Histopathological features and satellite cell population characteristics in human inferior oblique muscle biopsies: clinicopathological correlation

Abstract

To investigate the correlation between clinical characteristics and histopathological and immunohistochemical features of inferior oblique muscles in patients with primary and secondary inferior oblique overaction. Inferior oblique muscle specimens of patients who underwent inferior oblique-weakening procedures for primary or secondary inferior oblique overaction were recruited. Subjects were mainly divided into two groups, each of which was further divided into two subgroups: group 1 included patients with primary inferior oblique overaction (subgroups, infantile esotropia vs acquired V-pattern esotropia), and group 2 included patients with secondary inferior oblique overaction (subgroups, congenital vs acquired trochlear nerve palsy). Inferior oblique overaction was graded between 0-4. Histopathologic changes, such as angular fibers, endo- and perimysial fibrosis, and vacuolization were categorized from mild to severe. Immunohistochemical markers Pax7, NCAM, and MyoD1 were used to detect satellite cells, a unique stem cell population in muscles presumably responsible from myofiber regeneration and maintenance, and their activity. Results were reported as stained cells per cross-section ratio. A total of 51 patients were included: 36 in group 1 and 15 in group 2. Satellite cell distribution and activity was significantly higher in group 1 (P<0.001). The angular fiber count and the degree of perimysial fibrosis was higher in the secondary group (P<0.001 and P=0.01, resp.). There was no correlation between clinical amount of inferior oblique muscle overaction and immunohistochemical markers. The differences in immunohistochemical parameters supported with histopathological changes between different strabismus etiologies imply that satellite cell population behavior varies among strabismus types.