Effects Of Insulin-like Growth Factor-Ion Myf5 And MyoD Expression In Rectus Of Exotropia Cat Models

Objective: The present study was to investigate whether exogenous IGF-I can upregulate the expression of MyoD and Myf5 in the medial rectus muscle of exotropia model of cat,and to further explore the feasibility of exogenous IGF-I in the treatment of strabismus.Methods: Twenty-seven kittens being in visual development stage were included in this study,which were randomly divided into 3 groups,the treatment group,the standard control group and the normal control group,each with 9 kittens.Each group was divided into three sub-groups based on the postoperative period,each with 3 kittens.In the experimental group,50μL(5μg)of exogenous IGF-I was injected into the medial rectus of the right eye of the experimental cats immediately and every two weeks after operation.The standard control group was injected with sterile water in the same way.The normal control group was only be made into strabismus model without any injections.These experimental exotropia kittens were sacrificed at 4 weeks,8 weeks and 12 weeks after operation and treatmen.In present study,extraocular muscle tissue was used to extract RNA from the extraocular muscles,and then we use the collected RNA for qPCR to quantify the expression of MyoD and Myf5 in the right medial rectus of each group and observe the changes of their expression with the prolongation of treatment time.Results:(1)The expression of Myf5 in mRNA level in IGF-I treatment group was higher than that in sterile water group and blank control group 4 weeks after operation,but there is no statistical difference among the three groups(P=0.122).The expression of Myf5 mRNA in IGF-1 treatment group was significantly higher than that in both of the two control groups(P <0.01)8 weeks later,and the expression was higher in blank control group than that in sterile water group(P <0.01).12 weeks later,the expression of Myf5 mRNA in IGF-1 treatment group was significantly higher than that in control groups(P<0.01),but there was no significant difference between sterile water group and sterile water group(P=0.769).(2)The expression of MyoD in mRNA level in IGF-I treatment group was higher than that in sterile water group and blank control group 4 weeks after operation,but there was no statistical difference among the three groups(P=0.267).The expression of MyoD mRNA in IGF-1 group and blank control group was higher than that in sterile water group(P <0.01)8 weeks later,however there was no significant difference between IGF-1 treatment group and blank control group(P=0.354).12 weeks later,The expression of MyoD mRNA in IGF-1 treatment group was significantly higher than that in control groups(P<0.01),but there is no significant difference between sterile water group and normal control group(P=0.095).(3)The expression of Myf5 in mRNA level in IGF-I treatment group increased gradually with the prolongation of treatment time,and was positively correlated with treatment time(r= 0.949,P <0.01).There was significant increase or decrease of the expression of Myf5 mRNA in sterile water group,and there was no positively correlated with treatment time(r=0.949,P<0.01).The expression of Myf5 in mRNA level was significantly increased in blank control group at 8 weeks after operation,however it decreased at 12 weeks after operation,and there was no positively correlated with treatment time(r=0.053,P=0.893).(4)The expression of MyoD in mRNA level in IGF-I treatment group increased gradually with the prolongation of treatment time,and was positively correlated with treatment time(r=0.949,P <0.01).There was no positively correlated with treatment time in sterile water group(r=0.949,P<0.01).(6)The expression of MyoD in mRNA level was significantly increased in blank control group at 8 weeks after operation,however it decreased at 12 weeks after operation,and there was no positively correlated with treatment time(r=0.527,P=0.145).Conclusion: IGF-I local injection probably upregular the expression of Myf5 and MyoD in mRNA in the extraocular muscles,and its effect is more obvious with the prolongation of the treatment time.