Diameter Of Myelinated Fibers Research Articles

Electroacupuncture alleviates sciatic nerve injury and inhibits autophagy in rats.

Sciatic nerve injury is a common form of peripheral nerve injury (PNI). It has been suggested that electroacupuncture (EA) stimulation at GB30 and ST36 can improve nerve dysfunction post-PNI. Autophagy is an important factor in the regeneration of sciatic nerves and recovery of motor function. Therefore, we investigated the biological effects of EA and examined whether these were mediated by autophagy in sciatic nerve injury. Mechanical clamping of the sciatic nerve in Sprague-Dawley rats was performed to establish an experimental model of sciatic nerve injury. EA stimulation was administered once daily for 15 min for seven consecutive days beginning 1 week after successful modeling. The recovery of sciatic nerve function was examined via the sciatic functional index (SFI) test. Morphometric analysis was conducted by staining nerve samples with toluidine blue. Autophagy-associated protein levels were measured via Western blotting. EA stimulation at GB30 and ST36 significantly increased the number of myelinated fibers, axonal and fiber diameters, and the thickness of the myelin sheath in our rat model of sciatic nerve injury. In addition, EA stimulation greatly facilitated nerve regeneration following sciatic nerve injury. Moreover, sciatic nerve injury-induced autophagy was inhibited by EA stimulation. EA facilitates recovery of injured sciatic nerves and inhibits autophagy in a rat model.

Evaluation of long-term results of single intraoperative electrical neurostimulation after autologous plastic surgery of a resection defect of the tibial portion of the sciatic nerve in adult rats

Introduction World literature data indicate the effectiveness of single intraoperative electrical stimulation (IES) of the proximal segment of the damaged nerve to stimulate its regeneration, but there is no data on its effect on the long-term results of autoplasty of resection defects.The purpose of the work was to evaluate the long-term results of a single IES after autologous plastic surgery of the tibial portion of the sciatic nerve in rats.Materials and methods Thirty rats after autologous repair of the resection defect of the tibial portion of the sciatic nerve were divided into series 1 (unstimulated control, n = 16) and series 2 (single IES for 40 minutes, n = 14). At 4 and 6 months after surgery, the static sciatic functional index (SFI) and morphometry of epoxy transverse semithin sections of the tibial nerve at the level of the middle third of the leg were assessed. For comparison with the normal values, the corresponding data from 7 intact rats were used.Results The number of animals with excellent results of SFI restoration was 12.5 % in series 1 and 50 % in series 2 (p = 0.05). The numerical density of regenerated myelinated fibers (MF) exceeded the norm: in series 1 — by 63 % (p < 0.01) and 34 % (p < 0.01), in series 2 — by 58 % (p < 0.01) and 47 % (p < 0.01), respectively. In series 2, there were greater values in comparison with series 1: the median diameters of MFs were by 11.7 % and 15.7 %, the median diameters of their axons were by 5.4 % and 11.9 %, the median thickness of the myelin sheath was by 17.0 % and 24.1 %, respectively (p < 0.05 4 months and p < 0.01 6 months after surgery). Four months after surgery in series 1 and 2, the numerical densities of endoneurial vessels exceeded the intact control by 134 % (p < 0.05) and 156 % ( 0.05), their average diameters by 18 % and 16 % (p < 0.01) respectively, and lumen diameters increased only in series 2 by 8 % (p = 0.07). After 6 months of the experiment in series 1 and 2, the numerical densities of microvessels decreased, but significantly exceeded the control by 66 % (p < 0.05) and 83 % (p < 0.05), the average diameters — by 14 % and 36 % (p < 0.05), lumen diameters — by 26 % (p < 0.05) and 50 % (p < 0.01), respectively.Discussion The difference between stimulated and unstimulated animals in all MF size parameters 6 months after surgery was greater than after 4 months, indicating a persistent neuroregenerative effect.Conclusions A significant increase in the diameters of regenerating nerve fibers in the tibial nerve, as well as the diameters of their axons and the thickness of the myelinated sheaths 4 and 6 months after autoplasty of the tibial portion of the sciatic nerve in the group of animals with a single 40-minute IES of the proximal portion of the sciatic nerve indicates the promoting effect of the applied additive effect on regenerative axono- and myelinogenesis. Increase in the lumens and improvement of blood flow of the endoneurial vessels of the tibial nerve in the series with IES ensured the stability of the neuroregenerative effect. The functional significance of the effects of a single IES is confirmed by a significantly higher percentage of animals with excellent results in restoring the static functional index.

Experimental unilateral intracerebral hemorrhage induces delayed bilateral neurodegeneration of sciatic nerve fibres in rats.

Pathological processes, such as inflammatory effects, oxidative stress, apoptosis and cytotoxicity of blood after an intracerebral hemorrhage (ICH), generally contribute to a secondary injury. One of the secondary ICH consequences in the nervous system may be delayed neurodegeneration of the peripheral nerves. Therefore, the aim of our study was to investigate possible structural changes in the sciatic nerve and changes in the conduction velocity via this nerve at different terms after experimental ICH in male Wistar rats. Intracerebral hemorrhage was provided by direct injection of autologous blood into the capsula interna. On the 10th day after ICH mean conduction velocity in sciatic nerve was 15% smaller compared to the control. On the 30th and 90th days after ICH, highly significant decreases in the conduction velocity by 62% and 60%, respectively in comparison with the control group of animals were observed. The data of morphometric analysis demonstrated significant decreases in the mean diameter and density of myelinated fibres at all examined terms after ICH. A number of the myelin sheaths were swollen and lost their regular laminations. Axoplasmic and myelin degenerations were the most frequent events in these nerve fibres; reductions of the diameter of the axis cylinders were also observed. In the contralateral nerve (related to the hemisphere with ICH), negative changes were greater, while the ipsilateral nerve was also subjected to those. Our data demonstrate that the consequences of unilateral ICH in the capsula interna induce bilateral negative changes in the peripheral nervous system of rats.

Influence of the Neuroprotective Properties of Quercetin on Regeneration and Functional Recovery of the Nervous System.

Quercetin is a dietary flavonoid present in vegetables, fruits, and beverages, such as onions, apples, broccoli, berries, citrus fruits, tea, and red wine. Flavonoids have antioxidant and anti-inflammatory effects, acting in the prevention of several diseases. Quercetin also has neuroprotective properties and may exert a beneficial effect on nervous tissue. In this literature review, we compiled in vivo studies that investigated the effect of quercetin on regeneration and functional recovery of the central and peripheral nervous system. In spinal cord injuries (SCI), quercetin administration favored axonal regeneration and recovery of locomotor capacity, significantly improving electrophysiological parameters. Quercetin reduced edema, neutrophil infiltration, cystic cavity formation, reactive oxygen species production, and pro-inflammatory cytokine synthesis, while favoring an increase in levels of anti-inflammatory cytokines, minimizing tissue damage in SCI models. In addition, the association of quercetin with mesenchymal stromal cells transplantation had a synergistic neuroprotective effect on spinal cord injury. Similarly, in sciatic nerve injuries, quercetin favored and accelerated sensory and motor recovery, reducing muscle atrophy. In these models, quercetin significantly inhibited oxidative stress and cell apoptosis, favoring Schwann cell proliferation and nerve fiber remyelination, thus promoting a significant increase in the number and diameter of myelinated fibers. Although there is still a lack of clinical research, in vivo studies have shown that quercetin contributed to the recovery of neurological functions, exerting a beneficial effect on the regeneration of the central and peripheral nervous system.

Negative neuromuscular and functional repercussion of forced swimming after axonotmesis

Peripheral nerve injuries are cause of sensory disturbances and in functional abilities, and are associated personal and social costs. Strategies that maximize nerve regeneration and functional recovery are necessary, the exercise is an option. This study evaluated the effects of forced swimming exercise on neuromuscular histomorphometry and on functional recovery in a median nerve crush model. Sixteen Wistar rats underwent median nerve crush and were divided into control group (CG) and swimming group (SG). The forced swimming protocol started one week after the injury and was performed for 1 hr a day, 5 days per week, for 2 weeks. The rats swam with an overload of 5% and 10% of body weight in the first and second week, respectively. The functional recovery was assessed in three moments using the grasping test. On day 21, fragments of the median nerve and of the forearm flexors muscles were removed for histomorphometric analysis. The SG had functional recovery impaired (P<0.001) and presented lower myelinated fibers number, fiber and axon minimal diameter, myelin thickness and g-ratio in the proximal e distal segments of the median nerve (P<0.005) and area muscle fiber (P<0.005) than CG. Also, the SG presented a number of capillaries in the proximal segments of the median nerve greater than CG (P<0.005). The exercise protocol used in this study impaired the regeneration of the median nerve and negatively influenced the functional recovery.

Application of Human Epineural Conduit Supported with Human Mesenchymal Stem Cells as a Novel Therapy for Enhancement of Nerve Gap Regeneration

Various therapeutic methods have been suggested to enhance nerve regeneration. In this study, we propose a novel approach for enhancement of nerve gap regeneration by applying human epineural conduit (hEC) supported with human mesenchymal stem cells (hMSC), as an alternative to autograft repair. Restoration of 20 mm sciatic nerve defect with hEC created from human sciatic nerve supported with hMSC was tested in 4 experimental groups (n = 6 each) in the athymic nude rat model (Crl:NIH-Foxn1rnu): 1 - No repair control, 2 - Autograft control, 3 - Matched diameter hEC filled with 1 mL saline, 4 - Matched diameter hEC supported with 3 × 106 hMSC. Assessments included: functional tests: toe-spread and pinprick, regeneration assessment by immunofluorescence staining: HLA-1, HLA-DR, NGF, GFAP, Laminin B, S-100, VEGF, vWF and PKH26 labeling; histomorphometric analysis of myelin thickness, axonal density, fiber diameter and myelinated nerve fibers percentage; Gastrocnemius Muscle Index (GMI) and muscle fiber area ratio. Best sensory and motor function recovery, as well as GMI and muscle fiber area ratio, were observed in the autograft group, and were comparable to the hEC with hMSC group (p = 0.038). Significant improvements of myelin thickness (p = 0.003), fiber diameter (p = 0.0296), and percentage of myelinated fibers (p < 0.0001) were detected in hEC group supported with hMSC compared to hEC with saline controls. At 12-weeks after nerve gap repair, hEC combined with hMSC revealed increased expression of neurotrophic and proangiogenic factors, which corresponded with improvement of function comparable with the autograft control. Application of our novel hEC supported with hMSC provides a potential alternative to the autograft nerve repair.Graphical

Histomorphometry in Peripheral Nerve Regeneration: Comparison of Different Axon Counting Methods

Histomorphometry quantitatively evaluates nerve regeneration. Total myelinated fiber count (TMFC) is most accurately obtained manually across full nerve cross-sections, but most researchers opt for automated, sampled analysis. Few of the numerous techniques available have been validated. The goal of this study was to compare common histomorphometric methods (full manual [FM], sampled manual [SM], and sampled automatic [SA]) to determine their reliability and consistency. Twenty-four rats underwent sciatic nerve (SN) repair with 20mm isografts; SNs distal to the graft were analyzed. TMFC was manually determined in each full cross-section. Counts were also extrapolated from sampled fields, both manually and automatically with ImageJ software. Myelinated fiber diameter, axon diameter, and myelin sheath thickness were measured manually in full and sampled fields; G-ratio was calculated. Repeated-measures MANOVA, Spearman correlation, and Wilcoxon signed-rank tests were performed. A systematic review of histomorphometry in rat SN repair was performed to analyze the variability of techniques in the literature. FM TMFC was 13,506 ± 4,217. Both sampled methods yielded significantly different TMFCs (SM:14.4 ± 13.4%, P< 0.001; SA:21.8 ± 44.7%, P=0.037). All three methods strongly correlated with each other, especially FM and SM (rs=0.912, P< 0.001). FM fiber diameter, axon diameter, and myelin sheath thickness did not differ from SM (P=0.493, 0.209, and 0.331, respectively). 65% of papers used sampling; 78% utilized automated or semi-automated analysis. Software, sampling, and histomorphometric parameters varied widely. SM and SA analysis are reliable with standardized, systematic sampling. Transparency is essential to allow comparison of data; meanwhile, researchers must be cognizant of the wide variety of methodologies in the literature.

Low-Intensity Pulsed Ultrasound Prompts Both Functional and Histologic Improvements While Upregulating the Brain-Derived Neurotrophic Factor Expression after Sciatic Crush Injury in Rats

The aim of this study was to determine that low-intensity pulsed ultrasound (LIPUS) at an intensity of 140 mW/cm2 promotes functional and histologic improvements in sciatic nerve crush injury in a rat model and to investigate changes over time in relevant growth factors and receptors, exploring the mechanism of LIPUS in the recovery process after injury. Toe angle in the toe-off phase, regenerative axonal length, myelinated nerve fiber density, diameter of myelinated nerve fiber, axon diameter and myelin sheath thickness were significantly higher in the LIPUS group than in the sham group. Gene and protein expression of brain-derived neurotrophic factor (BDNF) was upregulated in the LIPUS group. In conclusion, LIPUS contributed to rapid functional and histologic improvement and upregulated BDNF expression after sciatic nerve crush injury in rats.

Ultrastructural and morphometric alterations to the peripheral nerve following the administration of immunosuppressive agent tacrolimus (FK506)

ABSTRACT Tacrolimus, a widely used immunosuppressive drug for preventing graft rejection following organ transplantation, was reported to develop neurotoxic side effects ranging from mild to severe symptoms in the literature. Rats were randomly divided into three groups as control and 2-week and 3-week treatment groups and received a 2 mg/kg/day tacrolimus by oral gavage. Animals were sacrificed and sciatic nerves obtained from all groups were fixed and processed for light and electron microscopic investigations. The myelinated fiber diameter, axon diameter, G-ratio (axon diameter/myelinated fiber diameter), and myelin thickness were also determined. The data obtained in the control and tacrolimus-treated groups were compared. The control group sciatic nerve fascicles showed normal morphology with myelinated and unmyelinated fibers. Experimental groups exhibited axonal dilatation, irregularly thickened and vacuolated myelin sheaths with separation of myelin layers. The morphometric analysis showed that the myelinated fibers of the 2-week tacrolimus-treated group displayed a moderate increase in the myelin thickness and axon and fiber diameter in comparison with the control and 3-week tacrolimus-treated groups. The G-ratio was found to be in normal range in all groups and there were no statistically significant difference. The present study indicates that the treatment with tacrolimus may produce a mild degenerative change but prolonged drug administration for 3 weeks led to improvement in morphometric and morphologic data and the normal G-ratio values, suggesting that the regeneration capacity of the myelinated fibers maintains their normal function to transmit nerve impulses.

Conventional histomorphometry and fast free of acrylamide clearing tissue (FACT) visualization of sciatic nerve in chicken (Gallus domesticus).

Histomorphometry and use of the fast free of acrylamide clearing tissue (FACT) protocol were studied on the sciatic nerve in chicken (Gallus domesticus). In the first part of the study, the sciatic nerves of 20 chickens of four age groups (7, 14, 26 and 40 days) were studied (n=5 birds per age class). Their sciatic nerve samples were stained with Hematoxylin and Eosin and Masson's trichrome and were histomorphometrically evaluated. In the second part of the study, FACT protocol was applied on the sciatic nerve of a 26 days old chicken. After clearing of 1.00 mm-thick sciatic nerve sections, they were immunolabelled using Hoechst for nuclei staining and recorded by a Z-stack motorized fluorescent microscope. In the conventional histo-morphometry, the epineurium, perineurium and endoneurium were thicker and the nerve bundle diameter was bigger in the left sciatic nerve of chicken of all age groups compared to the right sciatic nerve. On the contrary, the axon diameter and the myelinated nerve fiber diameter were bigger, the myelin sheath was thicker, the nodes of Ranvier intervals were higher and the density of myelinated nerve fibers was also higher in the right sciatic nerve compared to the left one. In conclusion, histomorphometric parameters in the left and right sciatic nerve during chicken growth were significantly different. Furthermore, the FACT protocol could be used for the 3D imaging of the chicken sciatic nerve and its immunostained evaluation.

Sympathetic innervation of canine pulmonary artery and morphometric and functional analysis in dehydromonocrotaline-induced models after pulmonary artery denervation.

We aimed to describe the anatomic distribution of periarterial pulmonary sympathetic nerves and to observe the long-term morphometric and functional changes after pulmonary artery denervation (PADN), a novel therapy for pulmonary arterial hypertension (PAH). A total of 45 beagles were divided into a sympathetic innervation group (n = 3, 33.3% were females), a PAH group (n = 35, 34.3% were females) and a control group (n = 7, 28.5% were females). The PAH group was randomly divided into no-PADN (n = 7), instant-PADN (n = 7), 1M-PADN (n = 7), 2M-PADN (n = 7) and 3M-PADN (n = 7) subgroups. The sympathetic innervation group was sacrificed to reveal the sympathetic innervation of pulmonary arteries. PAH was induced by injecting dehydromonocrotaline (DHMCT) through the right atrium. The pulmonary capillary wedge pressure, right ventricular systolic pressure, right ventricular mean pressure, pulmonary artery systolic pressure and pulmonary artery mean pressure of each group were continuously measured. The cardiac output was detected to calculate the pulmonary vascular resistance. PAH and control groups were subjected to immunofluorescence assay, sympathetic nerve conduction velocity measurement and transmission electron microscopy. The no-PADN group had significantly higher PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but lower cardiac output than those of the control group (P < 0.05). Instant-PADN, 1M-PADN, 2M-PADN and 3M-PADN groups had significantly lower PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but higher cardiac output than those of the no-PADN group (P < 0.05). Most sympathetic nerves were located within 2.5 mm of the intimae of the bifurcation and proximal trunk, mainly in the left trunk. The diameter and cross-sectional area of myelinated fibres in the PAH group were significantly larger than those of the control group. Sympathetic nerve conduction velocity of the PAH group gradually decreased, and nerve fibres were almost demyelinated 3 months after PADN. PADN effectively relieved dehydromonocrotaline-induced canine PAH and decreased sympathetic nerve conduction velocity.

Assessments of regenerative potential of silymarin nanoparticles loaded into chitosan conduit on peripheral nerve regeneration: a transected sciatic nerve model in rat

ABSTRACT Purpose It is compulsory to make a tension-free, end-to-end repair in transected injuries. However, when it comes to longer defects, placement of an autograft or nerve conduits is required. The present study was designed to assess regenerative potential of silymarin nanoparticles loaded into chitosan conduit on peripheral nerve regeneration in a transected sciatic nerve model in rat. Methods In NML group left sciatic nerve was exposed through a gluteal muscle incision and after careful hemostasis skin was closed. In TSC group left sciatic nerve was transected and stumps were fixed in adjacent muscle. In CTN group, 10-mm sciatic nerve defects were bridged using a chitosan. In CTN/NSLM group, 10-mm sciatic nerve defects were bridged using a chitosan conduit and 100 µL silymarin nanoparticles were administered into the conduit. The regenerated fibers were studied 4, 8, and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional, biomechanical, histomorphometric, and immuohistochemical criteria. Results The behavioral, functional, electrophysiological, and biomechanical studies confirmed significant recovery of regenerated axons in CTN/NSLM group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed number and diameter of myelinated fibers in CTN/NSLM group were significantly higher than in CTN group (P < 0.05). Discussion This demonstrated potential of using chitosan-silymarin nanoparticles in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation of autograft. It is also cost saving and may have clinical implications for surgical management of patients after peripheral nerve transection.

Histomorphometry in Peripheral Nerve Regeneration: Experimental Comparison of Different Axon Counting Methods

PURPOSE: Histomorphometry is a common tool to quantitatively evaluate outcomes of peripheral nerve regeneration by measuring axonal parameters such as count, diameter, and myelination. Manual measurement across the entire nerve cross-section is the most accurate technique of histomorphometric analysis but is extremely labor intensive. Thus, most researchers have opted for analysis of just a sample of the cross-section. Currently, automated sampled analysis is the most common method. However, no study has been performed to compare the accuracy of these techniques, making it difficult to compare results across the literature. METHODS: Rat sciatic nerves were transected and repaired with a 20 mm nerve isograft. A total of 34 sections were stained with toluidine blue and digitized: 24 from native nerve distal to the graft, 5 from nerve proximal to the graft, and 5 from the graft itself. Three blinded researchers manually counted total myelinated fibers in each full cross-section. Total myelinated fiber counts were also extrapolated from sampled fields representing 20% of the cross-sectional area. Sampled counts were performed both manually and automatically with the software ImageJ (National Institutes of Health). Myelinated fiber diameter (FD), axon diameter (AD), and myelin sheath thickness (MTh) were measured manually in the full cross-sections and the sampled fields. Repeated measures MANOVA, Spearman’s correlation, and Wilcoxon signed-rank tests were performed. RESULTS: Results are expressed in mean ± standard deviation. Full manual axon count was 12,504 ± 4,195 overall and 13,506 ± 4,217 distally. Sampled axon counts were significantly higher than full manual, especially distally (sampled manual: 15,316 ± 4,613, P < 0.001; sampled automated: 16,297 ± 7,733, P = 0.037). All three methods showed strong, significant correlation with each other, especially for distal sections (full manual and sampled manual: rs = 0.912, P < 0.001; full manual and sampled automated: rs = 0.599, P = 0.002; sampled manual and sampled automated: rs = 0.708, P < 0.001). Overall full manual fiber diameter, axon diameter, and myelin sheath thickness were 5.42 ± 1.18 µm, 3.61 ± 0.78 µm, and 0.93 ± 0.28 µm, respectively. They did not differ from sampled measurements (P = 0.144, P = 0.059, and P = 0.817, respectively). CONCLUSIONS: Manual count of sampled nerve sections produces highly correlated, reliable results when using standardized and systematic sampling methods. Automated data should be regarded with more caution as correlation was not as high. However, the significant correlation indicates it is an acceptable technique if manual sampled analysis is not possible. Although the methods explored in this study correlated highly with one another, the accuracy of both sampled techniques differed significantly from full manual analysis. Therefore, comparison of numerical results between papers reporting these parameters (ie, for a metanalysis) may not be possible. Researchers must be cognizant of the wide variety of techniques reported in the literature and exercise caution when comparing data between studies.

Structural Changes in the Posterior Interosseous Nerve from Patients with Wrist Osteoarthritis and Asymptomatic Controls

Background Posttraumatic morphological changes have been described in the posterior interosseous nerve (PIN) after mild wrist trauma, and it has been suggested that posttraumatic nerve changes may contribute to wrist pain. PIN excision has shown to relieve pain in some patients with wrist osteoarthritis. However, is not known if PINs from osteoarthritic wrist have pathological features. Objective The aim of this study was to investigate whether PINs from osteoarthritic wrists show morphological changes that are not present in healthy wrists. Materials and Methods PINs resected from 15 osteoarthritic wrists were analyzed with light microscopy regarding morphological changes and compared with five asymptomatic controls without osteoarthritis. Results No significant differences in fascicular area, myelinated fiber density or myelinated fiber diameter were found. However, most patients and controls exhibited some degree of pathology, and a few samples from both groups exhibited severe pathological changes. Conclusions Our findings of morphological changes in both patients with osteoarthritis and asymptomatic controls suggest that pathological changes of unknown significance might exist in the general population in the PIN at wrist level. We believe that the observed structural nerve changes in the PIN are unlikely to contribute to the symptoms of pain. Further studies of the normal histological appearance of the terminal PIN are needed. Level of Evidence This is Level II study.

Metformin Preserves Peripheral Nerve Damage with Comparable Effects to Alpha Lipoic Acid in Streptozotocin/High-Fat Diet Induced Diabetic Rats.

BackgroundMetformin is widely marketed medication for the treatment of diabetes, but its pharmacological effect on diabetic peripheral neuropathy remains unclear. In this study, the effect of metformin on peripheral nerves in diabetic rats was investigated using diverse neuronal parameters of nerve fibers.MethodsRats were assigned to one of four groups (n=7 to 10 per group): normal, diabetes mellitus (DM), DM+metformin (100 mg/kg), and DM+alpha lipoic acid (ALA, 100 mg/kg). DM was induced by streptozotocin/high-fat diet (STZ/HFD). After 12 weeks, the sensory thresholds to mechanical and heat stimuli were assessed. Repeated sensory tests, immunofluorescence microscopic comparison of peripheral nerves, and biochemical blood analysis were performed after 24 weeks.ResultsBoth DM+metformin and DM+ALA groups showed similar trends to diverse sensory tests at 24 weeks compared to DM group although the degree of change were different according to the stimulated senses. There was no significant difference in the comparison of the intraepidermal nerve fiber density (IENFD) of peripheral nerves between the DM+metformin and DM+ALA groups (11.83±0.07 fibers/mm vs. 12.37±1.82 fibers/mm, respectively). Both groups showed preserved IENFD significantly compared with DM group (8.46±1.98 fibers/mm, P<0.05). Sciatic nerve morphology of the experimental animals showed a similar trend to the IENFD, with respect to axonal diameter, myelin sheath thickness, and myelinated fiber diameter.ConclusionMetformin has beneficial pharmacological effects on the preservation of peripheral nerves in diabetic rats and its effects are comparable to those of ALA.

Platelet-rich fibrin membrane nerve guidance conduit: a potentially promising method for peripheral nerve injuries.

Platelet-rich fibrin membrane nerve guidance conduit: a potentially promising method for peripheral nerve injuries.

Evaluation of the Antioxidant and Anti‐inflammatory Effects of SMTP‐44D against Streptozotocin‐Induced Diabetic Neuropathy in Mice

ObjectiveDiabetic neuropathy (DN), a major complication of diabetic mellitus, is present in more than 50% of diabetic patients. During the early stages of pathologic progression, patients with DN may experience sensory defects such as allodynia and hyperalgesia. Patients in advanced stages may present with sensory paralysis, such as nerve injury and the degeneration of axons, which are frequently accompanied by foot ulcerations, amputations, and poor prognoses. The pathogenesis of DN primarily involves oxidative stress and inflammation; thus, oxidative stress and inflammation are considered important therapeutic targets. However, few effective therapies are approved for the treatment of painful or insensate DN. The study aimed to evaluate the antioxidant and anti‐inflammatory effects of Stachybotrys microspora triprenyl phenol‐44D (SMTP‐44D) in a mouse model of DN.MethodsWe induced diabetes in C57BL/6J male mice by administering a single intraperitoneal injection of streptozotocin (200 mg/kg). SMTP‐44D (0.3, 3, and 30 mg/kg) was subsequently administered daily from 1 to 4 weeks after the injection of streptozotocin. The effects of SMTP‐44D were evaluated by mechanical and thermal thresholds to assess allodynia and hyperalgesia, and conduction velocity and blood flow in sciatic nerves. In addition, the levels of oxidative stress and inflammatory cytokines in sciatic nerves were determined via a thiobarbituric acid reactive substances assay and enzyme‐linked immunosorbent assay, respectively. To evaluate for neurological degeneration, G‐ratios (ratio of axon diameter to myelinated fiber diameter) and myelin thickness in the Schwann cells of sciatic nerves were measured.ResultsMechanical and thermal thresholds, conduction velocity, blood flow, and myelin thickness were significantly lower in the diabetic group than in the nondiabetic group. Moreover, the levels of oxidative stress (e.g., malondialdehyde), inflammatory cytokines (e.g., tumor necrosis factor‐α, interleukin‐1β, and interleukin‐6), and G‐ratios were significantly higher in the diabetic group than in the nondiabetic group. Such results demonstrated that the DN model was successfully established. In mice with DN, treatment with SMTP‐44D significantly and dose‐dependently improved allodynia, hyperalgesia, conduction velocity of sciatic nerves, and blood flow in sciatic nerves. Furthermore, G‐ratios and myelin thickness in the Schwann cells of sciatic nerves were also significantly improved by the suppression of oxidative stress and inflammatory cytokines.ConclusionIt is believed that oxidative stress and inflammation are involved in the pathological progression of DN and that they are important therapeutic targets. Our results showed that SMTP‐44D improved DN by exerting antioxidant and anti‐inflammatory effects, which suggests that SMTP‐44D is a potential novel therapeutic agent for the treatment of DN.Support or Funding InformationThis study was supported in part by the Japan Society for the Promotion of Science KAKENHI (Grant Number 26460346, awarded to KN; Grant Number 18K14958, awarded to KS). SMTP‐44D was generously donated by TMS Co., Ltd. (Tokyo, Japan).

Fabrication and transplantation of chitosan-selenium biodegradable nanocomposite conduit on transected sciatic nerve: a novel study in rat model

ABSTRACTPurpose: The improvement of techniques using conduits that connects the ends of damaged nerves and guides the growth of nerve fibers between the stumps, including adoption of natural or synthetic materials still is a challenge in peripheral nerve repair. The aim of the present novel study was to fabricate and transplant chitosan-selenium biodegradable nanocomposite conduit on transected sciatic nerve in rat model.Methods: In NORMAL group, the left sciatic nerve was exposed through a gluteal muscle incision and after careful hemostasis skin was closed. In TRANSECTED group left sciatic nerve was transected and stumps were fixed in adjacent muscle. In CHITOSAN and CSBNC groups, 10-mm sciatic nerve defects were bridged using a chitosan and chitosan-selenium biodegradable nanocomposite conduits, respectively. The regenerated fibers were studied 4, 8 and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional, biomechanical, histomorphometric and immunohistochemical criteria.Results: The behavioral, functional and biomechanical studies confirmed significant recovery of regenerated axons in CSBNC group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed the number and diameter of myelinated fibers in CSBNC group were significantly higher than in the CHITOSAN group (P < 0.05).Discussion: This demonstrates the potential of using CSBNC in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation autograft. It is also cost saving and may have clinical implications for the surgical management of patients after facial nerve transection.

Comparison of nerve fibers in the deciduous first and second molar teeth: an in vitro study.

Sensory nerves of the tooth pulp have been evolved in both deciduous and permanent teeth for conducting possible damages to the teeth. Although it has been reported that the deciduous tooth's pulp is histologically similar to permanent teeth, the difference in the density of nerves between the first and second deciduous molars has been reported in no studies. The aim of the study was to investigate the histological assay of pulpal nerves and assess the relationship between diameter and density of nerve fibres in the first and second deciduous molar teeth. In this in vitro study, 15 deciduous first and 16 deciduous second extracted from molar teeth belonging to children aged from 5 to 8years were studied. After fixation, the decalcified teeth were sectioned and then stained with silver solution and calcitonin gene-related peptide (CGRP) antibody. The mean diameter of myelinated fibres, un-myelinated fibres, and density of peripheral network fibres of dental pulp were examined. The results showed that the mean diameter of myelinated and non-myelinated fibres and density of nerve fibres were significantly more in the second molars (4.269, 2.328µm, 2.6 fibres per unit area) compared to the first molar teeth (3.793, 2.093µm, 1.8 fibres per unit area) (P < 0.032, 0.019, 0.003, respectively). An important finding in this study, which is reported for the first time, is the presence of fatty cells (adipocytes) in pulp tissue of some of the first deciduous molars as well as the second molars. Based on the results of the current study, differences between nerve fibres of first and second molar teeth are significant. It could be concluded that the less sensitivity to pain of the first deciduous molars compared with the second deciduous molars, is due to the lower nerve density of this tooth.

The effect of propolis-gum arabic as a novel nerve guidance channel on regeneration of sciatic nerve in male rats

To investigate the effect of Propolis-gum Arabic as a nerve guidance channel. Male rats (n=24) were randomly divided into sham surgery, autograft, and Propolis+gum Arabic groups with equal numbers. Under anesthesia, the sciatic nerve was removed, and the gap between the two ending was repaired by Propolis-gum Arabic or nerve autograft. Nerve regeneration was evaluated by sciatic function index (SFI), withdrawal reflex latency (WRL), muscle fiber diameter, number of myelinated axons, myelinated fiber diameter, and immunohistochemical analysis. At 30, 49, 60 and 90 days after surgery, the mean of SFI in Propolis + gum Arabic group was significantly greater than the autograft group (p < 0.03). The mean muscle fiber diameters (30 and 90 days after surgery) and the mean number of myelinated axons (90 days after surgery) in Propolis + gum Arabic group were significantly greater than autograft group (p < 0.05). In addition, 90 days after surgery, the mean myelinated fiber diameter in Propolis + gum Arabic group was significantly higher than autograft group (p < 0.05). The results of this study suggest that as guidance channel, the Propolis + gum Arabic may be useful in peripheral nerve regeneration.