Nonviral delivery of siRNA into mesenchymal stem cells by a combination of ultrasound and microbubbles

Cell therapy is a promising therapeutic strategy for regenerative medicine. However, its current efficacy is insufficient, because of the short lifetime and low engraftment of transplanted cells. Transplantation of genetically modified stem cells has been reported to improve the efficacy of cell therapy. The aim of this study was to elucidate the feasibility of a combination of ultrasound and microbubbles (US-MB) for delivery of small interfering RNA (siRNA) into mesenchymal stem cells (MSC). Although cell damage was observed after US-MB treatment, the transfection efficiency determined using fluorescent-labeled siRNA was significantly increased after US-MB. Furthermore, the intracellular delivery of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) siRNA by US-MB resulted in significant knockdown of PTEN mRNA expression and activation of Akt, a mediator of a survival signaling pathway. Our results indicate that US-MB could serve as a nonviral delivery method of siRNA into MSC. The transplantation of genetically modified MSC by US-MB could be a useful strategy for regenerative medicine in the future.