Experimental Observation Of Auditory-vestibular Fuction And Inner Ear Morphology In Smad5 Knokout Mice

Part 1 Experimental observation of auditory-vestibular function and inner ear morphology in Smad5 knockout miceObjective: To observe the change of morphology and auditory-vestibular function of Smad5 knockout mice Smad5(+/-) and investigate if Smad5 is a involved gene in the vestibualr function. Method: ABR and click-evoked potentials on the surface of the cervical dura mater were tested in 20 Smad5(+/-) mice and 15 Smad5(+/+) as control. The morphological changes of vestibule and cochlea were observed in semi-thin section in temporal bone.Result: The average threshold of ABR in Smad5 (+/-)mice was 72.25±10.23dB (SPL) and that of Smad5 (+/+) mice is 37.75±16.65dB (SPL) .The difference between the two groups is significant (P<0.01) ; The latency of Click-Evoked Potentials on the surface of the cervical dura mater in Smad5 (+/-) mice is 6.85±0.23ms, 6.78±0.20ms and 6.70±0.43ms at the intensity of 85dB, 95dB and 105dB respectively. While that of the Smad5 (+/+) mice is 6.35±0.28ms, 6.22±0.49ms and 6.17±0.73ms.The prominent changes in the semi-thin section of Smad5 (+/-) mice were the sensory cells loss in the saccule, utricule and ampullarae, and the loss in the spiral ganglion and vestibular ganglion. While morphological changes in above mentioned structures in Smad5 (+/+) mice were scattered loss of sensory hair cell and ganglion neuron. Conclusion: TGF-8/Smad5 knockout can induce moderate to severe hearing loss and prolongation of the latency of click-evoked potentials on the surface of the cervical dura mater. Also it resulted in the morphological change of the sensory cells in vestibular organ and vestibular ganglion neuron. The mechanism of elongation of the latency of click-evoked...