Background: Bioartificial liver systems, designed to support patients with liver failure,\r\nare composed of bioreactors and functional hepatocytes. Immunological rejection of\r\nthe embedded hepatocytes by the host immune system is a serious concern that\r\ncrucially degrades the performance of the device. Induced pluripotent stem (iPS) cells\r\nare considered a desirable source for bioartificial liver systems, because patient-derived\r\niPS cells are free from immunological rejection. The purpose of this paper was to test\r\nthe feasibility of a bioartificial liver system with iPS cell-derived hepatocyte-like cells.\r\nMethods: Mouse iPS cells were differentiated into hepatocyte-like cells by a multi-step\r\ndifferentiation protocol via embryoid bodies and definitive endoderm. Differentiation of\r\niPS cells was evaluated by morphology, PCR assay, and functional assays. iPS\r\ncell-derived hepatocyte-like cells were cultured in a bioreactor module with a pore size\r\nof 0.2 �µm for 7 days. The amount of albumin secreted into the circulating medium was\r\nanalyzed by ELISA. Additionally, after a 7-day culture in a bioreactor module, cells were\r\nobserved by a scanning electron microscope.\r\nResults: At the final stage of the differentiation program, iPS cells changed their\r\nmorphology to a polygonal shape with two nucleoli and enriched cytoplasmic\r\ngranules. Transmission electron microscope analysis revealed their polygonal shape,\r\nglycogen deposition in the cytoplasm, microvilli on their surfaces, and a duct-like\r\narrangement. PCR analysis showed increased expression of albumin mRNA over the\r\ncourse of the differentiation program. Albumin and urea production was also observed.\r\niPS-Heps culture in bioreactor modules showed the accumulation of albumin in the\r\nmedium for up to 7 days. Scanning electron microscopy revealed the attachment of\r\ncell clusters to the hollow fibers of the module. These results indicated that iPS cells\r\nwere differentiated into hepatocyte-like cells after culture for 7 days in a bioreactor\r\nmodule with a pore size of 0.2 �µm.\r\nConclusion: We consider the combination of a bioreactor module with a 0.2-�µm pore\r\nmembrane and embedded hepatocytes differentiated from iPS cells to be a promising\r\noption for bioartificial liver systems. This paper provides the basic concept and\r\npreliminary data for an iPS cell-oriented bioartificial liver system.\r\nPACS code: 87. Biological and medical physics, 87.85.-d Biomedical engineering, 87.85.Lf\r\nTissue engineering, 87.85.Tu Modeling biomedical systems
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