Smad5基因敲除小鼠耳蜗扫描电镜观察

Scanning electron microscopic morphology in the cochlea of Smad5 mutant mice

目的观察Smad5基因敲除杂合(3月组2只小鼠4只耳蜗)子小鼠内耳形态学超微结构变化。方法野生型动物组:1个月组4只小鼠5只耳蜗,2个月组及3个月组各有2只小鼠4只耳蜗;杂合子动物组1个月组3只小鼠3只耳蜗,2个月组2只小鼠4只耳蜗,3个月组3只小鼠6只耳蜗。按常规方法制成标本作扫描电镜观察。结果Smad5基因敲除杂合子小鼠扫描电镜观察:1月组耳蜗中均观察到耳蜗第一和第二圈外毛细胞有不同程度的静纤毛融合,未见外毛细胞缺失,内毛细胞未见明显地病理变化。2月组耳蜗中观察到第一和第二圈均可见内外毛细胞静纤毛不同程度缺失,有的部位以内毛细胞静纤毛缺失为主,而有的部位以外毛细胞静纤毛缺失为主,有的以片状缺失为主,有的则以散在性缺失为主。3个月组3只小鼠6只耳蜗中均观察到不同程度第一和第二圈内外毛细胞静纤毛广泛性缺失,有外毛细胞缺失的部位多,以第一排外毛细胞的静纤毛缺失为主,第二和第三排外毛细胞静纤毛多以散在性缺失为主,有内毛细胞缺失的部位多伴有外毛细胞静纤毛的大片状缺失。野生型动物组扫描电镜观察:1个月组4只小鼠5只耳蜗,2个月组2只小鼠4只耳蜗均未观察到内外毛细胞缺失和静纤毛的变化,3月组有少量的外毛细胞缺失。结论野生型小鼠2个月以内耳蜗毛细胞无明显变化.杂合子小鼠随着月龄的增加内外毛细胞缺失的程度逐渐加重。

Objective To observe the morphologic changes in inner ears of Smad5 （＋/-） heterozygote mice at different months of age. Methods Scanning electron microscope（SEM） observation, was performed in five cochleae from four wild type （WT） mice of one month of age and four cochleae from two WT mice of two months of age. As regards the heterozygotes, three cochleae from three mice of one month of age, four cochleae from two mice of two months of age and six cochleae from three mice of three months of age were examined with SEM. Results In heterozygotes, SEM data from mice of one month of age showed that there was coalesce of stereocilia of outer hair cells （OHCs） in the first and second turn to different degree without loss of outer hair cells and inner hair cells. SEM data from mice of two months of age showed that there was different degree absence of stereocilia of inner and outer hair cells in the first and second turn. In some sites most of these absent stereocilia are from inner hair cells and in other sites, from outer hair cells. At the same time some absence showed a patchy distribution while some appeared scattered. Mice of three months of age demonstrated extensive absence of stereocilia of inner and outer hair cells in the first and second turn. In the sites of absence of outer hair cells, stereocilia loss of the first OHC row accounted for majority of the absence. Meanwhile absence of inner hair cells often accompanied with patchy absence of stereocilia of OHCs. In wild type mice, absence of inner and outer hair cells and changes of stereocilia had not been observed except sparing outer hair cell loss in mice of three months of age.Conclusion There is changes in hair cells in WT mice within two months of age.The absence of innerand outer hair cells in heterozygote mice increased with inereasing age.