Spatial expression pattern of vascular endothelial growth factor and its receptor mRNA in the early stage of acute focal cerebral ischemia

Kangding LIU; Ping GONG; Xueling MA; Jiang WU; Yulin LI; Mingli RAO

ABSTRACT

BACKGROUND:

Vascular endothelial growth factor (VEGF) can accelerate neovascularization and, as a multifunctional cytokine, performs critical functions via its receptors in angiogenesis.

OBJECTIVE:

To investigate the expression of VEGF and its receptor FLT-1 and FLK-1 mRNA during the early stage of acute focal cerebral brain ischemia, and examine the relationship between the timing and location of their expressions.

DESIGN:

Randomized controlled study.

SETTING:

Department of Neurology of the First Hospital Affiliated to Jilin University and Teaching and Research Section of Pathology, Bethune Medical College of Jilin University.MATERIALS This study was carried out between June 2001 and April 2002. Totally 130 adult SD rats were selected, with male and female in half, and randomly divided into normal control group (n=10), sham operation group (n=10), and cerebral ischemia group (n=110). The rats in cerebral ischemia group were further divided equally into 11 subgroups and examined at 0, 1, 2, 3, 6, 24, 48 hours and 1, 2, 3, 4 weeks after cerebral ischemia model establishment, respectively.

METHODS:

Permanent middle cerebral artery occlusion (MCAO) model was established in rats in cerebral ischemia group by ligation of the left common carotid artery, while the rats in the sham operation group received no artery ligation but with identical other treatments. The rats in the control group did not have any treatment. Reverse transcriptional (RT) PCR was used to detect the expression of VEGF and its receptor mRNA at different time points after ischemic model establishment, and neovascularization in the rats'brain was observed.MAIN OUTCOME

MEASURES:

① Expression of VEGF and its receptor mRNA and ② neovascularization in the brain tissue at different time points of cerebral ischemia.

RESULTS:

Data of the 130 mice were statistically analyzed without losses.At 3, 6, 24, and 48 hours of ischemia, the number of cells positive for VEGF expression was 31.13±2.21, 43.11±2.43, 85.41±2.75 and 98.66±1.76 in each vision filed in the surrounding ischemic region, greater than the numbers in the central ischemic region at the corresponding time points (13.32±1.31, 19.40±3.22, 47.63±2.45, 57.32±3.35 in each vision field, respectively, P ＜ 0.05). VEGF mRNA expression gradually decreased since 48 hours after model establishment till recovering the control level by 2weeks. The expression of VEGF receptor FLT-1 mRNA, determined by the number of positive cells in each vision field at 3, 6, 24, and 48 hour after the ischemia in each vision field for FLK-1 mRNA at these time points in the peripheral ischemic regions, higher than those in the central ischemic regions (P ＜ 0.05), which recovered the control level 3 weeks after the ischemia (P ＜ 0.05). At 48 hours and 1 week after the ischemia, the number of microvessels in each vision field was 47.2±2.11 and 199.2±3.45 in the peripheral ischemic region, significantly higher than the number in the central ischemic region (29.4±2.37 and 76.6±4.62, P ＜ 0.05).

CONCLUSION:

VEGF and its receptors FLT-1 and FLK-1 mRNA are expressed in the neurons, glial cells and endothelial cells during the early stage of acute focal cerebral ischemia, and the expressions are significantly enhanced in response to ischemia, exhibiting temporal and spatial expression patterns.