Conversion of immortal liver progenitor cells into pancreatic endocrine progenitor cells by persistent expression of Pdx-1

Antioxidative Capacity of Liver- and Adipose-Derived Mesenchymal Stem Cell-Conditioned Media and Their Applicability in Treatment of Type 2 Diabetic Rats

Type 2 diabetes mellitus (T2DM) is mainly characterized by insulin resistance and impaired insulin secretion, which cannot be reversed with existing therapeutic strategies. Using mesenchymal stem cells (MSCs), cell-based therapy has been demonstrated in displaying therapeutic effects in T2DM for their self-renewable, differentiation potential, and immunosuppressive properties and higher levels of angiogenic factors. Stem cell therapies are complicated and have a serious adverse effect including tumor formation and immunogenicity, while using mesenchymal stem cell-conditioned media (MSC-CM) significantly reduces stem cell risk, maintaining efficacy and showing significantly higher levels of growth factors, cytokines, and angiogenic factors that stimulate angiogenesis and promote fracture healing in diabetes. In the present study, we investigated the therapeutic potential of the liver and adipose MSC-CM in diabetic endothelial dysfunction compared with standard insulin therapy. Fifty adult male Sprague Dawley rats were divided equally into 5 groups as follows: control, diabetic, diabetic+insulin, diabetic+liver MSC-CM, and diabetic+adipose MSC-CM; all treatments continued for 4 weeks. Finally, we observed that liver MSC-CM therapy had the most apparent improvement in levels of blood glucose; HbA1c; AGEs; lipid panel (cholesterol, TG, LDL, HDL, and total lipids); renal function (urea, uric acid, creatinine, and total protein); liver function (AST, ALT, ALP, bilirubin, and albumin); CPK; C-peptide; HO-1; inflammatory markers including IL-6, TNF-α, and CRP; growth factors (liver and serum IGF-1); amylase; histopathological changes; pancreatic cell oxidative stress; and antioxidant markers (MDA, GSH, ROS, CAT, SOD, HO-1, and XO) toward the normal levels compared with insulin and adipose MSCs-CM. Moreover, both the liver and adipose MSC-CM relieved the hyperglycemic status by improving pancreatic islet β cell regeneration, promoting the conversion of alpha cells to beta cells, reducing insulin resistance, and protecting pancreatic tissues against oxidative stress-induced injury as well as possessing the ability to modulate immunity and angiogenesis. These results indicated that MSC-CM infusion has therapeutic effects in T2DM rats and may be a promising novel therapeutic target.

PDX1 binds and represses hepatic genes to ensure robust pancreatic commitment in differentiating human embryonic stem cells

Inactivation of the Pancreatic and Duodenal Homeobox 1 (PDX1) gene causes pancreatic agenesis, which places PDX1 high atop the regulatory network controlling development of this indispensable organ. However, little is known about the identity of PDX1 transcriptional targets. We simulated pancreatic development by differentiating human embryonic stem cells (hESCs) into early pancreatic progenitors and subjected this cell population to PDX1 chromatin immunoprecipitation sequencing (ChIP-seq). We identified more than 350 genes bound by PDX1, whose expression was upregulated on day 17 of differentiation. This group included known PDX1 targets and many genes not previously linked to pancreatic development. ChIP-seq also revealed PDX1 occupancy at hepatic genes. We hypothesized that simultaneous PDX1-driven activation of pancreatic and repression of hepatic programs underlie early divergence between pancreas and liver. In HepG2 cells and differentiating hESCs, we found that PDX1 binds and suppresses expression of endogenous liver genes. These findings rebrand PDX1 as a context-dependent transcriptional repressor and activator within the same cell type.

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Early pancreatic progenitor (ePP) cells are efficiently derived from hESCs

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High levels of the homeobox transcription factor PDX1 label ePP cells

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PDX1 binds a battery of foregut/midgut and early pancreatic genes in ePP cells

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PDX1 binds and represses hepatic genes

miRNA-302 facilitates reprogramming of human adult hepatocytes into pancreatic islets-like cells in combination with a chemical defined media

The direct conversion of one cell type to another without an intermediate pluripotent stage is required for regenerative therapies. The ventral pancreas and liver share a common developmental origin. Recent studies have shown that hepatocytes could be induced to transdifferentiate into insulin-producing cells. In this paper, we showed a new strategy to achieve the direct conversion of human hepatocytes into surrogate β cells. Hepatocytes were transfected with microRNA-302 (miR-302) mimic and Pdx1, Ngn3 and MafA expressed plasmids, followed by a chemical-defined culture system for maturation of insulin-secreting cells. Co-transfection of miR-302 mimic increased the transcription of pancreatic development-related genes (Sox17, Foxa2, and endogenous Pdx1). Furthermore, at the end of this treatment, hepatocytes became insulin expressed cells that released the hormone in response to a physiological glucose change in vitro. This work shows that miR-302 participation may facilitates the conversion of adult hepatocytes into pancreatic islets-like cells.

Adult stem cells as a renewable source of insulin-producing cells

Diabetes mellitus is a metabolic disorder resulting from an inadequate mass of insulin-producing pancreatic beta cells. The replacement or restoration of damaged beta cells would be considered the optimal therapeutic options. Islet transplantation seems to be a promising approach for replacement therapy; however, the main obstacle is the shortage of organ donors. As mature beta cells have been shown to be difficult to expand in vitro, regeneration of beta cells from embryonic or adult stem cells or pancreatic progenitor cells is an attractive method to restore the islet cell mass. So far, multiple studies using various strategies have shown direct differentiation of stem and progenitor cells toward insulin-producing cells. The important issue to be solved is how to differentiate these cells into mature functional insulin-producing cells. Further research is required to understand how endogenous beta cells differentiate and to develop methods to regenerate enough functional beta cells for clinically applicable therapies for diabetes.

Generation of functional insulin-producing cells from neonatal porcine liver-derived cells by PDX1/VP16, BETA2/NeuroD and MafA

Surrogate β-cells derived from stem cells are needed to cure type 1 diabetes, and neonatal liver cells may be an attractive alternative to stem cells for the generation of β-cells. In this study, we attempted to generate insulin-producing cells from neonatal porcine liver-derived cells using adenoviruses carrying three genes: pancreatic and duodenal homeobox factor1 (PDX1)/VP16, BETA2/NeuroD and v-maf musculo aponeurotic fibrosarcoma oncogene homolog A (MafA), which are all known to play critical roles in pancreatic development. Isolated neonatal porcine liver-derived cells were sequentially transduced with triple adenoviruses and grown in induction medium containing a high concentration of glucose, epidermal growth factors, nicotinamide and a low concentration of serum following the induction of aggregation for further maturation. We noted that the cells displayed a number of molecular characteristics of pancreatic β-cells, including expressing several transcription factors necessary for β-cell development and function. In addition, these cells synthesized and physiologically secreted insulin. Transplanting these differentiated cells into streptozotocin-induced immunodeficient diabetic mice led to the reversal of hyperglycemia, and more than 18% of the cells in the grafts expressed insulin at 6 weeks after transplantation. These data suggested that neonatal porcine liver-derived cells can be differentiated into functional insulin-producing cells under the culture conditions presented in this report and indicated that neonatal porcine liver-derived cells (NPLCs) might be useful as a potential source of cells for β-cell replacement therapy in efforts to cure type I diabetes.

Guiding Differentiation of Stem Cells in Vivo by Tetracycline-Controlled Expression of Key Transcription Factors

Transplantation of stem or progenitor cells is an attractive strategy for cell replacement therapy. However, poor long-term survival and insufficiently reproducible differentiation to functionally appropriate cells in vivo still present major obstacles for translation of this methodology to clinical applications. Numerous experimental studies have revealed that the expression of just a few transcription factors can be sufficient to drive stem cell differentiation toward a specific cell type, to transdifferentiate cells from one fate to another, or to dedifferentiate mature cells to pluripotent stem/progenitor cells (iPSCs). We thus propose here to apply the strategy of expressing the relevant key transcription factors to guide the differentiation of transplanted cells to the desired cell fate in vivo. To achieve this requires tools allowing us to control the expression of these genes in the transplant. Here, we describe drug-inducible systems that allow us to sequentially and timely activate gene expression from the outside, with a particular emphasis on the Tet system, which has been widely and successfully used in stem cells. These regulatory systems offer a tool for strictly limiting gene expression to the respective optimal stage after transplantation. This approach will direct the differentiation of the immature stem/progenitor cells in vivo to the desired cell type.

CELLPEDIA: a repository for human cell information for cell studies and differentiation analyses

CELLPEDIA is a repository database for current knowledge about human cells. It contains various types of information, such as cell morphologies, gene expression and literature references. The major role of CELLPEDIA is to provide a digital dictionary of human cells for the biomedical field, including support for the characterization of artificially generated cells in regenerative medicine. CELLPEDIA features (i) its own cell classification scheme, in which whole human cells are classified by their physical locations in addition to conventional taxonomy; and (ii) cell differentiation pathways compiled from biomedical textbooks and journal papers. Currently, human differentiated cells and stem cells are classified into 2260 and 66 cell taxonomy keys, respectively, from which 934 parent-child relationships reported in cell differentiation or transdifferentiation pathways are retrievable. As far as we know, this is the first attempt to develop a digital cell bank to function as a public resource for the accumulation of current knowledge about human cells. The CELLPEDIA homepage is freely accessible except for the data submission pages that require authentication (please send a password request to cell-info@cbrc.jp). Database URL: http://cellpedia.cbrc.jp/

NKX6.1 promotes PDX-1-induced liver to pancreatic β-cells reprogramming

Reprogramming adult mammalian cells is an attractive approach for generating cell-based therapies for degenerative diseases, such as diabetes. Adult human liver cells exhibit a high level of developmental plasticity and have been suggested as a potential source of pancreatic progenitor tissue. An instructive role for dominant pancreatic transcription factors in altering the hepatic developmental fate along the pancreatic lineage and function has been demonstrated. Here we analyze whether transcription factors expressed in mature pancreatic β-cells preferentially activate β-cell lineage differentiation in liver. NKX6.1 is a transcription factor uniquely expressed in β-cells of the adult pancreas, its potential role in reprogramming liver cells to pancreatic lineages has never been analyzed. Our results suggest that NKX6.1 activates immature pancreatic markers such as NGN-3 and ISL-1 but not pancreatic hormones gene expression in human liver cells. We hypothesized that its restricted capacity to activate a wide pancreatic repertoire in liver could be related to its incapacity to activate endogenous PDX-1 expression in liver cells. Indeed, the complementation of NKX6.1 by ectopic PDX-1 expression substantially and specifically promoted insulin expression and glucose regulated processed hormone secretion to a higher extent than that of PDX-1 alone, without increasing the reprogrammed cells. This may suggest a potential role for NKX6.1 in promoting PDX-1 reprogrammed cells maturation along the β-cell-like lineage. By contrast, NKX6.1 repressed PDX-1 induced proglucagon gene expression. The individual and concerted effects of pancreatic transcription factors in adult extra-pancreatic cells, is expected to facilitate developing regenerative medicine approaches for cell replacement therapy in diabetics.

Adult cell fate reprogramming: converting liver to pancreas

Regenerative medicine aims at producing new cells for repair or replacement of diseased and damaged tissues. Embryonic and adult stem cells have been suggested as attractive sources of cells for generating the new cells needed. The leading dogma was that adult cells in mammals, once committed to a specific lineage, become "terminally differentiated" and can no longer change their fate. However, in recent years increasing evidence has accumulated demonstrating the remarkable ability of some differentiated cells to be converted into a different cell type via a process termed developmental redirection or adult cells reprogramming. For example, abundant human cell types, such as dermal fibroblasts and adipocytes, could potentially be harvested and converted into other, medically important cell types, such as neurons, cardiomyocytes, or pancreatic beta cells. In this chapter, we describe a method of activating the pancreatic lineage and beta-cells function in adult human liver cells by ectopic expression of pancreatic transcription factors. This approach aims to generate custom-made autologous surrogate beta cells for treatment of diabetes, and possibly bypass both the shortage of cadaveric human donor tissues and the need for life-long immune-suppression.

Development of insulin-producing cells from primitive biologic precursors

PURPOSE OF REVIEW

The differentiation of pluripotent and multipotent stem cells into insulin-producing cells has the potential to create a renewable supply of replacement beta cells with tremendous utility in the treatment of diabetes. The purpose of this review is to summarize recent advancements in the field, with emphasis on the limitations of this technology as it relates to the beta cell.

RECENT FINDINGS

Multiple groups have developed successful in-vitro protocols to differentiate human embryonic stem cells and selected tissue specific stem cells into progenitors capable of insulin production and glucose-stimulated insulin secretion. The resulting cells are immature beta cell-like cells that coexpress multiple islet hormones and lack the full complement of genes necessary for normal function. Protocols that include in-vivo maturation in immune-compromised mice produce cells with a more mature phenotype.

SUMMARY

Although tremendous progress has been made in differentiating stem cells into insulin-producing cells, there is still more research needed to produce a fully functional adult beta cell.

Pdx-1 or Pdx-1-VP16 protein transduction induces beta-cell gene expression in liver-stem WB cells

Background

Pancreatic duodenal homeobox-1 (Pdx-1) or Pdx-1-VP16 gene transfer has been shown to induce in vitro rat liver-stem WB cell conversion into pancreatic endocrine precursor cells. High glucose conditions were necessary for further differentiation into functional insulin-producing cells. Pdx-1 has the ability to permeate different cell types due to an inherent protein transduction domain (PTD). In this study, we evaluated liver-to-pancreas conversion of WB cells following Pdx-1 or Pdx-1-VP16 protein transduction.

Findings

WB cells were grown in high glucose medium containing Pdx-1 or Pdx-1-VP16 recombinant proteins for two weeks. β-like cell commitment was analysed by RT-PCR of pancreatic endocrine genes. We found that WB cells in high glucose culture spontaneously express pancreatic endocrine genes (Pdx-1, Ngn3, Nkx2.2, Kir6.2). Their further differentiation into β-like cells expressing genes related to endocrine pancreas development (Ngn3, NeuroD, Pax4, Nkx2.2, Nkx6.1, Pdx-1) and β-cell function (Glut-2, Kir6.2, insulin) was achieved only in the presence of Pdx-1(-VP16) protein.

Conclusion

These results demonstrate that Pdx-1(-VP16) protein transduction is instrumental for in vitro liver-to-pancreas conversion and is an alternative to gene therapy for β-cell engineering for diabetes cell therapy.