Transplantation of neural stem cells encapsulated in hydrogels improve functional recovery in a cauda equina lesion model.

This study explored the therapeutic effects of transplantation of neural stem cells (NSCs) encapsulated in hydrogels in a cauda equina lesion model. NSCs were isolated from neonatal dorsal root ganglion (nDRG) and cultured in three-dimensional porous hydrogel scaffolds. Immunohistochemistry, transmission electron microscopy and TUNEL assay were performed to detect the differentiation capability, ultrastructural and pathological changes, and apoptosis of NSCs. Furthermore, the functional recovery of sensorimotor reflexes was determined using the tail-flick test. NSCs derived from DRG were able to proliferate to form neurospheres and mainly differentiate into oligodendrocytes in the three-dimensional hydrogel culture system. After transplantation of NSCs encapsulated in hydrogels, NSCs differentiated into oligodendrocytes, neurons or astrocytes in vivo. Moreover, NSCs engrafted on the hydrogels decreased apoptosis and alleviated the ultrastructural and pathological changes of injured cauda equina. Behavioral analysis showed that transplanted hydrogel-encapsulated NSCs decreased the tail-flick latency and showed a neuroprotective role on injured cauda equina. Our results indicate transplantation of hydrogel-encapsulated NSCs promotes stem cell differentiation into oligodendrocytes, neurons or astrocytes and contributes to the functional recovery of injured cauda equina, suggesting that NSCs encapsulated in hydrogels may be applied for the treatment of cauda equina injury.

The fine structure of ependymomas.

Electron microscopy is a useful diagnostic technique in order to confirm or establish a definitive diagnosis in brain tumors that may have an atypical histological pattern, which requires a concrete diagnosis. In ependymomas, electron microscopy reveals morphological characters that have a pathognomonic diagnostic value, therefore allowing a definitive diagnosis. The main fine structural criteria of ependymomas consist of the numerous microvilli and cilia, which are incorporated in the cell body or extended freely in the intracellular space; the centriole or blepharoplast, which is located in the basis of the cilia; the large number of the fragmented microtubules in the perikaryon and the cellular processes (any small cellular projection into the neutrophil or intracellular space); the junctional apparatus between the cells, such as zonula adherens, zonula occludens and puncta adherentia; the basement membrane-like structure, seen in papillary ependymomas and ependymomas of the filum terminale; and the elongated cells in the loose intracellular space, commonly seen in myxopapillary ependymomas.

Ependymal cells variations in the central canal of the rat spinal cord filum terminale: an ultrastructural investigation.

OBJECTIVE: The ependymal cells, considered today as an active participant in neuroendocrine functions, were investigated by electron microscopy in the central canal of the lowest spinal cord, the filum terminale (FT), in adult rats. In this area of the spinal cord, the central canal is covered by a heterogeneous population of ependymal cells. The aim of the present work was to compare the regional features of the ependymal cells in two different parts of the FT with a special regard to their ultrastructure. METHODS: Two parts of the FT were selected for the ultrastructural observations: the rostral (rFT) and the caudal (cFT) ones. The rTF was removed at the level of the immediate continuation of the conus medullaris, while the cFT 30 mm further caudally. After formaldehyde fixation, the spinal cord was removed and cut into small blocks for electron microscopic processing. The material was embedded into durcupan, contrasted with uranyl acetate, lead citrate as well as osmium tetroxide, and investigated under JEOL 1200 EX electron microscope. RESULTS: In the rFT, the ependymal lining is pseudostratified and one-layered in the cFT, whereas the shape of the ependymal cells may vary from cuboidal to flatten in the rostro-caudal direction. The basal membrane of many ependymal cells possesses deep invaginations, so called "filum terminale labyrinths". Many neuronal processes occur in the pericanalicular neuropil. In contrast to the rFT, the cFT is less rich in the neuropil particles. Some of the ependymal cells concurrently reach both the intracanalicular and extracanalicular cerebrospinal fluid (CSF), thus they may represent a new variant of the ependymal cells designated as "bridge cells of the FT". CONCLUSIONS: The present data indicate that the FT ependymal cells exhibit clear differences in anatomy as well as ultrastructure that may reflect their distinct functional activity. Therefore, observations presented here may serve for the better understanding of the physiological role of the individual ependymal areas in this special portion of the rat spinal cord.

SEM study on filum terminale with tethered cord syndrome.

OBJECTIVE: To improve the understanding in pathology and provide steady proof for diagnosis and treatment of tethered cord syndrome (TCS), the ultrastructure of filum terminale (FT) with TCS will be researched, respectively. METHODS: Thirty-one fila were sectioned and divided into two groups according to diameter. Twenty-two fila thicker than 2 mm were placed into group 1; nine no thicker than 2 mm were placed into group 2. Their transverse and longitudinal sections were respectively submitted for scanning electron microscopy analysis. RESULTS: For the FTs with TCS, ultrastructural analysis confirmed the presence of abundant collagen bundles and adipocytes, sparse or invisible elastic and reticular fibers inside the FT, but the latter two fibers were still visible in the relative normal areas of FT; some abnormalities, such as thickening, distortion, adhesion or fusion to piece, relatively dense and disorderly arrangement at a different degree, were quite common for collagen fiber. Some areas looked blurry, and some crystallization appeared occasionally on their surface. For the FTs with TFTS, those changes as mentioned above were still exhibited, but slightly relatively. All the changes mentioned inside all the FTs may exist alone or concomitantly, rarely simultaneously. Moreover, they can be often seen focally or diffusely occasionally. CONCLUSIONS: Low elasticity resulting from the destruction of the three-dimensional structure of FT is involved in TCS. Early FT severing is a treatment of choice no matter whether its appearance looks normal.

Meningioma de cels claras. Una rara variante de meningioma / Clear cell meningioma. A rare variant of meningioma

Presentamos en nuestro trabajo, los hallazgos morfológicos e inmunohistoquímicos de carácter diagnóstico observados en un meningioma de células claras localizado a nivel de la cauda equina en un paciente de 25 años. El tumor mostró un patrón morfológico de predominio nodular en el que destacaban las células de citoplasma claro, positivas para la tinción de PAS. El hallazgo de áreas de aspecto meningoteliomatoso dentro del mismo tumor así como la inmunohistoquímica (positividad de las células tumorales para vimentina y EMA y negatividad para citoqueratinas, CD10, HMB-45 y proteína glial fibrilar ácida) permitió establecer un diagnóstico diferencial con otras neoplasias principalmente con las metástasis de carcinoma renal. De igual modo se comentan con brevedad las características de esta variante de meningioma de grado intermedio de malignidad (meningioma grado ii de la OMS)(AU)

The morphological and immunohistochemical findings of a clear cell meningioma found in the cauda equina of a 25 year old patient are reported. The tumour was predominately nodular with a marked presence of cells with clear cytoplasm which stained positively for PAS. The presence of meningoteliomatous areas in the tumour, together with the immunohistochemistry of the tumour cells (positivity for vimentin and EMA and negativity for cytokeratins, CD10, HMB45 and PGFA) were the diagnostic features that differentiated the tumour from other possible diagnoses, principally metastases from a renal carcinoma. The characteristics of this type of meningioma, which has an intermediate grade of malignancy (WHO grade ii meningioma) are discussed(AU)

Syncytial cytoplasmic anastomoses between neurites in caudal mesenteric ganglion cells in adult cats.

The fact that most published data on syncytial cytoplasmic anastomoses are based on the autonomic nervous system in the early postnatal period of development, when many nerve fibers are poorly ensheathed by glia or have no glial sheaths at all, has led to the assumption that these anastomoses do not exist in adults because of the significant development of the glia and glial insulation of individual neurites from each other. We tested this assumption using electron microscopic studies of the caudal mesenteric ganglion in adult cats. A high level of glial ensheathing of neurites was observed. However, syncytial pores were seen between contacting neurites lacking glial sheaths in almost every specimen. This is the first report describing axodendritic synapses with perforations in the presynaptic zone outside the synaptic specializations in the autonomic nervous system. It is suggested that although syncytial cytoplasmic connections are seen in adult animals, they do not contradict the neuron theory.

[Syncytial cytoplasmic anastomoses between the neurites of caudal mesenteric ganglion cells in adult cats].

Since the majority of the published data on syncytial cytoplasmic anastomoses relate to the autonomic nervous system in the early postnatal period of development, when many nerve fibers are still poorly covered by glia or have no glial sheaths at all, it was suggested that such anastomoses were not present in adults due to the significant development of glia separating individual neurites from each other. To check this assumption, we have performed an electron microscopic study of the adult cat dorsal caudal mesenteric ganglion. The cell neurites were found to be frequently covered by glial sheaths. However, almost in every sample, the syncytial pores were detected between the contacting neurites lacking glial covering layers. Sometimes serial syncytially connected neurites were seen. Axo-dendritic synapses with presynaptic perforations outside the synaptic specializations were described in the autonomic nervous system for the first time. These observations therefore provide evidence of syncytial cytoplasm connections in normal adult animals, however this does not reject the neuronal doctrine.

Long-distance axonal regeneration in the filum terminale of adult rats is regulated by ependymal cells.

Studies of regeneration of transected adult central nervous system (CNS) axons are difficult due to lack of appropriate in vivo models. In adult rats, we described filum terminale (FT), a caudal slender extension of the sacral spinal cord and an integral part of the central nervous system (CNS), to use it as a model of spinal cord injury. FT is more than 3 cm long, encompasses a central canal lined with ependymal cells surrounded by a narrow band of axons interspersed with oligodendrocytes and astrocytes but not neurons. Two weeks after the crush of FT, histological, ultrastructural, and axonal tracing studies revealed long distance descending axonal regeneration uniquely in close proximity of the ependymal cells of the central canal. Ependymal cells extended basal processes to form channels encompassing axons apparently regenerating at a rate of more than 2 mm a day. Remarkable increase of axonal sprouting was observed in the sacral spinal cord of Long Evans Shaker (LES) rats with crushed FT. FT offers an excellent model to study mechanisms of axonal regeneration regulated by ependymal cells in the adult CNS.

Ultrastructural study of the filum terminale and its elastic fibers.

OBJECTIVE: The filum terminale (FT) is a fibrovascular band involved in the pathophysiology of tethered cord syndrome (TCS). Its morphological and ultrastructural properties remain largely unknown even though they are thought to play a role in the generation of TCS in adult patients with normal level conus medullaris. MATERIALS AND METHODS: Twenty fresh adult human cadavers had their fila measured and removed. Transversal and longitudinal sections of the proximal, middle, and distal thirds of FT were submitted to light microscopy analysis with four different techniques. Five fila were selected for longitudinal and transversal scanning electron microscopy analysis. RESULTS: The bulk of the FT is composed of 5- to 20-microm thick longitudinal bundles of Type 1 collagen separated by 3- to 10-microm intervals, although capillaries and other elements may be present. A delicate (0.05-1.5 microm) meshwork of predominantly Type 3 collagen transversal fibers connects these bundles. Abundant longitudinally oriented elastic and elaunin fibers are found inside collagen bundles. A complex tridimensional structure is evidenced on electron microscopy. CONCLUSION: The longitudinal arrangement of collagen bundles and the impressive amount of elastic and elaunin fibers should elicit considerable elastic properties to the FT. An altered elasticity mechanism has been proposed for TCS; further studies are needed with TCS patients to define whether the collagen structure, Type 1/Type 3 proportion, or elastic fiber content are altered, which could lead to new histopathological definitions of TCS, helping neurosurgeons in the difficult management of TCS patients with normal level conus medullaris.

The nerve root entry zone is highly vulnerable to intrathecal tetracaine in rabbits.

It has been speculated that the nerve root entry zone in the spinal cord, known as the Obersteiner-Redlich zone, may be more sensitive to large concentrations of local anesthetics administered intrathecally. However, there has been no morphological evidence for this. In the present study, we examined morphological changes of nerve fibers at the nerve root entry zone after administration of intrathecal tetracaine in rabbits. Rabbits were assigned to 4 groups (n = 6 in each) and received intrathecal 0.3 mL saline (control), or 1%, 2%, or 4% tetracaine. Neurological and histopathological assessments were performed 1 wk after the administration. Tetracaine 1% selectively injured the myelin sheaths made by oligodendrocytes at the nerve root entry zones of both ventral and dorsal roots, although neurological dysfunction could not be detected. With tetracaine 2% and 4%, histopathological damage extended to the dorsal funiculus, distal part of roots, and cauda equina and neurological dysfunction became apparent. These results demonstrate that the myelin sheaths made by oligodendrocytes at the nerve root entry zone are highly vulnerable to large concentrations of tetracaine given intrathecally.

The caudal end of the rat spinal cord: transformation to and ultrastructure of the filum terminale.

Contrary to the current belief, the spinal cord of the rat does not terminate with the conus terminalis (CT), but its basic components (central canal, gray matter, white matter) continue in the filum terminale (FT). Proceeding caudally in the conus terminalis, first the motoneuron cell column discontinues in the ventral horn. More caudally the dorsal horns separate from the intermediate zone, and discontinue. The ensuing filum terminale consists of the slit-like central canal lined by ciliated ependymal cells, the periventricular gray matter and the peripheral white matter. Uniform small size neurons and glial cells populate the gray matter. Ultrastructural analysis revealed various types of axodendritic and axosomatic synapses as well as fine unmyelinated axons. The white matter consists mainly of myelinated nerve fibers. The neuronal components of the filum terminale, if they occur also in the human spinal cord, should be involved in the diagnosis and treatment of various diseases, e.g. tethered spinal cord syndrome, vascular malformations and disraphysm.

Lumbar intrathecal ligaments.

A meticulous examination was performed on 56 vertebral columns from cadavers between 64 and 89 years of age. Identification of all contents within the dural sac was completed; however, the main focus was the cauda equina and lumbar region. In addition to scope dissection, radiographs and histological preparations were used to identify structures, tissue types, and any possible pathology. Discrete intrathecal ligamentous bands were observed in all cadavers examined. They were found randomly binding the dorsal nerve roots of the cauda equina to the dura. Occasional binding of the ventral nerve roots to the dorsal roots was observed. Histological examination demonstrated a dense collagen ligament varying between 0.13 and 0.35 microm in thickness and from 3 mm to 3.5 cm in length. The average number of ligaments found per cadaver was 18. These ligaments displayed a broad base attachment to the nerve root or dura of approximately 3 mm. Looping of the nerve roots associated with these ligaments was seen in one cadaver with a burst fracture. Electron microscopic studies of these ligaments demonstrated similarities to denticulate ligaments. It is suggested that the intrathecal ligaments represent remnants from fetal development of the denticulate ligaments.

Human immunoglobulin ameliorates rat experimental autoimmune neuritis.

Human immunoglobulin is an effective treatment for Guillain-Barré syndrome, although the mechanism of action is not understood. We have investigated the effect of human immunoglobulin in an animal model of Guillain-Barré syndrome, namely experimental autoimmune neuritis (EAN), induced in Lewis rats by immunization with bovine spinal root myelin. Human immunoglobulin administered intraperitoneally at the time of onset of disease accelerated the rate of recovery from EAN. This improvement was associated with a reduction in the titre of anti-rat myelin antibodies and may be due to earlier remyelination of demyelinated nerve fibres. This model may facilitate further investigation of the mechanism of therapeutic action of immunoglobulin in inflammatory neuropathy.

Postlaminectomy adhesion of the cauda equina. Changes of postoperative vascular permeability of the equina in rats.

STUDY DESIGN: The authors evaluated the vascular permeability changes of the cauda equina after lumbar laminectomy in rats. OBJECTIVES: To clarify the early vascular responses in postlaminectomy adhesive arachnoiditis. SUMMARY OF BACKGROUND DATA: Laminectomy-induced cauda equina adhesion has been visualized by postoperative serial magnetic resonance imaging in humans. In laminectomized rats, fibrinous exudation was apparent among the adhered cauda equina. To date, there has been no report of substantial changes in vascular permeability in the cauda equina after lumbar laminectomy. METHODS: Wistar rats laminectomized from L5-L6 were used for four studies; 1) Evans blue albumin tracer study; 2) horseradish peroxidase tracer study; 3) lanthanum tracer study; and 4) fluoroscein isothiocyanate-dextran (molecular weights: 20K, 70K, and 150K) tracer study. Untreated rats were used as controls. RESULTS: 1) In the laminectomized (L5-L6) area, the cauda equina tended to conglomerate from 3 hours after surgery; this was relatively resolved by 6 weeks. Extravascular leakage of Evans blue albumin in the cauda equina appeared at 3 hours after surgery and reached a plateau at 24 hours; it mostly disappeared by 6 weeks. At 24 hours after surgery, the extent of Evans blue albumin extravasation was seen in one or more levels adjacent to the laminectomized area. Evans blue albumin leakage and cauda equina adhesion started to appear in nearly a same phase after laminectomy, followed by a plateau of vascular permeability facilitating complete cauda equina adhesion by 24 hours after surgery. The restoration of Evans blue albumin leakage was noted 1 week after surgery, and tended to precede recovery of the cauda equina adhesion; 2) in the laminectomy group, Horseradish peroxidase penetrated from the lumen to the extracellular space beyond the basal laminae of the endothelial cells. Numerous horseradish peroxidase-labeled vesicles in the endothelial cells were found; 3) There was a significant increase in lanthanum distribution in the endothelial cytoplasm at the laminectomized levels. Lanthanum filled the interendothelial clefts beyond the tight junction, but did not penetrate through the perivascular basal laminae; 4) Fluoroscein isothiocyanate-dextran (20K, 70K, 150K) permeability increased in the laminectomy group, but there was no difference in extravasation of fluoroscein isothiocyanate-dextran, irrespective of the molecular weight. CONCLUSION: Laminectomy consistently induced an increase in vascular permeability in the cauda equina, an increase of vesicular transport in the endothelial cell, and opening of the tight junction early after laminectomy, suggesting breakdown of the blood nerve barrier in the cauda equina. The accelerated permeability may enhance cauda equina adhesion.

The ventriculus terminalis and filum terminale of the human spinal cord.

Serial sections of the conus medullaris and the filum terminale of 23 randomly selected human spinal cords were studied by light and electron microscopy, and following immunoperoxidase staining for glial fibrillary acidic protein (GFAP), vimentin, neuron-specific enolase (NSE), amyloid beta protein, and S-100 protein. The intradural portion of the filum contains bundles of GFAP-positive glial fibers, scattered silver- and NSE-positive neurons, segments of peripheral nerve, blood vessels, fibrous connective tissue, and fat. Glial cell clusters varying from five to 100 cell layers thick at times constitute the bulk of the filum. The periependymal glial cells possess moderate amounts of eosinophilic cytoplasm and relatively uniform round to ovoid nuclei containing evenly distributed chromatin. They are distributed diffusely with no specific pattern of organization, although some of them showed a tendency to form acinar structures. A minority of the glial cells showed GFAP immunoreactivity, and some were immunoreactive for vimentin. Electron microscopy demonstrated the presence of periependymal cells showing cilia, microvilli, and the formation of intercellular junctional complexes, as well as cells containing bundles of glial filaments within the cytoplasm. Degenerated NSE-positive neurons and degenerated neurites resembling neuritic plaques were also demonstrated. However, immunoperoxidase staining for amyloid beta protein was negative in these structures. Thus, the filum terminale is endowed with an abundance of glial cells and neurons and is not simply a fibrovascular tag. Periependymal glial cells in the filum terminale should not be mistaken for neoplasm. The presence of neuropil with profuse astroglial and neuronal components within the filum terminale suggests a possible functional role for these structures.

Impairment of vertebral canal nervous structures after intrathecal prophylaxis in non-Hodgkin's lymphomas.

Neuropathological analysis of spinal cord and spinal roots as well as spinal leptomeninges after intrathecal methotrexate (MTX) therapy was performed in 44 cases of non-Hodgkin's lymphomas of high malignancy. It was showed that MTX applied according to the program applied as a prophylaxis against lymphomatous infiltrations in the central nervous system, caused demyelination of spinal roots and fibrosis of leptomeninges and their blood vessels. However, it does not affect spinal cord structures. Described morphological changes remained clinically mute, therefore they do not seem counterindicate prophylactic intrathecal MTX application.

Giant gangliocytic paraganglioma of the filum terminale. Case report.

The clinical and pathological features of a giant cauda equina paraganglioma arising from the intradural filum terminale is described. Scattered mature large neurons characterized the tumor as a gangliocytic paraganglioma. Histologically, these neoplasms have considerable similarity with ependymoma and the diagnosis can be easily missed unless special techniques are employed.

Microtubular aggregates within rough endoplasmic reticulum in myxopapillary ependymoma of the filum terminale.

Aggregates of microtubules with-in rough endoplasmic reticulum were found in many neoplastic cells of three cases of myxopapillary ependymoma of the filum terminale studied ultrastructurally. The cytoplasm and cellular processes of some neoplastic cells were distended by the aggregates. In general the involved rough endoplasmic reticulum contained three to six microtubules, but some enclosed more than 10 microtubules. The enclosed microtubules were straight parallel hollow cylindrical structures with fuzzy coats. They had an inner diameter of 12 to 15 nm, an outer diameter of 30 to 35 nm, and a center-to-center distance of 50 to 62 nm. The involved rough endoplasmic reticulum often showed various degrees of loss of surface ribosomes and some appeared totally degranulated. Vacuolar degeneration of involved rough endoplasmic reticulum with fragmentation and disintegration of the enclosed microtubules was frequent. Direct relationship of the enclosed microtubules to the cytoplasmic microtubules and ciliary formation was not found. This unusual microtubular aggregate has not been described in other types of ependymoma, or in other brain tumors. They may represent a characteristic ultrastructural feature of myxopapillary ependymoma.