The influence of IGF-Ⅰ on the expression of Myf5 and TGF-β1 in medial rectus muscle of cat model with strabismus

Abstract

Objective: To observe the influence of exogenous insulin-like growth factor-Ⅰ(IGF-Ⅰ) on the expression of myocyte differentiation factor 5 (Myf5) and transforming growth factor β1(TGF-β1) in medial rectus muscle of cat model with strabismus. Methods: Experiment research. Twenty-seven kittens which were in sensitive period of visual development (4-6 weeks old), were randomly divided into experimental, control and blank control groups by random numbers table method. Each experimental group was further divided into 3 sub-groups (4 weeks, 8 weeks and 12 weeks) based on drug intervention time, hence 3 kittens in each sub-group. The control group and the blank control group were also divided into 3 sub-groups respectively. Exotropia treatment models were set up through surgical methods and injection of IGF-Ⅰ(0.05 ml,0.1 g/L). The internal rectus muscles of 4 weeks sub-group, 8 weeks sub-group and 12 weeks sub-group were taken respectively after the treatment model had been set up. The internal rectus muscles of the control group and the blank control group were also taken according to corresponding time. The expressions of Myf5 and TGF-β1 were tested with immunohistochemistry staining method, and optical density analysis method were employed to measure the average optical density value. The expression of Myf5 and TGF-β1 was analyzed by Kruskal-Wallis and Bonferroni test. The correlation between the expression of Myf5 and TGF-β1 and the time of drug intervention was analyzed by simple linear regression. Results: (1) In the experimental group, the expression of the Myf5 of the 4 weeks sub-group, 8 weeks sub-group and 12 weeks sub-group were 33.34±17.16, 39.24±15.25 and 47.70±19.39, which were higher than the control group (21.30±7.44, 19.43±4.75, 4.82±2.66) and the blank control group (18.95±6.59, 18.00±7.29, 5.86±2.61) at the same time point, and the differences were statistically significant in 8 weeks sub-group and 12 weeks sub-group (χ(2)=21.864, 31.814, both P<0.01). The expression of Myf5 in the experimental group increased with the extension of IGF-Ⅰ intervention time (R(2)=0.99, P<0.05). But there were negative correlation between expression of Myf5 and drug intervention times in the control group and the blank control group (R(2)=0.81, 0.80, both P<0.05). (2) In the experimental group, the expression of the TGF-β1 of the 4 weeks sub-group, 8 weeks sub-group and 12 sub-weeks group were 0.80±0.12, 0.53±0.09, 0.42±0.08, which were higher than the control group (1.91±0.23, 2.30±1.03, 1.82±0.72) and the blank control group (2.01±0.31, 2.62±1.11, 1.83±0.67) at the same time point, and the differences were statistically significant (χ(2)=30.801, 40.278, 35.177, all P<0.01). The expression of TGF-β1 in the experimental group decreased with the extension of IGF-Ⅰintervention time (R(2)=0.83, P<0.05). The average optical density value regression equation of TGF-β1 in the sterile water control group and the blank control group was 0.04 and 0.06, respectively, and the fitting degree was very poor. Therefore, there was no correlation trend with time. Conclusions: Exogenic IGF-Ⅰ could enhance the expression of Myf5 in medial rectus muscle of cat model with strabismus. Exogenic IGF-Ⅰ could inhibit the expression of TGF-β1 in medial rectus muscle of cat model with strabismus. Repeated injection of exogenous IGF-Ⅰ may continuously enhance the expression of Myf5 and inhibit the expression of TGF-β1. (Chin J Ophthalmol, 2018, 54: 375-382).