title: Inhibition of Shedding of Low-Density Lipoprotein Receptor-Related Protein 1 Reverses Cartilage Matrix Degradation in Osteoarthritis.
abstract: The aggrecanase ADAMTS-5 and the collagenase matrix metalloproteinase 13 (MMP-13) are constitutively secreted by chondrocytes in normal cartilage, but rapidly endocytosed via the cell surface endocytic receptor low-density lipoprotein receptor-related protein 1 (LRP-1) and subsequently degraded. This endocytic system is impaired in osteoarthritic (OA) cartilage due to increased ectodomain shedding of LRP-1. The aim of this study was to identify the LRP-1 sheddase(s) in human cartilage and to test whether inhibition of LRP-1 shedding prevents cartilage degradation in OA.
  
  
  
  Cell-associated LRP-1 and soluble LRP-1 (sLRP-1) released from human cartilage explants and chondrocytes were measured by Western blot analysis. LRP-1 sheddases were identified by proteinase inhibitor profiling and gene silencing with small interfering RNAs. Specific monoclonal antibodies were used to selectively inhibit the sheddases. Degradation of aggrecan and collagen in human OA cartilage was measured by Western blot analysis using an antibody against an aggrecan neoepitope and a hydroxyproline assay, respectively.
  
  
  
  Shedding of LRP-1 was increased in OA cartilage compared with normal tissue. Shed sLRP-1 bound to ADAMTS-5 and MMP-13 and prevented their endocytosis without interfering with their proteolytic activities. Two membrane-bound metalloproteinases, ADAM-17 and MMP-14, were identified as the LRP-1 sheddases in cartilage. Inhibition of their activities restored the endocytic capacity of chondrocytes and reduced degradation of aggrecan and collagen in OA cartilage.
  
  
  
  Shedding of LRP-1 is a key link to OA progression. Local inhibition of LRP-1 sheddase activities of ADAM-17 and MMP-14 is a unique way to reverse matrix degradation in OA cartilage and could be effective as a therapeutic approach.
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Santamaria
authors.affiliation: University of Cambridge, Cambridge, UK.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Botkjaer
authors.affiliation: Royal Veterinary College, Hertfordshire, UK.
authors.forename: Jayesh
authors.initials: J
authors.lastname: Dudhia
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Linda
authors.initials: L
authors.lastname: Troeberg
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Itoh
authors.affiliation: University of Cambridge, Cambridge, UK.
authors.forename: Gillian
authors.initials: G
authors.lastname: Murphy
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagase
mesh_terms: D000072198:ADAM17 Protein / Q000032:analysis / Q000378:metabolism; D000071116:ADAMTS5 Protein / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D053674:Aggrecans / Q000187:drug effects; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000378:metabolism; D002648:Child; D019902:Chondrocytes / Q000502:physiology; D003094:Collagen / Q000187:drug effects; D017364:Collagenases / Q000187:drug effects*; D004705:Endocytosis / Q000187:drug effects; D005260:Female; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000187:drug effects* / Q000502:physiology; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D053511:Matrix Metalloproteinase 14 / Q000032:analysis / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000188:drug therapy* / Q000503:physiopathology; D059748:Proteolysis / Q000187:drug effects*; D055815:Young Adult
chemical_list: D053674:Aggrecans; D000911:Antibodies, Monoclonal; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D003094:Collagen; D000071116:ADAMTS5 Protein; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14; D000072198:ADAM17 Protein