Degradation Behaviors Of Nerve Guidance Conduits Made Up Of Silk Fibroin In Vitro And In Vivo

Objective: The present study aimed to comprehensively investigate the in vitro and in vivo degradation behaviors of SF-NGCs versus SF fibers (control).Method: We have developed a new design of nerve guidance conduits (NGCs) made up of silk fibroin (SF) materials, referred to as SF-NGCs, by a well-established method. After SF-NGCs or SF fibers were allowed to incubate in the protease XIV solution, to be subcutaneously implanted in rabbits or to be submuscularly implanted in rats, respectively, they were subjected to degradation level measurement, mass loss assessment, and gel electrophoresis or light and electron microscopy and mass loss assessment for the dynamic course of in vitro or in vivo degradation over a 18 day period of incubation or at 4, 8, 12, and 24 weeks post-implantation, respectively. Furthermore, based on the possible involvement of lysosome-related pathways in the in vivo degradation of SF-NGCs, the time-dependent changes in the mRNA level of lysosome-related genes (Hip1R, cathepsin D, and tPA) in the subcutaneous implantation site within a 24-week period post-implantation was determined by real time RT-PCR.Results: FT-IR analysis suggested that an enhanced degradability of SF-NGCs might benefit from the conformational alterations within SF protein molecules induced by the processing of SF fibers into SF-NGCs. In brief, the mass loss of SF-NGCs and fibers was 71% and 20%, respectively, after incubation in the protease solution for 18 days. And the mass loss of SF-NGCs and fibers was 79% and 34%, respectively, at 24 weeks after subcutaneous implantation. The real time RT-PCR datas indicated that the express of lysosome-related factor changes according to the time.Conclusion: The results indicated that SF-NGCs were able to degrade at a significantly increasing rate as compared to SF fibers. The real time RT-PCR resulting data might contribute to our understanding of the molecular aspects that affect in vivo degradation and absorption of SF-NGCs.