Activation of Wnt/β-catenin signalling via GSK3 inhibitors direct differentiation of human adipose stem cells into functional hepatocytes

A change in the zinc ion concentration reflects the maturation of insulin-producing cells generated from adipose-derived mesenchymal stem cells

The generation of insulin-producing cells (IPCs) from pluripotent stem cells could be a breakthrough treatment for type 1 diabetes. However, development of new techniques is needed to exclude immature cells for clinical application. Dithizone staining is used to evaluate IPCs by detecting zinc. We hypothesised that zinc ion (Zn2+) dynamics reflect the IPC maturation status. Human adipose-derived stem cells were differentiated into IPCs by our two-step protocol using two-dimensional (2D) or 3D culture. The stimulation indexes of 2D -and 3D-cultured IPCs on day 21 were 1.21 and 3.64 (P < 0.05), respectively. The 3D-cultured IPCs were stained with dithizone during culture, and its intensity calculated by ImageJ reached the peak on day 17 (P < 0.05). Blood glucose levels of streptozotocin-induced diabetic nude mice were normalised (4/4,100%) after transplantation of 96 3D-cultured IPCs. Zn2+ concentration changes in the medium of 3D cultures had a negative value in the early period and a large positive value in the latter period. This study suggests that Zn2+ dynamics based on our observations and staining of zinc transporters have critical roles in the differentiation of IPCs, and that their measurement might be useful to evaluate IPC maturation as a non-destructive method.

Design, Synthesis and in Vitro Tumor Cytotoxicity Evaluation of 3,5-Diamino-N-substituted Benzamide Derivatives as Novel GSK-3β Small Molecule Inhibitors

Glycogen synthase kinase-3 (GSK-3) plays an important regulatory role in various signaling pathways; such as PI3 K/AKT, which is closely related to the occurrence and development of tumors. At present, the most reported active GSK-3 inhibitors have the same structure: lactam ring or amide structure. To find out the GSK-3β small molecule inhibitor with novel, safe, efficient and more uncomplicated synthesis method, we analyzed in-depth reported crystal-binding patterns of GSK-3β small molecule inhibitor with GSK-3β protein, and designed and synthesized 17 non-reported 3,5-diamino-N-substituted benzamide compounds. Their structures were confirmed by ¹ H-NMR, ¹³ C-NMR, and HR-MS. The preliminary screening of tumor cytotoxicity of compounds in vitro was detected by MTT, and their structure-activity relationships were illustrated. The results have shown that 3,5-diamino-N-[3-(trifluoromethyl)phenyl]benzamide (4d) exhibited significant tumor cytotoxicity against human colon cancer cells (HCT-116) with IC₅₀ of 8.3 μm and showed commendable selectivity to GSK-3β. In addition, Compound 4d induced apoptosis to some extent and possessed modest PK properties.

CHIR-99021 regulates mitochondrial remodelling via β-catenin signalling and miRNA expression during endodermal differentiation

Mitochondrial remodelling is a central feature of stem cell differentiation. However, little is known about the regulatory mechanisms during these processes. Previously, we found that a pharmacological inhibitor of glycogen synthase kinase-3α and -3β, CHIR-99021, initiates human adipose stem cell differentiation into human definitive endodermal progenitor cells (hEPCs), which were directed to differentiate synchronously into hepatocyte-like cells after further treatment with combinations of soluble factors. In this study, we show that CHIR-99021 promotes mitochondrial biogenesis, the expression of PGC-1α (also known as PPARGC1A), TFAM and NRF1 (also known as NFE2L1), oxidative phosphorylation capacities, and the production of reactive oxygen species in hEPCs. Blocking mitochondrial dynamics using siRNA targeting DRP1 (also known as DNM1L) impaired definitive endodermal differentiation. Downregulation of β-catenin (CTNNB1) expression weakened the effect of CHIR-99021 on the induction of mitochondrial remodelling and the expression of transcription factors for mitochondrial biogenesis. Moreover, CHIR-99021 decreased the expression of miR-19b-2-5p, miR-23a-3p, miR-23c, miR-130a-3p and miR-130a-5p in hEPCs, which target transcription factors for mitochondrial biogenesis. These data demonstrate that CHIR-99021 plays a role in mitochondrial structure and function remodelling via activation of the β-catenin signalling pathway and inhibits the expression of miRNAs during definitive endodermal differentiation.This article has an associated First Person interview with the first author of the paper.

Palbociclib, a selective CDK4/6 inhibitor, restricts cell survival and epithelial-mesenchymal transition in Panc-1 and MiaPaCa-2 pancreatic cancer cells

The mortality rate of pancreatic cancer has close parallels to its incidence rate because of limited therapeutics and lack of effective prognosis. Despite various novel chemotherapeutics combinations, the 5-year survival rate is still under 5%. In the current study, we aimed to modulate the aberrantly activated PI3K/AKT pathway and epithelial-mesenchymal transition (EMT) signaling with the treatment of CDK4/6 inhibitor PD-0332991 (palbociclib) in Panc-1 and MiaPaCa-2 pancreatic cancer cells. It was found that PD-0332991 effectively reduced cell viability and proliferation dose-dependently within 24 hours. In addition, PD-0332991 induced cell cycle arrest at the G1 phase by downregulation of aberrant expression of CDK4/6 through the dephosphorylation of Rb in each cell lines. Although PD-0332991 treatment increased epithelial markers and decreased mesenchymal markers, the nuclear translocation of β-catenin was not prevented by PD-0332991 treatment, especially in MiaPaCa-2 cells. Effects of PD-0332991 on the regulation of PI3K/AKT signaling and its downstream targets such as GSK-3 were cell type-dependent. Although the activity of AKT was inhibited in both cell lines, the phosphorylation of GSK-3β at Ser9 increased only in Panc-1. In conclusion, PD-0332991 induced cell cycle arrest and reduced the cell viability of Panc-1 and MiaPaCa-2 cells. However, PD-0332991 differentially affects the regulation of the PI3K/AKT pathway and EMT process in cells due to its distinct influence on Rb and GSK-3/β-catenin signaling. Understanding the effect of PD-0332991 on the aberrantly activated signaling axis may put forward a new therapeutic strategy to reduce the cell viability and metastatic process of pancreatic cancer.

Pharmacological modulation of cell functional activity with valproic acid and erythropoietin

Introduction: Valproic acid (VA) is carboxylic acid with a branched chain, which is used as an antiepileptic drug.

Valproic acid influence on cells in vivo: VA, which is an antiepileptic drug, is also a teratogen, which causes defects of a neural tube and an axial skeleton, although the mechanisms are not yet fully clear.

Valproic acid influence on mesenchymal stem cells (MSC) in vitro: It is shown that valproic acid reduces the intracellular level of oxygen active forms.

Valproic acid effect on tumor cells: VA inhibits tumor growth through several mechanisms, including the cell cycle stop, differentiation induction and inhibition of growth of tumor vessels.

Valproic acid influence on enzymes: It affects mainly GSK-3.

Valproic acid influence on animals’ cells: It is shown that VA can significantly improve an ability to develop in vitro and improve nuclear reprogramming of embryos.

Erythropoietin (EPO): Is an hypoxia-induced hormone and a cytokine, which is necessary for normal erythropoiesis. EPO is widely used in in vitro experiments.

Conclusion: Thus, the influence of VA and EPO on cells can be used in cell technologies.

Hsa-miR-335 regulates cardiac mesoderm and progenitor cell differentiation

BACKGROUND

WNT and TGFβ signaling pathways play critical regulatory roles in cardiomyocyte fate determination and differentiation. MiRNAs are also known to regulate different biological processes and signaling pathways. Here, we intended to find candidate miRNAs that are involved in cardiac differentiation through regulation of WNT and TGFβ signaling pathways.

METHODS

Bioinformatics analysis suggested hsa-miR-335-3p and hsa-miR-335-5p as regulators of cardiac differentiation. Then, RT-qPCR, dual luciferase, TOP/FOP flash, and western blot analyses were done to confirm the hypothesis.

RESULTS

Human embryonic stem cells (hESCs) were differentiated into beating cardiomyocytes, and these miRNAs showed significant expression during the differentiation process. Gain and loss of function of miR-335-3p and miR-335-5p resulted in BRACHYURY, GATA4, and NKX2-5 (cardiac differentiation markers) expression alteration during the course of hESC cardiac differentiation. The overexpression of miR-335-3p and miR-335-5p also led to upregulation of CNX43 and TNNT2 expression, respectively. Our results suggest that this might be mediated through enhancement of WNT and TGFβ signaling pathways.

CONCLUSION

Overall, we show that miR-335-3p/5p upregulates cardiac mesoderm (BRACHYURY) and cardiac progenitor cell (GATA4 and NKX2-5) markers, which are potentially mediated through activation of WNT and TGFβ signaling pathways. Our findings suggest miR-335-3p/5p to be considered as a regulator of the cardiac differentiation process.

Emergence of the Dedifferentiated Phenotype in Hepatocyte-Derived Tumors in Mice: Roles of Oncogene-Induced Epigenetic Alterations

Hepatocellular carcinoma often reactivates the genes that are transiently expressed in fetal or neonatal livers. However, the mechanism of their activation has not been elucidated. To explore how oncogenic signaling pathways could be involved in the process, we examined the expression of fetal/neonatal genes in liver tumors induced by the introduction of myristoylated v-akt murine thymoma viral oncogene (AKT), HRas proto-oncogene, guanosine triphosphatase (HRASV12), and MYC proto-oncogene, bHLH transcription factor (Myc), in various combinations, into mouse hepatocytes in vivo. Distinct sets of fetal/neonatal genes were activated in HRAS- and HRAS/Myc-induced tumors: aldo-keto reductase family 1, member C18 (Akr1c18), glypican 3 (Gpc3), carboxypeptidase E (Cpe), adenosine triphosphate-binding cassette, subfamily D, member 2 (Abcd2), and trefoil factor 3 (Tff3) in the former; insulin-like growth factor 2 messenger RNA binding protein 3 (Igf2bp3), alpha fetoprotein (Afp), Igf2, and H19, imprinted maternally expressed transcript (H19) in the latter. Interestingly, HRAS/Myc-induced tumors comprised small cells with a high nuclear/cytoplasmic ratio and messenger RNA (mRNA) expression of delta-like noncanonical Notch ligand 1 (Dlk1), Nanog homeobox (Nanog), and sex determining region Y-box 2 (Sox2). Both HRAS- and HRAS/Myc-induced tumors showed decreased DNA methylation levels of Line1 and Igf2 differentially methylated region 1 and increased nuclear accumulation of 5-hydroxymethylcytosine, suggesting a state of global DNA hypomethylation. HRAS/Myc-induced tumors were characterized by an increase in the mRNA expression of enzymes involved in DNA methylation (DNA methyltransferase [Dnmt1, Dnmt3]) and demethylation (ten-eleven-translocation methylcytosine dioxygenase 1 [Tet1]), sharing similarities with the fetal liver. Although mouse hepatocytes could be transformed by the introduction of HRAS/Myc in vitro, they did not express fetal/neonatal genes and sustained global DNA methylation, suggesting that the epigenetic alterations were influenced by the in vivo microenvironment. Immunohistochemical analyses demonstrated that human hepatocellular carcinoma cases with nuclear MYC expression were more frequently positive for AFP, IGF2, and DLK1 compared with MYC-negative tumors. Conclusion: The HRAS signaling pathway and its interactions with the Myc pathway appear to reactivate fetal/neonatal gene expression in hepatocytic tumors partly through epigenetic alterations, which are dependent on the tumor microenvironment.

A Potential Role for GSK3β in Glucose-Driven Intrauterine Catch-Up Growth in Maternal Obesity

Obesity and unhealthy nutrition are increasing and affect women of childbearing age and hence during pregnancy. Despite normal or even high birth weight, the offspring suffers from long-term metabolic risks. We hypothesized that fetal growth is disturbed during different intrauterine phases. Underlying molecular events remain elusive. Female mice were fed either a standard diet (SD) or a high-fat diet (HFD) after weaning until mating and during pregnancy. Pregnant mice were euthanized at gestational day (G)15.5 and G18.5, and fetuses and placentas were removed for analysis. HFD fetuses displayed intrauterine growth restriction (IUGR) at G15.5, which disappeared until G18.5, indicating intrauterine catch-up growth during that time period. Main placental findings indicate decreased canonical Wnt-GSK3β signaling and lower proliferation rates at G18.5, which goes along with a smaller placental transfer zone. On the other hand, glucose depots (glycogen cluster) in HFD placentas decreased more strongly between G15.5 and G18.5 compared with placentas from SD mothers, and the glucose transporter protein GLUT-1 was increased at G18.5 in the HFD group. Maternal diet-induced obesity causes an IUGR phenotype at the beginning of the third week (G15.5) in our mouse model. This phenotype is reversed by the end of the third week (G18.5) despite a smaller placental transfer zone, probably based on GSK3β-mediated increased glucose mobilization in the placenta and hence an increased glucose supply to the fetus.

Fine Tuning of Hepatocyte Differentiation from Human Embryonic Stem Cells: Growth Factor vs. Small Molecule-Based Approaches

Human embryonic stem cells (hESCs) are being utilized in diverse areas of studies such as development and disease modeling, cell replacement therapy, or drug toxicity testing because of their potential to be differentiated into any cell type in the body. The directed differentiation of hESCs into hepatocytes could provide an invaluable source of liver cells for various liver-based applications. Therefore, several protocols have been established in the past for hESC-hepatocyte differentiation based on the knowledge of signaling pathways and growth factors involved in different stages of embryonic hepatogenesis. Although successful derivation of hepatocytes has been achieved through these protocols, the efficiency is not always ideal. Herein, we have tested several combinations of published protocols, for example, growth factor vs. small molecule and different time durations of treatment for definitive endoderm (DE) induction and further hepatocyte differentiation to develop an efficient DE induction and hepatocyte differentiation in a highly reproducible manner based on the stage-specific marker expression and functional analysis.

Luteolin suppresses lipopolysaccharide‑induced cardiomyocyte hypertrophy and autophagy in vitro

Luteolin (LTL) serves essential roles in a wide variety of biological processes. Lipopolysaccharide (LPS) can lead to myocardial hypertrophy and autophagy. However, the roles of LTL on LPS-induced cardiomyocyte hypertrophy and autophagy in rat cardiomyocytes have not yet been fully elucidated. In the present study, the morphology of cultured rat cardiomyocytes was observed under an inverted microscope. Cell viability was detected by MTT assay. α-Actinin and microtubule-associated protein 1 light chain 3 (LC3) expression levels were measured by immunofluorescence assay. In addition, the expression levels of atrial natriuretic peptide/brain natriuretic peptide (ANP/BNP), LC3, and autophagy- and Wnt signaling pathway-associated genes were analyzed by reverse transcription-quantitative polymerase chain reaction or western blot assays. The results indicated that LTL increased the cell viability of cardiomyocytes treated with LPS. LTL decreased the expression of cardiac hypertrophy associated markers (ANP and BNP). LTL decreased α-actinin and LC3 expression levels in LPS-treated cardiomyocytes. It was also demonstrated that LTL suppressed the mRNA and protein expression levels of LPS-mediated autophagy and Wnt signaling pathway-associated genes. In addition, it was demonstrated that silencing of β-catenin inhibited LPS-induced cardiomyocyte hypertrophy and the formation of autophagosomes. Thus, the present study suggested that LTL protected against LPS-induced cardiomyocyte hypertrophy and autophagy in rat cardiomyocytes.

Autophagy promotes hepatic differentiation of hepatic progenitor cells by regulating the Wnt/β-catenin signaling pathway

Hepatic progenitor cells (HPCs) can be activated when the liver suffers persistent and severe damage and can differentiate into hepatocytes to maintain liver regeneration and homeostasis. However, the molecular mechanism underlying the hepatic differentiation of HPCs is unclear. Therefore, in this study, we aimed to investigate the roles of autophagy and the Wnt/β-catenin signaling pathway during hepatic differentiation of HPCs in vivo and in vitro. First, immunohistochemistry, immunofluorescence and electron microscopy showed that Atg5 and β-catenin were highly expressed in human fibrotic liver and mouse liver injury induced by feeding a 50% choline-deficient diet plus 0.15% ethionine solution in drinking water (CDE diet) for 21 days; in addition, these factors were expressed in CK19-positive HPCs. Second, Western blotting and immunofluorescence confirmed that CK19-positive HPCs incubated in differentiation medium for 7 days can differentiate into hepatocytes and that differentiated HPCs were able to take up ICG and secrete albumin and urea. Further investigation via Western blotting, immunofluorescence and electron microscopy revealed autophagy and the Wnt/β-catenin pathway to be activated during hepatic differentiation of HPCs. Next, we found that inhibiting autophagy by downregulating Atg5 gene expression impaired hepatic differentiation of HPCs and inhibited activation of the Wnt/β-catenin pathway, which was rescued by overexpression of the β-catenin gene. Moreover, downregulating β-catenin gene expression without inhibiting autophagy still impeded the differentiation of HPCs. Finally, coimmunoprecipitation demonstrated that P62 forms a complex with phosphorylated glycogen synthase kinase 3 beta (pGSK3β). Third, in mouse CDE-induced liver injury, immunohistochemistry and immunofluorescence confirmed that downregulating Atg5 gene expression inhibited autophagy, thus impeding hepatic differentiation of HPCs and inhibiting activation of the Wnt/β-catenin pathway. As observed in vitro, overexpression of β-catenin rescued this phenomenon caused by autophagy inhibition, though decreasing β-catenin levels without autophagy inhibition still impeded HPC differentiation. We also found that HPCs differentiated into hepatocytes in human fibrotic liver tissue. Collectively, these results demonstrate that autophagy promotes HPC differentiation by regulating Wnt/β-catenin signaling. Our results are the first to identify a role for autophagy in promoting the hepatic differentiation of HPCs.

Osteocytes Specific GSK3 Inhibition Affects In Vitro Osteogenic Differentiation

Osteocytes, the most important regulators of bone processes, are producers of molecules (usually proteins) that act as signals in order to communicate with nearby cells. These factors control cell division (proliferation), differentiation, and survival. Substantial evidence showed different signaling pathways activated by osteocytes and involved in osteoblast differentiation, in particular in the last decade, when the Wingless-related integration site (WNT) pathway assumed a critical large importance. WNT activation by inhibiting glycogen synthase kinase 3 (GSK-3) causes bone anabolism, making GSK3 a potential therapeutic target for bone diseases. In our study, we hypothesized an important role of the osteocyte MLO-Y4 conditioned medium in controlling the differentiation process of osteoblast cell line 2T3. We found an effect of diminished differentiation capability of 2T3 upon conditioning with medium from murine long bone osteocyte-Y4 cells (MLO-Y4) pre-treated with GSK3 inhibitor CHIR2201. The novel observations of this study provide knowledge about the inhibition of GSK3 in MLO-Y4 cells. This strategy could be used as a plausible target in osteocytes in order to regulate bone resorption mediated by a loss of osteoblasts activity through a paracrine loop.

Oncogenic Determination of a Broad Spectrum of Phenotypes of Hepatocyte-Derived Mouse Liver Tumors

Activation of the phosphoinositide 3-kinase-AKT, Yes-associated protein (YAP), and MYC pathways is involved in human liver cancers, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC). However, the nature of the interactions among these pathways has remained poorly understood. Herein, we demonstrate the coordination of these pathways during the formation of mouse liver tumors induced by hepatocyte-specific somatic integration of myristoylated AKT, mutant YAP, Myc, or their combinations. Although the introduction of YAP or Myc alone was inefficient in inducing tumors, these proteins accelerated tumorigenesis induced by AKT. The generated tumors demonstrated various histological features: low-grade HCC by AKT/Myc, CC by AKT/YAP, and high-grade HCC by AKT/Myc/YAP. CC induced by AKT/YAP was associated with activation of the Notch pathway. Interestingly, the combination of Myc and YAP generated tumors composed of hepatoblast/stem-like cells expressing mRNA for Afp, Dlk1, Nanog, and Sox2 and occasionally forming immature ducts. Finally, immunohistochemical analysis revealed that human HCC and CC were predominantly associated with phosphorylation of S6 and glycogen synthase kinase-3β, respectively, and >60% of CC cases were positive for both phosphorylated glycogen synthase kinase--3β and YAP. Our study suggests that hepatocyte-derived tumors demonstrate a wide spectrum of tumor phenotypes, including HCC, CC, and hepatoblastoma-like, through the combinatory effects of the oncogenic pathways and that the state of the phosphoinositide 3-kinase-AKT pathway is a key determinant of differentiation.