Effects of recession versus tenotomy surgery without recession in adult rabbit extraocular muscle.
OBJECTIVE
Surgical recession of an extraocular muscle (EOM) posterior to its original insertion is a common form of strabismus surgery, weakening the rotational force exerted by the muscle on the globe and improving eye alignment. The purpose of this study was to assess myosin heavy chain (MyHC) isoform expression and satellite cell activity as defined by Pax7 expression in recessed EOMs of adult rabbits compared with that in muscles tenotomized but not recessed and with that in normal control muscles.


METHODS
The scleral insertion of the superior rectus muscle was detached and sutured either 7 mm posterior to its original insertion site (recession surgery) or at the same site (tenotomy). One day before euthanization, the rabbits received bromodeoxyuridine (BrdU) injections. After 7 and 14 days, selected EOMs from both orbits were examined for changes in fast, slow, neonatal, and developmental MyHC isoform expression, Pax7 expression, and BrdU incorporation.


RESULTS
Recession and tenotomy surgery resulted in similar changes in the surgical EOMs. These included a decreased proportion of fast MyHC myofibers, an increased proportion of slow MyHC myofibers, and increased BrdU-positive satellite cells. Similar changes were seen in the non-operated contralateral superior rectus muscles. The ipsilateral inferior rectus showed reciprocal changes to the surgical superior rectus muscles.


CONCLUSIONS
The EOMs are extremely adaptive to changes induced by recession and tenotomy surgery, responding with modulations in fiber remodeling and myosin expression. These adaptive responses could be manipulated to improve surgical success rates.
Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA.
Stephen P
SP
Christiansen
Rosalia S
RS
Antunes-Foschini
Linda K
LK
McLoon
D000818:Animals; D001973:Bromodeoxyuridine / Q000008:administration & dosage; D018995:Myosin Heavy Chains / Q000378:metabolism*; D009801:Oculomotor Muscles / Q000378:metabolism / Q000601:surgery*; D051763:PAX7 Transcription Factor / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D011817:Rabbits; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism*; D012590:Sclera / Q000601:surgery; D058971:Tenotomy
D051763:PAX7 Transcription Factor; D020033:Protein Isoforms; D018995:Myosin Heavy Chains; D001973:Bromodeoxyuridine