Changes Of Extraocular Muscle After Direct Injection Of Different Concentration Of Nerve Growth Factor In Rabbits

Objective To evaluate the changes of adult rabbit extraocular muscle afterdirect injection of different concentration of nerve growth factor（NGF）.Methods In the self-control study, the left eyes of15adult rabbits wereselected as the experimental group（group A）, and the right eyes as the controlgroup（group B），randomly assigned to three groups.5μg/ml，10μg/ml and20μg/ml NGF was either injected into the superior rectus muscle of eachexperimental eye for0.1ml（group A1, A2, A3）, and the identical volume ofsterilized saline into each control eyes. Two weeks after injection, muscle fibercross-sectional areas was examined. The morphology of the muscles both in theexperimental group and the control group was studied by hematoxylin-eosinstaining under the light microscope，and the MyoD positive cells in superiorrectus muscle were determined by immunohistochemistry.Results (1) Muscle wet weight did not see the four groups are obviouslydifferent. The myofibers mean cross-sectional area of the superior rectos musclewere(9.54±0.42) mm2，（11.71±1.55） mm2，（9.22±1.12） mm2in theexperimental group, and (6.84±0.05) mm2in the control group, with asignificant difference between them(P＜0.05).（2）All the experimental groups and control group rabbit sclera are not seen obvious abnormity after two weeks,no difference between the surface membrane congestion situation. Betweengroups of extraocular muscle hematoxylin eosin staining under the light seemuscle fibers are arranged neatly, direction are consistent, boundaries are clear,no significant cell necrosis and inflammatory cells infiltration.（3）Theperimeter of the superior rectus muscle were (194.25±17.78) μm，（230.67±17.25）μm，（183.81±21.28）μm， in the experimental group and （135.29±13.39）μm in the control group, with a significant difference betweenthem(P<0.05).The frequencies of large and middle fibers in the muscles werehigher in the experimental group than in the control group (P<0.05).（4）Theproportion of activated satellite cells was higher in the experimental group withstatistical significance（P<0.01）.The proportion of MyoD positive cells washigher in the experimental groups than that in the control group （P=0.000).（5）We estimate the trade-offs among these characteristics and see no statisticallysignificant difference between group A1and A3(P>0.05), however group A2was statistically significant with the others (P <0.05).Conclusion Single direct injection of NGF into extraocular muscles is ansafe and effective procedure. Three concentrations of nerve growth factor canincrease the extraocular muscle fibers proliferation, and can promote the musclesatellite cell activation especially10μg/mL.