title: Development and characteristics of pannus-like soft tissue in osteoarthritic articular surface in rat osteoarthritis model.
abstract: OBJECTIVE
  Pannus is invasive granulation tissue found on the articular cartilage having rheumatoid arthritis (RA). However, pannus-like tissue has also been found in osteoarthritis (OA). Our previous study showed that pannus-like tissue in OA (OA pannus) was frequently found in human OA samples. The purpose of the study is to investigate the development and the characteristics of OA pannus in a rat OA model.
  
  
  METHODS
  Ligaments of the knee joint were transected in Wister rats to induce OA. The knee joints were removed at weeks 1, 2, 4 and 6, and subjected to histological study. Samples were stained with hematoxylin and eosin (HE), Safranin-O and immuno-stained for vimentin, CD34, type II collagen and MMP-3. The whole knee joint of OA rats was implanted in SCID mice and kept for a further 3 weeks. Then the histological findings were evaluated in HE sections.
  
  
  RESULTS
  OA pannus appeared at week 2 and extend over the articular surface. OA pannus cells were positive for vimentin and/or CD34. At week 6, a part of articular surface was restored with matrix. OA pannus cells expressed MMP-3 as well as type II collagen. Histological study of rat OA knees implanted in SCID mice showed that OA pannus cells filled the joint space and invaded articular cartilage.
  
  
  CONCLUSIONS
  The presence of OA pannus was found in a rat OA model and its features were similar to those in human OA. OA pannus had both catabolic and reparative features, and the latter feature were speculated to be dominant in the later phase of the disease under a certain environmental condition.
authors.affiliation: Institute of Medical Science, St. Marianna University, Nippon Medical School, Tokyo, Japan.
authors.forename: P A
authors.initials: PA
authors.lastname: Duc
authors.forename: K
authors.initials: K
authors.lastname: Yudoh
authors.forename: K
authors.initials: K
authors.lastname: Masuko
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: K
authors.initials: K
authors.lastname: Nishioka
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D018952:Antigens, CD34; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology*; D024043:Collagen Type II / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008592:Menisci, Tibial / Q000473:pathology*; D051379:Mice; D016513:Mice, SCID; D020370:Osteoarthritis, Knee / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia / Q000473:pathology*; D014746:Vimentin / Q000378:metabolism
chemical_list: D018952:Antigens, CD34; D024043:Collagen Type II; D014746:Vimentin; D019278:Matrix Metalloproteinase 3