Mechanisms And Inhibitory Effect Of The 3D-printed Biodegradable External Stent On Vein Graft Intimal Hyperplasia

Objective Coronary artery bypass grafting(CABG)is an effective method for surgical treatment of coronary atherosclerotic heart disease.The great saphenous vein is the most commonly used conduit in CABG.Postoperative intimal hyperplasia is an important cause of graft restenosis and poor patency ratio.Venous external stent(VES)has the potential to inhibit intimal hyperplasia and increase the patency rate of grafts by limiting venous dilatation and stabilizing hemodynamics,but the detailed mechanism is not yet clear.This study intends to fabricate a new type of biodegradable VES through 3D printing technology,and explore the inhibitory effect of VES of different diameters on graft veins.The study will also explain the potential mechanism of VES inhibiting the intimal hyperplasia,and expand the scope of application of new VESMethods By using 4-axis 3D-printing technology,biodegradable polycaprolactone(PCL)VES was prepared,and VES with different diameters were made by adjusting the production parameters.The structural characteristics of the new VES were observed using an electron scanning microscope;and the mechanical characteristics of VES were characterized by mechanical tests;the biocompatibility of VES was verified in vitro experiments;by establishing rat autologous jugular vein transplantation models,VES of different diameters(1.5mm,2.0mm)were implanted.In order to observe the patency ratio of graft veins,intimal changes,and expression of inflammatory factors respectively,animals were tested by vascular ultrasound,histology,immunohistochemistry,immunofluorescence at 2w,4w,and 8w after surgery.By using RNA-seq analysis,differential gene expression in stent veins and non-stent veins were found,and the differential genes function were analyzed correspondingly.The activity of Hippo-YAP signaling pathway in vein grafts was verified by Western bolt and PCR;rapamycin(RM)were coated on VES and implanted in the same animal models,vascular ultrasound,histology,and immunohistochemical of model animals were tested at 2w,4w and 8w after surgery.Comparison of the therapeutic effect of drug-coated stents and VES alone by observing the changes of intimal hyperplasia in vein grafts.Results PCL-VES,which produced by using 4-axis-3D printing technology,has a spring-like tubular structure,and the thickness of the stent fiber is uniform;it has well biocompatibility,radial anti-expansion,axial elasticity and flexibility.Our in vivo study found that,comparing with vein graft alone and the use of 2.0mm diameter outer stent,using 1.5mm diameter VES has a stronger inhibitory effect on the intimal hyperplasia,which can significantly reduce the expression of inflammatory factors and endothelial apoptosis,while improve patency of vein graft.In addition,the use of VES can change the extracellular matrix components by regulating the proportion of collagen fibers,increase the anti-expansion performance of the transplanted vein,reduce the expression of macrophages,and increase the expression of eNOS in the intima.RNA-seq results showed that,compared with the vein graft alone,the use of VES could maintain the activity of the Hippo-YAP signaling pathway and inhibit the formation of neointima.The RM-VES can further inhibit the intimal hyperplasia and inhibit the expression of mTOR in the vein graftConclusion 3D printed degradable VES has superior structural characteristics and excellent mechanical properties,which can limit the expansion of the vein graft and protect the function of endothelial cells.By inhibiting the expression of intimal inflammatory factors and maintaining the activity of the Hippo-YAP signaling pathway,VES improves vein remodeling and inhibits the formation of neointimal.Compared with VES alone,RM-VES could inhibit intimal hyperplasia more effectively.