Photobiomodulation promotes adenoviral gene transduction in auditory cells

Abstract

Gene therapy is the delivery of a therapeutic gene into target cells to treat disorders by replacing disease-causing mutated genes with healthy ones. Gene therapy of the inner ear has been recently described, with applications for sensorineural hearing loss. However, gene delivery to the location of the inner ear, and thus efficacy of therapy, is challenging. Photobiomodulation (PBM) with a low-level laser has been suggested to have a therapeutic effect and has the potential to augment gene therapy. To investigate whether PBM improves the rate of adenovirus (Ad)-mediated viral delivery, we compared low-level laser therapy (LLLT) and non-LLLT HEI-OC1 cells treated with an Ad viral vector carrying green fluorescent protein (GFP). Cultured HEI-OC1 cells were divided into six groups: no treatment control, LLLT only, 1μL Ad-GFP, 3μL Ad-GFP, 1μL Ad-GFP + LLLT, and 3μL Ad-GFP + LLLT (LLLT: 808nm at 15mW for 15min). Cells were irradiated twice: at 2h and again at 24h. A nonparametric Mann-Whitney U test was used to statistically analyze differences between the control and treatment groups. The viral inoculations used in this study did not change the amount of viable HEI-OC1 cells (N = 4-8). The 1μL Ad-GFP + LLLT and 3μL Ad-GFP + LLLT groups showed an increased density of GFP-positive cells compared to 1μL and 3μL Ad-GFP cells (N = 5-8, 1μL: p = 0.0159; 3μL: p = 0.0168,). The quantitative analysis of the epifluorescence of the 1μL Ad-GFP + LLLT, and 3μL Ad-GFP + LLLT groups revealed increased GFP expression/cell compared to 1μL and 3μL Ad-GFP cells (N = 6-15, 1μL: p = 0.0082; 3μL: p = 0.0012). The RT-qPCR results were consistent (N = 4-5, p = 0.0159). These findings suggest that PBM may enhance the gene delivery of Ad-mediated viral transduction, and the combination of the two may be a promising tool for gene therapy for sensorineural hearing loss.