title: MicroRNA-22 can reduce parathymosin expression in transdifferentiated hepatocytes.
abstract: Pancreatic acinar cells AR42J-B13 can transdifferentiate into hepatocyte-like cells permissive for efficient hepatitis B virus (HBV) replication. Here, we profiled miRNAs differentially expressed in AR42J-B13 cells before and after transdifferentiation to hepatocytes, using chip-based microarray. Significant increase of miRNA expression, including miR-21, miR-22, and miR-122a, was confirmed by stem-loop real-time PCR and Northern blot analyses. In contrast, miR-93, miR-130b, and a number of other miRNAs, were significantly reduced after transdifferentiation. To investigate the potential significance of miR-22 in hepatocytes, we generated cell lines stably expressing miR-22. By 2D-DIGE, LC-MS/MS, and Western blot analyses, we identified several potential target genes of miR-22, including parathymosin. In transdifferentiated hepatocytes, miR-22 can inhibit both mRNA and protein expression of parathymosin, probably through a direct and an indirect mechanism. We tested two computer predicted miR-22 target sites at the 3' UTR of parathymosin, by the 3' UTR reporter gene assay. Treatment with anti-miR-22 resulted in significant elevation of the reporter activity. In addition, we observed an in vivo inverse correlation between miR-22 and parathymosin mRNA in their tissue distribution in a rat model. The phenomenon that miR-22 can reduce parathymosin protein was also observed in human hepatoma cell lines Huh7 and HepG2. So far, we detected no major effect on several transdifferentiation markers when AR42J-B13 cells were transfected with miR-22, or anti-miR-22, or a parathymosin expression vector, with or without dexamethasone treatment. Therefore, miR-22 appears to be neither necessary nor sufficient for transdifferentiation. We discussed the possibility that altered expression of some other microRNAs could induce cell cycle arrest leading to transdifferentiation.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Hung-Lin
authors.initials: HL
authors.lastname: Chen
authors.forename: Jyun-Yuan
authors.initials: JY
authors.lastname: Huang
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Chen
authors.forename: Tien-Hua
authors.initials: TH
authors.lastname: Chu
authors.forename: Chiaho
authors.initials: C
authors.lastname: Shih
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D061354:Acinar Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D054338:Cell Transdifferentiation / Q000235:genetics*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D013947:Thymosin / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D057825:Two-Dimensional Difference Gel Electrophoresis
chemical_list: D020413:3' Untranslated Regions; D035683:MicroRNAs; D013947:Thymosin; D003907:Dexamethasone; C044498:parathymosin alpha