The Role Of P120 Catenin In The Endothelium Injury Induced By An Impinging Flow

Objects: The formation of intracranial aneurysm(IA)is still unclear.In our previous research,we found that through the experimental model of IA in rabbits,the endothelium injured,caused by the changes of hemodynamics,played a crucial role in the formation of IA,and during the process,the expression of VE-Cadherin and P120 catenin(P120ctn)decreased in the vascular endothelium.We designed this vitro research to elucidate the effects of hemodynamic changes on the expression of P120 ctn in human umbilical vein endothelial cells(HUVEC)and its role in the formation of IA.Methods:We designed a T-chamber system to produce a impinging flow with a different velocity,and the pressure in the chamber is adjustable.HUVEC were cultured on a 22×50mm coverslip.P120 ctn in HUVEC was knocked down by small interfering RNA(Si RNA).The coverslip with endothelial cells(ECs)was placed in the chamber when the confluent rate was 85-95%.The flow rate were set at250ml/min and 500 ml/min.The morphology of HUVEC and the expression of P120 ctn,VE-Cadherin,Kaiso,α-catenin and β-catenin were examed after 3,6 and12 hours.Results: At 250 ml/min,ECs remained confluent,with no signs of damage,no gaps,no rounding up of cells been detected after 12 hours.The expression of P120 ctn,VE-Cadherin,and Kaiso decreased statistically(P<0.05),and MMP-2 had a significantly increasing expression(P<0.05).At 500 ml/min,the morphology of ECs showed no significantly changed after 6 hours.After 12 hours,ECs were over confluent and crowed at the stagnation point,while gaps between cells were enlarged and the number of cells decreased in the region with a high wall shear stress(WSS)and wall shear stress gradient(WSSG).ECs were over confluent and crowed in downstream,and were highly elongated and aligned as the direction of flow.There were a significantly decreased expression in P120ctn(P<0.01),VE-Cadherin and Kaiso and a-catenin,while the expression of MMP-2 had a statisticallyincreased(P<0.01).When P120 ctn was knocked down,at the rate of 500 ml/min,ECs remained to be confluent with normal shape in 30 minutes.After 1 hour,the number of ECs in the region with high WSS and WSSG decreased significantly,and in such region,gaps between cells were enlarged.ECs moved to downstream and were over confluent.ECs were highly elongated and aligned as the direction of flow.The expression of VE-Cadherin,Kaiso and α-catenin decreased significantly(P<0.01),while MMP-2showed a statistically increased expression(P<0.01).At the rate of 250 ml/min,no prominent damage were detected in ECs and the shape of cells were still normal after1 hour.The number of cells in region with high WSS and WSSG decreased,and moved to downstream.A significantly decreased expression in VE-Cadherin and Kaiso was detected(P<0.01),while the expression of MMP-2 had a statistically increased(P<0.01).Conclusion: The change of hemodynamic may interfere the expression of P120 ctn and damage the cohesive junction between ECs.ECs will have more chance to get injured in the region with high WSS and WSSG.When P120 ctn was knocked down,a more significant damage to cohesive junction between ECs can be observed.The change of hemodynamic may be a crucial factor in inducing endothelium injured.