DUBOIS, C. | Search bioRxiv

bioRxiv2024

Transient hypoxia followed by progressive reoxygenation is required for efficient skeletal muscle repair through Rev-ERBalpha modulation

Muscle stem cells (MuSCs) are essential for skeletal muscle repair. Following injury, MuSCs reside in low oxygen environments until muscle fibers and vascularization are restablished. The dynamics of oxygen levels during the regenerative process and its impact on muscle repair has been underappreciated. We confirm that muscle repair is initiated in a low oxygen environment followed by gradual reoxygenation. Strikingly, when muscle reoxygenation is limited by keeping mice under systemic hypoxia, muscle repair is impaired and leads to the formation of hypotrophic myofibers. In vivo, sustained hypoxia decreases the ability of MuSCs to differentiate and fuse independently of HIF-1. Prolonged hypoxia specifically affects the circadian clock by increasing Rev-erb expression in MuSCs. Using pharmacological tools, we demonstrate that Rev-ERB negatively regulates myogenesis by reducing late myogenic cell fusion under prolonged hypoxia. Our results underscore the critical role of progressive muscle reoxygenation after transient hypoxia in coordinating proper myogenesis through Rev-ERB.

physiology↗

bioRxiv2023

A thrombus is formed by a gradient of platelet activation and procoagulant endothelium

IntroductionThe contribution of platelets in thrombosis within microcirculation has been extensively documented in the literature. We previously showed, in vivo, that platelet activation revealed by intracellular calcium mobilization was a crucial step in the growth of thrombi following laser-induced injury, a model of thromboinflammation. AimWe employed a multimodal, correlative microscopy approach and computational biology to investigate the extent of platelet activation and the spatial distribution of platelets throughout a growing thrombus. ResultsWe observed a reversible intracellular platelet calcium mobilization that correlates with the time a platelet resides during thrombus growth. Our bioinformatics analysis displayed three distinct platelet subpopulations resident within a thrombus: (1) resting, (2) partially activated, and (3) "fully" activated platelets. The spatial distribution of the platelet subpopulations in the thrombus creates a double gradient in both the transversal and longitudinal axis, with the maximal percentage of fully activated platelets close to the site of injury. However, these activated platelets did not express negative phospholipids. The injured endothelium was identified to play a vital role in activating the blood coagulation cascade in this model of thrombosis. ConclusionFollowing a laser-induced injury, thrombi are formed by a gradient of activated platelets from the injury site to the periphery of the thrombus. These different activation states of platelets throughout the thrombi regulate the biomechanics of the thrombus. The injured endothelium, rather than platelets, was identified to play a key role in the activation of the blood coagulation cascade in this model of thromboinflammation. EssentialsO_LIComputational biology was used to analyze thrombosis. C_LIO_LINon-activated, low- and fully-activated platelets are part of a thrombus. C_LIO_LIThe activation of the platelets forms a gradient from the site of injury to the periphery. C_LIO_LIThe endothelium, and not platelets, expressed negative phospholipids. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/550692v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@13ab958org.highwire.dtl.DTLVardef@5e7246org.highwire.dtl.DTLVardef@a07df6org.highwire.dtl.DTLVardef@adcbdb_HPS_FORMAT_FIGEXP M_FIG A thrombus is formed by a gradient of platelet activation and procoagulant endothelium C_FIG

physiology↗