Study on changes of Cx26 expression level and inner ear development of offspring rats with chronic intrauterine hypoxia

doi:10.3877/cma.j.issn.1673-5250.2015.05.018

Objective

To study the changes of connexin-26(Cx26) expression level and inner ear development of offspring rats after SD pregnant rats suffering from chronic intrauterine hypoxia(CIH) in gestation period.

Methods

A total of 12 healthy SD pregnant rats were chosen as research objects and randomly divided into CIH group and normal group, each consisted 6 SD pregnant rats.CIH pregnant rat models were established for the CIH group.Compared the postnatal weight of different days of offspring rats between two groups statistically and inner ear specimen of offspring rats were extracted on the 56th day after born.Light microscope (HE staining) and electron microscope were used to observe the changes of hair cell development in inner ears.In Situ Nick-End Labeling(TUNEL) method was used to detect the apoptosis of hair cells in corti organ.Western blotting method was used to detect the changes of Cx26 protein expression level in inner ears.

Results

① The weight of newborn offspring rats within 12 hours after birth in CIH group was lower than that of normal group, and the difference was statistically significant [(4.8±0.6) g vs (6.0±0.4) g, t=4.076, P=0.002]. ② The results of light and electron microscopic examination showed that the hair cells in corti organ were deficient and apoptosis could be seen under the electron microscope in CIH group.The relative value of mean optical density of corti organ hair cells, stria vascularis cells and spiral ganglion in cochlear of CIH group were higher than those of normal group, and the differences were statistically significant[(0.42±0.11) vs (0.26±0.09), t=2.758, P=0.020 0; (0.40±0.14) vs (0.19±0.05), t=3.460, P=0.006 0; (0.45±0.12) vs (0.19±0.03), t=5.149, P=0.000 4]. ③ The expression level of Cx26 protein of offspring rats of CIH group were lower than that of normal group, and the difference was statistically significant[(0.72±0.36) mg/(kg·d) vs (1.07±0.19) mg/(kg·d), t=0.785, P=0.042].

Conclusions

Prenatal CIH of SD rats results in intrauterine growth restriction of fetal rats, therefore, offspring rats are born with low birth weight and suffer from hearing damage.

Key words: Chronic intermittent hypoxia, Ear, inner, Cx26 protein, rat, Rats, Sprague-Dawley

表1 两组孕鼠动脉血气分析比较(±s)

组别	鼠数	PaO₂(kPa)	SaO₂(%)	PaCO₂(kPa)	pH值
CIH组	6	7.19±2.75	75.3±3.4	5.98±2.17	7.3±2.2
正常组	6	11.17±2.68	92.6±3.0	6.21±1.15	7.4±1.0
t值		2.538	9.346	0.229	0.101
P值		0.029	0.000	0.823	0.921

表1 两组孕鼠动脉血气分析比较(±s)

组别	鼠数	PaO₂(kPa)	SaO₂(%)	PaCO₂(kPa)	pH值
CIH组	6	7.19±2.75	75.3±3.4	5.98±2.17	7.3±2.2
正常组	6	11.17±2.68	92.6±3.0	6.21±1.15	7.4±1.0
t值		2.538	9.346	0.229	0.101
P值		0.029	0.000	0.823	0.921

表2 两组子鼠生后不同时间点体质量比较(g，±s)

组别	鼠数	生后12 h内	生后21 d	生后56 d	生后105 d
CIH组	6	4.8±0.6	58.8±9.0	306.6±21.0	466.2±71.6
正常组	6	6.0±0.4	52.4±3.0	302.3±11.0	456.2±31.2
t值		4.076	1.652	0.443	0.313
P值		0.002	0.129	0.667	0.760

表2 两组子鼠生后不同时间点体质量比较(g，±s)

组别	鼠数	生后12 h内	生后21 d	生后56 d	生后105 d
CIH组	6	4.8±0.6	58.8±9.0	306.6±21.0	466.2±71.6
正常组	6	6.0±0.4	52.4±3.0	302.3±11.0	456.2±31.2
t值		4.076	1.652	0.443	0.313
P值		0.002	0.129	0.667	0.760

图1 两组子鼠耳蜗切片HE染色结果(图1A：正常组；图1B：CIH组)(HE染色，×40)

图2 两组子鼠耳蜗毛细胞电镜检查结果(图2A：正常组；图2B：CIH组)(电镜，×5 000)

表3 两组子鼠耳蜗毛细胞TUNEL染色不同部位平均光密度值比较(±s)

组别	鼠数	考蒂器	血管纹细胞	螺旋神经节
CIH组	6	0.42±0.11	0.40±0.14	0.45±0.12
正常组	6	0.26±0.09	0.19±0.05	0.19±0.03
t值		2.758	3.460	5.149
P值		0.020 0	0.006 0	0.000 4

表3 两组子鼠耳蜗毛细胞TUNEL染色不同部位平均光密度值比较(±s)

组别	鼠数	考蒂器	血管纹细胞	螺旋神经节
CIH组	6	0.42±0.11	0.40±0.14	0.45±0.12
正常组	6	0.26±0.09	0.19±0.05	0.19±0.03
t值		2.758	3.460	5.149
P值		0.020 0	0.006 0	0.000 4

图3 两组子鼠耳蜗毛细胞细胞凋亡检测(图3A：正常组；图3B：CIH组)(TUNEL染色，×20)

图4 两组子鼠内耳Cx26蛋白表达水平比较

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Huang Huang, Jingcang Lin, Guorong Lyu, Xiangyang Xu, Wendong Lin, Xianyan Xu, Jing Cheng. [J]. Chinese Journal of Obstetrics & Gynecology and Pediatrics(Electronic Edition), 2016, 12(06): 672-679.

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