Development of a Novel Nonviral Gene Silencing System That Is Effective Both in Vitro and in Vivo by Using a Star-Shaped Block Copolymer (Star Vector)

Gene-repaired iPS cells as novel approach for patient with osteogenesis imperfecta

Introduction: The benefits of patient's specific cell/gene therapy have been reported in relation to numerous genetic related disorders including osteogenesis imperfecta (OI). In osteogenesis imperfecta particularly also a drug therapy based on the administration of bisphosphonates partially helped to ease the symptoms. Methods: In this controlled trial, fibroblasts derived from patient diagnosed with OI type II have been successfully reprogrammed into induced Pluripotent Stem cells (iPSCs) using Yamanaka factors. Those cells were subjected to repair mutations found in the COL1A1 gene using homologous recombination (HR) approach facilitated with star polymer (STAR) as a carrier of the genetic material. Results: Delivery of the correct linear DNA fragment to the osteogenesis imperfecta patient's cells resulted in the repair of the DNA mutation with an 84% success rate. IPSCs showed 87% viability after STAR treatment and 82% with its polyplex. Discussion: The use of novel polymer Poly[N,N-Dimethylaminoethyl Methacrylate-co-Hydroxyl-Bearing Oligo(Ethylene Glycol) Methacrylate] Arms (P(DMAEMA-co-OEGMA-OH) with star-like structure has been shown as an efficient tool for nucleic acids delivery into cells (Funded by National Science Centre, Contract No. UMO-2020/37/N/NZ2/01125).

Hyperbranched polymeric "star vectors" for effective DNA or siRNA delivery

Although gene therapy offers an attractive strategy for treating inherited disorders, current techniques using viral and nonviral delivery systems have not yielded many successful results in clinical trials. Viral vectors such as retroviruses, lentiviruses, and adenoviruses deliver genes efficiently; however, the possibility of negative outcomes from viral transformation cannot be completely ruled out. In contrast, various types of nonviral vectors are attracting considerable attention because they are easier to handle and induce weak immune responses. Cationic polymers, such as polyethylenimine (PEI) and poly(N,N-dimethylaminopropyl acrylamide) (PDMAPAAm), can generate nanoparticles through the formation of polyion complexes, "polyplexes" with DNA. These nonviral systems offer many advantages over viral systems. The primary obstacle to implementing these cationic polymers in an effective gene therapy remains their comparatively inefficient gene transfection in vivo. We describe four strategies for the development of hyperbranched star vectors (SVs) for enhancing DNA or siRNA delivery. The molecular design was performed by living radical polymerization in which the chain length can be controlled by photoirradiation and solution conditions, including concentrations of the monomer or iniferter (a molecule that serves as a combination of initiator, transfer agent, and terminator). The branch composition is controlled by the types of monomers that are added stepwise. In our first strategy, we prepared a series of only cationic PDMAPAAm-based SVs with no branches or 3, 4, or 6 branching numbers. These SVs could form polyion complexes (polyplexes) by mixing with DNA only in aqueous solution. The relative gene expression activity of the delivered DNA increased according to the degree of branching. In addition, increasing the molecular weight of SVs and narrowing their polydispersity index (PDI) improved their activity. For targeting DNA delivery to the specific cells, we modified the SV with ligands. Interestingly, the SV could adsorb the RGD peptide, making gene transfer possible in endothelial cells which are usually refractory to such treatments. The peptide was added to the polyplex solution without covalent derivatization to the SV. The introduction of additional branching by cross-linking using iniferter-induced coupling reactions further improved gene transfection activity. After block copolymerization of PDMAPAAm-based SVs with a nonionic monomer (DMAAm), the blocked SVs (BSVs) produced polyplexes with DNA that had excellent colloidal stability for 1 month, leading to efficient in vitro and in vivo gene delivery. Moreover, BSVs served as carriers for siRNA delivery. BSVs enhanced siRNA-mediated gene silencing in mouse liver and lung. As an alternative approach, we developed a novel gene transfection method in which the polyplexes were kept in contact with their deposition surface by thermoresponsive blocking of the SV. This strategy was more effective than reverse transfection and the conventional transfection methods in solution.

Bioreducible poly (β-amino esters)/shRNA complex nanoparticles for efficient RNA delivery

RNA interference (RNAi) mediating gene silencing is a promising approach in the area of gene therapy, but it still is a major challenge to find new non-viral vectors with high transfection efficiency and low toxicity until today. In this work, three novel bioreducible poly (β-amine esters) (PAEs) with different amino monomers in the main chain were designed and synthesized by Michael addition polymerization. All PAEs could condense shRNA into complex nanoparticles with particle size (60-200nm) and positive surface charges (>+10mV). The PAEs/shRNA complex nanoparticles (PAENs) were stable under the extracellular physiological condition, while it would degrade in the reductive environment due to the cleavage of the disulfide bonds in the PAEs main chain. PAENs could achieve efficient cellular uptake and EGFP silencing in HEK-293 cells and U-87 MG cells with low cytotoxicity. The high accumulation of PAENs in tumor and high silencing efficiency of intra-tumor EGFP expression occurred when PAENs were intravenously injected into BALB/c mice bearing U-87 MG-GFP tumor. The relationship between the polymer structure and RNAi efficiency and cytotoxicity showed that the density of nitrogen atoms in PAEs backbone and the existence of disulfide bonds demonstrated the remarkable influence on in vitro and in vivo gene silencing efficiency and cytotoxicity. These experimental results suggested that the PAENs could be a promising non-viral vector for efficient RNA delivery.