title: The identification of CD163 expressing phagocytic chondrocytes in joint cartilage and its novel scavenger role in cartilage degradation.
abstract: BACKGROUND
  Cartilage degradation is a typical characteristic of arthritis. This study examined whether there was a subset of phagocytic chondrocytes that expressed the specific macrophage marker, CD163, and investigated their role in cartilage degradation.
  
  
  METHODS
  Cartilage from the knee and temporomandibular joints of Sprague-Dawley rats was harvested. Cartilage degradation was experimentally-induced in rat temporomandibular joints, using published biomechanical dental methods. The expression levels of CD163 and inflammatory factors within cartilage, and the ability of CD163(+) chondrocytes to conduct phagocytosis were investigated. Cartilage from the knees of patients with osteoarthritis and normal cartilage from knee amputations was also investigated.
  
  
  RESULTS
  In the experimentally-induced degrading cartilage from temporomandibular joints, phagocytes were capable of engulfing neighboring apoptotic and necrotic cells, and the levels of CD163, TNF-α and MMPs were all increased (P<0.05). However, the levels of ACP-1, NO and ROS, which relate to cellular digestion capability were unchanged (P>0.05). CD163(+) chondrocytes were found in the cartilage mid-zone of temporomandibular joints and knee from healthy, three-week old rats. Furthermore, an increased number of CD163(+) chondrocytes with enhanced phagocytic activity were present in Col-II(+) chondrocytes isolated from the degraded cartilage of temporomandibular joints in the eight-week experimental group compared with their age-matched controls. Increased number with enhanced phagocytic activity of CD163(+) chondrocytes were also found in isolated Col-II(+) chondrocytes stimulated with TNF-α (P<0.05). Mid-zone distribution of CD163(+) cells accompanied with increased expression of CD163 and TNF-α were further confirmed in the isolated Col-II(+) chondrocytes from the knee cartilage of human patients with osteoarthritis, in contrast to the controls (both P<0.05).
  
  
  CONCLUSIONS
  An increased number of CD163(+) chondrocytes with enhanced phagocytic activity were discovered within degraded joint cartilage, indicating a role in eliminating degraded tissues. Targeting these cells provides a new strategy for the treatment of arthritis.
authors: Department of Oral Anatomy and Physiology and TMD, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors: Kai
authors: K
authors: Jiao
authors: Jing
authors: J
authors: Zhang
authors: Mian
authors: M
authors: Zhang
authors: Yuying
authors: Y
authors: Wei
authors: Yaoping
authors: Y
authors: Wu
authors: Zhong Ying
authors: ZY
authors: Qiu
authors: Jianjun
authors: J
authors: He
authors: Yunxin
authors: Y
authors: Cao
authors: Jintao
authors: J
authors: Hu
authors: Han
authors: H
authors: Zhu
authors: Li-Na
authors: LN
authors: Niu
authors: Xu
authors: X
authors: Cao
authors: Kun
authors: K
authors: Yang
authors: Mei-Qing
authors: MQ
authors: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology*; D002452:Cell Count; D002465:Cell Movement / Q000187:drug effects; D002469:Cell Separation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D010587:Phagocytosis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013704:Temporomandibular Joint / Q000378:metabolism / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D011956:Receptors, Cell Surface; D014409:Tumor Necrosis Factor-alpha