FGF signaling in specification of hESC-derived definitive endoderm

Diabetes affects around 200 million people worldwide. Curing diabetes would require the prevention of autoimmune destruction of beta cells and restoration of the beta cell mass restored either through regeneration or transplantation of the insulin producing cells. Islet transplantation according to the Edmonton protocol have been the most promising therapeutic option for Diabetes type I patients, however, lack of cadaveric donor islets is a major obstacle and new strategies need to be established. Human embryonic stem cells (hESCs) not only offer an excellent source for establishment of strategies for future regenerative cell therapies and drug discovery but also offers en excellent experimental assay for understanding human pancreas development. Pancreas originates from the definitive endoderm (DE), one of the three germ layers. The path from definitive endoderm to pancreatic progenitor cells and finally the insulin producing beta cells involves sequential cell-fate decisions characterized by the expression of multiple transcription factors. Governed by the developmental biological principles that normally control foregut endoderm and pancreas specification, numerous multifactor protocols for directing mature foregut-derived cells from hESCs have been reported. However, to establish less complex and more robust protocols there is a need to further understand the mechanism of action of individual growth and differentiation factors in specification of human pluripotent stem cells towards foregut derived cell lineages. Here, we describe two studies where we have investigated the role of fibroblast growth factor (FGF) signaling, specifically FGF2 and FGF4, and Retinoic acid (RA) in specification of the hESC-derived DE development. Studies in lower vertebrates have demonstrated that FGF2 acts in a restricted manner primarily patterning the ventral foregut endoderm into liver and lung, whereas FGF4 exhibits broad anteriorposterior and left-right patterning activities. Furthermore, whereas FGF2 is not required for ventral pancreas development an inductive role of FGF2 has been shown during dorsal pancreas formation. Whether FGF2 and FGF4 play a similar role during human endoderm development remained however unknown. In contrast, RA has frequently been employed (together with other growth factors) for directed differentiation of hESCs to pancreatic endoderm. In the first study we show that FGF2 in a dosage-dependent manner specifies hESC-derived DE into different foregut lineages such as liver, lung, pancreatic and intestinal cells. Furthermore, by dissecting the FGF receptor intracellular pathway that regulates pancreas specification, we demonstrate for the first time to our knowledge that induction of PDX1+ pancreatic progenitors in part relies on 8 FGF2-mediated activation of the MAPK signaling pathway. In the second study, we show that FGF4 alone is not sufficient for induction of foregut endoderm but that in combination with RA it efficiently induces PDX1+ cells from hESC-derived DE. Specifically, FGF4 promoted cell survival in the differentiating hESCs. Hence, in contrast to studies in lower vertebrates we demonstrate that FGF4 neither patterns hESC-derived DE, nor induces PDX1+ pancreatic progenitors suggesting that FGF4 is not responsible for anterior-posterior patterning of the primitive gut during human development.. Altogether, these observations suggest a broader gut endodermal patterning activity of FGF2 that corresponds to what has previously been advocated for FGF4, implying a functional switch from FGF4 to FGF2 during evolution. Thus, our results provide new knowledge of how cell fate specification of human DE is controlled – facts that will be of great value for future regenerative cell therapies. Finally, we present a method for efficient gene targeting in hESCs, which allows the monitoring of gene expression in living cells

NANOG Reporter Cell Lines Generated by Gene Targeting in Human Embryonic Stem Cells

Background: Pluripotency and self-renewal of human embryonic stem cells (hESCs) is mediated by a complex interplay between extra- and intracellular signaling pathways, which regulate the expression of pluripotency-specific transcription factors. The homeodomain transcription factor NANOG plays a central role in maintaining hESC pluripotency, but the precise role and regulation of NANOG are not well defined. Methodology/Principal Findings: To facilitate the study of NANOG expression and regulation in viable hESC cultures, we generated fluorescent NANOG reporter cell lines by gene targeting in hESCs. In these reporter lines, the fluorescent reporter gene was co-expressed with endogenous NANOG and responded to experimental induction or repression of the NANOG promoter with appropriate changes in expression levels. Furthermore, NANOG reporter lines facilitated the separation of hESC populations based on NANOG expression levels and their subsequent characterization. Gene expression arrays on isolated hESC subpopulations revealed genes with differential expression in NANOG high and NANOG low hESCs, providing candidates for NANOG downstream targets hESCs. Conclusion/Significance: The newly derived NANOG reporter hESC lines present novel tools to visualize NANOG expression in viable hESCs. In future applications, these reporter lines can be used to elucidate the function and regulation of NANO

FGF4 and Retinoic Acid Direct Differentiation of hESCs into PDX1-Expressing Foregut Endoderm in a Time- and Concentration-Dependent Manner

BACKGROUND: Retinoic acid (RA) and fibroblast growth factor 4 (FGF4) signaling control endoderm patterning and pancreas induction/expansion. Based on these findings, RA and FGFs, excluding FGF4, have frequently been used in differentiation protocols to direct differentiation of hESCs into endodermal and pancreatic cell types. In vivo, these signaling pathways act in a temporal and concentration-dependent manner. However, in vitro, the underlying basis for the time of addition of growth and differentiation factors (GDFs), including RA and FGFs, as well as the concentration is lacking. Thus, in order to develop robust and reliable differentiation protocols of ESCs into mature pancreatic cell types, including insulin-producing beta cells, it will be important to mechanistically understand each specification step. This includes differentiation of mesendoderm/definitive endoderm into foregut endoderm--the origin of pancreatic endoderm. METHODOLOGY/PRINCIPAL FINDINGS: Here, we provide data on the individual and combinatorial role of RA and FGF4 in directing differentiation of ActivinA (AA)-induced hESCs into PDX1-expressing cells. FGF4's ability to affect endoderm patterning and specification in vitro has so far not been tested. By testing out the optimal concentration and timing of addition of FGF4 and RA, we present a robust differentiation protocol that on average generates 32% PDX1(+) cells. Furthermore, we show that RA is required for converting AA-induced hESCs into PDX1(+) cells, and that part of the underlying mechanism involves FGF receptor signaling. Finally, further characterization of the PDX1(+) cells suggests that they represent foregut endoderm not yet committed to pancreatic, posterior stomach, or duodenal endoderm. CONCLUSION/SIGNIFICANCE: In conclusion, we show that RA and FGF4 jointly direct differentiation of PDX1(+) foregut endoderm in a robust and efficient manner. RA signaling mediated by the early induction of RARbeta through AA/Wnt3a is required for PDX1 expression. Part of RA's activity is mediated by FGF signaling

Positional cloning of the Igl genes controlling rheumatoid factor production and allergic bronchitis in rats

Rheumatoid factors (RF), autoantibodies that bind the Fc region of IgG, are one of the major diagnostic marker in rheumatoid arthritis (RA) but occur with lower frequency also in other infectious and inflammatory conditions. Through positional cloning of the previously described quantitative trait locus (QTL) Rf1 in congenic and advanced intercrossed rats, we identified the Ig lambda light chain locus as a locus that regulates the production of RF in rats. The congenic rats produce RF-Ig lambda and have significant higher levels of RF-IgG and RF-IgM in serum, while the DA rat has an impaired RF production and does not produces RF-Ig lambda. Thus, we could investigate the role of RF in pristane-induced arthritis (PIA) as well as ovalbumin-induced airway inflammation. We show that there was no difference in the development and severity of PIA between congenic and parental DA rats, suggesting that RIP using lambda light chains have no impact on PIA. However, the RF producing congenic rats developed a more severe airway inflammation as indicated in the significantly increased number of eosinophils in bronchoalveolar lavage fluid as well as total IgE in serum. In addition, RF congenic rats had a significantly enhanced immune response toward OVA due to increased OVA-Igk but not OVA-IgI antibodies, suggesting a possible involvement of RF in the regulation of the humoral immune response

FGF2 Specifies hESC-Derived Definitive Endoderm into Foregut/Midgut Cell Lineages in a Concentration-Dependent Manner.

Fibroblast growth factor (FGF) signaling controls axis formation during endoderm development. Studies in lower vertebrates have demonstrated that FGF2 primarily patterns the ventral foregut endoderm into liver and lung, whereas FGF4 exhibits broad anterior-posterior and left-right patterning activities. Furthermore, an inductive role of FGF2 during dorsal pancreas formation has been shown. However, whether FGF2 plays a similar role during human endoderm development remains unknown. Here, we show that FGF2 specifies hESC-derived definitive endoderm (DE) into different foregut lineages in a dosage-dependent manner. Specifically, increasing concentrations of FGF2 inhibits hepatocyte differentiation, whereas intermediate concentration of FGF2 promotes differentiation towards a pancreatic cell fate. At high FGF2 levels specification of midgut endoderm into small intestinal progenitors is increased at the expense of PDX1+ pancreatic progenitors. High FGF2 concentrations also promote differentiation towards an anterior foregut pulmonary cell fate. Finally, by dissecting the FGF receptor intracellular pathway that regulates pancreas specification, we demonstrate for the first time to our knowledge that induction of PDX1+ pancreatic progenitors relies on FGF2-mediated activation of the MAPK signaling pathway. Altogether, these observations suggest a broader gut endodermal patterning activity of FGF2 that corresponds to what has previously been advocated for FGF4, implying a functional switch from FGF4 to FGF2 during evolution. Thus, our results provide new knowledge of how cell fate specification of human DE is controlled - facts that will be of great value for future regenerative cell therapies

Efficient Generation of Glucose-Responsive Beta Cells from Isolated GP2+ Human Pancreatic Progenitors

Stem cell-based therapy for type 1 diabetes would benefit from implementation of a cell purification step at the pancreatic endoderm stage. This would increase the safety of the final cell product, allow the establishment of an intermediate-stage stem cell bank, and provide a means for upscaling β cell manufacturing. Comparative gene expression analysis revealed glycoprotein 2 (GP2) as a specific cell surface marker for isolating pancreatic endoderm cells (PECs) from differentiated hESCs and human fetal pancreas. Isolated GP2+ PECs efficiently differentiated into glucose responsive insulin-producing cells in vitro. We found that in vitro PEC proliferation declines due to enhanced expression of the cyclin-dependent kinase (CDK) inhibitors CDKN1A and CDKN2A. However, we identified a time window when reducing CDKN1A or CDKN2A expression increased proliferation and yield of GP2+ PECs. Altogether, our results contribute tools and concepts toward the isolation and use of PECs as a source for the safe production of hPSC-derived β cells

Widefield OCT Findings of a Patient With Stellate Nonhereditary Idiopathic Foveomacular Retinoschisis

The authors report extensive peripheral retinoschisis in a patient with stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR) detected by widefield optical coherence tomography (OCT). A 64-year-old woman diagnosed with foveomacular retinoschisis 3 years prior presented for evaluation after being seen by multiple other retina specialists. Standard macular spectral-domain OCT (6 mm) revealed typical foveomacular schisis involving only the outer retina. However, widefield OCT (12 mm) revealed diffuse bilateral retinoschisis involving both inner and outer retinal layers in the macula and midperiphery. Widefield imaging is important to evaluate and monitor complex peripheral retinoschisis that may be otherwise undetectable using conventional techniques

Phosphoinositide 3-Kinase Gamma Inhibition Protects from Anthracycline Cardiotoxicity and Reduces Tumor Growth

reserved33Background - Anthracyclines, such as doxorubicin (DOX), are potent anti-cancer agents for the treatment of solid tumors and hematological malignancies. However, their clinical use is hampered by cardiotoxicity. This study sought to investigate the role of PI3Kγ in DOX-induced cardiotoxicity and the potential cardio-protective and anti-cancer effects of PI3Kγ inhibition. Methods - Mice expressing a kinase-inactive PI3Kγ or receiving PI3Kγ selective inhibitors were subjected to chronic DOX treatment. Cardiac function was analyzed by echocardiography and DOX-mediated signaling was assessed in whole hearts or in isolated cardiomyocytes. The dual cardio-protective and anti-tumor action of PI3Kγinhibition was assessed in mouse mammary tumor models. Results - PI3Kγ KD mice showed preserved cardiac function after chronic low-dose DOX treatment, and were protected against DOX-induced cardiotoxicity. The beneficial effects of PI3Kγ inhibition were causally linked to enhanced autophagic disposal of DOX-damaged mitochondria. Consistently, either pharmacological or genetic blockade of autophagyin vivoabrogated the resistance of PI3Kγ KD mice to DOX cardiotoxicity. Mechanistically, PI3Kγ was triggered in DOX-treated hearts, downstream of TLR9, by the mitochondrial DNA released by injured organelles, and contained in autolysosomes. This autolysosomal PI3Kγ/Akt/mTOR/Ulk1 signaling provided maladaptive feedback inhibition of autophagy. Finally, PI3Kγ blockade in models of mammary gland tumors prevented DOX-induced cardiac dysfunction, and concomitantly synergized with the anti-tumor action of DOX, by unleashing anticancer immunity. Conclusions - Blockade of PI3Kγ may provide a dual therapeutic advantage in cancer therapy, by simultaneously preventing anthracyclines cardiotoxicity and reducing tumor growth.mixedLi, Mingchuan; Sala, Valentina; De Santis, Maria Chiara; Cimino, James; Cappello, Paola; Pianca, Nicola; Di Bona, Anna; Margaria, Jean Piero; Martini, Miriam; Lazzarini, Edoardo; Pirozzi, Flora; Rossi, Luca; Franco, Irene; Bornbaum, Julia; Heger, Jacqueline; Rohrbach, Susanne; Perino, Alessia; Tocchetti, Carlo G; Lima, Braulio H F; Teixeira, Mauro M; Porporato, Paolo E; Schulz, Rainer; Angelini, Annalisa; Sandri, Marco; Ameri, Pietro; Sciarretta, Sebastiano; Lima-Júnior, Roberto César P; Mongillo, Marco; Zaglia, Tania; Morello, Fulvio; Novelli, Francesco; Hirsch, Emilio; Ghigo, AlessandraLi, Mingchuan; Sala, Valentina; De Santis, Maria Chiara; Cimino, James; Cappello, Paola; Pianca, Nicola; Di Bona, Anna; Margaria, Jean Piero; Martini, Miriam; Lazzarini, Edoardo; Pirozzi, Flora; Rossi, Luca; Franco, Irene; Bornbaum, Julia; Heger, Jacqueline; Rohrbach, Susanne; Perino, Alessia; Tocchetti, Carlo G; Lima, Braulio H F; Teixeira, Mauro M; Porporato, Paolo E; Schulz, Rainer; Angelini, Annalisa; Sandri, Marco; Ameri, Pietro; Sciarretta, Sebastiano; Lima-Júnior, Roberto César P; Mongillo, Marco; Zaglia, Tania; Morello, Fulvio; Novelli, Francesco; Hirsch, Emilio; Ghigo, Alessandr