Alterations in the structure of extracellular matrix (ECM) play akey role in atherothrombosis. Matrix metalloproteinases (MMPs), afamily of zinc-dependent proteases produced and released by endo-thelial and smooth muscle cells, monocytes and platelets, degradeECM. There is evidence that MMPs are involved in cardiovascular dis-ease [1,2], but also in inflammatory disorders of the respiratory, gas-trointestinal, osteoarticular and central nervous systems [3].Plasma levels of some MMPs, and in particular of MMP-2, havebeen established as biomarkers of cardiovascular risk [1,2], but theyhave also been found to be increased in connective tissue disorders,likerheumatoidarthritis,systemiclupuserythematosusandSjogren'ssyndrome [3].No data are available instead on plasma MMPs in the anti-phospholipid syndrome (APS), an autoimmune condition characterizedby the occurrence of thrombotic events or pregnancy complications as-sociated with antiphospholipid antibodies (aPL). Among thromboticmanifestations of APS, both arterial and venous thrombosis may occur.However, so far no features have been identi fied distinguishing APS pa-tients undergoing arterial thrombotic events versus those developingvenous thromboembolism (VTE).AimofthepresentstudywastoexplorewhetherplasmaMMP-2isincreased in APS patients and to test if this marker can identifypatients undergoing arterial versus venous thrombosis.77 patients with APS (both primary and secondary), definedaccording to the international consensus criteria [4], (48 females,mean age 47±8 years), and 69 age- and sex-matched healthy con-trols (40 females, mean age 45±7 years) without concomitant riskfactors for cardiovascular disease, enrolled in two previously pub-lishedstudies[5,6], wereincluded inthepresentstudy.OftheAPSpa-tients,30 (22primaryand 8 secondary)(39%)had ahistoryof arterialthrombosis (mean time from event: 3.7±3 years), 41 (53%) (29 pri-mary and 12 secondary) a history of VTE (mean time from event:5±3 years) and six (8%) had obstetric manifestations. A group of pa-tients with history of arterial thrombosis (n=30, 16 females, 7 MI,5 stroke, 18 PAD) but no APS was alsostudied to distinguishthe role ofMMP-2 as a marker of vascular disease per se from a specific increaselinked to APS. Informed consent was obtained from each patient andthe study protocol, conformed to the ethical guidelines of the Declara-tion of Helsinki, was approved by the Local Ethic Committees (deliber-ation number 433/03). The authors of this manuscript have certifiedthattheycomplywiththePrinciplesofEthicalPublishingintheInterna-tional Journal of Cardiology.Plasma, obtained by centrifugation of 3.8% citrated venous bloodat 3000 g for 20 min, was immediately frozen and stored at −80 °Cfor later assay of MMP-2 by zymography, as described [7]. Intra-and inter-assay coefficients of variation of MMP-2 measurementswere 2.3% and 3.9%, respectively (n=8). All measurements were car-ried out by investigators blinded as to the patients' characteristics.The association of MMP-2 levels with history of arterial or venousthrombosis was evaluated by binary logistic regression analysis.Odds ratio (OR) and 95% confidence intervals (CIs) were calculatedconsidering the thrombotic event (arterial vs venous) as dependentvariable. Independent variables were: MMP-2 levels and age as con-tinuous variables, and sex (male vs female), oral anticoagulation(yes/no) and triple positivity for aPL (LAC, ACA, anti-β2GPI) (yes/no), as dichotomous variables. A two-sidedp-valueb0.05 was consid-ered as statistically significant. All analyses were performed with thestatistical package SPSS for Windows.PlasmaMMP-2wassignificantly higher in APSpatientsthanin con-trol subjects (Fig. 1A). When further subdivided in relation to clinicalmanifestations, MMP-2 levels were significantly higher in patientswith a previous arterial event than in patients with a previous VTE orin healthy controls (Fig. 1B). APS patients with obstetric manifesta-tions had MMP-2 levels similar to those of patients with VTE(740.9±94.2 ng/ml). MMP-2 levels in patients without APS but withprevious arterial thrombosis were higher than controls (682.6±84.3
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