Human pancreas development

Zebrafish Pancreas Development and Regeneration: Fishing for Diabetes Therapies

The zebrafish pancreas shares its basic organization and cell types with the mammalian pancreas. In addition, the developmental pathways that lead to the establishment of the pancreatic islets of Langherhans are generally conserved from fish to mammals. Zebrafish provides a powerful tool to probe the mechanisms controlling establishment of the pancreatic endocrine cell types from early embryonic progenitor cells, as well as the regeneration of endocrine cells after damage. This knowledge is, in turn, applicable to refining protocols to generate renewable sources of human pancreatic islet cells that are critical for regulation of blood sugar levels. Here, we review how previous and ongoing studies in zebrafish and beyond are influencing the understanding of molecular mechanisms underlying various forms of diabetes and efforts to develop cell-based approaches to cure this increasingly widespread disease.

Directed differentiation of human iPSC into insulin producing cells is improved by induced expression of PDX1 and NKX6.1 factors in IPC progenitors

Background

Induced pluripotent stem cells (iPSC) possess an enormous potential as both, scientific and therapeutic tools. Their application in the regenerative medicine provides new treatment opportunities for numerous diseases, including type 1 diabetes. In this work we aimed to derive insulin producing cells (IPC) from iPS cells established in defined conditions.

Methods

We optimized iPSC generation protocol and created pluripotent cell lines with stably integrated PDX1 and NKX6.1 transgenes under the transcriptional control of doxycycline-inducible promoter. These cells were differentiated using small chemical molecules and recombinant Activin A in the sequential process through the definitive endoderm, pancreatic progenitor cells and insulin producing cells. Efficiency of the procedure was assessed by quantitative gene expression measurements, immunocytochemical stainings and functional assays for insulin secretion.

Results

Generated cells displayed molecular markers characteristic for respective steps of the differentiation. The obtained IPC secreted insulin and produced C-peptide with significantly higher hormone release level in case of the combined expression of PDX1 and NKX6.1 induced at the last stage of the differentiation.

Conclusions

Efficiency of differentiation of iPSC to IPC can be increased by concurrent expression of PDX1 and NKX6.1 during progenitor cells maturation. Protocols established in our study allow for iPSC generation and derivation of IPC in chemically defined conditions free from animal-derived components, which is of the utmost importance in the light of their prospective applications in the field of regenerative medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1097-0) contains supplementary material, which is available to authorized users.

Loss of Pancreas upon Activated Wnt Signaling Is Concomitant with Emergence of Gastrointestinal Identity

Organ formation is achieved through the complex interplay between signaling pathways and transcriptional cascades. The canonical Wnt signaling pathway plays multiple roles during embryonic development including patterning, proliferation and differentiation in distinct tissues. Previous studies have established the importance of this pathway at multiple stages of pancreas formation as well as in postnatal organ function and homeostasis. In mice, gain-of-function experiments have demonstrated that activation of the canonical Wnt pathway results in pancreatic hypoplasia, a phenomenon whose underlying mechanisms remains to be elucidated. Here, we show that ectopic activation of epithelial canonical Wnt signaling causes aberrant induction of gastric and intestinal markers both in the pancreatic epithelium and mesenchyme, leading to the development of gut-like features. Furthermore, we provide evidence that β -catenin-induced impairment of pancreas formation depends on Hedgehog signaling. Together, our data emphasize the developmental plasticity of pancreatic progenitors and further underscore the key role of precise regulation of signaling pathways to maintain appropriate organ boundaries.

Revisiting the immunocytochemical detection of Neurogenin 3 expression in mouse and man

During embryonic development, endocrine cells of the pancreas are specified from multipotent progenitors. The transcription factor Neurogenin 3 (NEUROG3) is critical for this development and it has been shown that all endocrine cells of the pancreas arise from endocrine progenitors expressing NEUROG3. A thorough understanding of the role of NEUROG3 during development, directed differentiation of pluripotent stem cells and in models of cellular reprogramming, will guide future efforts directed at finding novel sources of β-cells for cell replacement therapies. In this article, we review the expression and function of NEUROG3 in both mouse and human and present the further characterization of a monoclonal antibody directed against NEUROG3. This antibody has been previously been used for detection of both mouse and human NEUROG3. However, our results suggest that the epitope recognized by this antibody is specific to mouse NEUROG3. Thus, we have also generated a monoclonal antibody specifically recognizing human NEUROG3 and present the characterization of this antibody here. Together, these antibodies will provide useful tools for future studies of NEUROG3 expression, and the data presented in this article suggest that recently described expression patterns of NEUROG3 in human foetal and adult pancreas should be re-examined.

An integrative transcriptomic atlas of organogenesis in human embryos

Human organogenesis is when severe developmental abnormalities commonly originate. However, understanding this critical embryonic phase has relied upon inference from patient phenotypes and assumptions from in vitro stem cell models and non-human vertebrates. We report an integrated transcriptomic atlas of human organogenesis. By lineage-guided principal components analysis, we uncover novel relatedness of particular developmental genes across different organs and tissues and identified unique transcriptional codes which correctly predicted the cause of many congenital disorders. By inference, our model pinpoints co-enriched genes as new causes of developmental disorders such as cleft palate and congenital heart disease. The data revealed more than 6000 novel transcripts, over 90% of which fulfil criteria as long non-coding RNAs correlated with the protein-coding genome over megabase distances. Taken together, we have uncovered cryptic transcriptional programs used by the human embryo and established a new resource for the molecular understanding of human organogenesis and its associated disorders.

DOI:http://dx.doi.org/10.7554/eLife.15657.001

Individual organs and tissues form in human embryos during the first two months of pregnancy. Any errors during this crucial stage of human development can result in miscarriage or serious birth defects. Yet remarkably little is known about how this process works. What is known has been inferred from studies of how other animals develop, human stem cells grown in a laboratory, and babies born with genetic conditions that cause developmental problems.

Genes control the way that organs and tissues form, and are switched on or off in complex patterns during development to ensure that particular cells develop into one type of organ and not another. When genes are switched on, their DNA is copied into molecules called RNA. Many RNA molecules are used as templates to make proteins, which then perform critical roles in cell processes. One way to find out which genes are activated during development is to identify which RNAs are made by cells in the embryo.

Here, Gerrard, Berry et al. used a technique called RNA-sequencing to identify the RNAs that human embryos make while their organs and tissues form. The RNA came from many different tissues including the heart, limbs and the roof of the mouth. Gerrard, Berry et al. developed a new computational model that used the identity of the RNAs to decode the precise patterns of gene activity in the tissues. The model correctly identified many genes that were already known to cause developmental problems when faulty, and identified numerous others that are now predicted to cause developmental defects in humans.

Gerrard, Berry et al. also discovered over 6,000 RNAs in the human embryos that are unlikely to code for proteins. These “non-coding” RNAs may have other roles in cells, such as switching off genes, and many of them appear to be specific to human embryos. Together, these findings have uncovered new patterns of gene activity that drive development in human embryos and provide a resource for studying how organs and tissues form. Future challenges are to understand what controls these patterns of gene activity, and how the patterns change over time.

DOI:http://dx.doi.org/10.7554/eLife.15657.002

Molecular mechanisms of Sox transcription factors during the development of liver, bile duct, and pancreas

The liver and pancreas are the prime digestive and metabolic organs in the body. After emerging from the neighboring domains of the foregut endoderm, they turn on distinct differentiation and morphogenesis programs that are regulated by hierarchies of transcription factors. Members of SOX family of transcription factors are expressed in the liver and pancreas throughout development and act upstream of other organ-specific transcription factors. They play key roles in maintaining stem cells and progenitors. They are also master regulators of cell fate determination and tissue morphogenesis. In this review, we summarize the current understanding of SOX transcription factors in mediating liver and pancreas development. We discuss their contribution to adult organ function, homeostasis and injury responses. We also speculate how the knowledge of SOX transcription factors can be applied to improve therapies for liver diseases and diabetes.

Mesenchymal Stem Cells Derived from Human Exocrine Pancreas Spontaneously Express Pancreas Progenitor-Cell Markers in a Cell-Passage-Dependent Manner

Mesenchymal stem cells (MSCs) derived from bone marrow, adipose tissue, and most connective tissues have been recognized as promising sources for cell-based therapies. MSCs have also been detected in human pancreatic tissue, including endocrine and exocrine cells. These adult human pancreas-derived MSCs have generated a great deal of interest owing to their potential use in the differentiation of insulin-producing cells for diabetes treatment. In the present study, we isolated MSCs from the adult human exocrine pancreas to determine whether isolated MSCs have the potential to differentiate into pancreatic endocrine cells and, therefore, whether they can be used in stem cell-based therapies. Pancreatic tissue was digested by collagenase and an enriched exocrine-cell fraction was obtained by density-gradient separation. Crude exocrine cells were methodically cultured in suspension and then in adherent culture. We expanded the human pancreatic exocrine-derived MSCs (hpMSCs) by cell passaging in culture and confirmed by flow cytometry that >90% expressed human classic surface markers of MSCs. Interestingly, these cells expressed pancreatic transcription factors, such as Pdx1, Ngn3, and MafA, similar to pancreatic progenitor cells. These results indicated that hpMSCs can be used for the differentiation of pancreatic endocrine cells and may be used in type 1 diabetes treatment.

Pancreas Volume and Fat Deposition in Diabetes and Normal Physiology: Consideration of the Interplay Between Endocrine and Exocrine Pancreas

The pancreas is comprised of exocrine and endocrine components. Despite the fact that they are derived from a common origin in utero, these two compartments are often studied individually because of the different roles and functions of the exocrine and endocrine pancreas. Recent studies have shown that not only type 1 diabetes (T1D), but also type 2 diabetes (T2D), is characterized by a deficit in beta-cell mass, suggesting that pathological changes in the pancreas are critical events in the natural history of diabetes. In both patients with T1D and those with T2D, pancreas mass and exocrine function have been reported to be reduced. On the other hand, pancreas volume and pancreatic fat increase with obesity. Increased beta-cell mass with increasing obesity has also been observed in humans, and ectopic fat deposits in the pancreas have been reported to cause beta-cell dysfunction. Moreover, neogenesis and transdifferentiation from the exocrine to the endocrine compartment in the postnatal period are regarded as a source of newly formed beta-cells. These findings suggest that there is important interplay between the endocrine and exocrine pancreas throughout life. This review summarizes the current knowledge on physiological and pathological changes in the exocrine and endocrine pancreas (i.e., beta-cell mass), and discusses the potential mechanisms of the interplay between the two compartments in humans to understand the pathophysiology of diabetes better.

Changes in expression of C2cd4c in pancreatic endocrine cells during pancreatic development

C2cd4c, encoded by a gene belonging to the C2cd4 family, contains a C2 domain conserved across species and is localized to the cytoplasm. To examine the role of C2cd4c in the pancreas, we studied its localization and generated C2cd4c knockout (KO) mice. C2cd4c was expressed in pancreatic endocrine progenitors at early embryonic stages. When endocrine cells arise from their precursors, C2cd4c is gradually confined to the insulin‐ and pancreatic polypeptide‐expressing cells of the endocrine. In the adult pancreas, C2cd4c is restricted to the beta cells. C2cd4c KO mice showed normal embryonic pancreatic development and adult pancreatic function. Thus, our results suggest that C2cd4c is dispensable for pancreatic development.

De Novo Prediction of Stem Cell Identity using Single-Cell Transcriptome Data

Adult mitotic tissues like the intestine, skin, and blood undergo constant turnover throughout the life of an organism. Knowing the identity of the stem cell is crucial to understanding tissue homeostasis and its aberrations upon disease. Here we present a computational method for the derivation of a lineage tree from single-cell transcriptome data. By exploiting the tree topology and the transcriptome composition, we establish StemID, an algorithm for identifying stem cells among all detectable cell types within a population. We demonstrate that StemID recovers two known adult stem cell populations, Lgr5+ cells in the small intestine and hematopoietic stem cells in the bone marrow. We apply StemID to predict candidate multipotent cell populations in the human pancreas, a tissue with largely uncharacterized turnover dynamics. We hope that StemID will accelerate the search for novel stem cells by providing concrete markers for biological follow-up and validation.

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StemID infers the lineage tree and identifies stem cells from single-cell mRNA-seq data

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Direct links of stem cells to distinct sub-types reflect transcriptome plasticity

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The permissive stem cell transcriptome is characterized by high entropy

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StemID infers candidate multipotent cell populations in the human pancreas

Xenopus as a model system for studying pancreatic development and diabetes

Diabetes is a chronic disease caused by the loss or dysfunction of the insulin-producing β-cells in the pancreas. To date, much of our knowledge about β-cells in humans comes from studying rare monogenic forms of diabetes. Importantly, the majority of mutations so far associated to monogenic diabetes are in genes that exert a regulatory role in pancreatic development and/or β-cell function. Thus, the identification and study of novel mutations open an unprecedented window into human pancreatic development. In this review, we summarize major advances in the genetic dissection of different types of monogenic diabetes and the insights gained from a developmental perspective. We highlight future challenges to bridge the gap between the fast accumulation of genetic data through next-generation sequencing and the need of functional insights into disease mechanisms. Lastly, we discuss the relevance and advantages of studying candidate gene variants in vivo using the Xenopus as model system.

Human development: a Special Issue

Summary: With this Special Issue, Development signals its strong interest in the field of human development – a new research frontier opened up by recent technological advances.

Human pluripotent stem cell based islet models for diabetes research

Although similar, mouse and human pancreatic development and beta cell physiology have significant differences. For this reason, mouse models present shortcomings that can obscure the understanding of human diabetes pathology. Progress in the field of human pluripotent stem cell (hPSC) differentiation now makes it possible to derive unlimited numbers of human beta cells in vitro. This constitutes an invaluable approach to gain insight into human beta cell development and physiology and to generate improved disease models. Here we summarize the main differences in terms of development and physiology of the pancreatic endocrine cells between mouse and human, and describe the recent progress in modeling diabetes using hPSC. We highlight the need of developing more physiological hPSC-derived beta cell models and anticipate the future prospects of these approaches.