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:To investigate the molecular mechanisms responsible for failed skeletal muscle repair in the Chronic limb threatening ischemia (CLTI) limb. We used single cell RNA sequencing (scRNA-seq) to profile the transcriptomes of the skeletal muscle specimens.
Project description:The aim of the experiment is to compare the effect of two different calcineurin A isoforms on skeletal muscle in uninjured mice and during skeletal muscle regeneration (after cardiotoxin injection). The transgenic mice express CnAbeta1 or CnAalpha under the control of the myosin light chain promoter and enhancer.
Project description:Heterochronic blood exchange (HBE) has demonstrated that circulating factors restore youthful features to aged tissues. However, the systemic mediators of those rejuvenating effects remain poorly defined. We show that the beneficial effect of young blood on aged muscle regeneration was diminished when serum was depleted of extracellular vesicles (EVs). Whereas EVs from young animals rejuvenate aged cell bioenergetics and skeletal muscle regeneration, aging shifts EV subpopulation heterogeneity and compromises downstream benefits on recipient cells. Machine learning classifiers revealed that aging shifts the nucleic acid, but not protein, fingerprint of circulating EVs. Alterations in sub-population heterogeneity were accompanied by declines in transcript levels of the pro-longevity protein, α-Klotho, and injection of EVs improved muscle regeneration in a Klotho mRNA-dependent manner. These studies demonstrate that EVs play a key role in the rejuvenating effects of HBE and that Klotho transcripts within EVs phenocopy the effects of young serum on aged skeletal muscle.
Project description:Muscle regeneration is process where different type of cells are interacting together to ensure a proper muscle regeneration. As Muscle stem cells are the central protagonist of muscle regeneration, we performed single cell RNA-seq to observe the change between the different cell types when SETDB1 is absent in Muscle stem cells.
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:Bone regeneration involves skeletal stem/progenitor cells within periosteum and bone marrow, the formation of a fibrous callus followed by the deposition of cartilage and bone matrix to consolidate the fracture. Interactions between bone and skeletal muscle are known to play a role in bone repair but the underlying mechanisms are poorly understood. To better understand the role of skeletal muscle during bone repair, we characterized stem/progenitor cells within skeletal muscle that participate in bone repair. We show that cells originating from bone marrow, periosteum and skeletal muscle are all derived from the Prx1 embryonic lineage. We developed a mouse polytrauma model combining a non-stabilized tibial fracture and mechanical injury to adjacent skeletal muscles. In this polytrauma model, bone fracture healing is impaired. We characterized the Prx1-derived cell population within skeletal muscle in response to fracture and to polytrauma. To do so, we performed fracture and polytrauma in Prx1Cre;Rosa mTmG mice. We harvested skeletal muscle surrounding the tibia at d0 (uninjured), and surrounding the fracture site at d3 and d5 post-fracture or post-polytrauma. Following enzymatic and mechanical digestion of skeletal muscle tissue, we FACS sorted Prx1-derived GFP+ cells and sequenced them using the 10X Chromium technology.
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.