Study Of The Activated Muscle Satellite Cell And The MyoD MRNA Expression In Overacting Inferior Oblique Muscle

ObjectiveIn the examination of eye movements for strabismus, the overaction of inferior oblique muscle is normal. But the pathogenesis is not clear.The purpose of the topic is to observe the morphologic change of the overacting inferior oblique muscle, to detect the muscle satellite cells with MyoD+in the overacting inferior oblique muscle by immunohistochemistry stain methods，and to detect the expression of MyoD mRNA in the normal, constitutional overacting, sencondary overacting inferior oblique muscle by SYBR Green I fluorescent reverse transcription polymerase chain reaction.To investigate the influence of activated satellite cells and MyoD to the overacting inferior oblique muscle.Methods1. The case group was to collect13cases with constitutional overaction of inferior oblique muscle,13cases with sencondary overaction of inferior oblique muscle by random.the control group was the normal inferior oblique muscle.Intercepted the overacting inferior oblique muscle with4-6mm from patients undergoing surgical resection, the normal inferior oblique muscle was obtained from patients undergoing eyeball removal,intercepted the normal inferior oblique muscle with3-4mm. Fixed and scliced the muscle tissue.and then carried out routine HE stain and immunohistochemistry stain. Observed the morphologic of the inferior oblique muscle and the percentages of MyoD+satellite cells per100myfibers.2. The method to divide group and to obtain the muscle was the same as part one. Extraction RNA from the fresh muscle tissue, and to detect the expression of MyoD mRNA by SYBR Green I fluorescent RT-PCR,Significant diffrences between groups were evaluated by One-way ANOVA and LSD-t test.Results1. The arrange of the constitutional overacting inferior oblique muscle fiber is disorder,the diameter of the muscle fiber is different, some of the diameter of the muscle fiber is thickening,some of the nucleus of the muscle fiber move depart from cell membrane,some of the muscle bundle fuse;the morphologic changes of the secondary overacting inferior oblique muscle is the same as the constitutional overacting infefrior oblique muscle.The cross section area of the constitutional overacting inferior oblique muscle fiber is bigger than the normal inferior oblique muscle fiber(P<0.05); the cross section area of the secondary overacting inferior oblique muscle fiber is bigger than the normal inferior oblique muscle fiber(P<0.05).2. The percentage of MyoD+satellite cells of the constitutional overacting inferior oblique muscle is17.7%±3.3%,which is higher than the normal inferior oblique muscle(P<0.05);the percentage of MyoD+satellite cells of the secondary overacting inferior oblique muscle is16.6%±4.6%, which is higher than the normal inferior oblique muscle(P<0.05); there is no significant difference between the constitutional overacting inferior oblique muscle and the secondary overacting inferior oblique muscle in the percentage of MyoD+satellite cells(P>0.05).3. The expression of MyoD mRNA in the constitutional overacting inferior oblique muscle is0.77±0.09;which is higher than the normal inferior oblique muscle(P<0.05);the expression of MyoD mRNA in the secondary overacting inferor oblique muscle is0.75±0.12;which is higher than the normal inferior oblique muscle(P<0.05)Conclusion1. The morphologic changes of the constitutional overacting inferior oblique muscle and the secondary overacting inferior oblique muscle are the same,the arrange and the diameter of the muscle fiber changed, the diameter of some muscle fibers enlarged,some of the muscle bundle fuse. The diameter of muscle fiber become bigger.which lead to the thickening of the muscle fiber;the fusion of the muscle bundle leads to strengthen of the contractility.the morphologie changes are correlation with the overacting inferior oblique muscle.2. The MyoD+muscle satellite cells and the MyoD mRNA increase in the overacting inferior oblique muscle,which represent the increasing of the activated satellite cells.We suspect that, the activated muscle satellite cells induce regeneration and remodeling of the inferior oblique muscle, the contractility of the inferior oblique muscle strengthened.lead to the overaction of the inferior oblique muscle.