Dataset Information

Perimysial fibroblasts of extraocular muscle, as unique as the muscle fibers.

ABSTRACT: Extraocular muscle (EOM) has a distinct skeletal muscle phenotype. The hypothesis for the study was that fibroblasts support the unique EOM phenotype and that perimysial fibroblasts derived from EOM have properties that distinguish them from fibroblasts derived from other skeletal muscle.Perimysial fibroblasts from leg muscle (LM-Fibro) and EOM (EOM-Fibro) of mice were derived and maintained in culture. EOM- and LM-Fibro were assessed morphologically and for vimentin, smooth muscle actin, and Thy-1 immunoreactivity. DNA microarray analysis was performed on LM- and EOM-Fibro grown in conditions that support myoblast differentiation. To assess trophic interactions, co-cultures of myoblasts from established cell lines, CL-EOM and CL-LM with, EOM- or LM-Fibro were performed in direct contact and in a permeable filter support culture. The degree of myotube maturation was assessed by the percentage of myotubes with more than three myonuclei per myotube.EOM- and LM-Fibro cells exhibited distinct morphologies. Both cell types proliferated as a monolayer and expressed vimentin. Fifty-five percent (SD 4.4%) of EOM-Fibro were Thy-1 positive compared with only 24% (SD 4.4%) of LM-Fibro. DNA microarray analysis demonstrated differential expression of structural, immune response, and metabolism-related genes between EOM- and LM-Fibro. Co-cultures demonstrated that mature myotube formation in EOM-derived cell lines was supported to a greater extent by EOM-Fibro than by LM-Fibro, compared with CL-EOM grown with LM-Fibro.Fibroblasts from EOM demonstrate distinct properties that distinguish them from leg muscle-derived fibroblasts. The distinct properties of EOM-Fibro may support the unique EOM phenotype and contribute to their differential involvement in disease.

SUBMITTER: Kusner LL

PROVIDER: S-EPMC2869047 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Perimysial fibroblasts of extraocular muscle, as unique as the muscle fibers.

Kusner Linda L LL Young Andrew A Tjoe Steven S Leahy Patrick P Kaminski Henry J HJ

Investigative ophthalmology & visual science 20090806 1

<h4>Purpose</h4>Extraocular muscle (EOM) has a distinct skeletal muscle phenotype. The hypothesis for the study was that fibroblasts support the unique EOM phenotype and that perimysial fibroblasts derived from EOM have properties that distinguish them from fibroblasts derived from other skeletal muscle.<h4>Methods</h4>Perimysial fibroblasts from leg muscle (LM-Fibro) and EOM (EOM-Fibro) of mice were derived and maintained in culture. EOM- and LM-Fibro were assessed morphologically and for vimen ...[more]

PMID: 19661226

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Project description:Each rectus extraocular muscle in cetaceans divides into two portions: a massive palpebral belly that inserts into the deep surface of the eyelids and a smaller scleral belly that inserts onto the eyeball. While the cetacean palpebral insertions have long been recognized, their homologies and functions remain unclear. To compare cetacean rectus EOM insertions with the global and orbital rectus EOM insertions of other mammals we dissected orbital contents of 20 odontocete species, 2 mysticete species and 18 non-cetacean species, both aquatic and terrestrial. Four cetacean species were also examined with magnetic resonance imaging (MRI). All four rectus muscles in cetaceans had well-developed palpebral bellies and insertions. Adjacent palpebral bellies showed varying degrees of fusion, from near independence to near complete fusion. Fusion was most complete towards palpebral insertions and less towards origins. A medial moiety of the superior rectus palpebral belly is likely the levator palpebrae superioris. Smaller but still robust scleral insertions were present on all recti, with the medial rectus (MR) being significantly more muscular than the others. All non-cetacean species examined had recti with distinct global and orbital insertions, the latter generally onto Tenon's capsule. Orbital insertions in pygmy hippopotamus and Florida manatee extended into the deep surfaces of the eyelids, hence qualifying as palpebral insertions. Our results suggest that rectus EOMs of mammals generally have both global and orbital insertions, and that palpebral bellies of cetaceans and other species are modified homologs of the orbital insertions. The presence of palpebral insertions in pygmy hippopotamus and absence in other cetartiodactyls suggests an intermediate condition between terrestrial cetartiodactyls and cetaceans. Palpebral insertions in Florida manatee and reports of their presence in some pinnipeds suggest parallel evolution in multiple aquatic lineages. Various functions of cetacean palpebral recti have been proposed, including eyelid dilators, protection during diving and thermogenesis for warming eye and brain. For further insight into their possible functions, we observed eye movements of captive bottlenose dolphins (Tursiops truncatus) at the U.S. National Aquarium. Our observations showed that in addition to rotation of the eyeball the entire surrounding palpebral region also moves during gaze changes. For example during upward gaze the globe not only rotates in supraduction but translates dorsally as well. It appears the rectus palpebral bellies are responsible for flexing the palpebral structures and thus also translating the globe, while the scleral insertions act directly for ocular rotation. Along with frequent non-conjugate eye movements, the oculomotor mechanics and repertoire of cetaceans are thus quite distinctive. Summarily, axial displacement within the orbit is a major 'eye movement' in cetaceans, with protrusion and retraction mediated by well-developed circular muscles and retractor bulbi respectively. Torsional eye movements driven by elaborate oblique EOMs are likewise significant. The roles of rectus EOMs for ocular rotation via their scleral insertions, especially the highly muscular MR, are for typical supra/infraductions and nasal/temporal ductions. The palpebral bellies accentuate these ductions by translating the globe and surrounding structures in the same direction.

Project description:PurposeThe purpose of this study was to characterize the injury response of extraocular muscles (EOMs) in adult zebrafish.MethodsAdult zebrafish underwent lateral rectus (LR) muscle myectomy surgery to remove 50% of the muscle, followed by molecular and cellular characterization of the tissue response to the injury.ResultsFollowing myectomy, the LR muscle regenerated an anatomically correct and functional muscle within 7 to 10 days post injury (DPI). Following injury, the residual muscle stump was replaced by a mesenchymal cell population that lost cell polarity and expressed mesenchymal markers. Next, a robust proliferative burst repopulated the area of the regenerating muscle. Regenerating cells expressed myod, identifying them as myoblasts. However, both immunofluorescence and electron microscopy failed to identify classic Pax7-positive satellite cells in control or injured EOMs. Instead, some proliferating nuclei were noted to express mef2c at the very earliest point in the proliferative burst, suggesting myonuclear reprogramming and dedifferentiation. Bromodeoxyuridine (BrdU) labeling of regenerating cells followed by a second myectomy without repeat labeling resulted in a twice-regenerated muscle broadly populated by BrdU-labeled nuclei with minimal apparent dilution of the BrdU signal. A double-pulse experiment using BrdU and 5-ethynyl-2'-deoxyuridine (EdU) identified double-labeled nuclei, confirming the shared progenitor lineage. Rapid regeneration occurred despite a cell cycle length of 19.1 hours, whereas 72% of the regenerating muscle nuclei entered the cell cycle by 48 hours post injury (HPI). Dextran lineage tracing revealed that residual myocytes were responsible for muscle regeneration.ConclusionsEOM regeneration in adult zebrafish occurs by dedifferentiation of residual myocytes involving a muscle-to-mesenchyme transition. A mechanistic understanding of myocyte reprogramming may facilitate novel approaches to the development of molecular tools for targeted therapeutic regeneration in skeletal muscle disorders and beyond.

Dataset Information

Perimysial fibroblasts of extraocular muscle, as unique as the muscle fibers.

Publications

Perimysial fibroblasts of extraocular muscle, as unique as the muscle fibers.

Similar Datasets

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