Evaluation of a d-octaarginine-linked polymer for CRISPR-Cas9 ribonucleoprotein (RNP) delivery and genome editing in murine dendritic cells.

We previously reported that poly (N-vinylacetamide-co-acrylic acid) coupled with d-octaarginine (VP-R8) efficiently introduces proteins and nucleic acids into cells. Based on these results, we hypothesized that VP-R8 can introduce a complex composed of guide RNA and Cas9 (RNP complex) into cells and induce genome editing mediated by the CRISPR-Cas9 system. We tested this hypothesis using a mouse dendritic cell line and mouse primary dendritic cells. The RNP complexes formed by guide RNA consisting of CRISPR RNA (crRNA), fluorescently labeled trans-activating crRNA (tracrRNA), and GFP-fused Cas9 were introduced into a mouse dendritic cell line using VP-R8 or control transfection reagents. Cells transfected using VP-R8 exhibited higher fluorescence than those transfected with other transfection reagents, indicating that VP-R8 efficiently introduced the RNP complex into the mouse dendritic cell line. Genome editing of the target DNA was detected in cells transfected with the RNP complex using VP-R8 and dominant relative to other transfection reagents. We also observed that VP-R8 effectively delivered RNP complexes consisting of single-guide RNA and Cas9 and induced genome editing in the dendritic cell line. Additionally, VP-R8 efficiently delivered RNP complexes into mouse primary dendritic cells and induced genome editing of the functional gene without producing early inflammatory cytokines. Thus, VP-R8 shows potential as a transfection tool to generate dendritic cells with specific gene regions deleted by genome editing via the CRISPR-Cas9 system. This approach aims to elucidate the detailed molecular mechanisms of dendritic cell function for its application to vaccines.