Microvascular network remodeling in dura mater of ovariectomized pigs: role for angiopoietin-1 in estrogen-dependent control of vascular stability.

Estrogen is a key regulator of vascular responses and angioadaptation in multiple organs and tissues, including brain. However, the consequences of a loss of ovarian steroid hormone secretion on the status of microvascular networks in brain and meninges are largely unknown. Here, using the perfused dura mater model coupled with high-resolution digital epifluorescence and laser scanning confocal microscopy and computer-assisted morphometric analysis, we demonstrate that cessation of ovarian hormone production causes dramatic vascular remodeling in meningeal microvascular networks characterized by a threefold decrease in microvessel density and capillary rarefaction and an almost fourfold increase in vascular permeability. These changes were accompanied by a significant decrease in angiopoietin-1 (Ang-1) expression and Ang-1/Tie-2 ratio (1.4-fold, P < 0.01, and 1.5-fold, P < 0.05, respectively) in ovariectomized animals compared with intact females, but no changes were detected in the expression of estrogen receptors (ER)-alpha and -beta. We conclude that estrogen-dependent control of Ang-1 expression plays an important role in stabilizing meningeal microvessel and maintaining healthy microvascular networks.