Vascular endothelial growth factor expression by activated synovial leukocytes in rheumatoid arthritis: critical involvement of the interaction with synovial fibroblasts.
OBJECTIVE
To examine the expression and regulation of the angiogenic factor, vascular endothelial growth factor (VEGF), by fibroblast-like synoviocytes (FLS), monocytes, and polymorphonuclear neutrophils (PMNs) isolated from the synovial fluid (SF) of rheumatoid arthritis (RA) patients.


METHODS
Monocytes or PMNs obtained from RA SF were cocultured with unstimulated, semiconfluent RA FLS. Culture supernatants were assayed for the proliferation and in vitro tube formation of endothelial cells, and for the production of VEGF, by enzyme-linked immunosorbent assay. The expression of VEGF messenger RNA and protein was also determined by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively.


RESULTS
We found that the interaction of inflammatory, activated leukocytes with FLS resulted in synergistic increases in VEGF expression and secretion, which contributed to the proliferation of endothelial cells and to in vitro endothelial tube formation. The induction of VEGF was mediated via specific adhesion molecules, as indicated by the finding that anti-integrin antibodies significantly inhibited VEGF. Furthermore, the levels of VEGF secretion correlated with the expression of cell surface integrin (CD11b and CD18) on both monocytes and PMNs in the SF.


CONCLUSIONS
VEGF expression within inflamed joints thus appears to be regulated not only by inflammatory cytokines, but also by the physical interaction of activated leukocytes and FLS. Once expressed, VEGF likely plays a crucial role in the neovascularization of the pannus and the progressive joint destruction associated with the synovial inflammation of RA.
Kasama
T
T
First Department of Internal Medicine, Showa University School of Medicine, Tokyo, Japan. tkasama@med.showa-u.ac.jp
Shiozawa
F
F
Kobayashi
K
K
Yajima
N
N
Hanyuda
M
M
Takeuchi
H T
HT
Mori
Y
Y
Negishi
M
M
Ide
H
H
Adachi
M
M
D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D002452:Cell Count; D002455:Cell Division; D018920:Coculture Techniques; D016228:Endothelial Growth Factors / Q000096:biosynthesis* / Q000235:genetics; D004730:Endothelium, Vascular / Q000166:cytology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008222:Lymphokines / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000378:metabolism* / Q000473:pathology; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors