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Analysis of Neurotrophic Factors in Limb and Extraocular Muscles of Mouse Model of Amyotrophic Lateral Sclerosis
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Paediatrics.
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
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2014 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 9, no 10, e109833Article in journal (Refereed) Published
Abstract [en]

Amyotrophic lateral sclerosis (ALS) is currently an incurable fatal motor neuron syndrome characterized by progressive weakness, muscle wasting and death ensuing 3–5 years after diagnosis. Neurotrophic factors (NTFs) are known to be important in both nervous system development and maintenance. However, the attempt to translate the potential of NTFs into the therapeutic options remains limited despite substantial number of approaches, which have been tested clinically. Using quantitative RT-PCR (qRT-PCR) technique, the present study investigated mRNA expression of four different NTFs: brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4/5 (NT-4) and glial cell line-derived neurotrophic factor (GDNF) in limb muscles and extraocular muscles (EOMs) from SOD1G93A transgenic mice at early and terminal stages of ALS. General morphological examination revealed that muscle fibres were well preserved in both limb muscles and EOMs in early stage ALS mice. However, in terminal ALS mice, most muscle fibres were either atrophied or hypertrophied in limb muscles but unaffected in EOMs. qRT-PCR analysis showed that in early stage ALS mice, NT-4 was significantly down-regulated in limb muscles whereas NT-3 and GDNF were markedly up-regulated in EOMs. In terminal ALS mice, only GDNF was significantly up-regulated in limb muscles. We concluded that the early down-regulation of NT-4 in limb muscles is closely associated with muscle dystrophy and dysfunction at late stage, whereas the early up-regulations of GDNF and NT-3 in EOMs are closely associated with the relatively well-preserved muscle morphology at late stage. Collectively, the data suggested that comparing NTFs expression between limb muscles and EOMs from different stages of ALS animal models is a useful method in revealing the patho-physiology and progression of ALS, and eventually rescuing motor neuron in ALS patients.

Place, publisher, year, edition, pages
2014. Vol. 9, no 10, e109833
Keyword [en]
neurotrophins, neurotrophic factor, limb muscles, extraocular muscles, ALS
National Category
Cell and Molecular Biology
Research subject
Medical Cell Biology
URN: urn:nbn:se:umu:diva-96545DOI: 10.1371/journal.pone.0109833ISI: 000346766200057OAI: diva2:765208
Available from: 2014-11-21 Created: 2014-11-21 Last updated: 2016-05-16Bibliographically approved
In thesis
1. A Muscle Perspective on the Pathophysiology of Amyotrophic Lateral Sclerosis: Differences between extraocular and limb muscles
Open this publication in new window or tab >>A Muscle Perspective on the Pathophysiology of Amyotrophic Lateral Sclerosis: Differences between extraocular and limb muscles
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Amyotrophic lateral sclerosis (ALS) is a late-onset progressive neurodegenerative disorder. ALS has been traditionally believed to be primarily a motor neuron disease. However, accumulating data indicate that loss of contact between the axons and the muscle fibres occurs early; long before the death of motor neurons and that muscle fibres may initiate motor neuron degeneration. Thus, the view of ALS is changing focus from motor neurons alone to also include the muscle fibres and the neuromuscular junctions (NMJs). While skeletal muscles are affected in ALS, oculomotor disturbances are not dominant features of this disease and extraocular muscles (EOMs) are far less affected than limb muscles. Why oculomotor neurons and EOMs are capable to be more resistant in the pathogenetic process of ALS is still unknown.

The overall goal of this thesis is to explore the pathophysiology of ALS from a muscle perspective and in particular study the expression and distribution of key neurotrophic factors (NTFs) and Wnt proteins in EOMs and limb muscles from ALS donors and from SOD1G93A transgenic mice. Comparisons were made with age-matched controls to distinguish between changes related to ALS and to ageing.

Results: Brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4) were present in EOMs and limb muscles at both mRNA and protein levels in control mice. The mRNA levels of BDNF, NT-3 and NT-4 were significantly lower in EOMs than in limb muscles of early and/or late control mice, indicating an intrinsic difference in NTFs expression between EOMs and limb muscles. qRT-PCR analysis showed significantly upregulated mRNA levels of NT-3 and GDNF in EOMs but significantly downregulated mRNA levels of NT-4 in limb muscles from SOD1G93A transgenic mice at early stage. The NTFs were detected immunohistochemically in NMJs, nerve axons and muscle fibres. The expression of BDNF, GDNF and NT-4 on NMJs of limb muscles, but not of EOMs, was significantly decreased in terminal stage ALS animals as compared to the limb muscles of the age-matched controls. In contrast, NTFs expression in intramuscular nerve axons did not present significant changes in either muscle group of early or late ALS mice. NTFs, especially BDNF and NT-4 were upregulated in some small-sized muscle fibres in limb muscles of late stage ALS mice. All the four Wnt isoforms, Wnt1, Wnt3a, Wnt5a and Wnt7a were detected in most axon profiles in all human EOMs with ALS, whereas significantly fewer axon profiles were positive in the human limb muscles except for Wnt5a. Similar differential patterns were found in myofibres, except for Wnt7a, where its expression was elevated within sarcolemma of limb muscle fibres. β-catenin, a marker of the canonical Wnt pathway was activated in a subset of myofibres in the EOMs and limb muscle in all ALS patients. In the SOD1G93A mouse, all four Wnt isoforms were significantly decreased in the NMJs at the terminal stage compared to age matched controls.

Conclusions: There were clear differences in NTF and Wnt expression patterns between EOM and limb muscle, suggesting that they may play a role in the distinct susceptibility of these two muscle groups to ALS. In particular, the early upregulation of GDNF and NT-3 in the EOMs might play a role in the preservation of the EOMs in ALS. Further studies are needed to determine whether these proteins and the pathways they control may be have a future potential as protecting agents for other muscles.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2016. 92 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1803
Neuromuscular junctions, Extraocular muscles, Skeletal muscle, Neurotrophic factor, Wnt, Motor neuron disease, Amyotrophic lateral sclerosis, SOD1G93A mice
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Research subject
Molecular Biology
urn:nbn:se:umu:diva-120219 (URN)978-91-7601-445-5 (ISBN)
Public defence
2016-06-08, KB3B1 (149), KBC-huset, KBC house, Umeå University, Umeå, 09:00 (English)
Available from: 2016-05-18 Created: 2016-05-11 Last updated: 2016-05-26Bibliographically approved

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