Kazuko Takubo

Hepatic differentiation of human bone marrow–derived mesenchymal stem cells by tetracycline-regulated hepatocyte nuclear factor 3β†

Human bone marrow–derived mesenchymal stem cells (BM‐MSCs) are expected to be a potential source of cells for transplantation. Although recent reports have shown that isolated MSCs can differentiate into hepatocytes, the efficiency of differentiation is insufficient for therapeutic application. To circumvent this problem, it is necessary to understand the mechanisms of hepatic differentiation of human BM‐MSCs. Hepatocyte nuclear factor 3β (HNF3β), a forkhead/winged helix transcription factor, is essential for liver development. In the present study, we established a tetracycline (Tet)‐regulated expression system for HNF3β in UE7T‐13 BM‐MSCs. HNF3β expression significantly enhanced expression of albumin, α‐fetoprotein (AFP), tyrosine amino transferase (TAT) and epithelial cell adhesion molecule (EpCAM) genes. The differentiated cells showed hepatocyte‐specific functions including glycogen production and urea secretion. During treatment with the Tet‐on system for 8 days, over 80% of UE7T‐13 cells turned out to express albumin. Furthermore, the combination of Tet with basic fibroblast growth factor (bFGF) efficiently induced the genes such as albumin and TAT, which are associated with maturity of hepatocytes; however, it suppressed genes such as AFP and EpCAM, which are associated with immaturity of hepatocytes, suggesting that Tet‐induced HNF3β expression sensitizes BM‐MSCs to bFGF signals. Finally, the results of the present study suggest that down‐regulation of Wnt/β‐catenin signals caused by translocation of β‐catenin to cytoplasmic membrane is associated with hepatic differentiation of human BM‐MSCs. Conclusion: HNF3β expression induced efficient differentiation of UE7T‐13 human BM‐MSCs. (HEPATOLOGY 2008;48:597–606.)

Synthetic retinoid CD437 induces mitochondria-mediated apoptosis in hepatocellular carcinoma cells

Retinoids play an important role in the regulation of cell growth and death. Synthetic retinoid CD437 reportedly induces apoptosis in various cancer cell lines. However, the mechanism of inducing apoptosis in hepatocellular carcinoma (HCC) cells by this agent remains to be clarified. In this study, we investigated the signaling pathway by which CD437 induces apoptosis in HCC cell lines. Apoptosis of six human HCC cell lines was induced by treatment with CD437. Caspase-3 and -9 were activated by CD437, suggesting that the apoptosis is mediated by mitochondrial pathways. Consistent with these findings, the treatment with CD437 upregulated Bax protein, downregulated Bcl-2 protein and released cytochrome c into the cytoplasm. Moreover, rhodamine123 staining revealed mitochondrial depolarization in the cells treated with CD437. These data of the present study suggest that CD437 induces apoptosis in HCC cells via mitochondrial pathways.

Involvement of microRNAs in regulation of osteoblastic differentiation in mouse induced pluripotent stem cells.

Backgoround MicroRNAs (miRNAs), which regulate biological processes by annealing to the 3′-untranslated region (3′-UTR) of mRNAs to reduce protein synthesis, have been the subject of recent attention as a key regulatory factor in cell differentiation. The effects of some miRNAs during osteoblastic differentiation have been investigated in mesenchymal stem cells, however they still remains to be determined in pluripotent stem cells. Methodology/Principal Findings Bone morphogenic proteins (BMPs) are potent activators of osteoblastic differentiation. In the present study, we profiled miRNAs during osteoblastic differentiation of mouse induced pluripotent stem (iPS) cells by BMP-4, in which expression of important osteoblastic markers such as Rux2, osterix, osteopontin, osteocalcin, PTHR1 and RANKL were significantly increased. A miRNA array analysis revealed that six miRNAs including miR-10a, miR-10b, miR-19b, miR-9-3p, miR-124a and miR-181a were significantly downregulated. Interestingly, miR-124a and miR-181a directly target the transcription factors Dlx5 and Msx2, both of which were increased by about 80-and 30-fold, respectively. In addition, transfection of miR-124a and miR-181a into mouse osteo-progenitor MC3T3-E1 cells significantly reduced expression of Dlx5, Runx2, osteocalcin and ALP, and Msx2 and osteocalcin, respectively. Finally, transfection of the anti-miRNAs of these six miRNAs, which are predicted to target Dlx5 and Msx2, into mouse iPS cells resulted in a significant increase in several osteoblastic differentiation markers such as Rux2, Msx2 and osteopontin. Conclusions/Significance In the present study, we demonstrate that six miRNAs including miR-10a, miR-10b, miR-19b, miR-9-3p, miR-124a and miR-181a miRNAs, especially miR-124a and miR-181a, are important regulatory factors in osteoblastic differentiation of mouse iPS cells.

Retinoids ameliorate insulin resistance in a leptin-dependent manner in mice†

Transgenic mice expressing dominant‐negative retinoic acid receptor (RAR) α specifically in the liver exhibit steatohepatitis, which leads to the development of liver tumors. Although the cause of steatohepatitis in these mice is unknown, diminished hepatic expression of insulin‐like growth factor‐1 suggests that insulin resistance may be involved. In the present study, we examined the effects of retinoids on insulin resistance in mice to gain further insight into the mechanisms responsible for this condition. Dietary administration of all‐trans‐retinoic acid (ATRA) significantly improved insulin sensitivity in C57BL/6J mice, which served as a model for high‐fat, high‐fructose diet–induced nonalcoholic fatty liver disease (NAFLD). The same effect was observed in genetically insulin‐resistant KK‐Ay mice, occurring in concert with activation of leptin‐signaling pathway proteins, including signal transducer and activator of transcription 3 (STAT3) and Janus kinase 2. However, such an effect was not observed in leptin‐deficient ob/ob mice. ATRA treatment significantly up‐regulated leptin receptor (LEPR) expression in the livers of NAFLD mice. In agreement with these observations, in vitro experiments showed that in the presence of leptin, ATRA directly induced LEPR gene expression through RARα, resulting in enhancement of STAT3 and insulin‐induced insulin receptor substrate 1 phosphorylation. A selective RARα/β agonist, Am80, also enhanced hepatic LEPR expression and STAT3 phosphorylation and ameliorated insulin resistance in KK‐Ay mice. Conclusion: We discovered an unrecognized mechanism of retinoid action for the activation of hepatic leptin signaling, which resulted in enhanced insulin sensitivity in two mouse models of insulin resistance. Our data suggest that retinoids might have potential for treating NAFLD associated with insulin resistance. (HEPATOLOGY 2012)

Hepatic differentiation of human bone marrow-derived UE7T-13 cells: Effects of cytokines and CCN family gene expression.

Aim:  Bone marrow‐derived mesenchymal stem cells (MSC) are expected to be an excellent source of cells for transplantation. We aimed to study the culture conditions and involved genes to differentiate MSC into hepatocytes.

Involvement of N-acetyltransferase human in the cytotoxic activity of 5-fluorouracil.

N-acetyltransferase human (NATH) participates in a posttranslational modification of the proteins and has been reported to play a role in apoptosis. In this study, the involvement of NATH in the cytotoxic action of 5-fluorouracil (5-FU) in human squamous cell carcinoma HEp-2 cells was examined. We found that 5-FU decreased NATH expression in a dose-dependent and time-dependent manner. No change was observed after treatment with bleomycin, nedaplatin, mitomycin C, or methotrexate. Interestingly, knockdown of NATH by small interfering RNA resulted in the downregulation of thymidylate synthase mRNA expression and induced apoptosis. Conversely, NATH overexpression facilitated cell proliferation independent of the presence of 5-FU. The effect of NATH knockdown on the expression of proteins in HEp-2 cells was examined using two-dimensional gel electrophoresis and mass spectrometry. Profilin 1, CutA, ras-related nuclear protein, annexin A5, enolase 1, and elongation factor 1 alpha 1 were found to be upregulated and 14-3-3η, tublin, nuclear auto antigenic sperm protein, heat shock protein 70, and heat shock protein 90 were downregulated by knockdown of NATH. The results of this study suggest that NATH plays an important role in the cytotoxic activity of 5-FU.

A Case of Actinomycosis of the Minor Salivary Gland in the Buccal Region

Abstract We report a case of actinomycosis arising in the minor salivary gland in the buccal region. A 71-year-old male presented with a swelling in the left buccal region. The clinical diagnosis was minor salivary gland tumor in the buccal mucosa. Under local anesthesia, the lesion was excised. Histopathological examination showed basophilic amorphous masses of Actinomyces in the dilated excretory duct with squamous metaplasia. A final diagnosis of actinomycosis was made. Its portal of entry was thought to be a disruption of the mucosal barrier after trauma due to maladaptation of dentures. There was no sign of recurrence after the surgery.