| Objective: X linked inhibitor of apoptosis protein(XIAP)can be transported into the inner ear cells with adeno-associated virus as a vector with different approaches.This study is about the best approach in different animals and the protection of over-expressed XIAP in the choclear against cisplatin.Methods:1.A total of two animals were studied in this experiment: guinea pigs with(A)round window membrane puncture approach,(B)scala tympani approach,(C)round window membrane treated with collagenase approach,chinchillas with scala tympani approach.2 weeks post the operationgs,ABR was test and transfection efficiency in hair cells were observed.2.Guinea pigs with normal closed field ABR thresholds of was selected,one ear was given r AAV8-XIAP-6myc via RWM treated with collagenase,the other ear given physiological saline.Four of them were intraperitoneal injected with not cisplatin administration,but saline as the normal control group.1 week later,ABR was test,IHCs and SGNs were counted.3.Adult chinchillas with normal closed field ABR threholds were selected.With the scala tympani approacha,one ear was microinjected with r AAV-XIAP-6myc,the other with saline.1 weeks post the injection with 30 mg / kg of carboplatin,ABR thresholds and CAP were detected,the loss of hair cells was observed.Results: 1.Round window membrane treated with collagenase approach were able to achieve high efficient transfection in inner hair cells and outer hair cells(>40%).During the operation we observed that the round window of chinchilla was half-covered with a bone niche,suggesting scala tympani approach should be chosen.There is no significant change in ABR thresholds and efficient transfection(>80%)in inner hair cells were achieved.2.1)Western-blot results suggest successful expression of exogenous XIAP expression in inner ear.2)The XIAP overexpression was found to attenuate cisplatin-induced hearing loss in ABR tests.This was also accompanied by a reduction of the loss of vulnerable hair cells and sensory neurons in the cochlea.3.There is no obvious difference of ABR thresholds post carboplatin injection.CAP amplitudes suggested significant difference at 4k Hz between AAV-XIAP-6myc-treated ear and saline-treated ear.According to the results of the CAP amplitudes,we selected the basilar membrane associated with 4k Hz(10-15mm distance from the apex)to count the loss of IHCs.Conclusions: 1.With RWM treated with collagenase approach,there is high transfeciton efficiency and no damage of the inner ear of.Special cochlear anatomy structure of chinchilla,suggests that scala tympani approach is a better choice.2.r AAV mediated XIAP overexpression in the inner ear can protect against the injury of OHCs and SGNs indeced by cisplatin.3.AAV-XIAP has certain protective effect protecting against cisplatin ototoxity in chinchilla. |
