胰岛素样生长因子结合蛋白-4对雏鸡眼外肌形态和功能的影响

Effects of insulin-like growth factor binding protein 4 on morphology and function of chick extraocularmuscle

背景 研究表明胰岛素样生长因子（IGF）眼外肌肌内注射可使发育中的眼外肌增厚,收缩力增加,IGF的缺乏可能与斜视的发生有关,但其抑制剂胰岛素样生长因子结合蛋白-4（IGFBP-4）眼外肌注射后是否能够进一步证明其作用,目前相关的研究较少. 目的 观察IGFBP-4对发育中雏鸡眼外肌形态和收缩力的影响,探讨IGFBP-4对斜视眼眼外肌形态结构的影响. 方法 选取出生后1d的雏鸡24只,左眼作为实验眼,于左眼眼眶上缘进针将2μ1 IGFBP-4注入上直肌内,质量浓度为1 g/L,隔日注射,连续5次,右眼用同法注入生理盐水2 μ1.于末次眶内注射后2d以过量麻醉法处死实验动物,取12只雏鸡眼的上直肌,用张力换能器测定其最大收缩能力及单位横截面积的最大收缩能力.另取12只雏鸡上直肌制作组织切片,行苏木精-伊红染色,评价IGFBP-4注射眼外肌与生理盐水注射眼上直肌的形态变化,并用计算机图像分析系统测量肌纤维直径,对两组雏鸡眼外肌的肌纤维直径进行比较. 结果 雏鸡IGFBP-4注射眼上直肌的最大收缩力为（1.602±0.080） mN,而生理盐水注射眼为（1.815±0.010） mN,IGFBP-4注射眼上直肌最大收缩力明显低于生理盐水注射眼,差异有统计学意义（t=13.65,P＜0.01）；IGFBP-4注射眼和生理盐水注射眼上直肌单位横截面积最大收缩力分别为（95.500±7.420） mN/cm2和（101.510±5.220） mN/cm2,两组比较差异有统计学意义（t=28.81,P＜0.01）.雏鸡上直肌组织形态学检查显示,IGFBP-4注射眼外肌肌纤维中细小纤维较生理盐水注射眼有所增加,但肌纤维结构无明显区别.IGFBP-4注射眼上直肌肌纤维平均直径为（8.7±0.5） μm,与生理盐水注射眼的（9.1-0.4） μm比较,差异无统计学意义（t=0.75,P=0.46）,但肌纤维在不同直径的分布差异均有统计学意义（P＜0.05）. 结论 IGFBP-4的眼外肌内注射会造成发育中的眼外肌肌纤维变细,引起眼外肌的收缩功能下降,进一步证实IGF对发育中的眼外肌有神经营养作用.

Background Researches have showed that the extraocular muscle injection of insulin-like growth factor（IGF） results in the thickness of extraocular muscle and enhancement of contractility,and lack of IGF probably is associated with pathogenesis of strabismus.If extraocular muscle injection of insulin-like growth factor binding protein 4（IGFBP-4）,an inhibitor of IGF,can further ensure the effect of IGF is still under-investigation.Objective The aim of this study was to evaluate the effects of IGFBP-4 on the developing extraocular muscle.Methods IGFBP-4 of 2 μl（1 g/L）was injected into superior rectus muscles via supraorbital margin in the left eyes of 24 postnatal l-day-old chickens once every other day for five times,and the equivalent amount of normal saline solution was used in the same way in the fellow eyes as controls.The animals were sacrificed by overdose of anesthesia 2 days after the final injection and 12 animals were randomly selected for the maximal contractility test of superior rectus muscle.The other 12 pieces of superior rectus muscle of the chickens were obtained for the hematoxylin ＆ eosin staining to evaluate the morphology of superior rectus muscle and calculate the myofiber diameter using imaging system.Results The maximal contractility was （1.602 ± 0.080） mN and（1.815±0.O10）mN in the IGFBP-4 injection group and normal saline solution group respectivily,showing a significant difference between the two groups（t =13.65,P〈0.01）.The maximal contraction force in cross-sectional area was （95.500 ± 7.420） mN/cm2 in the IGFBP-4 injection group and it was significantly lower than that of the normal saline solution group（101.510±5.220）mN/cm2（t =28.81,P〈0.01）.Histological examination showed that thin myofibers were obvious more in the IGFBP-4 injection group than those with saline injection.The mean diameter was （8.7 ± 0.5） μm in the IGFBP-4 injected group,and that of the normal saline group was（9.1 ±0.4） μm,there was no significant difference between them （t =0.75,P =0.46）.However,significant differences were found in the number of different diameters of myofibers between the two groups（all at P〈0.05）.Conclusions IGF is one of the key nutrition factors in the development of extraocular musele.The extraocular muscle injection of IGFBP-4 may cause the dysfunction and morphologic abnormality of extraocular muscle.