CONTRACTION OF HUMAN BRAIN ENDOTHELIAL-CELLS INDUCED BY THROMBOGENIC AND FIBRINOLYTIC FACTORS - AN IN-VITRO CELLS CULTURE MODEL

Background and Purpose Vasogenic brain edema is a frequent complicatio n of ischemic stroke. The mechanism of the blood-brain barrier opening that underlies the edema formation is poorly understood. In the prese nt study we examined the response of endothelial cells cultured from a dult human brain to thrombogenic and fibrinolytic factors that possibl y accumulate in the occluded vascular segments in ischemic stroke. Met hods The changes in the morphology of cultured human brain microvascul ar endothelial cells were observed by phase-contrast light microscopy and quantified with computerized morphometry. Results Active proteases (eg, thrombin, plasmin, urokinase) as well as heparin and protamine, but not fibrinogen and antithrombin III, produced significant changes in endothelial cell morphology. Two shape patterns of contraction were observed: protamine treatment resulted in rounded cells with a decrea se in both cell perimeter and area, whereas all other agents induced s piderlike cell morphology with increased perimeter and reduced area. T he rate of contraction was dose dependent, and at comparable enzyme co ncentrations plasmin produced faster contraction than thrombin. The ob served changes were reversed 3 hours after abrogating the treatment. C onclusions In an in vitro model we have demonstrated that factors invo lved in thrombus formation and dissolution induce endothelial cell con traction, which could affect focally the permeability of the blood-bra in barrier by opening paracellular avenues between endothelial cells i n vivo. Thus, the genesis of brain edema in thromboembolic stroke or o ccasionally during fibrinolytic therapy can be attributed in part to t he contact of these factors with the microvascular endothelium.