Project description:MicroRNAs (miRNAs) are short noncoding RNAs that impact protein expression, regulating a variety of physiological processes. To date, a few miRNAs have been implicated in the process of muscle regeneration after injury; however, our understanding of the miRNAs involved and their regulatory mechanisms remains incomplete.The analysis showed differences of microRNAs in the tibialis anterior muscles at days 0, 1 and 3 post-cardiotoxin injury.
Project description:MicroRNAs (miRNAs) are important in the regulation of many biological processes including muscle development. However, little is known regarding miRNA regulation of muscle regeneration. In mature murine tibialis anterior muscle following injury, 298 miRNAs were significantly changed during the time course of muscle regeneration including 86 that were altered greater than 10-fold as compared to uninjured muscle. Temporal miRNA expression patterns were identified and included inflammation-related miRNAs (miR-223 and -147) that increased immediately after injury; this pattern contrasted to that of mature muscle-specific miRNAs (miR-1, -133a and -499) that were abruptly decreased following injury and then up-regulated in later regenerative events. Another cluster of miRNAs were transiently increased in the early days of muscle regeneration. This included miR-351, a miRNA that was also transiently expressed during myogenic progenitor cell (MPC) differentiation in vitro. Based on computational predictions, further studies demonstrated that E2f3 was a target of miR-351 in myoblasts. Moreover, knockdown of miR-351 expression inhibited MPC proliferation and promoted apoptosis during MPC differentiation, whereas miR-351 overexpression protected MPC from apoptosis during differentiation. Collectively, these observations suggest that miR-351 is involved in both the maintenance of MPC proliferation and the transition of MPC into differentiated myotubes. Thus, a novel, time-dependent sequence of molecular events during skeletal muscle regeneration has been identified, i.e., miR-351 inhibits E2f3 expression, a key regulator of cell cycle progression and proliferation, and promotes MPC proliferation and protects early differentiating MPC from apoptosis, important events in the hostile tissue environment after acute muscle injury. Skeletal muscles are damaged and repaired repeatedly throughout life. Muscle regeneration maintains locomotor function during aging and delays the appearance of clinical symptoms in neuromuscular diseases, such as Duchenne muscular dystrophy. The capacity for skeletal muscle growth and regeneration is conferred by satellite cells located between the basal lamina and the sarcolemma of mature myofibers. Upon injury, satellite cells reenter the cell cycle, proliferate, and then exit the cell cycle either to renew the quiescent satellite cell pool or to differentiate into mature myofibers. Despite recent advances, genes involved in these processes are still largely unknown. Understanding the molecular mechanisms that regulate satellite cell activities could promote development of novel countermeasures to enhance muscle regeneration that is compromised by diseases or aging. Using a muscle injury mouse model, we profiled miRNA expression during muscle regeneration.
Project description:Background Changes in protein turnover play an important role in dynamic physiological processes, including skeletal muscle regeneration, which occurs as an essential part of tissue repair after injury. The inability of muscle tissue to recapitulate this regenerative process can lead to pathology and clinical symptoms in various musculoskeletal diseases, including muscular dystrophies and pathological atrophy.
Methods Here, we employed a workflow that couples deuterated water (2H2O) administration with tandem mass spectrometry (MS) to systematically measure in-vivo protein turnover rates across the muscle proteome in 8-week-old male C57BL6/J mice. We compared the turnover kinetics of over 100 proteins in response to cardiotoxin (CTX) induced muscle damage and regeneration at unique sequential stages along the regeneration timeline. This analysis is compared to gene expression data from mRNA-sequencing (mRNA-seq) from the same tissue.
Results The data reveals quantitative protein flux signatures in response to necrotic damage, in addition to sequential differences in cell proliferation, energy metabolism, and contractile gene expression. Interestingly, the mRNA changes correlated poorly with changes in protein synthesis rates, consistent with post-transcriptional control mechanisms.	
Conclusions In summary, the experiments described here reveal the signatures and timing of protein flux changes during skeletal muscle regeneration, as well as the inability of mRNA expression measurements to reveal changes in directly measured protein turnover rates. The results of this work described here provide a better understanding of the muscle regeneration process and could help to identify potential biomarkers or therapeutic targets.
Project description:Background - Changes in protein turnover play an important role in dynamic physiological processes, including skeletal muscle regeneration, which occurs as an essential part of tissue repair after injury. The inability of muscle tissue to recapitulate this regenerative process can lead to pathology and clinical symptoms in various musculoskeletal diseases, including muscular dystrophies and pathological atrophy.
Methods - Here, we employed a workflow that couples deuterated water (2H2O) administration with tandem mass spectrometry (MS) to systematically measure in-vivo protein turnover rates across the muscle proteome in 8-week-old male C57BL6/J mice. We compared the turnover kinetics of over 100 proteins in response to cardiotoxin (CTX) induced muscle damage and regeneration at unique sequential stages along the regeneration timeline. This analysis is compared to gene expression data from mRNA-sequencing (mRNA-seq) from the same tissue.
Results - The data reveals quantitative protein flux signatures in response to necrotic damage, in addition to sequential differences in cell proliferation, energy metabolism, and contractile gene expression. Interestingly, the mRNA changes correlated poorly with changes in protein synthesis rates, consistent with post-transcriptional control mechanisms.	
Conclusions - In summary, the experiments described here reveal the signatures and timing of protein flux changes during skeletal muscle regeneration, as well as the inability of mRNA expression measurements to reveal changes in directly measured protein turnover rates. The results of this work described here provide a better understanding of the muscle regeneration process and could help to identify potential biomarkers or therapeutic targets.
Project description:Background Changes in protein turnover play an important role in dynamic physiological processes, including skeletal muscle regeneration, which occurs as an essential part of tissue repair after injury. The inability of muscle tissue to recapitulate this regenerative process can lead to pathology and clinical symptoms in various musculoskeletal diseases, including muscular dystrophies and pathological atrophy. Methods Here, we employed a workflow that couples deuterated water (2H2O) administration with tandem mass spectrometry (MS) to systematically measure in-vivo protein turnover rates across the muscle proteome in 8-week-old male C57BL6/J mice. We compared the turnover kinetics of over 100 proteins in response to cardiotoxin (CTX) induced muscle damage and regeneration at unique sequential stages along the regeneration timeline. This analysis is compared to gene expression data from mRNA-sequencing (mRNA-seq) from the same tissue. Results The data reveals quantitative protein flux signatures in response to necrotic damage, in addition to sequential differences in cell proliferation, energy metabolism, and contractile gene expression. Interestingly, the mRNA changes correlated poorly with changes in protein synthesis rates, consistent with post-transcriptional control mechanisms. Conclusions In summary, the experiments described here reveal the signatures and timing of protein flux changes during skeletal muscle regeneration, as well as the inability of mRNA expression measurements to reveal changes in directly measured protein turnover rates. The results of this work described here provide a better understanding of the muscle regeneration process and could help to identify potential biomarkers or therapeutic targets.
Project description:Utilizing glycerol intramuscular injections in M. musculus provide a models of skeletal muscle damage followed by skeletal muscle regeneration. In particular, glycerol-induced muscle injury triggers accute activation of skeletal muscle stem cells, called satellite cells. However, aging dramatically impairs the regenerative capacity of satellite cells. We characterized genome-wide expression profiles of young and old satellite cells in the non-proliferative and activated state, freshly isolated to non-injured or damaged muscles, respectively. Our goal was to uncover new regulatory signaling specific to satellite cells entry into the activation and myogenic program that are affected with age. Satellite cells were isolated in either quiescent / non-proliferative or activated state from uninjured or 3 days after glycerol-induced injury of tibialis anterior, gastrocnemius and quadriceps, respectively. Young (2-4 months old) and old (20-24 months old) wildtype C57BL/6J male were used, with five to six biological replicates per group.
Project description:Single-cell RNA sequencing of cells dissociated from skeletal muscle at discrete regeneration timepoints to reveal transcriptional identities of contributors to skeletal muscle regeneration.
Project description:While aging results in marked decreases in the capacity of skeletal muscle to repair following injury, as well as increases in fibrosis, the pathways and factors that regulate these processes are poorly defined. P311/Nrep (P311) is a highly conserved protein known to promote fibrosis through TGF-beta production in non-muscle tissues. Considering the over-production of TGF-beta in aged muscle, especially in the context of regeneration, we aimed to determine if the loss of P311 would enhance aged muscle regeneration. To test this hypothesis, we utilized a chemical injury (BaCl2) model to injure the tibialis anterior (TA) muscle in young (4-7 months) and old (24 months) wild-type and global P311 knockout mice (P311-/-). In wild-type mice, P311 expression increased in response to injury in young muscle and to an even greater extent in aged muscle. P311-deficiency decreased TGF-β production, particularly in old muscle tissue. P311-deficiency also decreased fibrosis in old mice, including improved histology and reductions in fibrotic gene markers. Regeneration as assessed by fiber regrowth and force generation was increased in old mice with P311-deficiency, and genetic programs that drive skeletal muscle regeneration were enriched in old P311-/- mice relative to old wild-type mice. Single-cell transcriptomic analysis revealed P311 was found to be highly expressed in skeletal muscle fibroblast and fibroadipogenic progenitor (FAP) populations. The loss of P311 in aged muscle FAPs was sufficient to reduce their fibrogenic capacity. These findings establish P311 as a therapeutic target to enhance aged muscle regeneration through reductions in fibrosis and related fibrogenic pathways.