Osteopontin expression and its possible functions in the aortic disorders and coronary artery disease

Abstract

Osteopontin (OPN) has been verified to be closely associated with oncogenesis and remodeling processes. But this cytokine was rarely assessed in the presence of aortopathies, especially acute aortic dissection. The aim of the present study was to evaluate the expressions of OPN by way of molecular biological approaches so as to offer a better understanding of the possible mechanisms of the aortopathies. Consecutive patients with type A acute aortic dissection (20 patients), aortic aneurysm (nine patients) or coronary artery disease (21 patients) referred to this hospital for surgical operations were enrolled into this study. Blood samples of the surgical patients after systematic heparinization, and control fast morning blood samples drawn from 21 young healthy volunteers who had no evidence of any healthy problems were investigated for enzyme linked immunosorbent assay (ELISA). The surgical specimens of the aortic tissues collected from the surgical patients during the operations were obtained for quantitative realtime reverse transcription polymerase chain reaction (RT-PCR) for OPN mRNA, western blot assay for OPN protein, and for immunohistochemical staining of OPN. Ascending aortic tissues from the autopsies of the healthy individuals dying of accident were obtained as controls of immunohistochemistry. By quantitative RT-PCR, the expressions of OPN mRNA were all upregulated in all three surgical groups. The quantitative results did not reveal any intergroup differences. Western blot assay revealed that OPN was positive with similar intensities of expressions in all three surgical groups. Quantitative western blot analyses of OPN expressions did not show any significance between groups. The OPN expressions by ELISA in the aortic tissue were 3.09311 ± 1.65737, 3.40414 ± 1.15095, and 1.68243 ± 0.31119 pg/mg protein in the aortic dissection, aortic aneurysm, and coronary artery disease groups, respectively. The OPN level of the patients with coronary artery disease was much lower than those with aortic dissection (P = 0.033) or with aortic aneurysm (P = 0.019). By unparametric tests, there were significant differences in the aortic OPN contents among aortic dissection, aortic aneurysm and coronary artery disease groups (P < 0.01). A significant direct correlation was present between plasma OPN concentration and the time interval from the onset to surgery of aortic dissection (Y = 0.1420X + 2.4838, r² = 0.5623, r = 0.750, P = 0.032). By immunohistochemistry, OPN was expressed in the aortic cells: in the intima, it was weaker in all three surgical groups in comparison with the healthy control; in the media, it was weak in the aortic dissection, intense positive in aortic aneurysm, focal positive in the coronary artery disease, but evenly positive in the healthy control groups; and in the adventitia, it was positive in the aortic dissection, coronary artery disease and healthy control groups, but weak positive in the aortic aneurysm group. These data may provide evidences that OPN may play a role in the pathogenesis of aortopathies including aortic dissection, aortic aneurysm, and coronary artery disease. OPN might be of potential perspective as a clinically diagnostic tool in the evaluations of the complex remodeling process incorporating vascular injury and repair.