To evaluate the feasibility of radiofrequency-enhanced vascular gene transduction and gene expression by using a magnetic resonance imaging-heating guidewire as an intravascular heating vehicle during magnetic resonance imaging-guided therapy.
Gene therapy presents great potential for the treatment of artherosclerotic cardiovascular disease. A magnetic resonance imaging-guidewire was designed to fulfill three functions simultaneously: to serve as a receiver antenna for generating high-spatial-resolution magnetic resonance images of vessel walls, a conventional guidewire for guiding endovascular interventions (such as balloon angioplasty and vascular gene transfer) and a potential intravascular heating source for local heating in targeted vessel segments.
The investigation included in vitro evaluation of the use of radiofrequency energy to enhance gene transduction and gene expression in vascular smooth muscle cells, as well as in vivo validation in pig arteries.
For in vitro experiments, cells were seeded in each of four chambers of a cell culture plate and a green fluorescent protein gene-bearing lentivirus was added. One of the chamber was heated at approximately 41°C for 15 minutes by using an magnetic resonance imaging-heating guidewire.
For the in vivo experiments, a lentivirus vector bearing the therapeutic vascular endothelial growth factor 165 gene was transferred by using a gene delivery balloon catheter in 18 femoral-iliac arteries (nine artery pairs) in pigs (with and without atherosclerosis). During gene infusion, one artery in each pig was heated to approximately 41°C with radiofrequency energy transferred via the intravascular magnetic resonance imaging-heating guidewire, while the contralateral artery was not heated (control condition).
The MR imaging-heating guidewire was configured in such a way that simultaneous MR imaging and RF heating was possible with the same MR imaging-heating guide wire.
|Exposure duration||continuous for 15 min|
|Additional info||In vitro experiments|
|Chamber||Cell culture plate with four chambers in which smooth muscle cells were cultured.|
|Setup||The MR imaging-heating guidewire was attached to the bottom of chamber 4 with the hot spot of the guidewire located at the center of the chamber bottom.|
|Exposure duration||approximately 20 min|
|Additional info||In vivo experiments|
|Setup||A lentivirus vector bearing a therapeutic gene was transferred by using a gene delivery balloon catheter in 18 femoral-iliac arteries in domestic pigs and Yucatan pigs with atherosclerosis. During the gene infusion, one femoral-iliac artery in each pig was heated by RF exposure. The contralateral artery was not heated and served as control.|
|Additional info||Infusion was given for continuously for 8.5 at a flow rate of 10 mL/h or intermittently at a flow rate of 21 mL/h for 8 min (4 increments of 2 mins each with 2 min interval between them).|
In vitro experiment: Confocal microscopy revealed green fluorescent protein expression in the heated chamber that was 293% the level of expression in chamber 1 (non-heated).
In vivo experiment: Data of Western blot analysis showed vascular endothelial growth factor 165 gene expression for normal arteries in the radiofrequency-heated group that was 300% the level of expression in the non-heated group, and, for atherosclerotic arteries in the radiofrequency-heated group, 986% the level in the non-heated group.
Simultaneous monitoring and enhancement of vascular gene delivery and gene expression is feasible with the magnetic resonance imaging-heating guidewire.