The Mechanism Of MicroRNA-145/Osteopontin Participate In The Developent Of Ascending Aortic Aneurysm

Ascending aortic aneurysm is a serious life-threatening cardiovascular disease. This disease tends to expand asymptomatically until a catastrophic event occurs such as aortic rupture or dissection, which is associated with a high degree of morbidity and mortality. If the etiology of ascending aortic aneurysm can be clarified, then effective early treatment of the disease will improve the prognosis of patients. However, the mechanisms involved in ascending aortic aneurysm formation are not well understood, we will continue to research the pathogenesis of ascending aortic aneurysm to provide a scientific basis for targeting therapy of the disease. Ascending aortic aneurysms develop in response to pathological changes that alter the structure and composition of the aortic wall. The pathological changes result in the ascending aorta wall stiffness and decreased arterial plasticity, so that the disordered aorta can not retract effectively after expansion in response to blood flow, leading to aortic aneurysm. Smooth muscle cell and extracellular matrix are the main constituents of aortic wall, the abnormalities of smooth muscle cell and extracellular matrix will result in aortic wall disorder. Therefore, most of the researcheres are do their best to investigate the mechanisms involved in the abnormalities of smooth muscle cell and extracellular matrix to research the pathogenesis of ascending aortic aneurysm. In recent years, MicroRNAs are reported to play an important role in cardiovascular diseases by regulating cell proliferation, differentiation, apoptosis, and the process of inflammatory. In the present research, we performed several experiments to investigate whether MicroRNAs and its target proteins participant in the aortic aneurysm formation by regulating the systhesis and degradation of smooth muscle cell and extracellular matrix.Our main work includes two aspects as follows:Part Ⅰ Overexpression of MicroRNA-145 promotes ascending aortic aneurysm media remodeling through TGF-β1Objective:The main pathological characteristic in ascending aortic aneurysm is media remodeling; however, the precise mechanisms involved in this process are not well understood. MicroRNA-145 has been reported to be a novel regulator of vascular smooth muscle cell (VSMC) fate and plasticity. In this research, we examined the role of MicroRNA-145 in ascending aortic aneurysm wall media remodeling.Methods:Aortic wall samples were obtained from 10 patients who underwent operations for ascending aortic aneurysms. Control aortic tissue samples were obtained from 10 patients who underwent coronary artery bypass graft. Hematoxylin and eosin staining was used to assess aortic wall morphology. Masson’s trichrome stain was used to evaluate collagen in the aortic wall. The levels of microRNA-145 were analyzed using real-time quantitative reverse transcriptase polymerase chain reaction, and western blot were used to determine the expressions of osteopontin (OPN) and collagen. In vitro cultures of vascular smooth muscle cells (VSMCs) were established from both patient groups. The VSMCs were transfected with either microRNA-145 mimics or microRNA-145 inhibitors to determine the effect of microRNA-145 on the expression of OPN and collagen. Furthermore, cells were co-transfected with microRNA-145 and TGF-β1 siRNA to investigate whether TGF-β1 involve in the process that microRNA-145 increase the expression of osteopontin and collagen.Results:Aortic microRNA-145, OPN and collagen Ⅲ increased in ascending aortic aneurysm wall compared with controls (P<0.05). VSMCs transfected with microRNA-145 mimics increased the expression of both OPN (average of 1.59-fold, P<0.05) and collagen Ⅲ (mean of 1.71-fold, P< 0.05). Cells transfected with microRNA-145 inhibitors decreased expression of both OPN and collagen Ⅲ compared with negative controls. In addition, the inhibition of TGF-P 1 decreased the positive effect of microRNA-145 on the expression of OPN and collagen Ⅲ.Conclusion:The increased expression of microRNA-145 increases the expression of OPN and collagen through TGF-β1 in the aortic aneurysm wall, resulting in aortic media remodeling.Part II Proliferative vascular smooth muscle cells stimulate extracellular matrix production via Osteopontin/P38 MAPK signaling pathwayObjectives:Extracellular matrix disorder and cellular phenotype transformation are the major histopathological features associated with ascending aortic aneurysms. Rare studies have investigated the relationship between cellular phenotype transformation and the abnormalities of the matrix constituents. In this study, we investigated whether the cellular phenotype transformation resulted in the extracellular matrix disorder.Methods:Aortic samples were obtained from 20 patients undergoing operations for ascending aortic aneurysms. Control aortic samples were obtained from 15 patients who underwent coronary artery bypass graft. The protein levels of osteopontin (OPN), collagen and elastin were examined using western blot, and qRT-PCR was used to analyze the mRNA expression of collagen and elastin. In vitro experiment, vascular smooth muscle cells (VSMCs) were treated with Recombinant Human OPN (rh-OPN) or P38 MAPK inhibitor (SB203580) to investigate whether OPN and P38 MAPK regulated the expression of collagen and elastin.Results:The protein level of OPN and collagen Ⅲ increased in ascending aortic aneurysm samples, compared with controls (P<0.05). There was no difference in the protein level of elastin between aneurysm tissues and the controls. VSMCs treated with rh-OPN increased the collagen Ⅲ and elastin protein level and mRNA expression (P<0.05). Cells treated with SB203580 decreased the collagen Ⅲ and elastin protein level and mRNA expression (P<0.05). Furthermore, VSMCs incubated with SB203580 reduced rh-OPN-induced the production of collagen Ⅲ and elastin (P<0.05).Conclusion:OPN, the proliferative VSMCs maker, increased the expression of extracellular matrix (elastin and collagen) via P38 MAPK.OPN/P38 MAPK signaling pathways may protect against ascending aortic aneurysm progression.In the present research, we investigated the mechanism of MicroRNA-145 promoting ascending aortic aneurysm media remodeling. The results revealed that overexpression of MicroRNA-145 increased the expression of proliferative VSMCs and OPN. In addition, the proliferative VSMCs maker, OPN, increased the expression of elastin and collagen. The reults suggested that overexpression of MicroRNA-145 lead to the decrease of arterial plasticity through promoting aortic media remodeling, and the process may result in the progression of ascending aortic aneurysm. However, overexpression of MicroRNA-145 increased the expression of OPN and overexpression of OPN increased the expression of extracellular matrix, the changes may explain the low propensity of small ascending aortic aneurysm to rupture.