胰腺腺泡细胞AR42J-B13能够转分化为肝细胞样的细胞,实验发现，在这种转分化的细胞中乙肝病毒(HBV)能够有效的复制。
在AR42J-B13细胞转分化为肝细胞前后，台湾国防医学院的研究人员使用芯片微阵列技术发现了miRNAs的区别性表达。
通过实时PCR以及Northern blot分析发现，miRNA（包括miR-21, miR-22及miR-122a）的表达得到了显著的提高。与此相反，miR-93和miR-130b以及许多其它的miRNAs，在转分化后明显减少。
为了研究肝细胞中miR-22的潜在作用，他们建立了能够稳定表达miR-22的细胞系。随后通过2D-DIGE, LC-MS/MS及Western blot分析，鉴定了miR-22的几种潜在的目的基因。
研究发现，在转分化的肝细胞，miR-22可能是通过一个直接的或者是间接的机制，抑制了胸腺旁腺素的mRNA及蛋白的表达。在胸腺旁腺素的3'UTR，通过3'UTR报告基因分析，他们检测了两个由电脑预测的miR-22靶点。
miR-22能够降低胸腺旁腺素蛋白的现象也被发现于人类肝癌细胞系Huh7及HepG2。到目前为止，即使AR42J-B13细胞被miR-22或anti-miR-22或胸腺旁腺素表达载体的转染，并使用或者不使用地塞米松处理，研究人员发现这些对几种转分化标记物没有明显影响。
因此，miR-22对于转分化作用好像既不是充分的也不是必须的。为此，研究人员表示，这有可能是因为改变了能够诱导细胞发生转分化的其它的microRNAs的表达。相关论文发表在4月6日的Plos One。（生物谷Deepblue编译）
doi: 10.1371/journal.pone.0034116
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MicroRNA-22 Can Reduce Parathymosin Expression in Transdifferentiated Hepatocytes
Hung-Lin Chen, Jyun-Yuan Huang, Chun-Ming Chen, Tien-Hua Chu, Chiaho Shih.
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.
