Immunohistochemical detection of liporpotein(a) in the wall of plancetal bed spiral arteries

Objective: Lipoprotein(a) [Lp(a)] has been localised in the wall of atherosclerotic coronary arteries. Pre-eclampsia is associated with an increased incidence of atherotie lesions in the placental bed spiral arteries. This study was undertaken to determine if Lp(a) is present in these atherotie lesions and in the walls of spiral arteries that have undergone physiological and other pathological changes in pregnancy. Methods: 116 spiral arteries were studied in 42 placental bed biopsies taken from 18 normal and 24 severe pre-eclamptic pregnancies. Standard histology (H&E, PAS) and immunohistochemicai staining using a streptavidin-biotin system (Zymed No. 95-6543) with a monoclonal antibody to apolipoprotein (a), [Lp(a)], (Cappel clone 2-D1) were carried out. Controls were atherosclerotie coronary artery, TBS and a monoclonal antibody to cytokeratin. The amount of Lp(a) detected was scored as negative, faint, light, moderate and heavy. Results: Lp(a) was detected in all spiral arteries with atherosis and necrosis, in 57% with disorganisation or hyperplasia and in 45% with physiological change. 12 spiral arteries did not show any morphological change and Lp(a) was not detected in these. When Lp(a) was detected there was a trend in the amount seen between spiral arteries showing these features: it was most in atherotie vessels, less in areas of necrosis, less still in vessels with medial change and least in vessels with physiological change. In normal pregnancies the amount of Lp(a) when detected was generally less than in the severe pre-eclamptic group for the same category of vascular change. Conclusions: Immunostaining for Lp(a) was sensitive in demonstrating areas of atherosis and necrosis and as a marker may help to distinguish between physiological and atherotic fibrinoid. The prothrombotic property of Lp(a) may play a role which leads to the increase placental infarction seen in pre-eclampsia.