd: None. R.Dejesus: None. A.Dominguez: Employee; Sana Biotechnology Inc. W.E.Dowdle: Employee; Sana Biotechnology Inc., Stock/Shareholder; Sana Biotechnology Inc. E.Y.L.Chu: None. A.Friera: None. C.Young: Employee; Sana Biotechnology Inc.

Adult pancreatic islet endocrine cells emerge as fetal hormone-expressing cells.

SummaryThe precise developmental dynamics of the pancreatic islet endocrine cell types, and their interrelation, are unknown. Some authors claim the persistence of islet cell differentiation from precursor cells after birth (“neogenesis”). Here, using four conditional cell lineage tracing (“pulse-and-chase”) murine models, we describe the natural history of pancreatic islet cells, once they express a hormone gene, until late in life. Concerning the contribution of early-appearing embryonic hormone-expressing cells to the formation of islets, we report that adult islet cells emerge from embryonic hormone-expressing cells arising at different time points during development, without any evidence of postnatal neogenesis. We observe specific patterns of hormone gene activation and switching during islet morphogenesis, revealing that, within each cell type, cells have heterogeneous developmental trajectories. This likely applies to most maturating cells in the body, and explains the observed phenotypic variability within differentiated cell types. Such knowledge should help devising novel regenerative therapies.

209.2: Engineering Immune-evasive Human Stem Cell-derived Islet Cells

Introduction: Protection against the human immune system is required to realize the therapeutic potential of stem cell (SC)-islet cells for the treatment of type 1 diabetes. Various groups have attempted to address this challenge by engineering immune-evasive human embryonic stem cells (hESCs) that can be differentiated into various cell types. In many cases, over-expression of the tolerogenic molecules at safe harbor loci is lost due to transgene silencing. We recently addressed this issue by targeting Firefly luciferase (Luc2) to the constitutively expressed GAPDH locus of hESCs (GAPluc), followed by successful differentiation into SC-islet cells that maintain Luc2 expression. Thus, in this study we used a similar engineering strategy to generate hypoimmunogenic SC-islet cells. Methods: Using CRISPR/Cas9 we introduced Luc2 and the B2M::HLA-E fusion to the GAPDH locus of hESCs, followed by CRISPR knockout of endogenous B2M to eliminate class I HLA expression. Using sequential antibiotic selection of GAPDH-targeted and FACS sorting of HLA-ABC-/- hESCs, we generated a hypoimmunogenic hESC line (BEC) that was differentiated into SC-islet cells. SC-islet cell immunogenicity was assessed in in vitro PBMC and NK cell co-culture assays using cells isolated from allogeneic human peripheral blood (n=5 donors), with Luc2 expression serving as a reporter of cell viability. Wild-type (WT) and B2M-/- SC-islet cells served as controls. To assess SC-islet cell survival in vivo, 5x106 WT and BEC SC-islet cells were transplanted under the kidney capsule of HLA-A2 mismatched humanized NSG-(Kb Db)null (IAnull) mice (n=4/group). Graft survival was assessed via bioluminescence imaging using the IVIS Spectrum. Results: Differentiation of WT, B2M-/- and BEC hESCs into SC-islet cells resulted in a similar yield (~20%) of Nkx6.1+/C-peptide+ SC-beta cells. HLA-E and Luc2 expression correlated throughout the course of differentiation, with a ~10-fold decrease in expression in hESCs vs CD49a-enriched SC-beta cells. No significant difference in Luc2 expression was observed in CD49a-enriched SC-beta cells derived from all gene-modified hESC lines. In in vitro PBMC co-culture assays, B2M-/- and BEC SC-islet cells were significantly protected from PBMC cytotoxicity by comparison to WT. In in vitro NK cell co-culture assays, BEC SC-islet cells were significantly protected against NK cell cytotoxicity by comparison to B2M-/-. Additionally, following transplant into the kidney capsule of humanized NSG-(Kb Db)null (IAnull) mice, BEC SC-islet cells showed a significant survival advantage by comparison to WT at 35 days post transplantation. Conclusion: In this study we show that targeting transgenes to constitutively expressed loci results in persistent transgene expression throughout the course of islet cell differentiation. Furthermore, our engineering strategy resulted in the generation of hypoimmunogenic SC-islet cells that evade immune rejection both in vitro and in vivo.

Butyrate and Class I Histone Deacetylase Inhibitors Promote Differentiation of Neonatal Porcine Islet Cells into Beta Cells.

Neonatal porcine islets-like clusters (NPICCs) are a promising source for cell therapy of type 1 diabetes. Freshly isolated NPICCs are composed of progenitor cells and endocrine cells, which undergo a maturation process lasting several weeks until the normal beta cell function has developed. Here, we investigated the effects of short-chain fatty acids on the maturation of islet cells isolated from two to three day-old piglets. NPICCs were cultivated with acetate, butyrate and propionate (0–2000 µM) for one to eight days. Incubation with butyrate resulted in a significant upregulation of insulin gene expression and an increased beta cell number, whereas acetate or propionate had only marginal effects. Treatment with specific inhibitors of G-protein-coupled receptor GPR41 (β-hydroxybutyrate) and/or GPR43 (GPLG0974) did not abolish butyrate induced insulin expression. However, incubation of NPICCs with class I histone deacetylase inhibitors (HDACi) mocetinostat and MS275, but not selective class II HDACi (TMP269, MC1568) mimicked the butyrate effect on beta cell differentiation. Our study revealed that butyrate treatment has the capacity to increase the number of beta cells, which may be predominantly mediated through its HDAC inhibitory activity. Butyrate and specific class I HDAC inhibitors may represent beneficial supplements to promote differentiation of neonatal porcine islet cells towards beta cells for cell replacement therapies.

A Comparative Endocrine Trans-Differentiation Approach to Pancreatic Ductal Adenocarcinoma Cells with Different EMT Phenotypes Identifies Quasi-Mesenchymal Tumor Cells as Those with Highest Plasticity.

Simple SummaryPancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancer types with the quasi-mesenchymal (QM) subtype of PDAC having the worst prognosis. De-differentiation of the ductal tumor cells to a mesenchymal phenotype occurs as a result of epithelial–mesenchymal transition (EMT), a process associated with the acquisition of stem cell traits. While QM tumor cells are highly metastatic and drug-resistant, their increased plasticity opens a window of opportunity for trans-differentiation into non-malignant pancreatic cells. In this study we compared established PDAC-derived cell lines of either epithelial (E) or QM phenotype for their potential to be differentiated to pancreatic endocrine cells. We found that QM cells responded more strongly than E cells with transcriptional activation of a pancreatic progenitor or pancreatic β cell-specific program. Our results bear strong implications for a novel type of targeted therapy, namely EMT-based trans-differentiation of highly metastatic PDAC cells in vivo to non-malignant endocrine cells.Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and therapy-resistant cancer types which is largely due to tumor heterogeneity, cancer cell de-differentiation, and early metastatic spread. The major molecular subtypes of PDAC are designated classical/epithelial (E) and quasi-mesenchymal (QM) subtypes, with the latter having the worst prognosis. Epithelial–mesenchymal transition (EMT) and the reverse process, mesenchymal-epithelial transition (MET), are involved in regulating invasion/metastasis and stem cell generation in cancer cells but also early pancreatic endocrine differentiation or de-differentiation of adult pancreatic islet cells in vitro, suggesting that pancreatic ductal exocrine and endocrine cells share common EMT programs. Using a panel of PDAC-derived cell lines classified by epithelial/mesenchymal expression as either E or QM, we compared their trans-differentiation (TD) potential to endocrine progenitor or β cell-like cells since studies with human pancreatic cancer cells for possible future TD therapy in PDAC patients are not available so far. We observed that QM cell lines responded strongly to TD culture using as inducers 5′-aza-2′-deoxycytidine or growth factors/cytokines, while their E counterparts were refractory or showed only a weak response. Moreover, the gain of plasticity was associated with a decrease in proliferative and migratory activities and was directly related to epigenetic changes acquired during selection of a metastatic phenotype as revealed by TD experiments using the paired isogenic COLO 357-L3.6pl model. Our data indicate that a QM phenotype in PDAC coincides with increased plasticity and heightened trans-differentiation potential to activate a pancreatic β cell-specific transcriptional program. We strongly assume that this specific biological feature has potential to be exploited clinically in TD-based therapy to convert metastatic PDAC cells into less malignant or even benign cells.

Activation of Pancreatic Stellate Cells Is Beneficial for Exocrine but Not Endocrine Cell Differentiation in the Developing Human Pancreas.

Pancreatic stellate cells (PaSCs) are non-endocrine, mesenchymal-like cells that reside within the peri-pancreatic tissue of the rodent and human pancreas. PaSCs regulate extracellular matrix (ECM) turnover in maintaining the integrity of pancreatic tissue architecture. Although there is evidence indicating that PaSCs are involved in islet cell survival and function, its role in islet cell differentiation during human pancreatic development remains unclear. The present study examines the expression pattern and functional role of PaSCs in islet cell differentiation of the developing human pancreas from late 1st to 2nd trimester of pregnancy. The presence of PaSCs in human pancreata (8–22 weeks of fetal age) was characterized by ultrastructural, immunohistological, quantitative RT-PCR and western blotting approaches. Using human fetal PaSCs derived from pancreata at 14–16 weeks, freshly isolated human fetal islet-epithelial cell clusters (hIECCs) were co-cultured with active or inactive PaSCs in vitro. Ultrastructural and immunofluorescence analysis demonstrated a population of PaSCs near ducts and newly formed islets that appeared to make complex cell-cell dendritic-like contacts. A small subset of PaSCs co-localized with pancreatic progenitor-associated transcription factors (PDX1, SOX9, and NKX6-1). PaSCs were highly proliferative, with significantly higher mRNA and protein levels of PaSC markers (desmin, αSMA) during the 1st trimester of pregnancy compared to the 2nd trimester. Isolated human fetal PaSCs were identified by expression of stellate cell markers and ECM. Suppression of PaSC activation, using all-trans retinoic acid (ATRA), resulted in reduced PaSC proliferation and ECM proteins. Co-culture of hIECCs, directly on PaSCs or indirectly using Millicell® Inserts or using PaSC-conditioned medium, resulted in a reduction the number of insulin+ cells but a significant increase in the number of amylase+ cells. Suppression of PaSC activation or Notch activity during the co-culture resulted in an increase in beta-cell differentiation. This study determined that PaSCs, abundant during the 1st trimester of pancreatic development but decreased in the 2nd trimester, are located near ductal and islet structures. Direct and indirect co-cultures of hIECCs with PaSCs suggest that activation of PaSCs has opposing effects on beta-cell and exocrine cell differentiation during human fetal pancreas development, and that these effects may be dependent on Notch signaling.

Extensive NEUROG3 occupancy in the human pancreatic endocrine gene regulatory network

ObjectiveMice lacking the bHLH transcription factor (TF) Neurog3 do not form pancreatic islet cells, including insulin-secreting beta cells, the absence of which leads to diabetes. In humans, homozygous mutations of NEUROG3 manifest with neonatal or childhood diabetes. Despite this critical role in islet cell development, the precise function of and downstream genetic programs regulated directly by NEUROG3 remain elusive. Therefore, we mapped genome-wide NEUROG3 occupancy in human induced pluripotent stem cell (hiPSC)–derived endocrine progenitors and determined NEUROG3 dependency of associated genes to uncover direct targets. MethodsWe generated a novel hiPSC line (NEUROG3-HA-P2A-Venus) where NEUROG3 is HA-tagged and fused to a self-cleaving fluorescent VENUS reporter. We used the CUT&RUN technique to map NEUROG3 occupancy and epigenetic marks in pancreatic endocrine progenitors (PEP) that were differentiated from this hiPSC line. We integrated NEUROG3 occupancy data with chromatin status and gene expression in PEPs as well as their NEUROG3-dependence. In addition, we investigated whether NEUROG3 binds type 2 diabetes mellitus (T2DM)–associated variants at the PEP stage. ResultsCUT&RUN revealed a total of 863 NEUROG3 binding sites assigned to 1263 unique genes. NEUROG3 occupancy was found at promoters as well as at distant cis-regulatory elements that frequently overlapped within PEP active enhancers. De novo motif analyses defined a NEUROG3 consensus binding motif and suggested potential co-regulation of NEUROG3 target genes by FOXA or RFX transcription factors. We found that 22% of the genes downregulated in NEUROG3−/− PEPs, and 10% of genes enriched in NEUROG3-Venus positive endocrine cells were bound by NEUROG3 and thus likely to be directly regulated. NEUROG3 binds to 138 transcription factor genes, some with important roles in islet cell development or function, such as NEUROD1, PAX4, NKX2-2, SOX4, MLXIPL, LMX1B, RFX3, and NEUROG3 itself, and many others with unknown islet function. Unexpectedly, we uncovered that NEUROG3 targets genes critical for insulin secretion in beta cells (e.g., GCK, ABCC8/KCNJ11, CACNA1A, CHGA, SCG2, SLC30A8, and PCSK1). Thus, analysis of NEUROG3 occupancy suggests that the transient expression of NEUROG3 not only promotes islet destiny in uncommitted pancreatic progenitors, but could also initiate endocrine programs essential for beta cell function. Lastly, we identified eight T2DM risk SNPs within NEUROG3-bound regions. ConclusionMapping NEUROG3 genome occupancy in PEPs uncovered unexpectedly broad, direct control of the endocrine genes, raising novel hypotheses on how this master regulator controls islet and beta cell differentiation.

177-OR: The Swi/Snf Chromatin Remodeling Complex Controls the Specification, Expansion, and Differentiation of Pancreatic Endocrine Progenitor Cells

A key feature of type 1 and type 2 diabetes is insufficient functional β-cell mass. Strategies to augment functional β-cell mass include directed differentiation of embryonic stem cells towards a β-cell fate, which requires extensive knowledge of the transcriptional programs governing endocrine cell differentiation in vivo. Pdx1, an essential transcription factor involved in pancreas formation, endocrine progenitor cell expansion and β-cell function, dynamically recruits coregulators to drive gene expression programs in those cells vital for its activity. Pdx1 binds to numerous coregulators in the β-cell, including the ATP-dependent Swi/Snf chromatin remodeling complex. Previous work by our group revealed a critical role for Pdx1:Swi/Snf in both the developing pancreas and mature β-cell. Here we interrogate the role of Swi/Snf on governing Pdx1-dependent gene expression programs and chromatin accessibility in pancreatic endocrine cell development. We developed a mouse model to eliminate the activity of the two core ATPase subunits of Swi/Snf, Brg1 and Brm from endocrine progenitor cells using Neurogenin3-Cre (Δendo). Conditional knockout of Brg1 (Brg1ΔendoBrm+/-) from endocrine progenitor cells leads to severe glucose intolerance, ad-libitum fed hyperglycemia, reduced serum insulin, compromised glucose stimulated insulin secretion from isolated islets and reduced islet mass in 4-week old animals. Whereas Brg1Δendo/+Brm-/- mice are normal, remarkably, no DKOΔendo (double knockout (DKO): targeted both Brg1 and Brm) mice have been found at weaning, suggesting loss of all Swi/Snf activity from the endocrine progenitor cell pool is postnatally lethal. Future experiments will be directed at determining how Swi/Snf controls Pdx1-dependent gene expression programs and chromatin accessibility in endocrine progenitor cells that are critical for islet cell expansion, differentiation and maturation. Disclosure J. Spaeth: None. R. K. Davidson: None. N. Casey: None. Funding National Institutes of Health (R03DK127129, K01DK115633)

Tracing the cellular basis of islet specification in mouse pancreas

Pancreatic islets play an essential role in regulating blood glucose level. Although the molecular pathways underlying islet cell differentiation are beginning to be resolved, the cellular basis of islet morphogenesis and fate allocation remain unclear. By combining unbiased and targeted lineage tracing, we address the events leading to islet formation in the mouse. From the statistical analysis of clones induced at multiple embryonic timepoints, here we show that, during the secondary transition, islet formation involves the aggregation of multiple equipotent endocrine progenitors that transition from a phase of stochastic amplification by cell division into a phase of sublineage restriction and limited islet fission. Together, these results explain quantitatively the heterogeneous size distribution and degree of polyclonality of maturing islets, as well as dispersion of progenitors within and between islets. Further, our results show that, during the secondary transition, α- and β-cells are generated in a contemporary manner. Together, these findings provide insight into the cellular basis of islet development.

Enzymatically stable analogue of the gut-derived peptide xenin on beta-cell transdifferentiation in high fat fed and insulin-deficient Ins1Cre/+ ;Rosa26-eYFP mice.

The antidiabetic effects of the gut hormone xenin include augmenting insulin secretion and positively affecting pancreatic islet architecture. The current study has further probed pancreatic effects through sub-chronic administration of the long-acting xenin analogue, xenin-25[Lys13 PAL], in both high fat fed (HFF) and streptozotocin (STZ)-induced insulin-deficient Ins1Cre/+ ;Rosa26-eYFP transgenic mice. Parallel effects on metabolic control and pancreatic islet morphology, including islet beta-cell lineage tracing were also assessed. Xenin-25[Lys13 PAL] treatment reversed body weight loss induced by STZ, increased plasma insulin and decreased blood glucose levels. There were less obvious effects on these parameters in HFF mice, but all xenin-25[Lys13 PAL] treated mice exhibited decreased pancreatic alpha-cell areas and circulating glucagon. Xenin-25[Lys13 PAL] treatment fully, or partially, returned overall islet and beta-cell areas in STZ- and HFF mice to those of lean control animals, respectively, and was consistently associated with decreased beta-cell apoptosis. Interestingly, xenin-25[Lys13 PAL] also increased beta-cell proliferation and decreased alpha-cell apoptosis in STZ mice, with reduced alpha-cell growth noted in HFF mice. Lineage tracing studies revealed that xenin-25[Lys13 PAL] reduced the number of insulin positive pancreatic islet cells that lost their beta-cell identity, in keeping with a decreased transition of insulin positive to glucagon positive cells. These beneficial effects on islet cell differentiation were linked to maintained expression of Pdx1 within beta-cells. Xenin-25[Lys13 PAL] treatment was also associated with increased numbers of smaller sized islets in both models. Benefits of xenin-25[Lys13 PAL] on diabetes includes positive modulation of islet cell differentiation, in addition to promoting beta-cell growth and survival.

Control of Hyperglycemia Using Differentiated and Undifferentiated Mesenchymal Stem Cells in Rats with Type 1 Diabetes

Due to their ability in self-renewing and differentiation into a wide variety of tissues, mesenchymal stem cells (MSCs) exhibit outstanding potential for regenerative medicine. This study was aimed at investigating different aspects of MSC therapy in controlling hyperglycemia in streptozotocin-induced diabetes rats. Using an islet cell differentiation protocol, bone marrow (BM) MSCs were differentiated into insulin-producing cells (IPCs). The differentiation process was evaluated by immunocytochemistry, reverse transcriptase PCR, and dithizone staining. Diabetic animals in 4 diabetic individual groups received normal saline, BM-MSCs, coadministration of BM-MSCs with supernatant, and IPCs. Blood glucose and insulin levels were monitored during the experiment. Immunohistochemical analysis of the pancreas was performed at the end of the experiment. Administration of BM-MSCs could not reverse glucose and insulin levels in experimental animals as efficiently as cotransplantation of BM-MSCs with supernatant. The effect of coadministration of BM-MSCs with supernatant and transplantation of IPCs on controlling hyperglycemia is comparable. Immunohistochemical analysis showed that number and size of islets per section were significantly increased in groups receiving IPCs and BM-MSC-supernatant compared to the MSC group of animals. In conclusion, coadministration of BM-MSCs with supernatant could be used as efficiently as IPC transplantation in controlling hyperglycemia in diabetic rats.

Charting cellular identity during human in vitro β-cell differentiation.

In vitro differentiation of human stem cells can produce pancreatic β-cells; the loss of this insulin-secreting cell type underlies type 1 diabetes. Here, as a step towards understanding this differentiation process, we report the transcriptional profiling of more than 100,000 human cells undergoing in vitro β-cell differentiation, and describe the cells that emerged. We resolve populations that correspond to β-cells, α-like poly-hormonal cells, non-endocrine cells that resemble pancreatic exocrine cells and a previously unreported population that resembles enterochromaffin cells. We show that endocrine cells maintain their identity in culture in the absence of exogenous growth factors, and that changes in gene expression associated with in vivo β-cell maturation are recapitulated in vitro. We implement a scalable re-aggregation technique to deplete non-endocrine cells and identify CD49a (also known as ITGA1) as a surface marker of the β-cell population, which allows magnetic sorting to a purity of 80%. Finally, we use a high-resolution sequencing time course to characterize gene-expression dynamics during the induction of human pancreatic endocrine cells, from which we develop a lineage model of in vitro β-cell differentiation. This study provides a perspective on human stem-cell differentiation, and will guide future endeavours that focus on the differentiation of pancreatic islet cells, and theirapplications in regenerative medicine.