Matrix Stiffness Regulates Interaction Between Endothelial Cells And Monocytes

Atherosclerosis is the main causes of cerebral and cardiovascular diseases,which is one of a leading threat to human.Increasing evidences indicate that when being stimulated,vascular endothelial cells generate monocyte chemoattractant protein-1(MCP-1)to recruit monocytes in the blood circulation.Meanwhile,the expression of endothelial adhesion molecules,including intercellular adhesion molecule-1(ICAM-1)and vascular cells adhesion molecule(VCAM-1),are up-regulated to arrest monocytes.In the pathogenesis of atherosclerosis,the stiffness of vascular wall will be changed.It is reported that vascular wall was softened due to deposition of low density lipoprotein and subsequently stiffened because of fibrosis to form atherosclerosis plaque.The question of whether the range of vessel wall stiffness impacts the functions of vascular cells and responsive inflammation still need to be investigated.Hereby,we hypothesized that matrix stiffness influences vascular endothelial cells,which impacts the functions of monocytes,participating in the development of atherosclerosis.To validate our hypothesis,we first prepared polyacrylamide(PA)matrix with the stiffness of 8 kPa,20 kPa and 40 kPa.We confirmed the stiffness of the PA matrix via atomic force microscope.Human umbilical vein endothelial cells(HUVECs)were then seeded onto the PA matrix to analyze the functions of HUVECs.Interestingly,no significant difference of the functions of intercellular junction and lipid absorption were observed while the expression of several inflammatory genes,MCP-1,VCAM-1 and ICAM-1,was identified to be changed remarkably by matrix stiffness.These three genes were up-regulated on 8 kPa and 40 kPa stiffness compared to 20 kPa.Further study confirmed MCP-1 protein level was also changed.Higher level of MCP-1 protein level was detected in 8 kPa(1122.92ng/mL)and 40 kPa(1132.26 ng/mL)compared to 20 kPa(889.76 ng/mL).The tendency of chemotaxis of MCP-1 to monocytes was also changed subsequently.Later NF?B signaling pathway regulators,TRAF6 and miR-146 a,were observed to be changed.Hereby,the preliminary results indicated matrix stiffness regulates inflammation related genes to modulate MCP-1 expression,thus regulating the chemotaxis of monocytes to HUVECs.In addition,VCAM-1 and ICAM-1 variation induced by matrix stiffness led to monocytes adhesion difference.Due to expression change of VCAM-1 and ICAM-1 expression,HUVECs on 8 kPa and 40 kPa matrices adhered more monocytes than 20 kPa matrix.It was reported that miR-126 and miR-222 are regulators of VCAM-1 and ICAM-1respectively.Consistently,further study indicated that reverse expression patterns of miR-126 and miR-222 to VCAM-1 and ICAM-1 respectively.Concretely,miR-126 and miR-222 were up-regulated on 20 kPa stiffness compared to 8 kPa and 40 kPa matrices.Further knocking down of miR-126 or miR-222 diminished the difference of miR-126 and miR-222 thus elevated VCAM-1 and ICAM-1 expression.Later monocytes adhesion was also increased and no significant variation was observed.Taken together,our research has investigated the impact of matrices with a series of stiffness of vessels on the interactions between HUVECs and monocytes.The results indicated that the stiffness of 8 kPa and 40 kPa promotes the chemotaxis and adhesion between endothelial cells and monocytes.Meanwhile our research noticed that matrix stiffness influences HUVECs functions via regulating cellular microRNAs for the first time,which is helpful to the research of pathogenesis and therapy of atherosclerosis.