September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
A sturdy connective tissue network surrounds all the extraocular muscle fibers
Author Affiliations & Notes
  • Fatima Pedrosa Domellof
    Clinical Sciences, Ophthalmology, UMEA University, Umea, Sweden
  • Linda K McLoon
    Dept of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Mona Lindström
    IMB, Anatomy, UMEA University, Umea, Sweden
  • Footnotes
    Commercial Relationships   Fatima Pedrosa Domellof, None; Linda McLoon, None; Mona Lindström, None
  • Footnotes
    Support  Supported by The Swedish Research Council (K2012- 63x-20399-06-3 and 2015-02438_3; Stockholm, Sweden), the County Council of Vasterbotten (Cutting Edge Medical Research and Central ALF; Umea, Sweden), EY15313 from the National Institutes of Health (LKM), the Minnesota Lions and Lionesses (LKM), and an unrestricted grant to the Department of Ophthalmology from Research to Prevent Blindness, Inc.
Investigative Ophthalmology & Visual Science September 2016, Vol.57, No Pagination Specified. doi:
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      Fatima Pedrosa Domellof, Linda K McLoon, Mona Lindström; A sturdy connective tissue network surrounds all the extraocular muscle fibers. Invest. Ophthalmol. Vis. Sci. 201657(12):.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Recent reports suggest that the different compartmentss of the extraocular muscles can contract independently. As this is in contrast to how other skeletal muscles function, we examined the connective tissue endo-, peri-, and epimysium to determine the biological feasibility of this view.

Methods : Normal human EOMs were serially cross-sectioned and processed for immunohistochemistry with antibodies specific against Collagen I, III IV , VI and elastin. Human and rabbit EOMs were fixed and processed for scanning electron microscopy (SEM).

Results : Col III, IV, and VI nicely delineated the contours of all muscle fibers, and Col VI was also found in the perimysial space. In contrast, Col I was mostly present in the interstitial perimysial space. Elastin was found surrounding individual myofibers both circumferentially and longitudinally, as well as running between neighboring fibers. Col I, VI, and elastin were all seen to run equally between all parts of the muscle, including between the orbital and global layers.
SEM revealed a very prominent network of fibrils around the individual muscle fibers, showing a network of highly interconnected and sturdy channels within which the fibers are contained. These interconnected networks ran from the epimyisum to the endomysium around each myofiber, forming a continuous and prominent network, with a continuous and tight matrix interconnection between the orbital and global layers.

Conclusions : This massively interconnected collagen matrix likely results in significant lateral force transmission. This finding helps explain the ”loss of additive force” seen in experiments where the stimulation of multiple motor units does not equal the sum of the forces of each stimulated singly. It also supports the view that individual compartmental movements could not be possible if the epimysium is intact.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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