Peptide-modified PAMAM-based bone-targeting RNA delivery system

Abstract

Abstract Background Osteoporosis, among other bone diseases, has become a prevalent cause of decreased quality of life in older and postmenopausal women. Traditional anti-osteoporotic therapies, though widely prescribed, are limited by a lack of cell- or tissue-specific targeting ability and effectiveness without side effects. Gene therapy is rapidly replacing traditional therapeutics, primarily because of its specific targeting ability and efficiency. Among viral- and non-viral-based gene therapies, the latter is often preferred over the former due to lower cytotoxicity, immunogenicity, and ease of modification with different molecules to improve efficiency and extend gene expression. We designed and synthesized a multifunctional bone-targeting ribonucleic acid (RNA) delivery system based on polyamidoamine (PAMAM). PAMAM was modified with the serine-aspartate-serine-serine-aspartate (SDSSD) peptide to deliver antagomir 138-5p to osteoblasts (MC3T3-E1 cell line) in vitro and in vivo using the ovariectomized (OVX) mouse model. Results The results showed that this system was less cytotoxic than polyethylenimine (PEI) and could bind to RNA favorably while maintaining gene delivery ability in vitro. In vivo data showed that the distal tibia and femur of the mice in the PAMAM-SDSSD (PS) + RNA group had improved bone mineral density (BMD), bone mineral content (BMC), and bone volume compared to those in the PS + Negative Control (NC) or OVX groups. Moreover, the femurs of the PS + RNA group mice demonstrated a higher breaking point, stress, stiffness, and elasticity than those of the PS + NC or OVX mice, suggesting improved femur strength in the OVX mice treated with RNA delivered through SDSSD-modified PAMAM. Conclusion This study shows that SDSSD modification of PAMAM not only improves gene delivery capacity but also enhances the cell targeting efficiency of nanoparticles towards osteoblasts. The successful delivery of antagomir 138-5p to osteoblasts demonstrates cell-specificity and gene delivery to alleviate osteoporotic symptoms.