Sciatic nerve regeneration in ganglioside-treated rats

Local application of 0.25 mg ganglioside to the site of a crush in the rat sciatic nerve resulted in a 19 to 33% increase in the number of regenerating axons at 7 days after the lesion, although the maximum axonal outgrowth distance was not affected. Intraperitoneal injection of ganglioside (50 mg/kg) also had no effect on axonal outgrowth distance.     

Sciatic nerve regeneration in rats induced by transplantation of in vitro differentiated bone-marrow stromal cells

Bone marrow stromal cells (MSCs) are multipotent stem cells that have the potential to differentiate into bone, cartilage, fat and muscle. We now demonstrate that MSCs can be induced to differentiate into cells with Schwann cell characteristics, capable of eliciting peripheral nervous system regeneration in adult rats. MSCs treated with beta-mercaptoethanol followed by retinoic acid and cultured in the presence of forskolin, basic-FGF, PDGF and heregulin, changed morphologically into cells resembling primary cultured Schwann cells and expressing p75, S-100, GFAP and O4. The MSCs were genetically engineered by transduction with retrovirus encoding green fluorescent protein (GFP), and then differentiated by treatment with factors described above. They were transplanted into the cut ends of sciatic nerves, which then responded with vigorous nerve fibre regeneration within 3 weeks of the operation. Myelination of regenerated fibers by GFP-expressing MSCs was recognized using confocal and immunoelectron microscopy. The results suggest that MSCs are able to differentiate into myelinating cells, capable of supporting nerve fibre re-growth, and they can therefore be applied to induce nerve regeneration.     

Sciatic nerve regeneration using a nerve growth factor-containing fibrin glue membrane

Our previous findings confirmed that the nerve growth factor-containing fibrin glue membrane provides a good microenvironment for peripheral nerve regeneration; however, the precise mechanism remains unclear, p75 neurotrophin receptor （p75NTR） plays an important role in the regulation of peripheral nerve regeneration. We hypothesized that a nerve growth factor-containing fibrin glue membrane can promote neural regeneration by up-regulating p75NTR expression. In this study, we used a silicon nerve conduit to bridge a 15 mm-long sciatic nerve defect and injected a mixture of nerve growth factor and fibrin glue at the anastomotic site of the nerve conduit and the sciatic nerve. Through RT-PCR and western blot analysis, nerve growth factor-containing fibrin glue membrane significantly increased p75NTR mRNA and protein expression in the Schwann cells at the anastomotic site, in particular at 8 weeks after injection of the nerve growth factor/fibrin glue mixture. These results indicate that nerve growth factor-containing fibrin glue membrane can promote peripheral nerve regeneration by up-regulating p75NTR expression in Schwann cells.     

Sciatic nerve regeneration is accelerated in galectin-3 knockout mice

The success of peripheral nerve regeneration depends on intrinsic properties of neurons and a favorable environment, although the mechanisms underlying the molecular events during degeneration and regeneration are still not elucidated. Schwann cells are considered one of the best candidates to be closely involved in the success of peripheral nerve regeneration. These cells and invading macrophages are responsible for clearing myelin and axon debris, creating an appropriate route for a successful regeneration. After injury, Schwann cells express galectin-3, and this has been correlated with phagocytosis; also, in the presence of galectin-3, there is inhibition of Schwann-cell proliferation in vitro. In the present study we explored, in vivo, the effects of the absence of galectin-3 on Wallerian degeneration and nerve-fiber regeneration. We crushed the sciatic nerves of galectin-3 knockout and wild-type mice, and followed the pattern of degeneration and regeneration from 24 h up to 3 weeks. We analyzed the number of myelinated fibers, axon area, fiber area, myelin area, G-ratio and immunofluorescence for β-catenin, macrophages and Schwann cells in DAPI counterstained sections. Galectin-3 knockout mice showed earlier functional recovery and faster regeneration than the wild-type animals. We concluded that the absence of galectin-3 allowed faster regeneration, which may be associated with increased growth of Schwann cells and expression of β-catenin. This would favor neuron survival, followed by faster myelination, culminating in a better morphological and functional outcome.     

Discomfort after fascicular sural nerve biopsy

Sural nerve biopsy may, in selected cases, give valuable information in the investigation of patients with polyneuropathy. The prevalence and severity of patient discomfort after fascicular nerve biopsy was investigated in 67 patients by a mailed questionnaire. A lasting (greater than 6 months) significant discomfort was found in 6 patients (11%), in 3 of these the symptoms were graded as severe. Thus, sural nerve biopsy should be limited to cases in which important information may be expected and the patients should be carefully informed of the risks of long-lasting discomfort.     

The effects of an autologous transplant on patterns of regeneration in rat sciatic nerve

Autologous transplants are often used in repair of peripheral nerve injury. Quantitative evaluation of the results of such a transplant is obviously desirable. In previous study, we determined numerical and cytologic parameters of the regeneration that followed transection of rat sciatic nerve, but no transplant was used. This work now serves as a basis for evaluating the use of an autologous transplant in the same transection paradigm. Our procedure is to remove 8 mm of sciatic nerve in the thigh. The removed segment is then put into the center of a silicone tube and the proximal and distal stumps of the severed nerve are placed into the ends of the tube. The data show: (1) a high percentage of successful regenerations; (2) a relatively large nerve in the gap; (3) a typical outer perineurium underlying the epineurium; (4) a well-developed fascicular perineurium; and (5) approximately equal numbers of myelinated and unmyelinated axons in the gap and distal stump. If a transplant is not used there are: (1) a greater number of failures of regeneration; (2) a smaller nerve in the gap; (3) a less well-developed fascicular perineurium; (4) unequal numbers of axons in the gap as compared to the distal stump; and (5) no outer perineurium forms. The presence of a typical outer perineurium after a transplant and its absence if a transplant is not used is probably the most striking cytologic difference between the two paradigms. The equal numbers of axons in the gap and distal stump following regeneration after transplantation presumably indicate that all axons in the gap enter the distal stump without branching or ending blindly, a situation that is presumably beneficial and contrasts with the findings when a transplant is not used. Both paradigms show a remarkable increase in the density of blood vessels in the regenerated nerve in the gap between the two stumps. These findings will serve as a basis for further studies on the mechanisms of peripheral nerve regeneration.     

Spontaneous axonal regeneration after optic nerve injury in adult rat

Optic nerves of adult rats were crushed 2 mm behind the eye to examine the ability of retinal ganglion cells (RGCs) to regenerate their axons. Some animals were treated with the immunophilin ligands FK 506 or GPI 1046 for up to 4 weeks. After 10 days to 16 months, regenerating RGC axons were visualized using anterograde tracing and/or electron microscopy. A small proportion of RGC axons regenerated across the lesion site and grew very slowly along the entire optic nerve. Immunophilin ligands had no obvious effect. The regenerating axons were about 0.2 microm in diameter, and usually in clusters surrounded by astrocyte processes. Thus, some CNS axons can spontaneously regenerate long distances within degenerate white matter and this slow regeneration is not accelerated by immunophilin ligands.     

Variability in the extent of sensory deficit after sural nerve biopsy

BACKGROUND: Sural nerve biopsy (SNBx) is associated with multiple complications such as paresthesia, pain, or numbness in the sural nerve distribution at the site of biopsy and wound infection. An accurate idea of these adverse events would be useful while taking informed consent from patients. AIMS: We conducted a prospective study to determine the extent of sensory deficits after SNBx. SETTINGS AND DESIGN: It is a prospective, hospital-based (tertiary teaching hospital) study. MATERIALS AND METHODS: All the patients who had SNBx between May 2003 and March 2004 were eligible for inclusion. However, patients with sensory impairment in sural nerve territory or abnormal sural nerve conduction studies prior to the procedure were excluded. SNBx was performed in the ankle region under local anesthesia, and a 3 cm nerve segment was excised. Touch, pain, temperature, vibration and joint position were tested after the nerve biopsy. The extent of sensory deficit was determined. Any other complications, when present were also noted. Follow-up assessment was performed at three months or later. RESULTS: Fifty patients (26 women) fulfilled the inclusion and exclusion criteria. The mean age was 37.4 (16-63) years. One-two weeks after the SNBx, 46 (92%) patients had sensory deficit along the lateral aspect of the foot at the site of the biopsy, and 48 (96%) patients had sensory impairment extending beyond the outer aspect of the fifth toe. At follow-up, sensory deficit was present in 89% patients and paresthesia in 39%. CONCLUSIONS: The majority of the patients undergoing SNBx develop persistent sensory deficits, which often extend beyond the typical sural nerve territory.     

Relationship of myelin internode elongation and growth in the rat sural nerve

The lengthening of myelin internodes along peripheral nerve fibers was studied in rat sural nerve during the period of myelination and subsequent growth. Sural nerves were examined from 34 animals ranging in age from 2 to 140 days. Analyses of osmicated, epon-embedded and transversely sectioned nerves indicated that myclination of rat sural nerve commenced in the two to five day period and continued until day 20. Direct measurements of consecutive myelin internodes along representative teased fibers disclosed a progressive increase of internode length and fiber diameter. A direct relationship was shown between the rate of increment of the largest internodes and the longitudinal growth rate of the rat hind limb as determined by the combined lengths of the disarticulated femur and tibia. Increases of internode lengths among the entire population of myelinated fibers also appeared to correlate with the longitudinal growth pattern of the hind limb. This was assessed by comparing the size distribution of myelinated fibers in adult sural nerve with a theoretical distributional profile based upon the assumption that internode length is solely determined by amount of longitudinal growth after myelination. Assuming that internode elongation is determined by growth, it was shown that the quantity of longitudinal growth after myelination could account for the size and distribution of all myelin internodes in the adult sural nerve. In addition, the relationships between myelin internodes and fiber size at different ages was expressed by slopes of the regression lines. A significant change in this value for sural nerve fibers in the 30–40 day age period indicated that there was an increase of composite fiber diameter relative to internode length during the interval. During the remaining periods of growth, the diameters of myelinated fibers increased at a rate comparable to the increase of internode length.     

Motor fibers in the sural nerve

Summary In an ischemia-induced model of an acute motor neuron disorder, there is anterior horn cell damage with Wallerian degeneration in ventral roots; dorsal root ganglia and dorsal roots are unaffected. In a mixed nerve there is axonal degeneration reflecting loss of motor fibers. The sural nerve is normal showing that it does not contain motor fibers. This observation is relevant to the neuropathology of motor neuron disease where axonal degeneration found in the sural nerve suggests involvement of sensory fibers.Portions of this paper were presented at the 37th Annual Meeting of the American Academy of Neurology in Dallas, Texas in April 1985     

The effects of 2,5-hexanedione on axonal regeneration after nerve crush in the rat

The pattern of recovery of myelinated axons in the posterior tibial nerve after crushing was studied in rats chronically intoxicated with 2,5-hexanedione. It was given for 2 weeks before crushing (200 mg/kg i.p. 5 times a week) or additionally for two further weeks after the nerve crush. Two animals were examined from each group at approximately 1,2,3,4 and 8 weeks later. Return of function in poisoned animals was slower than in the controls. The numbers of regenerating myelinated fibres was severely reduced in poisoned animals up to 4 weeks later, but by 8 weeks the numbers equalled those in the control nerves. Marked impairment of initiation of neurite outgrowth was found, but once begun, axonal growth was comparable to controls and myelination occurred normally. Above the crush for 10 mm, filament-filled axonal swellings were found in poisoned animals accompanied by varying amounts of retrograde axonal degeneration. These findings are discussed in relation to the role of normal neurofilaments in axonal growth and the effects of probably cross-linking of these by 2,5-hexanedione on regenerating neurites.     

Optic nerve regeneration with return of vision through an autologous peripheral nerve graft

The optic fiber termination layer in the contralateral optic tectum was reinnervated and useful vision was recovered in the adult frog, after successful optic nerve regeneration through an autologous peripheral nerve-bridge used to replace the optic nerve and optic chiasma. During their course through the nerve-bridge, the optic fibers were associated with Schwann cells in the usual relationship observed in peripheral nerve.     

Shock wave treatment improves nerve regeneration in the rat

Introduction: The aims of the experiments were to: (1) determine whether low‐energy shock wave treatment accelerates the recovery of muscle sensitivity and functionality after a nerve lesion; and (2) assess the effect of shock waves on the regeneration of injured nerve fibers. Methods: After compression of a muscle nerve in rats the effects of shock wave treatment on the sequelae of the lesion were tested. In non‐anesthetized animals, pressure pain thresholds and exploratory activity were determined. The influence of the treatment on the distance of nerve regeneration was studied in immunohistochemical experiments. Results: Both behavioral and immunohistochemical data show that shock wave treatment accelerates the recovery of muscle sensitivity and functionality and promotes regeneration of injured nerve fibers. Conclusion: Treatment with focused shock waves induces an improvement of nerve regeneration in a rodent model of nerve compression. Muscle Nerve 47: 702–710, 2013     

Nerve guides seeded with autologous schwann cells improve nerve regeneration

This study evaluates the ability of Schwann cells (SCs) transplanted into a nerve guide to improve regeneration and reinnervation after sciatic nerve resection and repair, leaving a 6-mm gap, in the mouse. SCs were isolated from predegenerated adult sciatic nerves and expanded in culture using a chemically defined medium. Syngeneic, isogeneic, and autologous SCs were suspended in Matrigel and seeded in resorbable, permeable poly(l-lactide-co-epsilon-caprolactone) guides at 150,000 cells/tube. Guides containing SCs were compared to guides filled with Matrigel alone and with peroneal nerve autografts. Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, nociceptive, sensory, and motor functions in the hindpaw during 4 months postoperation. Morphological analysis of the regenerated nerves was performed at the end of follow-up. The group with an autograft achieved faster and higher levels of reinnervation and higher number of regenerated myelinated fibers than groups repaired by tubulization. The immunogenicity of transplanted SCs influenced the outcome of nerve regeneration. Transplants of autologous SCs resulted in slightly lower levels of reinnervation than autografts, but higher recovery and number of regenerated fibers reaching the distal nerve than transplants of isologous and syngeneic SCs, although most of the differences were not statistically significant. Syngeneic SCs did not improve regeneration with respect to acellular guides. Prelabeled transplanted SCs were found to survive into the guide 1-3 months after implantation, to a larger number when they were autologous than syngeneic. Cellular prostheses composed of a resorbable guide seeded with autologous SCs appear as an alternative for repairing long gaps in injured nerves, approaching the success of autografts.     

Axonal regeneration in the foot branch of the superficial peroneal nerve and the lateral plantar nerve of the rat after sciatic nerve lesions

Hand injuries with nerve lesions often leave the patient with a persistent sensory deficit, particularly with respect to glabrous skin. The present study examines axonal regeneration in the foot branch of the superficial peroneal nerve (fSPN) and the lateral plantar nerve (LPN), supplying hairy skin and glabrous skin together with some intrinsic muscles, respectively, after sciatic nerve lesions in the rat. Following crush lesions, the number of myelinated axons is normal in the fSPN, and the occurrence of C-fibers appears slightly reduced. In the LPN, the numbers of myelinated axons and C-fibers are both significantly increased. Post-crush regenerated myelinated fSPN and LPN axons show normal size ranges, but the proportion of small myelinated axons is increased. After neurotomy and suture, the numbers of myelinated axons and C-fibers in the fSPN are not significantly different from normal. The LPN exhibits a significantly increased number of myelinated axons, but the number of C-fibers is not significantly abnormal. In both nerves, the myelinated axons present an abnormally narrow size range. These findings show that the quantitative outcome of regeneration in a nerve innervating glabrous skin (and some intrinsic muscles) differs significantly from that of branches to hairy skin of the foot, with respect to myelinated as well as unmyelinated axons. To what extent these differences mirror functional differences awaits elucidation.     

Ipsilateral, cabled sural nerve for a sciatic nerve defect: an experimental model in the rat

The 10 mm rat sciatic nerve defect model is commonly used to investigate new strategies to improve functional recovery with segmental nerve defects. However, a lack of standardization makes comparisons between studies difficult. The present study aims to evaluate a standardized experimental model that can minimize the number of animals required for obtaining valid results and simulates a current treatment for human peripheral nerve injury defects. Eighteen cadaveric Sprague-Dawley rats were utilized in the anatomic arm of the study and 18 living Sprague-Dawley rats were used in the experimental arm. The results from the cadaveric study allowed us to create an ipsilateral, three-cable autologous sural nerve graft technique in the rat. This repair construct was evaluated with functional and histomorphometric analysis of nerve regeneration. The results support functional recovery of the sciatic nerve in all grafted animals. The use of an ipsilateral cabled sural nerve graft technique in the rat sciatic nerve defect model is a viable control group that utilizes a single incision, incurs minimal morbidity, and maintains muscle attachments. We conclude that this rat model can be used in various experimental trials in the field of peripheral nerve regeneration.