Efficient generation of functional hepatocytes from human embryonic stem cells and induced pluripotent stem cells by HNF4α transduction

Abstract

Hepatocyte-like cells from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are expected to be a useful source of cells drug discovery. Although we recently reported that hepatic commitment is promoted by transduction of SOX17 and HEX into human ESC- and iPSC-derived cells, these hepatocyte-like cells were not sufficiently mature for drug screening. To promote hepatic maturation, we utilized transduction of the hepatocyte nuclear factor 4α (HNF4α) gene, which is known as a master regulator of liver-specific gene expression. Adenovirus vector-mediated overexpression of HNF4α in hepatoblasts induced by SOX17 and HEX transduction led to upregulation of epithelial and mature hepatic markers such as cytochrome P450 (CYP) enzymes, and promoted hepatic maturation by activating the mesenchymal-to-epithelial transition (MET). Thus HNF4α might play an important role in the hepatic differentiation from human ESC-derived hepatoblasts by activating the MET. Furthermore, the hepatocyte like-cells could catalyze the toxication of several compounds. Our method would be a valuable tool for the efficient generation of functional hepatocytes derived from human ESCs and iPSCs, and the hepatocyte-like cells could be used for predicting drug toxicity.

Figure 1

Transduction of HNF4α into hepatoblasts promotes hepatic differentiation. (a–c) The human ESC (H9)-derived cells, which were cultured for 6, 9, or 12 days according to the protocol described in Figure 2a, were transduced with 3,000 vector particles (VP)/cell of Ad-HNF4α for 1.5 hours and cultured until day 20. The gene expression levels of (a) hepatocyte markers (ALB and α-1-antitrypsin), (b) cholangiocyte markers (CK7 and SOX9), and (c) pancreas markers (PDX1 and NKX2.2) were examined by real-time RT-PCR on day 0 (human ESCs (hESCs)) or day 20 of differentiation. The horizontal axis represents the days when the cells were transduced with Ad-HNF4α. On the y-axis, the level of the cells without Ad-HNF4α transduction on day 20 was taken as 1.0. All data are represented as means ± SD (n = 3). ESC, embryonic stem cell; HNF4α, hepatocyte nuclear factor 4α RT-PCR, reverse transcription-PCR.

Figure 2

Hepatic differentiation of human ESCs and iPSCs transduced with three factors. (a) The procedure for differentiation of human ESCs and iPSCs into hepatocytes via DE cells and hepatoblasts is presented schematically. The hESF-DIF medium was supplemented with 10 µg/ml human recombinant insulin, 5 µg/ml human apotransferrin, 10 µmol/l 2-mercaptoethanol, 10 µmol/l ethanolamine, 10 µmol/l sodium selenite, and 0.5 mg/ml fatty-acid-free BSA. The L15 medium was supplemented with 8.3% tryptose phosphate broth, 8.3% FBS, 10 µmol/l hydrocortisone 21-hemisuccinate, 1 µmol/l insulin, and 25 mmol/l NaHCO₃. (b) Sequential morphological changes (day 0–20) of human ESCs (H9) differentiated into hepatocytes via DE cells and hepatoblasts are shown. Red arrow shows the cells that have double nuclei. (c) The morphology of primary human hepatocytes is shown. Bar represents 50 µm. BSA, bovine serum albumin; DE, definitive endoderm; ESC, embryonic stem cell; iPSC, induced pluripotent stem cell.

Figure 3

Transduction of HNF4α promotes hepatic maturation from human ESCs and iPSCs. (a,b) The human ESCs were differentiated into hepatocytes according to the protocol described in Figure 2a. On day 20 of differentiation, the gene expression levels of (a) CYP enzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP7A1) and (b) POR were examined by real-time RT-PCR in undifferentiated human ESCs (hESCs), the hepatocyte-like cells, and primary human hepatocytes (PH, hatched bar). On the y-axis, the expression level of primary human hepatocytes, which were cultured for 48 hours after the cells were plated, was taken as 1.0. (c–e) The hepatocyte-like cells (day 20) were subjected to immunostaining with (c) anti-drug-metabolizing enzymes (CYP2D6, CYP3A4, and CYP7A1), (d) anti-hepatic surface protein (ASGR1 and c-Met), and (e) anti-ALB antibodies, and then the percentage of antigen-positive cells was examined by flow cytometry on day 20 of differentiation. All data are represented as means ± SD (n = 3). ESC, embryonic stem cell; HNF4α, hepatocyte nuclear factor 4α iPSC, induced pluripotent stem cell.

Figure 4

Transduction of the three factors enhances hepatic functions. The human ESCs were differentiated into hepatoblasts and transduced with 3,000 VP/cell of Ad-LacZ or Ad-HNF4α for 1.5 hours and cultured until day 20 of differentiation according to the protocol described in Figure 2a. The hepatic functions of the two factors plus Ad-LacZ-transduced cells (SOX17+HEX+LacZ) and the three factors-transduced cells (SOX17+HEX+HNF4α) were compared. (a) Undifferentiated human ESCs (hESCs) and the hepatocyte-like cells (day 20) were cultured with medium containing Alexa-Flour 488-labeled LDL (green) for 1 hour, and immunohistochemistry and flow cytometry analysis were performed. The percentage of LDL-positive cells was measured by flow cytometry. Nuclei were counterstained with DAPI (blue). The bar represents 100 µm. (b) Induction of CYP3A4 (left), CYP2C9 (middle), or CYP1A2 (right) by DMSO (gray bar), rifampicin (black bar), or omeprazole (black bar) in the hepatocyte-like cells (day 20) and primary human hepatocytes (PH), which were cultured for 48 hours after the cells were plated. On the y-axis, the activity of primary human hepatocytes that have been cultured with medium containing DMSO was taken as 1.0. (c) The hepatocyte-like cells (day 20) (upper column) were examined for their ability to take up Indocyanin Green (ICG) and release it 6 hours thereafter (lower column). (d) Glycogen storage of the hepatocyte-like cells (day 20) was assessed by Periodic Acid-Schiff (PAS) staining. PAS staining was performed on day 20 of differentiation. Glycogen storage is indicated by pink or dark red-purple cytoplasms. The bar represents 100 µm. (e) The cell viability of undifferentiated human ESCs (black), two factors plus Ad-LacZ-tansduced cells (green), the three factors-transduced cells (blue), and primary human hepatocytes (red) was assessed by Alamar Blue assay after 48 hours exposure to different concentrations of four test compounds (troglitazone, acetaminophen, cyclophosphamide, and carbamazepine). The cell viability is expressed as a percentage of cells treated with solvent only treat: 0.1% DMSO except for carbamazepine: 0.5% DMSO. All data are represented as means ± SD (n = 3). ESC, embryonic stem cell; DMSO, dimethyl sulfoxide; LDL, low-density lipoprotein.

Figure 5

HNF4α promotes hepatic differentiation by activating MET. Human ESCs were differentiated into hepatoblasts according to the protocol described in Figure 2a, and then transduced with 3,000 VP/cell of Ad-LacZ or Ad-HNF4α for 1.5 hours, and finally cultured until day 12 of differentiation. (a) The hepatoblasts, two factors plus Ad-LacZ-transduced cells (SOX17+HEX+LacZ) (day 12), and the three factors-transduced cells (SOX17+HEX+HNF4α) (day 12) were subjected to immunostaining with anti-N-cadherin, ALB, or CK7 antibodies. The percentage of antigen-positive cells was measured by flow cytometry. (b) The cells were subjected to immunostaining with anti-N-cadherin (green), E-cadherin (green), or HNF4α (red) antibodies on day 9 or day 12 of differentiation. Nuclei were counterstained with DAPI (blue). The bar represents 50 µm. Similar results were obtained in two independent experiments. (c) The cell cycle was examined on day 9 or day 12 of differentiation. The cells were stained with Pyronin Y (y-axis) and Hoechst 33342 (x-axis) and then analyzed by flow cytometry. The growth fraction of cells is the population of actively dividing cells (G1/S/G2/M). (d) The expression levels of AFP, PROX1, α-1-antitrypsin, ALB, CK7, SOX9, N-cadherin, Snail1, Ceacam1, E-cadherin, p15, and p21 were examined by real-time RT-PCR on day 9 or day 12 of differentiation. The expression level of hepatoblasts (day 9) was taken as 1.0. All data are represented as means ± SD (n = 3). (e) The model of efficient hepatic differentiation from human ESCs and iPSCs in this study is summarized. The human ESCs and iPSCs differentiate into hepatocytes via definitive endoderm and hepatoblasts. At each stage, the differentiation is promoted by stage-specific transduction of appropriate functional genes. In the last stage of hepatic differentiation, HNF4α transduction provokes hepatic maturation by activating MET. ESC, embryonic stem cell; HNF4α, hepatocyte nuclear factor 4α iPSC, induced pluripotent stem cell; MET, mesenchymal-to-epithelial transition; RT-PCR, reverse transcription-PCR; VP, vector particle.