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R. S. Antunes-Foschini, D. Miyashita, H. E. A. Bicas, L. K. McLoon; Increased Numbers of Activated Satellite Cells in Muscles From Patients With Medial Rectus Underaction. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5623.
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The goal of this study was to determine if the medial rectus muscles of patients with a history of medial rectus underaction show alterations in the process of satellite cell activation when compared to normal age-matched control muscles.
Medial rectus muscles were obtained with consent from adult patients undergoing surgical resection due to medial rectus underaction and prepared for histological examination by fixation and paraffin embedding. Control muscles were obtained from adult cornea donors who had no history of strabismus or neuromuscular disease. Cross-sections were obtained and immunohistochemically for the presence of MyoD-positive satellite cells, and the percentage of MyoD positive satellite cells per myofiber was calculated.
As predicted from the literature, MyoD-positive satellite cells, indicative of activation, were present in both the control and resected muscles. In the underacting medial rectus muscles, the frequency of MyoD positive satellite cells was approximately 2.5 fold higher than the percent seen in control muscles.
The presence of increased numbers of activated satellite cells in the resected underacting medial rectus muscles was paradoxical. This upregulation in the number of MyoD positive satellite cells correlates with increases in activation of satellite cells seen after functional denervation in extraocular muscles, and with increases in MyoD positive cells in laryngeal muscles both acutely and chronically after section of the recurrent laryngeal nerve. It suggests that there is potential for successful reinnervation of these muscles, as the cellular machinery for muscle repair and regeneration, the satellite cells, are retained in patients with medial rectus underaction.
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