Intramuscular Injection of Angiogenic Gene with Bubble Liposomes Followed by Ultrasound Exposure to Improve Angiogenesis

Ultrasound (US) in combination with microbubbles has recently engendered much attention as a safe method of gene delivery. Previously, we have developed polyethyleneglycol (PEG)‐modified liposomes entrapping echo‐contrast gas. We have called the liposomes “Bubble liposomes” (BLs). In this study, to assess the feasibility and the effectiveness of BLs for angiogenic gene delivery in clinical use, we tried to deliver bFGF (an angiogenic factor) expressing plasmid DNA into a mouse hindlimb ischemia model by the combination of BLs and US exposure. After femoral artery ligation, the hindlimb of ischemic mice were treated with BLs and US‐mediated intramuscular gene transfer of bFGF expressing plasmid DNA. After the treatment, blood flow was determined over 2 weeks using laser doppler blood flow meter. As a result, the blood flow in the treated groups with BLs and US‐mediated the gene transfer was quickly measured, and compared to other treatment groups (non‐treated, bFGF alone, or $bFGF+US$⁠). Furthermore, the number of CD31 positive cells was higher in the treatment groups with BLs and US‐mediated the gene transfer than in other treatment groups. These results suggest that intramuscular injection of bFGF as an angiogenic gene with Bubble liposomes followed by ultrasound exposure improved angiogenesis in the ischemic muscle. Thus, gene transfer into the ischemic muscle by the combination of BLs and US exposure is an effective means of angiogenic gene therapy.