Extraction of lipoprotein(a), apo B, and apo E from fresh human arterial wall and atherosclerotic plaques

Abstract

Several studies have analysed apo(a) quantitatively in arterial wall tissue derived from post mortem samples. The purpose of this study was a qualitatative analysis of Lp(a) in fresh human arterial wall tissue. It was evaluated whether Lp(a) exists as an intact lipoprotein or whether it is degraded. Additionally it was analysed whether there are differences in the apolipoprotein composition between lesion-free and diseased human arterial wall tissue. Serum and intimal tissue samples taken from the abdominal aorta and the inferior caval vein of 18 organ donors were analysed for lipids, Lp(a), and apolipoproteins apo B and apo E. Serum and tissue parameters were correlated. In the aortic tissue, higher Lp(a) and apolipoprotein levels were observed in the diseased samples. The total amount of Lp(a) recovered during three different extraction procedures was 5 μg/g wet weight in tissue free of plaque and 11.8 μg/g wet weight in atherosclerotic tissue. The corresponding values for apo B and apo E were 4.3 and 6.1 μg/g wet weight vs. 5.0 and 9.1 μg/g wet weight. After density gradient centrifugation of the aortic tissue extracts, it was shown that the major parts of apo(a) and apo B detected in the lesion-free vessel wall were present as Lp(a)-like particles. In the diseased tissue Lp(a) was partly dissociated into LDL-like particles and free apo(a). With this study we confirm that Lp(a) accumulates in the arterial wall, preferentially in diseased tissue, and that Lp(a) particles, deposited in atherosclerotic plaques, are partly degraded to LDL-like particles and free apo(a) in atherosclerotic plaques.