A 3D-printed extravascular stent containing sirtuin-3 engineered human bone marrow mesenchymal stem cells maintains venous graft patency

BACKGROUND: Coronary artery bypass grafting (CABG) reconstructs the blood supply for treating coronary heart disease. One of the most used conduits is the great saphenous vein, but its effect is limited, owing to lower long-term patency versus arterial grafts. This study devised a 3D bio-printed stent, comprising of genetically modified human bone marrow mesenchymal stem cells (BMSCs), to improve venous graft patency. METHODS: BMSCs and endothelial cells (ECs) were obtained from sternal bone marrow and discarded saphenous veins, respectively. BMSCs were transduced with lentivirus overexpressing sirtuin-3 (SIRT3) and seeded on a 3D bio-printed matrix stent, comprising of hyaluronic acid methacryloyl and gelatin methacryloyl (HAMA/GelMA). A rat CABG model was established, via generating a jugular vein-common carotid artery arteriovenous graft. The SIRT3-BMSC-seeded stent was "wrapped" around this venous graft, serving as an extravascular stent. An in vitro model was also devised, in which lipopolysaccharide (LPS)-pre-treated ECs were co-cultured with SIRT3-BMSCs, followed by evaluating mitochondrial transferal and tunneling nanotube (TNT) formation-related functional changes. Immunoprecipitation was used to examine SIRT3-vasodilator-simulated phosphoprotein (VASP) interactions. RESULTS: EC area, along with the lowest cell proliferation and inflammatory cell infiltration; therefore, SIRT3-BMSC+stent had the greatest inhibitory effects on venous graft neointimal formation. In vitro, LPS-pre-treated ECs, after co-culture with SIRT3-BMSCs, restored endothelial, along with lowering mesenchymal marker expression. Furthermore, mechanistic analyses revealed increased SIRT-BMSC-to-LPS-pre-treated EC mitochondrial transfer, facilitated by TNTs formed between SIRT3-BMSCs and ECs. This mitochondrial transfer was mediated via SIRT3-VASP interactions, in which SIRT3 deacetylates VASP to promote TNT. CONCLUSION: SIRT3-BMSC/HAMA/GelMA extravascular stent could effectively lower arteriovenous graft dilation and inhibit neointimal formation, possibly via SIRT3 deacetylation of VASP, thereby promoting TNT formation, and subsequently, mitochondrial transfer from BMSCs to ECs to improve EC function. Thus, the extravascular stent was able to provide external support, along with facilitating BMSC therapeutic effects.