title: The loss of α2β1 integrin suppresses joint inflammation and cartilage destruction in mouse models of rheumatoid arthritis.
abstract: OBJECTIVE
  Integrin α2β1 functions as a major receptor for type I collagen on different cell types, including fibroblasts and inflammatory cells. Although in vitro data suggest a role for α2β1 integrin in regulating both cell attachment and expression of matrix-degrading enzymes such as matrix metalloproteinases (MMPs), mice that lack the α2 integrin subunit (Itga2(-/-)  mice) develop normally and are fertile. We undertook this study to investigate the effect of Itga2 deficiency in 2 different mouse models of destructive arthritis: the antigen-induced arthritis (AIA) mouse model and the human tumor necrosis factor α (TNFα)-transgenic mouse model.
  
  
  METHODS
  AIA was induced in the knee joints of Itga2(-/-)  mice and wild-type controls. Human TNF-transgenic mice were crossed with Itga2(-/-)  mice and were assessed clinically and histopathologically for signs of arthritis, inflammation, bone erosion, and cartilage damage. MMP expression, proliferation, fibroblast attachment, and ERK activation were determined.
  
  
  RESULTS
  Under arthritic conditions, Itga2 deficiency led to decreased severity of joint pathology. Specifically, Itga2(-/-)  mice showed less severe clinical symptoms and dramatically reduced pannus formation and cartilage erosion. Mice lacking α2β1 integrin exhibited reduced MMP-3 expression, both in their sera and in fibroblast-like synoviocytes (FLS), due to impaired ERK activation. Further, both the proliferation and attachment of FLS to cartilage were partially dependent on α2β1 integrin in vitro and in vivo.
  
  
  CONCLUSIONS
  Our findings suggest that α2β1 integrin contributes significantly to inflammatory cartilage destruction by promoting fibroblast proliferation and attachment and MMP expression.
authors.affiliation: University of Muenster, Muenster, Germany.
authors.forename: Marvin A
authors.initials: MA
authors.lastname: Peters
authors.forename: Doreen
authors.initials: D
authors.lastname: Wendholt
authors.forename: Simon
authors.initials: S
authors.lastname: Strietholt
authors.forename: Svetlana
authors.initials: S
authors.lastname: Frank
authors.forename: Noreen
authors.initials: N
authors.lastname: Pundt
authors.forename: Adelheid
authors.initials: A
authors.lastname: Korb-Pap
authors.forename: Leo A B
authors.initials: LA
authors.lastname: Joosten
authors.forename: Wim B
authors.initials: WB
authors.lastname: van den Berg
authors.forename: George
authors.initials: G
authors.lastname: Kollias
authors.forename: Beate
authors.initials: B
authors.lastname: Eckes
authors.forename: Thomas
authors.initials: T
authors.lastname: Pap
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion; D049109:Cell Proliferation; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D006801:Humans; D007178:Inbreeding; D038982:Integrin alpha2beta1 / Q000172:deficiency* / Q000235:genetics; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013264:Stifle / Q000473:pathology; D013585:Synovitis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology
chemical_list: D038982:Integrin alpha2beta1; D014409:Tumor Necrosis Factor-alpha; D019278:Matrix Metalloproteinase 3; C511769:Mmp3 protein, mouse