Suppression of tissue inhibitor of metalloproteinase-1 by recombinant adeno-associated viruses carrying siRNAs in hepatic stellate cells

Elevated tissue inhibitor of metalloproteinase (TIMP)-1 expression contributes to excess production of extracellular matrix in liver fibrosis. However, there are few studies on sustained suppression of TIMP-1. We aimed to construct a recombinant adeno-associated virus (AAV) carrying small interfering RNAs (siRNAs) of TIMP-1 and investigate the long-term effects of RNA interference upon the TIMP-1 gene in rat hepatic stellate cells (HSCs). Five siRNA oligomers targeting rat TIMP-1 were designed and transfected into HSCs. A U6 promoter followed by the siRNA which had the strongest suppression effect was cloned into the AAV vector and packed into 293 cells to construct the recombinant AAV/siRNA-TIMP-1/neo. After infecting HSCs with this recombinant AAV, the transcription and expression levels of the TIMP-1 and matrix metalloproteinase-13 (MMP-13) genes were detected at 4 and 12 weeks. Three of the five designed siRNA oligomers had a suppressing effect on TIMP-1 expression in rat HSCs within 72 h. The transcription and expression levels of TIMP-1 were suppressed significantly (P<0.05) following recombinant AAV/siRNA1-TIMP-1/neo infection and lasted 12 weeks. TIMP-1 expression in rAAV/siRNA1-TIMP-1/neo-infected HSCs was suppressed by 60% after four weeks and 90% after twelve weeks when compared to the control recombinant AAV/neo and uninfected HSCs. Furthermore, the transcription and protein expression levels of MMP-13, the main substrate of TIMP-1, were elevated by ≈40% at twelve weeks in rAAV/siRNA-TIMP-1/neo-infected HSCs. RNA interference exerts suppressive effect on the TIMP-1 gene in cultured HSCs for a longer time when a recombinant AAV is utilized as the gene delivery vector.