Recent progress in understanding the role of microRNAs in hepatic stellate cell biology and liver fibrosis pathogenesis

Small non-coding RNAs (21~22nt in length; known as microRNAs, miRNAs) regulate a broad array of biological processes by disrupting gene expression through physically degrading or inhibiting translation of target mRNA sequences. miRNA-mediated regulation of gene expression has been demonstrated in both physiologic and pathogenic processes of cellular differentiation, proliferation, and death. Recent studies of liver fibrosis have begun to implicate miRNAs in the disease development and progression, which in turn suggests a potential new perspective for preventive and therapeutic molecular strategies. In this review, we summarize the various miRNAs identified as differentially expressed under conditions of liver fibrosis and then detail the latest findings regarding their roles in activation of hepatic stellate cells (HSCs), the key early event in liver fibrosis. In addition, the latest findings regarding which signaling pathways and factors (such as cytokines, growth and apoptotic factors) these miRNAs interact with and modulate are discussed to provide a comprehensive insight into the fibrosis-related functions of miRNAs which may be manipulated to reduce, halt, or reverse the fibrotic process.