Innovative Strategy for 3D Transfection of Primary Human Stem Cells with BMP-2 Expressing Plasmid DNA: A Clinically Translatable Strategy for Ex Vivo Gene Therapy

Ex vivo gene therapy offers enormous potential for cell-based therapies, however, cumbersome in vitro cell culture conditions have limited its use in clinical practice. We have optimized an innovative strategy for the transient transfection of bone morphogenetic protein-2 (BMP-2) expressing plasmids in suspended human stem cells within 5-min that enables efficient loading of the transfected cells into a 3D hydrogel system. Such a short incubation time for lipid-based DNA nanoparticles (lipoplexes) reduces cytotoxicity and at the same time reduces the processing time for cells to be transplanted. The encapsulated human mesenchymal stromal/stem cells (hMSCs) transfected with BMP-2 plasmid demonstrated high expression of an osteogenic transcription factor, namely RUNX2, but not the chondrogenic factor (SOX9), within the first three days. This activation was also reflected in the 7-day and 21-day experiment, which clearly indicated the induction of osteogenesis but not chondrogenesis. We believe our transient transfection method demonstrated in primary MSCs can be adapted for other therapeutic genes for different cell-based therapeutic applications.