Experimental Study Of Super-pulse CO2 Laser On Morphology Damage Of Guinea Pig Cochlea

【Objective】To investigate the effect of super-pulse carbon dioxide(CO2) laser irradiation to basal turn of cochlea on the structure of the inner ear in guinea pigs, a fenestration was obtained in the basal cochlear turn of guinea pigs in vivo. And comparing to the control group, attempted to obtain some evidence for safely application of laser in ear surgery.【Methods】Anatomized four guinea pigs with acoustic capsule approach and post aurem approach, to study the middle ear anatomic structures and determine the optimal operative approach to the basal turn of cochlea.48 guinea pigs were randomly equally divided into 4 groups. The basal turn of cochlea was irradiated by super-pulse carbon dioxide laser with out-put power of 1W,2W and 3W respectively. The left ears are experimental group and the right ears are control group.Immediately and two weeks after irradiation, the animals were decapitated in batch. Light and scanning electron microscopies were performed to observe the morphological alteration. Six hours after irradiation, the expression of the Hsp70 was detected by immunohistochemisty.【Results】Immediately after irradiation, through optical microscope, control group's outer and inner hair cell showed no abnormalities. Swelling and deeply staining of outer hair cells and dilation of stria vascularis were present in the cochlea of experimental groups. Immediately after irradiation, through scanning electron microscopies, control group and 1W group were found that the stereocilia and cuticular plates of the inner and outer hair cells and supporting cells showed normal configuration. However, with 2W,3W irradiation, part of the outer hair cells collapsed and derangement of the stereocilia were observed, especially in the third row of the basal turn, but the inner hair cells showed normal configuration. Two weeks after irradiation, through scanning electron microscopies,2W group's outer and inner hair cell showed no abnormalities. In 3 W group, we could see that part of the outer hair cells collapsed and the stereocilia deranged, especially in the third row of the basal turn, but the inner hair cells showed normal configuration.Six hours after irradiation, the expression of HSP70 in control group's cochlea spiral ganglion, basilar membrane and spiral ligament were weakly positive, experimental group's spiral ganglion, basilar membrane and spiral ligament were positive. With the enlargement of laser dose, the number of positive cells and the percentage of positive cells gradually increased. There was statistical significance between 3W group and other groups (p<0.05).【Conclusion】1,Acoustic capsule approach as a simple, easy exposure to the basal turn of cochlea, with less post-operative complications, was considered as the optimal operative approach.2,Low-dose super-pulse CO2 laser could effectively ablate the bone wall of basal turn of cochlea, and it did not damage the inner ear structures in the limited parameters, but the impact of inner ear function remains to be further studied.3,The expression of Hsp70 was induced in guinea pigs cochlea fenestration after laser irradiation, which related to the damage degree of the cochlea. HSP70 might play a role in protecting the cochlea from damage.