Laminin‐modified and aligned poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/polyethylene oxide nanofibrous nerve conduits promote peripheral nerve regeneration

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) has received much attention for its biodegradability and biocompatibility, characteristics that are required in tissue engineering. In this study, polyethylene oxide (PEO)‐incorporated PHBV nanofibres with random or aligned orientation were obtained by electrospinning. For further use in vivo, the nanofibre films were made into nerve conduits after treatment with NH₃ plasma, which could improve the hydrophilicity of inner surfaces of nerve conduits and then facilitate laminin adsorption via electrostatic interaction for promoting cell adhesion and proliferation. Morphology of the surfaces of modified PHBV/PEO nanofibrous scaffolds were examined by scanning electron microscopy. Schwann cell viability assay was conducted and the results confirmed that the functionalized nanofibres were favourable for cell growth. Morphology of Schwann cells cultured on scaffolds showed that aligned nanofibrous scaffolds provided topographical guidance for cell orientation and elongation. Furthermore, three‐dimensional PHBV/PEO nerve conduits made from aligned and random‐oriented nanofibres were implanted into 12‐mm transected sciatic nerve rat model and subsequent analysis were conducted at 1 and 2 months postsurgery. The above functionalized PHBV/PEO scaffolds provide a novel and promising platform for peripheral nerve regeneration. Copyright © 2016 John Wiley & Sons, Ltd.     

A laminin‐2‐derived peptide promotes early‐stage peripheral nerve regeneration in a dual‐component artificial nerve graft

The DLTIDDSYWYRI motif (Ln2‐P3) of human laminin‐2 has been reported to promote PC12 cell attachment through syndecan‐1; however, the in vivo effects of Ln2‐P3 have not been studied. In Schwann cells differentiated from skin‐derived precursors, the peptide was effective in promoting cell attachment and spreading in vitro. To examine the effects of Ln2‐P3 in peripheral nerve regeneration in vivo, we developed a dual‐component poly(p‐dioxanone) (PPD)/poly(lactic‐co‐glycolic acid) (PLGA) artificial nerve graft. The novel graft was coated with scrambled peptide or Ln2‐P3 and used to bridge a 10 mm defect in rat sciatic nerves. The dual‐component nerve grafts provided tensile strength comparable to that of a real rat nerve trunk. The Ln2‐P3‐treated grafts promoted early‐stage peripheral nerve regeneration by enhancing the nerve regeneration rate and significantly increased the myelinated fibre density compared with scrambled peptide‐treated controls. These findings indicate that Ln2‐P3, combined with tissue‐engineering scaffolds, has potential biomedical applications in peripheral nerve injury repair. Copyright © 2012 John Wiley & Sons, Ltd.     

周围神经损伤后再生的药物调控研究

目的　探讨神康灵对损伤的坐骨神经再生的作用。方法　采用 2 8只成年体重为 2 0 0g的Wistar大鼠 ,随机分成 2组 (实验组和对照组 ) ,分别于术后 4周和 6周 ,通过肌电图检测坐骨神经运动诱发电位的传导速度和波幅 ;组织学检测有髓神经轴突数目、横截面积 ,从而探讨神康灵对坐骨神经损伤后再生的作用。结果　实验组神经传导速度、再生的有髓神经纤维横截面积、数目均优于对照组。结论　神康灵对坐骨神经损伤后的再生有明显的促进作用。     

Electrospun silk fibroin‐based neural scaffold for bridging a long sciatic nerve gap in dogs

Silk fibroin (SF)‐derived silkworms represent a type of highly biocompatible biomaterial for tissue engineering. We have previously investigated biocompatibility of SF with neural cells isolated from the central nervous system or peripheral nerve system in vitro, and also developed a SF‐based nerve graft conduit or tissue‐engineered nerve grafts by introducing bone marrow mesenchymal stem cells, as support cells, into SF‐based scaffold and evaluated the outcomes of peripheral nerve repair in a rat model. As an extension of the previous study, the electrospun technique was performed here to fabricate SF‐based neural scaffold inserted with silk fibres for bridging a 30‐mm‐long sciatic nerve gap in dogs. Assessments including functional, histological and morphometrical analyses were applied 12 months after surgery. All the results indicated that the SF‐based neural scaffold group achieved satisfactory regenerative outcomes, which were close to those achieved by autologous nerve grafts as the golden‐standard for peripheral nerve repair. Overall, our results raise a potential possibility for the translation of SF‐based electrospun neural scaffolds as an alternative to nerve autografts into the clinic.     

Functional recovery guided by an electrospun silk fibroin conduit after sciatic nerve injury in rats

The aim of this study was to evaluate the regenerative capacity of a newly developed nerve guidance conduit using electrospun silk fibroin (SFNC) implanted in a 10‐mm defect of the sciatic nerve in rats. After evaluating the physical properties and cytocompatibility of SFNC in vitro, rats were randomly allocated into three groups: defect only, autograft and SFNC. To compare motor function and abnormal sensation among groups, ankle stance angle (ASA) and severity of autotomy were observed for 10 weeks after injury. Immunostaining with axonal neurofilament (NF) and myelin basic protein (MBP) antibodies were performed to investigate regenerated nerve fibres inside SFNC. ASA increased significantly in the SFNC group at 1, 7 and 10 weeks after injury compared to the defect only group (p < 0.05). At one week, mean ASA of the SFNC group was significantly higher than that of the autograft group (p < 0.05). Onset and severity of autotomy decreased significantly in the SFNC group compared to other groups (p < 0.05). Autotomy in the SFNC group started at 4 weeks and maximally reached toe level. However, the defect only and autograft groups first showed autotomy at 2 and 1 weeks following injury, respectively, and then reached the sole level. Well myelinated nerve fibres stained with NF and MBP were found inside SFNC. In conclusion, SFNC could be helpful in restoring motor function and preventing abnormal sensations after nerve injury. Copyright © 2012 John Wiley & Sons, Ltd.     

海藻纤维膜片促进大鼠损伤坐骨神经的再生

背景：课题组和青岛大学高分子材料研究所合作研制的海藻纤维生物膜,具有优良的生物相容性,常被用作制备各种复合材料。目的：观察海藻纤维膜片包绕覆盖神经断端吻合口对大鼠坐骨神经损伤后再生的影响。方法：切断36只雄性Wistar大鼠右侧坐骨神经,随机分组：对照组行神经外膜端端吻合;实验组行神经外膜端端缝合,将海藻纤维膜片包绕并覆盖神经吻合口远近端各约0.5 cm,形成封闭再生室。术后观察海藻纤维膜片降解吸收规律及缝合处粘连情况,组织学切片行苏木精-伊红染色、锇酸染色、白细胞介素2及白细胞介素4免疫组织化学染色。结果与结论：术后4-6周,实验组海藻纤维膜片逐渐被降解吸收,与周围组织粘连较少,炎性细胞浸润程度较轻,纤维组织增生较少。两组术后1,7,14 d的白细胞介素2及白细胞介素4含量比较差异无显著性意义。实验组术后6周再生神经纤维分布规则且大小较为均一,其神经纤维数量、轴突大小及髓鞘厚度等指标均显著优于对照组（P 〈0.05）。表明海藻纤维膜片具有良好的生物降解性和组织相容性,其包绕覆盖坐骨神经形成的神经再生密闭室可促进大鼠损伤坐骨神经再生。     

Biologically inspired approaches to drug delivery for nerve regeneration

As the biological processes governing nerve regeneration have become elucidated over the past decades, interest has developed in manipulating these processes to improve nerve regeneration. Drug delivery to the regenerating nerve has the potential for major clinical applications in neurodegenerative diseases, spinal cord injury and peripheral nerve injury or sacrifice. This article reviews the evolution of the field of drug delivery to the regenerating nerve, from simple local applications of neurotrophic agents in solution and osmotic pump delivery, to the existing approaches involving novel biomaterials and genetically manipulated cell populations. A discussion of the various known nerve growth-promoting agents, and the chemical considerations involved in their delivery, is included. A perspective on the role of tissue engineering approaches for nerve regeneration in the future is offered.     

Enhancement of nerve regeneration with nimodipine treatment after sciatic nerve injury

Peripheral nerve injuries (PNI/s) are common orthopedic conditions, characterized by motor and sensory deficits in the damaged region. There is growing evidence that the L-type calcium channel antagonist nimodipine has neuroprotective and neuroregenerative effects in animal models of neurological disorders. The efficacy of nimodipine on improving motor function and sensation following a sciatic nerve crush model was investigated in male Wistar rats as a model of PNI. At different time periods following damage, we evaluated motor function, sensory recovery, electrophysiology, histomorphometry, and gene expression. Moreover, we used histological and mass ratio analysis of the gastrocnemius muscle to assess atrophy. Our findings suggest that the nimodipine improves motor and sensory function more quickly in the damaged region 2, 4, and 6 weeks after 1 week of treatment. Nimodipine treatment also increased the number of myelinated fibers while decreasing their thickness, as shown by histomorphometry. Additionally, nimodipine treatment increases the mRNA levels of neurotrophic factors (BDNF and NGF), which are known to contribute to the regeneration of injured neurons. The impact of nimodipine in PNI recovery may be due to its stimulation of the CREB signaling pathway and suppression of pro-inflammatory factor production.     

Regenerative effect of adipose tissue‐derived stem cells transplantation using nerve conduit therapy on sciatic nerve injury in rats

This study proposed a biodegradable GGT nerve conduit containing genipin crosslinked gelatin annexed with tricalcium phosphate (TCP) ceramic particles for the regeneration of peripheral nerves. Cytotoxicity tests revealed that GGT‐extracts were non‐toxic and promoted proliferation and neuronal differentiation in the induction of stem cells (i‐ASCs) derived from adipose tissue. Furthermore, the study confirmed the effectiveness of a GGT/i‐ASCs nerve conduit as a guidance channel in the repair of a 10‐mm gap in the sciatic nerve of rats. At eight weeks post‐implantation, walking track analysis showed a significantly higher sciatic function index (SFI) (P < 0.05) in the GGT/i‐ASC group than in the autograft group. Furthermore, the mean recovery index of compound muscle action potential (CMAP) differed significantly between GGT/i‐ASCs and autograft groups (P < 0.05), both of which were significantly superior to the GGT group (P < 0.05). No severe inflammatory reaction in the peripheral nerve tissue at the site of implantation was observed in either group. Histological observation and immunohistochemistry revealed that the morphology and distribution patterns of nerve fibers in the GGT/i‐ASCs nerve conduits were similar to those of the autografts. These promising results achieved through a combination of regenerative cells and GGT nerve conduits suggest the potential value in the future development of clinical applications for the treatment of peripheral nerve injury. Copyright © 2012 John Wiley & Sons, Ltd.     

Detergent‐based decellularized peripheral nerve allografts: An in vivo preclinical study in the rat sciatic nerve injury model

Nerve autograft is the gold standard technique to repair critical nerve defects, but efficient alternatives are needed. The present study evaluated the suitability of our novel Roosens‐based (RSN) decellularized peripheral nerve allografts (DPNAs) in the repair of 10‐mm sciatic nerve defect in rats at the functional and histological levels after 12 weeks. These DPNAs were compared with the autograft technique (AUTO) and Sondell (SD) or Hudson (HD) based DPNAs. Clinical and functional assessments demonstrated a partial regeneration in all operated animals. RSN‐based DPNAs results were comparable with SD and HD groups and closely comparable with the AUTO group without significant differences (p > .05). Overall hematological studies confirmed the biocompatibility of grafted DPNAs. In addition, biochemistry revealed some signs of muscle affection in all operated animals. These results were confirmed by the loss of weight and volume of the muscle and by muscle histology, especially in DPNAs. Histology of repaired nerves confirmed an active nerve tissue regeneration and partial myelination along with the implanted grafts, being the results obtained with HD and RSN‐based DPNAs comparable with the AUTO group. Finally, this in vivo study suggests that our novel RSN‐based DPNAs supported a comparable tissue regeneration, along the 10‐mm nerve gap, after 12‐week follow‐up to HD DPNAs, and both were superior to SD group and closely comparable with autograft technique. However, further improvements are needed to overcome the efficacy of the nerve autograft technique.     

神经生长液促大鼠坐骨神经再生的实验研究

目的评价一种新型中药-神经生长液对大鼠坐骨神经损伤后神经再生的影响。方法SD大鼠50只雌雄各半,采用随机数字表法将其随机分成5组:神经生长液低、中、高剂量组,弥可保组和空白对照组。采用坐骨神经夹伤模型,于术后每5d测定坐骨神经功能指数(sciaticnerveindex,SFI),术后第20天行电生理,组织学检测及超微结构观察。结果术后5d时实验组(-72±9)与对照组(-79±8)间SFI差异无显著性意义(F=1.58,P>0.05),10d时高剂量组(-60±9)和弥可保组(-61±7)优于对照组(-75±7)(F=5.1,P<0.05),15d和20d时低、中、高剂量组及弥可保组均优于对照组(F=6.83和9.92,P<0.05)。坐骨神经干动作电位传导速度,小腿三头肌最大收缩力检测,及脊髓前角运动神经元记数、再生有髓纤维数、肌细胞截面积等指标神经生长液低、中、高剂量组及弥可保组均优于空白对照组(F=26.29,51.35,7.86,37.38,11.11,P<0.05)。超微结构观察实验组有髓神经纤维的髓鞘形态、厚度、成熟度均优于对照组,变性纤维的数目少于对照组。结论神经生长液能促进周围神经再生及功能的恢复。     

Gelatin‐based hydrogel for vascular endothelial growth factor release in peripheral nerve tissue engineering

Hydrogels are promising materials in regenerative medicine applications, due to their hydrophilicity, biocompatibility and capacity to release drugs and growth factors in a controlled manner. In this study, biocompatible and biodegradable hydrogels based on blends of natural polymers were used in in vitro and ex vivo experiments as a tool for VEGF‐controlled release to accelerate the nerve regeneration process. Among different candidates, the angiogenic factor VEGF was selected, since angiogenesis has been long recognized as an important and necessary step during tissue repair. Recent studies have pointed out that VEGF has a beneficial effect on motor neuron survival and Schwann cell vitality and proliferation. Moreover, VEGF administration can sustain and enhance the growth of regenerating peripheral nerve fibres. The hydrogel preparation process was optimized to allow functional incorporation of VEGF, while preventing its degradation and denaturation. VEGF release was quantified through ELISA assay, whereas released VEGF bioactivity was validated in human umbilical vein endothelial cells (HUVECs) and in a Schwann cell line (RT4‐D6P2T) by assessing VEGFR‐2 and downstream effectors Akt and Erk1/2 phosphorylation. Moreover, dorsal root ganglia explants cultured on VEGF‐releasing hydrogels displayed increased neurite outgrowth, providing confirmation that released VEGF maintained its effect, as also confirmed in a tubulogenesis assay. In conclusion, a gelatin‐based hydrogel system for bioactive VEGF delivery was developed and characterized for its applicability in neural tissue engineering. Copyright © 2014 John Wiley & Sons, Ltd.     

Cell‐free artificial implants of electrospun fibres in a three‐dimensional gelatin matrix support sciatic nerve regeneration in vivo

Surgical repair of larger peripheral nerve lesions requires the use of autologous nerve grafts. At present, clinical alternatives to avoid nerve transplantation consist of empty tubes, which are only suitable for the repair over short distances and have limited success. We developed a cell‐free, three‐dimensional scaffold for axonal guidance in long‐distance nerve repair. Sub‐micron scale fibres of biodegradable poly‐ε‐caprolactone (PCL) and collagen/PCL (c/PCL) blends were incorporated in a gelatin matrix and inserted in collagen tubes. The conduits were tested by replacing 15‐mm‐long segments of rat sciatic nerves in vivo. Biocompatibility of the implants and nerve regeneration were assessed histologically, with electromyography and with behavioural tests for motor functions. Functional repair was achieved in all animals with autologous transplants, in 12 of 13 rats that received artificial implants with an internal structure and in half of the animals with empty nerve conduits. In rats with implants containing c/PCL fibres, the extent of recovery (compound muscle action potentials, motor functions of the hind limbs) was superior to animals that had received empty implants, but not as good as with autologous nerve transplantation. Schwann cell migration and axonal regeneration were observed in all artificial implants, and muscular atrophy was reduced in comparison with animals that had received no implants. The present design represents a significant step towards cell‐free, artificial nerve bridges that can replace autologous nerve transplants in the clinic. Copyright © 2017 John Wiley & Sons, Ltd.     

Repairing peripheral nerve defects with revascularized tissue‐engineered nerve based on a vascular endothelial growth factor‐heparin sustained release system

To enhance the angiogenic capacity of tissue‐engineered peripheral nerves, we have constructed revascularized tissue‐engineered nerves based on a vascular endothelial growth factor (VEGF)‐heparin sustained release system. However, the effects of the repair of large peripheral nerve defects are not known. In this study, we used the above revascularized tissue‐engineered nerve to repair large nerve defects in rats. The repair effects were observed through general observation, functional evaluation of nerve regeneration, ultrasound examination, neural electrophysiology, wet weight ratio of bilateral gastrocnemius muscle, histological evaluation, and quantitative real‐time polymerase chain reaction (PCR) analysis. The results showed that the tissue‐engineered peripheral nerve based on a VEGF‐heparin sustained release system can achieve early vascularization and restore blood supply in the nerve graft area. The realization of early vascularization in the area of the nerve defect greatly promotes the speed of nerve regeneration and reconstruction in the area of the nerve defect, which greatly advances the process of nerve repair and reconstruction and accelerates the restoration of the normal morphological structure and function of peripheral nerves.     

利用胶原导管和聚四氟乙烯平板修复兔面神经损伤的实验研究

目的评价自体神经移植物、聚四氟乙烯平板(ePTFE)和胶原导管在修复兔面神经损伤中的作用。方法将兔面神经主干分离、切断并隔离5mm,神经断端分别用自体神经、ePTFE或胶原导管连接。术后第7天和1个月、3个月测定实验动物的神经传导速度。处死动物,取出移植物,计数标本断面有髓神经纤维数量。结果术后第7天,各组动物的标本中几乎均未观察到神经生长,在此后的3个月中,观察到自体神经和移植物中有轴突生长,且不同时间点之间有显著性差异,不同时间点的神经传导速度也有显著性差异。结论ePTFE和胶原导管可以作为修复周围神经系统损伤的生物相容性材料。     

不同浓度许旺细胞与聚乳酸-聚羟基乙酸共聚物修复损伤周围神经的比较

背景：有研究表明,许旺细胞神经移植复合体具有极强修复自体神经缺损作用,并且许旺细胞在神经再生过程中发挥至关重要的作用。目的：比较不同浓度许旺细胞神经移植复合体修复自体神经缺损时周围神经的再生效果。方法：建立坐骨神经缺损模型大鼠。原代培养大鼠许旺细胞,构建聚乳酸-聚羟基乙酸共聚物管-细胞外基质凝胶-许旺细胞神经移植复合体修复坐骨神经缺损模型大鼠。按许旺细胞浓度的不同分为105,106,107,108,109 L-1结果与结论：建模后3,6和12周,含许旺细胞各浓度的神经移植复合体组各时间点神经传导速率均高于对照组（P 〈0.01）,其中10浓度组,对照组不含许旺细胞。分别于建模后3,6和12周,行运动神经传导速度的测定。建模后12周各组胫骨前肌湿质量测量和组织学观察。8 L-1组运动神经传导速度优于其他各浓度组（P 〈0.05）。建模后12周,大鼠胫骨前肌苏木精-伊红染色显示,各浓度许旺细胞神经移植复合体组正常肌纤维数均多于对照组（P 〈0.05）。其中许旺细胞浓度108,109 L-1浓度组胫骨前肌形态恢复较好,肌纤维细条样、波浪状,同向而行,长短、粗细及疏密大致一致。结果证实,108 L-1许旺细胞神经聚乳酸-聚羟基乙酸共聚物移植复合体对缺损坐骨神经再生的促进作用较好。     

Undifferentiated and differentiated adipose‐derived stem cells improve nerve regeneration in a rat model of facial nerve defect

Autologous nerve grafting is the current procedure used for repairing facial nerve gaps. As an alternative to this method, tissue engineering cell‐based therapy using induced pluripotent stem cells, Schwann cells and bone marrow‐derived mesenchymal stem cells has been proposed. However, these cells have major problems, including tumorigenesis in induced pluripotent stem cells and invasiveness and limited tissue associated with harvesting for the other cells. Here, we investigated the therapeutic potential of adipose‐derived stem cells (ASCs), which can be harvested easily and repeatedly by a minimally invasive liposuction procedure. The ASCs had characteristics of mesenchymal tissue lineages and could differentiate into Schwann‐like cells that were relatively simple to isolate and expand in culture. In an in vivo study, a silicone conduit containing undifferentiated ASCs, differentiated ASCs or Schwann cells were transplanted, embedded in a collagen gel and the efficacy of repair of a 7 mm‐gap in the rat facial nerve examined. Morphometric quantification analysis of regenerated facial nerves after a regeneration period of 13 weeks showed that undifferentiated ASCs, differentiated ASCs, and Schwann cells had similar potential for nerve regeneration. Furthermore, the functional recovery of facial nerve regeneration using a rat facial palsy scoring system in the three groups was close to that in autologous nerve graft positive controls. These findings suggest that undifferentiated and differentiated ASCs may both have therapeutic potential in facial nerve regeneration as a source of Schwann cells in cell‐based therapy performed as an alternative to autologous nerve grafts. Copyright © 2014 John Wiley & Sons, Ltd.     

白细胞介素-1对周围神经再生及功能恢复的实验研究

目的本研究采用神经再生室研究白细胞介素-1(Interlukin-1,IL-1)对周围神经再生功能的影响.方法将57只SD大白鼠随机分为IL-1、白细胞介素-1受体拮抗剂(Interkukin-1ReceptorAntagonist,IL-1ra)和等渗盐水3组.术后3、6周取材作神经电生理检查,术后16周作大鼠趾展宽度测定.结果IL-1组再生周围神经功能明显优于IL-1ra组和等渗盐水组.IL-1ra组和等渗盐水组间没有明显差异.结论IL-1具有促进周围神经再生及神经功能恢复的作用.     

Nanofibrous gelatine scaffolds integrated with nerve growth factor‐loaded alginate microspheres for brain tissue engineering

Neural regeneration research is designed in part to develop strategies for therapy after nerve damage due to injury or disease. In this study, a new gelatine‐based biomimetic scaffold was fabricated for brain tissue engineering applications. A technique combining thermally induced phase separation and porogen leaching was used to create interconnected macropores and nanofibrous structure. To promote tissue regeneration processes, the scaffolds were integrated with nerve growth factor (NGF)‐loaded alginate microspheres. The results showed that nanofibrous matrix could only be obtained when gelatine concentration was at least 7.5% (w/v). The scaffold with a modulus value (1.2 kPa) similar to that of brain tissue (0.5–1 kPa) was obtained by optimizing the heat treatment time, macropore size and gelatine concentration. The encapsulation efficiencies of NGF into 0.1% and 1% alginate microspheres were 85% and 100%, respectively. The release rate of NGF from the microspheres was controlled by the alginate concentration and the poly(L‐lysine) coating. The immobilization of the microspheres in the scaffold reduced burst release and significantly extended the release period. The nanofibrous architecture and controlled release of NGF from the microspheres induced neurite extension of PC12 cells, demonstrating that the released NGF was in an active form. The results suggest that the scaffolds prepared in this study may have potential applications in brain tissue engineering due to topologic and mechanical properties similar to brain tissue and pore structure suitable for cell growth and differentiation. Copyright © 2016 John Wiley & Sons, Ltd.