title: Modulation of macrophage activation state protects tissue from necrosis during critical limb ischemia in thrombospondin-1-deficient mice.
abstract: BACKGROUND
  Macrophages, key regulators of healing/regeneration processes, strongly infiltrate ischemic tissues from patients suffering from critical limb ischemia (CLI). However pro-inflammatory markers correlate with disease progression and risk of amputation, suggesting that modulating macrophage activation state might be beneficial. We previously reported that thrombospondin-1 (TSP-1) is highly expressed in ischemic tissues during CLI in humans. TSP-1 is a matricellular protein that displays well-known angiostatic properties in cancer, and regulates inflammation in vivo and macrophages properties in vitro. We therefore sought to investigate its function in a mouse model of CLI.
  
  
  RESULTS
  Using a genetic model of tsp-1(-/-) mice subjected to femoral artery excision, we report that tsp-1(-/-) mice were clinically and histologically protected from necrosis compared to controls. Tissue protection was associated with increased postischemic angiogenesis and muscle regeneration. We next showed that macrophages present in ischemic tissues exhibited distinct phenotypes in tsp-1(-/-) and wt mice. A strong reduction of necrotic myofibers phagocytosis was observed in tsp-1(-/-) mice. We next demonstrated that phagocytosis of muscle cell debris is a potent pro-inflammatory signal for macrophages in vitro. Consistently with these findings, macrophages that infiltrated ischemic tissues exhibited a reduced postischemic pro-inflammatory activation state in tsp-1(-/-) mice, characterized by a reduced Ly-6C expression and a less pro-inflammatory cytokine expression profile. Finally, we showed that monocyte depletion reversed clinical and histological protection from necrosis observed in tsp-1(-/-) mice, thereby demonstrating that macrophages mediated tissue protection in these mice.
  
  
  CONCLUSIONS
  This study defines targeting postischemic macrophage activation state as a new potential therapeutic approach to protect tissues from necrosis and promote tissue repair during CLI. Furthermore, our data suggest that phagocytosis plays a crucial role in promoting a deleterious intra-tissular pro-inflammatory macrophage activation state during critical injuries. Finally, our results describe TSP-1 as a new relevant physiological target during critical leg ischemia.
authors.affiliation: INSERM, U833, Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bréchot
authors.forename: Elisa
authors.initials: E
authors.lastname: Gomez
authors.forename: Marine
authors.initials: M
authors.lastname: Bignon
authors.forename: Jamila
authors.initials: J
authors.lastname: Khallou-Laschet
authors.forename: Michael
authors.initials: M
authors.lastname: Dussiot
authors.forename: Aurélie
authors.initials: A
authors.lastname: Cazes
authors.forename: Cécile
authors.initials: C
authors.lastname: Alanio-Bréchot
authors.forename: Mélanie
authors.initials: M
authors.lastname: Durand
authors.forename: Josette
authors.initials: J
authors.lastname: Philippe
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Silvestre
authors.forename: Nico
authors.initials: N
authors.lastname: Van Rooijen
authors.forename: Pierre
authors.initials: P
authors.lastname: Corvol
authors.forename: Antonino
authors.initials: A
authors.lastname: Nicoletti
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Chazaud
authors.forename: Stéphane
authors.initials: S
authors.lastname: Germain
mesh_terms: D000818:Animals; D042783:Endothelial Cells / Q000378:metabolism; D006614:Hindlimb / Q000098:blood supply* / Q000473:pathology*; D018836:Inflammation Mediators / Q000378:metabolism; D007511:Ischemia / Q000473:pathology* / Q000517:prevention & control*; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes; D032342:Muscle Cells / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D009389:Neovascularization, Pathologic / Q000378:metabolism; D010587:Phagocytosis; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000172:deficiency* / Q000378:metabolism
chemical_list: D018836:Inflammation Mediators; D019700:Thrombospondin 1