TISSUE FACTOR EXPRESSION ON MACROPHAGES IN CORONARY PLAQUES IN PATIENTS WITH UNSTABLE ANGINA

Tissue factor is a membrane-bound glycoprotein that functions in the e xtrinsic pathway of blood coagulation by acting as a cofactor for fact or VII, and the resulting complex leads to thrombin production in vivo . The purpose of the present study is to determine whether macrophages express tissue factor in human coronary atherosclerotic plaques. We e xamined directional coronary atherectomy specimens from 24 patients wi th unstable angina and 23 with stable exertional angina. In these spec imens, macrophages were detected in 22 (92%) of 24 patients with unsta ble angina versus 12 (52%) of 23 with stable exertional angina (P=.003 ). The percentage of macrophage infiltration area was significantly la rger in patients with unstable angina than in those with stable exerti onal angina (17+/-3% versus 6+/-2%, P=.008). The immunohistochemical d ouble staining revealed the expression of tissue factor on macrophages in 18 (75%) of 24 patients with unstable angina versus 3 (13%) of 23 with stable exertional angina (P<.0001). Thrombus was identified in 20 (83%) of 24 patients with unstable angina versus 12 (52%) of 23 with stable exertional angina (P=.02). Fibrin deposition was mainly observe d around macrophages expressing tissue factor in the patients with uns table angina. We have shown that tissue factor expression on macrophag es was more frequent in coronary atherosclerotic plaques in patients w ith unstable angina. Tissue factor expressed on macrophages may play a n important role in the thrombogenicity in coronary atherosclerotic pl aques of these patients.