The role of microRNAs in muscle wasting during ageing and disease
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2023-05-23Author
Sannicandro, Anthony J.
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Abstract
Sarcopenia is age-related muscle loss and management is complex. The mechanisms
underpinning age-related decline in muscle health include defective muscle
regeneration and deterioration of neuromuscular junctions. microRNAs are small,
non-coding RNAs that regulate expression of genes and are implicated in the
regulation of muscle. Using bioinformatics and small RNA-seq from human
myoblasts, we detected miR-199a-5p to be upregulated in age and was predicted to
regulate genes associated with sarcopenia. Therefore, we used C2C12 cells as
myogenic model and NSC-34 cells as a neuron-like model in vitro, and adult and old
C57BL/6 mice (adult 5-6 months, old 23-24 months) in vivo to determine the effect
of miR-199a-5p overexpression and inhibition on muscle. Our data, in vitro,
indicated the negative role of miR-199a-5p on myogenic differentiation and myotube
size of C2C12 cells. Inhibition of miR-199a-5p in C2C12 also partially restored
myotube atrophy resulting from tunicamycin-induced stress of myotubes and
increased mitochondrial activity. We found ER stress protein GRP78 upregulated
with miR-199a-5p overexpression in vitro. We also observed neuronal growth
protein GAP43 to be differentially expressed in vitro with miR-199a-5p
overexpression. Luciferase assay identified these as likely targets of miR-199a-5p.
We found, in vivo, that miR-199a-5p inhibition did not significantly affect muscle
size but did improve muscle force. We examined the neuromuscular junction and
found miR-199a-5p overexpression contributed towards increased instance of
abnormal morphology and fragmentation, and with miR-199a-5p inhibition this was
somewhat reversed. Adult mice treated with miR-199a-5p exhibited reduced
expression of GAP43 neuronal growth protein. In old mice, we also found
significantly differentially expressed autophagy markers with miR-199a-5p
overexpression. Using a model of muscle regeneration in adult and old mice, we
found no significant changes to muscle size or function. We can conclude that
upregulated miR-199a-5p may lead to muscle loss via a compromised neuromuscular
junction, potentially driven by dysregulated miR-199a-5p targets, although more
work is needed to precisely understand the nature of this relationship.