PDGF-receptor beta-targeted adenovirus redirects gene transfer from hepatocytes to activated stellate cells

Chronic liver damage may lead to liver fibrosis. In this process, hepatic activated stellate cells are the key players. Thus, activated stellate cells are attractive targets for antifibrotic gene therapy. Recombinant adenovirus is a promising vehicle for delivering therapeutic genes to liver cells. However, this vector has considerable tropism for hepatocytes and Kupffer cells. The aim of this study is therefore to retarget the adenovirus to the activated stellate cells while reducing its affinity for hepatocytes. We constructed a fusion protein with affinity for both the adenovirus and the platelet derived growth factor-receptor beta (PDGF-Rbeta). In contrast to other cells, the PDFG-Rbeta is highly expressed on activated stellate cells. The targeting moiety, the PDGF peptide CSRNLIDC, was cloned in front of the single-chain antibody fragment (S11) directed against the adenoviral knob. This fusion protein enhanced adenoviral gene transfer in both 3T3 fibroblasts and primary isolated activated rat stellate cells by 10-60-fold. A fusion protein with a scrambled PDGF peptide (CIDNLSRC) did not accomplish this effect. Importantly, the PDGF-Rbeta-retargeted adenovirus showed a 25-fold reduced tropism for primary rat hepatocytes. Our novel approach demonstrates that therapeutic genes can be selectively directed to stellate cells. This opens new possibilities for the treatment of liver fibrosis.