Conditional Deletion of Dicer in Adult Mice Impairs Skeletal Muscle Regeneration

Abstract

Skeletal muscle has a remarkable regenerative capacity, which is orchestrated by multiple processes, including the proliferation, fusion, and differentiation of the resident stem cells in muscle. MicroRNAs (miRNAs) are small noncoding RNAs that mediate the translational repression or degradation of mRNA to regulate diverse biological functions. Previous studies have suggested that several miRNAs play important roles in myoblast proliferation and differentiation in vitro. However, their potential roles in skeletal muscle regeneration in vivo have not been fully established. In this study, we generated a mouse in which the Dicer gene, which encodes an enzyme essential in miRNA processing, was knocked out in a tamoxifen-inducible way (iDicer KO mouse) and determined its regenerative potential after cardiotoxin-induced acute muscle injury. Dicer mRNA expression was significantly reduced in the tibialis anterior muscle of the iDicer KO mice, whereas the expression of muscle-enriched miRNAs was only slightly reduced in the Dicer-deficient muscles. After cardiotoxin injection, the iDicer KO mice showed impaired muscle regeneration. We also demonstrated that the number of PAX7+ cells, cell proliferation, and the myogenic differentiation capacity of the primary myoblasts did not differ between the wild-type and the iDicer KO mice. Taken together, these data demonstrate that Dicer is a critical factor for muscle regeneration in vivo.

Muscle memory: myonuclear accretion, maintenance, morphology, and miRNA levels with training and detraining in adult mice

“…12 Our laboratory and others recently found that muscle-specific miRNAs (myomiRs) persist for prolonged periods in the absence of the miRNA processing enzyme Dicer. 13,14 If prolonged miRNA stability is a quality specific to skeletal muscle, 15 myomiRs could be good candidates as long-term epigenetic regulators of exercise adaptation, especially given their known function in regulating muscle mass. [16][17][18] In the current investigation, we provide evidence on myonuclear accretion and maintenance in skeletal muscles with different fibre type composition and function after 2 months of PoWeR training and prolonged 6-month detraining.…”

“…Beyond myonuclear number, recent evidence suggests that DNA methylation changes in skeletal muscle induced by training could be long‐lasting and represent a memory of prior training exposure that facilitates future adaptation 12 . Our laboratory and others recently found that muscle‐specific miRNAs (myomiRs) persist for prolonged periods in the absence of the miRNA processing enzyme Dicer 13,14 . If prolonged miRNA stability is a quality specific to skeletal muscle, 15 myomiRs could be good candidates as long‐term epigenetic regulators of exercise adaptation, especially given their known function in regulating muscle mass 16–18 …”

Inducible and reversible inhibition of miRNA-mediated gene repression in vivo

“…In previous studies where Dicer1 was conditionally ablated in the skeletal muscle of adult mice, muscle regeneration was impaired after acute injury, but no effect on muscle morphology or function was observed during homeostasis 24,81,82 . An explanation for this difference is that in the Dicer1 conditional knockout experiments miRNA levels were only partially reduced even weeks after Dicer1 ablation, likely reflecting the high stability of these short non-coding RNAs.…”

microRNA-mRNA Profile of Skeletal Muscle Differentiation and Relevance to Congenital Myotonic Dystrophy

“…The role of miRNAs in muscle disorders was supported by observation that global depletion of miRNAs through Dicer knockout in mice lead to impaired muscle development [ 58 ]. CMD patient muscle has lower expression of myomiRs such as miR-1 [ 59 ], possibly due to differences in miRNA processing [ 59 , 60 ].…”