The Role And Mechanism Of Hippo Pathway In High Shear Stress Rat Model-induced Pulmonary Hypertension

【Background】Pulmonary hypertension(PH)is a syndrome characterized by pulmonary vascular remodeling and progressive increase in pulmonary vascular resistance,leading to right ventricular hypertrophy and remodeling,followed by right heart failure leading to death.According to the latest pulmonary arterial hypertension guidelines,there are two types of pulmonary hypertension induced by high pulmonary blood flow,namely type I pulmonary arterial hypertension(PAH)and left-to-right shunt congenital heart disease(CHD).Secondary PH,chronic thromboembolic pulmonary hypertension(chronic thromboembolic pulmonary hypertension,CTEPH).During the pathogenesis of pulmonary arterial hypertension,the imbalance of calcium ion homeostasis in pulmonary arterial smooth muscle cells(PASMCs)causes pulmonary artery vascular remodeling and abnormal contraction.More and more studies have found that mechanical stress,especially hemodynamic and shear stress,plays a key role in initiating and maintaining pulmonary vascular remodeling.Hippo pathway is a classic mechanical stress-related signaling pathway,and its transcription factor YAP has attracted much attention as a mechanosensor.Recent studies have shown that YAP can be activated by various forms of mechanical stimulation,convert mechanical force into electrochemical signals,participate in vascular remodeling,and then aggravate the occurrence and development of PH,but its molecular mechanism under the action of mechanical force It’s not entirely clear.【Objectives】Endothelial injury and smooth muscle proliferation and migration are induced by blood flow shear force,which proves the role and mechanism of Hippo pathway in pulmonary vascular remodeling and pulmonary hemodynamics.【Methods】1.Establish 2-week and 5-week LPAL-PH rat models,respectively,and evaluate the LPAL-PH rat model by observing rat hemodynamics,cardiac function,tissue HE and Masson staining.2.To detect the changes of YAP(Yes-associated protein)and proliferation-related protein expression in lung tissue and pulmonary artery of LPAL-PH rat model by Western blot(Western Bolt,WB).3.The expression of YAP was assessed by immunofluorescence staining.4.The expression of YAP in primary PASMCs of LPAL-PH rat model was detected by WB,and the co-localization of YAP and its transcription factor TEAD4 was evaluated by immunofluorescence co-localization technique.5.Using WB 、 immunofluorescence staining to study the effect of YAP on the proliferation of PASMCs.6.Using WB to study the expression of YAP in the heart in LPAL-PH model.【Results】1.LPAL can induce increased right ventricular systolic blood pressure,increased mean pulmonary arterial pressure,thickening and occlusion of small pulmonary blood vessels,perivascular collagen deposition,adhesion between the ligation site and the chest wall,left lung atrophy,right lung edema,and subsequent Over time,the disease was progressively aggravated.2.The right heart structure of LPAL-PH model rats changed,right ventricular hypertrophy and right heart function decreased.3.The proliferation level of smooth muscle cells in LPAL-PH rat model increased,and the LPAL-5ws group was more obvious than LPAL-2ws.4.Due to the increase of right lung blood flow in LPAL-PH rats,the expression level of YAP in the lung tissue and PA of the LPAL group rats increased.YAP was activated into the nucleus and combined with TEAD4 to promote the proliferation of PASMCs and vascular remodeling.【Conclusion】Because the ligation of the left pulmonary artery increases the blood flow in the right lung,the shear force changes,the blood flow velocity of the blood vessel branches increases,and the YAP senses mechanical force changes,which is then activated into the nucleus,interacts with its transcription factor TEAD4,and promotes the proliferation of PACMSs,causing PA vascular remodeling.With the prolongation of left pulmonary artery ligation,the vascular remodeling became more obvious,and the vascular geometry changed,which affected the blood flow pattern,further promoted the localization of YAP nuclear,aggravated vascular remodeling,and formed a vicious circle.At the same time,right pulmonary blood flow increases,right ventricular afterload increases,causing right ventricular hypertrophy,leading to right heart failure,thereby promoting the development of pulmonary hypertension.