Background/Aims: Genetic modification of mesenchymal stem cells (MSCs) is an essential requirement for their use as a delivery vehicle. To achieve higher transfection efficiency and better reproducibility than previously synthesized chitosan (100 kDa)-polyethylenimine (PEI; 1200 Da), we synthesized a low molecular weight PEI (1200 Da)-grafted chitosan (50 kDa) (CP). Methods: Safety of CP/DNA or PEI (25 kDa)/DNA was evaluated by an MTT assay using A549 cells or MSCs and a zebrafish embryo model. Effects of CP/DNA on the characteristics of MSCs were evaluated using flow cytometry. Additionally, a pGL3 plasmid was used to investigate the transfection efficiency of PEI (25 kDa), chitosan (100 kDa)-PEI (1200 Da), and CP with different N/P mass ratios on A549 cells and MSCs. Furthermore, CP/pGL3 was used to investigate the effect of serum on transfection, and intracellular transport was assessed by observing the intracellular location of DNA using laser scanning confocal microscopy. In addition, the effect of endocytosis on transfection efficiency was evaluated using A549 cells pre-treated with different inhibitors. Investigations related to analysis of transfection efficiency were all performed using the BCA protein assay to standardize the data. Furthermore, TGF-β1-and CXCR4-expressing plasmids were applied to evaluate the gene transfer efficiency of CP, including its effects on the osteogenic differentiation and migratory ability of MSCs. Results: The safety evaluation demonstrated that CP/DNA had significantly lower toxicity than PEI (25 kDa)/DNA. Additionally, DNA entered MSCs transfected by CP without changing their properties, while the examination of intracellular transport demonstrated that CP/pGL3 was internalized rapidly into MSCs. Furthermore, studies of the internalization mechanism showed that CP/pGL3 complexes entered the cells through caveolae-mediated endocytosis, thereby suggesting that the CP coating helped DNA enter A549 cells without the requirement for receptors. Compared to PEI (25 kDa), the interference of serum on transfection was reduced significantly with the use of CP in both A549 cells and MSCs. To evaluate the effects of gene delivery using the constructed CP complex and the possibility of obtaining gene-engineered MSCs, TGF-β1- and CXCR4-expressing plasmids were successfully delivered into MSCs, confirming their ability to induce osteogenesis and change the migratory ability of MSCs, respectively. Conclusion: These results demonstrated that CP could be used to deliver genes into MSCs and could potentially be used in gene therapy based on MSCs.
