The Expression And Preliminary Research Of MiRNA In Pulmonary Hypertension Subjected To Left-to-right Shunting

If patients with a large, high-pressure left-to-right shunt do not undergo surgical repair or palliation in the first months or years of life, they are at significant risk of developing progressive, irreversible anatomic changes in lung vasculature resulting pulmonary hypertension(PH). These pathologic changes in pulmonary vasculature were described and graded by Heath and Edwards in1958. In addition to a large VSD (or multiple VSDs) and a large PDA, the other lesions commonly associated with PH are complete common atrioventricular canal defect, truncus arteriosus, transposition of the great arteries with a large VSD, and specific types of single ventricle defects with no obstruction to pulmonary blood flow. The physiologic result of this diffuse vascular obstruction is pulmonary hypertension, when advanced, PH can cause right-to-left shunting which is called Eisenmenger’s syndrome.The pateint will die of hypoxia and multiple organ failure.Once Eisenmenger syndrome develops, repair of congenital heart disease is contraindicated. Advanced pulmonary vascular disease secondary to congenital heart disease remains a major problem in the developing world. Infants born with large, continued, systemic-to-pulmonary communication have a high pulmonary artery pressure and large pulmonary blood flow. High flow and high pressure in lungs inflicts endothelial damage. Platelets and leucocytes tend to adhere at the site of injury. In addition, there is degradation of extracellular matrix and release of growth factors leading to endothelial cell and smooth muscle cell hypertrophy and proliferation. Smooth muscle cells migrate to peripheral pulmonary vessels resulting in narrowing of arterioles. Intimal proliferation and fibrosis also contribute to gradual occlusion of small pulmonary arteries. Immune inflammation and thrombosis, secondary to endothelial damage, further cause obstruction in pulmonary arterioles. Endothelial dysfunction has been consider to be the starting and the key factor of PH in recent research. Endothelial dysfunction also affects the production of vasoconstrictors (endothelin I and thromboxane) and vasodilators (nitric oxide, vasoactive intestinal peptide, prostaglandin I2) leading to pulmonary vasoconstriction. Normal pulmonary vascular bed is very compliant; however, this compliance is lost in pulmonary hypertension resulting in stiffening of arterial wall.First recognized as regulators of development in worms and fruitflies, microRNAs are emerging as pivotal modulators of mammalian cardiovascular development and disease. Individual microRNAs modulate the expression of collections of messenger RNA targets that often have related functions, thereby governing complex biological processes. The wide-ranging functions of microRNAs in the cardiovascular system have provided new perspectives on disease mechanisms and have revealed intriguing therapeutic targets, as well as diagnostics, for a variety of cardiovascular disorders.Diseases of the cardiovascular system are the most common congenital birth defects and causes of adult morbidity and mortality. Although the cellular mechanisms and gene mutations responsible for numerous cardiovascular disorders have been extensively studied, it has become apparent only recently that microRNAs (miRNAs) have key roles in cardiovascular development and disease. The prominent functions of miRNAs in cardiovascular biology probably reflect the sensitivity of the cardiovascular system to relatively subtle perturbations in gene expression, which can result in severe and often fatal abnormalities.A primary role of miRNAs seems to be the’fine-tuning’of gene expression to control development and tissue homeostasis. However, under conditions of stress, the functions of miRNAs become especially pronounced, underscoring their roles in disease. Highly specific patterns of miRNA expression correlate with different cardiovascular disorders (such as cardiac hypertrophy, heart failure, post-myocardial infarction remodelling and vascular remodelling), RNAi studies in mice have revealed pathogenic and protective functions of miRNAs in vivo.Material and methodA total of80male inbred line healthy SD rats of specified-pathogens free class,4weeks old, weighing95-110g, were aleatory assigned into shunt operation group (n=40) and control group (n=40). Shunt operation group received left-to-right shunting by the connection of common carotid artery and external jugular vein via a shrinking polyethylene blood vessel connector, while Control group received sham operation. Every four weeks postoperation(4,8,12,16weeks, respectively), ten models were determined with a series of procedures:hemodynamics detection, pathological observation of pulmonary arteryResults(1)A11animal survived the operation. Hemodynamic parameters were evaluated at the12th and16th week, compare to sham operation group, We observed a significant higher pulmonary blood flow (P<0.01) in shunt operation group. Shunt operation group rats develop a significant (P<0.01) PH(higher right ventricular systolic pressure and right ventricular hypertrophy index). Pathological detection suggest the proliferation of endothelial cells and the Stricture of pulmonary arterial.(2) microarray showed that:contrast with control group,37microRNAs were differentially expressed in shunt group including a set of7downexpressed miRNAs and30overexpressed microRNAs. RT-PCR verified that miR-127was downregulated while miR-98, miR-130b were upregulated in shunt group. The result of PCR was in agreement with the microarray results. The differentially expressed microRNAs may play a significant role in the pathogensis of PAH.(3) The experession of miR-126and VEGF in congenital heart disease patients complicated pulmonary hypertension is significant higher than that of congenital heart disease patients with nomal pulmonary arterial pressure. The expression of miR-126and VEGF was in accodance with the pulmonary arterial pressure. The level of VEGF was positively correlated with the pulmonary arterial pressure.Conclusion(1)Left-to-right continuously low-flow shunt in rats can induce right ventricle hypertrophy in response to the elevation of right ventricular systolic pressure and promote chronic pulmonary arterial remodeling gradually. The establishment of left-to-right shunt models by the connection of common carotid artery and external jugular vein is a stable tool for studying chronic pulmonary arterial hypertension caused by congenital heart disease.(2)There are abundant differential expressed miRNAs in pulmonary hypertension, which may participate the formation of pulmonary vascular remodeling. The concordance of PCR and miRNA array suggest the reliability of the result of miRNA array.(3)The expression of miR-126and VEGF was significantly increased in the pulmonary hypertension. MiR-126and VEGF may play an significant role in the pulmonary hypertension.