Overexpression of vascular endothelial growth factor in restenoticabdominal aorta of rabbits

Objective To investigate the expression of vascular endothelial growth factor (VEGF) in the wall of normal and restenotic abdominal aorta of rabbits. Methods Restenotic model was developed by balloon injured abdominal aorta in eight male New Zealand White rabbits fed with a 2.0%cholesterol diet beginning two weeks before operation and continuing four weeks after procedure. At the end of 4 weeks after injury, the animals underwent total body perfusion fixation. Then, the abdominal aorta from iliac artery root to the diaphragm was harvested and post fixed in 10%neutral formalin for 16 hours. Eight male animals fed with general diet were used for a normal control. The VEGF protein level in normal and restenotic abdominal aorta of rabbits was studied by means of immunohistochemistry. Results VEGF protein was detected in 5 (62.5%) of 8 normal abdominal aorta, 3 showed faint staining, and the remaining 2 showed moderate VEGF expression. VEGF expression at the protein level was identified in all 8 restenotic specimens, 2 showed faint staining, 4 showed moderate staining, and the remaining 2 showed strong VEGF expression. In contrast to normal vessels, VEGF in restenotic specimens was distinctly expressed at sites that contained clustered macrophages and proliferating smooth muscle cells as well as endothelial cells. VEGF immunostaining was more extensive in restenotic specimens (2.00±0.76) than in normal vessels (0.82±0.83, P< 0.01). Microvessels were found in 7 of the 8 restenotic lesions, but only one lesion showed VEGF staining in endothelial cells of the microvessels. Conclusion VEGF expression is consistently more intense in sections of restenotic abdominal aorta than in those of normal abdominal aorta. The VEGF expressed by the smooth muscle cells and foamy macrophages in the restenotic arteries may act as a local and endogenous regulator of endothelial cell functions, including maintenance and repair of luminal endothelium, and formation of intimal neovascularization.

Influence of Stent Implantation on the Expression of PCNA and Apoptosis in Injured Vascular Smooth Muscle Cells

Objectives To evaluate the impact of stent implantation on proliferation and apop-tosis in injured media vascular smooth muscle cells (VSMC) and to explore the mechanism of restenosis after stent implantation. Methods Fifty male New Zealand rabbits were randomized into two groups, including balloon group and stent group. Control group was set up. The samples were harvested on 3, 7, 14, 28, 56 days after operation and the following investigation was carried out: (1) Assessing the expression of proliferating cell nuclear antigen (PCNA) of media VSMC by the method of immunohistochemistry; (2) Analyzing apoptosis of media VSMC by DNA agarose gel electrophoresis and TUNEL technique. Results The expression of PCNA and apoptosis in stent and balloon groups were markedly increased compared with control groups. (1) Stent group induced significant increased expression of PCNA in the media VSMC compared with balloon group on 3 to 28 days. On day 7, the positive rates of PCNA were 24. 36±0. 55 % vs 18. 74±1. 09 % ( P < 0. 01 ); (2) From 3 to 28 days, stent group appeared obvious DNA ladder, while balloon group only had little trace ; (3) TUNEL method showed that stent group induced much more significant apoptosis than that of balloon group on 3 to 28 days. The highest rate of apoptosis appeared on day 7: 12. 42 ±1.13% vs 5. 54±0.53% (P<0. 01); (4) By calculating the ratio of the positive rate of PCNA to apoptosis, it showed that on 3 to 28 days, the ratio of balloon group was higher than that of stent group. There was obvious difference between two groups. Conclusions Stent group induces augmented proliferation and much more significant apoptosis of media VSMC than that of balloon group. It makes the ratio of proliferation to apotosis reduced and the severity of restenosis relieved after stent implantation.