title: Comparative Study of Injury Models for Studying Muscle Regeneration in Mice.
abstract: BACKGROUND
  A longstanding goal in regenerative medicine is to reconstitute functional tissues or organs after injury or disease. Attention has focused on the identification and relative contribution of tissue specific stem cells to the regeneration process. Relatively little is known about how the physiological process is regulated by other tissue constituents. Numerous injury models are used to investigate tissue regeneration, however, these models are often poorly understood. Specifically, for skeletal muscle regeneration several models are reported in the literature, yet the relative impact on muscle physiology and the distinct cells types have not been extensively characterised.
  
  
  METHODS
  We have used transgenic Tg:Pax7nGFP and Flk1GFP/+ mouse models to respectively count the number of muscle stem (satellite) cells (SC) and number/shape of vessels by confocal microscopy. We performed histological and immunostainings to assess the differences in the key regeneration steps. Infiltration of immune cells, chemokines and cytokines production was assessed in vivo by Luminex®.
  
  
  RESULTS
  We compared the 4 most commonly used injury models i.e. freeze injury (FI), barium chloride (BaCl2), notexin (NTX) and cardiotoxin (CTX). The FI was the most damaging. In this model, up to 96% of the SCs are destroyed with their surrounding environment (basal lamina and vasculature) leaving a "dead zone" devoid of viable cells. The regeneration process itself is fulfilled in all 4 models with virtually no fibrosis 28 days post-injury, except in the FI model. Inflammatory cells return to basal levels in the CTX, BaCl2 but still significantly high 1-month post-injury in the FI and NTX models. Interestingly the number of SC returned to normal only in the FI, 1-month post-injury, with SCs that are still cycling up to 3-months after the induction of the injury in the other models.
  
  
  CONCLUSIONS
  Our studies show that the nature of the injury model should be chosen carefully depending on the experimental design and desired outcome. Although in all models the muscle regenerates completely, the trajectories of the regenerative process vary considerably. Furthermore, we show that histological parameters are not wholly sufficient to declare that regeneration is complete as molecular alterations (e.g. cycling SCs, cytokines) could have a major persistent impact.
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.|Paris Est University, Créteil, France.
authors.forename: David
authors.initials: D
authors.lastname: Hardy
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: Aurore
authors.initials: A
authors.lastname: Besnard
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Latil
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.|Paris Descartes University, Sorbonne Paris Cité, Paris France.
authors.forename: Grégory
authors.initials: G
authors.lastname: Jouvion
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: David
authors.initials: D
authors.lastname: Briand
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.|IRBA, Unité Interactions Hôte-Agents Pathogènes, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Thépenier
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Pascal
authors.affiliation: Inserm, U955, Plateforme de Cytométrie en Flux, Créteil, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Guguin
authors.affiliation: Institut Pasteur, Stem Cells & Development Unit, Department of Developmental & Stem Cell Biology, Paris, France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Gayraud-Morel
authors.affiliation: Institut Pasteur, Cytokines and Inflammation Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Cavaillon
authors.affiliation: Institut Pasteur, Stem Cells & Development Unit, Department of Developmental & Stem Cell Biology, Paris, France.
authors.forename: Shahragim
authors.initials: S
authors.lastname: Tajbakhsh
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Rocheteau
authors.affiliation: Institut Pasteur, Human histopathology and animal models Unit, Infection and Epidemiology Department, Paris, France.|Paris Descartes University, Sorbonne Paris Cité, Paris France.|Centre Hospitalier Sainte Anne, Laboratoire de Neuropathologie, Paris, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chrétien
mesh_terms: D000818:Animals; D017609:Barium Compounds / Q000633:toxicity; D002712:Chlorides / Q000633:toxicity; D004179:Cobra Cardiotoxin Proteins / Q000633:toxicity; D000067390:Cold Injury / Q000473:pathology / Q000503:physiopathology; D016207:Cytokines / Q000502:physiology; D004546:Elapid Venoms / Q000633:toxicity; D005355:Fibrosis; D005615:Freezing / Q000009:adverse effects; D049452:Green Fluorescent Proteins / Q000032:analysis; D008264:Macrophages / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D023421:Models, Animal; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000187:drug effects / Q000293:injuries / Q000473:pathology / Q000502:physiology*; D032446:Myoblasts / Q000502:physiology; D009336:Necrosis; D018919:Neovascularization, Physiologic; D012038:Regeneration / Q000276:immunology / Q000502:physiology; D032496:Satellite Cells, Skeletal Muscle / Q000502:physiology; D013234:Stem Cells / Q000502:physiology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000032:analysis
chemical_list: D017609:Barium Compounds; D002712:Chlorides; D004179:Cobra Cardiotoxin Proteins; D016207:Cytokines; D004546:Elapid Venoms; C024986:barium chloride; D049452:Green Fluorescent Proteins; C005082:notexin; D040301:Vascular Endothelial Growth Factor Receptor-2