Studies on YKL-40 in knee joints of patients with rheumatoid arthritis and osteoarthritis. Involvement of YKL-40 in the joint pathology.
OBJECTIVE
The presence of YKL-40 (human cartilage glycoprotein 39) in synovium, cartilage and synovial fluid (SF) from knee joints of patients with rheumatoid arthritis and osteoarthritis (OA) were related to histopathological changes in synovium and cartilage and to serum YKL-40 and other biochemical markers.


METHODS
The localization of YKL-40 in synovium and cartilage was determined by immunohistochemistry. Synovial inflammation was estimated histologically and by magnetic resonance imaging (MRI). Biochemical markers of inflammation, neutrophil activation and cartilage metabolism were analysed. YKL-40 concentrations in serum and SF were determined by RIA and ELISA.


RESULTS
In the synovium YKL-40 positive cells were found in lining and stromal cells (macrophages) and the number of YKL-40 positive cells was related to the degree of synovitis. In arthritic cartilage, YKL-40 was located to chondrocytes. YKL-40 levels in SF were higher in RA patients with moderate/severe or none/slight synovitis of the knee joint compared to OA patients with moderate/severe or none/slight synovitis. SF YKL-40 correlated with the synovial membrane and the joint effusion volumes determined by magnetic resonance imaging (MRI) and with other biochemical markers of intercellular matrix metabolism. SF YKL-40 was higher than serum YKL-40, and a relationship existed between the YKL-40 levels in SF and serum. Intraarticular glucocorticoid injection was followed by clinical remission and a decrease in serum YKL-40, which increased again at clinical relapse.


CONCLUSIONS
YKL-40 in SF is derived from cells in the inflamed synovium, chondrocytes and SF neutrophils. Joint derived YKL-40 influences serum YKL-40. YKL-40 may be involved in the pathophysiology of the arthritic processes and reflect local disease activity.
Volck
B
B
Department of Rheumatology, Hvidovre Hospital, University of Copenhagen, Denmark. b.volck@dadlnet.dk
Johansen
J S
JS
Stoltenberg
M
M
Garbarsch
C
C
Price
P A
PA
Ostergaard
M
M
Ostergaard
K
K
Løvgreen-Nielsen
P
P
Sonne-Holm
S
S
Lorenzen
I
I
D054392:Adipokines; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000175:diagnosis*; D002356:Cartilage / Q000378:metabolism*; D000071451:Chitinase-3-Like Protein 1; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D007719:Knee Joint; D037102:Lectins; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018375:Neutrophil Activation / Q000502:physiology; D010003:Osteoarthritis / Q000503:physiopathology*; D011863:Radioimmunoassay / Q000379:methods; D013582:Synovial Fluid / Q000737:chemistry; D013583:Synovial Membrane / Q000378:metabolism; D013585:Synovitis / Q000378:metabolism
D054392:Adipokines; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins