Effects Of Insulin - Like Growth Factor - â…  On MyoD And Myogenin Expression In Experimental Esotropia

Objective Observing the expression changes of Myo D and Myogenin in media rectus muscle of cat model with extropia after direct injection of insulin-like growth factor-I(IGF-I), to evaluate the relationship between the strabismus and the effect of direct injection of IGF-I on the extraocular muscles.Method Select 27 little cats(4-6 weeks old), which were in sensitive period. All animals were randomly divided into experimental, sterile water and blank control groups. We producted extropia model through surgical methods. The medial rectus muscles of the extropia model recived the direct injection of 50μl(5μg) IGF-I or 50μl sterile water immediately, respectively as the experimental group and the sterile water group, then once every two weeks later. Blank control group only preparated extropia model. Respectively after strabismus surgery 4, 8, 12 weeks, collected medial rectus muscles of the experimental, sterile water and blank control groups. These collection were prepared for histologic examination by fixation, paraffin embedding and slice. By Immunohistochemistry staining to detect Myo D and Myogenin expression and by optical density analysis method to measure the average optical density value.Results ①There is a significant difference(P<0.05) of the Myo D and Myogenin expression in the medial rectus muscle between the experimental group with the other two groups. Then there are no obvious differences(P>0.05) of Myo D and Myogenin expression between the sterile water group and blank control group. ②There were significantly positive correlation between the expression of the Myo D and Myogenin in the experimental groups and the duration of intervene( r Myo D=0.347,P<0.01;r Myogenin=0.395,P<0.01). There was significantly negative correlation between the expression of Myogenin in the two other groups and the duration of intervene(rsterile water=-0.524,P<0.01;rblank=-0.602,P<0.001). There was no significance correlation between the expression of Myo D in the other two groups and the duration of intervene(P>0.05).Conclusion The expression of Myo D and Myogenin increased after sequentially direct injection of IGF-I; With the time of IGF-I injection increased, the expression of two kinds of factors were on the rise.