Extravascular rapamycin film inhibits the endothelial-to-mesenchymal transition through the autophagy pathway to prevent vein graft restenosis

Prevention of anastomotic stenosis for decellularized vascular grafts using rapamycin-loaded boronic acid-based hydrogels mimicking the perivascular tissue function

Abnormal proliferation of vascular smooth muscle cells (VSMCs) induces graft anastomotic stenosis, resulting in graft failure. Herein, we developed a drug-loaded tissue-adhesive hydrogel as artificial perivascular tissue to suppress VSMCs proliferation. Rapamycin (RPM), an anti-stenosis drug, is selected as the drug model. The hydrogel was composed of poly (3-acrylamidophenylboronic acid-co-acrylamide) (BAAm) and polyvinyl alcohol. Since phenylboronic acid reportedly binds to sialic acid of glycoproteins which is distributed on the tissues, the hydrogel is expected to be adherent to the vascular adventitia. Two hydrogels containing 25 or 50 mg/mL of BAAm (BAVA25 and BAVA50, respectively) were prepared. A decellularized vascular graft with a diameter of <2.5 mm was selected as a graft model. Lap-shear test indicates that both hydrogels adhered to the graft adventitia. In vitro release test indicated that 83 and 73 % of RPM in BAVA25 and BAVA50 hydrogels was released after 24 h, respectively. When VSMCs were cultured with RPM-loaded BAVA hydrogels, their proliferation was suppressed at an earlier stage in RPM-loaded BAVA25 hydrogels compared to RPM-loaded BAVA50 hydrogels. An in vivo preliminary test reveals that the graft coated with RPM-loaded BAVA25 hydrogel shows better graft patency for at least 180 d than the graft coated with RPM-loaded BAVA50 hydrogel or without hydrogel. Our results suggest that RPM-loaded BAVA25 hydrogel with tissue adhesive characteristics has potential to improve decellularized vascular graft patency.

A novel Nanocellulose-Gelatin-AS-IV external stent resists EndMT by activating autophagy to prevent restenosis of grafts

Vein grafts are widely used for coronary artery bypass grafting and hemodialysis access, but restenosis remains the "Achilles' heel" of these treatments. An extravascular stent is one wrapped around the vein graft and provides mechanical strength; it can buffer high arterial pressure and secondary vascular dilation of the vein to prevent restenosis. In this study, we developed a novel Nanocellulose-gelatin hydrogel, loaded with the drug Astragaloside IV (AS-IV) as an extravascular scaffold to investigate its ability to reduce restenosis. We found that the excellent physical and chemical properties of the drug AS-IV loaded Nanocellulose-gelatin hydrogel external stent limit graft vein expansion and make the stent biocompatible. We also found it can prevent restenosis by resisting endothelial-to-mesenchymal transition (EndMT) in vitro. It does so by activating autophagy, and AS-IV can enhance this effect both in vivo and in vitro. This study has added to existing research on the mechanism of extravascular stents in preventing restenosis of grafted veins. Furthermore, we have developed a novel extravascular stent for the prevention and treatment of restenosis. This will help optimize the clinical treatment plan of external stents and improve the prognosis in patients with vein grafts.

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The NC-Gelatin extravascular stent has suitable physicochemical properties to prevent restenosis of the grafted veins.

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The NC-Gelatin extravascular stent has excellent biocompatibility, which is critical for grafting veins.

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The NC-Gelatin extravascular stent prevents restenosis by activating autophagy against EndMT.

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AS-IV can enhance the effect of the stent to activate autophagy against EndMT.