Quantitative assessment of angiogenesis in murine antigen-induced arthritis by intravital fluorescence microscopy

Inhibition of angiogenesis might be a therapeutic approach to
prevent joint destruction caused by the overgrowing synovial tissue
during chronic joint inflammation. The aim of this study was to
investigate angiogenesis in the knee joint of mice with
antigen-induced arthritis (AIA) by means of intravital microscopy.
In 14 mice (C57BL6/129Sv) intravital microscopic assessment was
performed on day 8 after AIA induction in two groups (controls,
AIA). Synovial tissue was investigated by intravital fluorescence
microscopy using FITC-dextran (150 kD). Quantitative assessment of
vessel density was performed according to the following categories:
functional capillary density (FCD, vessels 10 mum) and FVD of
vessels with angiogenic criteria (convoluted vessels, abrupt
changes of diameter, vessels which are generated by sprouting and
progressively pruned and remodelled). Microvessel count was
performed using immunohistochemistry. There was no significant
difference in FCD between the control group (337 +/- 9 cm/cm(2);
mean +/-SEM) and the AIA group (359 +/- 13 cm/cm(2)). The density
of vessels larger than 10 gm diameter was significantly increased
in animals with AIA (135 +/- 10 vs. 61 +/- 5 cm/cm(2) in control).
The density of blood vessels with angiogenic criteria was enhanced
in arthritic animals (79 +/- 17 vs. 12 +/- 2 cm/cm(2) in control).
There was a significant increase in the microvessel count in
arthritic animals (297 +/- 25 vs. 133 +/- 16 mm(-2) in control).
These findings demonstrate that angiogenesis in murine AIA can be
assessed quantitatively using intravital microscopy. Further
studies will address antiangiogenic strategies in AIA.