Abnormal pattern of Tie-2 and vascular endothelial growth factor receptor expression in human cerebral arteriovenous malformations

OBJECTIVE: Human cerebral arteriovenous malformations (AVMs) are speculated to result from abnormal angiogenesis. Vascular endothelial growth factor receptors (VEGF-Rs) and Tie-2 play critical roles in vasculogenesis and angiogenesis. We hypothesized that the abnormal vascular phenotype of AVMs may be associated with abnormal expression of VEGF-Rs and Tie-2. METHODS: We measured the expression of Tie-2, VEGF-R1, and VEGF-R2 in AVMs and normal brain tissue, using immunoblotting. To assess active vascular remodeling, we also measured endothelial nitric oxide synthase expression. CD31 expression was used to control for endothelial cell mass for Tie-2, VECF-Rs, and endothelial nitric oxide synthase. Immunoblotting data were presented as relative expression, using normal brain tissue values as 100%. RESULTS: CD31 was expressed to similar degrees in AVMs and normal brain tissue (99 +/- 29% versus 100 +/- 20%, mean +/- standard error, P = 0.98). Tie-2 expression was markedly decreased in all AVMs, compared with normal brain tissue (16 +/- 9% versus 100 +/- 37%, P = 0.04). VEGF-R1 expression was decreased in four of five AVMs, but the difference between the mean values was not significant (35 +/- 8% versus 100 +/- 42%, P = 0.14). VEGF-R2 expression was decreased in all AVMs, compared with normal brain tissue (28 +/- 6% versus 100 +/- 29%, P = 0.03). There was no difference in endothelial nitric oxide synthase expression between AVMs and normal brain tissue (106 +/- 42% versus 100 +/- 25%, P = 0.91). CONCLUSION: AVM vessels exhibited abnormal expression of Tie-2 and VECF-Rs, both of which may contribute to the pathogenesis of AVMs.