Differentiation Of Pancreatic Islet Cells Research Articles

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.

Amniotic membrane-derived stem cells and pancreatic islet-cell differentiation

Amniotic membrane-derived stem cells and pancreatic islet-cell differentiation

Generation of pancreatic islet cells from human embryonic stem cells

Efficiently obtaining functional pancreatic islet cells derived from human embryonic stem (hES) cells not only provides great potential to solve the shortage of islets sources for type I diabetes cell therapy, but also benefits the study of the development of the human pancreas and diabetes pathology. In 2001, hES cells were reported to have the capacity to generate insulin-producing cells by spontaneous differentiation in vitro. Since then, many strategies (such as overexpression of key transcription factors, delivery of key proteins for pancreatic development, co-transplantation of differentiated hES cells along with fetal pancreas, stepwise differentiation by mimicking in vivo pancreatic development) have been employed in order to induce the differentiation of pancreatic islet cells from hES cells. Moreover, patient-specific induced pluripotent stem (iPS) cells can be generated by reprogramming somatic cells. iPS cells have characteristics similar to those of ES cells and offer a new cell source for type I diabetes cell therapy that reduces the risk of immunologic rejection. In this review, we summarize the recent progress made in the differentiation of hES and iPS cells into functional pancreatic islet cells and discuss the challenges for their future study.

Chronology of Islet Differentiation Revealed By Temporal Cell Labeling

OBJECTIVENeurogenin 3 plays a pivotal role in pancreatic endocrine differentiation. Whereas mouse models expressing reporters such as eGFP or LacZ under the control of the Neurog3 gene enable us to label cells in the pancreatic endocrine lineage, the long half-life of most reporter proteins makes it difficult to distinguish cells actively expressing neurogenin 3 from differentiated cells that have stopped transcribing the gene.RESEARCH DESIGN AND METHODSIn order to separate the transient neurogenin 3 –expressing endocrine progenitor cells from the differentiating endocrine cells, we developed a mouse model (Ngn3-Timer) in which DsRed-E5, a fluorescent protein that shifts its emission spectrum from green to red over time, was expressed transgenically from the NEUROG3 locus.RESULTSIn the Ngn3-Timer embryos, green-dominant cells could be readily detected by microscopy or flow cytometry and distinguished from green/red double-positive cells. When fluorescent cells were sorted into three different populations by a fluorescence-activated cell sorter, placed in culture, and then reanalyzed by flow cytometry, green-dominant cells converted to green/red double-positive cells within 6 h. The sorted cell populations were then used to determine the temporal patterns of expression for 145 transcriptional regulators in the developing pancreas.CONCLUSIONSThe precise temporal resolution of this model defines the narrow window of neurogenin 3 expression in islet progenitor cells and permits sequential analyses of sorted cells as well as the testing of gene regulatory models for the differentiation of pancreatic islet cells.

MARKERS IN EXPANSION OF REGENERATING & EARLY POSTNATAL PANCREAS

Type 1 diabetes results from destruction of insulin‐producing pancreatic beta cells. A possible treatment is to replace these cells by genetic engineering or the use of stem cells. This approach requires that we understand the signals that regulate beta cell proliferation. Inhibition of DNA binding proteins (Ids), are implicated in a number of cellular processes, including control of proliferation and differentiation. Ids bind to and inhibit the function of bHLH transcription factors including those that regulate pancreatic development. Moreover, bone morphogenetic proteins (BMPs) are shown to regulate the expression of Ids. We found that neutralization of BMP4 significantly reduced duct epithelial cell expansion in a mouse model of islet regeneration. BMP4 stimulation promotes Id2 binding to the bHLH transcription factor NeuroD, which is required for the differentiation of pancreatic islet cells. Moreover, using BTC cells we demonstrated that Id2 enhanced proliferation through the Rb/E2F pathway. The early postnatal pancreas represents an intriguing model since expansion of beta cells is still evident. We found BMP4 enhanced two surface markers that may be relevant in proliferation in neonatal pancreatic cells and during islet regeneration. Collectively, our data provide novel insights into the signaling pathways required for beta cell proliferation, which may be useful for treating diabetes.

Pancreatic Development and Disease

Pancreatic Development and Disease

BMP4 Regulates Pancreatic Progenitor Cell Expansion through Id2

Inhibitor of DNA binding (Id) proteins bind to and inhibit the function of basic helix-loop-helix (bHLH) transcription factors including those that regulate pancreatic development. Moreover, bone morphogenetic proteins (BMPs) regulate the expression of Ids. We hypothesized that BMP4 and Id proteins play a role in the expansion and differentiation of epithelial progenitor cells. We demonstrate that BMP4 induces the expression of Id2 along with the expansion of AR42J pancreatic epithelial cells. Furthermore, neutralization of BMP4 significantly reduced duct epithelial cell expansion in a mouse model of islet regeneration. BMP4 stimulation promotes Id2 binding to the bHLH transcription factor NeuroD, which is required for the differentiation of pancreatic islet cells. Therefore, our results indicate that BMP4 stimulation blocks the differentiation of endocrine progenitor cells and instead promotes their expansion thereby revealing a novel paradigm of signaling explaining the balance between expansion and differentiation of pancreatic duct epithelial progenitors. Understanding the mechanisms of BMP and Id function elucidates a key step during pancreas embryogenesis, which is important knowledge for expanding pancreatic progenitors in vitro.

Cellular Aggregates Induced from Monolayer Cultures of Human Pancreatic Cells Correct Hyperglycemia in Diabetic Mice and Demonstrate Physiological Production of Human C-Peptide.

Diabetes is due to loss of appropriate insulin production by pancreatic islet cells, resulting in hyperglycemia and significant morbidity. We have developed cell cultures of pancreas-derived precursor cells that can be maintained for more than 20 population doublings in culture, growing as monolayers of undifferentiated cells. These monolayer cells can then be induced to differentiate into cellular aggregates that resemble islets when grown on different extracellular matrix components, including matrigel, or poly-d-lysine. The induced cellular aggregates, but not monolayer cells, correct hyperglycemia in diabetic (streptozotocin) SCID (severe combined immunodeficiency) mice after implantation under the kidney capsule. This animal model can be used to follow the process of differentiation from undifferentiated precursor cell to fully functional insulin producing beta cells, and to identify key proteins and genes involved in differentiation of pancreatic islet cells. Here we report that in the mice, after implantation of cellular aggregates, human c-peptide concentrations are controlled physiologically appropriately in response to glucose tolerance testing (challenged with 2 grams of glucose injected intraperitoneally) in the treated diabetic SCID mice (n = 6) as well as in normal mice that received implanted cellular aggregates (n = 6). Human c peptide is not detected in any of the control animals, nor in animals implanted with monolayer cells. Comparative RNA microarray data analyses, using U133 arrays (Affymetrix), were compared between the monolayer cells in culture and the cellular aggregates 48 hours after induction with poly-d-lysine. We consider of particular interest the up-regulation of BMP, CXCR4, and HGF in the cell aggregates, and the down-regulation of VCAM-1. We believe that these genes are necessary for either aggregation or for physiologically functional insulin secretion. When examined for greater than two-fold gene expression differences between monolayer and aggregated cells, 424 gene sequences were upregulated and 690 genes down regulated. In addition, RAGE display analysis for tyrosine kinases also showed that the kinases Erb-B2 and PDGFR-B were upregulated at 48 hours in the aggregating process. In contrast, DDR2, a collagen I receptor tyrosine kinase, was expressed equally in both monolayer and aggregated cells. In summary, the results suggest: 1) that a population of pancreatic stem cells can be isolated and cultured in vitro, 2) that these cells can be induced to form functional islet cells that correct hyperglycemia in diabetic mice, 3) that human c-peptide is physiologically regulated in aggregate implanted mice in response to glucose challenge, and 4) HGF, along with other genes of potential interest, is upregulated in the process of differentiation from monolayer to aggregated cell phenotype.

Genomic structure and promoter characterization of the gene encoding the ErbB ligand betacellulin

Betacellulin (BTC) belongs to the epidermal growth factor (EGF) family of peptide ligands that are characterized by a six-cysteine consensus motif (EGF-motif) that forms three intra-molecular disulfide bonds, crucial for binding the ErbB receptor family. A variety of in vitro studies have identified BTC as an important factor in the growth and/or differentiation of pancreatic islet cells. The molecular mechanisms that regulate the transcription of the BTC gene however have not been delineated. As an initial step, we have characterized the genomic structure of the mouse BTC (mBTC) gene. mBTC cDNA was used as a probe to screen a mouse 129/SVJ genomic bacterial artificial chromosome (BAC) library. Three positive clones containing the entire gene were isolated. DNA sequence analysis identified six exons (1–6) and five introns (A–E); a structure conserved among the EGF family. PCR analysis showed that introns A–E are approximately 7.8, 8.9, 3.8, 1.4 and 1.4 kb in length, respectively. The EGF-motif is encoded by exons 3 and 4 with an intron (intron C) disrupting the coding sequence between the second and third disulfide loops. All exon–intron boundaries are consistent with the “gt-ag” rule. Multiple transcription start sites and one poly(A) site, located 18 bp downstream of a polyadenylation signal sequence, were identified by 5′- and 3′-RACE, respectively. Approximately 2.6 kb of 5′-flanking region was sequenced and was shown to lack consensus TATA and CCAAT boxes, but was found to contain several putative cis-acting regulatory elements. These included consensus binding sites for transcription factors HNF3β, USF, Nkx2–5, AP-4, and Sp1. Functional promoter analysis of the 5′-flanking region in COS-7 cells, using 5′-deletion fragments (−168/+335; −635/+335; −732/+335; −1175/+335; −1698/+335) cloned into a promoterless firefly luciferase reporter vector, identified basal promoter activity and both positive and negative cis-acting elements.

Impaired migration and delayed differentiation of pancreatic islet cells in mice lacking EGF-receptors.

Pancreatic acini and islets are believed to differentiate from common ductal precursors through a process requiring various growth factors. Epidermal growth factor receptor (EGF-R) is expressed throughout the developing pancreas. We have analyzed here the pancreatic phenotype of EGF-R deficient (-/-) mice, which generally die from epithelial immaturity within the first postnatal week. The pancreata appeared macroscopically normal. The most striking feature of the EGF-R (-/-) islets was that instead of forming circular clusters, the islet cells were mainly located in streak-like structures directly associated with pancreatic ducts. Based on BrdU-labelling, proliferation of the neonatal EGF-R (-/-) beta-cells was significantly reduced (2.6+/-0.4 versus 5.8+/-0.9%, P<0.01) and the difference persisted even at 7-11 days of age. Analysis of embryonic pancreata revealed impaired branching morphogenesis and delayed islet cell differentiation in the EGF-R (-/-) mice. Islet development was analyzed further in organ cultures of E12.5 pancreata. The proportion of insulin-positive cells was significantly lower in the EGF-R (-/-) explants (27+/-6 versus 48+/-8%, P<0.01), indicating delayed differentiation of the beta cells. Branching of the epithelium into ducts was also impaired. Matrix metalloproteinase (MMP-2 and MMP-9) activity was reduced 20% in EGF-R (-/-) late-gestation pancreata, as measured by gelatinase assays. Furthermore, the levels of secreted plasminogen activator inhibitor-1 (PAI-1) were markedly higher, while no apparent differences were seen in the levels of active uPA and tPa between EGF-R (-/-) and wild-type pancreata. Our findings suggest that the perturbation of EGF-R-mediated signalling can lead to a generalized proliferation defect of the pancreatic epithelia associated with a delay in beta cell development and disturbed migration of the developing islet cells as they differentiate from their precursors. Upregulated PAI-1 production and decreased gelatinolytic activity correlated to this migration defect. An intact EGF-R pathway appears to be a prerequisite for normal pancreatic development.

A2B5-Reactive Ganglioside Expression Is an Index of Differentiation in Rat Insulinoma (RIN) Cells*

To investigate the relationship between surface ganglioside expression and pancreatic islet cell differentiation, we examined the function of five rat insulinoma (RIN-m5F) sublines A4, A6, A7, A10, and A12 selected for increased expression of A2B5-reactive gangliosides, as well as a subline AlGh, low in A2B5- but high in 3G5-reactive ganglioside expression. Class I major histocompatibility (MHC) protein expression was also measured in the sublines because of our previous finding that class I proteins were preferentially expressed on human insulinoma tissue compared with differentiated islet cells. In comparison with parental RIN-m5F cells, subline A12 displayed a 7.6-fold increase in A2B5 expression and a 3.4-fold increase in the number of A2B5 positive cells (81% vs. 24%). A2B5 expression was increased 1.3-, 5.4-, 5.4-, and 6.9-fold on A4, A6, A7, and A10 sublines, respectively. In contrast, AlGh cells, which had comparable A2B5 expression to parental cells, displayed a 2.9-fold increase in 3G5 expression and an 8-fold increase in the number of 3G5 positive cells (72% vs. 9%). Insulin secretion and content increased with increasing A2B5 expression. On day 2, secretion was 1.2-, 8-, 8-, 21-, and 18-fold higher and content 1.4-, 4-, 5-, 26-, and 33-fold higher for A4, A6, A7, A10, and A12 cells, respectively, compared to parental cells. There was a direct association between expression of A2B5 and the level of insulin messenger RNA (mRNA) in the sublines. Neither glucagon nor somatostatin was detected in any subline. The AlGh subline secreted and contained less insulin than parental cells. Fully differentiated adult rat islet cells, the majority of which are beta-cells, contained a lower number of 3G5 (12%) than A2B5 (57%) positive cells. Compared to parental cells, class I MHC proteins were decreased 4-fold on A12 cells, but increased 1.5-fold on AlGh cells. We conclude that, at least in RIN cells, the expression of A2B5-reactive ganglioside expression is associated directly, and class I MHC protein expression indirectly, with beta-cell differentiation.