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Ghrelin is a circulating peptide hormone released by enteroendocrine cells of the gastrointestinal tract as two forms, acylated and unacylated. Acylated ghrelin (AG) binds to the growth hormone secretagogue receptor 1a (GHSR1a), thus stimulating food intake, growth hormone release, and gastrointestinal motility. Conversely, unacylated GHR (UnAG), through binding to a yet unidentified receptor, protects the skeletal muscle from atrophy, stimulates muscle regeneration, and protects cardiomyocytes from ischemic damage. Recently, interest about ghrelin has raised also among neuroscientists because of its effect on the nervous system, especially the stimulation of neurogenesis in spinal cord, brain stem, and hippocampus. However, few information is still available about its effectiveness on peripheral nerve regeneration. To partially fill this gap, the aim of this study was to assess the effect of UnAG on peripheral nerve regeneration after median nerve crush injury and after nerve transection immediately repaired by means of an end-to-end suture. To this end, we exploited FVB1 Myh6/Ghrl transgenic mice in which overexpression of the ghrelin gene (Ghrl) results in selective up-regulation of circulating UnAG levels, but not of AG. Regeneration was assessed by both functional evaluation (grasping test) and morphometrical analysis of regenerated myelinated axons. Results obtained lead to conclude that UnAG could have a role in development of peripheral nerves and during more severe lesions.

The rabbit has been proposed to represent an animal model that allows studying peripheral nerve regeneration across extended gap lengths. We describe here our experiences with the rabbit median nerve model and the obstacles it comes along with. This short communication is meant to inform the community and to prevent other researcher from investing time and animal lives in a model with low translational power., (© 2020 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons Ltd.)

Introduction: The aim of this research was to test, in an animal model, the nerve regeneration technique with a hypoallergenic acellular dermal matrix used to wrap the microsurgical neural suture., Materials and Methods: Two groups of rats received the cut of limb right median nerves. The regeneration technique considers for both groups an end-to-end nerve suture. In the experimental group (A) was used also a wrapping protocol by a conduit of collagen matrix currently used in oral surgery. The animals underwent functional grasping tests (at 1, 3, 5, and 7 months) and a histological and quantitative analysis of distal nerve was performed at the end of experimental time., Result: After seven months, the grasping test reveals functional recovery in each tested animal; this improvement is more evident in Group A. The fibers appear well organized with restored myelin sheaths in both groups. Group A showed a great quantity of connective tissue surrounding the nerve. The quantitative morphology analysis in both groups shows a similar fibers density, fiber diameter, and myelin thickness. The differences between the groups in axon mean diameter are significant. In Group A M/d, D/d, and g-ratio is significantly higher compared to control group., Conclusions: Histological and functional assessments show a functional recovery of the injured nerve in the test groups, stressed by the results of the grasping tests and the meaningful increasing in fiber diameter and higher g-ratio. Moreover, a connective tissue cuff distinguishes the distal portion of the injured nerve. Considering the easy availability and handling of the material used in this study we can conclude that this experimental technique can be considered as a valid alternative to protect nerves in nerve wrap surgery.

Background: In this study, we evaluate the role of RGMa (Repulsive Guidance Molecule a) during peripheral nerve regeneration using the mouse median nerve model., Methods: By real-time PCR and Western Blot analysis, we examined expression changes of RGMa mRNA and RGMa protein in neural tissue after transection and microsurgical repair of the mouse median nerve distal to the transection site. We evaluated histomorphometrical changes in neural tissue distal to the injury site and functional recovery of the grasping force after median nerve transection and repair in wild-type mice and RGMa+/- heterozygous mice., Results: RT-PCR revealed a 1,8 fold increase of RGMa mRNA two weeks and a 4,4 fold increase of RGMa mRNA 3 weeks after nerve transection and repair in the nerve segment distal to the injury site. In Western blot analysis, we could show a high increase of RGMa in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis showed significant differences between wild-type animals and heterozygous animals. The absolute number of myelinated fibres was significantly higher in operated heterozygous RGMa+/- animals compared to operated wildtye animals. Using the functional grasping test, we could demonstrate that peripheral nerve regeneration is significantly diminished in heterozygous RGMa+/- mice., Conclusions: Employing the mouse median nerve model in transgenic animals, we demonstrate that RGMa plays an important role during peripheral nerve regeneration.

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10-11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.

The use of autologous sural nerve grafts is still the current gold standard for the repair of peripheral nerve injuries with wide substance losses, but with a poor rate of functional recovery after repair of mixed and motor nerves, a limited donor nerve supply, and morbidity of donor site. At present, tubulization through the muscle vein combined graft, is a viable alternative to the nerve autografts and certainly is a matter of tissue engineering still open to continuous development, although this technique is currently limited to a critical gap of 3 cm with less favorable results for motor function recovery. In this report, we present a completely new tubulization method, the amnion muscle combined graft (AMCG) technique, that consists in the combination of the human amniotic membrane hollow conduit with autologous skeletal muscle fragments for repairing the substance loss of peripheral nerves and recover both sensory and motor functions. In a series of five patients with loss of substance of the median nerve ranging 3-5 cm at the wrist, excellent results graded as S4 in two cases, S3+ in two cases, and S3 in one case; M4 in four cases and M3 in one case were achieved. No iatrogenic damage due to withdrawal of a healthy nerve from donor site was observed. This technique allows to repair extensive loss of substance up to 5 cm with a good sensory and motor recovery. The AMCG thus may be considered a reasonable alternative to traditional nerve autograft in selected clinical conditions., (© 2014 Wiley Periodicals, Inc.)

Sciatic nerve crush injury in rat animal model is one of the most common experimental models used in regenerative research. However, the availability of transgenic mouse for nerve regeneration studies is constantly increasing and, therefore, the shift from rat model to mouse model is, in some cases, necessary. Moreover, since most of the human nerve lesions occur in the upper limb, it is also advantageous to shift from sciatic nerve to median nerve. In this study we described an experimental model which involves lesions of the median nerve in the mouse. Data showed that the finger flexor muscle contraction strength, assessed to evaluate the motor function recovery, and reached values not different from the control already 20 days after injury. The degree of nerve regeneration evaluated with stereological methods in light microscopy showed that, 25 days after injury, the number of regenerated myelinated fibers was comparable to the control, but they were smaller with a thinner myelin thickness. Stereological analysis made in electron microscopy confirmed these results, although the total number of fibers quantified was significantly higher compared to light microscopy analysis, due to the very small size of some fibers that can be detected only in electron microscopy.

The aim of this study was to evaluate the impact of pulsed magnetic field therapy on peripheral nerve regeneration after median nerve injury and primary coaptation in the rat. Both median nerves were surgically exposed and denervated in 24 female Wistar rats. A microsurgical coaptation was performed on the right side, whereas on the left side a spontaneous healing was prevented. The study group underwent a daily pulsed magnetic field therapy; the other group served as a control group. The grasping force was recorded 2 weeks after the surgical intervention for a period of 12 weeks. The right median nerve was excised and histologically examined. The histomorphometric data and the functional assessments were analyzed by t-test statistics and one-way ANOVA. One-way ANOVA indicated a statistically significant influence of group affiliation and grasping force (P = 0.0078). Grasping strength was higher on a significant level in the experimental group compared to the control group permanently from the 9th week to the end of the study. T-test statistics revealed a significantly higher weight of the flexor digitorum sublimis muscle (P = 0.0385) in the experimental group. The histological evaluation did not reveal any statistically significant differences concerning the histomorphometric parameters. Our results suggest that the pulsed magnetic field therapy has a positive influence on the functional aspects of neural regeneration. More studies are needed to precisely evaluate and optimize the intensity and duration of the application.

The babysitter-procedure might offer an alternative when nerve reconstruction is delayed in order to overcome muscular atrophy due to denervation. In this study we aimed to show that a sensomotoric babysitter-procedure after median nerve injury is capable of preserving irreversible muscular atrophy. The median nerve of 20 female Wistar rats was denervated. 10 animals received a sensory protection with the N. cutaneous brachii. After six weeks the median nerve was reconstructed by autologous nerve grafting from the contralateral median nerve in the babysitter and the control groups. Grasping tests measured functional recovery over 15 weeks. At the end of the observation period the weight of the flexor digitorum sublimis muscle was determined. The median nerve was excised for histological examinations. Muscle weight (P < 0.0001) was significantly superior in the babysitter group compared to the control group at the end of the study. The histological evaluation revealed a significantly higher diameter of axons (P = 0.0194), nerve fiber (P = 0.0409), and nerve surface (P = 0.0184) in the babysitter group. We conclude that sensory protection of a motor nerve is capable of preserving muscule weight and we may presume that metabolism of the sensory nerve was sufficient to keep the target muscle's weight and vitality.

Background: Less is known about the role of Netrin-1 in the peripheral nervous system. In this study, we evaluated the role of Netrin-1 using the mouse median nerve model for assessment of peripheral nerve regeneration., Methods: Using real-time PCR and western blot analysis, we examined expression changes of netrin-1 mRNA and Netrin-1 protein after transection and repair of the mouse median nerve in Wild-type animals. We further evaluated histomorphometrical changes as well as the functional recovery of the grasping force after median nerve transection and repair in WT mice and Netrin-1(+/-) heterozygous mice., Results: RT-PCR revealed a 1, 9 fold increase of Netrin-1 mRNA two weeks after nerve transection and repair in the nerve segment distal to the injury site. In Western blot analysis, we could show a high increase of Netrin-1 in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis showed significantly higher cross sectional area and a lower fibre density in heterozygous Netrin-1(+/-) mice. Using the functional grasping test, we could show that peripheral nerve regeneration is significantly diminished in heterozygous Netrin-1(+/-) mice., Conclusions: Employing the mouse median nerve model in transgenic animals, we demonstrate that Netrin-1 plays an important role during peripheral nerve regeneration.

In a transgenic mice (BALB-neuT) over-expressing ErbB2 receptor, we investigated the adult mouse median nerve in physiological and pathological conditions. Results showed that, in physiological conditions, the grip function controlled by the median nerve in BALB-neuT mice was similar to wild-type (BALB/c). Stereological assessment of ErbB2-overexpressing intact nerves revealed no difference in number and size of myelinated fibers compared to wild-type mice. By contrast, after a nerve crush injury, the motor recovery was significantly faster in BALB-neuT compared to BALB/c mice. Moreover, stereological assessment revealed a significant higher number of regenerated myelinated fibers with a thinner axon and fiber diameter and myelin thickness in BALB-neuT mice. At day-2 post-injury, the level of the mRNAs coding for all the ErbB receptors and for the transmembrane (type III) Neuregulin 1 (NRG1) isoforms significantly decreased in both BALB/c and BALB-neuT mice, as shown by quantitative real time PCR. On the other hand, the level of the mRNAs coding for soluble NRG1 isoforms (type I/II, alpha and beta) increased at the same post-traumatic time point though, intriguingly, this response was significantly higher in BALB-neuT mice with respect to BALB/c mice. Altogether, these results suggest that constitutive ErbB2 receptor over-expression does not influence the physiological development of peripheral nerves, while it improves nerve regeneration following traumatic injury, possibly through the up-regulation of soluble NRG1 isoforms.

Despite extensive research and surgical innovation, the treatment of peripheral nerve injuries remains a complex issue, particularly in nonsharp lesions. The aim of this study was to assess the clinical outcome in a group of 16 patients who underwent, in emergency, a primary repair for crush injury of sensory and mixed nerves of the upper limb with biological tubulization, namely, the muscle-vein-combined graft. The segments involved were sensory digital nerves in eight cases and mixed nerves in another eight cases (four median nerves and four ulnar nerves). The length of nerve defect ranged from 0.5 to 4 cm (mean 1.9 cm). Fifteen of 16 patients showed some degree of functional recovery. Six patients showed diminished light touch (3.61), six had protective sensation (4.31), and three showed loss of protective sensation (4.56) using Semmes-Weinstein monofilament test. All the patients who underwent digital nerve repair had favorable results graded as S4 in one case, S3+ in six cases, and S3 in one case. With respect to mixed nerve repair, we observed two S4, two S3+, two S3, one S2, and one S0 sensory recovery. Less favorable results were observed for motor function with three M4, one M3, two M2, and two M0 recoveries. Altogether, the results of this retrospective study demonstrates that tubulization nerve repair in emergency, in case of short nerve gaps, may restore the continuity of the nerve avoiding secondary nerve grafting. This technique preserves donor nerve and, in case of failure, does not preclude a delayed repair with a nerve graft., (Copyright © 2012 Wiley Periodicals, Inc.)

Whether post-traumatic regeneration can eventually result in rat peripheral nerve fibers regaining their pretrauma size is still an open question. While it has been shown that, after a sufficient duration in post-traumatic time, the number of regenerated rat peripheral nerve fibers can return to pretrauma numbers and the animal can regain normal prelesion function, no information regarding long-term changes in the size parameters of the regenerated nerve fibers is available. To fill this gap, we have investigated the post-traumatic changes in myelinated axon and nerve fiber diameter, myelin thickness, and g-ratio (the ratio of the inner axonal diameter to the fiber diameter) at three different time points following nerve injury: week-6, week-8, and week-24. A standardized nerve crush injury of the rat median nerve obtained using a nonserrated clamp was used for this study. The results showed that, consistent with previous studies, fiber number returned to normal values at week-24, but both axon and fiber diameter and myelin thickness were still significantly lower at week-24 than prelesion, and the g-ratio, which remained unchanged during the regeneration process, was significantly reduced at week-24 in comparison to the prelesion value. On the basis of these results, the hypothesis that regenerated rat peripheral nerve fibers are able to return spontaneously to their normal pretrauma state, provided there is a sufficiently long recovery time postaxonotmesis, is not supported., (Copyright © 2012 Wiley Periodicals, Inc.)

Background: Hemostatic procedures by means of electrical coagulation or application of topical agents are widely used to avoid postoperative bleeding during microsurgical reconstruction of peripheral nerves. It is speculated, however, that extensive hemostasis could provoke significant nerve damage., Objective: To examine the effects of 2 intraoperative hemostatic procedures on peripheral nerve regeneration., Methods: In 36 adult rats divided into 3 groups, the median nerve was transected and repaired by end-to-end neurorrhaphy. During surgery, bleeding was treated in groups 2 and 3 by application of either the topical hemostatic agent Floseal or routine bipolar coagulation. The degree of nerve regeneration was assessed in terms of motor function recovery using weekly grasping test evaluation for 3 months, muscle mass recovery of flexor digitorum sublimis, and stereological assessment of myelinated axon regeneration., Results: Neither of the 2 applied hemostatic methods induced any negative effects on nerve regeneration as defined by grip strength, muscle mass recovery, and morphology of myelinated nerve fibers. In contrast, Floseal-treated animals showed a faster progression of motor function recovery, and animals subjected to bipolar coagulation revealed a higher muscle mass recovery compared with the control group., Conclusion: Controlled application of bipolar coagulation or Floseal does not exert a negative effect on the nerve regeneration outcome in rats. We propose that these methods can be applied safely to patients.

Skeletal muscle atrophy represents one of the main causes of poor outcome of microsurgical nerve reconstruction. Recent studies have pointed to the importance of the neuregulin/ErbB signaling pathway in the development and regeneration of the neuromuscular system. Here, we show by immunohistochemistry, RT-PCR, and Western blotting analyses, in an in vivo model of adult skeletal muscle denervation/reinnervation, that expression of Neuregulin1 (NRG1) and ErbB receptors is regulated by the innervation condition. We found out that a significant upregulation of the alpha-, but not beta-, isoform of NRG1, as well as of ErbB2, ErbB3, and ErbB4-cyt1 isoform occurs as a consequence of denervation of flexor digitorum muscles of the rat forelimb by median nerve transection. Moreover, after tubulization median nerve repair, and consequent muscle reinnervation, all messengers of the NRG1/ErbB system are promptly downregulated. Therefore, our results suggest the existence of a alpha-NRG1-mediated autocrine and/or paracrine trophic loop in skeletal muscles that is activated after denervation and promptly deactivated after nerve reconstruction. This myotrophic loop is a promising therapeutic target for the prevention of muscle atrophy. Yet, the recent demonstration of a similar alpha-NRG1-mediated gliotrophic loop in denervated Schwann cells provides a possible explanation for the effectiveness of muscle conduits for tubulization nerve repair., (Copyright 2009 Wiley-Liss, Inc. Microsurgery 2009.)

Object: The authors of other studies have reported that the selection of an agonistic donor nerve is required for recovering voluntary motor control after end-to-side nerve repair. In this experimental investigation, the authors' goal was to verify this assumption by performing end-to-side neurorrhaphy of the rat median nerve on its antagonistic radial nerve., Methods: The left median nerve in 10 adult female rats was repaired by end-to-side neurorrhaphy after epineuriotomy on the radial nerve at the middle of the brachium. The time course of median nerve functional recovery was then assessed using the grasping test until postoperative Week 30. Before removing the nerve, the surgical site was carefully explored to exclude contamination by the proximal nerve stump, and the functional anatomy of median and radial nerves was assessed by electrical stimulation. Repaired nerves were then processed for resin embedding, and semithin sections were obtained for nerve fiber histomorphometry by using the dissector method., Results: Repaired median nerves were repopulated by nerve fibers regenerating from the radial donor nerve as previously shown. Moreover, voluntary motor control of the flexor muscles innervated by the median nerve was progressively recovered beginning in postoperative Week 10 and reaching 42% of normal by Week 30., Conclusions: Contrary to previously reported data, recovery of voluntary motor function after end-to-side nerve repair can also be expected when an antagonistic nerve is used as a donor nerve.

Our study used a rat animal model to verify that Schwann cell migration, collateral axonal sprouting, and regeneration were not hindered by interposition of a 10-mm vein segment between the distal stump of the transected ulnar nerve and the donor median nerve in end-to-side reconstruction. Reconstructed nerves were withdrawn at 7, 14, 30, and 60 days after surgery, then analyzed by confocal laser microscopy after immunolabeling with anti-neurofilament-200 kD (an axonal marker) and anti-S100 (a glial marker) antibodies. Results are reported at 7, 14, 30, and 60 days after surgery. Our observations indicate that chemotactic factors that stimulate end-to-side nerve regeneration can exert their action at this distance. These findings suggest a possible clinical application for this surgical technique in cases when the severed nerve stump is far from the potential donor nerve., ((c) 2007 Wiley-Liss, Inc.)

Y-shaped vein conduits enriched with fresh skeletal muscle fibers were used to bridge a concomitant ulnar and median nerve transection with substance loss in rats. The proximal limb of the Y-chamber was sutured to the proximal ulnar nerve, while the two distal limbs were sutured to ulnar and median distal nerve stumps. Eight months after surgery, median nerve functional recovery was evaluated by means of the grasping test, and nerve fiber regeneration in both repaired nerves was assessed by means of design-based histomorphometry. Results showed that nerve fibers regenerated along both severed nerve trunks, and in the median nerve led to a recovery corresponding to 58% of normal nerve function. Quantitative analysis showed no significant morphological differences between myelinated nerve fibers regenerated along the two distal nerves except for the number of fibers, which was higher in the median nerve. Notably, the total number of regenerated nerve fibers in the two distal nerves was 4-fold the normal fiber number in the ulnar nerve. Besides their interest in relation to the long-lasting debate about the topographic specificity of nerve regeneration, the results of this study show an effective way to repair, in the rat experimental model, two transected nerve trunks innervating agonistic muscles in the case that the proximal stump of only one nerve is preserved., ((c) 2004 Wiley-Liss, Inc.)

The quantitative assessment of motor function is an important requirement for studies on peripheral nerve injury and repair. So far, most studies on peripheral nerves have been performed on the sciatic nerve model using walking track analysis for assessing motor function. Alternatively, the employment of the median nerve model, which allows motor function evaluation by means of a simple behavioural test named grasping test (GT), have been more recently proposed. In this paper, the efficacy of the GT for the quantitative assessment of motor function recovery is re-appraised and a modified device for its carrying out is described. Finally, the rationale for the employment of the median nerve model as an alternative to the sciatic nerve model is critically discussed.

While it has been shown that terminolateral (end-to-side) neurorrhaphy leads to successful functional motor reinnervation of the peripheral territories belonging to the severed nerve, data on the morphology of terminolateral sprouting and on the voluntary control of the motor function restored by terminolateral neurorrhaphy are still partial. In this study, the severed rat median nerve was sutured in an end-to-side fashion to the intact ulnar nerve. The progression of recovery of the flexion of the fingers was assessed by means of the grasping test. Seven months after surgery, the rats were sacrificed, and morphologic and morphometric analysis was performed on the regenerated median nerve and on the donor ulnar nerve. Results of the functional assessment showed that voluntary motor control of the muscles innervated by the median nerve was partially and progressively recovered by terminolateral neurorrhaphy, with a mean strength in the flexion of the fingers that reached about 20 percent of normal before sacrifice. Morphologic and morphometric analysis showed that nerve-fiber regeneration occurred in all repaired median nerves. Signs of nerve fiber atrophy were detected in the ulnar nerve distal to the point of suture, suggesting the possible occurrence of secondary damage to the donor nerve after terminolateral neurorrhaphy that should be taken into consideration in a clinical perspective.

Nerve guidance conduits (NGCs) are used as an alternative to the "gold standard" nerve autografting, preventing the need for surgical intervention required to harvest autologous nerves. However, the regeneration outcomes achieved with the current NGCs are only comparable with autografting when the gap is short (less than 10 mm). In the present study, we have developed NGCs made from a blend of polyhydroxyalkanoates, a family of natural resorbable polymers. Hollow NGCs made from a 75:25 poly(3‐hydroxyoctanoate)/poly(3‐hydroxybutyrate) blend (PHA‐NGCs) were manufactured using dip‐molding. These PHA‐NGCs showed appropriate flexibility for peripheral nerve regeneration. In vitro cell studies performed using RT4‐D6P2T rat Schwann cell line confirmed that the material is capable of sustaining cell proliferation and adhesion. PHA‐NGCs were then implanted in vivo to repair 10 mm gaps of the median nerve of female Wistar rats for 12 weeks. Functional evaluation of the regenerated nerve using the grasping test showed that PHA‐NGCs displayed similar motor recovery as the autograft, starting from week 7. Additionally, nerve cross‐sectional area, density and number of myelinated cells, as well as axon diameter, fiber diameter, myelin thickness and g‐ratio obtained using the PHA‐NGCs were found comparable to an autograft. This preclinical data confirmed that the PHA‐NGCs are indeed highly promising candidates for peripheral nerve regeneration. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate: (i) the neuro‐regenerative potential of chitosan membrane (CS‐Me) on acutely axotomised autonomic neurones in vitro; (ii) to exclude the possibility that a pro‐regenerative biomaterial could interfere with the proliferation activity of prostate cancer cell lines; (iii) to provide an in vivo proof of the biocompatibility and regeneration promoting effect of CS‐Me in a standardised rat model of peripheral nerve injury and repair; (iv) finally, to evaluate the tissue reaction induced by the degrading material; as previous studies have shown promising effects of CS‐Me for protection of the neurovascular bundles for potency recovery in patients that undergo nerve‐sparing radical prostatectomy (RP). Materials and Methods: Addressing aim (i), the neuro‐regenerative potential, organotypic cultures derived from primary sympathetic ganglia were cultured on CS‐Me over 3 days and neurite extension and axonal sprouting were evaluated. Addressing aim (ii), effects of CS on cancer cells, different human prostate cancer cell lines (PC3, DU‐145, LN‐Cap) were seeded on CS‐coated plates or cultured in the presence of CS‐Me dissolution products. Addressing aims (iii) and (iv), functional recovery of peripheral nerve fibres and tissue reaction with the biomaterial, CS‐Me and CS nerve guides were used to repair a median nerve injury in the rat. Functional recovery was evaluated during the post‐recovery time by the behavioural grasping test. Results: CS‐Me significantly stimulated axon elongation from autonomic ganglia in comparison to control conditions in organotypic three‐dimensional cultures. CS coating, as well as the dissolution products of CS‐Me, led to a significantly lower proliferation rate of prostate cancer cell lines in vitro. Tissue reaction towards CS‐Me and standard CS nerve guides was similar in the rat median nerve model, as was the outcome of nerve fibre regeneration and functional recovery. Conclusion: The results of this study provide the first experimental evidence in support of the clinical safety of CS‐Me and of their postulated effectiveness for improving functional recovery after RP. The presented results are coherent in demonstrating that acutely axotomised autonomic neurones show increased neurite outgrowth on CS‐Me substrate, whilst the same substrate reduces prostate cancer cell line proliferation in vitro. Furthermore, CS‐Me do not demonstrate any disadvantage for peripheral nerve repair in a standard animal model. [ABSTRACT FROM AUTHOR]

The successful introduction of innovative treatment strategies into clinical practise strongly depends on the availability of effective experimental models and their reliable pre-clinical assessment. Considering pre-clinical research for peripheral nerve repair and reconstruction, the far most used nerve regeneration model in the last decades is the sciatic nerve injury and repair model. More recently, the use of the median nerve injury and repair model has gained increasing attention due to some significant advantages it provides compared to sciatic nerve injury. Outstanding advantages are the availability of reliable behavioural tests for assessing posttraumatic voluntary motor recovery and a much lower impact on the animal wellbeing. In this article, the potential application of the median nerve injury and repair model in pre-clinical research is reviewed. In addition, we provide a synthetic overview of a variety of methods that can be applied in this model for nerve regeneration assessment. This article is aimed at helping researchers in adequately adopting this in vivo model for pre-clinical evaluation of peripheral nerve reconstruction as well as for interpreting the results in a translational perspective. [ABSTRACT FROM AUTHOR]

Summary: In spite of great recent advancements, the definition of the optimal strategy for bridging a nerve defect, especially across long gaps, still remains an open issue since the amount of autologous nerve graft material is limited while the outcome after alternative tubulization techniques is often unsatisfactory. The aim of this study was to investigate a new tubulization technique based on the employment of vein conduits filled with whole subcutaneous adipose tissue obtained by lipoaspiration. In adult rats, a 1cm-long defect of the left median nerve was repaired by adipose tissue–vein-combined conduits and compared with fresh skeletal muscle tissue-vein-combined conduits and autologous nerve grafts made by the excised nerve segment rotated by 180°. Throughout the postoperative period, functional recovery was assessed using the grasping test. Regenerated nerve samples were withdrawn at postoperative month-6 and processed for light and electron microscopy and stereology of regenerated nerve fibers. Results showed that functional recovery was significantly slower in the adipose tissue-enriched group in comparison to both control groups. Light and electron microscopy showed that a large amount of adipose tissue was still present inside the vein conduits at postoperative month-6. Stereology showed that all quantitative morphological predictors analyzed performed significantly worse in the adipose tissue-enriched group in comparison to the two control groups. On the basis of this experimental study in the rat, the use of whole adipose tissue for tissue engineering of peripheral nerves should be discouraged. Pre-treatment of adipose tissue aimed at isolating stromal vascular fraction and/or adipose derived stem/precursor cells should be considered a fundamental requisite for nerve repair. [Copyright &y& Elsevier]

Purpose: The improvement of regeneration and functional recovery after peripheral nerve injury is a major challenge in neurosurgery. Although microsurgical techniques for nerve reconstruction have seen great advancements over the last years, the clinical outcome with patients is often unsatisfactory. The aim of the present study was to investigate if administration of the iron chelator Deferroxamine (DFO), can improve postoperative outcome in the rat median nerve reconstruction model. Methods: After complete transection, the right median nerve was repaired by end-to-end neurorrhaphy. The suture site was wrapped by a 1-cm-long external jugular vein segment, either empty or filled with DFO-loaded lipid particles (Perineurin© or with a vehicle (unloaded lipid particles) alone. Functional testing was carried out weekly by means of the grasping test. At the time of withdrawal, 12 weeks post-operatively, muscle tropism recovery was assessed by weighing flexor digitorum sublimis muscle that is innervated by the median nerve only. Before harvesting of the nerve specimens electrophysiological analyses were performed with measuring the latency, the threshold and the conduction velocity. Finally, the repaired nerves were withdrawn for immunocytochemistry with a neurofilament antibody and axon quantitative morphology. Results: The comparison between the groups showed that intraoperative application of the DFO-loaded lipid particles at the neurorrhaphy site led to a significant increase in the density of regenerating axons as well as to an accelerated recovery of both muscle tropism and motor function. The electrophysiological results demonstrated a decrease of the threshold, a lower latency, and a higher conduction velocity in the Perineurin©-treated animals. Conclusions: The results of the present study suggest that local administration of Perineurin© might have a therapeutic potential for improving the postoperative outcome after microsurgical nerve reconstruction in patients. [ABSTRACT FROM AUTHOR]