Assessment of in Vitro and in Vivo Transfection Efficiency of the Biodegradable Polymer Chitosan in the Inner Ear

Background: 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 theirdesiredpropertiesasanalternativetotheviralvectors,non-viralvectorshavebeenextensivelyexploredforgenedelivery. One example is chitosan, a biodegradable cationic polymer. Objective: 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. Materials and Methods: Organotypic cultures of the hearing organ, the organ of Corti, were prepared from postnatal day 2 rats,andexposedtochitosancarryingplasmidDNA(pDNA)encodingforgreenfluorescentprotein(GFP)for24-48hours.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). Results: 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. Conclusion: It can be concluded that the using chitosan as a carrier for the in vivo transfection, is associated with varying and in consistent degree of transfection.