A composition and method for replacement and regeneration of hair cells of the inner ear is provided. The composition comprises an active agent in an amount effective to decrease Hes1 gene expression in a tissue of the inner ear. The active agent can be short interfering RNA (siRNA) molecules encapsulated in a biodegradable nanoparticle. The method involves administering a solution to the inner ear where the solution contains an active agent in an amount effective to decrease Hes1 gene expression.
