Time-dependent proregenerative effects of exogenous melatonin on the transected sciatic nerve / Efectos proregenerativos dependientes del tiempo de la melatonina exógena en el nervio ciático seccionado

SUMMARY: Microsurgical procedures are the treatment of choice of peripheral nerve injuries, but often fail to reach full functional recovery. Melatonin has neuroprotective actions and might be used as a possible proregenerative pharmacological support. Therefore, the aim of this study was to analyze the time-dependence of the neuroprotective effect of melatonin on the overall fascicular structures of both ends of the transected nerve. Sciatic nerve transection was performed in 34 adult male Wistar rats divided in four groups: two vehicle groups (N=7) treated intraperitoneally for 7 (V7) or 21 (V21) consecutive days with vehicle (5 % ethanol in Ringer solution) and two melatonin groups (N=10) administered intraperitoneally 30 mg/kg of melatonin for 7 (M7) or 21 (M21) consecutive days. At the end of the experiment, proximal stump neuroma and distal stump fibroma were excised and processed for qualitative and quantitative histological analysis. Intrafascicular neural structures were better preserved and the collagen deposition was reduced in the melatonin treated groups than in the vehicle groups. Myelin sheath regeneration observed through its thickness measurement was statistically significantly (p<0,05) more pronounced in the M21 (1,23±0,18 µm) vs. V21 group (0,98±0,13 µm). The mean volume density of the endoneurium was lower in both melatonin treated groups in comparison to the matching vehicle treated groups. Although not statistically different, the endoneural tube diameter was larger in both melatonin groups vs. vehicle groups, and the effect of melatonin was more pronounced after 21 days (24,97 % increase) vs. 7 days of melatonin treatment (18,8 % increase). Melatonin exerts a time-dependent proregenerative effect on nerve fibers in the proximal stump and an anti-scarring effect in both stumps.

Los procedimientos microquirúrgicos son el tratamiento de elección de las lesiones de los nervios periféricos, pero a menudo no logran una recuperación funcional completa. La melatonina tiene acciones neuroprotectoras y podría ser utilizada como un posible apoyo farmacológico proregenerativo. Por lo tanto, el objetivo de este estudio fue analizar la dependencia del tiempo del efecto neuroprotector de la melatonina sobre las estructuras fasciculares generales de ambos extremos del nervio seccionado. La sección del nervio ciático se realizó en 34 ratas Wistar macho adultas divididas en cuatro grupos: dos grupos de vehículo (N=7) tratados por vía intraperitoneal durante 7 (V7) o 21 (V21) días consecutivos con vehículo (5 % de etanol en solución Ringer) y dos grupos grupos de melatonina (N=10) a los que se les administró por vía intraperitoneal 30 mg/kg de melatonina durante 7 (M7) o 21 (M21) días consecutivos. Al final del experimento, se extirparon y procesaron el neuroma del muñón proximal y el fibroma del muñón distal del nervio para un análisis histológico cualitativo y cuantitativo. Las estructuras neurales intrafasciculares se conservaron mejor y el depósito de colágeno se redujo en los grupos tratados con melatonina respecto a los grupos con vehículo. La regeneración de la vaina de mielina observada a través de la medición de su espesor fue estadísticamente significativa (p<0,05) más pronunciada en el grupo M21 (1,23±0,18 µm) vs V21 (0,98±0,13 µm). La densidad de volumen media del endoneuro fue menor en ambos grupos tratados con melatonina en comparación con los grupos tratados con vehículo equivalente. Aunque no fue estadísticamente diferente, el diámetro del tubo endoneural fue mayor en ambos grupos de melatonina frente a los grupos de vehículo, y el efecto de la melatonina fue más pronunciado después de 21 días (aumento del 24,97 %) frente a los 7 días de tratamiento con melatonina (18,8 % de aumento). La melatonina ejerce un efecto proregenerativo dependiente del tiempo sobre las fibras nerviosas del muñón proximal y un efecto anticicatricial en ambos muñones.

Characterization of the electrical properties of mammalian peripheral nerve laminae.

BACKGROUND AND OBJECTIVE: The intrinsic electrical material properties of the laminar components of the mammalian peripheral nerve bundle are important parameters necessary for the accurate simulation of the electrical interaction between nerve fibers and neural interfaces. Improvements in the accuracy of these parameters improve the realism of the simulation and enables realistic screening of novel devices used for extracellular recording and stimulation of mammalian peripheral nerves. This work aims to characterize these properties for mammalian peripheral nerves to build upon the resistive parameter set established by Weerasuriya et al. in 1984 for amphibian somatic peripheral nerves (frog sciatic nerve) that is currently used ubiquitously in the in-silico peripheral nerve modeling community. METHODS: A custom designed characterization chamber was implemented and used to measure the radial and longitudinal impedance between 10 mHz and 50 kHz of freshly excised canine vagus nerves using four-point impedance spectroscopy. The impedance spectra were parametrically fitted to an equivalent circuit model to decompose and estimate the components of the various laminae. Histological sections of the electrically characterized nerves were then made to quantify the geometry and laminae thicknesses of the perineurium and epineurium. These measured values were then used to calculate the estimated intrinsic electrical properties, resistivity and permittivity, from the decomposed resistances and reactances. Finally, the estimated intrinsic electrical properties were used in a finite element method (FEM) model of the nerve characterization setup to evaluate the realism of the model. RESULTS: The geometric measurements were as follows: nerve bundle (1.6 ± 0.6 mm), major nerve fascicle diameter (1.3 ± 0.23 mm), and perineurium thickness (13.8 ± 2.1 µm). The longitudinal resistivity of the endoneurium was estimated to be 0.97 ± 0.05 Ωm. The relative permittivity and resistivity of the perineurium were estimated to be 2018 ± 391 and 3.75 kΩm ± 981 Ωm, respectively. The relative permittivity and resistivity of the epineurium were found to be 9.4 × 106 ± 8.2 × 106 and 55.0 ± 24.4 Ωm, respectively. The root mean squared (RMS) error of the experimentally obtained values when used in the equivalent circuit model to determine goodness of fit against the measured impedance spectra was found to be 13.0 ± 10.7 Ω, 2.4° ± 1.3°. The corner frequency of the perineurium and epineurium were found to be 2.6 ± 1.0 kHz and 368.5 ± 761.9 Hz, respectively. A comparison between the FEM model in-silico impedance experiment against the ex-vivo methods had a RMS error of 159.0 ± 95.4 Ω, 20.7° ± 9.8°. CONCLUSION: Although the resistive values measured in the mammalian nerve are similar to those of the amphibian model, the relative permittivity of the laminae bring new information about the reactance and the corner frequency (frequency at peak reactance) of the peripheral nerve. The measured and estimated corner frequency are well within the range of most bioelectric signals, and are important to take into account when modeling the nerve and neural interfaces.

An experimental and numerical study of the microstructural and biomechanical properties of human peripheral nerve endoneurium for the design of tissue scaffolds.

Biomimetic design of scaffold architectures represents a promising strategy to enable the repair of tissue defects. Natural endoneurium extracellular matrix (eECM) exhibits a sophisticated microstructure and remarkable microenvironments conducive for guiding neurite regeneration. Therefore, the analysis of eECM is helpful to the design of bionic scaffold. Unfortunately, a fundamental lack of understanding of the microstructural characteristics and biomechanical properties of the human peripheral nerve eECM exists. In this study, we used microscopic computed tomography (micro-CT) to reconstruct a three-dimensional (3D) eECM model sourced from mixed nerves. The tensile strength and effective modulus of human fresh nerve fascicles were characterized experimentally. Permeability was calculated from a computational fluid dynamic (CFD) simulation of the 3D eECM model. Fluid flow of acellular nerve fascicles was tested experimentally to validate the permeability results obtained from CFD simulations. The key microstructural parameters, such as porosity is 35.5 ± 1.7%, tortuosity in endoneurium (X axis is 1.26 ± 0.028, Y axis is 1.26 ± 0.020 and Z axis is 1.17 ± 0.03, respectively), tortuosity in pore (X axis is 1.50 ± 0.09, Y axis is 1.44 ± 0.06 and Z axis is 1.13 ± 0.04, respectively), surface area-to-volume ratio (SAVR) is 0.165 ± 0.007 µm-1 and pore size is 11.8 ± 2.8 µm, respectively. These were characterized from the 3D eECM model and may exert different effects on the stiffness and permeability. The 3D microstructure of natural peripheral nerve eECM exhibits relatively lower permeability (3.10 m2 × 10-12 m2) than other soft tissues. These key microstructural and biomechanical parameters may play an important role in the design and fabrication of intraluminal guidance scaffolds to replace natural eECM. Our findings can aid the development of regenerative therapies and help improve scaffold design.

Optic nerve-associated connective tissue structures revisited: A histological study using human fetuses and adult cadavers.

Unlike the usual peripheral nerve, the optic nerve accompanies a thick "dural sheath," a thin "sheath of pia mater" (SPM), and multiple "septa," which divides the nerve fibers into fascicles. We collected specimens from 25 adult cadavers and 15 fetuses and revisited the histological architecture of the optic and oculomotor nerves. In the optic chiasma, the meningeal layer of the dura joins the pia to form a thick SPM, and the periosteum of the sphenoid is continuous with the dural sheath at the orbital exit of the bony optic canal. The septa appeared as a cluster of irregularly arrayed fibrous plates in the intracranial course near the chiasma. Thus, the septa were not derived from either the SPM or the dural sheath. In the orbit, the central artery of the retina accompanies collagenous fibers from the dural sheath and the SPM to provide the vascular sheath in the optic nerve. These connective tissue configurations were the same between adult and fetal specimens. At the optic disk, the dural sheath and SPM merged with the sclera, whereas the septa appeared to end at the lamina cribrosa. However, in fetuses without lamina cribrosa, the septa extend into the nerve fiber layer of the retina. The SPM and septa showed strong elastin immunoreactivity, in contrast to the absence of reactivity in the sheaths of the oculomotor nerve. Each S100 protein-positive Schwann sheath of the oculomotor nerve was surrounded by collagenous endoneurium. Glial fibrillary acidic protein-positive astrocytes showed a linear arrangement along the septa.

Gli1 Regulates the Postnatal Acquisition of Peripheral Nerve Architecture.

Peripheral nerves are organized into discrete compartments. Axons, Schwann cells (SCs), and endoneurial fibroblasts (EFs) reside within the endoneurium and are surrounded by the perineurium, a cellular sheath comprised of layers of perineurial glia (PNG). SC secretion of Desert Hedgehog (Dhh) regulates this organization. In Dhh nulls, the perineurium is deficient and the endoneurium is subdivided into small compartments termed minifascicles. Human Dhh mutations cause a neuropathy with similar defects. Here we examine the role of Gli1, a canonical transcriptional effector of hedgehog signaling, in regulating peripheral nerve organization in mice of both genders. We identify PNG, EFs, and pericytes as Gli1-expressing cells by genetic fate mapping. Although expression of Dhh by SCs and Gli1 in target cells is coordinately regulated with myelination, Gli1 expression unexpectedly persists in Dhh null EFs. Thus, Gli1 is expressed in EFs noncanonically (i.e., independent of hedgehog signaling). Gli1 and Dhh also have nonredundant activities. Unlike Dhh nulls, Gli1 nulls have a normal perineurium. Like Dhh nulls, Gli1 nulls form minifascicles, which we show likely arise from EFs. Thus, Dhh and Gli1 are independent signals: Gli1 is dispensable for perineurial development but functions cooperatively with Dhh to drive normal endoneurial development. During development, Gli1 also regulates endoneurial extracellular matrix production, nerve vascular organization, and has modest, nonautonomous effects on SC sorting and myelination of axons. Finally, in adult nerves, induced deletion of Gli1 is sufficient to drive minifascicle formation. Thus, Gli1 regulates the development and is required to maintain the endoneurial architecture of peripheral nerves.SIGNIFICANCE STATEMENT Peripheral nerves are organized into distinct cellular/ECM compartments: the epineurium, perineurium, and endoneurium. This organization, with its associated cellular constituents, is critical for the structural and metabolic support of nerves and their response to injury. Here, we show that Gli1, a transcription factor normally expressed downstream of hedgehog signaling, is required for the proper organization of the endoneurium but not the perineurium. Unexpectedly, Gli1 expression by endoneurial cells is independent of, and functions nonredundantly with, Schwann Cell-derived Desert Hedgehog in regulating peripheral nerve architecture. These results further delineate how peripheral nerves acquire their distinctive organization during normal development, and highlight mechanisms that may regulate their reorganization in pathologic settings, including peripheral neuropathies and nerve injury.

Neural invasion: a scenic trail for the nervous tumor and hidden therapeutic opportunity.

Neural invasion (NI) is the invasion of cancer cells into nerves, influencing the pathological characteristics of malignant tumors. NI promotes metastasis and is associated with reduced survival of affected patients. Although known for decades, its prognostic and therapeutic implications have not been not much appreciated due to the scattered information available on its clinical complications. The use of multiple nomenclatures to describe NI also generated confusions among researchers to understand this pathological process. Here, we discuss the multiple classifications of NI and review its clinical complications. Recent findings of the regulatory roles of nerves on tumor growth have fuelled research in this field, and there has been several attempts to molecularly define the NI interface and the cancer cells involved. Therefore, in this review, we discuss the large datasets available to characterize the cancer cells in NI and also discuss the roles of Schwann cells and macrophages participating in NI.

Biology of the human blood-nerve barrier in health and disease.

A highly regulated endoneurial microenvironment is required for normal axonal function in peripheral nerves and nerve roots, which structurally consist of an outer collagenous epineurium, inner perineurium consisting of multiple concentric layers of specialized epithelioid myofibroblasts that surround the innermost endoneurium, which consists of myelinated and unmyelinated axons embedded in a looser mesh of collagen fibers. Endoneurial homeostasis is achieved by tight junction-forming endoneurial microvessels that control ion, solute, water, nutrient, macromolecule and leukocyte influx and efflux between the bloodstream and endoneurium, and the innermost layers of the perineurium that control interstitial fluid component flux between the freely permeable epineurium and endoneurium. Strictly speaking, endoneurial microvascular endothelium should be considered the blood-nerve barrier (BNB) due to direct communication with circulating blood. The mammalian BNB is considered the second most restrictive vascular system after the blood-brain barrier (BBB) based on classic in situ permeability studies. Structural alterations in endoneurial microvessels or interactions with hematogenous leukocytes have been described in several human peripheral neuropathies; however major advances in BNB biology in health and disease have been limited over the past 50 years. Guided by transcriptome and proteome studies of normal and pathologic human peripheral nerves, purified primary and immortalized human endoneurial endothelial cells that form the BNB and leukocytes from patients with well-characterized peripheral neuropathies, validated by in situ or ex vivo protein expression studies, data are emerging on the molecular and functional characteristics of the human BNB in health and in specific peripheral neuropathies, as well as chronic neuropathic pain. These early advancements have the potential to not only increase our understanding of how the BNB works and adapts or fails to adapt to varying insult, but provide insights relevant to pathogenic leukocyte trafficking, with translational potential and specific therapeutic application for chronic peripheral neuropathies and neuropathic pain.

The capsule of human Meissner corpuscles: immunohistochemical evidence.

Meissner corpuscles are cutaneous mechanoreceptors that are usually located in the dermal papillae of human glabrous skin. Structurally, these sensory corpuscles consist of a mechanoreceptive sensory neuron surrounded by non-myelinating lamellar Schwann-like cells. Some authors have described a partially developed fibroblastic capsule of endoneurial or perineurial origin around Meissner corpuscles; however, others have noted that these structures are non-encapsulated. As there is continuity between the periaxonic cells forming the sensory corpuscles and the cells of the nerve trunks, we used immunohistochemistry to examine the expression of endoneurial (CD34 antigen) or perineurial [Glucose transporter 1 (Glut1)] markers in human cutaneous Meissner corpuscles. We also investigated the immunohistochemical patterns of nestin and vimentin (the main intermediate filaments of the cytoskeleton of endoneurial and perineurial cells, respectively) in Meissner corpuscles. The most important finding from this study was that CD34-positive cells formed a partial/complete capsule of endoneurial origin around most Meissner corpuscles, without signs of other perineurial Glut1-positive elements. However, the cytoskeletal proteins of the capsular CD34-positive cells did not include either nestin or vimentin, so the cytoskeletal composition of these cells remains to be established. Finally, the intensity of the immunoreactivity for CD34 in the capsule decreased with ageing, sometimes becoming completely absent in the oldest individuals. In conclusion, we report the first immunohistochemical evidence of the capsule of Meissner corpuscles in humans and demonstrate the endoneurial origin of the capsule.

In situ molecular characterization of endoneurial microvessels that form the blood-nerve barrier in normal human adult peripheral nerves.

The blood-nerve barrier (BNB) formed by tight junction-forming endoneurial microvessels located in the innermost compartment of peripheral nerves, and the perineurium serve to maintain the internal microenvironment required for normal signal transduction. The specific molecular components that define the normal adult human BNB are not fully known. Guided by data derived from the adult human BNB transcriptome, we evaluated the in situ expression of 25 junctional complex, transporter, cell membrane, and cytoskeletal proteins in four histologically normal adult sural nerves by indirect fluorescent immunohistochemistry to determine proteins specifically expressed by restrictive endoneurial microvascular endothelium. Using Ulex Europaeus Agglutinin-1 expression to detect endothelial cells, we ascertained that the selected proteins were uniformly expressed in ≥90% of endoneurial microvessels. P-glycoprotein (also known as adenosine triphosphate-binding cassette subfamily B member 1) and solute carrier family 1 member 1 demonstrated restricted expression by endoneurial endothelium only, with classic tight junction protein claudin-5 also expressed on fenestrated epineurial macrovessels, and vascular-specific adherens junction protein cadherin-5 also expressed by the perineurium. The expression profiles of the selected proteins provide significant insight into the molecular composition of normal adult peripheral nerves. Further work is required to elucidate the human adult BNB molecular signature in order to better understand its development and devise strategies to restore function in peripheral neuropathies.

Factors Within the Endoneurial Microenvironment Act to Suppress Tumorigenesis of MPNST.

Background: Deciphering avenues to adequately control malignancies in the peripheral nerve will reduce the need for current, largely-ineffective, standards of care which includes the use of invasive, nerve-damaging, resection surgery. By avoiding the need for en bloc resection surgery, the likelihood of retained function or efficient nerve regeneration following the control of tumor growth is greater, which has several implications for long-term health and well-being of cancer survivors. Nerve tumors can arise as malignant peripheral nerve sheath tumors (MPNST) that result in a highly-aggressive form of soft tissue sarcoma. Although the precise cause of MPNST remains unknown, studies suggest that dysregulation of Schwann cells, mediated by the microenvironment, plays a key role in tumor progression. This study aimed to further characterize the role of local microenvironment on tumor progression, with an emphasis on identifying factors within tumor suppressive environments that have potential for therapeutic application. Methods: We created GFP-tagged adult induced tumorigenic Schwann cell lines (iSCs) and transplanted them into various in vivo microenvironments. We used immunohistochemistry to document the response of iSCs and performed proteomics analysis to identify local factors that might modulate divergent iSC behaviors. Results: Following transplant into the skin, spinal cord or epineurial compartment of the nerve, iSCs formed tumors closely resembling MPNST. In contrast, transplantation into the endoneurial compartment of the nerve significantly suppressed iSC proliferation. Proteomics analysis revealed a battery of factors enriched within the endoneurial compartment, of which one growth factor of interest, ciliary neurotrophic factor (CNTF) was capable of preventing iSCs proliferation in vitro. Conclusions: This dataset describes a novel approach for identifying biologically relevant therapeutic targets, such as CNTF, and highlights the complex relationship that tumor cells have with their local microenvironment. This study has significant implications for the development of future therapeutic strategies to fight MPNSTs, and, consequently, improve peripheral nerve regeneration and nerve function.

A novel marker for identifying and studying the membranes, barriers, and compartments surrounding peripheral nerves microscopically.

Recent anatomical discoveries indicate the importance of identifying membranes and compartments surrounding peripheral nerves into which local anesthetic agents can be injected and continuous nerve block catheters placed during regional anesthetic procedures. However, current markers used in anatomical studies have multiple drawbacks, specifically extravasation into noninjected locations, which can result in inadequate treatment. We studied a readily-available new marker, heparinized blood solution (HBS), which is easy to identify by microscopy and can remain in the nerve compartment into which it is deposited without distorting the tissue. We collected blood from 22 patients and prepared it as HBS. This was then injected into four fresh cadavers as in routine clinical practice for ultrasound-guided nerve blocks to form a so-called "doughnut" by "hydro-dissecting" at 32 sites. All samples, including nerves and neighboring tissues, were then prepared and examined by light microscopy. Although no deliberate intraneural injection was attempted, the marker was identified inside all the nerve compartments except the fascicles. Apart from leaking through the needle entry site in some instances, there was no extravasation of the HBS into neighboring nerve compartments in either direction. The tissues were not distorted and the erythrocytes did not form a thrombus. Nerve membranes and compartments could be clearly identified with routine staining. This technique enabled us to study the longitudinal and circumferential spread in all nerve compartments and to collect data for better interpretation of factors influencing an anesthetic nerve block and situations in which complications could possibly arise. HBS seemed superior to other markers because it did not leave the compartments into which it had been injected, did not distort the tissue, and was easily visible under the light microscope. Clin. Anat., 31:1050-1057, 2018. © 2018 Wiley Periodicals, Inc.

Endoneurial-CD34 positive cells define an intermediate layer in human digital Pacinian corpuscles.

The endoneurial and/or perineurial origin of the outer core; i.e. the concentric and continuous lamellae located outside the complex formed by the axon and the Schwann-related cells, in human Pacinian corpuscles is still debated. Here we used immunohistochemistry coupled with a battery of antibodies to investigate the expression of perineurial (Glucose transporter 1 and epithelial membrane antigen) or endoneurial (CD34 antigen) markers in human digital Pacinian corpuscles. CD34 immunoreactivity was restricted to one layer immediately outside the inner core, whereas the proper outer core displayed antigens typical of the perineurial cells. These results demonstrate an intermediate endoneurial layer that divides the Pacinian corpuscles into two distinct compartments: the avascular inner neural compartment (formed by the axon and the Schwann-related cells that form the inner core), and the outer non-neural compartment (formed by the outer core). The functional relevance of these findings, if any, remains to be clarified.

Hedgehog Pathway-Mediated Vascular Alterations Following Trigeminal Nerve Injury.

Whereas neurovascular interactions in spinal neuropathic pain models have been well characterized, little attention has been given to such neurovascular interactions in orofacial neuropathic pain models. This study investigated in male Sprague-Dawley rats the vascular changes following chronic constriction injury (CCI) of the infraorbital nerve (IoN), a broadly validated preclinical model of orofacial neuropathic pain. Following IoN-CCI, an early downregulation of tight junction proteins Claudin-1 and Claudin-5 was observed within the endoneurium and perineurium, associated with increased local accumulation of sodium fluorescein (NaFlu) within the IoN parenchyma, as compared with sham animals. These events were evidence of local blood-nerve barrier disruption and increased vascular permeability. A significant upregulation of immunocytes (CD3, CD11b) and innate immunity (TLR2, TLR4) mRNA markers was also observed, suggestive of increased local inflammation. Finally, a significant downregulation of Hedgehog pathway readouts Patched-1 and Gli-1 was observed within the IoN after CCI and local injections of cyclopamine, a Hedgehog pathway inhibitor, replicated in naïve rats the molecular, vascular, and behavioral changes observed following IoN-CCI. These results suggest a major role of Hedgehog pathway inhibition in mediating local increased endoneurial and perineurial vascular permeability following trigeminal nerve injury, thus facilitating immunocytes infiltration, neuroinflammation development, and neuropathic pain-like aversive behavior.

Pathology of Perineural Spread.

The perineural space is a compartment located between the nerve axons, supporting cells and tissues, and the epineural fibrous sheath. Tumor cells invade this space in response to a complex interplay of trophic factors in the local microenviroment. This attraction of tumor cells to nerves is referred to as neurotropism. The perineural space provides a conduit for tumor spread beyond the primary site of tumor occurrence. Perineural tumor growth is of two types: perineural invasion, affecting small unnamed nerves; and perineural spread, affecting larger, named nerves and presenting with clinical symptoms related to the involved nerve. Both forms of perineural tumor growth represent an adverse prognostic feature and are an essential element of the histopathologic reporting of malignancies of the head and neck region. Perineural spread is associated with decreased overall survival. Endoneurial invasion frequently accompanies perineural spread. The epineurium is more resistant to invasion and represents an important barrier to tumor spread. Immunohistochemical stains such as broad-spectrum keratin can aid in defining the proximal extent of perineural tumor spread.

The blood-nerve barrier: Research progress / 第二军医大学学报

The blood-nerve barrier (BNB) is a barrier system similar to blood-brain barrier (BBB), which can selectively limits the interchange of materials between the blood and the peripheral nervous system. It has been reported that the change of BNB permeability occurs in nerve lesions, and further research on BNB is of great significance for the treatment of those diseases. This paper mainly introduced the structure and function of BNB, progress of BNB cellular biology, changes and significance of BNB under pathological conditions, and the possible association between BNB and drug effects.

Neurorrhaphy techniques: comparative stereological and experimental axonal study / Técnicas de neurorrafia: estudio experimental estereológico axonal comparativo

There is a great variety of injuries that affect peripheral nerves derived from acquired or congenital degenerative diseases affecting the central nervous system that cause loss of sensorimotor functions. The objective of this work was to perform an end-to-side or side-to-side experimental axonal stereological study in order to compare volume density of axons, endouneuro and myelin sheath (and muscle mass) in peroneal and tibial nerves, with anastomosis contact from 0.25 cm to 0.50 cm. After approval of the Ethics Committe, 20 male Wistar rats were divided into four groups of five rats each (G1= end-to-side neurorrhaphy; G2= side-to-side neurorrhaphy of 0.25 cm; G3= side-to-side neurorrhaphy of 0 cm and G4= Control of normality). After 180 days, fragments of peroneal and tibial nerves were collected for histological and stereological study. In comparative stereological experimental study between neurorraphies, the volume density of axons, myelin sheath of tibial and fibular nerves, as well as the post-surgical muscle mass, remains the same in end-to-side and side-to-side neurorraphies, regardless of contact area of anastomosis. It can be inferred, as surgical repair options, both end-to-side neurorrhaphy to recover and prevents atrophy of the endplate as side-to-side neurorraphy that is independent of the distance between the nerve stumps.

Gran variedad de lesiones atingen a los nervios periféricos, derivadas de enfermedades adquiridas o degenerativas congénitas que afectan la parte central del sistema nervioso y que ocasionan pérdida de funciones sensoriomotoras. El objetivo de ese trabajo fue realizar un estudio experimental estereológico axonal post neurorrafias termino-lateral o latero-lateral para comparar densidad de volumen de axones, endoneuro y vaina de mielina (así como masa muscular) en nervios fibular y tibial, con unión de contacto entre 0,25 cm y 0,50 cm. Tras la aprobación del comité de ética, fueran utilizados 20 ratones machos de la raza Wistar divididos en cuatro grupos de 5 ratones cada uno (G1= Neurorrafia término lateral; G2= Neurorrafia latero lateral de 0,25 cm; G3= Neurorrafia latero lateral de 0,50 cm y G4= Control). Posteriormente, fragmentos de los nervios tibiales y fibulares fueron procesados para estudios histológicos y estereológicos. En el estudio experimental estereológico comparativo entre neurorrafias termino-lateral y latero-lateral, la densidad de volumen de axones, endoneuro y vaina de mielina de nervios tibial y fibular y también la masa muscular post quirúrgica se mantuvo equitativa, independientemente del área de unión de contacto. Podemos inferir como opciones de reparación quirúrgica, que el tratamiento de la neurorrafia termino-lateral y latero-lateral previnen la atrofia de placa motora, independiente de la distancia entre los muñones nerviosos.

Bridging long gap peripheral nerve injury using skeletal muscle-derived multipotent stem cells.

Long gap peripheral nerve injuries usually reulting in life-changing problems for patients. Skeletal muscle derived-multipotent stem cells (Sk-MSCs) can differentiate into Schwann and perineurial/endoneurial cells, vascular relating pericytes, and endothelial and smooth muscle cells in the damaged peripheral nerve niche. Application of the Sk-MSCs in the bridging conduit for repairing long nerve gap injury resulted favorable axonal regeneration, which showing superior effects than gold standard therapy--healthy nerve autograft. This means that it does not need to sacrifice of healthy nerves or loss of related functions for repairing peripheral nerve injury.

Electron microscopy of human peripheral nerves of clinical relevance to the practice of nerve blocks. A structural and ultrastructural review based on original experimental and laboratory data.

AIM: The goal is to describe the ultrastructure of normal human peripheral nerves, and to highlight key aspects that are relevant to the practice of peripheral nerve block anaesthesia. METHOD: Using samples of sciatic nerve obtained from patients, and dural sac, nerve root cuff and brachial plexus dissected from fresh human cadavers, an analysis of the structure of peripheral nerve axons and distribution of fascicles and topographic composition of the layers that cover the nerve is presented. Myelinated and unmyelinated axons, fascicles, epineurium, perineurium and endoneurium obtained from patients and fresh cadavers were studied by light microscopy using immunohistochemical techniques, and transmission and scanning electron microscopy. Structure of perineurium and intrafascicular capillaries, and its implications in blood-nerve barrier were revised. RESULTS: Each of the anatomical elements is analyzed individually with regard to its relevance to clinical practice to regional anaesthesia. CONCLUSIONS: Routine practice of regional anaesthetic techniques and ultrasound identification of nerve structures has led to conceptions, which repercussions may be relevant in future applications of these techniques. In this regard, the ultrastructural and histological perspective accomplished through findings of this study aims at enlightening arising questions within the field of regional anaesthesia.

Ankle neurothekeoma: a case report.

Neurothekeoma is a rare, benign, cutaneous tumor of nerve sheath origin that is also termed benign nerve sheath myxoma. This tumor is usually asymptomatic and grows slowly. Neurothekeoma is typically found in young adults and seldom occurs in children. It is most commonly located in the head, neck, and upper extremity and extremely rarely found in the lower leg. We report a rare case of ankle neurothekeoma in a child, with a review of the related published data.

ULTRASTRUCTURE OF PERINEURIAL CELLS AND FIBROUS LONG-SPACING BODIES (FLS) IN ENDONEURIUM OF NORMAL HUMAN PERIPHERAL NERVE / 解剖学报

The perineurial cells of the small nerve branch of the normal human abdominal wall are observed with electron microscope. The fibrous long-spacing bodies (FLS) are found within the interstitial substance of the endoneurium. 1. 2-5 layers of the perineurial cells surround the nerve fasciculus. The perineurial cells are squamous in shape and the cytoplasm contains microfilaments and pinocytotic vesicles. Each perineurial cell has an obvious basement membrane on its basal surface but the fibroblasts, whatever situated in the endoneurium or on the outer surface of the perineurium, has no basement membrane. Numerous desmosome and some gap junctions between the close attached perineurial cells are demostrated. The collagen fibrils between perineurial cells can be often shown. FLS bodies and collagen fibrils about 45 nm in diameter in the interstitial substance of endoneurium inside perineurial cells are demonstrated. In the connective tissue surrounding the outside of perineurial cells, the collagen fibrils of 80 nm in diameter can be seen, but no FLS bodies present there. 2. FLS bodies in the endoneurial matrix can be demostrated. Most of them closely associated with the basement membrane of the Schwann cells surrounding the unmyelinated nerves but no FLS bodies are found associate with those of the myelinated nerves. A few FLS bodies do not relate to basement membrane and they are invested only with the collagen fibrils. In the longitudinal sections, most of FLS bodies are in spindle shape of various sizes, their longitudinal axes parallel to that of the adjoining collagen fibrils. Sometimes the FLS bodies continue with the collagen fibrils are found. Occasionally, FLS body like a bridge locate between two Schwann cells and its dark bands continue to the basement membrane of the Schwann cells. Two or three FLS bodies may fuse together but their cross bands do not registered at the same level. In the oblique sections, FLS bodies are nearly rectangular in shape, with the cross bands shown, and their appearance do not show greaty difference from those in longitudinal sections. The periodicity of FLS bodies is about 133nm in length; the dark band in it is about 53 nm, which is made of the dense granular substance; the light band is about 80 nm, which is made of a network with approximated parallel microfilaments. There are no further crossstriated structures within the periods. Some problems, such as the role of the perineurial cells, the relationship of FLS bodies with basement membrane, are briefly discussed.