VEGF release is associated with reduced oxygen tensions in experimental inflammatory arthritis.
OBJECTIVE
The contribution of local VEGF production and subsequent angiogenesis within the synovial membrane to the propagation of arthritis is unclear. The relationship between synovial oxygenation and blood flow in the development of arthritic disease is unknown. We have therefore measured oxygen levels and perfusion rates in the synovial space in a murine model of arthritis.


METHODS
Arthritis was induced in DBA/1 mice by immunisation with type II collagen. Oxygen and perfusion levels were measured polarographically using silver needle microelectrodes within the knee joints prior to and 10 days after the onset of arthritis. In addition, synovial cells were isolated from knee joints of naive, pre-arthritic and arthritic mice.


RESULTS
Onset of arthritis was associated with a marked reduction in synovial oxygen tensions (pO2). The perfusion rates in naive and arthritic animals were not significantly different: in naive mice, the rate was 0.58 +/- 0.11 ml/min/g and in arthritic joints, 0.64 +/- 0.17 ml/min/g. Furthermore, synovial cells isolated from the knee joints of naive animals did not express mRNA for VEGF, but significant levels were detected in cells from non-arthritic mice immunised with collagen. The onset of arthritis was associated with expression of VEGF mRNA and protein, and correlated negatively with pO2 levels.


CONCLUSIONS
These data demonstrate that decreases in intra-articular pO2 occur in established arthritic conditions and may be the stimulus for local VEGF production. However, perfusion was not increased in arthritic animals and vascular density was unaltered, suggesting that the neovascularisation associated with inflammatory arthritis, is insufficient to restore oxygen homeostasis in the joint.
Etherington
P J
PJ
Kennedy Institute of Rheumatology Division, Imperial College School of Medicine, London, UK.
Winlove
P
P
Taylor
P
P
Paleolog
E
E
Miotla
J M
JM
D000818:Animals; D001169:Arthritis, Experimental / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D024043:Collagen Type II / Q000276:immunology; D016228:Endothelial Growth Factors / Q000235:genetics / Q000378:metabolism*; D005620:Freund's Adjuvant / Q000276:immunology; D007091:Image Processing, Computer-Assisted; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007596:Joints / Q000378:metabolism / Q000473:pathology; D008222:Lymphokines / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008839:Microelectrodes; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D010101:Oxygen Consumption; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011048:Polarography; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D024043:Collagen Type II; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D005620:Freund's Adjuvant; D010100:Oxygen