Low-frequency ultrasound increases non-viral gene transfer to the mouse lung

Abstract

The aim of the study was to assess if low-frequency ultrasound (US), in the range of 30 -35 kHz, increases non-viral gene transfer to the mouse lung. US is greatly attenuated in the lung due to large energy losses at the air/tissue interfaces. The advantages of low-frequency US, compared with high-frequency US are: (i) increased cavitation (responsible for the formation of transient pores in the cell membrane) and (ii) reduced energy losses during lung penetration. Cationic lipid GL67/plasmid DNA ( pDNA), polyethylenimine (PEI)/pDNA and naked pDNA were delivered via intranasal instillation and the animals were then exposed to US (sonoporation) at 0.07 or 0.1 MPa for 10 min. Under these conditions, US did not enhance GL67 or PEI-mediated transfection. It did, however, increase naked pDNA gene transfer by approximately 4 folds. Importantly, this was achieved in the absence of microbubbles, which are crucial for the commonly used high-frequency (1 MHz) sonoporation but may not be able to withstand nebulization in a clinically relevant setup. Lung hemorrhage was also assessed and shown to increase with US pressure in a dose-dependent manner. We have thus, established that low-frequency US can enhance lung gene transfer with naked pDNA and this enhancement is more effective than the previously reported 1 MHz US.

The rapidly evolving state of gene therapy

“…Subsequently, a number of other physical methods were developed to transfect mammalian cells ex vivo, including cationic liposome-DNA complexes, polycation-DNA complexes, electroporation, ballistic gene delivery with gold particle-DNA complexes, and several others (75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86)(87)(88). Several of these technologies have been carried forward to in vivo use, including in humans, sometimes by simple direct naked DNA injection into muscle or tumor tissue.…”

Targeting the Lung: Challenges in Gene Therapy for Cystic Fibrosis

“…Naked DNA is in theory the safest gene therapy agent but very difficult to be introduced into the target cells. Several physical methods have been developed to facilitate DNA entry into the lung of living animals, such as the use of electrical pulses (electroporation) [77], of ultrasound waves (sonoporation) [78] and of magnetic fields (magnetofection) [79] but none of them has reached the clinical use yet. On the other hand, chemical carriers have rapidly been developed and used in 6% (n=110) of gene therapy clinical trials (http:// www.wiley.com/legacy/wileychi/genmed/clinical).…”

Non-Viral Gene Therapy Vectors Carrying Genomic Constructs

“…Such microbubbles are commercially available and their stability has been shown to affect directly the efficiency of in vivo sonoporation (Alter et al, 2009). Several studies have shown in vivo d e l i v e r y o f p l a s m i d s c a rrying either reporter or therapeutic genes to different tissues including lung, heart and muscle (Xenariou et al, 2010;Alter et al, 2009;Sheyn et al, 2008) but comparative data, wherever provided, confirmed that the efficiency of sonoporation was significantly lower than that of electroporation. However, sonoporation is still being considered for clinical application in humans due to its non-invasive nature and lesser tissue damage caused compared to electroporation.…”