Interstitial cells of the heart are remarkably resistant to AAV9-transduction. To overcome this limitation, we have employed a novel methodology for AAV9 vector-retargeting with a combination of polyamidoamine dendrimers (PAMAM) and cell type specific peptides and promoter specificity.

In a proof-of-concept study, we have demonstrated that endothelial cells of cardiac microvasculature can be transduced with modified vectors in different animal models. We identified an endothelial-affine peptide by bio-panning a phage display library, which then we linked to PEGylated PAMAM dendrimers, which were used to coat AAV9 vectors with Endoglin promoter-driven transgenes. After assessing transduction efficacy in reporter animals, we used the modified AAVs to deliver functionally relevant transgenes: an adhesion molecule (S1FG), where expression in cremaster endothelial cells increased leukocyte adhesion; an anti-inflammatory peptide (Anxa1), where its expression reduced long term leukocyte recruitment in carotid artery; and sgRNA targeting the vasodilatory enzyme eNOS, where Cas9 mediated knockout of eNOS caused significant increase of blood pressure. Moreover, using peptides targeting pericytes and fibroblasts and suitable promoters, we were able to obtain in vivo target cell type transduction. Also, substituting the affinity peptide with a myocyte targeting one yielded increased transduction rates of cardiomyocytes.

Here, we demonstrate that retargeted AAV9s are an efficient and modular tool for transducing cardiac interstitial cell types. Accordingly, achieving gene transfer in this previously inaccessible set of cells will broaden the toolkit of cardiovascular community to better understand the intricacies of cardiovascular system, as well as eventually have tangible results in the clinic.