28 EPIGENETIC RELAY CONTROLS EXPRESSION OF THE MASTER FIBROGENIC AND METABOLIC REGULATOR PPARγ AND IS ESSENTIAL FOR ACTIVATION OF HEPATIC STELLATE CELLS

Abstract

primary HSC by transfection of complementary LNA sequences or miR125b mimics, respectively. For induction of experimental fibrosis, bile-duct ligation was performed. Furthermore miRNA expression level were studied in 84 liver biopsies representing different stages of fibrosis. Results: Microarray analyses revealed 42 differentially expressed miRNAs during in vitro induced myofibroblastic differentiation of primary HSC. miR-22, miR-31, miR-125b and miR-143 were more than 2-fold upregulated. miR-126 was downregulated in myofibroblastic HSC and one miRNA, not yet annotated in miRBase, was more than 3-fold reduced. Real-time PCR confirmed the expression profile shown by microarray analyses. During fibrogenesis in rat and in man, miR-143 did not alter and miR-22 and miR-125b was moderately repressed (p< 0.05). Whereas miR-125b was highly upregulated during myofibroblastic transition, its identified target gene, the promoting factor of pluripotency, Lin28, showed prominent downregulation. miR-125b effects on HSC pluripotency were suggested and targeting of the Lin28-3′UTR-sequence was proven by a miR-125b reporter construct in primary HSC. Conclusion: miRNA are suggested to be involved in myofibroblastic activation of HSC especiallly miR-125b seems to play a crucial role by regulation of the stem-cell specific factor, Lin28, which is also subject of further studies.