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Updated: Aug 13, 2026
Flow Cytometry Analysis of Immune Cell Subsets within the Murine Spleen, Bone Marrow, Lymph Nodes and Synovial Tissue in an Osteoarthritis Model
Published on: April 24, 2020
Characterization of cells from pannus-like tissue over articular cartilage of advanced osteoarthritis
G-H Yuan1, M Tanaka, K Masuko-Hongo
1Department of Bioregulation, Institute of Medical Science, St. Marianna University, Kawasaki 216-8512, Japan.
Objective:
To identify the characteristics of cells isolated from pannus-like soft tissue on osteoarthritic cartilage (OA pannus cells), and to evaluate the role of this tissue in osteoarthritis (OA).
Methods:
OA pannus cells were isolated from pannus-like tissues in five joints obtained during arthroplasty. The phenotypic features of the isolated cells were characterized by safranin-O staining and immunohistochemical studies. Expression of MMP-1, MMP-3 and MMP-13 was also assessed using reverse transcriptase-polymerase chain reactions (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry.
Results:
Foci and plaque formation of pannus-like tissue over cartilage surface were found in 15 of 21 (71.4%) OA joints macroscopically, and among them, only five samples had enough tissue to be isolated. OA pannus cells were positive for type I collagen and vimentin, besides they also expressed type II collagen and aggrecan mRNA. Spontaneous expression of MMP-1, MMP-3 and MMP-13 was detected in OA pannus cells. Similar or higher levels of MMPs were detected in the supernatant of cultured OA pannus cells compared to OA chondrocytes, and among these MMP-3 levels were relatively higher in OA pannus cells. Immunohistochemically, MMP-3 positive cells located preferentially in pannus-like tissue on the border of original hyaline cartilage.
Conclusion:
Our results showed that OA pannus cells shared the property of mesenchymal cells and chondrocytes; however, their origin seemed different from chondrocytes or synoviocytes. The spontaneous expression of MMPs suggests that they are involved in the articular degradation in OA.
