Shinichiro Ogawa

Stage-specific signaling through TGFβ family members and WNT regulates patterning and pancreatic specification of human pluripotent stem cells.

The generation of insulin-producing β-cells from human pluripotent stem cells is dependent on efficient endoderm induction and appropriate patterning and specification of this germ layer to a pancreatic fate. In this study, we elucidated the temporal requirements for TGFβ family members and canonical WNT signaling at these developmental stages and show that the duration of nodal/activin A signaling plays a pivotal role in establishing an appropriate definitive endoderm population for specification to the pancreatic lineage. WNT signaling was found to induce a posterior endoderm fate and at optimal concentrations enhanced the development of pancreatic lineage cells. Inhibition of the BMP signaling pathway at specific stages was essential for the generation of insulin-expressing cells and the extent of BMP inhibition required varied widely among the cell lines tested. Optimal stage-specific manipulation of these pathways resulted in a striking 250-fold increase in the levels of insulin expression and yielded populations containing up to 25% C-peptide+ cells.

Biodegradable scaffold with built-in vasculature for organ-on-a-chip engineering and direct surgical anastomosis

We report the fabrication of a scaffold (hereafter referred to as AngioChip) that supports the assembly of parenchymal cells on a mechanically tunable matrix surrounding a perfusable, branched, three-dimensional microchannel network coated with endothelial cells. The design of AngioChip decouples the material choices for the engineered vessel network and for cell seeding in the parenchyma, enabling extensive remodelling while maintaining an open-vessel lumen. The incorporation of nanopores and micro-holes in the vessel walls enhances permeability, and permits intercellular crosstalk and extravasation of monocytes and endothelial cells on biomolecular stimulation. We also show that vascularized hepatic tissues and cardiac tissues engineered by using AngioChips process clinically relevant drugs delivered through the vasculature, and that millimeter-thick cardiac tissues can be engineered in a scalable manner. Moreover, we demonstrate that AngioChip cardiac tissues implanted via direct surgical anastomosis to the femoral vessels of rat hindlimbs establish immediate blood perfusion.

Predictive factors for intrahepatic cholangiocarcinoma recurrence in the liver following surgery

BackgroundWe performed hepatectomy without lymph node (LN) dissection for intrahepatic cholangiocarcinoma (ICC) limited to the peripheral region of the liver, and hepatectomy with extrahepatic bile duct resection and regional LN dissection for any types of ICC extending to the hepatic hilum. Surgical outcomes were evaluated to elucidate the prognostic factors that influence patient survival with respect to intrahepatic recurrence.MethodsForty-one patients underwent resection of ICC with no macroscopic evidence of residual cancer.ResultsSignificant risk factors for poorer survival included preoperative jaundice (P = 0.0115), serum CA19-9 levels >37 U/ml (P = 0.0089), tumor diameter >4.5 cm (P = 0.017), ICC extending to the hepatic hilum (P = 0.0065), mass-forming with periductal-infiltrating type (P = 0.003), poorly differentiated adenocarcinoma, portal vein involvement (P = 0.0785), LN metastasis at initial hepatectomy (P < 0.0001), and positive surgical margin (P = 0.023). Intrahepatic recurrence, which was the predominant manner of recurrence, was detected in 20 patients (74.1%). Patients with intrahepatic recurrence had a significantly high incidence of high serum CA19-9 levels (>37 U/ml; P = 0.0006), preoperative jaundice (P = 0.0262), ICC extended to the hepatic hilum (P = 0.0349), large tumors (>4.5 cm; P = 0.0351), portal vein involvement (P = 0.0423), and LN metastasis at initial hepatectomy (P = 0.009) compared with disease-free patients. The multiple logistic regression analysis revealed that preoperative CA19-9 elevation and obstructive jaundice influenced intrahepatic recurrence of ICC.ConclusionsAlthough LN metastasis is a significant prognostic factor, the most obvious recurrence pattern after surgery was intrahepatic recurrence, which could be predicted preoperatively by a combination of elevated serum CA19-9 levels and manifestation of obstructive jaundice.

Three-dimensional culture and cAMP signaling promote the maturation of human pluripotent stem cell-derived hepatocytes

Human pluripotent stem cells (hPSCs) represent a novel source of hepatocytes for drug metabolism studies and cell-based therapy for the treatment of liver diseases. These applications are, however, dependent on the ability to generate mature metabolically functional cells from the hPSCs. Reproducible and efficient generation of such cells has been challenging to date, owing to the fact that the regulatory pathways that control hepatocyte maturation are poorly understood. Here, we show that the combination of three-dimensional cell aggregation and cAMP signaling enhance the maturation of hPSC-derived hepatoblasts to a hepatocyte-like population that displays expression profiles and metabolic enzyme levels comparable to those of primary human hepatocytes. Importantly, we also demonstrate that generation of the hepatoblast population capable of responding to cAMP is dependent on appropriate activin/nodal signaling in the definitive endoderm at early stages of differentiation. Together, these findings provide new insights into the pathways that regulate maturation of hPSC-derived hepatocytes and in doing so provide a simple and reproducible approach for generating metabolically functional cell populations.

Directed differentiation of cholangiocytes from human pluripotent stem cells

Although bile duct disorders are well-recognized causes of liver disease, the molecular and cellular events leading to biliary dysfunction are poorly understood. To enable modeling and drug discovery for biliary disease, we describe a protocol that achieves efficient differentiation of biliary epithelial cells (cholangiocytes) from human pluripotent stem cells (hPSCs) through delivery of developmentally relevant cues, including NOTCH signaling. Using three-dimensional culture, the protocol yields cystic and/or ductal structures that express mature biliary markers, including apical sodium-dependent bile acid transporter, secretin receptor, cilia and cystic fibrosis transmembrane conductance regulator (CFTR). We demonstrate that hPSC-derived cholangiocytes possess epithelial functions, including rhodamine efflux and CFTR-mediated fluid secretion. Furthermore, we show that functionally impaired hPSC-derived cholangiocytes from cystic fibrosis patients are rescued by CFTR correctors. These findings demonstrate that mature cholangiocytes can be differentiated from hPSCs and used for studies of biliary development and disease.

Crucial Roles of Mesodermal Cell Lineages in a Murine Embryonic Stem Cell–Derived In Vitro Liver Organogenesis System

Recent studies in the field of regenerative medicine have exploited the pluripotency of embryonic stem (ES) cells to generate a variety of cell lineages. However, the target has always been only a single lineage, which was isolated from other differentiated cell populations. In the present study, we selected sublines with a high capability for differentiation to contracting cardiomyocytes and also produced germ‐line chimeric mice from a parent ES line. We also succeed in establishing embryoid bodies prepared from the ES cells that differentiated into not only hepatocytes but also at least two mesodermal lineages: cardiomyocytes that supported liver development and endothelial cells corresponding to sinusoids. This allowed the development of an in vitro system using murine ES cells that approximated the events of liver development in vivo. The expression of albumin was significantly higher in cardiomyocytes that had arisen in differentiated ES cells than in those that had not. Our in vitro system for liver organogenesis consists of a blood/sinusoid vascular‐like network and hepatocyte layers and shows higher levels of hepatic function, such as albumin production and ammonia degradation, than hepatic cell lines and primary cultures of murine adult hepatocytes. This innovative system will lead to the development of second‐generation regenerative medicine techniques using ES cells and is expected to be useful for the development of bioartificial liver systems and drug‐metabolism assays.

Characterization of cytochrome P450 expression in murine embryonic stem cell-derived hepatic tissue system

An in vitro system for liver organogenesis from murine embryonic stem (ES) cells has been recently established. This system is expected to be applied to the development of a new drug metabolism assay system that uses ES cells as a substitute for animal experiments. The objective of this study was to elucidate the drug metabolism profiles of the murine ES cell-derived hepatic tissue system compared with those of primary cultures of murine adult and fetal hepatocytes. The expression of the genes of the cytochrome P450 (P450) family, such as Cyp2a5, Cyp2b10, Cyp2c29, Cyp2d9, Cyp3a11, and Cyp7a1, was observed in the murine ES cell-derived hepatic tissue system at 16 days and 18 days after plating (A16 and A18). To investigate the activities of these P450 family enzymes in the murine ES cell-derived hepatic tissue system at A16 and A18, testosterone metabolism in this system was analyzed. Testosterone was hydroxylated to 6β-hydroxytestosterone (6β-OHT), 16α-OHT, 2α-OHT, and 2β-OHT in this system, and was not hydroxylated to 15α-OHT, 7α-OHT, and 16β-OHT. This metabolism profile was similar to that of fetal hepatocytes and different from that of adult hepatocytes. Furthermore, pretreatment with phenobarbital resulted in a 2.5- and 2.6-fold increase in the production of 6β-OHT and 16β-OHT. Thus, evidence for drug metabolic activities in relation to P450s has been demonstrated in this system. These results in this system would be a stepping stone of the research on the development and differentiation to adult liver.

Potentials of regenerative medicine for liver disease

Liver transplantation is still the only effective treatment for end-stage liver disease. However, because of the serious worldwide shortage of donated organs, an alternative cellular therapy would be desirable. Animal studies and preclinical trials have indicated that hepatocyte transplantation can serve as an alternative to liver transplantation. Unfortunately, however, the harvesting of hepatocytes is associated with the same problem as organ transplantation, i.e., a lack of a suitable cell source. Therefore, current stem cell technology, which is attempting to establish an unlimited supply of hepatocytes, would facilitate the clinical application of hepatocyte transplantation. This review summarizes current knowledge of embryonic and adult stem cell differentiation into hepatocytes and discusses how liver stem cells could be applied clinically in the future.

In vitro reprogramming of adult hepatocytes into insulin-producing cells without viral vectors.

The pancreas and the liver share the same endodermal origin. We have been studying whether mature hepatocytes can be induced to differentiate into pancreatic beta-cells by in vitro delivery of transcriptional factors using a non-viral approach. Here we showed that nucleofection allowed suitable transfection of primary hepatocytes employing various non-viral methods. We introduced either pancreatic and duodenal homeobox 1 (Pdx1) or neurogenin 3 (Ngn3), or both, into the mature cells using nucleofection. Co-expression of pdx1 and ngn3 using a bicistronic vector activated the transcription of various islet-related genes, and the transfected hepatocytes acquired the ability to synthesize and secrete insulin. Our results suggest that simultaneous expression of Pdx1 and Ngn3 is an excellent inducer of liver-to-pancreas reprogramming, and that reprogramming will occur even in mature somatic cells without the need for viral vectors. These findings are of considerable significance for further therapeutic development for various intractable diseases including diabetes.

New markers for tracking endoderm induction and hepatocyte differentiation from human pluripotent stem cells

The efficient generation of hepatocytes from human pluripotent stem cells (hPSCs) requires the induction of a proper endoderm population, broadly characterized by the expression of the cell surface marker CXCR4. Strategies to identify and isolate endoderm subpopulations predisposed to the liver fate do not exist. In this study, we generated mouse monoclonal antibodies against human embryonic stem cell-derived definitive endoderm with the goal of identifying cell surface markers that can be used to track the development of this germ layer and its specification to a hepatic fate. Through this approach, we identified two endoderm-specific antibodies, HDE1 and HDE2, which stain different stages of endoderm development and distinct derivative cell types. HDE1 marks a definitive endoderm population with high hepatic potential, whereas staining of HDE2 tracks with developing hepatocyte progenitors and hepatocytes. When used in combination, the staining patterns of these antibodies enable one to optimize endoderm induction and hepatic specification from any hPSC line. Highlighted article: Two new endoderm-specific cell surface antibodies, HDE1 and HDE2, identify and isolate liver-fated endoderm subpopulations with high specificity in differentiating human embryonic stem cells.