![]() Currently, novel approaches such as stem cell therapy, gene therapy, delivering small interfering RNA (siRNA) and microRNA (miRNA) molecules to the inner ear have been emerged to restore the abnormal hearing function ( Figure 1). However, some external devices, including hearing aids and cochlear implants are available for improving auditory dysfunctions. No major treatments are available for SNHL. Frequent exposure to loud noises, intake of ototoxic medications, viral infections, tumors, presbycusis (age-related hearing loss), heredity and malformation of the inner ear are the major causes of SNHL. ![]() ![]() Sensorineural hearing loss occurs when there is damage in the inner ear hair cells or insufficient function of hair cells and auditory neurons or impaired function of auditory neural pathways ( 2). Conductive hearing loss is the problem of conducting sound waves in the middle ear (eardrum and auditory ossicles), which primarily caused by the earwax or fluid accumulation in the ear canal, perforated eardrum, benign tumors, severe middle and external ear trauma and chronic otitis media ( 1). Conductive hearing loss (CHL) and sensorineural hearing loss (SNHL) are the main categories of hearing loss. The major hearing problems arise due to damage or injury in the middle ear and inner ear. Each compartment has its specific role in the hearing process. It is composed of three compartments outer, middle and inner ear. This review summarizes the potential application of mesenchymal stem cells in hearing restoration and combining stem cell and molecular therapeutic strategies can also be used in the recovery of cochlear function.Įar is the sensitive organ that senses soundwaves from the external environment and transmits them to the inner ear through external auditory meatus. Transplanted MSCs in the inner ear can recruit homing factors at the damaged sites to induce transdifferentiation into inner hair cells and ganglion neurons or regeneration of sensory hair cells, thus enhancing the cochlear function. Moreover, mesenchymal stem cells (MSCs) from different sources (bone marrow, umbilical cord, adipose tissue and placenta) could be used in inner ear therapy. Stem cell migration, survival and differentiation to supporting cells, cochlear hair cells and spiral ganglion neurons are the important foundation in understanding stem cell therapy. The current discoveries in gene therapy may provide a deeper understanding in essential genes for the inner ear regeneration. Cochlear implants and hearing aids are the temporary solutions for people suffering from severe hearing loss. Since mammalian cochlear hair cells do not regenerate naturally, some therapeutic interventions may be required to replace the damaged or lost cells. Damage to these cells can be caused by long-term exposure of excessive noise, ototoxic drugs (aminoglycosides), ear tumors, infections, heredity and aging. In the inner ear, sensory hair cells and ganglion neuronal cells are the essential supporters for hearing mechanism. In the auditory system, three components outer ear, middle ear and inner ear are essential for the hearing mechanism. Hearing loss is one of the major worldwide health problems that seriously affects human social and cognitive development.
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