Adeno-Associated Mediated Transduction of Sensory Epithelia Within the Guinea Pig Cochlea

Rova, Cherokee R. L., M.S., Autumn 2006 Pharmaceutical Sciences Adeno-associated virus mediated transduction of sensory epithelia within the guinea pig cochlea Chairperson: Dr. David J. Poulsen, PhD. Hearing loss is the most common disability of the senses and affects 250 million people worldwide. This condition is often caused by the degeneration of the sensory cells, called hair cells, found within the cochlea. Hair cell damage can result from factors such as disease, ototoxic insult, excessive noise and age. Because treatments for hearing loss are limited, scientists are looking to the use of transgene expression as a means of regenerating hair cells from nearby support cells. One possible means of transgene delivery is adeno-associated virus (AAV). AAV has been shown to be an effective transducer of both hair cells and support cells in mouse cochlear explants. Furthermore, the CAG promoter (also called CMV-beta-actin promoter) was shown to drive gene expression specifically in hair cells while the glial fibrillary acidic protein (GFAP) promoter drove expression in the non-sensory support cells. This in vivo study was designed to determine if these results might be recapitulated in the guinea pig model and was conducted in three separate phases. In Study 1, guinea pigs were inoculated with either AAV1-CAG-hrGFP or AAV2-GFAP-eGFP, the two viruses found most effective in the murine explants. Study 2 is a comparison of AAV serotypes 1, 2 and the mosaic 1/2 containing CAG and GFAP constructs with the green fluorescent protein (GFP) reporter gene. And, Study 3 examines the use of AAV1/2 with each of three promoters, CAG, GFAP and the excitatory amino acid transporter 1 promoter (EAAT1) in conjunction with GFP. Whole mount and paraffin samples from these studies illustrate the effectiveness of AAV in transducing the sensory epithelium of guinea pig cochleae. In particular, the CAG promoter was shown to drive gene expression primarily in the inner hair cells. And, gene expression appears to be enhanced by transduction using the mosaic serotype when compared to either serotype alone. GFAP drove gene expression specifically within the support cells of the organ of Corti, while EAAT1 treated animals presented with GFP strictly in the spiral ligament and limbus. Cell-type-specific gene expression is an extremely attractive quality in the development of effective gene therapy treatments for the inner ear