Antiphospholipid antibodies and recurrent abortions: possible pathogenetic role of annexin A5 investigated by confocal microscopy

AIM: It has been established that antiphospholipid antibodies (aPL) are associated with recurrent abortions, but the pathophysiologic mechanisms that characterize thrombosis and recurrent pregnancy losses are still not clear.However, it is known that they are associated with the presence of antibodies directed against anionic phospholipids and putative cofactors. In this study the pathogenetic role of annexin A5, a potent anticoagulant cofactor protein for its anticoagulant property in recurrent abortions, was investigated. METHODS: Endothelial cells of human umbilical veins 'EAHY2936 Line' in culture were used, incubated with antiphospholipid anticardiolipin (ACA) antibodies purified from plasma of patients with recurrent abortions. The expression of annexin A5 on the cells with ACA was investigated by immunofluorescence and by confocal microscope. The negative control was also carried out: EAHY cells in cultivation medium without ACA. RESULTS: Confocal analysis revealed a uniform distribution of annexin A5 on the cellular membranes in the negative control. Instead, in EAHY cells with ACA, the annexin A5 appears distributed in irregular manners on the cellular membranes (cytoplasmic and nuclear). CONCLUSION: The results of an irregular 'cluster' distribution of annexin A5 on the EAHY cells in presence of aPL, and in agreement with the literature, demonstrated that aPL, inhibiting annexin A5 ability to protect anionic phospholipid, promote the coagulation factors to diffuse laterally against phospholipids.