No abstract

The treatment of lengthy peripheral nerve defect is challenging in the field of nerve regeneration. Our previous studies have shown that low-intensity pulsed ultrasound (LIPUS) could promote the proliferation, cell viability, and neural differentiation of induced pluripotent stem cells-derived neural crest stem cells (iPSCs-NCSCs) andimprove the regeneration of damaged peripheral nerve. In this study, the mechanical signal transduction pathway of LIPUS promoting iPSCs-NCSCs proliferation and differentiation was further explored, and the effects of LIPUS combined with iPSCs-NCSCs, perfluorotributylamine (PFTBA), and growth differentiation factor 5 (GDF5) on the repair of peripheral nerve injury were evaluated. Results showed LIPUS may regulate the proliferation and differentiation of iPSCs-NCSCs through FAK-ERK1/2 signal pathway. PFTBA could supply sufficient oxygen to promote the viability of iPSCs-NCSCs under 5% hypoxia culture condition and provide a favourable microenvironment for nerve regeneration. The addition of GDF5 could promote the neural differentiation of iPSCs-NCSCs in vitro. LIPUS treatment of allogeneic decellularized nerve conduit containing iPSCs-NCSCs, PFTBA, and GDF5 has very good effect on the repair of sciatic nerve injury. Taken together, these results provide functional evidence that LIPUS might be a useful tool to explore alternative approaches in the field of nerve regeneration. KEYWORDS growth differentiation factor 5, induced pluripotent stem cells, low-intensity pulsed ultrasound, perfluorotributylamine, peripheral nerve regeneration, signal pathway

Ultrasonic Plasticization Injection Molding (UPIM) is an effective way to manufacture polymeric micro parts and has great potential for energy saving with processing polymeric materials of a small amount. To better control the UPIM process and improve the quality of micro parts, it is necessary to study the heat generation mechanism. In this paper, the interfacial friction heating process of UPIM was studied by finite element (FEM) simulation and experiment, and the temperature change in the friction interface was estimated. Then, the effects of different process parameters such as ultrasonic frequency and ultrasonic amplitude on the friction heating process were analyzed. The results showed that the rising trend of friction heating temperature was transient (finished within 1 s), and the change trend of FEM simulation was consistent with experimental results. Adjusting ultrasonic frequency and amplitude has a significant influence on the friction heating process. Increasing the ultrasonic frequency and amplitude can improve the efficiency of friction heating.