Int. Adv. Otol. 2010; 6(3): 307-315

Assessment of in vitro and in vivo transfection efficiency of the biodegradable polymer chitosan in the inner ear.
Amanj Saber, Cecilia Gont, Suvarna Dash-Wagh, Mette Kirkegaard, Sabina P. Strand, Mats Ulfendahl. Center for Hearing and Communication Research, and Department of Clinical Neuroscience, Karolinska Institutet, Sweden

Sensorineural hearing loss is a significant problem worldwide and a condition that is not completely cured by currently available therapy. Gene therapy of the inner ear offers an exciting alternative and it has been suggested that this therapeutic modality could be used in treatment aiming at preventing, reversing or managing cochlear disorders. Because of their desired properties as an alternative to the viral vectors, non-viral vectors have been extensively explored for gene delivery. One example is chitosan, a biodegradable cationic polymer.

The aim of this study was to evaluate the in vitro and in vivo transfection efficiency of chitosan as a non-viral gene carrier for gene delivery to cells of the inner ear.

Organotypic cultures of the hearing organ, the organ of Corti, were prepared from postnatal day 2 rats, and exposed to chitosan carrying plasmid DNA (pDNA) encoding for green fluorescent protein (GFP) for 24-48 hours. The in vivo transfection efficiency was tested at two time points, at one day or seven days after infusing chitosan/pDNA polyplexes through osmotic pumps into the cochlea of adult guinea pigs (n=41). The tissue was then processed for anti-GFP immunostaining (in vitro and in vivo) and RT-PCR (in vivo). The in vitro assessment showed prominent GPF transfection after 24-48 hours, while the in vivo GFP transfection in the inner ear was inconsistent and did not show good correlation with the in vitro transfection. It can be concluded that using chitosan as a carrier for inner ear in vivo transfection, is associated with varying and in consistent degree of transfection.