Figure 4

Up-regulation of markers of angiogenesis in the surgically-induced models of joint instability. (A) Induction of angiogenesis gene expression marker, VEGF, was seen at 2-wk post-surgery in both models. Levels of VEGF increased approximately 2 fold at week 2, maintained expression during wk 4 and 6 and returned to Sham levels by week 10. All values are shown as mean ± SD. (B) Frontal section of medial tibial plateau and growth plate were stained with anti-VEGF (blue) and anti-KDR (brown). (a) At 2-wk post-surgery, many chondrocytes differentiated to hypertrophic chondrocytes in ACLT+MMx joint. (b) Higher magnification of inset in (a) showed that hypertrophic chondrocyte-like cells strongly stained with VEGF (arrowheads). KDR (brown) positive cells are found in proximity with VEGF-positive cells (arrow). (c) Sham joint shows a few VEGF-positive cells in deep zone of articular cartilage (arrowheads). Vascular endothelial cells are positive for KDR in bone marrow, but not in proximity with VEGF-positive cells (arrows). (d) Negative control shows no specific staining. C: articular cartilage. B: bone. V: vascular invasion. Bar = 200 μm in (a, c and d); and 100 μm in (b).