A Muscle-Mimetic Core-Sheath Composite Yarn Scaffold for In-Body Tissue Induction and Regeneration of Small-Diameter Vascular Grafts.

Cardiovascular diseases remain a leading cause of mortality worldwide. Small-diameter vascular grafts (SDVGs) continue to face critical clinical challenges, including acute thrombosis, intimal hyperplasia, and insufficient endothelialization. Inspired by the hierarchical structure of skeletal muscle, in which myofibrils assemble into muscle fibers and then into functional tissue, we developed a novel tissue-engineered vascular graft (TEVG) based on a muscle-mimetic composite yarn. Using friction spinning technology, we fabricated a core-sheath composite yarn with a poly(ethylene terephthalate) (PET) filament as the artificial myofibril core to provide durable mechanical support, and poly(glycolic acid) (PGA) staple fibers as the sheath component to replicate the extracellular matrix (ECM) topology of muscle fibers, thereby enhancing bioactivity. The knitted tubular scaffold was implanted subcutaneously in rabbits for in vivo tissue induction, followed by decellularization, yielding an extracellular matrix-rich and biocompatible graft. This "yarn mimicking muscle, fabric transforming into vessel" strategy achieved staged vascular regeneration. In a canine carotid artery replacement model, the TEVG maintained 100% patency at one month, with histological evidence of endothelialization (CD31+), smooth muscle regeneration (α-SMA+), and collagen deposition. This bioinspired approach demonstrates short-term feasibility for small-diameter vascular regeneration in a canine model, providing a promising platform for long-term studies and clinical translation.