Insulin like growth factor II receptor (IGFIIR) is a transmembrane protein overexpressed in activated hepatic stellate cells (HSCs), which are the major target for the treatment of liver fibrosis. In this study, we aim to discover an IGFIIR-specific aptamer that can be potentially used as a targeting ligand for the treatment and diagnosis of liver fibrosis. Systematic evolution of ligands by exponential enrichment (SELEX) was conducted on recombinant human IGFIIR to identify IGFIIR-specific aptamers. The binding affinity and specificity of the discovered aptamers to IGFIIR and hepatic stellate cells were studied using flow cytometry and Surface Plasmon Resonance (SPR). Aptamer-20 showed the highest affinity to recombinant human IGFIIR protein with a Kd of 35.5 nM, as determined by SPR. Aptamer-20 also has a high affinity (apparent Kd 45.12 nM) to LX-2 human hepatic stellate cells. Binding of aptamer-20 to hepatic stellate cells could be inhibited by knockdown of IGFIIR using siRNA, indicating a high specificity of the aptamer. The aptamer formed a chimera with an anti-fibrotic PCBP2 siRNA and delivered the siRNA to HSC-T6 cells to trigger silencing activity. In Vivo biodistribution study of the siRNA-aptamer chimera also demonstrated a high and specific uptake in the liver of the rats with CCl4-induced liver fibrosis. These data suggest that aptamer-20 is a high-affinity ligand for antifibrotic and diagnostic agents for liver fibrosis.
Keywords: IGFIIR; PCBP2.; SELEX; aptamer; hepatic stellate cells; imaging; liver fibrosis; siRNA chimera; targeted delivery.