The Role Of Differential Expression Of TGF-β1 And Elastin Metabolism For Thoracic Aortic Dissection Versus Aneurysm In Pathogenesis Mechanism Of Thoracic Aortic Dissection

Part IComparison of TGF-β1 Distribution and Expression in Aortic Wall of Thoracic Aortic Dissection versus Thoracic Aortic Aneurysm PatientsBackgrouds-Transforming Growth Factor (TGF)-β1 has been documented as one of pivotal multi-functional cytokines modulating the remodification of extracellular matrix and inflammatory process, and acted as a key role in mechanism of diseases involving connective tissue disorder. This study is in aim to explore the possible role of TGF-β1 in the mechanism of thoracic aortic dissection (TAD) by comparing the distribution and expression of TGF-β1 in the aortic wall of TAD versus thoracic aortic aneurysm (TAA) patients.Material and Method Aortic specimens were obtained from patients underwent aortic procedures for TAD (n=20) and TAA (n=38) in our institute and organ donor (n=20) as control. Histopathologic examination was performed with hematoxylin-eolin, Verhoeff van-Gieson and Masson's trichrome stain. Double immunofluorescent staining of TGF-β1 andα-smooth muscle actin was performed with paraffin embedded slides for all aortic samples and semiquantified by fluorescent intensity analysis. Expression and distribution of TGF-β1 within aortic wall were compared for TAD versus TAA patients, and the correlation between the distribution of TGF-β1 and elements of extracellular matrix were analyzed.Results Histopathologic examination results characterized with mild to severe cystic medial degeneration were found in 17(85%) TAD and 29(76.3%) TAA patients. Morphologically, TAD was characterized with attenuated and disarrayed fragments of elastic lamellae and hyperplastic collagen in media. TGF-β1 distributed unevenly across aortic wall with the highest expression level in tunica media, followed by intima then adventitia in all groups. In whole aortic wall, TGF-β1 exhibited with 70.71±9.7 in TAD specimens,77.66±10.93 in TAA and 64.54±5.18 in control with an up-regulation of 9.56% and 20.3% for TAD and TAA compared to control(P<0.05). As for the distribution within aortic wall, at media, TAD patients exhibited with 79.26±12.77, TAA with 86.82±13.47 and control with 68.28±7.98, higher level of 16.09% and 27.2% for TAD and TAA than control(P<0.01). At adventitia, TGF-β1 expression was 60.04±12.07 in TAD,61.52±18.29 in TAA and 51.43±8.09 in control, a 16.74% and 19.6% up-regulation than control(P<0.05), while no difference was detected between TAA and TAD. At intima, TGF-β1 expression was 62.54±8.81 in TAD,72.14±15.85 in TAA and 62.63±6.12 in control, TGF-β1 increased by 15.18% for TAA compared with control (P<0.05), no difference was detected between TAD and control. TGF-β1 distribution histogram analysis disclosed TGF-β1 condensed at the elastic lamella in media and expressed higher level by 34.83% in TAD patients compared to control (p<0.01). No significant difference of TGF-(31 expression was detected referring age, gender, maximal aortic diameter and type of dissection for TAD patients. Nucleus density analysis revealed significantly higher cellular density in intima and adventitia for TAD than TAA patients (P<0.05).Conclusions TGF-β1 expression is unevenly distributed in aortic wall and up-regulated in TAD and TAA compared to control. The significant up-regulation in media and condensed in the elastic lamella, implicates a crucial role of TGF-β1 in evolution of TAD.PartⅡExpression and regulation of synthesis on elastin for thoracic aortic dissection versus thoracic aortic aneurysmBackgrounds-Aortic elastic fiber network within aortic tunica media is crucial to maintain the integrity of the aortic wall and resist the pulsatile stress to aortic wall. Elastin constitutes the main component of elastic fibers. Piles of researches have documented significant degradation of elastic fibers caused by activing of MMP/TIMP system in the thoracic aortic dissection and aneurysm. For mature elastin fiber, there is a balance between continuous degradation and repair by deposition of microfiber and elastin. Yet little study on elastin synthesis in thoracic aortic dissection has been reported. Herein we explore the mechanism of thoracic aortic dissection by comparing the expression and synthesis of elastin between TAD and TAA aortic tissue.Material and Method Aortic specimens were obtained from patients underwent aortic procedures for TAD (n=10) and TAA (n=10) in our institute and organ donor (n=10) as control. Total protein and total RNA were extracted and preserved from fresh operative aortic specimen. Expression level of elastin of TAD and control was detected and semi-quantitative by western-blotting technique. Elastin mRNA of TAD, TAA and the control group were analyzed with fluorescence quantitative RT-PCR, GAPDH served as internal reference.Results Expression of elastin by western-blotting for 8 TAD patients and 8 control demonstrated a decrease of elastin in TAD than control, mean level of 0.807±0.159 for TAD to 1.194±0.187 for control, with a down-regulation of 32.42%(P<0.001). As for elastin mRNA, TAD group was significantly reduced comparing to that of TAA and control group, with mean level of 3.95±2.07 for TAD,28.32±12.95 for TAA group and 29.71±8.65 for control group. A down-regulation of 86.70% for TAD compared to control group (P<0.01). While no difference was detected between TAA and control mRNA level (P>0.05).Conclusions Besides elastin fiber degradation, expression of elastin and elastin mRNA were significant reduced for TAD than TAA and control。While elastin synthesis remained normal for TAA compared to control, which suggesting the disorder of elastin synthesis and repair contribute to the arise of TAD.