Functional assessment of sciatic nerve reconstruction: biodegradable poly (DLLA-epsilon-CL) nerve guides versus autologous nerve grafts

The aim of this study was to compare functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with modified denatured muscle tissue (MDMT), or an autologous nerve graft. We evaluated nerve recovery using walking track analysis (measurement of the sciatic function index [SFI]) and electrostimulation tests. Functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with MDMT was faster when compared with nerve reconstruction using an autologous nerve graft. We conclude that in case of a short nerve gap in the rat, reconstruction can best be carried out using a p(DLLA-epsilon-CL) biodegradable nerve guide filled with MDMT.     

PLGA 90/10 and caprolactone biodegradable nerve guides for the reconstruction of the rat sciatic nerve

The purpose of this study was to test in vivo two different nerve guides for promoting nerve regeneration across a 10-mm gap of the rat sciatic nerve: 1) one made of PLGA in a novel proportion (90:10) of the two polymers poly(L-lactide):poly(glycolide); 2) another made of (DL-lactide-epsilon-caprolactone) copolyester (Neurolac) tube, by comparing its healing efficacy with that of the more traditional methods of end-to-end nerve suture and autologous graft. Motor and sensory functional recovery were assessed throughout the healing period of 20 weeks, and the repaired nerves were processed for morphological and histomorphometrical analysis. Both motor and sensory functions improved significantly in all experimental nerve repaired groups. At the end of the 20-week follow-up, the end-to-end group showed better recovery of motor function when compared with the groups treated with guiding tubes. However, at this time point, the level of motor function in the Neurolac(R) and PLGA groups was similar to the one of the graft group. Nociception function also recovered faster in the end-to-end group compared with the Neurolac(R) and PLGA groups, and in this case, recovery was also delayed in the graft group. At the end of follow-up, nociception was similar in all experimental groups. Morphological and histomorphometrical analysis showed that axon regeneration occurred in both PLGA and Neurolac(R) experimental groups, with no significant differences in the total number of regenerated fibers, but disclosed a different pattern of degradation of the two types of tubes with larger biodegradation of PLGA material by the end of 20 weeks. These results suggest that both types of biomaterials are a good substrate for preparing tubular nerve guides, and their different pattern of degradation does not seem to influence the degree of nerve regeneration.     

Interposed autologous nerve segment stimulates nerve regeneration in peripheral nerve allografts in a rat model

The ability of autologous nerve segments interposed between allografts, to increase the total nerve-gap distance, was studied. Sciatic nerve allografts were carried out in a rat model. A 15-mm nerve gap was repaired with a 25-mm nerve graft (interposed group: allo-auto-allograft; control group: allo-allo-allograft). Cyclosporin was given for 12 weeks. Nerve regeneration was evaluated using the weight of the anterior tibial muscle and histologic, morphometric and immunohistochemical analyses at 12, 13, 14, 15, 16, 20, and 24 weeks. Nerve regeneration in the interposed group was statistically significantly better than that in the control group. The authors concluded that a nerve allograft with interposed autograft may enhance nerve regeneration in this model, because of the migration of host-derived Schwann cells into the graft from not only the proximal and distal host nerve stumps, but also the interposed autograft.     

Vascular endothelial growth factor promotes peripheral nerve regeneration after sciatic nerve transection in rat

Objective：To evaluate the local effect of vascular endothelial growth factor （VEGF） on transected sciatic nerve regeneration.Methods：Sixty male white Wistar rats were divided into four experimental groups randomly （n=15）.In transected group the left sciatic nerve was transected and the stump was fixed to adjacent muscle.In treatment group the defect was bridged using a silicone graft filled with 10μL VEGF.In silicone group the graft was filled with phosphate-buffered saline.In sham-operated group the sciatic nerve was exposed and manipulated.Each group was subdivided into three subgroups with five animals in each and nerve fibers were studied 4,8 and 12 weeks after operation.Results：Behavioral test,functional study of sciatic nerve,gastrocnemius muscle mass and morphometric indices confirmed a faster recovery of regenerated axons in VEGF group than in silicone group （P〈0.05）.In immunohistochemical assessment,reactions to S-100 in VEGF group were more positive than that in silicone group.Conclusion：Local administration of VEGF will improve functional recovery and morphometric indices of sciatic nerve.     

Guided regeneration with resorbable conduits in experimental peripheral nerve injuries

Guided tissue regeneration is a new approach in the reconstructive surgery of peripheral nerves. Artificial conduits can be constructed from biodegradable polymers. Lactic/caproic acid copolymers and polyphospazenes are biocompatible materials with a slow resorption rate. Conduits made from either poly-[1-lactide-co-6-caprolatone] or poly-[bis-(ethylalanate)-phosphazene] were assessed for use as guides for nerve regeneration in experimental animals. Under general anesthesia and by using a microsurgery technique both sciatic nerves were exposed in 2 groups of 9 Wistar rats. On the right side, a 10 mm segment of the nerve was removed, and the defect was then repaired using a conduit. On the left side, the same defect was bridged using as an autograft the nerve segment, which had been removed from the right sciatic nerve. Histological and electron microscopy investigations were performed after 30, 90 and 180 days and showed the gradual degradation of both types of conduits without any evidence of local toxicity. The regeneration of the nerve fibers in the lumen was not significantly different from that shown by the autologous grafts. Likewise, no differences were found at 180 days in the functional recovery of the nerve (evoked muscle action potential). Both conduits were found to be effective for guided nerve regeneration. Poly-[1-lactide-co-6-caprolactone] tubes were easier to insert, while polyphosphazene conduits allowed the use of neurite-promoting factors.     

Long-term evaluation of nerve regeneration in a biodegradable nerve guide

Nerve regeneration using artificial biodegradable conduits is of increasing interest. The aim of this study is to evaluate the regeneration and maturation of a nerve after long-term implantation (2 years) of a biodegradable poly-L-lactide/poly-e-caprolactone (PLLA/PCL) copolymeric nerve guide in the sciatic nerve of the rat. After harvesting, we evaluated both the regenerated nerves and the controls, using light microscopy, transmission electron microscopy, and morphometric techniques. Remnants of biomaterial were still present after 2 years of implantation, but the foreign body reaction was very mild at this stage, due to the rounded shapes of the polymer debris. Morphometric analysis showed significant differences between the regenerated nerve and the normal sciatic nerve: the number of myelinated fibers is higher, and the mean fiber diameter of the myelinated fibers in the regenerated nerve is smaller. In conclusion, the results demonstrate that the new PLLA/PCL nerve guide can provide optimal conditions for regeneration and maturation of damaged nerves. © 1993 Wiley-Liss Inc.     

Effect of local administration of cyclosporine A on peripheral nerve regeneration in a rat sciatic nerve transection model

Objective： To assess the effect of cyclosporine A （CsA） loaded in chitosan conduit on bridg- ing the sciatic nerve defects in a rat model. Methods： A 10 mm sciatic nerve defect was bridged using a chitosan conduit filled with 10 μl carrier-drug dilu- tion （10 pg/L CsA）. In control group, the conduit was filled with the same volume of carrier dilution alone. The regene- rated fibers were studied 4, 8 and 12 weeks after surgery. Results： The functional study confirmed faster recov- ery of the regenerated axons in treatment group than control group （P〈0.05）. There was statistically significant differ- ence of the gastrocnemius muscle weight ratios between treatment and control groups （P〈0.05）. Morphometric indi-ces of regenerated fibers showed that the number and diam- eter of the myelinated fibers in CsA-treated animals were significantly higher than those in control group. In immunohistochemistry, the location of reactions to S-100 in CsA group was clearly more positive than control group. Conclusion： CsA loaded in a chitosan conduit results in improvement of functional recovery and quantitative mor- phometric indices of sciatic nerve. It is easily available with- out any complications compared with its systemic administration.     

AxCA-脑源性神经营养因子转染大鼠损伤坐骨神经后基因表达的检测

目的观察携带小鼠脑源性神经营养因子（BDNF）cDNA表达片段的非依赖辅助复制缺陷型重组腺病毒载体（AxCA）-BDNF转染大鼠坐骨神经后基因表达情况。方法成年大鼠随机分成A组（坐骨神经缺损＋硅胶管＋AxCA-BDNF原液8μl）；B组（坐骨神经缺损＋硅胶管＋BDNF溶液8μl）；C组（坐骨神经缺损＋硅胶管＋空白病毒稀释液8μl）三组。应用原位杂交和免疫组织化学检测方法，从BDNF mRNA和蛋白水平，进行坐骨神经损伤后BDNF基因表达的定性和半定量分析测定。结果伤后腺病毒介导的BDNF基因转移组，在3、7、14d、1个月，4个时相点，近、远端神经干和脊髓（L3-6）中BDNF mRNA水平均远远高于其他两组，BDNF的水平也远远高于作为对照的单纯硅胶管套接组。结论通过腺病毒介导转染的BDNF基因在大鼠坐骨神经SCs内得到了有效表达，并通过轴突逆行转运到了相应的脊髓神经元。     

Large-area irradiated low-level laser effect in a biodegradable nerve guide conduit on neural regeneration of peripheral nerve injury in rats

This study used a biodegradable composite containing genipin-cross-linked gelatin annexed with β-tricalcium phosphate ceramic particles (genipin-gelatin-tricalcium phosphate, GGT), developed in a previous study, as a nerve guide conduit. The aim of this study was to analyse the influence of a large-area irradiated aluminium-gallium-indium phosphide (AlGaInP) diode laser (660 nm) on the neural regeneration of the transected sciatic nerve after bridging the GGT nerve guide conduit in rats. The animals were divided into two groups: group 1 comprised sham-irradiated controls and group 2 rats underwent low-level laser (LLL) therapy. A compact multi-cluster laser system with 20 AlGaInP laser diodes (output power, 50 mW) was applied transcutaneously to the injured peripheral nerve immediately after closing the wound, which was repeated daily for 5 min for 21 consecutive days. Eight weeks after implantation, walking track analysis showed a significantly higher sciatic function index (SFI) score (P < 0.05) and better toe spreading development in the laser-treated group than in the sham-irradiated control group. For electrophysiological measurement, both the mean peak amplitude and nerve conduction velocity of compound muscle action potentials (CMAPs) were higher in the laser-treated group than in the sham-irradiated group. The two groups were found to be significantly different during the experimental period (P < 0.005). Histomorphometric assessments revealed that the qualitative observation and quantitative analysis of the regenerated nerve tissue in the laser-treated group were superior to those of the sham-irradiated group. Thus, the motor functional, electrophysiologic and histomorphometric assessments demonstrate that LLL therapy can accelerate neural repair of the corresponding transected peripheral nerve after bridging the GGT nerve guide conduit in rats.     

A prospective clinical evaluation of biodegradable neurolac nerve guides for sensory nerve repair in the hand

PURPOSE: Our purpose was to study the recovery of sensory nerve function after treatment of traumatic peripheral nerve lesions with a biodegradable poly(DL-lactide-epsilon-caprolactone) Neurolac nerve guide (Polyganics B.V., Groningen, the Netherlands) versus the current standard reconstruction techniques. METHODS: Thirty patients with 34 nerve lesions were included in this randomized, multicenter trial. RESULTS: Both groups were comparable considering their demographics. After a small learning curve the nerve guide could be implanted easily. There were more complications in the experimental group but none of them was directly device related. Recovery of sensibility in the nerve guide group was at least as good as in the control group. CONCLUSIONS: These results indicate that the Neurolac nerve guide is suitable for the repair of transected peripheral nerves in the hand.     

Functional nerve recovery after bridging a 15 mm gap in rat sciatic nerve with a biodegradable nerve guide

Recovery of nerve function was evaluated after bridging a 15?mm sciatic nerve gap in 51 rats with a biodegradable poly(DL-lactide-ε-caprolactone) nerve guide. Recovery of function was investigated by analysing the footprints, by analysing video recordings of gait, by electrically eliciting the withdrawal reflex, by nerve conduction velocity and by electromyography (EMG). Sensory nerve function recovered as measured by electrostimulation. Motor nerve function partly recovered but electromyograms remained abnormal throughout the study. We conclude that functional reinnervation by regenerating axons occurs after bridging a 15?mm nerve gap with a biodegradable poly(DL-lactide-ε-caprolactone) nerve guide, but the walking patterns remain abnormal. Video analysis is a useful tool to record and analyse the walking patterns of rats. Further studies are necessary to investigate the possibility of obtaining selective reinnervation of specific muscles.     

电针对大鼠坐骨神经再生影响的功能评价

目的从功能恢复评价电针对神经再生的促进作用。方法建立大鼠坐骨神经损伤模型，将９０只ＳＤ大鼠随机分为损伤对照组和电针组两组。分别于术后２、４、６、１０周测定运动神经传导速度、小腿三头肌肌力及坐骨神经功能指数，并以自身健侧作对照得出其恢复率。同时测定术后１周感觉神经再生的距离。结果电针组术后１周感觉神经再生距离及２、４、６、１０周运动神经传导速度、肌力、ＳＦＩ等的恢复率均明显优于对照组。结论电针可以促进损伤神经的再生，明显提高神经功能的恢复     

Functional nerve recovery after bridging a 15 mm gap in rat sciatic nerve with a biodegradable nerve guide.

Recovery of nerve function was evaluated after bridging a 15 mm sciatic nerve gap in 51 rats with a biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guide. Recovery of function was investigated by analysing the footprints, by analysing video recordings of gait, by electrically eliciting the withdrawal reflex, by nerve conduction velocity and by electromyography (EMG). Sensory nerve function recovered as measured by electrostimulation. Motor nerve function partly recovered but electromyograms remained abnormal throughout the study. We conclude that functional reinnervation by regenerating axons occurs after bridging a 15 mm nerve gap with a biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guide, but the walking patterns remain abnormal. Video analysis is a useful tool to record and analyse the walking patterns of rats. Further studies are necessary to investigate the possibility of obtaining selective reinnervation of specific muscles.     

Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration

Normal and electrically stimulated PC12 cell cultures and the implantation of nerve guidance channels were performed to evaluate newly developed electrically conductive biodegradable polymer composites. Polypyrrole (PPy) doped by butane sulfonic acid showed a significantly higher number of viable cells compared with PPy doped by polystyrenesulfonate after a 6-day culture. The PC12 cells were left to proliferate for 6 days, and the PPy-coated membranes, showing less initial cell adherence, recorded the same proliferation rate as did the noncoated membranes. Direct current electricity at various intensities was applied to the PC12 cell-cultured conductive membranes. After 7 days, the greatest number of neurites appeared on the membranes with a current intensity approximating 1.7-8.4 microA/cm. Nerve guidance channels made of conductive biodegradable composite were implanted into rats to replace 8 mm of sciatic nerve. The implants were harvested after 2 months and analyzed with immunohistochemistry and transmission electron microscopy. The regenerated nerve tissue displayed myelinated axons and Schwann cells that were similar to those in the native nerve. Electrical stimulation applied through the electrically conductive biodegradable polymers therefore enhanced neurite outgrowth in a current-dependent fashion. The conductive polymers also supported sciatic nerve regeneration in rats.     

Morphometric study of regeneration through vascularized nerve graft in a rabbit sciatic nerve model

Adequate vascularization is essential for a successful nerve graft. Theoretically, immediate vascularization will minimize fibroblast infiltration and support axonal regeneration. In this study, histomorphologic and morphometric studies were carried out to determine whether vascularized grafts are beneficial, in terms of axonal regeneration. In a rabbit model, 4-cm segments of sciatic nerve were obtained and placed as a nonvascularized graft on one side, and as a pedicled vascularized graft fed by the inferior gluteal vessel on the contralateral side. Histomorphologically, the distribution of myelinated nerve fibers and Schwann cells was evaluated after toluidine blue staining, at 2-, 3-, and 4-month intervals. The following results were obtained. 1) Myelinated nerve fibers were more abundant in the proximal, middle, and distal segments of the vascularized nerve group at 2 and 3 months. 2) The average nerve-fiber diameter was greater in the vascularized nerve graft group at 2, 3, and 4 months (2 to 10 microm). 3) Schwann cells were more abundant in the proximal, middle, and distal segments of the vascularized nerve graft group at all time points. Based on the above findings, the immediate restoration of circulation in the vascularized nerve graft can be accountable for the increased number of surviving Schwann cells, the rapid clearing of axons, and myelin-sheath changes that occur during Wallerian degeneration, thus enabling "morphologically" optimal regeneration.     

Clinical evoked potential research on the regeneration process in peripheral nerve injury

The examining results of SNAP, MAP and SEP of 239 median nerves and 76 ulnar nerves injuries are reported. Among those patients whose curative effects of complete severed nerves have reached "good" or above, SEP could be evoked in third month after suturing, MAP began to appear in sixth month and could be monitored in almost all patients in tenth month. On the other hand, SNAP was more difficult to evoke, only 2 cases could be recorded in tenth month, the figure came to about 80% after 4 years, and it could not be recorded in a few patients even after 10 years. While the clinical curative effects changed, the recovery rate of evoked potential changed accordingly. It has been proved the examination of evoked potential has important reference value to the diagnosis, treatment, regeneration and prognosis evaluation of peripheral nerve injury.