Functional assessment of sciatic nerve recovery: biodegradable poly (DLLA-epsilon-CL) nerve guide filled with fresh skeletal muscle

The aim of this study was to compare functional peripheral nerve recovery in the rat sciatic nerve model after reconstruction of a 10-mm gap with a biodegradable poly (DLLA-epsilon-CL) nerve guide, as filled with either fresh skeletal muscle or phosphate-buffered saline (PBS). During 24 weeks of recovery, motor and sensory functional evaluation was tested by extensor postural thrust (EPT) and withdrawal reflex latency (WRL), respectively. At the end of the experiment, anesthetized animals were prepared for motor nerve conduction velocity (MNCV) studies, followed by gastrocnemius and soleus muscle weight measurement. Motor functional recovery was greater in the muscle-grafted group, and reached a significant difference from weeks 8-12 (P < 0.05). The results of this investigation suggest that filling a nerve guide with fresh skeletal muscle induces faster maturation of regenerated nerve fibers in comparison with traditional tubular repair.     

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.     

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.     

Long-term evaluation of functional nerve recovery after reconstruction with a thin-walled biodegradable poly (DL-lactide-epsilon-caprolactone) nerve guide, using walking track analysis and electrostimulation tests.

This study was performed to evaluate the long-term functional nerve recovery after reconstruction of a 10-mm gap in the sciatic nerve of the rat, with a thin-walled nerve guide, composed of a biodegradable copolymer of DL-lactide and epsilon-caprolactone [p(DLLA-epsilon-CL)]. To evaluate both motor and sensory nerve recovery, walking track analysis and electrostimulation tests were carried out after implantation periods ranging from 3 to 52 weeks postoperatively. The first signs of both motor and sensory nerve recovery could be observed after 5 weeks. After 15 weeks, 70% of the sciatic function and 90% of the sensory nerve function had been recovered. After this period, the sciatic function index (SFI) did not improve further, whereas the sensory nerve function appeared to return to normal. When the results of the SFI measurements, minus those obtained from rats with severe automutilation, are extrapolated, further improvement of the SFI might be expected after 52 weeks. The fact that 100% sensory nerve recovery was obtained, as measured by the electrostimulation test, could be explained by sensory reinnervation from surrounding areas. The SFI was not fully reestablished because automutilation had a great impact on the use of walking track assessment.     

Secondary digital nerve repair in the foot with resorbable p(DLLA-epsilon-CL) nerve conduits

Nerve guides are increasingly being used in peripheral nerve repair. In the last decade, much preclinical research has been undertaken into a resorbable nerve guide composed of p(DLLA-epsilon-CL). This report describes the results of secondary digital nerve reconstruction in the foot in a patient with post-traumatic neuromas of the common plantar digital nerves II-III and III-IV. The neuromas were resected and reconstruction of the nerves was carried out with resorbable Neurolac nerve guides. The Pressure Specified Sensory Device was used to measure the static (s) and moving (m) 1- and 2-point discrimination (PD). Fourteen months after nerve repair, the m1-PD returned in all digital nerves. The s1-PD returned only on the lateral side of the second toe. The m2-PD and s2-PD did not return in any of the toes originally innervated by the reconstructed nerves. According to the British Classification System, the sensory nerve recovery was poor. However, there were no complaints of painful neuromas after this procedure. In conclusion, this report shows no beneficial effects of Neurolac nerve guides in terms of return of sensibility after repair of common plantar digital nerves. Painful neuromas, however, could be well-treated.     

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.     

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.     

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.     

Nerve regeneration through a two-ply biodegradable nerve guide in the rat and the influence of ACTH4-9 nerve growth factor.

Biodegradable polyurethane-based (PU) nerve guides, instilled with or without ACTH4-9 analog (a melanocortin) were used for bridging an 8 mm gap in the rat sciatic nerve and were evaluated for function and histological appearance after 16 weeks of implantation. Autologous nerve grafts functioned as controls. The guides successfully enabled the sciatic nerve to regenerate across the 8 mm gap, thus effectively reestablishing the contact between the proximal and distal nerve ends. The mean conduction velocity, motor latency, and muscle action potentials of all the nerve guides did not differ significantly from the autografts. The histological quality of the regeneration in the nerve guides was significantly better than in the autografts; in the nerve guides, a well-defined nerve cable of normal architecture had regenerated without extensive endoneural scarring as seen in the autografts. ACTH4-9 instilled in the nerve guides showed a slight, but significant, increase in the number of myelinated axons. It is concluded that biodegradable PU nerve guides result in similar functional recovery when compared with autografts, but their histological quality is significantly better. ACTH4-9 showed only slight, but significant, improved nerve growth promoting activity. Therefore biodegradable PU nerve guides with ACTH4-9 would appear to be promising alternatives to autografts for bridging nerve defects.     

甲壳素涂层PGLA神经导管修复兔面神经缺损的实验研究

目的:探讨甲壳素涂层PGLA神经导管修复兔面神经缺损的效果。方法:成年雄性新西兰兔24只,无菌条件下切断双侧面神经下颊支,制成15mm的兔面神经下颊支缺损模型。左侧用甲壳素涂层聚丙交脂-乙交脂共聚物[poly(L-lactide-co-glycolide),PGLA]神经导管修复;右侧用翻转自体神经修复作为对照。术后5周、10周和14周行大体观察、电生理检查、组织学、电镜观察评价修复效果。结果:术后5周观察到神经导管中有新生轴索通过,再生神经发育不成熟;右侧自体神经修复近段有髓神经纤维均匀疏散分布,远段未见明显再生神经束形成。术后14周左侧再生神经已通过神经导管长入远端,电生理检查结果表明自体神经修复侧再生神经质量优于神经导管修复侧,差异有统计学意义(P<0.01)。自体神经修复再生纤维密度优于神经导管修复侧,差异有统计学意义(P<0.01),但自体神经修复侧近段神经髓鞘部分空泡样变性及脱髓鞘改变,远段再生神经纤维束形成少,面肌联带运动程度较导管修复侧严重。结论:甲壳素涂层PGLA神经导管能有效修复周围神经缺损,有望替代自体神经移植。     

GaAs (904-nm) laser radiation does not affect muscle regeneration in mouse skeletal muscle.

BACKGROUND AND OBJECTIVE: We evaluated the effect of GaAs (904-nm) laser, applied directly to the skin of injured muscle, in muscle regeneration. STUDY DESIGN/MATERIAL AND METHODS: Muscle injury was induced in the Tibialis anterior (TA) muscle by ACL myotoxin (5 mg/kg). Two groups were irradiated with doses of 3 (n = 8) and 10 J/cm(2)(n = 8). GaAs laser (power 1.5 mW, intensity 7.5 mW/cm(2), spot 0.2 cm(2)) was applied daily for five days. Contralateral TA received a sham procedure. RESULTS: Similar morphological aspects were found in both laser irradiated and sham muscles. No differences were found in the muscle weight, but animals irradiated with 10 J/cm(2) showed a significant gain of body weight (P = 0.002). CONCLUSIONS: Doses of 3 and 10 J/cm(2) of GaAs laser were not efficient to promote significant morphological changes in the regenerated skeletal muscle, but the dose of 10 J/cm(2) promoted significant gain of body weight.     

Polarization of nerve regeneration (electrotaxis)

Regeneration of both median nerves was studied in the rat in three different experimental models of centrocentral anastomosis through an interposed segment of pre-degenerated tibial nerve after denervation by spinal root transection. Different patterns of regeneration were observed in the anastomoses. These patterns suggest a bio-electrical polarity related to neuronal function. The present experimental model appears to offer a new opportunity to study neuronal regeneration under the influence of defined bioelectrical conditions.     

An electron microscopic study of local anesthetic-induced skeletal muscle fiber degeneration and regeneration in the monkey

An electron microscopic study was done on abductor pollicis brevis muscles of 18 Rhesus monkeys after intramuscular injections of 0.75% bupivacaine, 2% mepivacaine, or 2% lidocaine + epinephrine. The muscles were examined for from 2 h to 28 days. Severe muscle fiber damage, consisting of breakdown of sarcolemma and myofibrils, was seen as early as 2 h. Phagocyte mediated fragmentation of the degenerating muscle fibers was at its peak during the third and fourth days. Myoblasts were abundant during the fourth day. Early myotubes appeared on the fifth and sixth days, and they matured during the second week. Satellite cells appeared alongside mature myotubes. Overall, the local anesthetic-induced breakdown and regeneration of skeletal muscle fibers in the monkey followed a course quite similar to that seen in the rat.     

Nerve regeneration across a 2-cm gap in the rat median nerve using a resorbable nerve conduit filled with Schwann cells

OBJECT: In a rat model, nerve regeneration was evaluated across a 2-cm defect in the median nerve by using a resorbable artificial nerve conduit. The aim of this study was to develop an artificial, biocompatible nerve guide to induce regeneration in the peripheral nervous system. METHODS: The authors compared a nerve conduit of trimethylenecarbonate-co-epsilon-caprolactone (TMC/CL) filled with autologous Schwann cells with both an empty hollow conduit and an autologous nerve graft. Animals that did not undergo surgery served as the control group. Nerve regeneration was evaluated with the grasping test, histological analysis of the nerve, muscle weight analysis (flexor digitorum superficialis muscle), and electrophysiological examination. After an observation period of 9 months, regeneration occurred only in animals that had received an autologous graft or a Schwann cell containing nerve conduit. No signs of regeneration were found in animals supplied with the empty conduit. CONCLUSIONS: Results of this study reveal the important role of Schwann cells in the regeneration process across a 2-cm defect in the rat median nerve. Furthermore, Schwann cell-filled nerve conduits induced functional recovery, as demonstrated in the grasping test, that was comparable with that of the autologous graft 9 months after implantation.     

Nerve conduit filled with GDNF gene-modified Schwann cells enhances regeneration of the peripheral nerve

A recombinant retrovirus vector containing the glial cell line-derived neurotrophic factor (GDNF) gene was constructed and transfected into Schwann cells (SCs) to investigate the possibility of GDNF transfection and functional expression of transfected SCs, including GDNF secretion and its mRNA expression. We found that transfection of the GDNF gene into SCs led to significantly enhanced expression of GDNF mRNA. The rate of GDNF secretion by GDNF-SCs was also increased. Functionally, more surviving motoneurons were seen when they were cocultured in GDNF-SC-conditioned medium than when they were in normal SC-conditioned medium. When bridging a rat sciatic nerve defect with a conduit filled with GDNF-transfected SCs, nerve regeneration was better than that of the control. In conclusion, transfection of SCs with the GDNF gene could enhance SC function. Application of genetically modified SCs could be a better way to promote nerve regeneration.     

Expression of N-cadherin by skeletal muscle in the degenerationand the degeneration/regeneration processes after nerve injury

We investigated the expression of N-cadherin by skeletal muscle during the degeneration and degeneration/regeneration processes using the rat sciatic nerve and gastrocnemius muscle model. The right sciatic nerve was exposed in the mid-thigh region, and the nerve was transsected with small scissors. After then, nerve was sutured (sutured group), or both edges of the resected nerve were turned and sutured to the muscle of each side (unsutured group). At various periods up to 24 weeks after the operation the middle portion of the gastrocnemius muscle of the treated hindlimbs was removed. Expression of N-cadherin was detected by western blot analysis and immunofluorescent staining with an anti N-cadherin antibody. In the both groups, the degree of expression had already increased by the end of the first postoperative week, but there were no significant differences between the first and second postoperative weeks between the two groups. However, the values recorded at the fourth, sixth, ninth, and twelfth postoperative weeks were significantly higher in the unsutured group than in the sutured group. Immunofluorescent staining was present around the muscular membrane in all specimens including the control. These results indicated that there was a difference in the kinetics of expression of N-cadherin in skeletal muscle between the degeneration and degeneration/regeneration processes of the muscle after injury to the nerve. It was also clear that N-cadherin has a role at the surface of the muscle cell in skeletal muscle, not in the satellite and inflammatory cells, in both groups.     

In vitro and in vivo evaluation of a biodegradable chitosan-PLA composite peripheral nerve guide conduit material

Chitosan, a nature biodegradable material, has good biocompatibility but poor physical properties to serve as a nerve conduit. In this study, polylactic acid (PLA) was added to chitosan to form a composite material with improved intensity and elasticity, to be used as nerve conduits. The chitosan-PLA nerve conduits were fabricated with a mold casting/infrared dehydration technique. The constituent ratio of PLA and chitosan of 1:5 (v:v) was chosen to give the composite material both good mechanical properties and good biocompatibility. An in vitro cytotoxicity test showed that the chitosan-PLA material was not cytotoxic. The conduits were proved biodegradable and had many micropores to allow permeability. We evaluated chitosan-PLA nerve conduits as a guidance channel to repair 10 mm gaps in rat sciatic nerves. Nerve autograft and silicon conduits were used as the control. After 12 weeks, the regenerating nerves in three groups succeeded in passing through the nerve gap and reinnervating the muscle. Assessments, including ECG, histomorphometric evaluation, and weighing of triceps calf muscle, showed that the functional recovery of sciatic nerve was better in chitosan-PLA conduit group than in the silicon conduit group (P < 0.05), but the differences between the chitosan-PLA conduit group and the nerve autograft group were not significant (P > 0.05). Therefore, the chitosan-PLA guide proved to be a promising nerve conduit.     

Experimental study of bridging the peripheral nerve gap with skeletal muscle

A piece of skeletal muscle was used as a conduit to bridge the gap microsurgically between the two ends of the severed sciatic nerve in 30 rats, and a method for histochemical demonstration of acetylcholinesterase was employed to assess the nerve regeneration process 5 weeks or more after the operation. Regenerating nerve fibers were detected in the muscle and could be traced through to the distal stump of the severed sciatic nerve. This suggests that skeletal muscle might serve as a grafting conduit for the repairing of peripheral nerve injuries.