Hypoxic synovial environment and expression of macrophage inflammatory protein 3gamma/CCL20 in juvenile idiopathic arthritis.
OBJECTIVE
Synovial inflammation is a major determinant of juvenile idiopathic arthritis (JIA) pathogenesis and is mediated by local chemokine secretion. Monocytic cells are an important source of chemokines. The purpose of this study was to investigate expression of CCL20, a macrophage inflammatory protein, in synovial fluid (SF) and SF-derived monocytic cells from JIA patients and its regulation by hypoxia, a common feature of the inflamed synovial environment.


METHODS
Mononuclear cells and monocytic cells were isolated from paired SF and peripheral blood (PB) samples from JIA patients and were maintained in a hypoxic environment or subjected to reoxygenation. CCL20 concentrations in SF, PB, and culture supernatants were measured by enzyme-linked immunosorbent assay. CCL20 expression was assessed in both freshly purified and cultured cells by reverse transcriptase-polymerase chain reaction and immunocytochemistry. Hypoxia-inducible factor 1alpha (HIF-1alpha) and HIF-2alpha were detected in the synovial tissue and cells of JIA patients by immunohistochemistry and Western blotting.


RESULTS
CCL20 concentrations were significantly higher in SF compared with PB samples (P < 0.0001). SF mononuclear cells, but not matched PB mononuclear cells, constitutively expressed CCL20 messenger RNA. The SF monocytic cell fraction produced higher amounts of CCL20 than did SF lymphocytes, and CCL20 expression was associated with HIF positivity. Reoxygenation abrogated HIF and CCL20 expression, which was maintained in SF monocytic cells exposed to prolonged hypoxia.


CONCLUSIONS
CCL20 is released into the SF of JIA patients, and SF monocytic cells are a major source of this chemokine. The hypoxic synovial microenvironment may directly contribute to the persistent inflammation associated with JIA by increasing CCL20 production by SF monocytic cells, thus representing a potential therapeutic target.
G Gaslini Institute, Genoa, Italy. mcbosco1@virgilio.it
Maria Carla
MC
Bosco
Silvana
S
Delfino
Francesca
F
Ferlito
Florinda
F
Battaglia
Maura
M
Puppo
Andrea
A
Gregorio
Claudio
C
Gambini
Marco
M
Gattorno
Alberto
A
Martini
Luigi
L
Varesio
D001171:Arthritis, Juvenile / Q000378:metabolism* / Q000503:physiopathology; D016022:Case-Control Studies; D002478:Cells, Cultured; D054418:Chemokine CCL20 / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D007719:Knee Joint; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*
C108355:CCL20 protein, human; D054418:Chemokine CCL20; D012333:RNA, Messenger