Role of Endogenous Bone Marrow Stem Cells Mobilization in Repair of Damaged Inner Ear in Rats

BACKGROUND AND OBJECTIVES: The utilization of the stem cells is widely used in the last few years in different fields of medicine, either by external transplantation or endogenous mobilization, most of these studies still experimental on animals; few were tried on human as in the spinal cord injury or myocardial infarction. As regard its use in the inner ear, stem cell transplantation was examined in many previous studies, while the mobilization idea is a new method to be experimented in inner ear hair cell regeneration. The present work assessed the possibility of mobilizing endogenous bone marrow derived stem cells (SCs) in rats using granulocyte colony stimulating factor (G-CSF) to induce regeneration and repair to experimentally damaged inner ear hair cells by Amikacin injection. METHODS: The study included thirty adult Sprague Dawley male rats. Experimental induction of inner ear damage was done by repeated intratympanic injection of amikacin sulfate. Mobilization of bone marrow SCs was provoked by subcutaneous injection of GCSF. Cochlear integrity, induction of hearing loss and functional recovery of sensory hearing loss were assessed using Distortion Product Otoacoustic Emission (DPOAEs). The morphological alteration and recovery of the organ of Corti was assessed histologically using the light and scanning electron microscopes. RESULTS: After six month duration, there was improvement in 50% of the sensorineural DPOAE results. Functional recovery coincided with the repair of structural components of organ of Corti. CONCLUSIONS: SCs mobilization by G-CSF is a promising alternative method for replacement therapy in sensorineural hearing loss.

effects of electromagnetic fields on some neuroepithelial structures in the inner ear of rats

This work was dedicated to study the effects of long term exposure to time varying extremely low frequency electromagnetic fields on some neuroepithelial structures in the inner ear of rats. This work was conducted on 15 male adult albino rats, 5 rats were sham exposed and served as normal controls and 10 rats were exposed to time varying electromagnetic field of extremely low frequency [50 Hz] and 10-mT flux density for one hour daily, for 30 days. By the end of the experiment animals were anesthetized, perfused with the proper fixative then decapitated. The inner ears were reperfused and the temporal bones obtained. The specimens were put in a decalcifying agent for about 5 days. The specimens were prepared for either histological or scanning electron microscopical study. The present study revealed histological changes in all experimental specimens examined. The cochlea showed variable degrees of affection ranging from of cytoplasmic vacuolation of some supporting cells, to complete destruction of the organ of Corti. Stria vascularis showed atrophied lining cells. Spiral ganglionic cells appeared swollen with karyolitic nuclei. Vestibular neuroepithelial structures revealed milder response in the form of cytoplasmic vacuolation of both hair cells and supporting cells. From the previous results it could be concluded that long-term exposure to 10-mT extremely low frequency time varying electromagnetic field caused degenerative changes in the neuroepithelial structures of rat's inner ear