title: Elevated aggrecanase activity in a rat model of joint injury is attenuated by an aggrecanase specific inhibitor.
abstract: OBJECTIVE
  To evaluate aggrecanase activity after traumatic knee injury in a rat model by measuring the level of aggrecanase-generated Ala-Arg-Gly-aggrecan (ARG-aggrecan) fragments in synovial fluid, and compare with ARG-aggrecan release into joint fluid following human knee injury. To evaluate the effect of small molecule inhibitors on induced aggrecanase activity in the rat model.
  
  
  METHODS
  An enzyme-linked immunosorbent assay (ELISA) was developed to measure ARG-aggrecan levels in animal and human joint fluids. A rat model of meniscal tear (MT)-induced joint instability was used to assess ARG-aggrecan release into joint fluid and the effects of aggrecanase inhibition. Synovial fluids were also obtained from patients with acute joint injury or osteoarthritis and assayed for ARG-aggrecan.
  
  
  RESULTS
  Joint fluids from human patients after knee injury showed significantly enhanced levels of ARG-aggrecan compared to uninjured reference subjects. Similarly, synovial fluid ARG-aggrecan levels increased following surgically-induced joint instability in the rat MT model, which was significantly attenuated by orally dosing the animals with AGG-523, an aggrecanase specific inhibitor.
  
  
  CONCLUSIONS
  Aggrecanase-generated aggrecan fragments were rapidly released into human and rat joint fluids after injury to the knee and remained elevated over a prolonged period. Our findings in human and preclinical models strengthen the connection between aggrecanase activity in joints and knee injury and disease. The ability of a small molecule aggrecanase inhibitor to reduce the release of aggrecanase-generated aggrecan fragments into rat joints suggests that pharmacologic inhibition of aggrecanase activity in humans may be an effective treatment for slowing cartilage degradation following joint injury.
authors.affiliation: Tissue Repair, BioTherapeutics Research & Development, Pfizer, Cambridge, MA 02140, USA. priya.chockalingam@pfizer.com
authors.forename: P S
authors.initials: PS
authors.lastname: Chockalingam
authors.forename: W
authors.initials: W
authors.lastname: Sun
authors.forename: M A
authors.initials: MA
authors.lastname: Rivera-Bermudez
authors.forename: W
authors.initials: W
authors.lastname: Zeng
authors.forename: D R
authors.initials: DR
authors.lastname: Dufield
authors.forename: S
authors.initials: S
authors.lastname: Larsson
authors.forename: L S
authors.initials: LS
authors.lastname: Lohmander
authors.forename: C R
authors.initials: CR
authors.lastname: Flannery
authors.forename: S S
authors.initials: SS
authors.lastname: Glasson
authors.forename: K E
authors.initials: KE
authors.lastname: Georgiadis
authors.forename: E A
authors.initials: EA
authors.lastname: Morris
mesh_terms: D053674:Aggrecans / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D004195:Disease Models, Animal; D010450:Endopeptidases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007718:Knee Injuries / Q000201:enzymology*; D051381:Rats; D011917:Rats, Inbred Lew; D013582:Synovial Fluid / Q000201:enzymology*
chemical_list: D053674:Aggrecans; D015415:Biomarkers; D010450:Endopeptidases; C083641:aggrecanase