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Investigation of the Expression of Myogenic Transcription Factors, microRNAs and Muscle-Specific E3 Ubiquitin Ligases in the Medial Gastrocnemius and Soleus Muscles following Peripheral Nerve Injury
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Anatomi. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Handkirurgi.
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Anatomi. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Handkirurgi.
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Anatomi.
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Anatomi.
2015 (engelsk)Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 12, artikkel-id e0142699Artikkel i tidsskrift (Fagfellevurdert) Published
Resurstyp
Text
Abstract [en]

Despite surgical innovation, the sensory and motor outcome after a peripheral nerve injury remains incomplete. One contributing factor to the poor outcome is prolonged denervation of the target organ, leading to apoptosis of both mature myofibres and satellite cells with subsequent replacement of the muscle tissue with fibrotic scar and adipose tissue. In this study, we investigated the expression of myogenic transcription factors, muscle specific microRNAs and muscle-specific E3 ubiquitin ligases at several time points following denervation in two different muscles, the gastrocnemius (containing predominantly fast type fibres) and soleus (slow type) muscles, since these molecules may influence the degree of atrophy following denervation. Both muscles exhibited significant atrophy (compared with the contra-lateral sides) at 7 days following either a nerve transection or crush injury. In the crush model, the soleus muscle showed significantly increased muscle weights at days 14 and 28 which was not the case for the gastrocnemius muscle which continued to atrophy. There was a significantly more pronounced up-regulation of MyoD expression in the denervated soleus muscle compared with the gastrocnemius muscle. Conversely, myogenin was more markedly elevated in the gastrocnemius versus soleus muscles. The muscles also showed significantly contrasting transcriptional regulation of the microRNAs miR-1 and miR-206. MuRF1 and Atrogin-1 showed the highest levels of expression in the denervated gastrocnemius muscle. This study provides further insights regarding the intracellular regulatory molecules that generate and maintain distinct patterns of gene expression in different fibre types following peripheral nerve injury.

sted, utgiver, år, opplag, sider
San Francisco: Public Library Science , 2015. Vol. 10, nr 12, artikkel-id e0142699
HSV kategori
Identifikatorer
URN: urn:nbn:se:umu:diva-114579DOI: 10.1371/journal.pone.0142699ISI: 000367092300002PubMedID: 26691660OAI: oai:DiVA.org:umu-114579DiVA, id: diva2:903622
Tilgjengelig fra: 2016-02-16 Laget: 2016-01-25 Sist oppdatert: 2018-06-07bibliografisk kontrollert
Inngår i avhandling
1. An exploration of the mechanisms behind peripheral nerve injury
Åpne denne publikasjonen i ny fane eller vindu >>An exploration of the mechanisms behind peripheral nerve injury
2016 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Despite surgical innovation, the sensory and motor outcome after peripheral nerve injury is incomplete. In this thesis, the biological pathways potentially responsible for the poor functional recoveries were investigated in both the distal nerve stump/target organ, spinal motoneurons and dorsal root ganglia (DRG). The effect of delayed nerve repair was determined in a rat sciatic nerve transection model. There was a dramatic decline in the number of regenerating motoneurons and myelinated axons found in the distal nerve stumps of animals undergoing nerve repair after a delay of 3 and 6 months. RT-PCR of the distal nerve stumps showed a decline in expression of Schwann cells (SC) markers, with a progressive increase in fibrotic and proteoglycan scar markers, with increased delayed repair time. Furthermore, the yield of SC which could be isolated from the distal nerve segments progressively fell with increased delay in repair time. Consistent with the impaired distal nerve stumps the target medial gastrocnemius (MG) muscles at 3- and 6-months delayed repair were atrophied with significant declines in wet weights (61% and 27% compared with contralateral sides). The role of myogenic transcription factors, muscle specific microRNAs and musclespecific E3 ubiquitin ligases in the muscle atrophy was investigated in both gastrocnemius and soleus muscles following either crush or nerve transection injury. In the crush injury model, the soleus muscle showed significantly increased recovery in wet weight at days 14 and 28 (compared with day 7) which was not the case for the gastrocnemius muscle which continued to atrophy. There was a significantly more pronounced up-regulation of MyoD expression in the denervated soleus muscle compared with the gastrocnemius muscle. Conversely, myogenin was more markedly elevated in the gastrocnemius versus soleus muscles. The muscles also showed significantly contrasting transcriptional regulation of the microRNAs miR-1 and miR-206. MuRF1 and Atrogin-1 showed the highest levels of expression in the denervated gastrocnemius muscle. Morphological and molecular changes in spinal motoneurons were compared after L4-L5 ventral root avulsion (VRA) and distal peripheral nerve axotomy (PNA). Neuronal degeneration was indicated by decreased immunostaining for microtubule-associated protein-2 in dendrites and synaptophysin in presynaptic boutons after both VRA and PNA. Immunostaining for ED1-reactive microglia and GFAPpositive astrocytes was significantly elevated in all experimental groups. qRT-PCR analysis and Western blotting of the ventral horn from L4-L5 spinal cord segments revealed a significant upregulation of apoptotic cell death mediators including caspases-3 and -8 and a range of related death receptors following VRA. In contrast, following PNA, only caspase-8 was moderately upregulated. The mechanisms of primary sensory neuron degeneration were also investigated in the DRG following peripheral nerve axotomy, where several apoptotic pathways including those involving the endoplasmic reticulum were shown to be upregulated. In summary, these results show that the critical time point after which the outcome of regeneration becomes too poor appears to be 3-months. Both proximal and distal injury affect spinal motoneurons morphologically, but VRA induces motoneuron degeneration mediated through both intrinsic and extrinsic apoptotic pathways. Primary sensory neuron degeneration involves several different apoptotic pathways, including the endoplasmic reticulum.

sted, utgiver, år, opplag, sider
Umeå: Umeå University, 2016. s. 53
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 1853
Emneord
Peripheral nerve injury, target organ, spinal motoneurons, primary sensory neurons, degeneration
HSV kategori
Forskningsprogram
anatomi
Identifikatorer
urn:nbn:se:umu:diva-127357 (URN)978-91-7601-591-9 (ISBN)
Disputas
2016-12-02, Sal KB3A9, KBC-huset, Umeå, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2016-11-11 Laget: 2016-11-09 Sist oppdatert: 2018-06-09bibliografisk kontrollert

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