title: MKP-1 coordinates ordered macrophage-phenotype transitions essential for stem cell-dependent tissue repair.
abstract: Re-establishing tissue homoeostasis in response to injury requires infiltration of inflammatory cells and activation of resident stem cells. However, full tissue recovery also requires that the inflammation is resolved. While it is known that disturbing the interactions between inflammatory cells and tissue resident cells prevents successful healing, the molecular mechanisms underlying the paracrine interactions between these cell types are practically unknown. Here, and in a recent study, we provide mechanistic evidence that macrophages control stem cell-dependent tissue repair. In particular, we found that the temporal spacing of the pro- to anti-inflammatory macrophage polarization switch is controlled by the balance of p38 MAPK (termed here p38) and the MAPK phosphatase MKP-1 during the muscle healing process. Moreover, we demonstrate a new function for MKP-1-regulated p38 signaling in deactivating macrophages during inflammation resolution after injury. Specifically, at advanced stages of regeneration, MKP-1 loss caused an unscheduled "exhaustion-like" state in muscle macrophages, in which neither pro- nor anti-inflammatory cytokines are expressed despite persistent tissue damage, leading to dysregulated reparation by the tissue stem cells. Mechanistically, we demonstrate that p38 and MKP-1 control the AKT pathway through a miR-21-dependent PTEN regulation. Importantly, both genetic and pharmacological interference with the individual components of this pathway restored inflammation-dependent tissue homeostasis in MKP-1-deficient mice and delayed inflammation resolution and tissue repair dysregulation in wild-type mice. Because the process of tolerance to bacterial infection involves a progressive attenuation of pro-inflammatory gene expression, we discuss here the potential similarities between the mechanisms underlying inflammation resolution during tissue repair and those controlling endotoxin tolerance.
authors.affiliation: Cell Biology Group, Department of Experimental and Health Sciences, Pompeu Fabra University (UPF), CIBER on Neurodegenerative diseases (CIBERNED), Barcelona, Spain. eusebio.perdiguero@upf.edu
authors.forename: Eusebio
authors.initials: E
authors.lastname: Perdiguero
authors.forename: Yacine
authors.initials: Y
authors.lastname: Kharraz
authors.forename: Antonio L
authors.initials: AL
authors.lastname: Serrano
authors.forename: Pura
authors.initials: P
authors.lastname: Muñoz-Cánoves
mesh_terms: D000818:Animals; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D010641:Phenotype; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D013234:Stem Cells / Q000276:immunology / Q000378:metabolism*; D014945:Wound Healing; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; C531950:MIRN21 microRNA, mouse; D035683:MicroRNAs; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D054638:Dual Specificity Phosphatase 1; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse