Project description:The purpose of this study is to investigate how melatonin-influenced promyogenic factor secreted from fibro-adipogenic progenitors (FAPs) regulate muscle regeneration and muscle cell fusion during muscle repair. We highlighted the role of melatonin in regulating crosstalk between muscle stem cells and FAPs during muscle regeneration. Mice that were treated with melatonin exhibited improved muscle regeneration and reduced intramuscular fat deposition, which were associated with enhanced myogenesis, remodeled lipid metabolism and reduced immune cell infiltration. Notably, melatonin did not exert positive effects on cell fusion and myotube formation during differentiation. Interestingly, melatonin repressed fibro-adipogenic progenitor (FAP) adipogenesis in a dose-dependent manner in vitro. Furthermore, melatonin treatment enhanced the pro-myogenic effects of FAPs, which stimulated GDF10 secretion to promote muscle cell fusion and induce myotube hypertrophy.
Project description:Injured skeletal muscle regenerates, but with age or in muscular dystrophies, muscle is replaced by fat. Upon injury, muscle-resident fibro/adipogenic progenitors (FAPs) proliferated and gave rise to adipocytes. These FAPs dynamically produced primary cilia, structures that transduce intercellular cues such as Hedgehog (Hh) signals. Genetically removing cilia from FAPs inhibited intramuscular adipogenesis, both after injury and in a mouse model of Duchenne muscular dystrophy. Blocking FAP ciliation also enhanced myofiber regeneration after injury and reduced myofiber size decline in the muscular dystrophy model. Hh signaling through FAP cilia regulated the expression of TIMP3, a secreted metalloproteinase inhibitor, that inhibited MMP14 to block adipogenesis. A pharmacological mimetic of TIMP3 blocked the conversion of FAPs into adipocytes, pointing to a strategy to combat fatty degeneration of skeletal muscle. We conclude that ciliary Hh signaling by FAPs orchestrates the regenerative response to skeletal muscle injury.
Project description:Fibro adipogenic progenitors (FAPs) promote satellite cell differentiation in adult skeletal muscle regeneration. However, in pathological conditions, FAPs are responsible for fibrosis and fatty infiltrations. Here we show that the NOTCH pathway negatively modulates FAP differentiation both in vitro and in vivo. However, FAPs isolated from young dystrophin- deficient mdx mice are insensitive to this control mechanism. An unbiased mass spectrometry-based proteomic analysis of FAPs from muscles of wild type and mdx mice, suggest that the synergistic cooperation between NOTCH and inflammatory signals controls FAP differentiation. Remarkably, we demonstrated that factors released by hematopoietic cells restore the sensitivity to NOTCH adipogenic inhibition in mdx FAPs. These results offer a basis for rationalizing pathological ectopic fat infiltrations in skeletal muscle and may suggest new therapeutic strategies to mitigate the detrimental effects of fat depositions in muscles of dystrophic patients.
Project description:Skeletal muscle possesses the ability to adapt its size in response to milieus, which is called plasticity. Resistance training induces the increment of muscle mass called muscle hypertrophy. Muscle stem cells (MuSC; also known as muscle stem cells) function to supply new nuclei for myofiber during the overload in muscle. We hypothesize that mesenchymal progenitors (also called FAPs) -derived factor induces MuSC proliferation. In order to identify such factors, RNA-seq of overloaded FAPs were performed.
Project description:Skeletal muscle possesses the ability to adapt its size in response to milieus, which is called plasticity. Resistance training induces the increment of muscle mass called muscle hypertrophy. Muscle stem cells (MuSC; also known as muscle stem cells) function to supply new nuclei for myofiber during the overload in muscle. We found that Yap1 and Taz in mesenchymal progenitors (also called FAPs) are critical for MuSC proliferation in overloaded muscles. We hypothsize that Yap1/Taz-dependent mesenchymal progenitors derived factor induces MuSC proliferation. In order to identify such factors, RNA-seq of overloaded FAPs were performed.
Project description:Fibro-adipogenic progenitors (FAPs) are emerging cellular components of the skeletal muscle regenerative environment. The alternative functional phenotype of FAPs - either supportive of muscle regeneration or promoting fibro-adipogenic degeneration - is a key determinant in the pathogenesis of muscular diseases, including Duchenne Muscular Dystrophy (DMD). However, the molecular regulation of FAPs is still unknown. We show here that an "HDAC-myomiR-BAF60 variant network" regulates the functional phenotype of FAPs in dystrophic muscles of mdx mice. Combinatorial analysis of gene expression microarray and genome-wide chromatin remodeling by Nuclease accessibility (NA)-seq revealed that HDAC inhibitors de-repress a "latent" myogenic program in FAPs from dystrophic muscles at early stages of disease progression. In these cells HDAC inhibition promoted the expression of two core components of the myogenic transcriptional machinery, MyoD and BAF60C, and upregulated the myomiRs (miRs) miR-1.2, miR-133 and miR-206, which target two alternative BAF60 variants (BAF60A and B) ultimately leading to the activation of a pro-myogenic program at the expense of the fibro-adipogenic phenotype. By contrast, FAPs from dystrophic muscles at late stages of disease progression displayed resistance to HDACi-induced chromatin remodeling at myogenic loci and fail to activate the pro-myogenic phenotype. These results reveal a previously unappreciated disease stage-specific bipotency of mesenchimal cells within the regenerative environment of dystrophic muscles. Resolution of such bi-potency by epigenetic interventions, such as HDACi, provides the molecular rationale for the in situ reprogramming of target cells to promote therapeutic regeneration of dystrophic muscles. miRNA modulation upon Histone Deacetylase inhibition in Fibro-Adipogenic Progenitors (FAPs) derived from young mdx mice was evaluated by small RNA-sequencing in 2 controls and 2 treated samples
Project description:FAPs isolated by FACS from miR-206 KO mice and WT mice were grown in culure and then placed in basal medium (BM) for 48 hours to assess the transcriptomic changes
Project description:In our study, we used hindlimb unloading rat model to study fibro-adipogenic progenitor cells (FAPs) condition in muscle atrophy. We have purified FAPs from m. soleus from control rats and after 7 and 14 days of immobilization (HS7, HS14). Also, we performed adipogenic differentiation of FAPS in vitro during 3 days.