Project description:Chronic CO2 retention, or hypercapnia, occurs in pulmonary diseases and leads to skeletal muscle wasting. Muscle wasting and hypercapnia are independently associated with substantial mortality. While abnormal skeletal muscle stem -satellite- cells, contribute to impaired myogenesis in pulmonary diseases, no mechanistic data exists on hypercapnia-driven dysfunctional satellite cells and myogenesis in-vivo. Autophagy regulates satellite cell activation and myogenesis, and while elevated CO2 inhibits autophagy in inflammatory cells, it has never been evaluated in the context of hypercapnia-driven abnormal myogenesis. Using lineage tracing in pre- and post-stem cell transplantation experiments, we show that hypercapnia undermines both Pax7- and α-7 integrin-expressing satellite cells activation, replication and myogenesis. Satellite cells’ multi-omic analyses indicate that hypercapnia disrupts multiple pathways regulated by autophagy. Moreover, autophagy-specific LC3 fluorescence-reporting mouse and cellular data demonstrate that hypercapnia reduces expressions of AMPK and Ulk1, which critically participate in autophagosome formation, and has no effect on the antagonistic mTOR pathway including Ulk1 serine-757 phosphorylation. Moreover, Atg7 knockout-driven loss of autophagy function phenocopies the effects on hypercapnia. After rapamycin administration, the hypercapnia-induced myogenic deficit is corrected by a sharp AMPK activation leading to the autophagy-stimulatory Ulk1 phosphorylation at serine-555, autophagy acceleration, increased satellite cells replication and improved myogenesis post-satellite cells transplantation.
Project description:Hypercapnia exposure in mice leads to reduced skeletal muscle repair capacity and myogenic potential. Autophagy is also reduced in this context. Satellite cells from mice treated with hypercapnia were isolated and compared to satellite cells from normocapnia control mice. Cells were isolated by FACS using Pax7-GFP tamoxifen inducible reporter to ensure enrichment of Pax7 cells.
Project description:Skeletal muscle dysfunction and elevated CO2 in the blood, or hypercapnia, are both associated with higher mortality in acute and chronic pulmonary diseases. Hypercapnia causes accelerated protein degradation, reduced protein synthesis, and dysfunctional myogenesis. We have recently reported that hypercapnia-induced skeletal myogenic dysfunction persists after resolution of CO2 exposure, suggesting the existence of durable cellular aberrations in previously hypercapnic cells. No data on lingering myofiber atrophy after hypercapnia resolution currently exist. Hypercapnia and age-induced skeletal muscle loss phenotypically overlap, and myogenic progenitor cells from hypercapnic mice elicit senescence-associated transcriptional programs. While aging is characterized by unique DNA methylation and other epigenetic changes, the potential association of hypercapnia and age-related differential methylation have never been investigated. In the present study, we show that hypercapnic mice elicit protracted muscle deterioration even after returning to normocapnia and demonstrate aberrant DNA methylation in comparison to animals never exposed to elevated CO2. We also show that these DNA methylation changes do not overlap with age-induced alterations.
Project description:Skeletal muscle dysfunction and elevated CO2 in the blood, or hypercapnia, are both associated with higher mortality in acute and chronic pulmonary diseases. Hypercapnia causes accelerated protein degradation, reduced protein synthesis, and dysfunctional myogenesis. We have recently reported that hypercapnia-induced skeletal myogenic dysfunction persists after resolution of CO2 exposure, suggesting the existence of durable cellular aberrations in previously hypercapnic cells. No data on lingering myofiber atrophy after hypercapnia resolution currently exist. Hypercapnia and age-induced skeletal muscle loss phenotypically overlap, and myogenic progenitor cells from hypercapnic mice elicit senescence-associated transcriptional programs. While aging is characterized by unique DNA methylation and other epigenetic changes, the potential association of hypercapnia and age-related differential methylation have never been investigated. In the present study, we show that hypercapnic mice elicit protracted muscle deterioration even after returning to normocapnia and demonstrate aberrant DNA methylation in comparison to animals never exposed to elevated CO2. We also show that these DNA methylation changes do not overlap with age-induced alterations.
Project description:The influence of the extracellular matrix (ECM) within the stem cell niche remains poorly understood. We found that Syndecan-4 (Sdc4) and Frizzled-7 (Fzd7) form a coreceptor complex in satellite cells and that binding of the ECM glycoprotein Fibronectin (FN) to Sdc4 stimulates the ability of Wnt7a to induce the symmetric expansion of satellite stem cells. Newly activated satellite cells dynamically remodel their niche via transient high-level expression of FN. Knockdown of FN in prospectively isolated satellite cells severely impaired their ability to repopulate the satellite cell niche. Conversely, in vivo overexpression of FN with Wnt7a dramatically stimulated the expansion of satellite stem cells in regenerating muscle. Therefore, activating satellite cells remodel their niche through autologous expression of FN that provides feedback to stimulate Wnt7a signaling through the Fzd7/Sdc4 coreceptor complex. Thus, FN and Wnt7a together regulate the homeostatic levels of satellite stem cells and satellite myogenic cells during regenerative myogenesis. The data set contains one microarray of pooled quiescent skeletal muscle satellite cells
Project description:Patients with chronic obstructive pulmonary disease (COPD)-pulmonary emphysema often develop locomotor muscle dysfunction, which is independently associated with disability and higher mortality in that population. Muscle dysfunction entails reduced muscle mass and force-generation capacity, which are influenced by fibers integrity. Myogenesis, which is muscle turnover driven by progenitor cells such as satellite cells, contributes to the maintenance of muscle integrity in the context of organ development and injury-repair cycles. Injurious events crucially occur in COPD patients’ skeletal muscles in the setting of exacerbations and infections which lead to acute decompensations for limited periods of time after which, patients typically fail to recover the baseline status they had before the acute event. Autophagy, which is dysregulated in muscles from COPD patients, is a key regulator of satellite cells activation and myogenesis, yet very little research has so far investigated the mechanistic role of autophagy dysregulation in COPD muscles. Using a genetically inducible murine model of COPD-driven muscle dysfunction and confirmed with a second genetic animal model, we found a significant myogenic dysfunction associated with a reduced proliferative capacity of freshly isolated satellite cells. Transplantation experiments followed by lineage tracing suggest that an intrinsic defect in satellite cells, and not in the COPD environment, plays a dominant role in the observed myogenic dysfunction. RNA sequencing analysis of freshly isolated satellite cells suggests cell cycle and autophagy dysregulation, which is confirmed by a direct observation of COPD mice satellite cells fluorescent-tracked autophagosome formation. Moreover, spermidine-induced autophagy stimulation leads to improved satellite cells autophagosome turnover, replication rate and myogenesis. Our data suggests that pulmonary emphysema causes a disrupted myogenesis, which could be improved with stimulation of autophagy and satellite cells activation, leading to an attenuated muscle dysfunction in this context.
Project description:Muscle satellite cells (MuSCs), skeletal muscle-resident stem cells, are crucial for regeneration of myofibers. Molecular factors such as cations that trigger the transition of MuSCs from a quiescent to an active state remain largely unidentified. In this study, we identified TRPM7, a Mg2+-permeable ion channel, as a critical determinant for myofiber regeneration. We investigated gene profiles of Trpm7-deficient MuSCs to understand the role of TRPM7 during myogenesis. Our results suggest that TRPM7 governs the myogenesis, cell-cycle progression and mitochondrial biosynthesis in satellite cells to regulate crucial events (ie, activation, proliferation, and myogenesis) during skeletal muscle regeneration.
Project description:Transcriptional profiling of gamma-oryzanol-treated (24h) differentiating equine satellite cells (3rd day of differentiation) compared to control GO-untreated cells. Goal was to determine the effects of gamma-oryzanol influence on gene expression in equine satellite cells during in vitro myogenesis Two-condition experiment, GO-treated (24h) differentiating equine satellite cells (3rd day of differentiation) vs. differentiating equine satellite cells without GO treatment (control). Biological replicates: 4 reps of examined condition (Cy5), 4 control replicates (Cy3)