Motility and function of smooth muscle cells in a silk small-caliber tubular scaffold after replacement of rabbit common carotid artery.

Cell infiltration and proliferation are prerequisites for tissue regeneration and repair. The aim of the present study was to evaluate the motility and function of vascular smooth muscle cells (SMCs) in a silk-based small-caliber artificial blood vessel (SFTS) following implantation to replace the common carotid artery in rabbits. Hematoxylin and eosin (HE) staining showed a number of SMCs clearly distributed in the scaffold at 1 month, which gradually increased up to 80-90% of autologous blood vessels at 3 months and was 100% at 12 months. Smooth muscle myosin heavy chain (SM-MHC) and α-smooth muscle actin (α-SMA) are specific markers of SMCs. Real-time PCR results showed that the gene expression level of α-SMA in SFTSs was significantly down-regulated within 6 months, except in the early stage of implantation. The relative expression level of α-SMA at 12 months was five times higher than that at 3 months, indicating that SMCs phenotype transformed from synthetic to contractile. The SM-MHC+ and α-SMA+ SMCs were disorderly distributed in the scaffolds at 1 month, but became ordered along the circumference 6 months after grafting as shown by immunohistochemistry. Results indicated that the bionic SFTSs were able to induce in situ angiogenesis in defects.