FoxO1 inhibition promotes differentiation of human embryonic stem cells into insulin producing cells

Insulin-producing cells (IPCs) derived from human embryonic stem cells (hESCs) hold great potential for cell transplantation therapy in diabetes. Tremendous progress has been made in inducing differentiation of hESCs into IPCs in vitro, of which definitive endoderm (DE) protocol mimicking foetal pancreatic development has been widely used. However, immaturity of the obtained IPCs limits their further applications in treating diabetes. Forkhead box O1 (FoxO1) is involved in the differentiation and functional maintenance of murine pancreatic β cells, but its role in human β cell differentiation is under elucidation. Here, we showed that although FoxO1 expression level remained consistent, cytoplasmic phosphorylated FoxO1 protein level increased during IPC differentiation of hESCs induced by DE protocol. Lentiviral silencing of FoxO1 in pancreatic progenitors upregulated the levels of pancreatic islet differentiation-related genes and improved glucose-stimulated insulin secretion response in their progeny IPCs, whereas overexpression of FoxO1 showed the opposite effects. Notably, treatment with the FoxO1 inhibitor AS1842856 displayed similar effects with FoxO1 knockdown in pancreatic progenitors. These effects were closely associated with the mutually exclusive nucleocytoplasmic shuttling of FoxO1 and Pdx1 in the AS1842856-treated pancreatic progenitors. Our data demonstrated a promising effect of FoxO1 inhibition by the small molecule on gene expression profile during the differentiation, and in turn, on determining IPC maturation via modulating subcellular location of FoxO1 and Pdx1. Therefore, we identify a novel role of FoxO1 inhibition in promoting IPC differentiation of hESCs, which may provide clues for induction of mature β cells from hESCs and clinical applications in regenerative medicine.     

Insulin-Producing Cells Derived from Human Embryonic Stem Cells: Comparison of Definitive Endoderm- and Nestin-Positive Progenitor-Based Differentiation Strategies

Human embryonic stem cells (hESCs) are pluripotent and capable of undergoing multilineage differentiation into highly specialized cells including pancreatic islet cells. Thus, they represent a novel alternative source for targeted therapies and regenerative medicine for diabetes. Significant progress has been made in differentiating hESCs toward pancreatic lineages. One approach is based on the similarities of pancreatic β cell and neuroepithelial development. Nestin-positive cells are selected as pancreatic β cell precursors and further differentiated to secrete insulin. The other approach is based on our knowledge of developmental biology in which the differentiation protocol sequentially reproduces the individual steps that are known in normal β cell ontogenesis during fetal pancreatic development. In the present study, the hESC cell line PKU1.1 was induced to differentiate into insulin-producing cells (IPCs) using both protocols. The differentiation process was dynamically investigated and the similarities and differences between both strategies were explored. Our results show that IPCs can be successfully induced with both differentiation strategies. The resulting IPCs from both protocols shared many similar features with pancreatic islet cells, but not mature, functional β cells. However, these differently-derived IPC cell types displayed specific morphologies and different expression levels of pancreatic islet development-related markers. These data not only broaden our outlook on hESC differentiation into IPCs, but also extend the full potential of these processes for regenerative medicine in diabetes.     

Human bone marrow mesenchymal stem cells differentiate into insulin-producing cells upon microenvironmental manipulation in vitro

It was recently reported that pluripotent mesenchymal stem cells (MSCs) in rodent bone marrow (BM) have the capacity to generate insulin-producing cells (IPCs) in vitro. However, little is known about this capacity in human BM-MSCs. We developed a nongenetic method to induce human BM-MSCs to transdifferentiate into IPCs both phenotypically and functionally. BM-MSCs from 12 human donors were sequentially cultured in specially defined conditions. Their differentiation extent toward β-cell phenotype was evaluated systemically. Specifically, after induction human BM-MSCs formed spheroid islet-like clusters containing IPCs, which was further confirmed by dithizone (DTZ) staining and electron microscopy. These IPCs expressed multiple genes related to the development or function of pancreatic β cells (including NKX6.1, ISL-1, Beta2/Neurod, Glut2, Pax6, nestin, PDX-1, ngn3, insulin and glucagon). The coexpression of insulin and c-peptide was observed in IPCs by immunofluorescence. Moreover, they were able to release insulin in a glucose-dependent manner and ameliorate the diabetic conditions of streptozotocin (STZ)-treated nude mice. These results indicate that human BM-MSCs might be an available candidate to overcome limitations of islet transplantation.     

Generation of insulin-producing cells from gnotobiotic porcine skin-derived stem cells

A major problem in the treatment of type 1 diabetes mellitus is the limited availability of alternative sources of insulin-producing cells for islet transplantation. In this study, we investigated the effect of bone morphogenetic protein 4 (BMP-4) treatments of gnotobiotic porcine skin-derived stem cells (gSDSCs) on their reprogramming and subsequent differentiation into insulin-producing cells (IPCs). We isolated SDSCs from the ear skin of a gnotobiotic pig. During the proliferation period, the cells expressed stem-cell markers Oct-4, Sox-2, and CD90; nestin expression also increased significantly. The cells could differentiate into IPCs after treatments with activin-A, glucagon-like peptide-1 (GLP-1), and nicotinamide. After 15 days in the differentiation medium, controlled gSDSCs began expressing endocrine progenitor genes and proteins (Ngn3, Neuro-D, PDX-1, NKX2.2, NKX6.1, and insulin). The IPCs showed increased insulin synthesis after glucose stimulation. The results indicate that stem cells derived from the skin of gnotobiotic pigs can differentiate into IPCs under the appropriate conditions in vitro. Our three-stage induction protocol could be applied without genetic modification to source IPCs from stem cells in the skin of patients with diabetes for autologous transplantation.     

Improved differentiation of umbilical cord blood-derived mesenchymal stem cells into insulin-producing cells by PDX-1 mRNA transfection

Numerous studies have sought to identify diabetes mellitus treatment strategies with fewer side effects. Mesenchymal stem cell (MSC) therapy was previously considered as a promising therapy; however, it requires the cells to be trans-differentiated into cells of the pancreatic-endocrine lineage before transplantation. Previous studies have shown that PDX-1 expression can facilitate MSC differentiation into insulin-producing cells (IPCs), but the methods employed to date use viral or DNA-based tools to express PDX-1, with the associated risks of insertional mutation and immunogenicity. Thus, this study aimed to establish a new method to induce PDX-1 expression in MSCs by mRNA transfection. MSCs were isolated from human umbilical cord blood and expanded in vitro, with stemness confirmed by surface markers and multipotentiality. MSCs were transfected with PDX-1 mRNA by nucleofection and chemically induced to differentiate into IPCs (combinatorial group). This IPC differentiation was then compared with that of untransfected chemically induced cells (inducer group) and uninduced cells (control group). We found that PDX-1 mRNA transfection significantly improved the differentiation of MSCs into IPCs, with 8.3±2.5% IPCs in the combinatorial group, 3.21±2.11% in the inducer group and 0% in the control. Cells in the combinatorial group also strongly expressed several genes related to beta cells (Pdx-1, Ngn3, Nkx6.1 and insulin) and could produce C-peptide in the cytoplasm and insulin in the supernatant, which was dependent on the extracellular glucose concentration. These results indicate that PDX-1 mRNA may offer a promising approach to produce safe IPCs for clinical diabetes mellitus treatment.     

Sodium butyrate activates genes of early pancreatic development in embryonic stem cells

Embryonic stem (ES) cells can differentiate into any tissue, including pancreatic islet cell types. Protocols for the efficient generation of these cells in vitro could have therapeutic applications for type I diabetes. Here we describe a simple method for the differentiation of mouse ES cells into epithelial cells with a gene expression profile consistent with that expected of early pancreatic progenitors (PP). It is based on the addition of sodium butyrate, an agent known to induce chromatin rearrangements. Variations on the length of exposure to butyrate result in the generation of hepatocytes or PP-like cells. qRT-PCR indicates that butyrate induces mesendoderm/definitive endoderm, but not neuroectoderm differentiation. PPlike cells show a strong upregulation of Ipf1/Pdx1, p48, Isl-1 and Nkx6.1, but not Ngn3, NeuroD/ Beta2 or Pax4. PP-like cells also express the epithelial marker E-cadherin. Taken together, our observations suggest that butyrate stimulates early events of pancreatic specification, prior to the onset of endocrine differentiation. These findings are discussed in the context of the development of protocols for the in vitro differentiation of islets.     

Controlled induction of human pancreatic progenitors produces functional beta-like cells in vitro

Directed differentiation of human pluripotent stem cells into functional insulin-producing beta-like cells holds great promise for cell replacement therapy for patients suffering from diabetes. This approach also offers the unique opportunity to study otherwise inaccessible aspects of human beta cell development and function in vitro. Here, we show that current pancreatic progenitor differentiation protocols promote precocious endocrine commitment, ultimately resulting in the generation of non-functional polyhormonal cells. Omission of commonly used BMP inhibitors during pancreatic specification prevents precocious endocrine formation while treatment with retinoic acid followed by combined EGF/KGF efficiently generates both PDX1⁺ and subsequent PDX1⁺/NKX6.1⁺ pancreatic progenitor populations, respectively. Precise temporal activation of endocrine differentiation in PDX1⁺/NKX6.1⁺ progenitors produces glucose-responsive beta-like cells in vitro that exhibit key features of bona fide human beta cells, remain functional after short-term transplantation, and reduce blood glucose levels in diabetic mice. Thus, our simplified and scalable system accurately recapitulates key steps of human pancreas development and provides a fast and reproducible supply of functional human beta-like cells.     

Pancreatic islet-like clusters from periosteum-derived progenitor cells

Recent studies comparing the insulin-producing cell (IPC) differentiation capacity of mesenchymal stem cells (MSCs) derived from four different sources (bone marrow, Wharton’s jelly, adipose tissue, and the periosteum) demonstrated that IPC differentiation of periosteum-derived progenitor cells (PDPCs) progressed faster than any other MSCs within 7 days, indicating that PDPCsare most suited to IPC differentiation. Here, two different cell culture methods, adhesion and cluster culture, were assessed for their ability to support in vitro IPC differentiation. The induction of IPC differentiation was confirmed by RTqPCR analysis of insulin gene expression levels and immunofluorescence analysis of insulin protein. An enzyme-linked immunosorbent assay was used to quantify secreted insulin. PDPC-derived IPCs from cluster cultures demonstrated a significantly increased expression of insulin and an enhanced secretion of insulin of insulin protein in response to glucose compared to IPCs derived from adhesion cultures. Thus, pancreatic islet-like cluster cultures appear to provide the optimal conditions such as cluster culture for IPC differentiation of PDPCs.     

NKX2-5(eGFP/w) hESCs for isolation of human cardiac progenitors and cardiomyocytes

NKX2-5 is expressed in the heart throughout life. We targeted eGFP sequences to the NKX2-5 locus of human embryonic stem cells (hESCs); NKX2-5(eGFP/w) hESCs facilitate quantification of cardiac differentiation, purification of hESC-derived committed cardiac progenitor cells (hESC-CPCs) and cardiomyocytes (hESC-CMs) and the standardization of differentiation protocols. We used NKX2-5 eGFP(+) cells to identify VCAM1 and SIRPA as cell-surface markers expressed in cardiac lineages.     

Ku70作为RNA解旋酶调节miR-124的加工成熟及神经细胞的分化

目的 Ku70蛋白主要通过其DNA结合特性参与双链DNA断裂（DSB）的非同源端连接（NHEJ）修复,有报道称其具有RNA结合功能,本文探索Ku70是否具有RNA解旋酶活性并影响miRNA加工成熟。方法 利用RNA免疫共沉淀（RIP）测序结合生物信息学分析Ku蛋白结合的RNA;蛋白质印迹法（Western blot,WB）结合定量反转录PCR（qRT-PCR）检测Ku蛋白与miRNAs的表达关系;生物膜干涉技术（BLI）实验分析Ku蛋白与RNA的结合能力;电泳迁移率变动分析（EMSA）实验确定Ku70及Ku80的RNA解旋酶活性;形态学检测结合WB分析Ku70调节miR-124引起的神经细胞功能变化;免疫荧光结合形态学分析寨卡病毒（ZIKV）感染后Ku70及miR-124的变化与神经元分化关联。结果 研究发现,Ku70蛋白具有RNA解旋酶活性,并通过其RNA解旋酶活性影响miRNA加工成熟。Ku70缺失引起许多miRNAs上调,其中包括神经细胞特异的miR-124。在人神经前体细胞（hNPCs）和人神经母细胞瘤细胞（SH-SY5Y）中敲低Ku70可促进 miR-124的成熟,从而导致上述细胞向神经元分化。本文进一步发现,ZIKV感染影响了Ku70及miR-124的表达,导致细胞形态的分化。结论 本研究揭示了Ku70的一种新功能,即Ku70有可能参与miRNA的成熟调控和神经细胞的分化,并且可能是ZIKV病毒致小头症的原因之一。