As diethylnitrosamine (DEN) effect on cell proliferation, DNA damage and stem cell marker(s) expression have been largely unknown in mouse normal hepatocytes (AML-12 cells) cultured over a short-term period, this study was conducted to examine the cell proliferation, Ataxia telangiectasia mutated (ATM) and epithelial cell adhesion molecule (EpCAM) and Neighbor of Punc E 11 (Nope) expression in AML-12 cells treated with DEN for 24 and 48 h. Cells were treated with DEN (25-800 μg/mL) and cell phenotype was determined, and the MTT assay was used to quantify the proliferation of cells treated with DEN. Expression and distribution of ATM in AML-12 cells were determined by indirect immunofluorescence microscopy. And Western blot analysis of EpCAM and Nope was performed. Cell viability was significantly increased in response to all doses of DEN treatment compared to control at 24 h (p<0.05 or p<0.01). However, there was no significant increase at 48 h, even though it showed increased trend. Immunofluorescence staining of ATM showed that there was an increase of ATM expression at doses of 50, 100 and 200 μg/mL of DEN treatment, showing strong nuclear staining. Furthermore, Western blot analysis showed that DEN treatment showed increased trend of EpCAM and Nope expression. Taken together, DEN treatment increased cell proliferation in AML- 12 cells, and it was associated with increased ATM expression.

Due to their anatomical, physiological and genetic similarities, pig is attractive animal model in biomedical research. In the recent stem cell research era, porcine derived stem cells also gain attention due to its use for the preclinical application of human. Mesenchymal stem cells (MSCs) have been studied by many researchers over decade, and their prospect for clinical application is recognized. Although porcine derived MSCs (pMSCs) have confirmed to be differentiated into various types of cells, such as osteocyte, chondrocyte, neuronal cell, cardiomyocyte and pancreatic β cell, few report has been studied regarding hepatocyte differentiation in vitro. The present study was therefore aimed for bone marrow MSCs derived from pig femur to differentiate into hepatocyte. The cells were confirmed as MSCs by characterizing their morphology, lineage differentiation capacity and surface phenotype. They showed spindle like morphology and adipocytic, osteoblastic, and chondrocytic differentiation potentials and displayed positive expression of mesenchymal markers CD29, CD44 and CD90 while lacked the expression of hematopoietic marker CD45. Under appropriate differentiation conditions, MSCs displayed hepatocyte-like morphology depending on duration of differentiation. The differentiated MSCs into hepatocyte expressed hepatocyte-specific genes including hepatocyte nuclear factor 4 (HNF4), albumin (ALB), alpha fetoprotein (AFP), alpha-1-anti trypsin (A1AT). They also showed hepatocyte-like function, glycogen storage which is identified by PAS staining. Taken together, it concluded that the bone marrow MSCs have the potential to differentiate into hepatocyte. Further studies are needed on additional hepatocytic functional assays, such as low density lipoprotein (LDL) uptake and urea synthesis of differentiated MSC.

There is a growing interest in the application of primary hepatocytes for treatment of liver diseases in humans and for drug development. Several studies have focused on long-term survival and di-differentiation blocking of primary hepatocytes in an in vitro culture system. Therefore, the present study also aimed to optimize an in vitro culture system using primary rat hepatocytes. Primary rat hepatocytes from 6-week-old male Crl:CD rats were isolated using a modified two-step collagenase perfusion. Healthy 3.5 × 106 primary rat hepatocytes were seeded into a 2 dimensional (2D) culture in a 25T culture flask coated with collagen type I or into a 3D culture in a 125-ml spinner flask for 7 days. Production of plasma protein (ALB and TF), apoptosis (BAX and BCL2), and CYP (CYP3A1) related genes were compared between the 2D and 3D culture systems. The 3D culture system had an advantage over the 2D system because of the relatively high expression of ALB and low expression of BAX in the 3D system. However, the level of CYP3A1 did not improve in the 3D culture with and without the presence of a dexamethasone inducer. Therefore, 3D culture has an advantage for albumin production and primary rat hepatocyte survivability, but a low expression of CYP3A1 indicated that primary rat hepatocytes require a high–density culture for stress reduction by continuous flow.

마늘 숙성 중 생성되는 S-allylmercaptocysteine의 콜레스 테롤 생합성 억제 효과에 대하여 Hepatocytes를 이용하여 조사하였다. HepG2 cells을 Dulbecco's modified Eagle's medium (DMEM)에 배양하여 S-allylmercaptocysteine의 농도를 20, 40, 60, 80 및 100 mL 씩 각각 첨가하여 cell viability를 살펴본 결과 20~40 μg/mL에서는 높았으며, 60 μg/mL 농도에서 약 50%가 유지되었다. S-allylmercaptocysteine을 5, 10, 15 및 20 μg/mL 농도로 [14C]-acetatecholesterol에서 처리하였을 경우 15 μg/mL 농도에서 cholesterol 생합성이 79%로 억제되었다. Fatty acid synthase의 활성은 0.95 nmol에서 19%의 억제효과를 나타내었으나, Glucose 6-phosphate dehydrogenase (G6PDH)의 활성에는 거의 영향을 미치지 않았다. S-allylmercaptocysteine의 3- hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase의 활성은 용량 의존형으로 감소하였다. 이상의 결과로 보아 마늘 숙성 과정에서 생성되는 주요 성분인 S-allylmercaptocysteine은 간 세포에서 cholesterol의 생합성을 억제하는데 기여하는 것으로 나타났다.

Recent advances in stem cell biology have shown that terminally differentiated somatic cells can be directly converted to the different types of somatic cells such as neurons and cardiomyocytes with defined sets of transcription factors without going through a pluripotent state. Recently, it was demonstrated that the hepatocyte-specific transcription factors, Hnf4α plus Foxa1, Foxa2 or Foxa3 could erase somatic memory and reset hepatocyte program on the differentiated somatic genome. Here, we show that Foxa3 together with Hnf4α could efficiently reprogram fibroblasts into hepatocytes. However, the direct conversion into hepatocytes is not observed with Hnf4α plus Foxa1. After two weeks of retroviral transduction of Hnf4α and Foxa3, we observed epithelial colonies emerged from starting fibroblasts and were able to establish stable hepatocyte cell lines, namely induced hepatocytes (iHep cells). The iHep cells closely resemble primary hepatocytes in a number of characteristics such as their polygonal shapes, the hepatic gene expression patterns and the presence of E-cadherin signals as determined by immunocytochemistry. In addition, iHep cells show the storage of glycogen as revealed by Periodic acid-Schiff (PAS) staining, indicating that iHep cells are functionally similar to their in vivo counterparts. Taken together, our findings suggest that the combination of hepatic transcription factors, Hnf4α with Foxa3 but not Foxa1 could induce hepatocyte fate on the differentiated somatic cells.

Mitochondria diseases have been reported to involve structural and functional defects of complex I-V. Especially, many of these diseases are known to be related to dysfunction of mitochondrial proton-translocating NADH-ubiquinone oxidoreductase (complex I). The dysfunction of mitochondria complex I is associated with neurodegenerative disorders, such as Parkinson's disease, Huntington's disease, and Leber’s hereditary optic neuropathy (LHON). Mammalian mitochondrial proton-translocating NADH-quinone oxidoreductase (complex I) is largest and consists of at least 46 different subunits. In contrast, the NDI1 gene of Saccharomyces cerevisiae is a single subunit rotenone-insensitive NADH-quinone oxidoreductase that is located on the matrix side of the inner mitochondrial membrane. The Saccharomyces cerevisiae NDI1 gene using a recombinant adeno-associated virus vector (rAAV-NDI1) was successfully expressed in AML12 mouse liver hepatocytes and the NDI1-transduced cells were able to grow in media containing rotenone. In contrast, control cells that did not receive the NDI1 gene failed to survive. The expressed Ndi1 enzyme was recognized to be localized in mitochondria by confocal immunofluorescence microscopic analyses and immunoblotting. Using digitonin-permeabilized cells, it was shown that the NADH oxidase activity of the NDI1-transduced cells was not affected by rotenone which is inhibitor of complex I, but was inhibited by antimycin A. Furthermore, these results indicate that Ndi1 can be functionally expressed in the AML12 mouse liver hepatocytes. It is conceivable that the NDI1 gene is powerful tool for gene therapy of mitochondrial diseases caused by complex I deficiency. In the future, we will attempt to functionally express the NDI1 gene in mouse embryonic stem (mES) cell.

Mitochondria diseases have been reported to involve structural and functional defects of complex I-V. Especially, many of these diseases are known to be related to dysfunction of mitochondrial proton-translocating NADH-ubiquinone oxidoreductase (complex I). The dysfunction of mitochondria complex I is associated with neurodegenerative disorders, such as Parkinson's disease, Huntington's disease, and Leber’s hereditary optic neuropathy (LHON). Mammalian mitochondrial proton-translocating NADH–quinone oxidoreductase (complex I) is largest and consists of at least 46 different subunits. In contrast, the NDI1 gene of is a single subunit rotenone-insensitive NADH-quinone oxidoreductase that is located on the matrix side of the inner mitochondrial membrane. The gene using a recombinant adeno-associated virus vector (rAAV-NDI1) was successfully expressed in AML12 mouse liver hepatocytes. The NDI1-transduced cells were able to grow in media containing rotenone. In contrast, control cells that did not receive the gene failed to survive. The expressed Ndi1 enzyme was recognized to be localized in mitochondria by confocal immunofluorescence microscopic analyses and immunoblotting. Using digitonin-permeabilized cells, it was shown that the NADH oxidase activity of the NDI1-transduced cells was not affected by rotenone which is inhibitor of complex I, but was inhibited by antimycin A. Furthermore, these results shown that Ndi1 can be functionally expressed in the AML12 mouse liver hepatocytes. It is conceivable that the gene is powerful tool for gene therapy of mitochondrial diseases caused by complex I deficiency. In the future, I will attempt to functionally express the NDI1 gene in mouse embryonic stem (mES) cell.

Hepatocytes and hepatic progenitors derived from human ES cells may be a useful source for clinical application. Therefore, identification and purification of these cell types would be following important issues. There are very few candidate surface markers that can be used to identify and purify hepatic progenitor cells. In addition, indocyanine-green can be uptaken by mature hepatocytes, but cannot be applied for fluorescence activated cell sorting (FACS) due to its long emission wavelength. In the present study, we tested EpCAM as a potential marker for magnetic-activated cell sorting (MACS) of hepatic progenitors and also modified indocyanine-green into fluorescent indomonocarbocyanine for FACS-mediated sorting of mature hepatocytes after differentiation of human ES cells. Hepatic progenitor cells were sorted by MACS after incubation with anti-human EpCAM antibodies. After the final differentiation, the differentiated cells and mouse primary hepatocytes (control group) were incubated with indomonocarbocyanine and were sorted by FACS. MACS and immunocytochemistry data showed that approximately 45% of differentiated cells were EpCAM-positive cells. EpCAM-positive cells expressed α-fetoprotein, FOXa2, HnF4a, and CK18. Differentiation efficiency into albumin-positive cells was significantly higher in EpCAM-positive cells, compared to EpCAM-negative cells. Importantly, indomonocarbocyanine successfully stained cells that expressed ALB. Furthermore, FACS analysis data showed that the purity of hepatocytes that expressed albumin was significantly increased after purification of indomonocarbocyanine-positive cells. Our data demonstrated that human ES cell-derived hepatic progenitors can be efficiently isolated by MACS using EpCAM antibody. In addition, we also showed that indomonocarbocyanine can be successfully used to identify and purify mature hepatocytes using FACS.

Highly homogeneous and functional stem cell-derived hepatocyte-like cells (HLCs) are considered a promising option in the treatment of liver disease and the development of effective in vitro toxicity screening tool. However, the purity of cells and expression and/or activity of drug metabolizing enzymes in stem cell-derived HLCs are usually too low to be useful for clinical or in vitro applications. Here, we describe a highly optimized differentiation protocol, which produces more than 90% albumin-positive HLCs with no purification process. In addition, we show that hepatic enzyme gene expressions and activities were significantly improved by generating three-dimensional (3D) spheroidal aggregate of HLCs. The 3D differentiation method increased expressions of nuclear receptors that regulate the proper expression of key hepatic enzymes. Furthermore, a significantly increased hepatic functions such as albumin and urea secretion were observed in 3D hepatic spheroids and HLCs in the spheroid exhibited morphological and ultrastructural features of normal hepatocytes. Importantly, we show that repeated exposures to xenobiotics facilitated the functional maturation of HLC, as confirmed by increased expression of genes for drug metabolizing enzymes and transcription factors. In conclusion, the 3D culture system with repeated exposures to xenobiotics may be a new strategy for enhancing hepatic maturation of stem cell-derived HLCs as a cell source for in vitro high-throughput hepatotoxicity models.

Hepatocyte-like cells (HLCs) derived from human pluripotent stem cells have received extensive attention in the development of drug screening and toxicity testing. However, it has been reported that stem cell-derived HLCs showed hepatic functions that were too limited to be of use in drug screening and toxicity testing, possibly due to the lack of sufficient intercellular communication under conventional two-dimensional (2D) culture conditions. Therefore, a 3D differentiation system may overcome the in vitro limitation of 2D culture to produce stem cell-derived hepatocytes with mature metabolic functions. In this study, the feasibility of using a silicone-based spherofilm, specifically designed to produce spherical cell clusters, to generate uniformly sized 3D hepatic spheroids from hESCs was investigated. Hepatic spheroids generated on the spherofilm showed more homogenous size and shape than those generated in conventional low-attachment suspension culture dishes. Results of immunohistochemical analysis showed that expression of the mature hepatic marker albumin (ALB) increased over time during the hepatic maturation process. Furthermore, the 3D culture system mimicked the in vivo 3D microenvironment. Laminin, which is an important component of hepatic ECM, was expressed in hepatic spheroids. The results of immunohistochemical analysis indicated that the 3D culture environment is capable of generating an in vivo-like microenvironment. In addition, quantitative PCR analysis showed that the mature hepatic marker ALB and cytochrome P450 (CYP) enzymes CYP3A4 and CYP3A7 were expressed at higher levels in 3D culture than in 2D culture. This indicates that the 3D culture system is suitable for hepatic maturation and that our size-controlled 3D culture conditions might accelerate hepatic function. These results suggest that 3D hepatic spheroids significantly enhance metabolic maturation of hepatocytes derived from hESCs

Hepatocytes derived from human embryonic stem cells (hESCs) may be a useful source for the treatment of diseased or injured liver. However, a low survival rate of grafted hepatocytes and immune rejection are still major obstacles to be overcome. We previously showed that secreted proteins (secretome) from hESC-derived hepatocytes had a potential therapeutic power in the tissue repair of injured liver without cell transplantation. The purpose of the present study was to discover key protein(s) in the secretome of hESC-derived hepatocytes using proteomic analysis and to study the tissue repair mechanism which may be operated by the secretomes. Purified indocyanine green+ hepatocytes derived from hESCs displayed multiple hepatic features, including expression of hepatic genes, production of albumin, and glycogen accumulation. The nano-LC/ESI-QTOF-MS analysis identified 365 proteins in the secretome of hESC-derived hepatocytes and the protein functional network analysis was conducted using the MetaCore TM from GeneGO. In addition, 20 tissue regeneration-related transcription factors (TFs) were extrapolated through further proteomic analysis. After intraperitoneal injection, the secretome significantly promoted the liver regeneration in a mouse model of acute liver injury. Protein functional network analysis on the secretome-induced regenerating liver confirmed 20 transcription factors (TFs) which were identified in the ICGhigh cells. The upreguation of these tissue repair-related TFs were validated by qPCR and western blotting on the regenerating liver tissues. These results demonstrate that application of the secretome analysis in combination with the protein functional network mapping would provide a reliable tool to discover new tissue-regenerating proteins as well as to expand our knowledge of the mechanisms of tissue regeneration.

본 연구는 내분비 장애물질의 검출을 위하여 간세포의 단층 형성, 생존 및 기능에 미치는 어류 혈청의 영향에 대해 검토하였다. 한국산 메기의 간세포는 자신의 혈청 및 뱀장어, 틸라피아 등 타어종의 혈청에 의해 부착 및 단층이 형성되었으나, FBS는 메기 간세포의 단층을 형성시키지 못했다. 0.5에서 3%의 어류 혈청으로 메기 간세포의 단층을 형성 시킬 수 있는데, 이것은 FBS(5~20%) 사용의 1/10 이하로 적은 양이며, 어류 혈청이 FBS를 대체할