【作者】 陈晓锋；

【导师】 王建安；

【作者基本信息】 浙江大学 ， 心血管内科， 2009， 博士

【摘要】 主动脉扩张性疾病(aortic aneurysmal diseases)即主动脉瘤，发病率呈逐年上升趋势，按照病理分型可分为真性动脉瘤、主动脉夹层(aortic dissecting，AD)和假性动脉瘤，按部位可分为胸主动脉瘤(Thoracic aortic aneurysm)和腹主动脉瘤(Abdominal aortic aneurysm)。主动脉瘤的确切病理机制目前尚不清楚。主动脉瘤已报道的相关危险因素有男性、高血压、吸烟、遗传结缔组织病等，一般认为动脉瘤的产生是动脉壁因各种原因发生的薄弱和改变的血流动力学相互作用的结果。新的危险因素和潜在的可能的其他发病机制有待进一步研究。血管细胞外基质(extracellular matrix proteins，ECMs)可被基质金属蛋白酶(matrix metalloproteinases，MMPs)等蛋白酶降解、破坏，导致动脉中膜受损、血管重构，动脉壁失去弹性，不能耐受血流冲击逐渐膨大形成动脉瘤。细胞外基质金属蛋白酶诱导子(Extracellular matrix metalloproteinase inducer，EMMPRIN)通过促进MMPs的表达而在细胞外基质重构中起重要作用。然关于EMMPRIN与主动脉瘤关系的研究国内外尚未见报道。本课题旨在：(1)以主动脉夹层患者及主动脉瘤高危人群为研究对象，结合超声多谱勒等检查，分析主动脉夹层、腹主动脉扩张、主动脉根部扩张的危险因素，并与传统动脉硬化危险因素比较，分析动脉瘤和动脉粥样硬化性疾病发病危险因素的异同点，探索动脉扩张性疾病新的危险因素。(2)以人主动脉瘤和人主动脉平滑肌细胞为研究对象，结合分子生物学技术，分析EMMPRIN与主动脉扩张性疾病的相关性，初步探讨主动脉扩张性疾病的发病机制。第一部分主动脉扩张性疾病的危险因素分析研究背景：我国在主动脉扩张性疾病的流行病学研究方面尚刚刚起步。结合我国人群特征，寻找国民动脉瘤高危人群，分析动脉瘤和动脉硬化危险因素的异同点，并探索动脉扩张性疾病新的危险因素，对今后开展针对性的防治工作及提高主动脉瘤的救治率具有重要价值。(一)主动脉夹层的危险因素分析—脂蛋白(α)与动脉夹层的相关性研究方法：以52例主动夹层患者为研究对象，检测常规血脂[总胆固醇(totalcholesterol)，高密度脂蛋白胆固醇(high-density lipoprotein，cholesterol,HDL-C)，低密度脂蛋白胆固醇(low-density lipoprotein cholesterol,LDL-C)，甘油三脂(triglycerides,TG)]，血肌酐(creatinine)、尿酸(uric acid)水平及血脂蛋白(a)[Lipoprotein(a)]等水平，并以104例年龄和性别匹配的健康者为对照组。用多因素logistic回归分析等统计方法分析主动脉夹层的可能危险因素。结果：(1)主动脉夹层患者中男性及高血压患者高于对照组；血TG低于对照组；血脂蛋白(a)水平高于对照组。(2)血脂蛋白(a)在非吸烟主动脉夹层患者明显高于吸烟患者；多元logistic回归分析表明血脂蛋白(a)是非吸烟患者发生主动脉夹层的独立危险因素(p＜0．05)。(二)中国老年冠心病人群腹主动脉瘤的发病率调查方法：以209例大于60岁的冠心病患者为研究对象，以260例非冠心病患者为对照，调查两组人群腹主动脉瘤的发病情况。结果：老年冠心病人群腹主动脉瘤的发病率为0．44％，而非冠心病人群腹主动脉瘤的发病率为0．77％，两组差别无统计学意义(p＞0．05)。(三)腹主动脉扩张的危险因素分析—嗜酒、血脂、脂蛋白(α)与腹动脉直径的相关性研究方法：以395例(平均年龄66．6±10．3岁)并有动脉硬化性疾病或传统心血管危险因素的患者为研究对象，超声检测腹主动脉直径，以多因素线性回归等统计方法分析腹主动脉直径与烟酒史、糖尿病、血压、血脂(HDL-C、LDL-C、TC、TG、ApoAI、Apo B)及脂蛋白(a)等的相关性。结果：身高、嗜酒、吸烟、慢性阻塞性肺病(Chronic obstructive pulmonary disease，COPD)、脂蛋白(a)与肾下主动脉直径呈正相关，而糖尿病、LDL-C／HDL-C，LDL-C和TC／HDL-C增高则是腹主动脉直径扩张的负性预测因子(p＜0．05)。(四)主动脉根部扩张的危险因素分析—糖尿病可否阻止升主动脉根部扩张？方法：以109例2型糖尿病患者和218例年龄、性别匹配的非糖尿病患者为研究对象，超声检测主动脉根部直径的四个水平：①主动脉瓣环；②瓦氏窦最大直径；③主动脉上嵴(窦管结合处)；④近段升主动脉(主动脉管部)，利用多元回归分析主动脉根部扩张及直径与年龄、性别、糖尿病、空腹血糖、血脂、血压、烟酒史等的相关性。结果：糖尿病与主动脉根部扩张呈负相关，是主动脉根部各水平直径的独立负性预测因子；而年龄、身高、高血压与主动脉根部直径呈正相关。第一部分结论：主动脉扩张性疾病与动脉粥样硬化性疾病的危险因素既存在相同点，也有差异之处：1．中国老年冠心病人群腹主动脉瘤的发病率明显低于国外报道的高加索人群的发病率，是否与种族差异有关有待进一步研究。2．Lp(a)是主动脉夹层的独立危险因素，并与腹主动脉直径呈正相关。3．嗜烟、嗜酒、COPD与腹主动脉直径扩张呈正相关；而LDL-C／HDL-C，LDL-C和TC／HDL-C与腹主动脉直径呈负相关。4．糖尿病是主动脉根部及腹主动脉直径扩张的负性预测因子。第二部分主动脉扩张性疾病发病机制的探讨—EMMPRIN在人主动脉瘤中表达升高并可被血管紧张素Ⅱ诱导研究背景：主动脉瘤的确切病理机制目前尚不清楚，血管细胞外基质(extracellularmatrix proteins，ECMs)始终处于合成、降解的动态平衡中，在维持主动脉正常组织结构与功能中起着非常重要的作用。细胞外基质可被MMPs等蛋白酶降解、破坏，导致动脉中膜受损、血管重构，动脉壁失去弹性，不能耐受血流冲击逐渐膨大形成动脉瘤。本文第一部分研究提示，Lp(a)、嗜烟、嗜酒、COPD与主动脉直径呈正相关，而糖尿病则与主动脉直径呈负相关。结合以往文献报道，Lp(a)、烟、酒、COPD和糖尿病可能通过影响血管MMPs的水平而与主动脉扩张性疾病相关。EMMPRIN可由血管平滑肌细胞合成，EMMPRIN通过促进MMPs的表达而在细胞外基质重构中起重要作用。然关于EMMPRIN与主动脉瘤关系的研究国内外尚未见报道。方法：以41例外科胸主动脉瘤(Thoracic aortic aneurysm，TAA，n=26)和腹主动脉瘤(abdominal aortic aneurysm，AAA，n=15)标本为研究对象，其中TAA包括Stanford A型胸主动脉夹层(Type-A aortic dissection，n=12)；Stanford B型胸主动脉夹层(Type-B aortic dissection，n=7)；无夹层的胸主动脉瘤(TAA without dissection，n=7)。并以12例无主动脉瘤的尸解主动脉标本为对照，免疫组化半定量法分析EMMPRIN与主动脉瘤的相关性。以体外培养入主动脉平滑肌细胞(human aorticsmooth muscle cells，HASMC)，Western Blotting分析血管紧张素(Angiotensin，Ang)Ⅱ刺激对HASMC中EMMPRIN的表达的影响。结果：主动脉瘤中EMMPRIN表达明显增高，主动脉平滑肌细胞是主要的表达部位。并有夹层的TAA中EMMPRIN过表达率(68．4％)明显高于不并有夹层的TAA(14．3％)(P=0．026)。AngⅡ可刺激体外培养的HASMC中EMMPRIN的表达，此效应可被除AngⅡ1型受体(receptor type 1，AT1-R)拮抗剂氯沙坦(losartan)抑制。结论：EMMPRIN表达异常可能与主动脉扩张性疾病的发病密切相关。EMMPRIN是否是主动脉瘤危险因素与主动脉瘤发病的中间关键蛋白，从而可能成为主动脉瘤的潜在治疗靶点，有待进一步研究。更多还原

【Abstract】 Aortic aneurysms are the major disease processes affecting the aorta and becominga relatively common cause of death because of rupture or dissection. Early recognitionand management are crucial.The most common location for aneurysms is the infrarenalabdominal aorta, followed by the ascending thoracic aorta.The aim of this study was to investigate the risk factors of aortic aneurysmaldieases and the possible underlying mechanism. Firstly, we detected the independentrisk facoters for aortic aneurysmal diseases (including aortic dissection, abdominalaortic dilatation, aortic root dilatation) in Chinese population, and compare them withthe traditional risk factors of atherosclerostic diseases. Secondly, we determinedwhether EMMPRIN is present and is upregulated in the wall of human TAA and AAA,and to assess possible association with AngⅡ-induced aneurysm formation.PartⅠRisk factors of aortic aneurysmal diseases in Chinese population(一) clinical study of risk factors for aortic dissection—Increased levels of lipoprotein(a) in non-smoking aortic dissection patientsBackground: Aortic dissection (AD) is a life-threatening cause of acute chest, back andabdominal pain. Early recognition and management are crucial. Chronic hypertension,smoking, dyslipidaemia, diabetes, pregnancy, cocaine abuse, inherited connective tissuedisorders and iatrogenic manoeuvres have been shown to cause damage the aortic wall and lead to dissection. Despite extensive research, the mechanisms responsible forinitiating dissection remain elusive. Additional risk factors and potential alternativepathomechanisms for the development of AD need to be further explored. Increasedplasma Lp(a) has been shown to be an independent risk factor for many forms ofvascular disease, including peripheral vascular disease (PVD),ischaemic stroke,coronary artery disease (CAD) and abdominal aortic aneurysm (AAA). However, to thebest of our knowledge, until now, limited data are available on the association of Lp(a)and AD. Methods: An age- and sex-matched case-control study was conducted.HDL-C、LDL-C、TC、TG、Lipoprotein(a)、creatinine and uric acid levels in aorticdissection patients(n=52) and healthy subjects (n=104) were studied. The strength ofassociations between lipids, Lipoprotein(a) serum levels, other risk factors and aorticdissection were assessed by means of multivariate logistic regression analysis. Results:Patients with aortic dissection had significantly higher Lp(a)serum levels (Median,17.6mg/dL; range, 6.4-88.7 mg/dL) compared with healthy individuals (median, 12.4mg/dL; range, 4.9-26.4 mg/dL) (P=0.005). The Lipoprotein(a) concentration innon-smoking aortic dissection patients (median, 19.1 mg/dL, range, 10.5-88.7mg/dL)surpassed significantly that of the smoking aortic dissection patients of comparable age(median, 10.7 mg/dL, range, 6.4-22.1 mg/dL) (P<0.0001). Multivariate analysisconfirmed an independent association between Lipoprotein(a) and aortic dissection innon-smoking population (P=0.001).(二) Prevalence of Abdominal Aortic Aneurysms in Chinese Coronary ArteryDisease PatientsBackground: Abdominal aortic aneurysm (AAA) is a common cause of morbidity andmortality among Caucasians and the incidence increases rapidly after age 60. It wasreported by Madaric et al that the prevalence of AAA was much higher (14%) incoronary artery disease (CAD) patients over 60 years of age. However, little information is available on the incidence of AAA for Asian patients with CAD.Methods: We studied the prevalence of AAAs in 209 coronary artery disease (CAD)patients > 60 years of age. A group of 261 patients without CAD served as controls.Results: The prevalence of AAAs in patients with CAD was 0.48%, compared to0.77% in controls (P > 0.05). These findings demonstrate a low incidence of AAA inChinese patients with CAD.(三) Epidemiolo gy of infrarenal aortic diameter in China—Relationship of heavy drinking, lipoprotein (a) and lipid profile to infrarenal aorticdiameterBackground: Infrarenal aortic diameter is central to the diagnosis of AAA. Studies ofpatients with AAAs have shown that morbidity increases with aneurysmal diameter.There was independent graded relationship between aortic diameter and all-causemortality for the whole range of diameter values, not just those in the aneurysmal range.However, up to now, there are limited studies on the epidemiology of aortic diameter.Risk factors and potential alternative pathomechanisms for the development ofinfrarenal aortic dilatation need to be further explored. Methods: The diameter of theinfrarenal aorta was measured using ultrasound in 395 subjects (mean 66.6±10.3 yrs)with atherosclerotic diseases or risk factors. The associations between heavy drinking,serum lipoprotein(a) levels, lipid profile and infrarenal aorta diameters were examined.Results: Heavy drinking and lipoprotein (a) were positively related with infrarenalaortic dimension. While LDL-C/HDL-C, LDL-C and TC/HDL-C were negativelyassociated with infrarenal aortic diameter (19<0.05). In addition, there were negativeassociations of diabetes and positive association of COPD with aortic dimension(p<0.05).(四) Clinical study of risk factors for aortic root dilatation —Diabetes Mellitus: Is It Protective against Aortic Root Dilatation?Background: Aortic root dilatation is a major pathophysiological mechanism for aorticregurgitation and is also frequently associated with aneurysm and dissection of thethoracic aorta. The usual underlying histopathologic changes in aortic tissue associatedwith aortic dilatation are summarized as cystic medial necrosis and vary in severity. Theaortic root diameter is strongly related to age and body size, and, less strongly, to bloodpressure. However, only a small proportion of the variance of the aortic root size can beexplained by all of its known clinical and demographic variables.There is evidence of anegative association between diabetes and both abdominal aortic aneurysm (AAA) andaortic diameter. However, little information is available on the relationship betweendiabetes and aortic root diameter. Methods: We studied 109 patients with type 2diabetes,Two-dimensional echocardiography was used to measure the aortic root at theaortic annulus, the sinus of Valsalva, the sinotubular junction and the proximal part ofthe ascending aorta. Measured mean values were compared with 218 ageandsex-matched patients without diabetes. Total cholesterol, high-density lipoproteincholesterol, low-density lipoprotein cholesterol, triglycerides, creatinine and fastingglucose concentrations were measured by commercially available standardized methods.Multiple linear regression was used to evaluate the influence of diabetes and cardiacrisk factors on aortic root dimensions. Results: Aortic root diameters at all levels weresignificantly related to sex, height, weight, body surface area and infrarenal aorticdiameter. Aortic diameters at all levels were also significantly negatively related todiabetes when the entire population was considered (p<0.05).The prevalence of aorticroot dilatation was significantly higher in nondiabetic subjects than in patients withdiabetes (9.63 vs. 2.75%; p = 0.025). In multiple regression analysis involving theentire study population, with age, height (the anthropometric variable resulting in thebest model), hypertension and diabetes entered as variables, height was the strongestpredictor of aortic diameter at all levels (p<0.005 for all). Diabetes was also an independent negative determinant of all aortic diameters. Additionally, hypertensionentered the model for diameters at the sinuses of Valsalva and the ascending aorta.PartⅡThe expression of extracellular matrix metalloproteinase inducer(EMMPRIN) in human aneurysmal aortaBackground: Although abdominal aortic aneurysm (AAA) and thoracic aorticaneurysm (TAA) with or without dissection display some important differences inpathology, these three types of aneurysmal diseases shared some similar pathologicalphenotypes including the remodeling of the aortic wall, involving fragmentation anddecreased elastic fibers in the tunica media. From experimental and clinical studies, it isknown that matrix conservation and degradation by matrix metalloproteinases (MMPs)plays a major role in aortic aneurysmal diseases formation and progression.Extracellular matrix metalloproteinase inducer (EMMPRIN, basigin, CD147) is a cellsurface glycoprotein that belongs to the immunoglobulin superfamily. Recently,EMMPRIN has been reported to induce and activate the expression of MMPs inmyocardium and atherosclerotic plaque and play an important role in the ventricularremodeling and atherogenic cell differentiation. Similarly, EMMPRIN may beexpressed in human aortic aneurysm and play a role in the extracellular matrix (ECM)remodeling and the pathogenesis of aortic aneurysmal diseases. However, the potentialrole of EMMPRIN in aneurysmal pathologies has not yet been characterized.Methods: Presence of EMMPRIN was assessed in 41 surgical specimens from patientswith thoracic aortic aneurysm (TAA, Type-A aortic dissection, n=12; Type-B aorticdissection, n=7; TAA without dissection, n=7) or abdominal aortic aneurysm (AAA,n=15)by immunohistochemistry. EMMPRIN expression in aortic aneurysm tissues wascompared with 12 autopsy aortas (free of any vascular diseases), and scored for bothstaining intensity and percentage of vascular cells stained. EMMPRIN protein levels incultured human aortic smooth muscle cells (SMCs) with the stimulation of AngⅡwere analyzed by western blot.Results: EMMPRIN showed significant immunoreactivity in aortic aneurism lesionsfrom patients with TAA and AAA. In the aneurysmal wall,α-actin-positive SMCs arethe main source of EMMPRIN. The frequency of EMMPRIN overexpression wassignificantly higher in TAA with dissection (68.4%) than TAA without dissection(14.3%) (P=0.026). AngⅡstimulation upregulated the expression of EMMPIRN incultured human aortic SMCs, which could be suppressed by addition of the AngⅡreceptor type 1 (AT1-R) antagonist losartan.Conclusions:1. Serum Lipoprotein(a) level is significantly elevated in non-smoking patients withaortic dissection independently of other cardiovascular risk factors. Derterminationof Lipoprotein(a) levels may be important in identifying subjects at risk of aorticdissection among non-smokers.2. Our findings demonstrated that there is low prevalence of AAAs in Chinese patientswith CAD, which Was regarded as a high risk group for AAAs in Caucasians.3. There was a positive association between infrarenal aortic diameters and heavydrinking, as well as lipoprotein (a) levels. Furthermore, the novel and unexpectedinverse association between LDL-C/HDL-C, LDL-C, TC/HDL-C and abdominalaortic diameter may suggest a possible role for anti-atherogenic lipid profile(characterized by higher level of HDL-C, and lower level of LDL-C) in aorticdilatation processes, which need to be clarified by further studies.4. In patients with diabetes, the aortic dimension is significantly smaller than inpatients without diabetes.更多还原