The identification of CD163 expressing phagocytic chondrocytes in joint cartilage and its novel scavenger role in cartilage degradation

PLoS One. 2013;8(1):e53312. doi: 10.1371/journal.pone.0053312. Epub 2013 Jan 11.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Animals
  • Antigens, CD / metabolism*
  • Antigens, Differentiation, Myelomonocytic / metabolism*
  • Cartilage, Articular / metabolism
  • Cartilage, Articular / pathology*
  • Cell Count
  • Cell Movement / drug effects
  • Cell Separation
  • Cells, Cultured
  • Chondrocytes / drug effects
  • Chondrocytes / metabolism*
  • Chondrocytes / pathology
  • Female
  • Humans
  • Knee Joint / drug effects
  • Knee Joint / metabolism
  • Knee Joint / pathology
  • Male
  • Middle Aged
  • Osteoarthritis / metabolism
  • Osteoarthritis / pathology
  • Phagocytosis* / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Cell Surface / metabolism*
  • Temporomandibular Joint / metabolism
  • Temporomandibular Joint / pathology
  • Tumor Necrosis Factor-alpha / metabolism
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • CD163 antigen
  • Receptors, Cell Surface
  • Tumor Necrosis Factor-alpha

Grants and funding

This work was supported by grants from the National Natural Science Foundation of China (numbers 81271169, 30801315, 30872870). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.