Project description:The purpose of this study is to investigate how SREBP1a in macrophages regulates cellular function during muscle regeneration process after injury. We report that the systemic deletion of Srebf1, encoding SREBP1, and macrophage-specific deletion of Srebf1a, encoding SREBP1a, delays the resolution of inflammation, and impairs skeletal muscle regeneration after injury. Srebf1 deficiency impairs mitochondrial function of macrophages and suppresses the accumulation of reparative macrophages to the injured site.
Project description:We identified caspase-4/S1P/SREBP1 pathway that is activated in LPS-treated macrophages. To analyze the functions of caspase-4 and SREBP1 in gene expression in macrophages, we analyzed the effects of deletions of Casp4 and Srebf1 in bone marrow-derived macrophages by RNA-seq.
Project description:We studied metabolic angiocrine mechanisms by which endothelial cell_ECs_ can contribute to muscle regeneration from ischemia by using endothelial specific pfkfb3 knockout mice_pfkfb3DEC_ after hind-limb ischemia_HLI_. During muscle regeneration, monocytes are recruited to the injured area and rapidly become macrophages which initially exhibit a more pro-inflammatory M1-like phenotype but soon thereafter functionally repolarize towards an M2-like phenotype to actively support muscle regeneration. Interestingly, macrophages derived from pfkfb3DEC failed to polarized to M2-like macrophages after HLI. Reduced macrophage polarization impairs angiogenesis and muscle regeneration. The RNAseq data are pfkfb3DEC and pfkfb3WT muscle derived macrophages 3 days after HLI.
Project description:IFNγ is traditionally known as a pro-inflammatory cytokine with diverse roles in antimicrobial and antitumor immunity. Yet, findings regarding its sources and functions during the regeneration process following a sterile injury are conflicting. Here, we show that natural killer (NK) cells are the main source of IFNγ in regenerating muscle. Beyond this cell population, IFNγ production is limited to a small population of T cells. We further show that NK cells do not play a major role in muscle regeneration following an acute injury or in dystrophic mice. Surprisingly, the absence of IFNγ per se also has no effect on muscle regeneration following an acute injury. However, the role of IFNγ is partially unmasked when TNFα is also neutralized, suggesting a compensatory mechanism. Using transgenic mice, we showed that conditional inhibition of IFNGR1 signaling in muscle stem cells or fibro-adipogenic progenitors does not play a major role in muscle regeneration. In contrast to common belief, we found that IFNγ is not present in the early inflammatory phase of the regeneration process, but rather peaks when macrophages are acquiring an anti-inflammatory phenotype. Our further transcriptomic analysis suggests that IFNγ cooperates with TNFα to regulate the transition of macrophages from pro- to anti-inflammatory. The absence of the cooperative effect of these cytokines on macrophages, however, does not result in significant regeneration impairment likely due to the presence of other compensatory mechanisms. Our findings support the arising view of IFNγ as a pleiotropic inflammatory regulator rather than an inducer of the inflammatory response.
Project description:IFNγ is traditionally known as a pro-inflammatory cytokine with diverse roles in antimicrobial and antitumor immunity. Yet, findings regarding its sources and functions during the regeneration process following a sterile injury are conflicting. Here, we show that natural killer (NK) cells are the main source of IFNγ in regenerating muscle. Beyond this cell population, IFNγ production is limited to a small population of T cells. We further show that NK cells do not play a major role in muscle regeneration following an acute injury or in dystrophic mice. Surprisingly, the absence of IFNγ per se also has no effect on muscle regeneration following an acute injury. However, the role of IFNγ is partially unmasked when TNFα is also neutralized, suggesting a compensatory mechanism. Using transgenic mice, we showed that conditional inhibition of IFNGR1 signaling in muscle stem cells or fibro-adipogenic progenitors does not play a major role in muscle regeneration. In contrast to common belief, we found that IFNγ is not present in the early inflammatory phase of the regeneration process, but rather peaks when macrophages are acquiring an anti-inflammatory phenotype. Our further transcriptomic analysis suggests that IFNγ cooperates with TNFα to regulate the transition of macrophages from pro- to anti-inflammatory. The absence of the cooperative effect of these cytokines on macrophages, however, does not result in significant regeneration impairment likely due to the presence of other compensatory mechanisms. Our findings support the arising view of IFNγ as a pleiotropic inflammatory regulator rather than an inducer of the inflammatory response.