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Lv ST, Gao K, Choe HM, Jin ZY, Chang SY, Quan BH, Yin XJ. Effects of myostatin gene knockout on porcine extraocular muscles. Anim Biotechnol 2023; 34:2150-2158. [PMID: 35658834 DOI: 10.1080/10495398.2022.2077741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Myostatin (MSTN), a negative regulator of skeletal muscle mass, is not well known in extraocular muscles (EOMs). EOMs are specialized skeletal muscles. Hence, in this study, the effect of MSTN on the superior rectus (SR) and superior oblique (SO) of 2-month-old MSTN knockout (MSTN-/-) and wild-type (WT) pigs of the same genotype was investigated. SR (P < 0.01) and SO (P < 0.001) fiber cross-sectional areas of MSTN-/- pigs were significantly larger than those of WT pigs. Compared with WT pigs, MSTN-/- SO displayed a decrease in type I fibers (WT: 27.24%, MSTN-/-: 10.32%, P < 0.001). Type IIb fibers were higher in MSTN-/- pigs than in WT pigs (WT: 30.38%, MSTN-/-: 62.24%, P < 0.001). The trend in SR was the same as that in SO, although the trend in SO was greater than that in SR. The expression of myogenic differentiation factor (MyoD) and myogenic (MyoG) showed a significant increase in MSTN-/- SO (about 2.5-fold and 2-fold, respectively at the gene expression level, about 1.5-fold at the protein level) compared with WT pigs. MSTN plays an important role in the development of EOMs and regulates the muscle fiber type by modulating the gene expression of MyoD and MyoG in pigs.
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Affiliation(s)
- Si-Tong Lv
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Kai Gao
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Hak Myong Choe
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Zheng-Yun Jin
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Shuang-Yan Chang
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Biao-Hu Quan
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
| | - Xi-Jun Yin
- Jilin Provincial Key Laboratory of Transgenic Animal and Embryo Engineering, Yanbian University, Yanji, Jilin, China
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Rudell JC, Fleuriet J, Mustari MJ, McLoon LK. Childhood Onset Strabismus: A Neurotrophic Factor Hypothesis. J Binocul Vis Ocul Motil 2021; 71:35-40. [PMID: 33872122 PMCID: PMC8102408 DOI: 10.1080/2576117x.2021.1893585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 10/21/2022]
Abstract
Strabismus is a genetically heterogeneous disorder with complex molecular and neurophysiological causes. Evidence in the literature suggests a strong role for motor innervation in the etiology of strabismus, which connects central neural processes to the peripheral extraocular muscles. Current treatments of strabismus through surgery show that an inherent sensorimotor plasticity in the ocular motor system decreases the effectiveness of treatment, often driving eye alignment back toward its misaligned pre-surgical state by altering extraocular muscle tonus. There is recent interest in capitalizing on existing biological processes in extraocular muscles to overcome these compensatory mechanisms. Neurotrophins are trophic factors that regulate survival and development in neurons and muscle, including extraocular muscles. Local administration of neurotrophins to extraocular muscles partially reversed strabismus in an animal model of strabismus. The hypothesis is that sustained release of neurotrophins gives more time for the ocular motor system to adapt to a slow change in alignment in the desired direction. The effect of neurotrophins on extraocular muscles is complex, as different neurotrophic factors have diverse effects on extraocular muscle contraction profiles, patterns of innervation, and density of extraocular muscle precursor cells. Neurotrophic factors show promise as a therapeutic option for strabismus, which may help to improve treatment outcomes and offset devastating amblyopia and psychosocial effects of disease in strabismus patients.
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Affiliation(s)
- Jolene C Rudell
- Department of Ophthalmology, University California San Diego, San Diego, California
| | - Jérome Fleuriet
- Assistance Publique-Hôpitaux de Paris, Intensive Care Unit, Raymond Poincaré Hospital, Garches, France
| | - Michael J Mustari
- Washington National Primate Research Center, University of Washington, Seattle, Washington
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Linda K McLoon
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota
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Europa TA, Nel M, Heckmann JM. Gene expression profiling of orbital muscles in treatment-resistant ophthalmoplegic myasthenia gravis. Orphanet J Rare Dis 2020; 15:346. [PMID: 33308266 PMCID: PMC7731744 DOI: 10.1186/s13023-020-01629-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 11/27/2020] [Indexed: 12/12/2022] Open
Abstract
Background Unbiased in silico approaches applied to genome-wide data prioritized putative functional gene variants associating with treatment-resistant ophthalmoplegic myasthenia gravis (OP-MG). Although altered expression of genes harbouring these variants, or associated pathways, were shown in patient-derived transdifferentiated-myocyte models, gene expression in orbital-derived muscle was required to test the validity of the predictions.
Methods We sampled orbicularis oculi muscle (OOM) and one paralysed extraocular muscle (EOM) from six individuals with OP-MG during blepharoptosis and re-alignment surgeries, respectively. For controls, the OOMs were sampled from four individuals without myasthenia undergoing surgery for non-muscle causes of ptosis, and one non-paralysed EOM. Using a qPCR array, expression of 120 genes was compared between OP-MG and control OOMs, profiling putative “OP-MG” genes, genes in related biological pathways and genes reported to be dysregulated in MG cases or experimental MG models, and in EOMs of cases with strabismus. Normalization was performed with two stable reference genes. Differential gene expression was compared between OP-MG and control samples using the ΔΔCT method. Co-expression was analysed by pairwise correlation of gene transcripts to infer expression networks.
Results Overall, transcript levels were similar in OOMs and EOMs (p = 0.72). In OOMs, significant downregulated expression of eight genes was observed in OP-MG cases compared with controls (> twofold; p ≤ 0.016), including TFAM, a mitochondrial transcription factor, and genes related to the following pathways: atrophy signalling; muscle regeneration and contraction; glycogen synthesis; and extracellular matrix remodelling. Several microRNAs, known to be highly expressed in EOMs, are predicted to regulate some of these genes. Co-expression analyses of gene-pairs suggested high interconnectedness of gene expression networks in OP-MG muscle, but not controls (r > 0.96, p < 0.01). Significant inverse directions of gene-pair correlations were noted in OP-MG versus controls OOM networks (r ≥ 0.92, p < 0.001) involving most OP-MG genes overlapping prominently with muscle atrophy/contractility and oxidative metabolism genes. Conclusions The gene expression in orbital muscles derived from OP-MG individuals compared with normal controls, support the pathogenic hypothesis previously generated from whole genome sequence analyses. Repression of gene transcripts in OP-MG orbital muscle implicate tissue-specific regulatory mechanisms, which may inform future biomarker discovery approaches.
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Affiliation(s)
- Tarin A Europa
- Neurology Research Group, Division of Neurology, Department of Medicine, Faculty of Health Sciences, E8-74, New Groote Schuur Hospital, University of Cape Town, Cape Town, 7925, South Africa.,UCT Neuroscience Institute, Cape Town, South Africa
| | - Melissa Nel
- Neurology Research Group, Division of Neurology, Department of Medicine, Faculty of Health Sciences, E8-74, New Groote Schuur Hospital, University of Cape Town, Cape Town, 7925, South Africa.,UCT Neuroscience Institute, Cape Town, South Africa
| | - Jeannine M Heckmann
- Neurology Research Group, Division of Neurology, Department of Medicine, Faculty of Health Sciences, E8-74, New Groote Schuur Hospital, University of Cape Town, Cape Town, 7925, South Africa. .,UCT Neuroscience Institute, Cape Town, South Africa.
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Eye alignment changes caused by sustained GDNF treatment of an extraocular muscle in infant non-human primates. Sci Rep 2020; 10:11927. [PMID: 32681083 PMCID: PMC7368047 DOI: 10.1038/s41598-020-68743-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 06/04/2020] [Indexed: 12/16/2022] Open
Abstract
The ability of sustained treatment of a single extraocular muscle with glial cell line-derived neurotrophic factor (GDNF) to produce a strabismus in infant non-human primates was tested. Six infant non-human primates received a pellet containing GDNF, releasing 2 µg/day for 90 days, on one medial rectus muscle. Eye alignment was assessed up to 6 months. Five of the six animals showed a slow decrease in eye misalignment from the significant exotropia present at birth, ending with approximately 10° of exotropia. Controls became orthotropic. Misalignment averaged 8° three months after treatment ended. After sustained GDNF treatment, few changes were seen in mean myofiber cross-sectional areas compared to age-matched naïve controls. Neuromuscular junction number was unaltered in the medial rectus muscles, but were significantly reduced in the untreated lateral recti. Neuromuscular junctions on slow fibers became multiply innervated after this sustained GDNF treatment. Pitx2-positive cells significantly decreased in treated and contralateral medial rectus muscles. Our study suggests that balanced GDNF signaling plays a role in normal development and maintenance of orthotropia. Sustained GDNF treatment of one medial rectus muscle resulted in a measurable misalignment largely maintained 3 months after treatment ended. Structural changes suggest mechanisms for producing an imbalance in muscle function.
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Pullela M, Agaoglu MN, Joshi AC, Agaoglu S, Coats DK, Das VE. Neural Plasticity Following Surgical Correction of Strabismus in Monkeys. Invest Ophthalmol Vis Sci 2019; 59:5011-5021. [PMID: 30326068 PMCID: PMC6188463 DOI: 10.1167/iovs.18-25245] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Purpose Although widely practiced, surgical treatment of strabismus has varying levels of success and permanence. In this study we investigated adaptive responses within the brain and the extraocular muscles (EOM) that occur following surgery and therefore determine long-term success of the treatment. Methods Single cell responses were collected from cells in the oculomotor and abducens nuclei before and after two monkeys (M1, M2) with exotropia (divergent strabismus) underwent a strabismus correction surgery that involved weakening of the lateral rectus (LR) and strengthening of the medial rectus (MR) muscle of one eye. Eye movement and neuronal data were collected for up to 10 months after surgery during a monocular viewing smooth-pursuit task. These data were fit with a first-order equation and resulting coefficients were used to estimate the population neuronal drive (ND) to each EOM of both eyes. Results Surgery resulted in a ∼70% reduction in strabismus angle in both animals that reverted toward presurgical misalignment by approximately 6 months after treatment. In the first month after surgery, the ND to the treated MR reduced in one animal and ND to the LR increased in the other animal, both indicating active neural plasticity that reduced the effectiveness of the treatment. Adaptive changes in ND to the untreated eye were also identified. Conclusions Active neural and muscle plasticity corresponding to both the treated and the untreated eye determines longitudinal success following surgical correction of strabismus. Outcome of surgical treatment could be improved by identifying ways to enhance “positive” adaptation and limit “negative” adaptation.
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Affiliation(s)
- Mythri Pullela
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Mehmet N Agaoglu
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Anand C Joshi
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Sevda Agaoglu
- College of Optometry, University of Houston, Houston, Texas, United States
| | - David K Coats
- Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, United States
| | - Vallabh E Das
- College of Optometry, University of Houston, Houston, Texas, United States
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Europa TA, Nel M, Heckmann JM. A review of the histopathological findings in myasthenia gravis: Clues to the pathogenesis of treatment-resistance in extraocular muscles. Neuromuscul Disord 2019; 29:381-387. [PMID: 31029532 DOI: 10.1016/j.nmd.2019.03.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/18/2019] [Accepted: 03/20/2019] [Indexed: 12/28/2022]
Abstract
In myasthenia gravis autoantibodies target components of the neuromuscular junction causing variable degrees of weakness. In most cases, autoantibodies trigger complement-mediated endplate damage and extraocular muscles may be most susceptible. A proportion of MG cases develop treatment-resistant ophthalmoplegia. We reviewed publications spanning 65 years reporting the histopathological findings in the muscles and extraocular muscles of myasthenic patients to determine whether pathological changes in extraocular muscles differ from non-ocular muscles. As extraocular muscles represent a unique muscle allotype we also compared their histopathology in myasthenia to those in strabismus. We found that in myasthenia gravis, the non-ocular muscles frequently demonstrate neurogenic changes regardless of myasthenic serotype. Mitochondrial stress/damage was also frequent in myasthenic muscles and possibly more evident in muscle-specific kinase antibody-positive MG. Although myasthenia-associated paralysed extraocular muscles demonstrated prominent fibro-fatty replacement and mitochondrial alterations, these features appeared commonly in paralysed extraocular muscles of any cause. We postulate that extraocular muscles may be more susceptible than limb muscles to poor contractility as a consequence of myasthenia, resulting in a cascade of atrophy signaling pathways and altered mitochondrial homeostasis which contribute to the tipping point in developing treatment-resistant myasthenic ophthalmoplegia. Early strategies to improve force generation in extraocular muscles are critical.
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Affiliation(s)
- Tarin A Europa
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Melissa Nel
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Jeannine M Heckmann
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa; Neurology Division, Department of Medicine, University of Cape Town, Cape Town, South Africa.
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Zhi JJ, Yan H, Sun LH. Establishment of an acute extraocular muscle injury model in cats. Int J Ophthalmol 2018; 11:1475-1481. [PMID: 30225221 PMCID: PMC6133886 DOI: 10.18240/ijo.2018.09.08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 05/07/2018] [Indexed: 11/23/2022] Open
Abstract
AIM To describe an acute extraocular muscle injury model in cats. METHODS Seventy-two cats were randomly divided into 6 groups (12 cats per group). Cats' left lateral recti were clamped using a surgical needle holder with a clamping strength of 2 (Groups A and D), 4 (Groups B and E) and 6 kg (Groups C and F). The right lateral recti were treated as controls. On the 4th and 7th days, hematoxylin eosin (HE) staining, immunohistochemical staining for proliferating cell nuclear antigen (PCNA), muscle force measurements and ocular alignment changes were performed to evaluate the extent of injuries. RESULTS The morphological changes were graded as mild, moderate or severe by HE staining in all experiment groups. PCNA immunohistochemical staining indicated repairment of muscle fibers in the damaged area. On the 4th and 7th days after clamping, the injured lateral muscle exhibited an elevated threshold for electric stimulation. The muscle forces among groups 2, 4 and 6 kg injury at 4d (Groups A, B and C) were statistically significant (P<0.05), but no significant differences were noted among groups 2, 4 and 6 kg injury at 7d (Groups D, E and F) (P>0.05), respectively. In addition, medial deviation in ocular alignment was also present to various degrees in all groups. CONCLUSION A cat model of acute extraocular muscle injury can be established by rectus clamping. Different clamping strengths can make different degrees of muscle injury. This model may help the future study in the acute extraocular muscle injury.
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Affiliation(s)
- Jun-Jie Zhi
- Department of Ophthalmology, Xi'an No. 4 Hospital, Shaanxi Eye Hospital, Affiliated Guangren Hospital School of Medicine, Xi'an Jiaotong University, Xi'an 710004, Shaanxi Province, China
- Department of Ophthalmology, No. 422 Hospital of PLA, Zhanjiang 524009, Guangdong Province, China
| | - Hong Yan
- Department of Ophthalmology, Xi'an No. 4 Hospital, Shaanxi Eye Hospital, Affiliated Guangren Hospital School of Medicine, Xi'an Jiaotong University, Xi'an 710004, Shaanxi Province, China
- Department of Ophthalmology, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, Shaanxi Province, China
| | - Li-Hua Sun
- Department of Ophthalmology, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, Shaanxi Province, China
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Fitzpatrick KR, Cucak A, McLoon LK. Changing muscle function with sustained glial derived neurotrophic factor treatment of rabbit extraocular muscle. PLoS One 2018; 13:e0202861. [PMID: 30142211 PMCID: PMC6108505 DOI: 10.1371/journal.pone.0202861] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 08/10/2018] [Indexed: 01/05/2023] Open
Abstract
Recent microarray and RNAseq experiments provided evidence that glial derived neurotrophic factor (GDNF) levels were decreased in extraocular muscles from human strabismic subjects compared to age-matched controls. We assessed the effect of sustained GDNF treatment of the superior rectus muscles of rabbits on their physiological and morphological characteristics, and these were compared to naïve control muscles. Superior rectus muscles of rabbits were implanted with a sustained release pellet of GDNF to deliver 2μg/day, with the contralateral side receiving a placebo pellet. After one month, the muscles were assessed using in vitro physiological methods. The muscles were examined histologically for alteration in fiber size, myosin expression patterns, neuromuscular junction size, and stem cell numbers and compared to age-matched naïve control muscles. GDNF resulted in decreased force generation, which was also seen on the untreated contralateral superior rectus muscles. Muscle relaxation times were increased in the GDNF treated muscles. Myofiber mean cross-sectional areas were increased after the GDNF treatment, but there was a compensatory increase in expression of developmental, neonatal, and slow tonic myosin heavy chain isoforms. In addition, in the GDNF treated muscles there was a large increase in Pitx2-positive myogenic precursor cells. One month of GDNF resulted in significant extraocular muscle adaptation. These changes are interesting relative to the decreased levels of GDNF in the muscles from subjects with strabismus and preliminary data in infant non-human primates where sustained GDNF treatment produced a strabismus. These data support the view that GDNF has the potential for improving eye alignment in subjects with strabismus.
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Affiliation(s)
- Krysta R. Fitzpatrick
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Anja Cucak
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Linda K. McLoon
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States of America
- Department of Ophthalmology and Visual Neurosciences and Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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Agarwal AB, Feng CY, Altick AL, Quilici DR, Wen D, Johnson LA, von Bartheld CS. Altered Protein Composition and Gene Expression in Strabismic Human Extraocular Muscles and Tendons. Invest Ophthalmol Vis Sci 2017; 57:5576-5585. [PMID: 27768799 PMCID: PMC5080916 DOI: 10.1167/iovs.16-20294] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Purpose To determine whether structural protein composition and expression of key regulatory genes are altered in strabismic human extraocular muscles. Methods Samples from strabismic horizontal extraocular muscles were obtained during strabismus surgery and compared with normal muscles from organ donors. We used proteomics, standard and customized PCR arrays, and microarrays to identify changes in major structural proteins and changes in gene expression. We focused on muscle and connective tissue and its control by enzymes, growth factors, and cytokines. Results Strabismic muscles showed downregulation of myosins, tropomyosins, troponins, and titin. Expression of collagens and regulators of collagen synthesis and degradation, the collagenase matrix metalloproteinase (MMP)2 and its inhibitors, tissue inhibitor of metalloproteinase (TIMP)1 and TIMP2, was upregulated, along with tumor necrosis factor (TNF), TNF receptors, and connective tissue growth factor (CTGF), as well as proteoglycans. Growth factors controlling extracellular matrix (ECM) were also upregulated. Among 410 signaling genes examined by PCR arrays, molecules with downregulation in the strabismic phenotype included GDNF, NRG1, and PAX7; CTGF, CXCR4, NPY1R, TNF, NTRK1, and NTRK2 were upregulated. Signaling molecules known to control extraocular muscle plasticity were predominantly expressed in the tendon rather than the muscle component. The two horizontal muscles, medial and lateral rectus, displayed similar changes in protein and gene expression, and no obvious effect of age. Conclusions Quantification of proteins and gene expression showed significant differences in the composition of extraocular muscles of strabismic patients with respect to important motor proteins, elements of the ECM, and connective tissue. Therefore, our study supports the emerging view that the molecular composition of strabismic muscles is substantially altered.
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Affiliation(s)
- Andrea B Agarwal
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - Cheng-Yuan Feng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - Amy L Altick
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
| | - David R Quilici
- Mick Hitchcock Nevada Proteomics Center, University of Nevada, Reno, Nevada, United States
| | - Dan Wen
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, China
| | - L Alan Johnson
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States 4Sierra Eye Associates, Reno, Nevada, United States
| | - Christopher S von Bartheld
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, United States
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Willoughby CL, Ralles S, Christiansen SP, McLoon LK. Effects of sequential injections of hepatocyte growth factor and insulin-like growth factor-I on adult rabbit extraocular muscle. J AAPOS 2012; 16:354-60. [PMID: 22929450 PMCID: PMC3431511 DOI: 10.1016/j.jaapos.2012.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/22/2012] [Accepted: 05/23/2012] [Indexed: 12/26/2022]
Abstract
PURPOSE To determine whether hepatocyte growth factor (HGF) and insulin-like growth factor-I (IGF-I) have synergistic effects in promoting extraocular muscle fiber growth and force generation. METHODS A superior rectus muscle of adult rabbits was treated with either a single injection of HGF or sequential injections of HGF followed 1 week later by IGF-I. One week after HGF alone and 1 week after the IGF-I injection, the superior rectus muscles from treated and control orbits were examined for alterations in force generation as well as changes in myofiber size. RESULTS Injection of HGF alone did not result in changes to muscle force, specific tension, or myofiber cross-sectional area; however, it did result in a significant increase in numbers of satellite cells. Sequential injection of HGF and IGF-I resulted in significantly increased force, specific tension, and myofiber cross-sectional areas as well as increased numbers of satellite cells. CONCLUSIONS Preinjection with HGF augments the treatment effect of IGF-I. This synergistic effect is likely a result of HGF-induced activation of satellite cells and should allow a reduction in IGF-I dosing required to produce a given increase in extraocular muscle force generation.
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Feng CY, von Bartheld CS. Expression of insulin-like growth factor 1 isoforms in the rabbit oculomotor system. Growth Horm IGF Res 2011; 21:228-232. [PMID: 21703892 PMCID: PMC3140565 DOI: 10.1016/j.ghir.2011.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 06/03/2011] [Accepted: 06/04/2011] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The insulin-like growth factor-1 (IGF-1) gene encodes two isoforms, IGF-1Ea and IGF-1Eb. Both isoforms can regulate skeletal muscle growth and strength. It has been suggested that IGF-Eb may be more potent in promoting skeletal muscle hypertrophy. Precise contractile force regulation is particularly important in the oculomotor system. However, expression of these isoforms in mammalian extraocular muscles (EOMs) is unknown. Here, we examined their expression in rabbit EOMs and the innervating nerve, two potential sources for myogenic growth factors, and compared isoform expression between EOMs and limb skeletal muscles. DESIGN Expression of IGF-1 isoforms was quantified by real-time RT-PCR in adult rabbit EOMs, trochlear and ophthalmic nerves, and compared with expression in rabbit limb skeletal muscles. The presence of mature IGF-1 peptide in the muscles was further examined by Western blot. RESULTS Both IGF-1Ea and IGF-1Eb were expressed in the EOM and the trochlear nerve. Both isoforms were expressed at significantly higher levels (9-fold) in EOM than in limb skeletal muscle. Transcripts of IGF-1 isoforms, of IGF-1 receptor and of IGF binding proteins showed a gradient distribution along the EOM from proximal to distal. The mature IGF-1 protein showed the same gradient distribution in the EOM. CONCLUSIONS Expression of relatively abundant amounts of both IGF-1 splicing isoforms in EOMs, and at a significantly higher level than in limb skeletal muscle, underscores the potential relevance of these myogenic growth factors in EOM plasticity and force regulation.
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Affiliation(s)
- Cheng-Yuan Feng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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McLoon LK, Park HN, Kim JH, Pedrosa-Domellöf F, Thompson LV. A continuum of myofibers in adult rabbit extraocular muscle: force, shortening velocity, and patterns of myosin heavy chain colocalization. J Appl Physiol (1985) 2011; 111:1178-89. [PMID: 21778415 DOI: 10.1152/japplphysiol.00368.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extraocular muscle (EOM) myofibers do not fit the traditional fiber typing classifications normally used in noncranial skeletal muscle, in part, due to the complexity of their individual myofibers. With single skinned myofibers isolated from rectus muscles of normal adult rabbits, force and shortening velocity were determined for 220 fibers. Each fiber was examined for myosin heavy chain (MyHC) isoform composition by densitometric analysis of electrophoresis gels. Rectus muscle serial sections were examined for coexpression of eight MyHC isoforms. A continuum was seen in single myofiber shortening velocities as well as force generation, both in absolute force (g) and specific tension (kN/m(2)). Shortening velocity correlated with MyHCIIB, IIA, and I content, the more abundant MyHC isoforms expressed within individual myofibers. Importantly, single fibers with similar or identical shortening velocities expressed significantly different ratios of MyHC isoforms. The vast majority of myofibers in both the orbital and global layers expressed more than one MyHC isoform, with up to six isoforms in single fiber segments. MyHC expression varied significantly and unpredictably along the length of single myofibers. Thus EOM myofibers represent a continuum in their histological and physiological characteristics. This continuum would facilitate fine motor control of eye position, speed, and direction of movement in all positions of gaze and with all types of eye movements-from slow vergence movements to fast saccades. To fully understand how the brain controls eye position and movements, it is critical that this significant EOM myofiber heterogeneity be integrated into hypotheses of oculomotor control.
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Affiliation(s)
- Linda K McLoon
- Dept. of Ophthalmology, Univ. of Minnesota, Minneapolis, MN 55455, USA.
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Anderson BC, Daniel ML, Kendall JD, Christiansen SP, McLoon LK. Sustained release of bone morphogenetic protein-4 in adult rabbit extraocular muscle results in decreased force and muscle size: potential for strabismus treatment. Invest Ophthalmol Vis Sci 2011; 52:4021-9. [PMID: 21357389 DOI: 10.1167/iovs.10-6878] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose. To assess the effect of a sustained-release preparation of bone morphogenetic protein-4 (BMP-4) on EOM force generation and muscle size. Methods. Sustained-release pellets, releasing 500 nanograms/day of BMP-4 for a maximum of 3 months, were implanted beneath the superior rectus muscle (SR) belly in anesthetized adult rabbits. The contralateral side received a placebo pellet as a control. After 1, 3, and 6 months, SRs were removed, and force generation at twitch and tetanic frequencies as well as fatigue resistance were determined in vitro. Myofiber size, myosin heavy chain isoform expression, and satellite cell density were assessed histologically. Results. SR force generation was significantly decreased by BMP-4 compared with the contralateral controls. Force generation was decreased by 25-30% by 1 month, 31-50% by 3 months, and at 6 months, after 3 BMP-4-free months, force was still decreased by 20-31%. No change in fatigue was seen. Significant decreases in muscle size were seen, greatest at 3 months. At all time points Pax7- and MyoD-positive satellite cell densities were significantly decreased. Conclusions. The decreased force generation and muscle size caused by sustained release of BMP-4 suggests that myogenic signaling factors may provide a more biological method of decreasing muscle strength in vivo than exogenously administered toxins. Treating antagonist-agonist pairs of EOM with titratable, naturally occurring myogenic signaling and growth factors may provide safe, efficacious, nonsurgical treatment options for patients with strabismus.
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Affiliation(s)
- Brian C Anderson
- Departments of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, USA
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Current world literature. Curr Opin Ophthalmol 2008; 19:435-43. [PMID: 18772678 DOI: 10.1097/icu.0b013e32830d5da2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Campos EC. Why do the eyes cross? A review and discussion of the nature and origin of essential infantile esotropia, microstrabismus, accommodative esotropia, and acute comitant esotropia. J AAPOS 2008; 12:326-31. [PMID: 18550403 DOI: 10.1016/j.jaapos.2008.03.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 03/24/2008] [Accepted: 03/24/2008] [Indexed: 11/20/2022]
Abstract
PURPOSE To try to explain the long-term stability of bilateral medial rectus botulinum toxin (botox) chemo-denervation in essential infantile esotropia; to evaluate divergent fusion amplitude in accommodative esotropia and acute comitant esotropia of emmetropes; to look for accommodation anomalies in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes; and to discuss characteristics of microstrabismus. METHODS Retrospective analysis of 61 essential infantile esotropia patients with early treatment with one botox injection in both medial rectus; measurement of divergent fusion amplitude in accommodative esotropia and acute comitant esotropia; measurement of Near point of accommodation in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes. RESULTS Stable results were found in 85.24% of essential infantile esotropia treated patients; reduced divergent fusion amplitude was detected in accommodative esotropia and acute comitant esotropia; hypo-accommodation was found in some patients with high AC/A ratio accommodative esotropia and a convergence spasm in acute comitant esotropia of myopes. CONCLUSIONS Very early botox treatment probably eradicates the effect of an excessive convergence tonus in essential infantile esotropia. A prevention of accommodative esotropia with full retinoscopic correction is only mandatory with a significantly reduced amplitude of fusional divergence. A deficit in accommodation should be looked for in high AC/A ratio accommodative esotropia, before bifocal lenses prescription. Early diagnosed acute comitant esotropia of myopic patients can be treated as a convergence spasm. Only surgery treats acute comitant esotropia, in patients with emmetropia or moderate hypermetropia.
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Affiliation(s)
- Emilio C Campos
- Professor of Ophthalmology, University of Bologna, Bologna, Italy; Chief of Ophthalmology, St. Orsola-Malpighi Teaching Hospital, Bologna, Italy
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