Designing a Prolonged Method of Therapeutic Delivery to Support Rehabilitation From Ototoxic Damage in a Schwann Cell Model.

Hypothesis: The ototoxicity of gentamicin and cisplatin can be evaluated with a Schwann cell model to screen for otoprotective agents that can be encapsulated into poly (lactic-co-glycolic acid) (PLGA) microparticles for drug delivery to the inner ear.

Background: Aminoglycosides and cisplatin are widely prescribed but known to cause ototoxicity. There is strong evidence that compromise to Schwann cells ensheathing inner ear afferent neurons results in inner ear dysfunction mimicking drug-induced ototoxicity. There is a need for a model for ototoxic demyelination to screen medications for protective potential and to subsequently target and tune the delivery of any promising agents.

Methods: RT4-D6P2T rat schwannoma cells were used as a Schwann cell model to assess gentamicin and cisplatin toxicity and to screen for protective agents. Cell viability was evaluated with the MTT cell proliferation assay. N -acetylcysteine (NAC) was encapsulated into a PLGA microparticle, and its elution profile was determined.

Results: The estimated 50% lethal concentration dose for gentamicin was 805.6 μM, which was 46-fold higher than that for cisplatin (17.5 μM). In several trials, cells dosed with NAC and cisplatin demonstrated a 22.6% ( p < 0.001) increase in cell viability when compared with cisplatin alone. However, this protective effect was not consistent across all trials. NAC was encapsulated into a PLGA microparticle and elution plateaued at 5 days.

Conclusion: When dosed at their respective therapeutic ranges, cisplatin is more likely than gentamicin to induce damage to the Schwann cell model. Although NAC demonstrates an uncertain role in protecting against cisplatin-induced Schwann cell cytotoxicity, this study establishes a method to screen for other otoprotective medications to encapsulate into a tunable microparticle for localized drug delivery.