Objective To explore the advance in physical materials,chemical matrix, and biological seed cells for fabricating artificial nerve. Methods Recent literature relevant to artificial nerve, especially the achievement in physical material, chemical matrix and biological seed cells for fabricating artificial nerve, were extensively reviewed. Results Polymers of polylactic acid or polyglycolic acid and their polymer, polymer of hyaluronic acid and glut-aldehyde, polymer of polyacrylonitrile and polyvinylchloride were artificial nerve materials with the properties of good biocompatibility and biodegradation. A conduit with multichannel and high percentage of pores was beneficial to the regeneration of nerve. The activated Schwann cells were excellent seeds of artificial nerve. A suitable chemical matrix, such as laminin and alginate, could promote the regeneration of nerve. Conclusion The successful fabrication of artificial nerve lies in the advance in the mechanism of nerve regeneration and physical material, chemical matrix and biological seed cells.
ObjectiveTo summarize the research progress of autologous vein nerve conduit for the repair of peripheral nerve defect. MethodsThe recent domestic and foreign literature concerning autologous vein nerve conduit for repair of peripheral nerve defect was analyzed and summarized. ResultsA large number of basic researches and clinical applications show that the effect of autologous venous nerve conduit is close to that of autologous nerve transplantation in repairing short nerve defect, especially the compound nerve conduit has a variety of autologous nerve tissue, cells, and growth factors, etc. ConclusionAutologous vein nerve conduit for repair of non-nerve defect can be a good supplement of autologous nerve graft, improvement of autologous venous catheter to repair peripheral nerve defect is the research direction in the future.
Objective To explore a green route for the fabrication of thermo-sensitive chitosan nerve conduits, improve the mechanical properties and decrease the degradation rate of the chitosan nerve conduits. Methods Taking advantage of the ionic specific effect of the thermo-sensitive chitosan, the strengthened chitosan nerve conduits were obtained by immersing the gel-casted conduits in salt solution for ion-induced phase transition, and rinsing, lyophilization, and 60Co sterilization afterwards. The nerve conduits after immersing in NaCl solutions for 0, 4, 12, 24, 36, 48, and 72 hours were obtained and characterized the general observation, diameters and mechanical properties. According to the above results, the optimal sample was chosen and characterized the microstructure, degradation properties, and cytocompatibility. The left sciatic nerve defect 15 mm in length was made in 20 male Sprague Dawley rats. The autologous nerves (control group, n=10) and the nerve conduits (experimental group, n=10) were used to repair the defects. At 8 weeks after operation, the compound muscle action potential (CMAP) was measured. The regenerated nerves were investigated by gross observation and toluidine blue staining. The gastrocnemius muscle was observed by HE staining. Results With the increased ionic phase transition time, the color of the conduit was gradually deepened and the diameter was gradually decreased, which showed no difference during 12 hours. The tensile strength of the nerve conduit was increased gradually. The ultimate tensile strength showed significant difference between the 48 hours and 12, 24, and 36 hours groups (P<0.05), and no significant difference between the 48 hours and 72 hours groups (P>0.05). As a result, the nerve conduit after ion-induced phase transition for 48 hours was chosen for further study. The scanning electron microscope (SEM) images showed that the nerve conduit had a uniform porous structure. The degradation rate of the the nerve conduit after ion-induced phase transition for 48 hours was significantly decreased as compared with that of the conduit without ion-induced phase transition. The nerve conduit could support the attachment and proliferation of rat Schwann cells on the inner surface. The animal experiments showed that at 8 weeks after operation, the CMAPs of the experimental and control groups were (3.5±0.9) and (4.3±1.1) m/V, respectively, which showed no significant difference between the two groups (P<0.05), and were significantly lower than that of the contralateral site ［(45.6±5.6 m/V), P>0.05］. The nerve conduit of the experimental group could repair the nerve defect. There was no significant difference between the experimental and control groups in terms of the histomorphology of the regenerated nerve fibers and the gastrocnemius muscle. Conclusion The green route for the fabrication of thermo-sensitive chitosan nerve conduits is free of any toxic reagents, and has simple steps, which is beneficial to the industrial transformation of the chitosan nerve conduit products. The prepared chitosan nerve conduit can be applied to rat peripheral nerve defect repair and nerve tissue engineering.
ObjectiveTo investigate the in vivo degradation and histocompatibility of modified chitosan based on conductive composite nerve conduit, so as to provide a new scaffold material for the construction of tissue engineered nerve.MethodsThe nano polypyrrole (PPy) was synthesized by microemulsion polymerization, blended with chitosan, and then formed conduit by injecting the mixed solution into a customized conduit formation model. After freeze-drying and deacidification, the nano PPy/chitosan composite conduit (CP conduit) was prepared. Then the CP conduits with different acetyl degree were resulted undergoing varying acetylation for 30, 60, and 90 minutes (CAP1, CAP2, CAP3 conduits). Fourier infrared absorption spectrum and scanning electron microscopy (SEM) were used to identify the conduits. And the conductivity was measured by four-probe conductometer. The above conduits were implanted after the subcutaneous fascial tunnels were made symmetrically on both sides of the back of 30 female Sprague Dawley rats. At 2, 4, 6, 8, 10, and 12 weeks after operation, the morphology, the microstructure, and the degradation rate were observed and measured to assess the in vivo degradation of conduits. HE staining and anti-macrophage immunofluorescence staining were performed to observe the histocompatibility in vivo.ResultsThe characteristic peaks of the amide Ⅱ band around 1 562 cm−1 appeared after being acetylated, indicating that the acetylation modification of chitosan was successful. There was no significant difference in conductivity between conduits (P>0.05). SEM observation showed that the surfaces of the conduits in all groups were similar with relatively smooth surface and compact structure. After the conduits were implanted into the rats, with the extension of time, all conduits were collapsed, especially on the CAP3 conduit. All conduits had different degrees of mass loss, and the higher the degree of acetylation, the greater the mass change (P<0.05). SEM observation showed that there were more pores at 12 weeks after implantation, and the pores showed an increasing trend as the degree of acetylation increased. Histological observation showed that there were more macrophages and lymphocytes infiltration in each group at the early stage. With the extension of implantation time, lymphocytes decreased, fibroblasts increased, and collagen fibers proliferated significantly. ConclusionThe modified chitosan basedon conductive composite nerve conduit made of nano-PPy/chitosan composite with different acetylation degrees has good biocompatibility, conductivity, and biodegradability correlated with acetylation degree in vivo, which provide a new scaffold material for the construction of tissue engineered nerve.
ObjectiveTo investigate the effect of folic acid coated-crosslinked urethane-doped polyester elastomer (fCUPE) nerve conduit in repairing long distance peripheral nerve injury. MethodsThirty-six 3-month-old male Sprague Dawley rats weighing 180-220 g were randomly assigned to 3 groups, each consisting of 12 rats: CUPE nerve conduit transplantation group (group A), fCUPE nerve conduit transplantation group (group B), and autologous nerve transplantation group (group C), the contralateral healthy limb of group C served as the control group (group D). A 20-mm-long sciatic nerve defect model was established in rats, and corresponding materials were used to repair the nerve defect according to the group. The sciatic function index (SFI) of groups A-C was calculated using the Bain formula at 1, 2, and 3 months after operation. The nerve conduction velocity (NCV) of the affected side in groups A-D was assessed using neuroelectrophysiological techniques. At 3 months after operation, the regenerated nerve tissue was collected from groups A-C for S-100 immunohistochemical staining and Schwann cell count in groups A and B to compare the level of nerve repair and regeneration in each group. ResultsAt 3 months after operation, the nerve conduits in all groups partially degraded. There was no significant adhesion between the nerve and the conduit and the surrounding tissues, the conduit was well connected with the distal and proximal nerves, and the nerve-like tissues in the conduit could be observed when the nerve conduit stents were cut off. SFI in group A was significantly higher than that in group C at each time point after operation and was significantly higher than that in group B at 2 and 3 months after operation (P<0.05). There was no significant difference in SFI between groups B and C at each time point after operation (P>0.05). NCV in group A was significantly slower than that in the other 3 groups at each time point after operation (P<0.05). The NCV of groups B and C were slower than that of group D, but the difference was significant only at 1 month after operation (P<0.05). There was no significant difference between groups B and C at each time point after operation (P>0.05). Immunohistochemical staining showed that the nerve tissue of group A had an abnormal cavo-like structure, light tissue staining, and many non-Schwann cells. In group B, a large quantity of normal neural structures was observed, the staining was deeper than that in group A, and the distribution of dedifferentiated Schwann cells was obvious. In group C, the nerve bundles were arranged neatly, and the tissue staining was the deepest. The number of Schwann cells in group B was (727.50±57.60) cells/mm2, which was significantly more than that in group A [(298.33±153.12) cells/mm2] (t=6.139, P<0.001). ConclusionThe fCUPE nerve conduit is effective in repairing long-distance sciatic nerve defects and is comparable to autologous nerve grafts. It has the potential to be used as a substitute material for peripheral nerve defect transplantation.
ObjectiveTo describe the research progress of silk-based biomaterials in peripheral nerve repair and provide useful ideals to accelerate the regeneration of large-size peripheral nerve injury. Methods The relative documents about silk-based biomaterials used in peripheral nerve regeneration were reviewed and the different strategies that could accelerate peripheral nerve regeneration through building bioactive microenvironment with silk fibroin were discussed. Results Many silk fibroin tissue engineered nerve conduits have been developed to provide multiple biomimetic microstructures, and different microstructures have different mechanisms of promoting nerve repair. Biomimetic porous structures favor the nutrient exchange at wound sites and inhibit the invasion of scar tissue. The aligned structures can induce the directional growth of nerve tissue, while the multiple channels promote the axon elongation. When the fillers are introduced to the conduits, better growth, migration, and differentiation of nerve cells can be achieved. Besides biomimetic structures, different nerve growth factors and bioactive drugs can be loaded on silk carriers and released slowly at nerve wounds, providing suitable biochemical cues. Both the biomimetic structures and the loaded bioactive ingredients optimize the niches of peripheral nerves, resulting in quicker and better nerve repair. With silk biomaterials as a platform, fusing multiple ways to achieve the multidimensional regulation of nerve microenvironments is becoming a critical strategy in repairing large-size peripheral nerve injury. Conclusion Silk-based biomaterials are useful platforms to achieve the design of biomimetic hierarchical microstructures and the co-loading of various bioactive ingredients. Silk fibroin nerve conduits provide suitable microenvironment to accelerate functional recovery of peripheral nerves. Different optimizing strategies are available for silk fibroin biomaterials to favor the nerve regeneration, which would satisfy the needs of various nerve tissue repair. Bioactive silk conduits have promising future in large-size peripheral nerve regeneration.