Cell Therapy for Inner Ear Diseases

Degeneration of inner ear cells, especially sensory hair cells and associated neurons, results in hearing impairment and balance disorders. These disabilities are incurable because loss of hair cells and associated neurons is currently irreversible. Protection or regeneration of hair cells and associated neurons is an important area of research for developing an effective treatment for inner ear diseases. Cell therapy is a rapidly growing area of research and has potential applications in the treatment of inner ear disorders. The first attempts to examine the feasibility of cell therapy in the treatment of inner ear disorders have been performed using neural stem cells (NSCs). Grafted NSCs can survive in the inner ear and differentiate into neural, glial and/or hair cell-phenotypes, making NSC transplantation for the restoration of inner ear cells a potentially viable treatment. Further studies have suggested embryonic stem cells (ESCs), dorsal ganglion cells and cell lines derived from fetal inner ear cells could be used to restore damaged inner ear cells. Cell transplantation has also been suggested as a strategy for drug delivery into the inner ear, and the ability of NSC-derived cells to produce neurotrophins in the inner ear has been demonstrated. Results from studies using autologous bone marrow stromal cells (MSCs) indicate a high survival and migration potential suggesting that MSCs can be used as a drug delivery vehicle to the inner ear. These cell transplantation findings provide a sound foundation for the development of therapies to treat inner ear disorders.