Continuous myonuclear addition to single extraocular myofibers in uninjured adult rabbits.
Extraocular muscles (EOM) are unique among mammalian skeletal muscles in that they normally express molecules associated with muscle development and regeneration. In this study we show that satellite cells of EOM, unlike those of other skeletal muscles, continually divide in the normal, uninjured adult. Adult EOM contained activated satellite cells positive for the myogenic regulatory factor MyoD. EOM satellite cells did not require a prolonged activation period prior to onset of cell division and differentiation in vitro. EOM satellite cells incorporated bromodeoxyuridine (brdU), a marker for cell division, and with longer postlabeling survival, brdU-labeled nuclei populated EOM myofibers. This was not seen with leg muscle. These findings suggest the possibility that continual division of satellite cells and fusion of their daughter myocytes with existing adult EOM myofibers contribute to the unique sparing or susceptibility of EOM to certain muscle diseases.
McLoon
Linda K
LK
Department of Ophthalmology, University of Minnesota, Lions Research Building, Room 374, 2001 Sixth Street SE, Minneapolis, Minnesota 55455, USA. mcloo001@tc.umn.edu
Wirtschafter
Jonathan D
JD
D000367:Age Factors; D000818:Animals; D000963:Antimetabolites; D001973:Bromodeoxyuridine; D002467:Cell Nucleus / Q000502:physiology*; D002478:Cells, Cultured; D016189:Dystrophin / Q000032:analysis; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology* / Q000502:physiology; D017570:MyoD Protein / Q000032:analysis; D009801:Oculomotor Muscles / Q000166:cytology* / Q000502:physiology; D011817:Rabbits
D000963:Antimetabolites; D016189:Dystrophin; D017570:MyoD Protein; D001973:Bromodeoxyuridine