BACKGROUND: The deficiency of liver regeneration needs to be addressed in the fields of liver surgery, split liver transplantation and living donor liver transplantation. Researches of micro RNAs would broaden our understandings on the mechanisms of various diseases. Our previous research confirmed that mi R-26 a regulated liver regeneration in mice; however, the relationship between mi R-26 a and its target, directly or indirectly, remains unclear. Therefore, the present study further investigated the mechanism of mi R-26 a in regulating mouse hepatocyte proliferation.METHODS: An established mouse liver cell line, Nctc-1469, was transfected with Ad5-mi R-26a-EGFP, Ad5-anti-mi R-26 aEGFP or Ad5-EGFP vector. Cell proliferation was assessed by MTS, cell apoptosis and cell cycle by flow cytometry, and gene expression by Western blotting and quantitative real-time PCR. Dual-luciferase reporter assays were used to test targets of mi R-26 a.RESULTS: Compared with the Ad5-EGFP group, Ad5-antimi R-26a-EGFP down-regulated mi R-26 a and increased proliferation of hepatocytes, with more cells entering the G1 phase of cell cycle(82.70%±1.45% vs 75.80%±3.92%), and decreased apoptosis(5.50%±0.35% vs 6.73%±0.42%). CCND2 and CCNE2 were the direct targeted genes of mi R-26 a. mi R-26 a downregulation up-regulated CCND2 and CCNE2 expressions and down-regulated p53 expression in Nctc-1469 cells. On the contrary, mi R-26 a over-expression showed the opposite results.CONCLUSIONS: mi R-26 a regulated mouse hepatocyte proliferation by directly targeting the 3’ untranslated regions of cyclin D2/cyclin E2; mi R-26 a also regulated p53-mediated apoptosis. Our data suggested that mi R-26 a may be a promising regulator in liver regeneration. BACKGROUND: The deficiency of liver regeneration needs to be addressed in the fields of liver surgery, split liver transplantation and living donor liver transplantation. Researches of micro RNAs would broaden our understandings on the mechanisms of various diseases. However, the relationship between mi R-26 a and its target, directly or indirectly, remains unclear. Thus, the present study further investigating the mechanism of mi R-26 a in regulating mouse hepatocyte proliferation. METHODS: An established mouse liver cell line, Nctc-1469, was transfected with Ad5-mi R-26a-EGFP, Ad5-anti-mi R-26 aEGFP or Ad5-EGFP vector. Cell proliferation was assessed by MTS, cell cycle by flow cytometry, and gene expression by Western blotting and quantitative real-time PCR. Dual-luciferase reporter assays were used to test targets of mi R-26 a.RESULTS: Compared with the Ad5-EGFP group, Ad5-anti mi R-26a-EGFP down-regulated mi R-26 a and increased proliferation of hepatocytes with more cells entering the G1 phase of cell cycle (82.70% ± 1.45% vs 75.80% ± 3.92% ± 0.35% vs. 6.73% ± 0.42%). CCND2 and CCNE2 were the direct targeted genes of mi R-26 a. Mi R-26 a downregulation up-regulated CCND2 and CCNE2 expressions and down-regulated p53 expression in Nctc-1469 cells . On the contrary, mi R-26 a over-expression showed the opposite results. CONCLUSIONS: mi R-26 a regulated mouse hepatocyte proliferation by directly targeting the 3 ’untranslated regions of cyclin D2 / cyclin E2; mi R-26 a also regulated p53-mediated apoptosis. Our data suggested that mi R-26 a may be a promising experiment in liver regeneration.