Gene delivery to the spinal cord using MRI-guided focused ultrasound.

Abstract

Non-invasive gene delivery across the blood-spinal cord barrier (BSCB) remains a challenge for treatment of spinal cord injury or disease. Here, we demonstrate the use of magnetic resonance imaging-guided focused ultrasound (MRIgFUS) to mediate non-surgical gene delivery to the spinal cord, using self-complementary adeno-associated virus serotype 9 (scAAV9). scAAV9 encoding green fluorescent protein (GFP) was injected intravenously in rats. MRIgFUS allows for transient, targeted permeabilization of the BSCB through the interaction of FUS with systemically-injected Definity® lipid-shelled microbubbles. scAAV9-GFP was delivered at 3 dosages: 4×108, 2×109, and 7×109 vector genomes per gram (VG/g). Viral delivery at 2×109 and 7×109 VG/g leads to robust GFP expression in the targeted length and side of the spinal cord. At a dose of 2×109 VG/g, GFP expression was found in 36% of oligodendrocytes, and in 87% of neurons in FUS-treated areas. FUS applications to the spinal cord could address a long-term goal of gene therapy: delivering vectors from the circulation to diseased areas in a noninvasive manner.