The Screening And Identification Of Phthogenic Related Genes Of Aortic Dissection

【Background】Aortic dissection is a catastrophic disease developing without any warning.Little is known about the underlying defects of aortic dissection.Patients with known heritable connective disorders,such as Marfan-syndrome patients with a defect of the glycoprotein fibrillin-1,and Ehlers-Danlos syndrome patients with a typeⅢ-procollagen disorder are known to develop aortic dissection very early in their life. However,only few patients with aortic dissection suffer from one of these syndromes. Historically,hypertension is thought to be the main etiology of aortic dissection apart from above mentioned patients.Nevertheless,the prevalence of hypertension is much higher than that of aortic dissection;most of the patients of hypertension wouldn't develop into aortic dissection.Some of the patients of aortic dissection suffer from this disease without apparent hypertension.Based on these observations arises the question:"Does an unknown connective tissue disorder cause a predisposition for aortic dissection?" We compared gene expression profiles of the aorta from acute type B aortic dissection with those from normal controls.【Materials and methods】From Sep,2005 to Feb,2007,23 descending aorta specimens from patients with an acute Stanford B dissection were taken during surgery;15 normal descending aorta specimens were taken from multi-organ donors.We compared the gene expression profiles between these two groups using 6 pieces of Phalanx Whole Genome Microarray gene chips.For analysis only genes with strong signals of more than 70 percent of the mean signal of all spots on the arrays were accepted as being expressed. The data from gene chips were analyzed with several professional gene chip data processing softwares and online websites.By literature retrieving,reading and comparing,we hypothese some genes are related to aortic dissection and maybe the pathogenic ones.Quantitative real time polymerase chain reaction was used to confirm the reliability of the data from the gene chips.Western Blot and Immunohistochemistry were applied to validate the protein level coded by four genes between two groups.Elastin dyeing and HE staining were employed to check the structure of aortic walls.Finally,electron microscope was adopted to observe the phenotype of smooth muscle cells.【Results】Totally the gene chips could detect 39200 genes of humans'.After raw data validation, the results of 6375 genes were thought to be valid in this experiment.Of those,1293 genes were differently expressed in dissected and control aorta specimens,496 ones were up regulated and 797 ones were down regulated.Some genes coding for extra cellular matrix components such as COL6A3,COL1A1, and COL3A1 were up regulated,other genes coding for extra cellular matrix components(e.g.COL6A2 and COL16A1) were down regulated.The molecular markers to confirm the intermediate phenotype of smooth muscle cell such as osteopontin were up regulated in the dissected group.However,the markesr for contractile phenotype(e.g.α-SMA,calponin) were down regulated.Several genes encoded for cell to matrix signaling,cell to cell adhesion(e.g.PKD 1 and PKD 2), were found to be down-regulated.The difference level of protein coded by PKD1, PKD 2,osteopontin,andα-SMA were validated by Western Blot or Immunohistochemistry.Electron microscope checking showed that the smooth muscle cells were undergoing phenotype modulation.【Conclusion】Our results demonstrate the complexity of the dissecting process on a molecular level. Some of the genes coding for extra cellular matrix components were down-regulated whereas some of them were up-regulated.The molecular markers of smooth muscle cells were differently expressed,indicating some cells were turned from contractile one into intermediate ones.The expressing difference of PKD1 and PKD2 maybe play a key role in the phenotype changing of smooth muscle cells and probably resulting into the development of aortic dissection finally.