Preliminary Study On Hath1 Gene And DAPT Therapy Of Hearing Loss In Rats

Sensorineural hearing loss influences the human being severely. There are still no effective clinical means for curing it at present while regeneration of hair cells is the key point of treatment of sensorineural deafness. Molecular biology, molecu- lar genetics and genetic engineering have improved in recent years, which makes gene therapy a promising technology for treating inner ear disorders. Our study includes two parts as following.Part one: Evaluation of hearing loss and hair cell injury induced by co-administration of furosemide and kanamycin in rats OBJECTIVE: To investigate the ototoxicity of co-administration of furosemide and kanamycin in rats and establish a reliable model to induce a sensorineural hearing loss. METHODS: All of the experimental rats were received a single intravenous injection of furosemide and/or another single intramuscular injection of kanamycin immediately. The auditory brainstem response (ABR) threshold shift was tested 3 days, 7 days and 2 months after the infusion, respectively. The series of experimental methods including scanning electron microscopy, myosinVIIa staining and HE staining were applied to observe the characteristics of the lesion of cochlea 7 days after the infusion. RESULTS: The ABR threshold shift was presented a significant increase after a co-administration of furosemide and kanamycin at 4, 8, 16, 32kHz. Pathological examination showed an absence of outer hair cells and inner hair cells throughout the length of the cochlea. However, the injury of vestibular hair cells and supporting cells was very slight. In contrast, there was no hearing loss or hair cell injury after a single injection of furosemide or kanamycin. CONCLUSION: Co-administration of furosemide and kanamycin eliminates hair cells completely in vivo, and it could establish a reliable model for the study of sensorineural hearing loss in rats.Part Two: Preliminary Study on regeneration of hair cells after H- ath1 gene and DAPT were delivered into the cochleaOBJECTIVE: To explore the regeneration of hair cells after Hath1 and DAPT w- ere delivered into cochlea in rats. METHODS: Hath1 gene and DAPT were deliv- ered into the right cochlea of normal and deaf rats througn scala tympani. The auditory brainstem response (ABR) threshold shift was tested. The series of experimental methods including hath1 staining, phalloidin staining, myosinVIIa staining and scanning electron microscopy were applied to observe the cochlea 4 weeks after the delivery. RESULTS: The number of hair cells didn't increase in the normal rats. There was no generation of new hair cells or hearing improvement in the deaf rats. CONCLUSION: Delivery of Hath1 gene and DAPT to cochlea failed to generate new hair cells or improve hearing in mature rats. Maybe it is necessary to deliver Multiple genes for the therapy of sensorineural hearing loss.