Nerve repair: experimental and clinical evaluation of neurotrophic factors in peripheral nerve regeneration

Analysis of Clinical Characteristics and Neuropeptides in Patients with Dry Eye with and without Chronic Ocular Pain after FS-LASIK

INTRODUCTION

Chronic ocular pain, particularly prevalent in patients with dry eye disease and post-femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) surgery, presents with unclear clinical characteristics and an undefined pathogenesis. In this study, we aimed to compare clinical characteristics and tear neuropeptide concentrations in patients with dry eye disease (DED) with and without chronic ocular pain following FS-LASIK, and investigate correlations between ocular pain, clinical characteristics, and tear neuropeptide levels.

METHODS

Thirty-eight post-FS-LASIK patients with DED were assigned to two groups: those with chronic ocular pain and those without chronic ocular pain. Dry eye, ocular pain, and mental health-related parameters were evaluated using specific questionnaires and tests. The morphology of corneal nerves and dendritic cells (DCs) was evaluated by in vivo confocal microscopy. Function of corneal innervation was evaluated by corneal sensitivity. Concentrations of tear cytokines (interleukin [IL]-6, IL-23, IL-17A, and interferon-γ) and neuropeptides (α-melanocyte-stimulating hormone, neurotensin, β-endorphin, oxytocin, and substance P [SP]) were measured using the Luminex assay.

RESULTS

Most patients with chronic ocular pain experienced mild to moderate pain; the most common types included stimulated pain (provoked by wind and light), burning pain, and pressure sensation. More severe dry eye (P < 0.001), anxiety symptoms (P = 0.026), lower Schirmer I test values (P = 0.035), lower corneal nerve density (P = 0.043), and more activated DCs (P = 0.041) were observed in patients with ocular pain. Tear concentrations of SP and oxytocin were significantly higher in patients with ocular pain (P = 0.001, P = 0.021, respectively). Furthermore, significant correlations were observed among ocular pain severity, SP, and anxiety levels.

CONCLUSIONS

Patients with DED after FS-LASIK who have chronic ocular pain show more severe ocular and psychological discomfort and higher tear levels of neuropeptides. Furthermore, ocular pain severity is correlated with tear SP levels.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05600985.

The Construction of Three-Layered Biomimetic Arterial Graft Balances Biomechanics and Biocompatibility for Dynamic Biological Reconstruction

The process of reconstructing an arterial graft is a complex and dynamic process that is subject to the influence of various mechanical factors, including tissue regeneration and blood pressure. The attainment of favorable remodeling outcomes is contingent upon the biocompatibility and biomechanical properties of the arterial graft. A promising strategy involves the emulation of the three-layer structure of the native artery, wherein the inner layer is composed of polycaprolactone (PCL) fibers aligned with blood flow, exhibiting excellent biocompatibility that fosters endothelial cell growth and effectively prevents platelet adhesion. The middle layer, consisting of PCL and polyurethane (PU), offers mechanical support and stability by forming a contractile smooth muscle ring and antiexpansion PU network. The outer layer, composed of PCL fibers with an irregular arrangement, promotes the growth of nerves and pericytes for long-term vascular function. Prioritizing the reconstruction of the inner and outer layers establishes a stable environment for intermediate smooth muscle growth. Our three-layer arterial graft is designed to provide the blood vessel with mechanical support and stability through nondegradable PU, while the incorporation of degradable PCL generates potential spaces for tissue ingrowth, thereby transforming our graft into a living implant.

Effect of Ultrasound Therapy on Expression of Vascular Endothelial Growth Factor, Vascular Endothelial Growth Factor Receptors, CD31 and Functional Recovery After Facial Nerve Injury

Functional recovery is provided by some neurotrophic factors released from the near vicinity of the injury site. Ultrasound treatment is known to increase neurotrophic factor expression. This study was aimed at determining the effect of ultrasound treatment on the expression of vascular endothelial growth factor (VEGF), its receptors and new vessel formation after facial nerve injury. Sixty-four Wistar rats were divided into four groups: control (group 1), sham (group 2), facial-facial coaptation (group 3), and facial-facial coaptation and ultrasound treatment (group 4). Animals in each group were evaluated on the 14th and 28th days. Immunohistochemical staining and electrophysiological and gene-level evaluations were performed for the expression of VEGF and its receptors. When the results were evaluated, it was determined that VEGF, VEGFR1 (VEGF receptor 1), VEGFR2 (VEGF receptor 2) and CD31 levels were significantly higher in groups 3 and 4 compared with the control and sham groups. The increase in these values was more prominent after 28 d of ultrasound treatment than all groups. Electrophysiological results revealed similar evident functional improvement in group 4 with decreased latency and increased amplitudes compared with group 3. Our findings suggest that ultrasound treatment might promote injured facial nerve regeneration by stimulating release of VEGF and its receptors and may result in functional improvement.

The efficacy of new neuronal growth factor in the healing of the sciatic nerves in rabbits

Background and Objective

Regeneration of nervous tissue is unpredictable and an ideal growth factor to influence the healing of the injured nerves is not available. A recent study in rats had shown that a new neuronal growth factor (NNGF) was effective in the early healing of the sciatic nerves. The aim of this experimental study is to test the efficacy of NNGF in the healing of iatrogenic division of the sciatic nerves in a larger animal (rabbits).

Methods

White New Zealand 20 male rabbits of 6 months of age were divided into two groups. Intramuscular ketamine and xylazine were used to anesthetize the animals. The sciatic nerves were divided using scalpel blade 15 and 10/0 Vicryl was used to repair the divided neural tissue. In the study group, 10 mg/kg body weight of NNGF was instilled on the top of the divided nerves and the wound was closed. At 4 weeks, the operated limbs were observed for any trophic skin changes. Nerve conduction studies were carried out using train-of-four-Watch SX, Organon (Ireland) Ltd., and Ireland. The rabbits were put to death humanely and the sciatic nerves were removed and delivered to the pathologist in 2% formalin. The pathologists were blinded about the two groups.

Results

Electromyographic study done at 4 weeks showed in the untreated group; the mean twitches 1-T4 was 0.45 ± 0.31% and in the treated group, the average was 77.912 ± 5% (P > 0.001). Microscopic anatomy in the treated group revealed prominent healing by regeneration was evidenced by showing growth of its proximal segments into an empty endoneurial tube which was not seen in the control group. In the control group, the nerves showed no histological element of healing by regeneration.

Conclusions

NNGF proves that in a larger animal at 4 weeks profoundly influenced early regeneration of experimentally created divisions of myelinated nerve tissue.

Protease Activated Receptor 1 and Its Ligands as Main Regulators of the Regeneration of Peripheral Nerves

In contrast with the brain and spinal cord, peripheral nerves possess a striking ability to regenerate after damage. This characteristic of the peripheral nervous system is mainly due to a specific population of glial cells, the Schwann cells. Schwann cells promptly activate after nerve injury, dedifferentiate assuming a repair phenotype, and assist axon regrowth. In general, tissue injury determines the release of a variety of proteases which, in parallel with the degradation of their specific targets, also activate plasma membrane receptors known as protease-activated receptors (PARs). PAR1, the prototypical member of the PAR family, is also known as thrombin receptor and is present at the Schwann cell plasma membrane. This receptor is emerging as a possible regulator of the pro-regenerative capacity of Schwann cells. Here, we summarize the most recent literature data describing the possible contribution of PAR1 and PAR1-activating proteases in regulating the regeneration of peripheral nerves.

Bone Marrow Mesenchymal Stem Cell Condition Medium Loaded on PCL Nanofibrous Scaffold Promoted Nerve Regeneration After Sciatic Nerve Transection in Male Rats

Nowadays, researchers pay a vast deal of attention to neural tissue regeneration due to its tremendous effect on the patient's life. There are many strategies, from using conventional autologous nerve grafts to the newly developed methods for reconstructing damaged nerves. Among the various therapeutic methods, incorporating highly potent biomolecules and growth factors, the damaged nerve site would promote nerve regeneration. The aim was to examine the efficiency of a mesenchymal stem cell condition medium (MSC-CM) loaded on a 3D-polycaprolactone (PCL) scaffold as a nerve conduit in an axotomy rat model. Twenty-four mature male rats were classified into four groups: controls (the animals of this group were intact), axotomy (10 mm piece of the nerve was removed), axotomy (10-mm piece of the nerve was removed) + scaffold, and axotomy (10-mm piece of the nerve was removed) + MSC-CM-loaded scaffold. We followed up nerve motor function using a sciatic function index and electromyography activity of the gastrocnemius muscle. At 12 weeks post axotomy, sciatic nerve and dorsal root ganglion specimens and L4 and L5 spinal cord segments were separated from the rats and were analyzed by stereological, immunohistochemistry, and RT-PCR procedures. The rats of the axotomy group presented the expected gross locomotor deficit. Stereological parameters, immunohistochemistry of GFAP, and gene expression of S100, NGF, and BDNF were significantly enhanced in the CM-loaded scaffold group compared with the axotomy group. The most observed similarity was noted between the results of the control group and the CM-loaded scaffold group. Our results support the potential applicability of MSC-CM-loaded PCL nanofibrous scaffold to treat peripheral nerve injury (PNI).

Stem cells in end-to-side neurorrhaphy. Experimental study in rats

Purpose:

To evaluate the influence of mesenchymal stem cells from adipose tissue in the end-to-side neurorrhaphy, focusing in the nerve regeneration and the muscle reinnervation in acute trauma.

Methods:

140 animals were randomly divided in seven groups: control, denervated, end-to-side neurorrhaphy between distal stump of common peroneal nerve and tibial nerve (ESN), ESN wrapped in fascia, ESN wrapped in fascia and platelet gel, ESN wrapped in platelet gel, ESN wrapped in fascia and platelet gel within stem cells (without culture) removed from the adipose tissue. Mass measurements of the animal and of cranial tibial muscles, electromyography, walking track analysis tests and histological examinations of the nerves and muscles after 180 days was performed.

Results:

In the groups where the ESN was performed, the results were always better when compared to the denervated group, showing reinnervation in all ESN groups. The most sensitive methods were walking track and histological analysis. Only the group with stem cells showed values similar to the control group, as well as the functional indices of peroneal nerve and the number of nerve fibers in the peroneal nerve.

Conclusions:

Stem cells were effective in ESN according with the functional index of the peroneal nerve, evaluated by walking track analysis and the number of nerve fibers in the peroneal nerve.

Immunoexpression of BDNF, TrkB, and p75NTR receptors in peripheral neural lesions of the head and neck

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and neurotrophin receptors have been recognized as fundamental regulators of normal brain development, homeostasis, and plasticity. They have also been studied in the behavior of central nervous system tumors. Here, we studied the pattern of BDNF, TrkB and p75NTR immunoexpression in peripheral benign and malignant neural lesions in head and neck.

METHODS

This cross-sectional analytical study included 79 cases of head and neck neural lesions. Nineteen cases of traumatic neuromas (TN), 20 cases of granular cell tumors (GCT), 16 cases of neurofibromas (NF), 20 cases of schwannomas (SC), and 4 malignant peripheral nerve sheath tumor (MPNST) were submitted to immunohistochemistry with BDNF, TrkB, and p75NTR antibodies. A semi-quantitative analysis was performed.

RESULTS

The analysis of BDNF demonstrated a high percentage of positive cells in TN, GCT and SC with a decrease in cases of NF and MPNST. TrkB presented a lower significant immunoexpression in GCT in relation to the TN, NF, SC, and MPNST (P < .0001); and TN showed less percentage of positive cell compared to SC (P = .0017). Regarding p75NTR, the percentage of positive cell was significantly reduced in MPNST compared GCT (P = .009), NF (P = .0138) and SC (P = .0069). Also, a decrease in TN compared to GCT (P = .007) was observed.

CONCLUSIONS

Our results showed the immunoreactivity of BDNF, TrkB, and p75NTR in head and neck peripheral neural lesions. Reduction of BDNF and p75NTR in MPNST might suggest down-regulation during the acquisition of malignant phenotype.

Overview of the short- and long-term quantitative outcomes following end-to-side neurorrhaphy in a rat model

The time course of events following end-to-side nerve coaptation remains unclear. Re-innervation and effects on the donor nerve were assessed following short- and long-term end-to-side neurorrhaphy were investigated in a rat model. One hundred and our Sprague-Dawley female rats were randomized to fresh and pre degenerated repair groups with or without perineurotomy. The right peroneal nerve was sutured to the tibial nerve in an end-to-side manner. Histological and electro-physiological assessment of re-innervation and of the donor nerve was performed at two-three months and at nine-twelve months, post-operatively. The results demonstrated that end-to-side neurorrhaphy could attract axonal sprouts and successfully re-innervate the target muscles. The influence on donor nerve was minimal in late stages, although it did have early negative effect. Double labeling provided evidence that one of the mechanisms of this procedure is probably by collateral sprouting.

Silicone tubes with thyroid hormone (Τ3) and BDNF as an alternative to autografts for bridging neural defects

The way thyroid hormone works in peripheral nerve regeneration has not been fully elucidated, although studies have shown that it has a strong positive effect on nerve regeneration. It is argued that its action is probably stronger than the neurotrophic factors that have been used for some time. It is hypothesized that the use of thyroid hormone in the nerve tubes has a beneficial effect on nerve regeneration to the extent that the results of its use are comparable to those of the autograft technique in bridging small nerve deficits. In this experimental study, we examined the effect of thyroid hormone and BDNF (Brain Derived Neurotrophic Factor) on the repair of 10 mm nerve defects when administered within silicone nerve tubes and compared the results with the autograft method. Thyroid hormone promotes nerve regeneration mainly by increasing its speed and its effect on the maturation of nerve fibers compared to the other groups where the nerve deficit was bridged by entubulation. Also, better organization and the absence of intraneural fibrosis, compared to the other groups, may argue for the action of thyroid hormone in regulating the inflammatory response. Functionally, the AG group showed better results compared to the other groups by the end of the study (16 weeks).

Tissue Plasminogen Activator Loaded PCL Nanofibrous Scaffold Promoted Nerve Regeneration After Sciatic Nerve Transection in Male Rats

According to the studies, damages to the peripheral nerve as a result of a trauma or acute compression, stretching, or burns accounts for a vast range of discomforts which strongly impressed the patient's life quality. Applying highly potent biomolecules and growth factors in the damaged nerve site would promote the probability of nerve regeneration and functional recovery. Tissue plasminogen activator (tPA) is one of the components that can contribute importantly to degenerating and regenerating the peripheral nerves following the injuries occurred and the absence of this biomolecule hinders the recoveries of the nerves. This technique would guarantee the direct accessibility of tPA for the regenerating axons. Structural, physical, and in vitro cytotoxicity evaluations were done before in vivo experiments. In this study, twenty-four mature male rats have been exploited. The rats have been classified into four groups: controls, axotomy, axotomy + scaffold, and axotomy + tPA-loaded scaffold. Four, 8, and 12 weeks post-surgical, the sciatic functional index (SFI) has been measured. After 12 weeks, the spinal cord, sciatic nerve, and dorsal root ganglion specimens have been removed and stereological procedures, immunohistochemistry, and gene expression have been used to analyze them. Stereological parameters, immunohistochemistry of GFAP, and gene expression of S100, NGF, and BDNF were significantly enhanced in tPA-loaded scaffold group compared with axotomy group. The most similarity was observed between the results of control group and tPA-loaded scaffold group. According to the results, a good regeneration of the functional nerve tissues in a short time was observed as a result of introducing tPA.

The investigation of therapeutic potential of oxytocin and liraglutide on vincristine-induced neuropathy in rats

The aim of this study was to assess the therapeutic potential of oxytocin and liraglutide (LIR), a GLP-1 analogue, in a rat model of vincristine-induced neuropathy. Rats were injected with vincristine (VCR) at a dose of 4 mg/kg twice a week for 5 weeks. The VCR-administered rats were divided into three groups and received saline, oxytocin, or liraglutide simultaneously with VCR. After the treatment period, electrophysiological, biochemical, histological, and immunohistochemical investigations were performed. Electromyography (EMG) recordings demonstrated significant alterations in the VCR + saline group (p < .001). Also, motor performance was decreased in the VCR + saline group (p < .05). Histologically, the axonal diameter was decreased in all groups. VCR + saline group showed significantly increased lipid peroxidation and decreased nerve growth factor (NGF) expression. However, the administration of oxytocin and liraglutide significantly prevented the EMG alterations, lipid peroxidation, and reduction in neuronal NGF expression. On the basis of these findings, oxytocin and liraglutide may be considered as potential agents for the prevention of VCR-induced neuropathy.

A new approach of ocular nebulization with vitamin B12 versus oxytocin for the treatment of dry eye disease: an in vivo confocal microscopy study

Purpose: To present a new ocular nebulization therapy for the treatment of dry eye disease (DED) and investigate the efficacy of vitamin B12 (VB12) and oxytocin (OXT) nebulization with clinical parameters and in vivo confocal microscopy (IVCM). Patients and methods: Thirty-eight patients with DED were enrolled, with 19 receiving VB12 nebulization and 19 receiving OXT nebulization twice weekly for 3 months. Clinical signs and symptoms including Ocular Surface Disease Index, self-assessment of light sensitivity and dryness, tear meniscus height, tear break-up time (BUT), and corneal staining, along with IVCM data of basal epithelial cell density, sub-basal dendritic cell (DC) density, nerve density, and nerve tortuosity were acquired at baseline, 1 month, and 3 months after starting treatment. Results: Patients treated with VB12 improved significantly in all signs and symptoms except for nerve tortuosity during the three-month treatment, while OXT demonstrated similar effects apart from BUT and nerve tortuosity. VB12 group revealed a higher BUT at 1 month and 3 months with a higher basal epithelial cell density at 3 months compared with OXT group, and a lower DC density was observed in OXT group at 1 month. Change of basal epithelial cell density was more significant at 3 months in VB12 group, with OXT group showing a significantly higher DC reduction at 1 month. Conclusion: The nebulization therapy delivering VB12 and OXT appears to be effective in improving the symptoms and signs of dry eye, with a relatively stronger effect of BUT elevation and epithelial repair in VB12 and anti-inflammation in OXT nebulization.

[Significance of the composition of conduit internal environment for the activation of axon growth in patients with extended peripheral nerve defects]

The recovery of peripheral nerves after injury is an urgent medical problem. Despite the advances in microsurgery techniques, it is still not possible to achieve complete holistic and functional recovery. It is more difficult to repair neural tissue after injury if there is a diastasis between the injured ends nerves. In this case, neurorraphy can not be carried out due to the eruption of the filaments in tension and convergence of proximal and distal ends of the axon. Modern tactics of restoration of extended defects of nerves involves the use of conduits - cylindrical conductors, overlapping posttraumatic diastasis, in order to create a vector of regeneration from the proximal part of the nerve to the distal. An ideal conduit should contain an internal environment that stimulates the recovery processes of nerve fibers. At present, there is no unified approach involving the use of a certain natural or artificial conduit environment. The review analyzes the regenerative potential of the internal environments of conduits as the most promising in modern biotechnologies for the reconstruction of extended peripheral nerve defects.

The multiple functions of melatonin in regenerative medicine

Melatonin research has been experiencing hyper growth in the last two decades; this relates to its numerous physiological functions including anti-inflammation, oncostasis, circadian and endocrine rhythm regulation, and its potent antioxidant activity. Recently, a large number of studies have focused on the role of melatonin in the regeneration of cells or tissues after their partial loss. In this review, we discuss the recent findings on the molecular involvement of melatonin in the regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others.

Molecular Mechanism of the "Babysitter" Procedure for Nerve Regeneration and Muscle Preservation in Peripheral Nerve Repair in a Rat Model

OBJECTIVE

To investigate the molecular mechanism of nerve "babysitter" for nerve regeneration and muscle preservation in peripheral nerve repair.

METHODS

Eighty rats were equalized into 4 groups: peroneal nerve transected, group A received no treatment; group B underwent end-to-end repair; group C underwent end-to-side "babysitter" with donor epineurial window; group D underwent end-to-side "babysitter" with 40% donor neurectomy. During second-stage procedure, end-to-end neurorrhaphies were executed in groups A, C, and D. Expression of Insulin-like growth factor (IGF)-1 in spinal cord and IGF-1, TNF-like weak inducer of apoptosis (TWEAK), and Fn14 in anterior tibial muscles were evaluated by histopathology at 4-, 8-, 12-, and 24-week timepoints postoperatively.

RESULTS

At 4 weeks, group D expressed comparable IGF-1 with group B, and greater value than groups A and C in spinal cord. By 24 weeks, groups B and D showed higher values than groups A and C. Insulin-like growth factor 1 in muscles were greater in groups C and D than in groups A and B at 4 weeks, and comparable in all groups at 24 weeks. At 4 weeks, immunoreactive scores of TWEAK were 9.00 ± 0, 3.00 ± 0, 6.75 ± 0.75, and 6.75 ± 0.75, respectively. No differences were noticed in all groups by 24 weeks. At 4 weeks, Fn14 were similar in groups A, C, and D, but lower in group B. Group D showed comparable Fn14 with groups B and C, but lower value than group A at 24 weeks.

CONCLUSIONS

End-to-side nerve "babysitter" in peripheral nerve could promote fiber regeneration and muscle preservation by regulating expression of IGF-1 and TWEAK-Fn14. End-to-side "babysitter" with partial donor neurectomy could achieve comparable effects with end-to-end repair.

The use of lumbar epidural injection of platelet lysate for treatment of radicular pain

Background

Epidural steroid injections (ESI) are the most common pain management procedure performed in the US, however evidence of efficacy is limited. In addition, there is early evidence that the high dose of corticosteroids used can have systemic side effects. We describe the results of a case series evaluating the use of platelet lysate (PL) epidural injections for the treatment of lumbar radicular pain as an alternative to corticosteroids.

Methods

Registry data was obtained for patients (N = 470) treated with PL epidural injections presenting with symptoms of lumbar radicular pain and MRI findings that were consistent with symptoms. Collected outcomes included numeric pain score (NPS), functional rating index (FRI), and a modified single assessment numeric evaluation (SANE) rating.

Results

Patients treated with PL epidurals reported significantly lower (p < .0001) NPS and FRI change scores at all time points compared to baseline. Post-treatment FRI change score means exceeded the minimal clinically important difference beyond 1 month. Average modified SANE ratings showed 49.7% improvement at 24 months post-treatment. Twenty-nine (6.3%) patients reported mild adverse events related to treatment.

Conclusion

Patients treated with PL epidurals reported significant improvements in pain, exceeded the minimal clinically important difference (MCID) for FRI, and reported subjective improvement through 2-year follow-up. PL may be a promising substitute for corticosteroid.

Approaches to Peripheral Nerve Repair: Generations of Biomaterial Conduits Yielding to Replacing Autologous Nerve Grafts in Craniomaxillofacial Surgery

Peripheral nerve injury is a common clinical entity, which may arise due to traumatic, tumorous, or even iatrogenic injury in craniomaxillofacial surgery. Despite advances in biomaterials and techniques over the past several decades, reconstruction of nerve gaps remains a challenge. Autografts are the gold standard for nerve reconstruction. Using autografts, there is donor site morbidity, subsequent sensory deficit, and potential for neuroma development and infection. Moreover, the need for a second surgical site and limited availability of donor nerves remain a challenge. Thus, increasing efforts have been directed to develop artificial nerve guidance conduits (ANCs) as new methods to replace autografts in the future. Various synthetic conduit materials have been tested in vitro and in vivo, and several first- and second-generation conduits are FDA approved and available for purchase, while third-generation conduits still remain in experimental stages. This paper reviews the current treatment options, summarizes the published literature, and assesses future prospects for the repair of peripheral nerve injury in craniomaxillofacial surgery with a particular focus on facial nerve regeneration.

Cartilage oligomeric matrix protein enhances the vascularization of acellular nerves

Vascularization of acellular nerves has been shown to contribute to nerve bridging. In this study, we used a 10-mm sciatic nerve defect model in rats to determine whether cartilage oligomeric matrix protein enhances the vascularization of injured acellular nerves. The rat nerve defects were treated with acellular nerve grafting (control group) alone or acellular nerve grafting combined with intraperitoneal injection of cartilage oligomeric matrix protein (experimental group). As shown through two-dimensional imaging, the vessels began to invade into the acellular nerve graft from both anastomotic ends at day 7 post-operation, and gradually covered the entire graft at day 21. The vascular density, vascular area, and the velocity of revascularization in the experimental group were all higher than those in the control group. These results indicate that cartilage oligomeric matrix protein enhances the vascularization of acellular nerves.

Effect of Frankincense Extract on Nerve Recovery in the Rat Sciatic Nerve Damage Model

This study investigated the effect of frankincense extract on peripheral nerve regeneration in a crush injury rat model. Forty-eight Sprague-Dawley rats were randomly divided into four groups: control and frankincense extract low-, medium-, and high-dose groups. At days 7, 14, 21, and 28 following the surgery, nerve regeneration and functional recovery were evaluated using the sciatic functional index (SFI), expression of GAP-43, and the proliferation of Schwann cells (SCs) in vivo and in vitro. At day 7, the SFI in the frankincense extract high-dose group was significantly improved compared with the control group. After day 14, SFI was significantly improved in the medium- and high-dose groups. There was no significant difference in GAP-43 expression among the groups at day 7. However, after day 14, expression of GAP-43 in the high-dose group was higher than that in the control group. Histological evaluation showed that the injured nerve of frankincense extract high-dose group recovered better than the other groups 28 days after surgery. Further, S100 immunohistochemical staining, MTT colorimetry, and flow cytometry assays all showed that frankincense extract could promote the proliferation of SCs. In conclusion, frankincense extract is able to promote sciatic nerve regeneration and improve the function of a crushed sciatic nerve. This study provides a new direction for the repair of peripheral nerve injury.

Effect of new neuronal growth factor on healing of sciatic nerve in rats

OBJECTIVE

The study aimed to investigate the effect of a new peptide new nerve growth factor (NNGF) on the healing of divided sciatic nerves in rats.

MATERIAL AND METHODS

Twenty Sprague-Dawley rats of 250-300g were divided into two groups (group 1 - study group and group 2 - control group). Under ketamine intramuscular anesthesia sciatic nerves were exposed, divided and repaired using 10/0 dexon. Study animals had 10mg/kg body weight of NNGF added to the repair. Electromyographic studies of the hind libs were carried out after 8weeks. The average stimulation was 50mA for 200μS and four twitches (T) were recorded. The animals were euthanized and the sciatic nerves were removed for histological analysis.

RESULTS

There were no deaths in either of the groups. Electromyographic study showed that in the control group the average T1-T4 was 0.587±0.17% and in the study group the average was 87.89±5.02% (p value of 0.001). Histologically the control group showed regenerated axons sprouting from the proximal segment of cut nerve with empty endoneurial channels, while in the study group whole nerve trunks were seen within endoneurial channels.

CONCLUSION

This study shows that the NNGF has a positive influence on the experimental healing of sciatic nerves in animals.

Effect of oxytocin administration on nerve recovery in the rat sciatic nerve damage model

Background

Growth factors such as nerve growth factor (NGF) and insulin-like growth factor-1 (IGF-1) have been shown to play a role in the healing process of nerve injury. Recent researches have also shown that oxytocin administration activates these growth factors of importance for the healing of nerve tissue. The objective of the present study was to evaluate the effects of oxytocin on peripheral nerve regeneration in rats.

Methods

Twenty-four male Sprague-Dawley rats were underwent transection damage model on the right sciatic nerve and defective damage model on the left sciatic nerve. The animals were assigned to one of two groups: control group or treatment group (received 80 mg/kg oxytocin intraperitoneally for 12 weeks). The sciatic nerve was examined, both functionally (on the basis of climbing platform test) and histologically (on the basis of axon count), 3, 6, 9, and 12 weeks after the injury. Also, stereomicroscopic and electrophysiological evaluations were carried out.

Results

Significantly greater improvements in electrophysiological recordings and improved functional outcome measures were presented in the treatment group at 12-week follow-up. Stereomicroscopic examinations disclosed prominent increases in vascularization on proximal cut edges in the oxytocin group in comparison with the control group. Higher axon counts were also found in this group.

Conclusion

Intraperitoneal oxytocin administration resulted in accelerated functional, histological, and electrophysiological recovery after different sciatic injury models in rats.

Nanotechnology versus stem cell engineering: in vitro comparison of neurite inductive potentials

Purpose

Innovative nerve conduits for peripheral nerve reconstruction are needed in order to specifically support peripheral nerve regeneration (PNR) whenever nerve autotransplantation is not an option. Specific support of PNR could be achieved by neurotrophic factor delivery within the nerve conduits via nanotechnology or stem cell engineering and transplantation.

Methods

Here, we comparatively investigated the bioactivity of selected neurotrophic factors conjugated to iron oxide nanoparticles (np-NTFs) and of bone marrow-derived stem cells genetically engineered to overexpress those neurotrophic factors (NTF-BMSCs). The neurite outgrowth inductive activity was monitored in culture systems of adult and neonatal rat sensory dorsal root ganglion neurons as well as in the cell line from rat pheochromocytoma (PC-12) cell sympathetic culture model system.

Results

We demonstrate that np-NTFs reliably support numeric neurite outgrowth in all utilized culture models. In some aspects, especially with regard to their long-term bioactivity, np-NTFs are even superior to free NTFs. Engineered NTF-BMSCs proved to be less effective in induction of sensory neurite outgrowth but demonstrated an increased bioactivity in the PC-12 cell culture system. In contrast, primary nontransfected BMSCs were as effective as np-NTFs in sensory neurite induction and demonstrated an impairment of neuronal differentiation in the PC-12 cell system.

Conclusion

Our results evidence that nanotechnology as used in our setup is superior over stem cell engineering when it comes to in vitro models for PNR. Furthermore, np-NTFs can easily be suspended in regenerative hydrogel matrix and could be delivered that way to nerve conduits for future in vivo studies and medical application.

Effect of locally administered ciliary neurotrophic factor on the survival of transected and repaired adult sheep facial nerve

OBJECTIVE

to determine whether the administration of Ciliary Neurotrophic Factor (CNTF) at the site of repaired facial nerve enhances regeneration in the adult sheep model.

METHODS

Ten adult sheep were divided into 2 groups: control and study group (CNTF group). In the CNTF group, the buccal branch of the facial nerve was transected and then repaired by epineural sutures. CNTF was injected over the left depressor labii maxillaris muscle in the vicinity of the transected and repaired nerve for 28 days under local anesthesia. In the CNTF group, the sheep were again anesthetized after nine months and the site of facial nerve repair was exposed. Detailed electrophysiological, tension experiments and morphometric studies were carried out and then analyzed statistically.

RESULTS

The skin CV min, refractory period, Jitter and tension parameters were marginally raised in the CNTF group than the control but the difference was statistically insignificant between the two groups. Morphometric indices also did not show any significant changes in the CNTF group.

CONCLUSION

CNTF has no profound effect on neuronal regeneration of adult sheep animal model.

KEYWORDS

CNTF; Neurtrophic factors; Sheep; Facial nerve; Regeneration.

Neural tissue engineering options for peripheral nerve regeneration

Tissue engineered nerve grafts (TENGs) have emerged as a potential alternative to autologous nerve grafts, the gold standard for peripheral nerve repair. Typically, TENGs are composed of a biomaterial-based template that incorporates biochemical cues. A number of TENGs have been used experimentally to bridge long peripheral nerve gaps in various animal models, where the desired outcome is nerve tissue regeneration and functional recovery. So far, the translation of TENGs to the clinic for use in humans has met with a certain degree of success. In order to optimize the TENG design and further approach the matching of TENGs with autologous nerve grafts, many new cues, beyond the traditional ones, will have to be integrated into TENGs. Furthermore, there is a strong requirement for monitoring the real-time dynamic information related to the construction of TENGs. The aim of this opinion paper is to specifically and critically describe the latest advances in the field of neural tissue engineering for peripheral nerve regeneration. Here we delineate new attempts in the design of template (or scaffold) materials, especially in the context of biocompatibility, the choice and handling of support cells, and growth factor release systems. We further discuss the significance of RNAi for peripheral nerve regeneration, anticipate the potential application of RNAi reagents for TENGs, and speculate on the possible contributions of additional elements, including angiogenesis, electrical stimulation, molecular inflammatory mediators, bioactive peptides, antioxidant reagents, and cultured biological constructs, to TENGs. Finally, we consider that a diverse array of physicochemical and biological cues must be orchestrated within a TENG to create a self-consistent coordinated system with a close proximity to the regenerative microenvironment of the peripheral nervous system.

The use of fiber-reinforced scaffolds cocultured with Schwann cells and vascular endothelial cells to repair rabbit sciatic nerve defect with vascularization

To explore the feasibility of biodegradable fiber-reinforced 3D scaffolds with satisfactory mechanical properties for the repair of long-distance sciatic nerve defect in rabbits and effects of vascularized graft in early stage on the recovery of neurological function, Schwann cells and vascular endothelial cells were cocultured in the fiber-reinforced 3D scaffolds. Experiment group which used prevascularized nerve complex for the repair of sciatic nerve defect and control group which only cultured with Schwann cells were set. The animals in both groups underwent electromyography to show the status of the neurological function recovery at 4, 8, and 16 weeks after the surgery. Sciatic nerve regeneration and myelination were observed under the light microscope and electron microscope. Myelin sheath thickness, axonal diameter, and number of myelinated nerve fiber were quantitatively analyzed using image analysis system. The recovery of foot ulcer, the velocity of nerve conduction, the number of regenerating nerve fiber, and the recovery of ultrastructure were increased in the experimental group than those in the control group. Prevascularized tissue engineered fiber-reinforced 3D scaffolds for the repair of sciatic nerve defects in rabbits can effectively promote the recovery of neurological function.

Spatiotemporal expression of SKIP after rat sciatic nerve crush

Ski-interacting protein (SKIP) is a highly conserved protein from yeast to Human. As an essential spliceosomal component and transcriptional co-regulator it plays an important role in preinitiation, splicing and polyadenylation. SKIP can also combine with Ski to overcome the G1 arrest and the growth-suppressive activities of pRb. Furthermore SKIP has the capacity to augment TGF-β dependent transcription. While the distribution and function of SKIP in peripheral nervous system lesion and regeneration remain unclear. Here, we investigated the spatiotemporal expression of SKIP in an acute sciatic nerve crush model in adult rats. Western Blot analysis revealed that SKIP was expressed in normal sciatic nerves. It gradually increased, reached a peak at 1 week after crush, and then returned to the normal level at 4 weeks. Besides, we observed that up-regulation of SKIP was approximately in parallel with Proliferating cell nuclear antigen (PCNA), and numerous Schwann cells (SCs) expressing SKIP were PCNA and Ki-67 positive. Collectively, we hypothesized peripheral nerve crush induced up-regulation of SKIP in the sciatic nerve, which was associated with SCs proliferation.

The embracing end-to-side neurorrhaphy in rats

PURPOSE

Compare two new methods with the traditional end-to-side neurorrhaphy.

METHODS

Rats were divided into four groups. In A-L group the peroneal nerve was sectioned and the distal stump was connected to the lateral of the tibial nerve (donor) with two 10-0 nylon points. In A-R group two perineurium flaps embraced the donor nerve. In the B-R group a suture embraced the donor nerve. Group B-L was the control. After six months tibial cranial muscle mass and morphometry of the distal stump of the peroneal nerve were evaluated.

RESULTS

Muscle mass in groups A-R, A-L and B-R were lower than B-L group (p<0.0001) an equal between themselves (p>0.05). Groups A-R, B-R and A-L had a lower number of nerve fibers when compared with B-L (p=0.0155, p=0.016, p=0.0021).

CONCLUSION

The three types of neurorrhaphy showed no differences related to muscle mass and number of nerve fibers suggesting that the embracing with a single suture has great potential due its simplicity and usefulness in deep areas.

Neurodegeneration and neuroregeneration in Chagas disease

Autonomic dysfunction plays a significant role in the development of chronic Chagas disease (CD). Destruction of cardiac parasympathetic ganglia can underlie arrhythmia and heart failure, while lesions of enteric neurons in the intestinal plexuses are a direct cause of aperistalsis and megasyndromes. Neuropathology is generated by acute infection when the parasite, though not directly damaging to neuronal cells, elicits immune reactions that can become cytotoxic, inducing oxidative stress and neurodegeneration. Anti-neuronal autoimmunity may further contribute to neuropathology. Much less clear is the mechanism of subsequent neuronal regeneration in patients that survive acute infection. Morphological and functional recovery of the peripheral neurons in these patients correlates with the absence of CD clinical symptoms, while persistent neuronal deficiency is observed for the symptomatic group. The discovery that Trypanosoma cruzi trans-sialidase can moonlight as a parasite-derived neurotrophic factor (PDNF) suggests that the parasite might influence the balance between neuronal degeneration and regeneration. PDNF functionally mimics mammalian neurotrophic factors in that it binds and activates neurotrophin Trk tyrosine kinase receptors, a mechanism which prevents neurodegeneration. PDNF binding to Trk receptors triggers PI3K/Akt/GSK-3β and MAPK/Erk/CREB signalling cascades which in neurons translates into resistance to oxidative and nutritional stress, and inhibition of apoptosis, whereas in the cytoplasm of infected cells, PDNF represents a substrate-activator of the host Akt kinase, enhancing host-cell survival until completion of the intracellular cycle of the parasite. Such dual activity of PDNF provides sustained activation of survival mechanisms which, while prolonging parasite persistence in host tissues, can underlie distinct outcomes of CD.

Platelet-rich plasma: a promising product for treatment of peripheral nerve regeneration after nerve injury

Nerve regeneration includes regrowth of injured axons as well as myelination, restoration of synaptic connections and recovery of physiological functions. Platelet-rich plasma (PRP) is prepared from the patient's own blood and contains growth factors that influence wound healing and used in various surgical fields including oral and maxillofacial surgery. When platelets are activated either ex vivo or in vivo, growth factors and proteins were released from platelets' alpha granules. Recent studies proved that PRP could promote regeneration of injured peripheral nerve. This review focuses on current trials using PRP to promote nerve regeneration and repairment, and proposes potential clinical application of PRP for nerve injury in the future.

BDNF mRNA expression is significantly upregulated in vestibular schwannomas and correlates with proliferative activity

The expression of neurotrophic factors, such as artemin, glial cell line-derived neurotrophic factor (GDNF), neurturin, transforming growth factors (TGF)-beta1/beta2 and brain-derived neurotrophic factor (BDNF), is enhanced in vestibular schwannomas compared to peripheral nerves. Furthermore, this upregulation may correlate with mitotic activity. Vestibular schwannoma arising from Schwann cells of the vestibular nerve are mostly benign and slow-growing. Most of the pathogenic mechanisms regulating the vestibular schwannoma growth process are unknown. An impaired growth regulation and imbalance between mitosis and apoptosis can be assumed. However, molecular mechanisms interfering with regulation of the vestibular schwannoma growth also modulated by mitogenic factors have to be identified. Neurotrophic factors are involved in regulation of developmental processes in neuronal tissues and regeneration after peripheral nerve trauma and also reveal mitogenic effects on glial cell populations. Gene expression profiles of artemin, BDNF, GDNF, TGF-beta1/beta2 and Ret were determined in the vestibular schwannoma in comparison to the peripheral nerve tissues by using semiquantitative RT-PCR. The expression data were correlated to the proliferation-associated Ki-67 labelling index. A significant higher BDNF expression was observed in the vestibular schwannoma, whereas gene expression of artemin and GDNF was upregulated in peripheral nerves. The correlation between LI and BDNF, TGF-beta1 and Ret was found to be significant in the vestibular schwannoma. Our results demonstrate a coherence between BDNF expression and proliferative activity in the vestibular schwannoma. Based on these results, we propose a pivotal role for BDNF in modulating the vestibular schwannoma growth.

Epidermal growth factor receptor inhibitors promote CNS axon growth through off-target effects on glia

Administration of epidermal growth factor receptor (EGFR) inhibitors (e.g. AG1478/PD168393) promotes central nervous system (CNS) axon regeneration in vivo by an unknown mechanism. Here, we show that EGFR activation is not required for AG1478-/PD168393-induced neurite outgrowth in cultures of dorsal root ganglion neurons (DRGN) with added inhibitory CNS myelin extract (CME), but is mediated by the paracrine and autocrine actions of the glia-/neuron-derived neurotrophins (NT) NGF, BDNF and NT-3 through Trk signalling in DRGN potentiated by elevated cAMP levels. The DRGN neurite growth seen in CME-inhibited cultures treated with AG1478 is eradicated by blocking Trk signalling but undiminished after siRNA knockdown of >90% EGFR. Moreover, addition of the combined triplet of NT restores neurite outgrowth in CME-inhibited cultures, when cAMP levels are raised. Accordingly, we suggest that chemical EGFR inhibitors act independently of EGFR, inducing glia and neurons to secrete NT and raising cAMP levels in DRG cultures, leading to Trk-dependent disinhibited DRGN neurite outgrowth.