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R.S. Antunes–Foschini, F.S. Ramalho, L.N. Z. Ramalho, H.E. A. Bicas; Frequency of Myod Positive Satellite Cells on Medial Recti and Inferior Oblique Muscles From Patients With Exotropia, Exotropia and Overacting Inferior Oblique Muscles and From Patients Without History of Strabismus . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5057.
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© ARVO (1962-2015); The Authors (2016-present)
Satellite cells (SC) are responsible for skeletal muscle growing, regeneration or hipertrophy. In these situations, they are activated and positive to MyoD1, a lineage specific myogenic marker. In other conditions they are quiescent. Mammalian adult extraocular muscles show 2–4% MyoD1 positive SC, besides the addition of some new nuclei to the existing myofibers. Exotropia is an horizontal strabismus, asociated or not with inferior oblique muscles (IOM) overactions. Different capabilities of SC activation may be envolved in the genesis of strabismus. This study quantified MyoD positive SC on IOM and medial recti muscles (MRM) from 14 patients with exotropia (XTG), 4 of them with IOM overaction, and from specimens obtained from cornea donors (control group, CG).
Fourteen patients who were submitted to ressection of a fragment of MRM to treat surgically their exotropias compounded XTG. Four were also submitted to myectomia due to IOM overaction. Transversal sections from MRM (n=14) and IOM (n=4) fragments and from 10 fragments of IOM and 11 fragments of MRM of cornea donors with no history of strabismus or muscle diseases (CG) were analysed by an immunohistochemistry study with antibody anti–MyoD1. SC were counted in percentage of the number of SC labelled nuclei each 100 myofibers counted.
MRM and IOM from CG showed, respectivelly, 2 and 3% of SC nuclei labelling. XTG showed 27.5% and 2%, respectivelly, for IOM and MRM groups.
XTG showed higher levels of MyoD labelled SC on IOM compared to CG, while the index of SC positive for MyoD1 were not different on MRM from CG and XTG. These findings show that different capabilities of renewal of muscular tissue, envolving SC, may be correlated to the genesis of under or overaction of extraocular muscles. Overacting muscles (IOM) showed higher indexes of activated SC, while underacting muscles (MRM) did not show differences compared to the CG. Different index labbeling obtained from MRM and IOM of the same eye in 4 patients suggests there is a small probability of the influence of the surgical act on the results.
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