Feasibility and Safety of Regenerated Wild Antheraea pernyi Silk Fibroin/Polyvinyl Alcohol Scaffold in Repair of Calcaneal Tendon Defects

This research discussed the value of regenerated wild Antheraea pernyi silk fibroin (RWSF)/polyvinyl alcohol (PVA) nanofiber scaffold (NFS) in repairing the calcaneal tendon defect (CTD). RWSF was prepared by saturated salt solution (SSS) method, and then RWSF/PVA NFS was prepared by electrospinning using RWSF and PVA as raw materials. Fourier transform infrared spectroscopy (FTIS) was applied to detect the characteristic absorption spectra of WSF, RWSF, and RWSF/PVA. The ultimate tensile strength (UTS) and elongation at break (BE) of RWSF/PVA NFS were analyzed by mechanical tester. The cytotoxicity of RWSF/PVA NFS was determined by MTT assay. 18 SD rats were randomly rolled into an operation group, control group, and experimental group, with 6 rats in each. Meanwhile, 27 rats were randomly grouped into three: blank group, model group, and experimental group. HE staining, Masson staining, and biomechanical properties of the regenerated fibers were analyzed in the calcaneal tendon tissues (CTTs) of rats in different groups. Expressions of tendon-related genes and inflammatory factors in CTTs in various groups were compared by RT-PCR. The results revealed that the UTS and BE of PVA and RWSF/PVA were much higher than those of natural acellular tendon (P <0.01). On day 15 after operation, the hair in the incision area of rats in the Ope, Con, and Exp groups grew normally. The implanted RWSF/PVA NFS in the Exp group adhered closely to the surrounding muscle tissue and degraded gradually, and there were still trace inflammatory cells at the junction. The tendon cross sectional area (CSA) in the Model group and RWSF/PVA group was greatly higher based on that in the Blank group (P <0.05), and the UTS in of Model group was much higher than that in the Blank group but lower to the Model group, showing great differences with P <0.05. The Collagen I, Collagen III, TGF-β1, BGN, and TNMD in CTTs in the RWSF/PVA group were higher to the Model group 2 months ago (P <0.05); while Collagen I, TGF-β1, BGN, and TNMD were still much higher 3 months later (P <0.01) but Collagen III was lower with an obvious difference (P <0.05). At 5 months, IL-1β and TNF-α in the RWSF/PVA group were greatly lower in contrast to the model group, presenting extremely obvious differences (P <0.001). The results indicated that the RWSF/PVA NFS exhibited a good biocompatibility, can accelerate the collagen secretion, promote TGF-β1, inhibit IL-1β and TNF-α factors, thus being conductive to repair of CTD. In conclusion, RWSF/PVA NFS possessed a good biocompatibility, can promote collagen secretion, elevate the TGF-β1, and inhibit IL-1β and TNF-α factors to participate in calcaneal CTD repair, showing a high value in repair of CTD.