The role of the notochord in vertebral column formation

Prevalence of incorrect posture among school adolescents after the COVID-19 pandemic: a large population-based scoliosis screening in China

BACKGROUND

The spinal health of teenagers is adversely affected by the effects of COVID-19, and large-scale scoliosis screening for teenagers after the pandemic has not been reported. This study aimed to explore the prevalence of incorrect posture among Chinese adolescents after the COVID-19 pandemic.

METHODS

This was a large-scale cross-sectional study based on school scoliosis screening. Each student underwent visual inspection, Adam's forward bending test, and trunk rotation angle measurement. A scoliometer was used for posture assessment. The participants were subgrouped based on sex, age, and ethnicity to compare the prevalence of suspected scoliosis. Univariate and multivariate logistic regression (LR) models were used to evaluate factors associated with suspected scoliosis.

RESULTS

During the post-COVID-19 pandemic period, 1,793,787 students participated. The overall prevalence of incorrect postures among Chinese adolescents was 79.92%, and the most common incorrect postures were high and low shoulders (74.18%) and scapular tilt (70.46%). A total of 97,529 students (5.44%) were suspected to have scoliosis. More females (7.5%) than males (3.7%) and more students aged > 15 years (15.12%) than those aged 10-15 years (7.58%) and < 10 years (0.88%) were suspected to have scoliosis. Univariate LR analysis showed that sex, age, grade, and various incorrect postures were significantly associated with suspected scoliosis. Multivariate LR analysis showed that being female (OR = 2.54, 95% CI: 1.68-3.85), age of 10-15 years (OR = 30.34, 95% CI: 4.99-12.64), and ages of > 15 years (OR = 22.30, 95% CI: 10.84-45.87), and incorrect posture, especially the lumbar eminence and right rib hump were high risk factors for suspected scoliosis.

CONCLUSIONS

The prevalence of incorrect posture and suspected scoliosis among Chinese adolescents increased significantly after the COVID-19 pandemic. Early screening of high-risk populations for suspected scoliosis and effective interventions should be implemented to prevent adolescent idiopathic scoliosis during the post-COVID-19 period.

Genetics and pathogenesis of scoliosis

Background

Scoliosis is defined as a lateral spine curvature of at least 10° with vertebral rotation, as seen on a posterior-anterior radiograph, often accompanied by reduced thoracic kyphosis. Scoliosis affects all age groups: idiopathic scoliosis is the most common spinal disorder in children and adolescents, while adult degenerative scoliosis typically affects individuals over fifty. In the United States, approximately 3 million new cases of scoliosis are diagnosed annually, with a predicted increase in part due to global aging. Despite its prevalence, the etiopathogenesis of scoliosis remains unclear.

Methods

This comprehensive review analyzes the literature on the etiopathogenetic evidence for both idiopathic and adult degenerative scoliosis. PubMed and Google Scholar databases were searched for studies on the genetic factors and etiopathogenetic mechanisms of scoliosis development and progression, with the search limited to articles in English.

Results

For idiopathic scoliosis, genetic factors are categorized into three groups: genes associated with susceptibility, disease progression, and both. We identify gene groups related to different biological processes and explore multifaceted pathogenesis of idiopathic scoliosis, including evolutionary adaptations to bipedalism and developmental and homeostatic spinal aberrations. For adult degenerative scoliosis, we segregate genetic and pathogenic evidence into categories of angiogenesis and inflammation, extracellular matrix degradation, neural associations, and hormonal influences. Finally, we compare findings in idiopathic scoliosis and adult degenerative scoliosis, discuss current limitations in scoliosis research, propose a new model for scoliosis etiopathogenesis, and highlight promising areas for future studies.

Conclusions

Scoliosis is a complex, multifaceted disease with largely enigmatic origins and mechanisms of progression, keeping it under continuous scientific scrutiny.

Planar cell polarity zebrafish models of congenital scoliosis reveal underlying defects in notochord morphogenesis

Congenital scoliosis (CS) is a type of vertebral malformation for which the etiology remains elusive. The notochord is pivotal for vertebrae development, but its role in CS is still understudied. Here, we generated a zebrafish knockout of ptk7a, a planar cell polarity (PCP) gene that is essential for convergence and extension (C&E) of the notochord, and detected congenital scoliosis-like vertebral malformations (CVMs). Maternal zygotic ptk7a mutants displayed severe C&E defects of the notochord. Excessive apoptosis occurred in the malformed notochord, causing a significantly reduced number of vacuolated cells, and compromising the mechanical properties of the notochord. The latter manifested as a less-stiff extracellular matrix along with a significant reduction in the number of the caveolae and severely loosened intercellular junctions in the vacuolated region. These defects led to focal kinks, abnormal mineralization, and CVMs exclusively at the anterior spine. Loss of function of another PCP gene, vangl2, also revealed excessive apoptosis in the notochord associated with CVMs. This study suggests a new model for CS pathogenesis that is associated with defects in notochord C&E and highlights an essential role of PCP signaling in vertebrae development.

Congenital spine deformities: timing of insult during development of the spine in utero

The development of the spine and spinal cord occurs at the earliest weeks of gestation. Their development not only affects each other but also are most likely associated with anomalies in other systems. It is essential to recognize the stages of spine development to understand the cause of congenital spinal deformities and their influences on the postnatal growing spine. A vast majority of congenital spinal problems are not evident clinically. For instance, the presence of neural axis abnormalities, such as spinal dysraphism or syringomyelia, may be so subtle that patients never seek medical care. Certain vertebral formation disorders such as hemivertebrae may remain asymptomatic throughout life if they are balanced while those with congenital bars may develop severe deformity. Major defects in the spine are often associated with abnormalities of the other organs such as cardiovascular and genital urinary system that warrants close attention by multidisciplinary specialists. A thorough understanding of the basics of embryology, which serves as a window into the development of the spine, is necessary to enable the practitioner to appreciate why, when, and where the numerous spine deformities develop in utero. Besides, certain developmental defects manifest in adulthood including spondylolysis, degenerative disc disease, congenital spinal stenosis, and even tumors like cordoma. Thus, understanding embryology can assist to establish the proper diagnosis and ensure optimal treatment.

Spatially defined single-cell transcriptional profiling characterizes diverse chondrocyte subtypes and nucleus pulposus progenitors in human intervertebral discs

A comprehensive understanding of the cellular heterogeneity and molecular mechanisms underlying the development, homeostasis, and disease of human intervertebral disks (IVDs) remains challenging. Here, the transcriptomic landscape of 108 108 IVD cells was mapped using single-cell RNA sequencing of three main compartments from young and adult healthy IVDs, including the nucleus pulposus (NP), annulus fibrosus, and cartilage endplate (CEP). The chondrocyte subclusters were classified based on their potential regulatory, homeostatic, and effector functions in extracellular matrix (ECM) homeostasis. Notably, in the NP, a PROCR⁺ resident progenitor population showed enriched colony-forming unit-fibroblast (CFU-F) activity and trilineage differentiation capacity. Finally, intercellular crosstalk based on signaling network analysis uncovered that the PDGF and TGF-β cascades are important cues in the NP microenvironment. In conclusion, a single-cell transcriptomic atlas that resolves spatially regulated cellular heterogeneity together with the critical signaling that underlies homeostasis will help to establish new therapeutic strategies for IVD degeneration in the clinic.

Spatially defined single-cell transcriptional profiling characterizes diverse chondrocyte subtypes and nucleus pulposus progenitors in human intervertebral discs

A comprehensive understanding of the cellular heterogeneity and molecular mechanisms underlying the development, homeostasis, and disease of human intervertebral disks (IVDs) remains challenging. Here, the transcriptomic landscape of 108 108 IVD cells was mapped using single-cell RNA sequencing of three main compartments from young and adult healthy IVDs, including the nucleus pulposus (NP), annulus fibrosus, and cartilage endplate (CEP). The chondrocyte subclusters were classified based on their potential regulatory, homeostatic, and effector functions in extracellular matrix (ECM) homeostasis. Notably, in the NP, a PROCR+ resident progenitor population showed enriched colony-forming unit-fibroblast (CFU-F) activity and trilineage differentiation capacity. Finally, intercellular crosstalk based on signaling network analysis uncovered that the PDGF and TGF-β cascades are important cues in the NP microenvironment. In conclusion, a single-cell transcriptomic atlas that resolves spatially regulated cellular heterogeneity together with the critical signaling that underlies homeostasis will help to establish new therapeutic strategies for IVD degeneration in the clinic.

Spatially defined single-cell transcriptional profiling characterizes diverse chondrocyte subtypes and nucleus pulposus progenitors in human intervertebral discs

A comprehensive understanding of the cellular heterogeneity and molecular mechanisms underlying the development, homeostasis, and disease of human intervertebral disks (IVDs) remains challenging. Here, the transcriptomic landscape of 108 108 IVD cells was mapped using single-cell RNA sequencing of three main compartments from young and adult healthy IVDs, including the nucleus pulposus (NP), annulus fibrosus, and cartilage endplate (CEP). The chondrocyte subclusters were classified based on their potential regulatory, homeostatic, and effector functions in extracellular matrix (ECM) homeostasis. Notably, in the NP, a PROCR⁺ resident progenitor population showed enriched colony-forming unit-fibroblast (CFU-F) activity and trilineage differentiation capacity. Finally, intercellular crosstalk based on signaling network analysis uncovered that the PDGF and TGF-β cascades are important cues in the NP microenvironment. In conclusion, a single-cell transcriptomic atlas that resolves spatially regulated cellular heterogeneity together with the critical signaling that underlies homeostasis will help to establish new therapeutic strategies for IVD degeneration in the clinic.

atoh8 expression pattern in early zebrafish embryonic development

Atonal homologue 8 (atoh8) is a basic helix-loop-helix transcription factor expressed in a variety of embryonic tissues. While several studies have implicated atoh8 in various developmental pathways in other species, its role in zebrafish development remains uncertain. So far, no studies have dealt with an in-depth in situ analysis of the tissue distribution of atoh8 in embryonic zebrafish. We set out to pinpoint the exact location of atoh8 expression in a detailed spatio-temporal analysis in zebrafish during the first 24 h of development (hpf). To our surprise, we observed transcription from pre-segmentation stages in the paraxial mesoderm and during the segmentation stages in the somitic sclerotome and not—as previously reported—in the myotome. With progressing maturation of the somites, the restriction of atoh8 to the sclerotomal compartment became evident. Double in situ hybridisation with atoh8 and myoD revealed that both genes are expressed in the somites at coinciding developmental stages; however, their domains do not spatially overlap. A second domain of atoh8 expression emerged in the embryonic brain in the developing cerebellum and hindbrain. Here, we observed a specific expression pattern which was again in contrast to the previously published suggestion of atoh8 transcription in neural crest cells. Our findings point towards a possible role of atoh8 in sclerotome, cerebellum and hindbrain development. More importantly, the results of this expression analysis provide new insights into early sclerotome development in zebrafish—a field of research in developmental biology which has not received much attention so far.

Assessment of adolescent idiopathic scoliosis from body scanner image by finite element simulations

Adolescent idiopathic scoliosis, is a three-dimensional spinal deformity characterized by lateral curvature and axial rotation around the vertical body axis of the spine, the cause of which is yet unknown. The fast progression entails regular clinical monitoring, including X-rays. Here we present an approach to evaluate scoliosis from the three-dimensional image of a patient’s torso, captured by an ionizing radiation free body scanner, in combination with a model of the ribcage and spine. A skeletal structure of the ribcage and vertebral column was modelled with computer aided designed software and was used as an initial structure for macroscopic finite element method simulations. The basic vertebral column model was created for an adult female in an upright position. The model was then used to simulate the patient specific scoliotic spine configurations. The simulations showed that a lateral translation of a vertebral body results in an effective axial rotation and could reproduce the spinal curvatures. The combined method of three-dimensional body scan and finite element model simulations thus provide quantitative anatomical information about the position, rotation and inclination of the thoracic and lumbar vertebrae within a three-dimensional torso. Furthermore, the simulations showed unequal distributions of stress and strain profiles across the intervertebral discs, due to their distortions, which might help to further understand the pathogenesis of scoliosis.

Metabolomic insights into the effects of thyroid hormone on Rana [Lithobates] catesbeiana metamorphosis using whole-body Matrix Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging (MALDI-MSI)

Anuran metamorphosis involves the transformation of an aquatic tadpole into a juvenile frog. This process is completely dependent upon thyroid hormones (THs). Although much research has been focused on changes in gene expression programs during this postembryonic developmental period, transitions in the metabolic profiles are relatively poorly understood. Matrix Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging (MALDI-MSI) is a technique that generates highly multiplexed mass spectra while retaining spatial location information on a thin tissue section. Reconstructed ion heat maps are correlated with morphology of the tissue section for biological interpretation. The present study is the first to use whole-body MALDI-MSI on tadpoles to gain insights into anuran metamorphosis. Approximately 1000 features were detected in each of five tissues examined (brain, eye, liver, notochord, and tail muscle) from premetamorphic North American bullfrog (Rana [Lithobates] catesbeiana) tadpoles. Of these detected metabolites, 1700 were unique and 136 were significantly affected by exposure to 50 nM thyroxine for 48 h. Of the significantly-affected metabolites, 64 features were tentatively identified using the MassTRIX annotation tool. All tissues revealed changes in lipophilic compounds including phosphatidylcholines, phosphatidylinositols, phosphatidylglycerols, phosphatidylethanolamines, and phosphatidylserines. These lipophilic compounds made up the largest portion of significantly-affected metabolites indicating that lipid signaling is a major target of TH action in frog tadpoles.

Embryonic origin of the gnathostome vertebral skeleton

The vertebral column is a key component of the jawed vertebrate (gnathostome) body plan, but the primitive embryonic origin of this skeleton remains unclear. In tetrapods, all vertebral components (neural arches, haemal arches and centra) derive from paraxial mesoderm (somites). However, in teleost fishes, vertebrae have a dual embryonic origin, with arches derived from somites, but centra formed, in part, by secretion of bone matrix from the notochord. Here, we test the embryonic origin of the vertebral skeleton in a cartilaginous fish (the skate, Leucoraja erinacea) which serves as an outgroup to tetrapods and teleosts. We demonstrate, by cell lineage tracing, that both arches and centra are somite-derived. We find no evidence of cellular or matrix contribution from the notochord to the skate vertebral skeleton. These findings indicate that the earliest gnathostome vertebral skeleton was exclusively of somitic origin, with a notochord contribution arising secondarily in teleosts.

The role of the notochord in amniote vertebral column segmentation

The vertebral column is segmented, comprising an alternating series of vertebrae and intervertebral discs along the head-tail axis. The vertebrae and outer portion (annulus fibrosus) of the disc are derived from the sclerotome part of the somites, whereas the inner nucleus pulposus of the disc is derived from the notochord. Here we investigate the role of the notochord in vertebral patterning through a series of microsurgical experiments in chick embryos. Ablation of the notochord causes loss of segmentation of vertebral bodies and discs. However, the notochord cannot segment in the absence of the surrounding sclerotome. To test whether the notochord dictates sclerotome segmentation, we grafted an ectopic notochord. We find that the intrinsic segmentation of the sclerotome is dominant over any segmental information the notochord may possess, and no evidence that the chick notochord is intrinsically segmented. We propose that the segmental pattern of vertebral bodies and discs in chick is dictated by the sclerotome, which first signals to the notochord to ensure that the nucleus pulposus develops in register with the somite-derived annulus fibrosus. Later, the notochord is required for maintenance of sclerotome segmentation as the mature vertebral bodies and intervertebral discs form. These results highlight differences in vertebral development between amniotes and teleosts including zebrafish, where the notochord dictates the segmental pattern. The relative importance of the sclerotome and notochord in vertebral patterning has changed significantly during evolution.

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The chick notochord has no intrinsic segmentation.

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Neither notochord or sclerotome can segment normally without the other.

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The notochord attracts sclerotome cells to the midline.

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Vertebral segmentation involves reciprocal signals between notochord and sclerotome.

Malformed vertebrae: a clinical and imaging review

A variety of structural developmental anomalies affect the vertebral column. Malformed vertebrae can arise secondary to errors of vertebral formation, fusion and/or segmentation and developmental variation. Malformations can be simple with little or no clinical consequence, or complex with serious structural and neurologic implications. These anomalies can occasionally mimic acute trauma (bipartite atlas versus Jefferson fracture, butterfly vertebra versus burst fracture), or predispose the affected individual to myelopathy. Accurate imaging interpretation of vertebral malformations requires knowledge of ageappropriate normal, variant and abnormal vertebral morphology and the clinical implications of each entity. This knowledge will improve diagnostic confidence in acute situations and confounding clinical scenarios.

This review article seeks to familiarize the reader with the embryology, normal and variant anatomy of the vertebral column and the imaging appearance and clinical impact of the spectrum of vertebral malformations arising as a consequence of disordered embryological development.

Teaching points

• Some vertebral malformations predispose the affected individual to trauma or myelopathy.

• On imaging, malformed vertebrae can be indistinguishable from acute trauma.

• Abnormalities in spinal cord development may be associated and must be searched for.

• Accurate interpretation requires knowledge of normal, variant and abnormal vertebral morphology.

Differentiation of human induced pluripotent stem cells into nucleus pulposus-like cells

Background

Intervertebral disc (IVD) degeneration is characterized by an early decrease in cellularity of the nucleus pulposus (NP) region, and associated extracellular matrix changes, reduced hydration, and progressive degeneration. Cell-based IVD therapy has emerged as an area of great interest, with studies reporting regenerative potential for many cell sources, including autologous or allogeneic chondrocytes, primary IVD cells, and stem cells. Few approaches, however, have clear strategies to promote the NP phenotype, in part due to a limited knowledge of the defined markers and differentiation protocols for this lineage. Here, we developed a new protocol for the efficient differentiation of human induced pluripotent stem cells (hiPSCs) into NP-like cells in vitro. This differentiation strategy derives from our knowledge of the embryonic notochordal lineage of NP cells as well as strategies used to support healthy NP cell phenotypes for primary cells in vitro.

Methods

An NP-genic phenotype of hiPSCs was promoted in undifferentiated hiPSCs using a stepwise, directed differentiation toward mesodermal, and subsequently notochordal, lineages via chemically defined medium and growth factor supplementation. Fluorescent cell imaging was used to test for pluripotency markers in undifferentiated cells. RT-PCR was used to test for potential cell lineages at the early stage of differentiation. Cells were checked for NP differentiation using immunohistochemistry and histological staining at the end of differentiation. To enrich notochordal progenitor cells, hiPSCs were transduced using lentivirus containing reporter constructs for transcription factor brachyury (T) promoter and green fluorescent protein (GFP) fluorescence, and then sorted on T expression based on GFP intensity by flow cytometry.

Results

Periods of pellet culture following initial induction were shown to promote the vacuolated NP cell morphology and NP surface marker expression, including CD24, LMα5, and Basp1. Enrichment of brachyury (T) positive cells using fluorescence-activated cell sorting was shown to further enhance the differentiation efficiency of NP-like cells.

Conclusions

The ability to efficiently differentiate human iPSCs toward NP-like cells may provide insights into the processes of NP cell differentiation and provide a cell source for the development of new therapies for IVD diseases.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0797-1) contains supplementary material, which is available to authorized users.

SMD Kozlowski type caused by p.Arg594His substitution in TRPV4 reveals abnormal ossification and notochordal remnants in discs and vertebrae

Spondylometaphyseal dysplasia Kozlowski type (SMDK) is a monogenic disorder within the TRPV4 dysplasia spectrum and has characteristic spinal and metaphyseal changes. We report skeletal MR imaging in a two-year-old patient who manifested typical clinical and radiographic features of SMDK. The diagnosis was confirmed by molecular analysis which revealed a mutation NM_021625.4:c.1781G > A - p.(Arg594His) in exon 11 of the TRPV4 gene. We have documented abnormalities in endochondral formation of the long and short tubular bones as well as round bones of the wrists and feet. The vertebral bodies had increased thickness of hyaline cartilage which enveloped ossification centers. The vertebrae and discs also had abnormalities in size, shape and structure. These anomalies were most likely the consequence of notochordal remnants presence within the intervertebral discs and in the vertebral bodies. The advantages of MR imaging in bone dysplasias caused by TRPV4 mutations are emphasized in this article.

Posterior tail development in the salamander Eurycea cirrigera: exploring cellular dynamics across life stages

During embryogenesis, the body axis elongates and specializes. In vertebrate groups such as salamanders and lizards, elongation of the posterior body axis (tail) continues throughout life. This phenomenon of post-embryonic tail elongation via addition of vertebrae has remained largely unexplored, and little is known about the underlying developmental mechanisms that promote vertebral addition. Our research investigated tail elongation across life stages in a non-model salamander species, Eurycea cirrigera (Plethodontidae). Post-embryonic addition of segments suggests that the tail tip retains some aspects of embryonic cell/tissue organization and gene expression throughout the life cycle. We describe cell and tissue differentiation and segmentation of the posterior tail using serial histology and expression of the axial tissue markers, MF-20 and Pax6. Embryonic expression patterns of HoxA13 and C13 are shown with in situ hybridization. Tissue sections reveal that the posterior spinal cord forms via cavitation and precedes development of the underlying cartilaginous rod after embryogenesis. Post-embryonic tail elongation occurs in the absence of somites and mesenchymal cells lateral to the midline express MF-20. Pax6 expression was observed only in the spinal cord and some mesenchymal cells of adult Eurycea tails. Distinct temporal and spatial patterns of posterior Hox13 gene expression were observed throughout embryogenesis. Overall, important insights to cell organization, differentiation, and posterior Hox gene expression may be gained from this work. We suggest that further work on gene expression in the elongating adult tail could shed light on mechanisms that link continual axial elongation with regeneration.

Identifying molecular phenotype of nucleus pulposus cells in human intervertebral disc with aging and degeneration

Previous study claimed that disc degeneration may be preceded by structure and matrix changes in the intervertebral disc (IVD) which coincide with the loss of distinct notochordally derived nucleus pulposus (NP) cells. However, the fate of notochordal cells and their molecular phenotype change during aging and degeneration in human are still unknown. In this study, a set of novel molecular phenotype markers of notochordal NP cells during aging and degeneration in human IVD tissue were revealed with immunostaining and flow cytometry. Furthermore, the potential of phenotype juvenilization and matrix regeneration of IVD cells in a laminin-rich pseudo-3D culture system were evaluated at day 28 by immunostaining, Safranin O, and type II collagen staining. Immunostaining and flow cytometry demonstrated that transcriptional factor Brachyury T, neuronal-related proteins (brain abundant membrane attached signal protein 1, Basp1; Neurochondrin, Ncdn; Neuropilin, Nrp-1), CD24, and CD221 were expressed only in juvenile human NP tissue, which suggested that these proteins may be served as the notochordal NP cell markers. However, the increased expression of CD54 and CD166 with aging indicated that they might be referenced as the potential biomarker for disc degeneration. In addition, 3D culture maintained most of markers in juvenile NP, and rescued the expression of Basp1, Ncdn, and Nrp 1 that disappeared in adult NP native tissue. These findings provided new insight into molecular profile that may be used to characterize the existence of a unique notochordal NP cells during aging and degeneration in human IVD cells, which will facilitate cell-based therapy for IVD regeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1316-1326, 2016.

Decoding the intervertebral disc: Unravelling the complexities of cell phenotypes and pathways associated with degeneration and mechanotransduction

Back pain is the most common cause of pain and disability worldwide. While its etiology remains unknown, it is typically associated with intervertebral disc (IVD) degeneration. Despite the prevalence of back pain, relatively little is known about the specific cellular pathways and mechanisms that contribute to the development, function and degeneration of the IVD. Consequently, current treatments for back pain are largely limited to symptomatic interventions. However, major progress is being made in multiple research directions to unravel the biology and pathology of the IVD, raising hope that effective disease-modifying interventions will soon be developed. In this review, we will discuss our current knowledge and gaps in knowledge on the developmental origin of the IVD, the phenotype of the distinct cell types found within the IVD tissues, molecular targets in IVD degeneration identified using bioinformatics strategies, and mechanotransduction pathways that influence IVD cell fate and function.

Expression of growth differentiation factor 6 in the human developing fetal spine retreats from vertebral ossifying regions and is restricted to cartilaginous tissues

During embryogenesis vertebral segmentation is initiated by sclerotomal cell migration and condensation around the notochord, forming anlagen of vertebral bodies and intervertebral discs. The factors that govern the segmentation are not clear. Previous research demonstrated that mutations in growth differentiation factor 6 resulted in congenital vertebral fusion, suggesting this factor plays a role in development of vertebral column. In this study, we detected expression and localization of growth differentiation factor 6 in human fetal spinal column, especially in the period of early ossification of vertebrae and the developing intervertebral discs. The extracellular matrix proteins were also examined. Results showed that high levels of growth differentiation factor 6 were expressed in the nucleus pulposus of intervertebral discs and the hypertrophic chondrocytes adjacent to the ossification centre in vertebral bodies, where strong expression of proteoglycan and collagens was also detected. As fetal age increased, the expression of growth differentiation factor 6 was decreased correspondingly with the progress of ossification in vertebral bodies and restricted to cartilaginous regions. This expression pattern and the genetic link to vertebral fusion suggest that growth differentiation factor 6 may play an important role in suppression of ossification to ensure proper vertebral segmentation during spinal development.

Immunohistochemical Studies of Cytoskeletal and Extracellular Matrix Components in Dogfish Scyliorhinus canicula L. Notochordal Cells

Immunofluorescence and immunohistochemical techniques were used to define the distribution of cytoskeletal (cytokeratin 8, vimentin) and extracellular matrix components (collagen type I, collagen type II, hyaluronic acid, and aggrecan) and bone morphogenetic proteins 4 and 7 (BMP4 and BMP7) in the notochord of the lesser spotted dogfish Scyliorhinus canicula L. Immunolocalization of hyaluronic acid was observed in the notochord, vertebral centrum, and neural and hemal arches, while positive labeling to aggrecan was observed in the ossified centrum, notochord, and the perichondrium of the hyaline cartilage. Type I collagen was observed in the mineralized cartilage of the vertebral bodies, the notochord, the fibrocartilage of intervertebral disc, and the perichondrium. A positive labeling to type II collagen was observed in the inner part of the cartilaginous vertebral centrum and the notochord, as well as in the neural arch and muscle tissue, but there was no appreciable labeling of the hyaline cartilage. The presence of both BMP4 and BMP7 was seen in the mineralized vertebral centrum, notochordal cells, and neural arch. The notochordal cells expressed both cytokeratin 8 and vimentin, but predominantly vimentin. Hyaluronic acid, collagen type I, and collagen type II expression confirmed the presence of a mixture of notochordal and fibrocartilaginous tissue in the intervertebral disc, while BMPs confirmed the presence of an ossification in the cartilaginous skeleton of the spotted dogfish.

Transient infection of the zebrafish notochord with E. coli induces chronic inflammation

Zebrafish embryos and larvae are now well-established models in which to study infectious diseases. Infections with non-pathogenic Gram-negative Escherichia coli induce a strong and reproducible inflammatory response. Here, we study the cellular response of zebrafish larvae when E. coli bacteria are injected into the notochord and describe the effects. First, we provide direct evidence that the notochord is a unique organ that is inaccessible to leukocytes (macrophages and neutrophils) during the early stages of inflammation. Second, we show that notochord infection induces a host response that is characterised by rapid clearance of the bacteria, strong leukocyte recruitment around the notochord and prolonged inflammation that lasts several days after bacteria clearance. During this inflammatory response, il1b is first expressed in macrophages and subsequently at high levels in neutrophils. Moreover, knock down of il1b alters the recruitment of neutrophils to the notochord, demonstrating the important role of this cytokine in the maintenance of inflammation in the notochord. Eventually, infection of the notochord induces severe defects of the notochord that correlate with neutrophil degranulation occurring around this tissue. This is the first in vivo evidence that neutrophils can degranulate in the absence of a direct encounter with a pathogen. Persistent inflammation, neutrophil infiltration and restructuring of the extracellular matrix are defects that resemble those seen in bone infection and in some chondropathies. As the notochord is a transient embryonic structure that is closely related to cartilage and bone and that contributes to vertebral column formation, we propose infection of the notochord in zebrafish larvae as a new model to study the cellular and molecular mechanisms underlying cartilage and bone inflammation.

TALEN-mediated mutagenesis in zebrafish reveals a role for r-spondin 2 in fin ray and vertebral development

R-spondin (Rspo) encodes a multi-domain protein that modulates the Wnt-signaling pathway. Two distinct rspo2 zebrafish mutants were generated by TALEN-mediated mutagenesis: a null mutant, rspo2(null), lacking all functional domains, and a hypomorphic mutant, rspo2(tsp), lacking the two N-terminal domains. Mutants were analyzed mainly for abnormalities in the skeletal system. Fin ray skeletons were formed normally in the rspo2(tsp) mutants, but were absent from the rspo2(null) mutants. Hypoplasia of the neural/hemal arches and ribs was observed in both mutants. Thus, the two rspo2 mutants help to identify the functions of Rspo2 in skeletogenesis, as well as functional differences among multiple Rspo2 domains.

Chordoma: the entity

Chordomas are malignant tumors of the axial skeleton, characterized by their locally invasive and slow but aggressive growth. These neoplasms are presumed to be derived from notochordal remnants with a molecular alteration preceding their malignant transformation. As these tumors are most frequently observed on the skull base and sacrum, patients suffering from a chordoma present with debilitating neurological disease, and have an overall 5-year survival rate of 65%. Surgical resection with adjuvant radiotherapy is the first-choice treatment modality in these patients, since chordomas are resistant to conventional chemotherapy. Even so, management of chordomas can be challenging, as chordoma patients often present with recurrent disease. Recent advances in the understanding of the molecular events that contribute to the development of chordomas are promising; the most novel finding being the identification of brachyury in the disease process. Here we present an overview of the current paradigms and summarize relevant research findings.

An assessment of the long-term effects of simulated microgravity on cranial neural crest cells in zebrafish embryos with a focus on the adult skeleton

It is becoming increasingly important to address the long-term effects of exposure to simulated microgravity as the potential for space tourism and life in space become prominent topics amongst the World's governments. There are several studies examining the effects of exposure to simulated microgravity on various developmental systems and in various organisms; however, few examine the effects beyond the juvenile stages. In this study, we expose zebrafish embryos to simulated microgravity starting at key stages associated with cranial neural crest cell migration. We then analyzed the skeletons of adult fish. Gross observations and morphometric analyses show that exposure to simulated microgravity results in stunted growth, reduced ossification and severe distortion of some skeletal elements. Additionally, we investigated the effects on the juvenile skull and body pigmentation. This study determines for the first time the long-term effects of embryonic exposure to simulated microgravity on the developing skull and highlights the importance of studies investigating the effects of altered gravitational forces.

Notochordal cell-derived therapeutic strategies for discogenic back pain

An understanding of the processes that occur during development of the intervertebral disk can help inform therapeutic strategies for discogenic pain. This article reviews the literature to identify candidates that are found in or derived from the notochord or notochordal cells and evaluates the theory that such factors could be isolated and used as biologics to target the structural disruption, inflammation, and neurovascular ingrowth often associated with discogenic back pain. A systematic review using PubMed was performed with a primary search using keywords "(notochordal OR notochord) And (nerves OR blood vessels OR SHH OR chondroitin sulfate OR notch OR CTGF) NOT chordoma." Secondary searches involved keywords associated with the intervertebral disk and pain. Several potential therapeutic candidates from the notochord and their possible targets were identified. Studies are needed to further identify candidates, explore mechanisms for effect, and to validate the theory that these candidates can promote structural restoration and limit or inhibit neurovascular ingrowth using in vivo studies.

Embryology of Early Jurassic dinosaur from China with evidence of preserved organic remains

Fossil dinosaur embryos are surprisingly rare, being almost entirely restricted to Upper Cretaceous strata that record the late stages of non-avian dinosaur evolution. Notable exceptions are the oldest known embryos from the Early Jurassic South African sauropodomorph Massospondylus and Late Jurassic embryos of a theropod from Portugal. The fact that dinosaur embryos are rare and typically enclosed in eggshells limits their availability for tissue and cellular level investigations of development. Consequently, little is known about growth patterns in dinosaur embryos, even though post-hatching ontogeny has been studied in several taxa. Here we report the discovery of an embryonic dinosaur bone bed from the Lower Jurassic of China, the oldest such occurrence in the fossil record. The embryos are similar in geological age to those of Massospondylus and are also assignable to a sauropodomorph dinosaur, probably Lufengosaurus. The preservation of numerous disarticulated skeletal elements and eggshells in this monotaxic bone bed, representing different stages of incubation and therefore derived from different nests, provides opportunities for new investigations of dinosaur embryology in a clade noted for gigantism. For example, comparisons among embryonic femora of different sizes and developmental stages reveal a consistently rapid rate of growth throughout development, possibly indicating that short incubation times were characteristic of sauropodomorphs. In addition, asymmetric radial growth of the femoral shaft and rapid expansion of the fourth trochanter suggest that embryonic muscle activation played an important role in the pre-hatching ontogeny of these dinosaurs. This discovery also provides the oldest evidence of in situ preservation of complex organic remains in a terrestrial vertebrate.

'Monster… -omics': on segmentation, re-segmentation, and vertebrae formation in amphibians and other vertebrates

Background

The axial skeleton is one of the defining evolutionary landmarks of vertebrates. How this structure develops and how it has evolved in the different vertebrate lineages is, however, a matter of debate. Vertebrae and vertebral structures are derived from the embryonic somites, although the mechanisms of development are different between lineages.

Discussion

Using the anecdotal description of a teratological newt (Triturus dobrogicus) with an unusual malformation in its axial skeleton, we review, compare, and discuss the development of vertebral structures and, in particular, the development of centra from somitic cellular domains in different vertebrate groups. Vertebrae development through re-segmentation of the somitic sclerotomal cells is considered the general mechanism among vertebrates, which has been generalized from studies in amniotic model organisms. The prevalence of this mechanism among anamniotes is, however, controversial. We propose alternative developmental mechanisms for vertebrae formation that should be experimentally tested.

Summary

Research in model organisms, especially amniotes, is laying the foundations for a thorough understanding of the mechanisms of development of the axial skeleton in vertebrates, foundations that should expand the extent of future comparative studies. Although immersed in the ‘-omics’ era, we emphasize the need for an integrative and organismal approach in evolutionary developmental biology for a better understanding of the causal role of development in the evolution of morphological diversity in nature.

Down-regulated CK8 expression in human intervertebral disc degeneration

As an intermediate filament protein, cytokeratin 8 (CK8) exerts multiple cellular functions. Moreover, it has been identified as a marker of notochord cells, which play essential roles in human nucleus pulposus (NP). However, the distribution of CK8 positive cells in human NP and their relationship with intervertebral disc degeneration (IDD) have not been clarified until now. Here, we found the percentage of CK8 positive cells in IDD (25.7±4.14%) was significantly lower than that in normal and scoliosis NP (51.9±9.73% and 47.8±5.51%, respectively, p<0.05). Western blotting and qRT-PCR results confirmed the down-regulation of CK8 expression in IDD on both of protein and mRNA levels. Furthermore, approximately 37.4% of cell clusters were CK8 positive in IDD. Taken together, this is the first study to show a down-regulated CK8 expression and the percentage of CK8 positive cell clusters in IDD based upon multiple lines of evidence. Consequently, CK8 positive cells might be considered as a potential option in the development of cellular treatment strategies for NP repair.

Coronal vertebral clefts: a radiological indicator for chromosomal aberrations

Coronal clefts-a radiolucent band running through at least one vertebral body, visualized in the lateral spinal radiograph and discussed as a physiological variation of the fetal vertebral ossification pattern-are often found in fetal autopsies with trisomies. Published studies are missing concerning the question of whether this finding could serve as a diagnostic radiological or even ultrasonographic sign. We studied the incidence of radiological coronal clefts and their association with chromosomal aberrations in 443 fetuses (mostly medically induced abortions). In 42 of the 443 fetuses (9.5%), coronal clefts were visualized. The majority (71%) were localized in the lumbar spine. No cervical or singular sacral clefts were detected. Twenty-five of the 42 fetuses (60%) displaying coronal clefts had chromosomal aberrations, either as a trisomy (13 or 21) or as monosomy X. Histologically, coronal clefts showed a missing central ossification of the vertebral body. Remnants of the notochord could be excluded. Hence, coronal clefts represent a variant ossification of vertebral bodies in fetal development that is found almost exclusively in fetuses with chromosomal aberrations or severe congenital malformations. This finding could be a helpful supplement to prenatal diagnostics and fetal autopsy. On the other hand, the genetic diagnosis of chromosomal aberration, especially trisomy, does not automatically imply the presence of coronal clefts.

Changes in the molecular phenotype of nucleus pulposus cells with intervertebral disc aging

Intervertebral disc (IVD) disorder and age-related degeneration are believed to contribute to low back pain. Cell-based therapies represent a promising strategy to treat disc degeneration; however, the cellular and molecular characteristics of disc cells during IVD maturation and aging still remain poorly defined. This study investigated novel molecular markers and their age-related changes in the rat IVD. Affymetrix cDNA microarray analysis was conducted to identify a new set of genes characterizing immature nucleus pulposus (NP) cells. Among these markers, select neuronal-related proteins (Basp1, Ncdn and Nrp-1), transcriptional factor (Brachyury T), and cell surface receptors (CD24, CD90, CD155 and CD221) were confirmed by real-time PCR and immunohistochemical (IHC) staining for differential expression between IVD tissue regions and among various ages (1, 12 and 21 months). NP cells generally possessed higher levels of mRNA or protein expression for all aforementioned markers, with the exception of CD90 in anulus fibrosus (AF) cells. In addition, CD protein (CD24 and CD90) and Brachyury (T) expression in immature disc cells were also confirmed via flow cytometry. Similar to IHC staining, results revealed a higher percentage of immature NP cells expressing CD24 and Brachyury, while higher percentage of immature AF cells was stained positively for CD90. Altogether, this study identifies that tissue-specific gene expression and age-related differential expression of the above markers do exist in immature and aged disc cells. These age-related phenotype changes provide a new insight for a molecular profile that may be used to characterize NP cells for developing cell-based regenerative therapy for IVD regeneration.

Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation

BACKGROUND

In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans) or ossify (osteichthyans). Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small teleost species, including zebrafish (Danio rerio), even haemal and neural arches form directly as intramembranous bone and only modified caudalmost arches remain cartilaginous. This study compares initial patterns of mineralization in different regions of the vertebral column in zebrafish. We ask if the absence or presence of cartilaginous arches influences the pattern of notochord sheath mineralization.

RESULTS

To reveal which cells are involved in mineralization of the notochord sheath we identify proliferating cells, we trace mineralization on the histological level and we analyze cell ultrastructure by TEM. Moreover, we localize proteins and genes that are typically expressed by skeletogenic cells such as Collagen type II, Alkaline phosphatase (ALP) and Osteocalcin (Oc). Mineralization of abdominal and caudal vertebrae starts with a complete ring within the notochord sheath and prior to the formation of the bony arches. In contrast, notochord mineralization of caudal fin centra starts with a broad ventral mineral deposition, associated with the bases of the modified cartilaginous arches. Similar, arch-related, patterns of mineralization occur in teleosts that maintain cartilaginous arches throughout the spine.Throughout the entire vertebral column, we were able to co-localize ALP-positive signal with chordacentrum mineralization sites, as well as Collagen II and Oc protein accumulation in the mineralizing notochord sheath. In the caudal fin region, ALP and Oc signals were clearly produced both by the notochord epithelium and cells outside the notochord, the cartilaginous arches. Based on immunostaining, real time PCR and oc2:gfp transgenic fish, we identify Oc in the mineralizing notochord sheath as osteocalcin isoform 1 (Oc1).

CONCLUSIONS

If notochord mineralization occurs prior to arch formation, mineralization of the notochord sheath is ring-shaped. If notochord mineralization occurs after cartilaginous arch formation, mineralization of the notochord sheath starts at the insertion point of the arches, with a basiventral origin. The presence of ALP and Oc1, not only in cells outside the notochord, but also in the notochord epithelium, suggests an active role of the notochord in the mineralization process. The same may apply to Col II-positive chondrocytes of the caudalmost haemal arches that show ALP activity and Oc1 accumulation, since these chondrocytes do not mineralize their own cartilage matrix. Even without cartilaginous preformed vertebral centra, the cartilaginous arches may have an inductive role in vertebral centrum formation, possibly contributing to the distinct mineralization patterns of zebrafish vertebral column and caudal fin vertebral fusion.

Diversity of intervertebral disc cells: phenotype and function

The intervertebral disc (IVD) is a moderately moving joint that is located between the bony vertebrae and provides flexibility and load transmission throughout the spinal column. The disc is composed of different but interrelated tissues, including the central highly hydrated nucleus pulposus (NP), the surrounding elastic and fibrous annulus fibrosus (AF), and the cartilaginous endplate (CEP), which provides the connection to the vertebral bodies. Each of these tissues has a different function and consists of a specific matrix structure that is maintained by a cell population with distinct phenotype. Although the healthy IVD is able to balance the slow matrix turnover of synthesis and degradation, this balance is often disturbed, leading to degenerative disorders. Successful therapeutic management of IVD degeneration requires a profound understanding of the cellular and molecular characteristics of the functional IVD. Hence, the phenotype of IVD cells has been of significant interest from multiple perspectives, including development, growth, remodelling, degeneration and repair. One major challenge that complicates our understanding of the disc cells is that both the cellular phenotype and the extracellular matrix strongly depend on disc maturity and health and as a consequence are continuously evolving. This review delineates the diversity of the cell types found in the intervertebral disc, with emphasis on human, but with reference to other species. The cells of the NP appear rounded and express a proteoglycan-rich matrix, whereas the more elongated AF cells are embedded in a collagen fibre matrix and the CEPs represent a layer of cartilage. Even though all disc cells have often been referred to as 'intervertebral disc chondrocytes', distinct phenotypical differences in comparison with articular chondrocytes exist and have been reported recently. The availability of more specific markers has also improved our understanding of progenitor cell differentiation towards an IVD cell phenotype. Ultimately, new cell- and tissue-engineering approaches to regenerative therapies will only be successful if the specific characteristics of the individual tissues and their context in the function of the whole organ, are taken into consideration.

The generation of vertebral segmental patterning in the chick embryo

We have carried out a series of experimental manipulations in the chick embryo to assess whether the notochord, neural tube and spinal nerves influence segmental patterning of the vertebral column. Using Pax1 expression in the somite-derived sclerotomes as a marker for segmentation of the developing intervertebral disc, our results exclude such an influence. In contrast to certain teleost species, where the notochord has been shown to generate segmentation of the vertebral bodies (chordacentra), these experiments indicate that segmental patterning of the avian vertebral column arises autonomously in the somite mesoderm. We suggest that in amniotes, the subdivision of each sclerotome into non-miscible anterior and posterior halves plays a critical role in establishing vertebral segmentation, and in maintaining left/right alignment of the developing vertebral elements at the body midline.

Regulatory changes of N-acetylgalactosamine terminal sugar in early mouse embryonic paraxial mesenchyme

OBJECTIVE

The development of vertebrae is a complex phenomenon that is correlated with distinct morphological and biochemical alterations in the paraxial mesenchyme and glycoconjugates. The purpose of this study is to investigate the glycosylation pattern in paraxial mesenchyme-forming vertebrae by using the lectin histochemical technique.

MATERIALS AND METHODS

In this descriptive-analytic study, B4G fixed paraffin sections of 9 to 15 day Balb/c mouse embryos were processed for histochemical studies using seven different HRP-labelled lectins: Glycin max (SBA), Maclura pomifera (MPA), Wistaria floribunda (WFA), Vicia villosa (VVA) which all of them are specific for N-acetylgalactosamine (GalNAc), Ulex europius (UEA1, binds to α-L-fucose), wheat germ agglutinin (WGA, binds to sialic acid), and Griffonia simplicifolia (GSA1-B4, binds to galactose terminal sugars). The sections were observed separately by three examiners who were blinded to the lectins. Grading was done according to the intensity of the tested lectins' reactions with the specimen, from negative (-) to severe (+++). Data was analysed with SPSS software (version 11.5) and the non-parametric Kruskal Wallis test; p<0.05 was considered significant.

RESULTS

Our findings showed that among the tested lectins, only GalNAc residue sensitive lectins showed regulated changes in paraxial mesenchyme. Reactions of WFA and MPA lectins with paraxial mesenchyme were severe on GD9. Reactions of WFA continued to GD15 constantly, while MPA reactions continued strongly to GD12, significantly decreased thereafter (p<0.001), and then disappeared. VVA and SBA bindings initiated weakly on GD10 and continued to GD12 without changing. These reactions increased significantly (p<0.001) thereafter, became severe to GD14, and later disappeared. The other tested lectins did not reveal regulated changes.

CONCLUSION

According to these findings it can be concluded that only the GalNAc terminal sugar showed temporally regulated changes during the early embryonic development of vertebrae in mice. Therefore it most likely plays a key role (s) in the development of vertebrae, especially in the conversion of mesenchymal cells into chondroblasts. The other tested terminal sugars may have no role in this phenomenon.

Normal axial skeleton structure in common roach Rutilus rutilus (Actinopterygii: Cyprinidae) and malformations due to radiation contamination in the area of the Mayak (Chelyabinsk Province, Russia) nuclear plant

This study was designed to describe normal axial skeletal structure in common roach Rutilus rutilus from putative unaffected environmental conditions, and the occurrence of skeletal malformations in the fish from an area under radiation contamination. Specimens were collected from water bodies of the Techa Cascade Reservoirs located near the Mayak atomic industry plant in the River Ob' drainage, Chelyabinsk Province, Russia. One sample was collected from Lake Irtyash, a reservoir of drinkable water, supplying the town of Ozersk, and the other one from a technical reservoir which is a storage of liquid radioactive waste from Mayak and characterized by high radioactive contamination (mostly (90)Sr and (137)Cs). A comparison was made with historical material collected from the River Ob' before the middle of the 20th century, i.e. before the environment became affected by radioactive contamination. A high number of abnormalities of the axial skeleton were detected in both Mayak samples, in 94 and 97% of examined specimens, in contrast to about 20% in the historical specimens. The abnormalities were in both the unpaired fins and the vertebral column, including the caudal complex and included supernumerary elements, fusions, deformities and displacement of the elements. Most axial skeleton abnormalities, however, were minor, such as splitting, shortening or deformation of spines. Severe defects, such as extensive scolioses, lordoses and kyphoses, were not found. The causes of the abnormalities were not identified in this study, but the high incidence of malformations may be attributed to genetically determined imbalance during development. The almost equal distribution of abnormalities among the fish from non-contaminated and radioactive contaminated reservoirs may be explained by either recent gene flow within the population of R. rutilus in the River Techa system or the effect of unknown unfavourable environmental factors such as chemical pollution.

Degeneration and regeneration of the intervertebral disc: lessons from development

Degeneration of the intervertebral discs, a process characterized by a cascade of cellular, biochemical, structural and functional changes, is strongly implicated as a cause of low back pain. Current treatment strategies for disc degeneration typically address the symptoms of low back pain without treating the underlying cause or restoring mechanical function. A more in-depth understanding of disc degeneration, as well as opportunities for therapeutic intervention, can be obtained by considering aspects of intervertebral disc development. Development of the intervertebral disc involves the coalescence of several different cell types through highly orchestrated and complex molecular interactions. The resulting structures must function synergistically in an environment that is subjected to continuous mechanical perturbation throughout the life of an individual. Early postnatal changes, including altered cellularity, vascular regression and altered extracellular matrix composition, might set the disc on a slow course towards symptomatic degeneration. In this Perspective, we review the pathogenesis and treatment of intervertebral disc degeneration in the context of disc development. Within this scope, we examine how model systems have advanced our understanding of embryonic morphogenesis and associated molecular signaling pathways, in addition to the postnatal changes to the cellular, nutritional and mechanical microenvironment. We also discuss the current status of biological therapeutic strategies that promote disc regeneration and repair, and how lessons from development might provide clues for their refinement.

Clinical characteristics of dural arteriovenous shunts in 446 patients of three different ethnicities

SUMMARY

Dural arteriovenous shunts (DAVSs) developing in either the ventral, dorsal or lateral epidural spaces (VE, DE and LE-shunts) predictably drain in either cranio/spino-fugal or -petal directions. Associated conditions like venous outflow restrictions (VOR) may be responsible for changes in this drainage pattern. The goal of this study was to compare demographic, angiographic and clinical characteristics of different types of DAVS in Europe, South America, and Asia to find out whether the same clinical profile is present in different ethnicities. Charts and angiographic films of 446 patients with DAVS from three hospitals in Europe, Asia and South America were retrospectively evaluated. Clinical symptoms were separated into benign and aggressive and the presence or absence of cortical venous reflux (CVR) and VOR was noted. LE-shunts were present in elderly men and were always associated with CVR resulting in aggressive symptoms. VE-shunts were present in females and almost always had benign symptoms. There were no differences among the three populations for these shunts. DE-shunts in the Asian population were more aggressive secondary to a higher rate of VOR with associated CVR. VE-shunts rarely lead to CVR even in the presence of VOR, whereas LE-shunts invariably lead to CVR, irrespective of the population investigated. CVR in DE-shunts is not related to the primary disease (i.e. the shunt itself) but to associated factors that led to VOR. Since the occurrence of these varied between different ethnicities, DE-shunts were aggressive in the Asian population and benign in the European and South American populations.

Znrg, a novel gene expressed mainly in the developing notochord of zebrafish

The notochord, a defining characteristic of the chordate embryo is a critical midline structure required for axial skeletal formation in vertebrates, and acts as a signaling center throughout embryonic development. We utilized the digital differential display program of the National Center for Biotechnology Information, and identified a contig of expressed sequence tags (no. Dr. 83747) from the zebrafish ovary library in Genbank. Full-length cDNA of the identified gene was cloned by 5'- and 3'- RACE, and the resulting sequence was confirmed by polymerase chain reaction and sequencing. The cDNA clone contains 2,505 base pairs and encodes a novel protein of 707 amino acids that shares no significant homology with any known proteins. This gene was expressed in mature oocytes and at the one-cell stage, and persisted until the 5th day of development, as determined by RT-PCR. Transcripts were detected by whole-mount RNA in situ hybridization from the two-cell stage to 72 h of embryonic development. This gene was uniformly distributed from the cleavage stage up to the blastula stage. During early gastrulation, it was present in the dorsal region, and became restricted to the notochord and pectoral fin at 48 and 72 h of embryonic development. Based on its abundance in the notochord, we hypothesized that the novel gene may play an important role in notochord development in zebrafish; we named this gene, zebrafish notochord-related gene, or znrg.

Spinal dural arteriovenous fistulas

Spinal dural arteriovenous (AV) fistulas are the most commonly encountered vascular malformation of the spinal cord and a treatable cause for progressive para- or tetraplegia. They most commonly affect elderly men and are classically found in the thoracolumbar region. The AV shunt is located inside the dura mater close to the spinal nerve root where the arterial blood from a radiculomeningeal artery enters a radicular vein. The increase in spinal venous pressure leads to decreased drainage of normal spinal veins, venous congestion, and the clinical findings of progressive myelopathy. On MR imaging, the combination of cord edema, perimedullary dilated vessels, and cord enhancement is characteristic. Therapy has to be aimed at occluding the shunting zone, either by superselective embolization with a liquid embolic agent or by a neurosurgical approach. Following occlusion of the fistula, the progression of the disease can be stopped and improvement of symptoms is typically observed.

Conservation of notochord gene expression across chordates: insights from the Leprecan gene family

The notochord is a defining character of the chordates, and the T-box transcription factor Brachyury has been shown to be required for notochord development in all chordates examined. In the ascidian Ciona intestinalis, at least 44 notochord genes have been identified as bona fide transcriptional targets of Brachyury. We examined the embryonic expression of a subset of murine orthologs of Ciona Brachyury target genes in the notochord to assess its conservation throughout chordate evolution. We focused on analyzing the Leprecan gene family, which in mouse is composed of three genes, as opposed to the single-copy Ciona gene. We found that all three mouse Leprecan genes are expressed in the notochord. Additionally, while Leprecan expression in C. intestinalis is confined to the notochord, expression of its mouse orthologs includes dorsal root ganglia, limb buds, branchial arches, and developing kidneys. These results have interesting implications for the evolution and development of chordates.

Dural arteriovenous shunts: a new classification of craniospinal epidural venous anatomical bases and clinical correlations

BACKGROUND AND PURPOSE

The craniospinal epidural spaces can be categorized into 3 different compartments related to their specific drainage role of the bone and central nervous system, the ventral epidural, dorsal epidural, and lateral epidural groups. We propose this new classification system for dural arteriovenous shunts and compare demographic, angiographic, and clinical characteristics of dural arteriovenous shunts that develop in these 3 different locations.

METHODS

Three hundred consecutive cases (159 females, 141 males; mean age: 47 years; range, 0 to 87 years) were reviewed for patient demographics, clinical presentation, multiplicity, presence of cortical and spinal venous reflux, and outflow restrictions and classified into the 3 mentioned groups.

RESULTS

The ventral epidural group (n=150) showed a female predominance, more benign clinical presentations, lower rate of cortical and spinal venous reflux, and no cortical and spinal venous reflux without restriction of the venous outflow. The dorsal epidural group (n=67) had a lower mean age and a higher rate of multiplicity. The lateral epidural group (n=63) presented later in life with a male predominance, more aggressive clinical presentations, and cortical and spinal venous reflux without evidence of venous outflow restriction. All differences were statistically significant (P<0.001).

CONCLUSIONS

Dural arteriovenous shunts predictably drain either in pial veins or craniofugally depending on the compartment involved by the dural arteriovenous shunt. Associated conditions (outflow restrictions, high-flow shunts) may change that draining pattern. The significant differences between the groups of the new classification support the hypothesis of biological and/or developmental differences in each epidural region and suggest that dural arteriovenous shunts are a heterogeneous group of diseases.

The teleost intervertebral region acts as a growth center of the centrum: in vivo visualization of osteoblasts and their progenitors in transgenic fish

The vertebral column is a defined feature of vertebrates. In birds and mammals, the sclerotome yields cartilaginous material for the vertebral column. In teleosts, however, it remains uncertain whether the sclerotome participates in vertebral column formation. To investigate osteoblast development in the teleost, we established transgenic systems that allow in vivo observation of osteoblasts and their progenitors marked by fluorescence of DsRed and enhanced green fluorescent protein (EGFP), respectively. In twist-EGFP transgenic medaka, EGFP-positive cells first appeared in the ventromedial portion of respective somites corresponding to the sclerotome, migrated dorsally around the notochord, and concentrated in the intervertebral regions. Ultrastructural analysis of the intervertebral regions revealed that some of these cells were directly located on the osteoidal surface of the perichordal centrum, and enriched with rough endoplasmic reticulum in their cytoplasm. By using the double transgenic medaka of twist-EGFP and osteocalcin-DsRed, we clarified that the EGFP-positive cells in the intervertebral region differentiated into mature osteoblasts expressing the DsRed. In vivo bone labeling in fact confirmed active matrix formation and mineralization of the perichordal centrum exclusively in the intervertebral region of zebrafish larvae as well as medaka larvae. These findings strongly suggest that the teleost intervertebral region acts as a growth center of the perichordal centrum, where the sclerotome-derived cells differentiate into osteoblasts.

Apoptosis regulates notochord development in Xenopus

The notochord is the defining characteristic of the chordate embryo and plays critical roles as a signaling center and as the primitive skeleton. In this study we show that early notochord development in Xenopus embryos is regulated by apoptosis. We find apoptotic cells in the notochord beginning at the neural groove stage and increasing in number as the embryo develops. These dying cells are distributed in an anterior to posterior pattern that is correlated with notochord extension through vacuolization. In axial mesoderm explants, inhibition of this apoptosis causes the length of the notochord to approximately double compared to controls. In embryos, however, inhibition of apoptosis decreases the length of the notochord and it is severely kinked. This kinking also spreads from the anterior with developmental stage such that, by the tadpole stage, the notochord lacks any recognizable structure, although notochord markers are expressed in a normal temporal pattern. Extension of the somites and neural plate mirrors that of the notochord in these embryos, and the somites are severely disorganized. These data indicate that apoptosis is required for normal notochord development during the formation of the anterior-posterior axis, and its role in this process is discussed.

Molecular phenotypes of notochordal cells purified from immature nucleus pulposus

The immature nucleus pulposus (NP) is populated by cells of notochordal-origin that are larger and contain an extensive cytoskeletal network and numerous vacuoles. The disappearance of these cells with age is believed important in regulating metabolic shifts that may contribute to age-related disc degeneration. The precise biological function of these notochordal cells in the immature NP remains unclear, however, because of challenges in studying the mixed cell population in the NP. In this study, notochordal-like cells were purified from immature NP cells using a new fluorescence-activated cell sorting (FACS) protocol with auto-fluorescence and size analysis. The unique molecular phenotypes of sorted notochordal-like cells were characterized by the mRNA expression pattern for key matrix proteins and modulators, and by the expression of cell-matrix receptor integrin subunits. An FACS analysis showed that the immature NP contained a majority of cells that were larger than anulus fibrosus (AF) cells and with fluorescence higher than AF cells. In comparison with the small NP cells separated by the FACS protocol, sorted notochordal-like cells expressed lower mRNA levels of type I collagen, biglycan, TIMP1, HSP70 and c-fos, and did not express detectable mRNA levels of decorin, lumican, multiple MMPs or IL-1beta via real-time quantitative RT-PCR. A greater number of these notochordal-like cells also expressed the higher levels of alpha6, alpha1 and beta1 integrin subunits as compared to small NP cells. Together, our results point towards a unique molecular phenotype for these notochordal-like cells of NP, characterized by the absence of gene expression for specific small proteoglycans and higher protein expression of integrin subunits that regulate interactions with collagens and laminin. Future studies will be important for revealing if this unique molecular profile is coordinated with functional differences in pericellular matrix regions and/or integrin-mediated cell-matrix interactions for these notochordal-like cells within the NP.

A segmental pattern of alkaline phosphatase activity within the notochord coincides with the initial formation of the vertebral bodies

This study shows that segmental expression of alkaline phosphatase (ALP) activity by the notochord of the Atlantic salmon (Salmo salar L.) coincides with the initial mineralization of the vertebral body (chordacentrum), and precedes ALP expression by presumed somite-derived cells external to the notochordal sheath. The early expression of ALP indicates that the notochord plays an instructive role in the segmental patterning of the vertebral column. The chordacentra form segmentally as mineralized rings within the notochordal sheath, and ALP activity spreads within the chordoblast layer from ventral to dorsal, displaying the same progression and spatial distribution as the mineralization process. No ALP activity was observed in sclerotomal mesenchyme surrounding the notochordal sheath during initial formation of the chordacentra. Our results support previous findings indicating that the chordoblasts initiate a segmental differentiation of the notochordal sheath into chordacentra and intervertebral regions.