The cytoskeleton of myotendinous junctions in human extraocular muscles

• Purpose: To systematically investigate the composition of the cytoskeleton of the myotendinous junctions (MTJs) in human extraocular muscles (EOMs).Methods: Ten human EOM samples collected with ethical permission were processed for immunofluorescence with antibodies against the cytoskeletal proteins desmin, nestin, vimentin and cytokeratin 19; various myosin heavy chain (MyHC) isoforms as well as antibodies against tenascin or laminin to identify the MTJs.Results: The majority of the MTJs in both orbital and global layer contained desmin but an important proportion of them did not show increased levels of immunostaining at the folds of the MTJ, in contrast to other muscles. Desmin was absent from approximately 15% of the MTJs and mostly in myofibers containing MyHCIIa. Nestin was present in approximately 91% of the MTJs. Four different combinations were encountered regarding immunolabeling for desmin+nestin at the MTJs, including absence of both in a subgroup of MTJs, irrespective of fiber type. Vimentin was not present at the MTJs and cytokeratin 19 was either present or absent from the MTJs.Conclusions: The present data on the composition of the cytoskeleton at the MTJs in the EOMs raises fundamental questions regarding our previous knowledge on the role of these proteins for force transmission. We propose a novel model to further investigate these questions.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Oftalmologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Ophthalmology (hsv//eng)

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