ASGCT - Aptamer Group Poster
Targeted Delivery of siRNA to Activated Hepatic Stellate Cells Using Aptamers: A Novel Approach for Fibrotic Liver Treatment
Lal R, Ward T, Withers J, Varayathu H, Kidd D, Bunka D
A lack of effective strategies for targeted delivery of gene therapies to different cell types (beyond hepatocytes) is hindering the development of therapeutic modalities such as RNAi for many diseases. Aptamers offer the potential to selectively deliver RNAi therapies to new biomarkers and cell types.
Activated hepatic stellate cells (HSCs) are a key driver of fibrosis within the liver; thus, targeting this cell type and the fibrotic differentiation process may offer new potential treatments for liver fibrosis. Applying cell-based aptamer selection methods to human primary activated HSCs, with negative selection against hepatocytes, an aptamer was developed that selectivity binds and internalises to activated human HSCs. Targeting of the aptamer to activated HSCs is ideal for targeting the cells actively involved in fibrotic disease without affecting the remaining hepatic cell population. Further screening with alternative cell types showed the aptamer does not interact with T lymphocytes, renal tubule epithelial cells, prostate, breast, or lung epithelial cells, or other hepatic cell populations, including hepatocytes and Kupffer cells. Multiple cleavable and non-cleavable Optimer-siRNA linker types have been tested for functionality, with the greatest siRNA silencing effect seen with a cathepsin-cleavable linker. siRNA conjugation to the aptamer delivery vehicle did not interfere with aptamer binding or selectivity. Four different siRNA molecules have been conjugated to the aptamer delivery vehicle, including those targeting ColA1 and PDGFR as critical molecular mediators of fibrosis. Each of the tested aptamer-siRNA conjugates resulted in significant silencing of the respective genes in HSCs by flow cytometry and qPCR (p < 0.0001), with no observable off-target gene silencing in hepatocyte cultures, indicating that the developed aptamer is selective and can deliver diverse siRNA payloads with sufficient endosomal escape to enable effective gene silencing.
Taken together, these data demonstrate for the first time the development of a delivery vehicle selective for activated HSCs, with the potential to deliver diverse therapeutic cargo to this cell type. Advancing this delivery vehicle into the clinic with a relevant siRNA conjugate opens the potential for new treatment approaches in liver fibrosis.
