Regulation of pancreas development by hedgehog signaling

Pancreaticobiliary Maljunction: A Multidimensional Exploration of Pathophysiology, Diagnosis, Classification, Management and Research Prospects

Pancreaticobiliary maljunction is a congenital malformation in which the pancreatic and bile ducts join anatomically outside the duodenal wall, usually forming a markedly long common channel, which can cause reciprocal reflux between pancreatic juice and bile. Cholangiography, endoscopic ultrasonography, surgery, and autopsy can be used to diagnose pancreaticobiliary maljunction. Elevated amylase levels in bile and extrahepatic bile duct dilatation strongly suggest the existence of pancreaticobiliary maljunction. The regurgitation may lead to the development of various hepatobiliary and pancreatic disorders such as pancreatitis and biliary carcinoma. The pathogenesis of pancreaticobiliary maljunction is the result of a series of pathophysiological changes caused by reflux. Surgery is recommended for patients diagnosed with pancreaticobiliary maljunction irrespective of the presence or absence of symptoms because of its high biliary carcinogenicity, but the treatment strategy is quite different between adult patients with and without biliary dilatation.

SHH Signaling as a Key Player in Endometrial Cancer: Unveiling the Correlation with Good Prognosis, Low Proliferation, and Anti-Tumor Immune Milieu

Endometrial Cancer (EC) is one of the most common gynecological malignancies. Despite its prevalence, molecular pathways, such as the Sonic Hedgehog (SHH) pathway, have not been extensively studied in the context of EC. This study aims to explore the clinical implications of SHH expression in EC, potentially uncovering new insights into the disease's pathogenesis and offering valuable insights for therapeutic strategies in EC. We utilized data from The Cancer Genome Atlas (TCGA) to divide the dataset into 'High SHH' and 'Low SHH' groups based on a gene signature score derived from SHH pathway-related genes. We explored the clinical and tumor characteristics of these groups, focusing on key cancer hallmarks, including stemness, proliferation, cytolytic activity, tumor micro-environment, and genomic instability. 'High SHH' tumors emerged as a distinct category with favorable clinical and molecular features. These tumors exhibited lower proliferation rates, reduced angiogenesis, and diminished genomic instability, indicating a controlled and less aggressive tumor growth pattern. Moreover, 'High SHH' tumors displayed lower stemness, highlighting a less invasive phenotype. The immune micro-environment in 'High SHH' tumors was enriched with immune cell types, such as macrophage M0, monocytes, B cells, CD8 T cells, CD4 T cells, follicular helper T cells, and natural killer cells. This immune enrichment, coupled with higher cytolytic activity, suggested an improved anti-tumor immune response. Our study sheds light on the clinical significance of Sonic signaling in EC. 'High SHH' tumors exhibit a unique molecular and clinical profile associated with favorable cancer hallmarks, lower grades, and better survival. These findings underscore the potential utility of SHH expression as a robust prognostic biomarker, offering valuable insights for tailored therapeutic strategies in EC. Understanding the SHH pathway's role in EC contributes to our growing knowledge of this cancer and may pave the way for more effective treatment strategies in the future.

Interactions between hedgehog signaling pathway and the complex tumor microenvironment in breast cancer: current knowledge and therapeutic promises

Breast cancer ranks as one of the most common malignancies among women, with its prognosis and therapeutic efficacy heavily influenced by factors associated with the tumor cell biology, particularly the tumor microenvironment (TME). The diverse elements of the TME are engaged in dynamic bidirectional signaling interactions with various pathways, which together dictate the growth, invasiveness, and metastatic potential of breast cancer. The Hedgehog (Hh) signaling pathway, first identified in Drosophila, has been established as playing a critical role in human development and disease. Notably, the dysregulation of the Hh pathway is recognized as a major driver in the initiation, progression, and metastasis of breast cancer. Consequently, elucidating the mechanisms by which the Hh pathway interacts with the distinct components of the breast cancer TME is essential for comprehensively evaluating the link between Hh pathway activation and breast cancer risk. This understanding is also imperative for devising novel targeted therapeutic strategies and preventive measures against breast cancer. In this review, we delineate the current understanding of the impact of Hh pathway perturbations on the breast cancer TME, including the intricate and complex network of intersecting signaling cascades. Additionally, we focus on the therapeutic promise and clinical challenges of Hh pathway inhibitors that target the TME, providing insights into their potential clinical utility and the obstacles that must be overcome to harness their full therapeutic potential.

Unraveling the interplay: exploring signaling pathways in pancreatic cancer in the context of pancreatic embryogenesis

Pancreatic cancer continues to be a deadly disease because of its delayed diagnosis and aggressive tumor biology. Oncogenes and risk factors are being reported to influence the signaling pathways involved in pancreatic embryogenesis leading to pancreatic cancer genesis. Although studies using rodent models have yielded insightful information, the scarcity of human pancreatic tissue has made it difficult to comprehend how the human pancreas develops. Transcription factors like IPF1/PDX1, HLXB9, PBX1, MEIS, Islet-1, and signaling pathways, including Hedgehog, TGF-β, and Notch, are directing pancreatic organogenesis. Any derangements in the above pathways may lead to pancreatic cancer. TP53: and CDKN2A are tumor suppressor genes, and the mutations in TP53 and somatic loss of CDKN2A are the drivers of pancreatic cancer. This review clarifies the complex signaling mechanism involved in pancreatic cancer, the same signaling pathways in pancreas development, the current therapeutic approach targeting signaling molecules, and the mechanism of action of risk factors in promoting pancreatic cancer.

Degradation meets development: Implications in β-cell development and diabetes

Pancreatic development is orchestrated by timely synthesis and degradation of stage-specific transcription factors (TFs). The transition from one stage to another stage is dependent on the precise expression of the developmentally relevant TFs. Persistent expression of particular TF would impede the exit from the progenitor stage to the matured cell type. Intracellular protein degradation-mediated protein turnover contributes to a major extent to the turnover of these TFs and thereby dictates the development of different tissues. Since even subtle changes in the crucial cellular pathways would dramatically impact pancreatic β-cell performance, it is generally acknowledged that the biological activity of these pathways is tightly regulated by protein synthesis and degradation process. Intracellular protein degradation is executed majorly by the ubiquitin proteasome system (UPS) and Lysosomal degradation pathway. As more than 90% of the TFs are targeted to proteasomal degradation, this review aims to examine the crucial role of UPS in normal pancreatic β-cell development and how dysfunction of these pathways manifests in metabolic syndromes such as diabetes. Such understanding would facilitate designing a faithful approach to obtain a therapeutic quality of β-cells from stem cells.

Whole-genome selection signature differences between Chaohu and Ji'an red ducks

Assessing the genetic structure of local varieties and understanding their genetic data are crucial for effective management and preservation. However, the genetic differences among local breeds require further explanation. To enhance our understanding of their population structure and genetic diversity, we conducted a genome-wide comparative study of Chaohu and Ji'an Red ducks using genome sequence and restriction site-associated DNA sequencing technology. Our analysis revealed a distinct genetic distinction between the two breeds, leading to divided groups. The phylogenetic tree for Chaohu duck displayed two branches, potentially indicating minimal impact from artificial selection. Additionally, our ROH (runs of homozygosity) analysis revealed that Chaohu ducks had a lower average inbreeding coefficient than Ji'an Red ducks. We identified several genomic regions with high genetic similarity in these indigenous duck breeds. By conducting a selective sweep analysis, we identified 574 candidate genes associated with muscle growth (BMP2, ITGA8, MYLK, and PTCH1), fat deposits (ELOVL1 and HACD2), and pigmentation (ASIP and LOC101797494). These results offer valuable insights for the further enhancement and conservation of Chinese indigenous duck breeds.

Fetal Hypoglycemia Induced by Placental SLC2A3-RNA Interference Alters Fetal Pancreas Development and Transcriptome at Mid-Gestation

Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to β cell activity.

Manipulation of Sonic Hedgehog Signaling Pathway in Maintenance, Differentiation, and Endocrine Activity of Insulin-Producing Cells: A Systematic Review

Background

Some studies have evaluated the manipulation of the sonic hedgehog (Shh) signaling pathway to generate more efficient insulin-producing cells (IPCs). In a systematic review, we evaluated in vitro and in vivo studies on the effect of inhibition or activation of the Shh pathway on the production, differentiation, maintenance, and endocrine activity of IPCs.

Methods

A systematic review was conducted using all available experimental studies published between January 2000 and November 2022. The review aimed at determining the effect of Shh manipulation on the differentiation of stem cells (SCs) into IPCs. Keywords and phrases using medical subject headings were extracted, and a complete search was performed in Web of Science, Embase, ProQuest, PubMed, Scopus, and Cochrane Library databases. The inclusion criteria were manipulation of Shh in SCs, SCs differentiation into IPCs, and endocrine activity of mature IPCs. Articles with incomplete data and duplications were excluded.

Results

A total of 208 articles were initially identified, out of which 11 articles were included in the study. The effect of Shh inhibition in the definitive endoderm stage to produce functional IPCs were confirmed. Some studies showed the importance of Shh re-activation at late-stage differentiation for the generation of efficient IPCs. It is proposed that baseline concentrations of Shh in mature pancreatic β-cells affect insulin secretion and endocrine activities of the cells. However, Shh overexpression in pancreatic β-cells ultimately leads to improper endocrine function and inadequate glucose-sensing insulin secretion.

Conclusion

Accurate manipulation of the Shh signaling pathway can be an effective approach in the production and maintenance of functional IPCs.

LncRNA Malat1 regulates iPSC-derived β-cell differentiation by targeting the miR-15b-5p/Ihh axis

BACKGROUND

Differentiation of induced pluripotent stem cells (iPSCs)-derived β-like cells is a novel strategy for treatment of type 1 diabetes. Elucidation of the regulatory mechanisms of long noncoding RNAs (lncRNAs) in β-like cells derived from iPSCs is important for understanding the development of the pancreas and pancreatic β-cells and may improve the quality of β-like cells for stem cell therapy.

METHODS

β-like cells were derived from iPSCs in a three-step protocol. RNA sequencing and bioinformatics analysis were carried out to screen the differentially expressed lncRNAs and identify the putative target genes separately. LncRNA Malat1 was chosen for further research. Series of loss and gain of functions experiments were performed to study the biological function of LncRNA Malat1. Quantitative real-time PCR (qRT-PCR), Western blot (WB) analysis and immunofluorescence (IF) staining were carried out to separately detect the functions of pancreatic β-cells at the mRNA and protein levels. Cytoplasmic and nuclear RNA fractionation and fluorescence in situ hybridization (FISH) were used to determine the subcellar location of lncRNA Malat1 in β-like cells. Enzyme-linked immunosorbent assays (ELISAs) were performed to examine the differentiation and insulin secretion of β-like cells after stimulation with different glucose concentrations. Structural interactions between lncRNA Malat1 and miR-15b-5p and between miR-15b-5p/Ihh were detected by dual luciferase reporter assays (LRAs).

RESULTS

We found that the expression of lncRNA Malat1 declined during differentiation, and overexpression (OE) of lncRNA Malat1 notably impaired the differentiation and maturation of β-like cells derived from iPSCs in vitro and in vivo. Most importantly, lncRNA Malat1 could function as a competing endogenous RNA (ceRNA) of miR-15b-5p to regulate the expression of Ihh according to bioinformatics prediction, mechanistic analysis and downstream experiments.

CONCLUSION

This study established an unreported regulatory network of lncRNA Malat1 and the miR-15b-5p/Ihh axis during the differentiation of iPSCs into β-like cells. In addition to acting as an oncogene promoting tumorigenesis, lncRNA Malat1 may be an effective and novel target for treatment of diabetes in the future.

Development of the Pancreatic Ducts and Their Contribution to Organogenesis

The pancreas is a dual-function organ, with exocrine cells that aid in digestion and endocrine cells that regulate glucose homeostasis. These cell types share common progenitors and arise from the embryonic ducts. Early signaling events in the embryonic ducts shape the neonatal, adolescent, and adult exocrine and endocrine pancreas. This chapter discusses recent advances in the tools used to study the ducts and our current understanding of how ductal development contributes to pancreatic organogenesis.

The role of noncoding RNAs in pancreatic birth defects

Congenital defects in the pancreas can cause severe health issues such as pancreatic cancer and diabetes which require lifelong treatment. Regenerating healthy pancreatic cells to replace malfunctioning cells has been considered a promising cure for pancreatic diseases including birth defects. However, such therapies are currently unavailable in the clinic. The developmental gene regulatory network underlying pancreatic development must be reactivated for in vivo regeneration and recapitulated in vitro for cell replacement therapy. Thus, understanding the mechanisms driving pancreatic development will pave the way for regenerative therapies. Pancreatic progenitor cells are the precursors of all pancreatic cells which use epigenetic changes to control gene expression during differentiation to generate all of the distinct pancreatic cell types. Epigenetic changes involving DNA methylation and histone modifications can be controlled by noncoding RNAs (ncRNAs). Indeed, increasing evidence suggests that ncRNAs are indispensable for proper organogenesis. Here, we summarize recent insight into the role of ncRNAs in the epigenetic regulation of pancreatic development. We further discuss how disruptions in ncRNA biogenesis and expression lead to developmental defects and diseases. This review summarizes in vivo data from animal models and in vitro studies using stem cell differentiation as a model for pancreatic development.

Protocol-Dependent Morphological Changes in Human Embryonic Stem Cell Aggregates during Differentiation toward Early Pancreatic Fate

Cell therapy is one of the promising approaches used against type 1 diabetes. Efficient generation of human embryonic stem cell (hESC)-derived pancreatic progenitors (PPs) is of great importance. Since signaling pathways underlying human pancreas development are not yet fully understood, various differentiation protocols are conducted, each considering variable duration, timing, and concentrations of growth factors and small molecules. Therefore, we compared two PP differentiation protocols in static suspension culture. We tested modified protocols developed by Pagliuca et al. (protocol 1) and Royan researchers (protocol 2) until early PP stage. The morphological changes of hESC aggregates during differentiation, and also gene and protein expression after differentiation, were evaluated. Different morphological structures were formed in each protocol. Quantitative gene expression analysis, flow cytometry, and immunostaining revealed a high level of PDX1 expression on day 13 of Royan's differentiation protocol compared to protocol 1. Our data showed that using protocol 2, cells were further differentiated until day 16, showing higher efficiency of early PPs. Moreover, protocol 2 is able to produce hESCs-PPs in a static suspension culture. Since protocol 2 is inexpensive in terms of media, growth factors, and chemicals, it can be used for massive production of PPs using static and dynamic suspension cultures.

Ptf1a function and transcriptional cis-regulation, a cornerstone in vertebrate pancreas development

Vertebrate pancreas organogenesis is a stepwise process regulated by a complex network of signaling and transcriptional events, progressively steering the early endoderm toward pancreatic fate. Many crucial players of this process have been identified, including signaling pathways, cis-regulatory elements, and transcription factors (TFs). Pancreas-associated transcription factor 1a (PTF1A) is one such TF, crucial for pancreas development. PTF1A mutations result in dramatic pancreatic phenotypes associated with severe complications, such as neonatal diabetes and impaired food digestion due to exocrine pancreatic insufficiency. Here, we present a brief overview of vertebrate pancreas development, centered on Ptf1a function and transcriptional regulation, covering similarities and divergences in three broadly studied organisms: human, mouse and zebrafish.

Prenatal Detection of Congenital Duodenal Obstruction-Impact on Postnatal Care

BACKGROUND

Duodenal obstruction is a rare cause of congenital bowel obstruction. Prenatal ultrasound could be suggestive of duodenal atresia if polyhydramnios and the double bubble sign are visible. Prenatal diagnosis should prompt respective prenatal care, including surgery. The aim of this study was to investigate the rate and importance of prenatally diagnosed duodenal obstruction, comparing incomplete and complete duodenal obstruction.

METHODS

A retrospective, single-center study was performed using data from patients operated on for duodenal obstruction between 2004 and 2019. Prenatal ultrasound findings were obtained from maternal logbooks and directly from the investigating obstetricians. Postnatal data were obtained from electronic charts, including imaging, operative notes and follow-up.

RESULTS

A total of 33/64 parents of respective patients agreed to provide information on prenatal diagnostics. In total, 11/15 patients with complete duodenal obstruction and 0/18 patients with incomplete duodenal obstruction showed typical prenatal features. Prenatal diagnosis prompted immediate surgical treatment after birth.

CONCLUSION

Prenatal diagnosis of congenital duodenal obstruction is only achievable in cases of complete congenital duodenal obstruction by sonographic detection of the pathognomonic double bubble sign. Patients with incomplete duodenal obstruction showed no sign of duodenal obstruction on prenatal scans and thus were diagnosed and treated later.

Pancreatic Cancer Microenvironment and Cellular Composition: Current Understandings and Therapeutic Approaches

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal human solid tumors, despite great efforts in improving therapeutics over the past few decades. In PDAC, the distinct characteristic of the tumor microenvironment (TME) is the main barrier for developing effective treatments. PDAC TME is characterized by a dense stroma, cancer-associated fibroblasts, and immune cells populations that crosstalk to the subpopulations of neoplastic cells that include cancer stem cells (CSCs). The heterogeneity in TME is also exhibited in the diversity and dynamics of acellular components, including the Extracellular matrix (ECM), cytokines, growth factors, and secreted ligands to signaling pathways. These contribute to drug resistance, metastasis, and relapse in PDAC. However, clinical trials targeting TME components have often reported unexpected results and still have not benefited patients. The failures in those trials and various efforts to understand the PDAC biology demonstrate the highly heterogeneous and multi-faceted TME compositions and the complexity of their interplay within TME. Hence, further functional and mechanistic insight is needed. In this review, we will present a current understanding of PDAC biology with a focus on the heterogeneity in TME and crosstalk among its components. We also discuss clinical challenges and the arising therapeutic opportunities in PDAC research.

The development of zebrafish pancreas affected by deficiency of Hedgehog signaling

The pancreas development depends on complex regulation of several signaling pathways, including the Hedgehog (Hh) signaling via a receptor complex component, Smoothened, which deficiency blocks the Hh signaling. Such a defect in birds and mammals results in an annular pancreas. We showed that in developing zebrafish, the mutation of Smoothened or inhibition of Hh signaling by its antagonist cyclopamine caused developmental defects of internal organs, liver, pancreas, and gut. In particular, the pancreatic primordium was duplicated. The two exocrine pancreatic primordia surround the gut. This phenomenon correlates with a significant reduction of the gut's diameter, causing the annular pancreas phenotype.

Sonic hedgehog signals hinder the transcriptional network necessary for pancreatic endoderm formation from human embryonic stem cells

Hedgehog morphogens govern multiple aspects of pancreas organogenesis and functioning with diverse outcomes across species. Although most current differentiation protocols repress Sonic hedgehog (SHH) signals during in vitro endocrine specification, the role and mechanisms through which the SHH pathway antagonizes pancreas development during in vitro human embryonic stem (hES) cell differentiation remain unclear. We modulated SHH signaling at transitory stages of hES cell-derived pancreatic progenitors and analyzed the effect on cellular fate decisions. We identify the Hedgehog pathway as a negative regulator of pancreatic endoderm formation through up-regulation of a set of pancreatobiliary markers required for ductal specification, including SOX17, FOXA2, HNF1β, HNF6, PDX1, and SOX9. Surprisingly, active Hedgehog signals impeded a group of pancreatic epithelium markers, including HNF4α, HHEX, PAX6, and PTF1α. To understand how SHH signals repress the transcription of these specific markers, we analyzed Polycomb group proteins. We found differential expression of Polycomb Repressive Complex 1 subunit, BMI1 upon Shh pathway modulation in the pancreatic progenitors. Ectopic activation of Sonic hedgehog results in over-expression of BMI1 and its associated repressive histone mark, H2AK119Ub1, in the multipotent progenitors. Our data suggest that Sonic hedgehog restricts the pancreatic differentiation program by limiting progenitor cells acquiring pancreatic epithelial fates and instead promotes pancreatobiliary differentiation. We further provide mechanistic cues of an association between Hedgehog signaling and epigenetic silencers during pancreatic lineage decisions.

Pancreatic Cancer and Therapy: Role and Regulation of Cancer Stem Cells

Despite significant improvements in clinical management, pancreatic cancer (PC) remains one of the deadliest cancer types, as it is prone to late detection with extreme metastatic properties. The recent findings that pancreatic cancer stem cells (PaCSCs) contribute to the tumorigenesis, progression, and chemoresistance have offered significant insight into the cancer malignancy and development of precise therapies. However, the heterogeneity of cancer and signaling pathways that regulate PC have posed limitations in the effective targeting of the PaCSCs. In this regard, the role for K-RAS, TP53, Transforming Growth Factor-β, hedgehog, Wnt and Notch and other signaling pathways in PC progression is well documented. In this review, we discuss the role of PaCSCs, the underlying molecular and signaling pathways that help promote pancreatic cancer development and metastasis with a specific focus on the regulation of PaCSCs. We also discuss the therapeutic approaches that target different PaCSCs, intricate mechanisms, and therapeutic opportunities to eliminate heterogeneous PaCSCs populations in pancreatic cancer.

Hedgehog Signaling in Intestinal Development and Homeostasis

The hedgehog (Hh) signaling pathway plays several diverse regulatory and patterning roles during organogenesis of the intestine and in the regulation of adult intestinal homeostasis. In the embryo, fetus, and adult, intestinal Hh signaling is paracrine: Hh ligands are expressed in the endodermally derived epithelium, while signal transduction is confined to the mesenchymal compartment, where at least a dozen distinct cell types are capable of responding to Hh signals. Epithelial Hh ligands not only regulate a variety of mesenchymal cell behaviors, but they also direct these mesenchymal cells to secrete additional soluble factors (e.g., Wnts, Bmps, inflammatory mediators) that feed back to regulate the epithelial cells themselves. Evolutionary conservation of the core Hh signaling pathway, as well as conservation of epithelial/mesenchymal cross talk in the intestine, has meant that work in many diverse model systems has contributed to our current understanding of the role of this pathway in intestinal organogenesis, which is reviewed here.

Effect of Sonic hedgehog pathway inhibition on PDX1 expression during pancreatic differentiation of human embryonic stem cells

Differentiation processes for generating pancreatic progenitors from pluripotent stem cells inhibit Sonic hedgehog signaling through synthetic antagonists. However, the effect of sonic hedgehog inhibition in differentiating human embryonic stem cells remains unclear. The primary aim of this study was to understand the effect of Sonic hedgehog inhibition on key pancreas-specific transcription factors during differentiation of human embryonic stem cells towards a pancreatic lineage. We differentiated human embryonic stem (ES) cells towards the pancreatic progenitor stage. To analyze the effect of Sonic hedgehog inhibition, we differentiated human ES cells in the presence or absence of pathway antagonist, cyclopamine, using the same concentration (0.25 µM) as reported earlier. Changes in gene expression between the groups were examined by quantitative reverse-transcription PCR and immunoblot analyses. Surprisingly, we found that expression of key transcription factors, PDX1 and SOX9, was not majorly affected by inhibition of Sonic hedgehog signals. Effects of inhibiting Hedgehog signals on pancreas-specific markers in differentiating human embryonic stem cells were analyzed in the study. We identified that the expression of pancreas-specific PDX1 and SOX9 was not affected by the Sonic hedgehog pathway in pancreatic progenitor populations from human ES cells. Thus, the restrictive nature of Hedgehog signaling during the early stages of pancreas formation could be facilitated through a transcriptional network beyond PDX1 and SOX9.

Human stem cell models: lessons for pancreatic development and disease

A comprehensive understanding of mechanisms that underlie the development and function of human cells requires human cell models. For the pancreatic lineage, protocols have been developed to differentiate human pluripotent stem cells (hPSCs) into pancreatic endocrine and exocrine cells through intermediates resembling in vivo development. In recent years, this differentiation system has been employed to decipher mechanisms of pancreatic development, congenital defects of the pancreas, as well as genetic forms of diabetes and exocrine diseases. In this review, we summarize recent insights gained from studies of pancreatic hPSC models. We discuss how genome-scale analyses of the differentiation system have helped elucidate roles of chromatin state, transcription factors, and noncoding RNAs in pancreatic development and how the analysis of cells with disease-relevant mutations has provided insight into the molecular underpinnings of genetically determined diseases of the pancreas.

The long non-coding RNA LncHDAC2 drives the self-renewal of liver cancer stem cells via activation of Hedgehog signaling

BACKGROUND & AIMS

Liver cancer is the second leading cause of cancer death worldwide. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults. The aim of this study was to define the role of the long non-coding RNA lncHDAC2 in the tumorigenesis of HCC.

METHODS

CD13⁺CD133⁺ cells (hereafter called liver cancer stem cells [CSCs]) and CD13^-CD133^- cells (referred to as non-CSCs) were sorted from 3 primary HCC tumor tissues and followed by transcriptome microarray. The expression and function of lncHDAC2 were further assessed by northern blot, sphere formation and xenograft tumor models.

RESULTS

LncHDAC2 is highly expressed in HCC tumors and liver CSCs. LncHDAC2 promotes the self-renewal of liver CSCs and tumor propagation. In liver CSCs, lncHDAC2 recruits the NuRD complex onto the promoter of PTCH1 to inhibit its expression, leading to activation of Hedgehog signaling. Moreover, HDAC2 expression levels are positively related to HCC severity and PTCH1 levels are negatively related to HCC severity. Additionally, the Smo inhibitor cyclopamine was shown to impair the self-renewal of liver CSCs and suppress tumor propagation.

CONCLUSION

Our findings reveal that lncHDAC2 promotes the self-renewal of liver CSCs and tumor propagation by activating the Hedgehog signaling pathway. Downregulating lncHDAC2 is a promising antitumor strategy in HCC.

LAY SUMMARY

Liver cancer stem cells harbor high tumor-initiating potential and confer resistance to typical therapies, but the mechanism underlying their self-renewal remains elusive. LncHDAC2 augments the self-renewal of these cells, promoting tumor propagation. In liver cancer stem cells, lncHDAC2 activates Hedgehog signaling to initiate liver tumorigenesis. Therefore, lncHDAC2 and the Hedgehog signaling pathway may serve as biomarkers and potential drug targets for hepatocellular carcinoma.

Pancreatic duct-like cell line derived from pig embryonic stem cells: expression of uroplakin genes in pig pancreatic tissue

The isolation of a cell line, PICM-31D, with phenotypic characteristics like pancreatic duct cells is described. The PICM-31D cell line was derived from the previously described pig embryonic stem cell-derived exocrine pancreatic cell line, PICM-31. The PICM-31D cell line was morphologically distinct from the parental cells in growing as a monolayer rather than self-assembling into multicellular acinar-like structures. The PICM-31D cells were propagated for over a year at split ratios of 1:3 to 1:10 at each passage without change in phenotype or growth rate. Electron microscopy showed the cells to be a polarized epithelium of cuboidal cells joined by tight junction-like adhesions at their apical/lateral aspect. The cells contained numerous mucus-like secretory vesicles under their apical cell membrane. Proteomic analysis of the PICM-31D's cellular proteins detected MUC1 and MUC4, consistent with mucus vesicle morphology. Gene expression analysis showed the cells expressed pancreatic ductal cell-related transcription factors such as GATA4, GATA6, HES1, HNF1A, HNF1B, ONECUT1 (HNF6), PDX1, and SOX9, but little or no pancreas progenitor cell markers such as PTF1A, NKX6-1, SOX2, or NGN3. Pancreas ductal cell-associated genes including CA2, CFTR, MUC1, MUC5B, MUC13, SHH, TFF1, KRT8, and KRT19 were expressed by the PICM-31D cells, but the exocrine pancreas marker genes, CPA1 and PLA2G1B, were not expressed by the cells. However, the exocrine marker, AMY2A, was still expressed by the cells. Surprisingly, uroplakin proteins were prominent in the PICM-31D cell proteome, particularly UPK1A. Annexin A1 and A2 proteins were also relatively abundant in the cells. The expression of the uroplakin and annexin genes was detected in the cells, although only UPK1B, UPK3B, ANXA2, and ANXA4 were detected in fetal pig pancreatic duct tissue. In conclusion, the PICM-31D cell line models the mucus-secreting ductal cells of the fetal pig pancreas.

Pluripotent Stem Cell-Derived Pancreatic Progenitors and β-Like Cells for Type 1 Diabetes Treatment

In this review, we focus on the processes guiding human pancreas development and provide an update on methods to efficiently generate pancreatic progenitors (PPs) and β-like cells in vitro from human pluripotent stem cells (hPSCs). Furthermore, we assess the strengths and weaknesses of using PPs and β-like cell for cell replacement therapy for the treatment of Type 1 diabetes with respect to cell manufacturing, engrafting, functionality, and safety. Finally, we discuss the identification and use of specific cell surface markers to generate safer populations of PPs for clinical translation and to study the development of PPs in vivo and in vitro.

Neurog3-dependent pancreas dysgenesis causes ectopic pancreas in Hes1 mutant mice

Mutations in Hes1, a target gene of the Notch signalling pathway, lead to ectopic pancreas by a poorly described mechanism. Here, we use genetic inactivation of Hes1 combined with lineage tracing and live imaging to reveal an endodermal requirement for Hes1, and show that ectopic pancreas tissue is derived from the dorsal pancreas primordium. RNA-seq analysis of sorted E10.5 Hes1^+/+ and Hes1^-/- Pdx1-GFP⁺ cells suggested that upregulation of endocrine lineage genes in Hes1^-/- embryos was the major defect and, accordingly, early pancreas morphogenesis was normalized, and the ectopic pancreas phenotype suppressed, in Hes1^-/-Neurog3^-/- embryos. In Mib1 mutants, we found a near total depletion of dorsal progenitors, which was replaced by an anterior Gcg⁺ extension. Together, our results demonstrate that aberrant morphogenesis is the cause of ectopic pancreas and that a part of the endocrine differentiation program is mechanistically involved in the dysgenesis. Our results suggest that the ratio of endocrine lineage to progenitor cells is important for morphogenesis and that a strong endocrinogenic phenotype without complete progenitor depletion, as seen in Hes1 mutants, provokes an extreme dysgenesis that causes ectopic pancreas.

Mesodermal induction of pancreatic fate commitment

The pancreas is a compound gland comprised of both exocrine acinar and duct cells as well as endocrine islet cells. Most notable amongst the latter are the insulin-synthesizing β-cells, loss or dysfunction of which manifests in diabetes mellitus. All exocrine and endocrine cells derive from multipotent pancreatic progenitor cells arising from the primitive gut epithelium via inductive interactions with adjacent mesodermal tissues. Research in the last two decades has revealed the identity of many of these extrinsic cues and they include signaling molecules used in many other developmental contexts such as retinoic acid, fibroblast growth factors, and members of the TGF-β superfamily. As important as these inductive cues is the absence of other signaling molecules such as hedgehog family members. Much has been learned about the interactions of extrinsic factors with fate regulators intrinsic to the pancreatic endoderm. This new knowledge has had tremendous impact on the development of directed differentiation protocols for converting pluripotent stem cells to β-cells in vitro.

Secretagogin protects Pdx1 from proteasomal degradation to control a transcriptional program required for β cell specification

OBJECTIVE

Specification of endocrine cell lineages in the developing pancreas relies on extrinsic signals from non-pancreatic tissues, which initiate a cell-autonomous sequence of transcription factor activation and repression switches. The steps in this pathway share reliance on activity-dependent Ca²⁺ signals. However, the mechanisms by which phasic Ca²⁺ surges become converted into a dynamic, cell-state-specific and physiologically meaningful code made up by transcription factors constellations remain essentially unknown.

METHODS

We used high-resolution histochemistry to explore the coincident expression of secretagogin and transcription factors driving β cell differentiation. Secretagogin promoter activity was tested in response to genetically manipulating Pax6 and Pax4 expression. Secretagogin null mice were produced with their pancreatic islets morphologically and functionally characterized during fetal development. A proteomic approach was utilized to identify the Ca²⁺-dependent interaction of secretagogin with subunits of the 26S proteasome and verified in vitro by focusing on Pdx1 retention.

RESULTS

Here, we show that secretagogin, a Ca²⁺ sensor protein that controls α and β cell turnover in adult, is in fact expressed in endocrine pancreas from the inception of lineage segregation in a Pax4-and Pax6-dependent fashion. By genetically and pharmacologically manipulating secretagogin expression and interactome engagement in vitro, we find secretagogin to gate excitation-driven Ca²⁺ signals for β cell differentiation and insulin production. Accordingly, secretagogin^-/- fetuses retain a non-committed pool of endocrine progenitors that co-express both insulin and glucagon. We identify the Ca²⁺-dependent interaction of secretagogin with subunits of the 26S proteasome complex to prevent Pdx1 degradation through proteasome inactivation. This coincides with retained Nkx6.1, Pax4 and insulin transcription in prospective β cells.

CONCLUSIONS

In sum, secretagogin scales the temporal availability of a Ca²⁺-dependent transcription factor network to define β cell identity.

αE-Catenin Is a Positive Regulator of Pancreatic Islet Cell Lineage Differentiation

The development and function of epithelia depend on the establishment and maintenance of cell-cell adhesion and intercellular junctions, which operate as mechanosensor hubs for the transduction of biochemical signals regulating cell proliferation, differentiation, survival, and regeneration. Here, we show that αE-catenin, a key component of adherens junctions, functions as a positive regulator of pancreatic islet cell lineage differentiation by repressing the sonic hedgehog pathway (SHH). Thus, deletion of αE-catenin in multipotent pancreatic progenitors resulted in (1) loss of adherens junctions, (2) constitutive activation of SHH, (3) decrease in islet cell lineage differentiation, and (4) accumulation of immature Sox9⁺ progenitors. Pharmacological blockade of SHH signaling in pancreatic organ cultures and in vivo rescued this defect, allowing αE-catenin-null Sox9⁺ pancreatic progenitors to differentiate into endocrine cells. The results uncover crucial functions of αE-catenin in pancreatic islet development and harbor significant implications for the design of β cell replacement and regeneration therapies in diabetes.

A novel role for cilia-dependent sonic hedgehog signaling during submandibular gland development

BACKGROUND

Submandibular glands (SMGs) are specialized epithelial structures which generate saliva necessary for mastication and digestion. Loss of SMGs can lead to inflammation, oral lesions, fungal infections, problems with chewing/swallowing, and tooth decay. Understanding the development of the SMG is important for developing therapeutic options for patients with impaired SMG function. Recent studies have suggested Sonic hedgehog (Shh) signaling in the epithelium plays an integral role in SMG development; however, the mechanism by which Shh influences gland development remains nebulous.

RESULTS

Using the Kif3a^f/f ;Wnt1-Cre ciliopathic mouse model to prevent Shh signal transduction by means of the loss of primary cilia in neural crest cells, we report that mesenchymal Shh activity is necessary for gland development. Furthermore, using a variety of murine transgenic lines with aberrant mesenchymal Shh signal transduction, we determine that loss of Shh activity, by means of loss of the Gli activator, rather than gain of Gli repressor, is sufficient to cause the SMG aplasia. Finally, we determine that loss of the SMG correlates with reduced Neuregulin1 (Nrg1) expression and lack of innervation of the SMG epithelium.

CONCLUSIONS

Together, these data suggest a novel mechanistic role for mesenchymal Shh signaling during SMG development. Developmental Dynamics 247:818-831, 2018. © 2018 Wiley Periodicals, Inc.

Stroma - A Double-Edged Sword in Pancreatic Cancer: A Lesson From Targeting Stroma in Pancreatic Cancer With Hedgehog Signaling Inhibitors

Pancreatic cancer is a uniformly lethal malignancy with an abundant dense desmoplastic stroma. Because of its dense stroma, conventional drugs were considered to not penetrate this physical barrier, and this caused a systemic drug resistance. Thus, abolishing this barrier with targeted agents is considered to improve the efficiency of chemotherapeutic treatment. The Hedgehog (Hh) signaling pathway is a critical regulator of pancreas development and plays diversified roles in pancreatic cancer stroma and neoplastic cells. Increasing Hh expression in neoplastic cells added desmoplastic stroma accumulation in orthotopic tumors, and Hh inhibitors that target the stroma have an ability to prolong the overall survival of Pdx-1-Cre/KrasG12D/p53R172H mice models via deleting the stromal components and increasing vascularity in pancreatic tumor. However, the failure of translation from bench to bedside indicate the complexity of the relationship between Hh signaling and desmoplastic stroma, and more insights into the complex relationships between Hh signaling pathway and stroma, even tumor cells, might help redesign Hh-targeted therapy. In this review, we discuss the possible mechanism of translation of Hh inhibitor in the clinic from pathology to molecular mechanism.

Sending mixed signals: Cilia-dependent signaling during development and disease

Molecular signals are the guiding force of development, imparting direction upon cells to divide, migrate, differentiate, etc. The mechanisms by which a cell can receive and transduce these signals into measurable actions remains a 'black box' in developmental biology. Primary cilia are ubiquitous, microtubule-based organelles that dynamically extend from a cell to receive and process molecular and mechanical signaling cues. In the last decade, this organelle has become increasingly intriguing to the research community due to its ability to act as a cellular antenna, receive and transduce molecular stimuli, and initiate a cellular response. In this review, we discuss the structure of primary cilia, emphasizing how the ciliary components contribute to the transduction of signaling pathways. Furthermore, we address how the cilium integrates these signals and conveys them into cellular processes such as proliferation, migration and tissue patterning. Gaining a deeper understanding of the mechanisms used by primary cilia to receive and integrate molecular signals is essential, as it opens the door for the identification of therapeutic targets within the cilium that could alleviate pathological conditions brought on by aberrant molecular signaling.

Histomorphometry of pancreas development in hybrid chicken (Galus galus) embryo and fetus

The pancreas comprises an important metabolic organ of endocrine and exocrine character that has embryonic origin of rudimentary buds that fuse to form the organ. The present work aims to describe the pancreatic histogenesis of hybrid chick embryos (Gallus gallus). The research was performed in the UFPI, previously approved by the CEUA with protocol no. 040/15. We used 120 fertilized eggs of hybrid chickens kept in an incubator with controlled temperature and humidity. Daily collections of embryos and fetuses were performed from 4 to 21 days of incubation through the anatomical dissection consecutive the euthanasia. The tissues, previously fixed in 10% buffered formaldehyde, were submitted to histological processing and stained with hematoxylin-eosin. Finally, the mounted slides were analyzed in image software to obtain histomorphometric data, which were submitted to statistical analysis. The pancreas of hybrid chicken embryos originates around the fourth day of incubation with the dorsal and ventral pancreatic bud formation, which are composed by epithelial and mesenchymal cells. These cells differ in exocrine and endocrine cells. Around twelve embryonic days occurs the buds fusion and the immature organ formation that will give continue with the ductal system development, vascularization and compartmentalization of the endocrine and exocrine parts. Until 21st day of incubation it is possible to identify undifferentiated tissue forms which suggesting postnatal histogenesis. The description of pancreas histogenesis using histometric data on hybrid chicken embryos contributes to the clarification of embryonic development and reaffirms the premise that chickens serve as an experimental model for embryonic study of mammals.

The combined effect of Pdx1 overexpression and Shh manipulation on the function of insulin-producing cells derived from adipose-tissue stem cells

Pancreatic and duodenal homeobox 1 (Pdx1) and Sonic hedgehog (Shh) are the key regulators of beta-cell function. In vitro experiments have shown that there is significant cooperation between Pdx1 and Shh with regard to the production and maintenance of insulin-producing cells (IPCs). In this study, the combined effect of Pdx1 overexpression and Shh manipulation on the function of adipose tissue-derived IPCs was determined. A eukaryotic expression vector (Pdx1- pCDNA3.1(+)) was constructed and transfected into a Chinese hamster ovary (CHO) cell line. Adipose tissue-derived mesenchymal stem cells (ADMSCs) obtained from rats were assigned to two groups [control (C) and manipulated (M)] and differentiated into IPCs. Manipulated cells were treated with a mixture of FGF-β and cyclopamine and recombinant Shh protein at days 3 and 11, respectively, and transfected with Pdx1- pCDNA3.1(+) at day 10. The expression of multiple genes related to function of beta cells was analyzed using real-time PCR. The functionality of IPCs in vitro was analyzed through dithizone (DTZ) staining and ELISA. IPCs were injected into the tail vein of diabetic rats, and blood glucose and insulin concentrations were measured. CHO cells transfected with Pdx1- pCDNA3.1(+) showed a significantly higher expression of Pdx1 compared with nontransfected cells. Manipulated IPCs exhibited a significantly higher expression of MafA, Nkx2.2, Nkx6.1, Ngn3, insulin, and Isl1 and a higher insulin secretion in response to glucose challenge in relation to control cells. Rats that received manipulated IPCs exhibited a higher ability to normalize blood glucose and insulin secretion when compared to controls. Our protocol might be used for more efficient cell therapy of patients with diabetes in the future.

Identification and fate mapping of the pancreatic mesenchyme

The murine pancreas buds from the ventral embryonic endoderm at approximately 8.75 dpc and a second pancreas bud emerges from the dorsal endoderm by 9.0 dpc. Although it is clear that secreted signals from adjacent mesoderm-derived sources are required for both the appropriate emergence and further refinement of the pancreatic endoderm, neither the exact signals nor the requisite tissue sources have been defined in mammalian systems. Herein we use DiI fate mapping of cultured murine embryos to identify the embryonic sources of both the early inductive and later condensed pancreatic mesenchyme. Despite being capable of supporting pancreas induction from dorsal endoderm in co-culture experiments, we find that in the context of the developing embryo, the dorsal aortae as well as the paraxial, intermediate, and lateral mesoderm derivatives only transiently associate with the dorsal pancreas bud, producing descendants that are decidedly anterior to the pancreas bud. Unlike these other mesoderm derivatives, the axial (notochord) descendants maintain association with the dorsal pre-pancreatic endoderm and early pancreas bud. This fate mapping data points to the notochord as the likely inductive source in vivo while also revealing dynamic morphogenetic movements displayed by individual mesodermal subtypes. Because none of the mesoderm examined above produced the pancreatic mesenchyme that condenses around the induced bud to support exocrine and endocrine differentiation, we also sought to identify the mesodermal origins of this mesenchyme. We identify a portion of the coelomic mesoderm that contributes to the condensed pancreatic mesenchyme. In conclusion, we identify a portion of the notochord as a likely source of the signals required to induce and maintain the early dorsal pancreas bud, demonstrate that the coelomic mesothelium contributes to the dorsal and ventral pancreatic mesenchyme, and provide insight into the dynamic morphological rearrangements of mesoderm-derived tissues during early organogenesis stages of mammalian development.

Heterotopic pancreatic cyst in the adrenal gland: A case report and review of literature

RATIONALE

The incidence of heterotopic pancreas (HP) is relatively rare and mainly found in the upper gastrointestinal tract, and no case of HP cyst in the adrenal gland has been reported. Informed consent has been obtained from the patient for the publication of the case details.

PATIENT CONCERNS

A 21-year-old woman who presented with chronic lower back pain for a week without urinary disturbance or gastrointestinal discomfortable.

DIAGNOSES

Ultrasound (US) revealed a left renal cyst, and computed tomography (CT) showed a cyst in the area of the adrenal gland.

INTERVENTIONS

Cystectomy was successfully performed laparoscopically. Histopathologic examination of the removed cyst wall showed heterotopic pancreatic cyst accompanied by cystic degeneration.

OUTCOMES

No unusual drainage or abdominal signs were observed during the 6-month follow-up.

LESSONS

Despite of its rarity, HP accompanied by cyst formation in the adrenal gland area can present with waist pain. Therefore, the possibility of such disease needs to be considered. For thorough evaluation, in addition to abdominal US, CT, and/or magnetic resonance imaging, histopathological examination should sometimes be performed to make a definite diagnosis. Total excision and regular follow-up is necessary for such cases due to the potential risk of complications or recurrent cyst formation.

Pancreatic fibroblasts smoothen their activities via AKT-GLI2-TGFα

This Outlook discusses the finding by Liu et al. that disruption of paracrine Hedgehog signaling via genetic ablation of Smoothened (Smo) in stromal fibroblasts in a Kras^G12D mouse model increases acinar-to-ductal metaplasia.

Pancreatic stromal fibroblasts provide structural support. Activated fibroblasts are critical in the tumor microenvironment. In this issue of Genes & Development, Liu and colleagues (pp. 1943–1955) unravel the finding that depletion of Smoothened (Smo) in pancreatic stromal fibroblasts results in AKT activation and noncanonical GLI2 activation with subsequent TGFα secretion, activation of EGFR in pancreatic epithelial cells, and augmentation of acinar–ductal metaplasia. Additionally, Smo-mediated signaling has proproliferative effects on pancreatic tumor cells.

Heterotopic Pancreas: Histopathologic Features, Imaging Findings, and Complications

Heterotopic pancreas is a congenital anomaly in which pancreatic tissue is anatomically separate from the main gland. The most common locations of this displacement include the upper gastrointestinal tract-specifically, the stomach, duodenum, and proximal jejunum. Less common sites are the esophagus, ileum, Meckel diverticulum, biliary tree, mesentery, and spleen. Uncomplicated heterotopic pancreas is typically asymptomatic, with the lesion being discovered incidentally during an unrelated surgery, during an imaging examination, or at autopsy. The most common computed tomographic appearance of heterotopic pancreas is that of a small oval intramural mass with microlobulated margins and an endoluminal growth pattern. The attenuation and enhancement characteristics of these lesions parallel their histologic composition. Acinus-dominant lesions demonstrate avid homogeneous enhancement after intravenous contrast material administration, whereas duct-dominant lesions are hypovascular and heterogeneous. At magnetic resonance imaging, the heterotopic pancreas is isointense to the orthotopic pancreas, with characteristic T1 hyperintensity and early avid enhancement after intravenous gadolinium-based contrast material administration. Heterotopic pancreatic tissue has a rudimentary ductal system in which an orifice is sometimes visible at imaging as a central umbilication of the lesion. Complications of heterotopic pancreas include pancreatitis, pseudocyst formation, malignant degeneration, gastrointestinal bleeding, bowel obstruction, and intussusception. Certain complications may be erroneously diagnosed as malignancy. Paraduodenal pancreatitis is thought to be due to cystic degeneration of heterotopic pancreatic tissue in the medial wall of the duodenum. Recognizing the characteristic imaging features of heterotopic pancreas aids in differentiating it from cancer and thus in avoiding unnecessary surgery. ^© RSNA, 2017.

The Stromal Niche for Epithelial Stem Cells: A Template for Regeneration and a Brake on Malignancy

Stromal restraint of cancer growth and progression-emerging as a widespread phenomenon in epithelial cancers such as bladder, pancreas, colon, and prostate-appears rooted in stromal cell niche activity. During normal tissue repair, stromal niche signals, often Hedgehog-induced, promote epithelial stem cell differentiation as well as self-renewal, thus specifying a regenerating epithelial pattern. In the case of cancerous tissue, stromal cell-derived differentiation signals in particular may provide a brake on malignant growth. Understanding and therapeutic harnessing of the role of stroma in cancer restraint may hinge on our knowledge of the signaling programs elaborated by the stromal niche.

Development of the thyroid gland

Thyroid hormones are crucial for organismal development and homeostasis. In humans, untreated congenital hypothyroidism due to thyroid agenesis inevitably leads to cretinism, which comprises irreversible brain dysfunction and dwarfism. Elucidating how the thyroid gland - the only source of thyroid hormones in the body - develops is thus key for understanding and treating thyroid dysgenesis, and for generating thyroid cells in vitro that might be used for cell-based therapies. Here, we review the principal mechanisms involved in thyroid organogenesis and functional differentiation, highlighting how the thyroid forerunner evolved from the endostyle in protochordates to the endocrine gland found in vertebrates. New findings on the specification and fate decisions of thyroid progenitors, and the morphogenesis of precursor cells into hormone-producing follicular units, are also discussed.

New paradigms for the Hedgehog signaling network in mammary gland development and breast Cancer

The Hedgehog signaling network regulates organogenesis, cell fate, proliferation, survival, and stem cell self-renewal in many mammalian tissues. Aberrant activation of the Hedgehog signaling network is present in ~25% of all cancers, including breast. Altered expression of Hedgehog network genes in the mammary gland can elicit phenotypes at many stages of development. However, synthesizing a cohesive mechanistic model of signaling at different stages of development has been difficult. Emerging data suggest that this difficulty is due, in part, to non-canonical and tissue compartment-specific (i.e., epithelial, versus stromal, versus systemic) functions of Hedgehog network components. With respect to systemic functions, Hedgehog network genes regulate development of endocrine organs that impinge on mammary gland development extrinsically. These new observations offer insight into previously conflicting data, and have bearing on the potential for anti-Hedgehog therapeutics in the treatment of breast cancer.

Human pluripotent stem cell differentiation to functional pancreatic cells for diabetes therapies: Innovations, challenges and future directions

Recent advances in the expansion and directed pancreatogenic differentiation of human pluripotent stem cells (hPSCs) have intensified efforts to generate functional pancreatic islet cells, especially insulin-secreting β-cells, for cell therapies against diabetes. However, the consistent generation of glucose-responsive insulin-releasing cells remains challenging. In this article, we first present basic concepts of pancreatic organogenesis, which frequently serves as a basis for engineering differentiation regimens. Next, past and current efforts are critically discussed for the conversion of hPSCs along pancreatic cell lineages, including endocrine β-cells and α-cells, as well as exocrine cells with emphasis placed on the later stages of commitment. Finally, major challenges and future directions are examined, such as the identification of factors for in vivo maturation, large-scale culture and post processing systems, cell loss during differentiation, culture economics, efficiency, and efficacy and exosomes and miRNAs in pancreatic differentiation.

Epithelial and non-epithelial Ptch1 play opposing roles to regulate proliferation and morphogenesis of the mouse mammary gland

Patched 1 (Ptch1) has epithelial, stromal and systemic roles in murine mammary gland organogenesis, yet specific functions remain undefined. Cre-recombinase-mediated Ptch1 ablation in mammary epithelium increased proliferation and branching, but did not phenocopy transgenic expression of activated smoothened (SmoM2). The epithelium showed no evidence of canonical hedgehog signaling, and hyperproliferation was not blocked by smoothened (SMO) inhibition, suggesting a non-canonical function of PTCH1. Consistent with this possibility, nuclear localization of cyclin B1 was increased. In non-epithelial cells, heterozygous Fsp-Cre-mediated Ptch1 ablation increased proliferation and branching, with dysplastic terminal end buds (TEB) and ducts. By contrast, homozygous Ptch1 ablation decreased proliferation and branching, producing stunted ducts filled with luminal cells showing altered ovarian hormone receptor expression. Whole-gland transplantation into wild-type hosts or estrogen/progesterone treatment rescued outgrowth and hormone receptor expression, but not the histological changes. Bone marrow transplantation failed to rescue outgrowth. Ducts of Fsp-Cre;Ptch1^fl/fl mice were similar to Fsp-Cre;SmoM2 ducts, but Fsp-Cre;SmoM2 outgrowths were not stunted, suggesting that the histology might be mediated by Smo in the local stroma, with systemic Ptch1 required for ductal outgrowth and proper hormone receptor expression in the mammary epithelium.

Summary: Systemic and tissue-specific depletion of patched 1 in epithelial and stromal compartments of the mammary gland defines functions in ductal patterning, proliferation and gene expression.

The molecular and morphogenetic basis of pancreas organogenesis

The pancreas is an essential endoderm-derived organ that ensures nutrient metabolism via its endocrine and exocrine functions. Here we review the essential processes governing the embryonic and early postnatal development of the pancreas discussing both the mechanisms and molecules controlling progenitor specification, expansion and differentiation. We elaborate on how these processes are orchestrated in space and coordinated with morphogenesis. We draw mainly from experiments conducted in the mouse model but also from investigations in other model organisms, complementing a recent comprehensive review of human pancreas development (Jennings et al., 2015) [1]. The understanding of pancreas development in model organisms provides a framework to interpret how human mutations lead to neonatal diabetes and may contribute to other forms of diabetes and to guide the production of desired pancreatic cell types from pluripotent stem cells for therapeutic purposes.

Pancreatic Mesenchyme Regulates Islet Cellular Composition in a Patched/Hedgehog-Dependent Manner

Pancreas development requires restrained Hedgehog (Hh) signaling activation. While deregulated Hh signaling in the pancreatic mesenchyme has been long suggested to be detrimental for proper organogenesis, this association was not directly shown. Here, we analyzed the contribution of mesenchymal Hh signaling to pancreas development. To increase Hh signaling in the pancreatic mesenchyme of mouse embryos, we deleted Patched1 (Ptch1) in these cells. Our findings indicate that deregulated Hh signaling in mesenchymal cells was sufficient to impair pancreas development, affecting both endocrine and exocrine cells. Notably, transgenic embryos displayed disrupted islet cellular composition and morphology, with a reduced β-cell portion. Our results indicate that the cell-specific growth rates of α- and β-cell populations, found during normal development, require regulated mesenchymal Hh signaling. In addition, we detected hyperplasia of mesenchymal cells upon elevated Hh signaling, accompanied by them acquiring smooth-muscle like phenotype. By specifically manipulating mesenchymal cells, our findings provide direct evidence for the non-autonomous roles of the Hh pathway in pancreatic epithelium development. To conclude, we directly show that regulated mesenchymal Hh signaling is required for pancreas organogenesis and establishment of its proper cellular composition.

GATA4 and GATA6 regulate pancreatic endoderm identity through inhibition of hedgehog signaling

GATA4 and GATA6 are zinc finger transcription factors that have important functions in several mesodermal and endodermal organs, including heart, liver and pancreas. In humans, heterozygous mutations of either factor are associated with pancreatic agenesis; however, homozygous deletion of both Gata4 and Gata6 is necessary to disrupt pancreas development in mice. In this study, we demonstrate that arrested pancreatic development in Gata4(fl/fl); Gata6(fl/fl); Pdx1:Cre (pDKO) embryos is accompanied by the transition of ventral and dorsal pancreatic fates into intestinal or stomach lineages, respectively. These results indicate that GATA4 and GATA6 play essential roles in maintaining pancreas identity by regulating foregut endodermal fates. Remarkably, pancreatic anlagen derived from pDKO embryos also display a dramatic upregulation of hedgehog pathway components, which are normally absent from the presumptive pancreatic endoderm. Consistent with the erroneous activation of hedgehog signaling, we demonstrate that GATA4 and GATA6 are able to repress transcription through the sonic hedgehog (Shh) endoderm-specific enhancer MACS1 and that GATA-binding sites within this enhancer are necessary for this repressive activity. These studies establish the importance of GATA4/6-mediated inhibition of hedgehog signaling as a major mechanism regulating pancreatic endoderm specification during patterning of the gut tube.

Pancreatic regeneration: basic research and gene regulation

Pancreatic regeneration (PR) is an interesting phenomenon that could provide clues as to how the control of diabetes mellitus might be achieved. Due to the different regenerative abilities of the pancreas and liver, the molecular mechanism responsible for PR is largely unknown. In this review, we describe five representative murine models of PR and thirteen humoral mitogens that stimulate β-cell proliferation. We also describe pancreatic ontogenesis, including the molecular transcriptional differences between α-cells and β-cells. Furthermore, we review 14 murine models which carry defects in genes related to key transcription factors for pancreatic ontogenesis to gain further insight into pancreatic development.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Exosome-like vesicles released from lipid-induced insulin-resistant muscles modulate gene expression and proliferation of beta recipient cells in mice

AIMS/HYPOTHESIS

The crosstalk between skeletal muscle (SkM) and beta cells plays a role in diabetes aetiology. In this study, we have investigated whether SkM-released exosome-like vesicles (ELVs) can be taken up by pancreatic beta cells and can deliver functional cargoes.

METHODS

Mice were fed for 16 weeks with standard chow diet (SCD) or with standard diet enriched with 20% palmitate (HPD) and ELVs were purified from quadriceps muscle. Fluorescent ELVs from HPD or SCD quadriceps were injected i.v. or intramuscularly (i.m.) into mice to determine their biodistributions. Micro (mi)RNA quantification in ELVs was determined using quantitative real-time RT-PCR (qRT-PCR)-based TaqMan low-density arrays. Microarray analyses were performed to determine whether standard diet ELVs (SD-ELVs) and high palmitate diet ELVs (HPD-ELVs) induced specific transcriptional signatures in MIN6B1 cells.

RESULTS

In vivo, muscle ELVs were taken up by pancreas, 24 h post-injection. In vitro, both SD-ELVs and HPD-ELVs transferred proteins and miRNAs to MIN6B1 cells and modulated gene expressions whereas only HPD-ELVs induced proliferation of MIN6B1 cells and isolated islets. Bioinformatic analyses suggested that transferred HPD-ELV miRNAs may participate in these effects. To validate this, we demonstrated that miR-16, which is overexpressed in HPD-ELVs, was transferred to MIN6B1 cells and regulated Ptch1, involved in pancreas development. In vivo, islets from HPD mice showed increased size and altered expression of genes involved in development, including Ptch1, suggesting that the effect of palm oil on islet size in vivo was reproduced in vitro by treating beta cells with HPD-ELVs.

CONCLUSIONS/INTERPRETATION

Our data suggest that muscle ELVs might have an endocrine effect and could participate in adaptations in beta cell mass during insulin resistance.