Netrin‐1 Promotes Inflammation Resolution to Achieve Endothelialization of Small‐Diameter Tissue Engineering Blood Vessels by Improving Endothelial Progenitor Cells Function In Situ

The transplant of small‐diameter tissue engineering blood vessels (small‐diameter TEBVs) (<6 mm) in vascular replacement therapy often fails because of early onset thrombosis and long‐standing chronic inflammation. The specific inflammation state involved in small‐diameter TEBVs transplants remains unclear, and whether promoting inflammation resolution would be useful for small‐diameter TEBVs therapy need study. The neural protuberant orientation factor 1 (Netrin‐1) is found present in endothelial cells of natural blood vessels and has anti‐inflammatory effects. This work generates netrin‐1‐modified small‐diameter TEBVs by using layer‐by‐layer self‐assembly to resolve the inflammation. The results show that netrin‐1 reprograms macrophages (MΦ) to assume an anti‐inflammatory phenotype and promotes the infiltration and subsequent efflux of MΦ from inflamed sites over time, which improves the local microenvironment and the function of early homing endothelial progenitor cells (EPCs). Small‐diameter TEBVs modified by netrin‐1 achieve endothelialization after 30 d and retain patency at 14 months. These findings suggest that promoting the resolution of inflammation in time is necessary to induce endothelialization of small‐diameter TEBVs and prevent early thrombosis and problems associated with chronic inflammation. Furthermore, this work finds that the MΦ‐derived exosomes can target and regulate EPCs, which may serve as a useful treatment for other inflammatory diseases.