Author + information
- Received March 1, 2012
- Revision received May 1, 2012
- Accepted May 3, 2012
- Published online December 1, 2012.
- Aris Xie, BS⁎,
- Todd Belcik, RDCS⁎,
- Yue Qi, MD⁎,
- Terry K. Morgan, MD, PhD†,
- Shivam A. Champaneri, MD‡,
- Sarah Taylor, PhD‡,
- Brian P. Davidson, MD⁎,
- Yan Zhao, MS⁎,
- Alexander L. Klibanov, PhD‡,
- Michael A. Kuliszewski, BS§,
- Howard Leong-Poi, MD§,
- Azzdine Ammi, PhD⁎ and
- Jonathan R. Lindner, MD⁎,⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. Jonathan R. Lindner, Cardiovascular Division, UHN-62, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239
Objectives Ultrasound-mediated gene delivery can be amplified by acoustic disruption of microbubble carriers that undergo cavitation. We hypothesized that endothelial targeting of microbubbles bearing cDNA is feasible and, through optimizing proximity to the vessel wall, increases the efficacy of gene transfection.
Background Contrast ultrasound-mediated gene delivery is a promising approach for site-specific gene therapy, although there are concerns with the reproducibility of this technique and the safety when using high-power ultrasound.
Methods Cationic lipid-shelled decafluorobutane microbubbles bearing a targeting moiety were prepared and compared with nontargeted microbubbles. Microbubble targeting efficiency to endothelial adhesion molecules (P-selectin or intercellular adhesion molecule [ICAM]-1) was tested using in vitro flow chamber studies, intravital microscopy of tumor necrosis factor-alpha (TNF-α)–stimulated murine cremaster muscle, and targeted contrast ultrasound imaging of P-selectin in a model of murine limb ischemia. Ultrasound-mediated transfection of luciferase reporter plasmid charge coupled to microbubbles in the post-ischemic hindlimb muscle was assessed by in vivo optical imaging.
Results Charge coupling of cDNA to the microbubble surface was not influenced by the presence of targeting ligand, and did not alter the cavitation properties of cationic microbubbles. In flow chamber studies, surface conjugation of cDNA did not affect attachment of targeted microbubbles at microvascular shear stresses (0.6 and 1.5 dyne/cm2). Attachment in vivo was also not affected by cDNA according to intravital microscopy observations of venular adhesion of ICAM-1–targeted microbubbles and by ultrasound molecular imaging of P-selectin–targeted microbubbles in the post-ischemic hindlimb in mice. Transfection at the site of high acoustic pressures (1.0 and 1.8 MPa) was similar for control and P-selectin–targeted microbubbles but was associated with vascular rupture and hemorrhage. At 0.6 MPa, there were no adverse bioeffects, and transfection was 5-fold greater with P-selectin–targeted microbubbles.
Conclusions We conclude that ultrasound-mediated transfection at safe acoustic pressures can be markedly augmented by endothelial juxtaposition.
Dr. Davidson is supported by a post-doctoral fellowship grant (T32-HL094294) from the National Institutes of Health (NIH). Dr. Leong-Poi is supported by the Clinician Scientist Award from the Heart and Stroke Foundation of Ontario. Dr. Lindner is supported by grants R01-HL-078610, R01-DK-063508, R01-HL111969, and RC1-HL-100659 from the NIH. Dr. Klibanov is a cofounder and minority stockholder of Targeson, through which his laboratory receives an NIH subcontract, and he has received research funding from Philips Research North America. Dr. Lindner has received a grant from GE Medical Imaging. All other authors have stated that they have no relationships relevant to the contents of this paper to disclose.
- Received March 1, 2012.
- Revision received May 1, 2012.
- Accepted May 3, 2012.
- American College of Cardiology Foundation