Transforming growth factor-β/Smad signaling function in the aortopathies.

OBJECTIVES

Transforming growth factor (TGF)-β/Smad signaling pathway in aortic dissection patients and normal subjects has not been previously described. The present study was designed to evaluate the TGF-β/Smad signaling expressions in the patients with acute type A aortic dissection in comparison with those in the patients with thoracic aortic aneurysm and with coronary artery disease, and (or) the healthy subjects.

METHODS

Consecutive surgical patients for acute type A aortic dissection (20 patients), aortic aneurysm (nine patients) or coronary artery disease (20 patients) were selected into this study. Blood samples (4 ml) were obtained from the right radial arterial indwelling catheter after systemic heparinization prior to the start of cardiopulmonary bypass in the operating room. Twenty-one young healthy volunteers without underlying health issues who donated forearm venous blood samples (4 ml) were taken as control. The surgical specimens of the aortic tissues were obtained immediately after they were severed during the operations of the replacement of the aorta in the patients with aortic dissection or aortic aneurysm. In patients receiving coronary artery bypass grafting, the tiny aortic tissues were taken when the punch holes of the proximal anastomosis on the anterior wall of the ascending aorta were made. The aortic tissues were for RNA, protein, or supernatant preparations until detection of TGF-β1 mRNA by quantitative real-time reverse transcription polymerase chain reaction, of TGF-β1, TGF-β receptor I, Smad2/3, Smad4 and Smad7 by Western blot, and of TGF-β1 by enzyme-linked immunosorbent assay, respectively. In particular, the linear correlations of the relative grayscales between different proteins of each group, and those correlations between the quantitative TGF-β1 by enzyme-linked immunosorbent assay and the time interval from the onset to surgery or the maximal dimensions of the aorta of the aortic dissection group were assessed.

RESULTS

Quantitative real-time reverse transcription polymerase chain reaction showed that TGF-β1 mRNA were upregulated in all surgical groups (1.59 ± 0.33 vs. 1.45 ± 0.34 vs. 1.48 ± 0.48, P > 0.05). Western blot revealed that the expressions of TGF-β1, TGF-β receptor I, Smad2/3, Smad4 and Smad7 were positive in the aortic tissues of all three investigated groups. Of the quantitative relative grayscales, a significant reverse correlation was noted between TGF-β1 and Smad2/3 (Y = -0.8552X + 1.6417, r = -0.759, P < 0.0001), and a close direct correlation between Smad4 and Smad7 (Y = 0.5905X + 0.2805, r = 0.781, P < 0.0001) in the Aortic Dissection Group. In the Aortic Aneurysm Group, Smad4 and Smad7 were also closely correlated (Y = 0.5228X + 0.1642, r = 0.727, P = 0.026), and in the Coronary Artery Disease Group, TGF-β1 and Smad7 were much significantly correlated (Y = 0.5301X + 0.5758, r = 0.917, P = 0.004). By enzyme-linked immunosorbent assay, TGF-β1 level of the aortic tissue was lower in the aortic dissection than in the aortic aneurysm and coronary artery disease groups with no statistical significance (319.52 ± 129.21 pg/mg protein vs. 324.09 ± 49.70 pg/mg protein vs. 304.15 ± 29.39 pg/mg protein, P > 0.05). The plasma TGF-β1 levels were 1158.30 ± 11.54 pg/ ml, 1170.27 ± 8.26 pg/ml, 1225.00 ± 174.42 pg/mL and 1160.25 ± 13.01 pg/mL in the four groups, respectively, showing significant intergroup differences (P < 0.05). No significant correlation was found between the aortic or plasma TGF-β1 levels and the time interval from the onset to surgery or the maximal dimensions of the aorta in the patients of the aortic dissection group.

CONCLUSIONS

Aortic dissection, aortic aneurysm and atheroslerosis might be associated with an enhanced TGF β/Smad signaling function, with aortic dissection exhibiting a less prominent upregulation. It might have implications for downstream signal activation presumably translating into matrix degradation in the condition of aortic dissection in comparison to matrix deposition in aortic aneurysm and coronary artery disease.