Spatiotemporal distribution of GAP-43 in the developing rat spinal cord: a histological and quantitative immunofluorescence study

Neuroprotective and Regenerative Effects of Growth Hormone (GH) in the Embryonic Chicken Cerebral Pallium Exposed to Hypoxic-Ischemic (HI) Injury

Prenatal hypoxic−ischemic (HI) injury inflicts severe damage on the developing brain provoked by a pathophysiological response that leads to neural structural lesions, synaptic loss, and neuronal death, which may result in a high risk of permanent neurological deficits or even newborn decease. It is known that growth hormone (GH) can act as a neurotrophic factor inducing neuroprotection, neurite growth, and synaptogenesis after HI injury. In this study we used the chicken embryo to develop both in vitro and in vivo models of prenatal HI injury in the cerebral pallium, which is the equivalent of brain cortex in mammals, to examine whether GH exerts neuroprotective and regenerative effects in this tissue and the putative mechanisms involved in these actions. For the in vitro experiments, pallial cell cultures obtained from chick embryos were incubated under HI conditions (<5% O2, 1 g/L glucose) for 24 h and treated with 10 nM GH, and then collected for analysis. For the in vivo experiments, chicken embryos (ED14) were injected in ovo with GH (2.25 µg), exposed to hypoxia (12% O2) for 6 h, and later the pallial tissue was obtained to perform the studies. Results show that GH exerted a clear anti-apoptotic effect and promoted cell survival and proliferation in HI-injured pallial neurons, in both in vitro and in vivo models. Neuroprotective actions of GH were associated with the activation of ERK1/2 and Bcl-2 signaling pathways. Remarkably, GH protected mature neurons that were particularly harmed by HI injury, but was also capable of stimulating neural precursors. In addition, GH stimulated restorative processes such as the number and length of neurite outgrowth and branching in HI-injured pallial neurons, and these effects were blocked by a specific GH antibody, thus indicating a direct action of GH. Furthermore, it was found that the local expression of several synaptogenic markers (NRXN1, NRXN3, GAP-43, and NLG1) and neurotrophic factors (GH, BDNF, NT-3, IGF-1, and BMP4) were increased after GH treatment during HI damage. Together, these results provide novel evidence supporting that GH exerts protective and restorative effects in brain pallium during prenatal HI injury, and these actions could be the result of a joint effect between GH and endogenous neurotrophic factors. Also, they encourage further research on the potential role of GH as a therapeutic complement in HI encephalopathy treatments.

Recursive Feature Elimination-based Biomarker Identification for Open Neural Tube Defects

Background: Open spina bifida (myelomeningocele) is the result of the failure of spinal cord closing completely and is the second most common and severe birth defect. Open neural tube defects are multifactorial, and the exact molecular mechanism of the pathogenesis is not clear due to disease complexity for which prenatal treatment options remain limited worldwide. Artificial intelligence techniques like machine learning tools have been increasingly used in precision diagnosis. Objective: The primary objective of this study is to identify key genes for open neural tube defects using a machine learning approach that provides additional information about myelomeningocele in order to obtain a more accurate diagnosis. Materials and Methods: Our study reports differential gene expression analysis from multiple datasets (GSE4182 and GSE101141) of amniotic fluid samples with open neural tube defects. The sample outliers in the datasets were detected using principal component analysis (PCA). We report a combination of the differential gene expression analysis with recursive feature elimination (RFE), a machine learning approach to get 4 key genes for open neural tube defects. The features selected were validated using five binary classifiers for diseased and healthy samples: Logistic Regression (LR), Decision tree classifier (DT), Support Vector Machine (SVM), Random Forest classifier (RF), and K-nearest neighbour (KNN) with 5-fold cross-validation. Results: Growth Associated Protein 43 (GAP43), Glial fibrillary acidic protein (GFAP), Repetin (RPTN), and CD44 are the important genes identified in the study. These genes are known to be involved in axon growth, astrocyte differentiation in the central nervous system, post-traumatic brain repair, neuroinflammation, and inflammation-linked neuronal injuries. These key genes represent a promising tool for further studies in the diagnosis and early detection of open neural tube defects. Conclusion: These key biomarkers help in the diagnosis and early detection of open neural tube defects, thus evaluating the progress and seriousness in diseases condition. This study strengthens previous literature sources of confirming these biomarkers linked with open NTD's. Thus, among other prenatal treatment options present until now, these biomarkers help in the early detection of open neural tube defects, which provides success in both treatment and prevention of these defects in the advanced stage.

Growth-associated protein 43 promotes thyroid cancer cell lines progression via epithelial-mesenchymal transition

Thyroid cancer is maintaining at a high incidence level and its carcinogenesis is mainly affected by a complex gene interaction. By analysis of the next‐generation resequencing of paired papillary thyroid cancer (PTC) and adjacent thyroid tissues, we found that Growth Associated Protein 43 (GAP43), a phosphoprotein activated by protein kinase C, might be novel markers associated with PTC. However, its function in thyroid carcinoma has been poorly understood. We discovered that GAP43 was significantly overexpressed in thyroid carcinoma and these results were consistent with that in The Cancer Genome Atlas (TCGA) cohort. In addition, some clinicopathological features of GAP43 in TCGA database showed that up‐regulated GAP43 is significantly connected to lymph node metastasis (P < 0.001) and tumour size (P = 0.038). In vitro experiments, loss of function experiments was performed to investigate GAP43 in PTC cell lines (TPC‐1 and BCPAP). The results proved that GAP43 knockdown in PTC cell significantly decreased the function of cell proliferation, colony formation, migration, and invasion and induced cell apoptosis. Furthermore, we also indicated that GAP43 could modulate the expression of epithelial‐mesenchymal transition‐related proteins, which could influence invasion and migration. Put those results together, GAP43 is a gene which was associated with PTC and might be a potential therapeutic target.

Changes and Significance of SYP and GAP-43 Expression in the Hippocampus of CIH Rats

Synaptophysin (SYP) and growth-associated binding protein 43 (GAP-43) have been shown to be closely related to hippocampal synaptic plasticity in recent years. They are important molecular markers associated with synaptic plasticity. However, the role of SYP and GAP-43 in chronic intermittent hypoxic injury of the central nervous system needs to be further clarified. In this study, 25 adult male sprague dawley (SD) rats were randomly divided into a normal control group (CON) and a chronic intermittent hypoxia group (CIH) with four time points as follows: 1 W, 2 W, 3 W, and 4 W. The behavioural changes (primarily learning and memory abilities) were observed by the Morris water maze in each group, consisting of 5 rats per group.The localization of SYP and GAP-43 in hippocampal CA1 neurons was observed, and the expression of SYP and GAP-43 in the hippocampus was detected by Western blotting. The results showed that the mean oxygen saturation of the tail artery in CIH rats was less than that in normal rats (P < 0.05). The escape latency of CIH rats was longer than that of normal rats, and the number of space exploration platform crossings was less than that of normal rats. SYP-positive stained cells were yellow or brown and were mainly expressed on the cell membrane, while the GAP-43-positive staining was brown and was mainly expressed on the cell membrane and in the cytoplasm. The expression of SYP in plasma decreased gradually at the four time points for the CIH group (P < 0.05), while the expression of GAP-43 in the CIH 1W group increased (P < 0.05) and decreased gradually in the CIH 2 W, CIH 3 W and CIH 4 W groups (P < 0.05).

GAP43, a novel metastasis promoter in non-small cell lung cancer

BACKGROUND

Brain metastasis is an extremely serious sequela with a dismal prognosis in non-small cell lung cancer (NSCLC). The present study aimed to identify novel biomarkers and potential therapeutic targets for brain metastases of NSCLC.

METHODS

We performed high-throughput Luminex assays to profile the transcriptional levels of 36 genes in 70 operable NSCLC patients, among whom 37 developed brain metastases as the first relapse within 3 years after surgery. The Cox proportional hazards regression model was used to evaluate the association between genes and brain metastases. Wound healing assay and transwell assay was carried out to estimate the function of target gene in vitro. And left ventricular injection on nude mice was used to evaluate the effect of target gene in vivo.

RESULTS

Growth-associated protein 43 (GAP43) was found to be related to brain metastasis. Multivariate Cox regression analysis showed that NSCLC patients with elevated GAP43 had a 3.29-fold increase in the risk for brain metastasis compared with those with low levels (95% confidence interval: 1.55-7.00; P = 0.002). Kaplan-Meier survival curves revealed that GAP43 was also associated with overall survival. Analysis of a cohort of 1926 NSCLC patients showed similar results: patients with high levels of GAP43 had worse progression-free and overall survival rates. Furthermore, in vitro experiments showed that GAP43 facilitated cell migration. Animal studies demonstrated that GAP43-silenced NSCLC cells were less likely to metastasize to the brain and bone than control cells. Immunofluorescence and F-actin/G-actin in vivo assays indicated that GAP43 knockdown triggered depolymerization of the F-actin cytoskeleton. Rho GTPase activation assays showed that Rac1 was deactivated after GAP43 was silenced.

CONCLUSIONS

Our findings suggest that GAP43 is an independent predictor of NSCLC brain metastasis and that it may facilitate metastasis by regulating the Rac1/F-actin pathway.

Combined application of Rho-ROCKII and GSK-3β inhibitors exerts an improved protective effect on axonal regeneration in rats with spinal cord injury

Previous studies have reported that the Rho-associated coiled-coil containing protein kinase 2 (ROCKII) and glycogen synthase kinase-3β (GSK)-3β signaling pathways are involved in axonal regeneration. The present study investigated the effects of the combined application of Y27632 (a ROCKII inhibitor) and 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8; a GSK-3β inhibitor) on neurite outgrowth and functional recovery in rats with spinal cord injury (SCI). A total of 90 female Sprague-Dawley rats were randomly allocated into six groups, and the SCI rats received daily administration of 1.6 mg/kg Y27632 for 2 weeks and/or 1 mg/kg TDZD-8 for 3 weeks via a catheter. Cellular apoptosis in the injured spinal cords was measured at each time point using a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. The expression levels of growth-associated protein-43 (GAP-43) were determined by immunohistochemical staining. In addition, an anterograde tracer was used to analyze axonal regeneration, the Basso Beattie Bresnahan locomotor rating scale (BBB) was analyzed, and the somatosensory evoked potential (SEP) test was conducted. The results demonstrated that SCI upregulated the number of apoptotic cells, increased GAP-43 expression and enhanced the latent periods of SEP, as compared with in mice that underwent a sham operation. Furthermore, SCI decreased the BBB scores and the SEP amplitudes. These injuries in the spinal cord were reduced following treatment with Y27632, TDZD-8, or their combined application, as detected by decreased apoptosis, the induction of axonal regeneration, and the promotion of functional recovery of the lower limbs. Although the BBB scores, and SEP amplitudes and latent periods were not significantly different among the three drug treatment groups, the combined application of Y27632 and TDZD-8 resulted in stronger axonal regenerative potency and a greater protective effect on secondary SCI. These results indicated that the combined application of Y27632 and TDZD-8 may more effectively protect against secondary SCI by inhibiting cellular apoptosis, enhancing GAP-43 expression and promoting neurite outgrowth in SCI rats, compared with Y27632 or TDZD-8 alone.

The Corticospinal System: From Development to Motor Control

The corticospinal system is the principal motor system for controlling movements that require the greatest skill and flexibility. It is the last motor system to develop. The pattern of termination of corticospinal axons, as they grow into the spinal gray matter, bears little resemblance to the pattern later in development and in maturity. Refinement of corticospinal terminations occurs during a protracted postnatal period and includes both elimination of transient terminations and growth to new targets. This refinement is driven by neural activity in the motor cortical areas and by limb motor experience. Developing corticospinal terminals compete with each other for synaptic space on spinal neurons. More active terminals are more competitive and are able to secure more synaptic space than their less active counterparts. Corticospinal terminals can activate spinal neurons from very early in development. The importance of this early synaptic activity appears to be more for refining corticospinal connections than for transmitting signals to spinal motor circuits for movement control. The motor control functions of the corticospinal system are not expressed until development of connectional specificity with spinal cord neurons, a strong capacity for corticospinal synapses to facilitate spinal motor circuits, and the formation of the cortical motor map.

Anterior Corticospinal Tract Revisited: A Study Using Human Fetuses

In the human corticospinal tract (CST), the anterior CST is known to be much thinner than the lateral CST, but fetal development of the CST remains obscure. In this study, we examined horizontal histological sections of the cervical spinal cord from 50 midterm fetuses (crown-rump length, CRL, 70-150 mm; 12-18 weeks) as well as 15 late-stage fetuses (CRL 230-250 mm; 28-30 weeks). While the lateral CST appeared at 14-15 weeks in the cervical cord of the midterm fetuses, we found the anterior CST in only 3 fetuses: CRL 117 mm (15 weeks), and CRL 144 and 150 mm (18 weeks). However, in the late-stage fetuses, the anterior CST exhibited a spectrum of variations, including bilaterally thick tracts (3 fetuses), a unilaterally thick tract (5 fetuses) and a thin or absent tract (7 fetuses). In the group with the thickest anterior CST, the cross-sectional area reached 40% of that of the lateral CST. In contrast to the stable morphology of the lateral CST, the shape of the anterior tract varied slightly between the cervical segments. Immunohistochemical observations demonstrated no difference between the lateral and anterior CSTs: (1) in macrophage infiltration, which suggests apoptosis, and (2) in the arrangement of radial glial fibers. Our findings indicate that the development of the anterior CST starts later than that of the lateral tract, with significant individual variations. The functional relevance of the anterior CST, if present, might not be found in an independent cortical input to motor neurons but in a remodeling of the ascending tracts.

Influence of chronic intermittent hypoxia on growth associated protein 43 expression in the hippocampus of young rats

This study aimed to explore the pathological change to hippocampal neurons and the expression of growth associated protein 43 in 21-day-old young rats following chronic intermittent hypoxia. Hematoxylin-eosin staining results showed varying degrees of degeneration and necrosis in hippocampal neurons depending on the modeling time. Immunohistochemistry revealed that growth associated protein 43 expression in young rats following chronic intermittent hypoxia decreased, but that levels were still higher than those of normal rats at each time point, especially 4 weeks after modeling. During 1–5 weeks after modeling, a slow growth in rat weight was observed. Experimental findings indicate that chronic intermittent hypoxia may induce growth dysfunction and necrosis of hippocampal neurons, as well as increase the expression of growth associated protein 43 in young rats.

GAP-43 dependency defines distinct effects of netrin-1 on cortical and spinal neurite outgrowth and directional guidance

Growth-associated protein-43 (GAP-43) is a major nervous system protein whose phosphorylation by protein kinase C regulates growth cone responses to extracellular guidance cues via F-actin. GAP-43 is essential for axon pathfinding in both cortical afferents and efferents: when it is genetically deleted, somatosensory, auditory and visual somatotopic maps fail to form, and telencephalic commissural axons fail to cross the midline. Here we investigated whether the midline guidance cue netrin-1 depends on GAP-43 for its functions in neurite growth and guidance. We used 3-dimensional collagen gel co-cultures to show that both endogenous netrin-1, expressed by the spinal cord floor plate, and recombinant netrin-1, expressed by transfected COS7 cells, stimulate neurite outgrowth and chemotropic guidance of neocortical callosal axons. In contrast both were significantly inhibited in GAP-43 (-/-) neocortical callosal axons, mimicking the in vivo phenotype. Conversely, neither netrin-1-stimulated neurite outgrowth nor guidance of dorsal spinal cord commissure axons were affected when GAP-43 was absent, again consistent with in vivo phenotype but suggesting fundamental differences in how neocortical and spinal cord axons respond to netrin-1. In addition, differences in GAP-43 dependency also distinguished how ventrolateral cortical efferents respond to netrin-1: in contrast to callosal neurites, in which netrin-1 required GAP-43 in order to stimulate both outgrowth and guidance, in ventrolateral efferents, netrin-1 required GAP-43 only to stimulate outgrowth, but not guidance. Moreover, netrin-1 increased the numbers of both types of cortical, but not spinal neurites. The results demonstrate previously unappreciated diversity in how different classes of neurons respond to the same guidance cue.

New bioactive motifs and their use in functionalized self-assembling peptides for NSC differentiation and neural tissue engineering

Developing functionalized biomaterials for enhancing transplanted cell engraftment in vivo and stimulating the regeneration of injured tissues requires a multi-disciplinary approach customized for the tissue to be regenerated. In particular, nervous tissue engineering may take a great advantage from the discovery of novel functional motifs fostering transplanted stem cell engraftment and nervous fiber regeneration. Using phage display technology we have discovered new peptide sequences that bind to murine neural stem cell (NSC)-derived neural precursor cells (NPCs), and promote their viability and differentiation in vitro when linked to LDLK12 self-assembling peptide (SAPeptide). We characterized the newly functionalized LDLK12 SAPeptides via atomic force microscopy, circular dichroism and rheology, obtaining nanostructured hydrogels that support human and murine NSC proliferation and differentiation in vitro. One functionalized SAPeptide (Ac-FAQ), showing the highest stem cell viability and neural differentiation in vitro, was finally tested in acute contusive spinal cord injury in rats, where it fostered nervous tissue regrowth and improved locomotor recovery. Interestingly, animals treated with the non-functionalized LDLK12 had an axon sprouting/regeneration intermediate between Ac-FAQ-treated animals and controls. These results suggest that hydrogels functionalized with phage-derived peptides may constitute promising biomimetic scaffolds for in vitro NSC differentiation, as well as regenerative therapy of the injured nervous system. Moreover, this multi-disciplinary approach can be used to customize SAPeptides for other specific tissue engineering applications.

Evaluation of early and late effects into the acute spinal cord injury of an injectable functionalized self-assembling scaffold

The complex physiopathological events occurring after spinal cord injury (SCI) make this devastating trauma still incurable. Self-assembling peptides (SAPs) are nanomaterials displaying some appealing properties for application in regenerative medicine because they mimic the structure of the extra-cellular matrix (ECM), are reabsorbable, allow biofunctionalizations and can be injected directly into the lesion. In this study we evaluated the putative neurorigenerative properties of RADA16-4G-BMHP1 SAP, proved to enhance in vitro neural stem cells survival and differentiation. This SAP (RADA16-I) has been functionalized with a bone marrow homing motif (BMHP1) and optimized via the insertion of a 4-glycine-spacer that ameliorates scaffold stability and exposure of the biomotifs. We injected the scaffold immediately after contusion in the rat spinal cord, then we evaluated the early effects by semi-quantitative RT-PCR and the late effects by histological analysis. Locomotor recovery over 8 weeks was assessed using Basso, Beattie, Bresnahan (BBB) test. Gene expression analysis showed that at 7 days after lesion the functionalized SAP induced a general upregulation of GAP-43, trophic factors and ECM remodelling proteins, whereas 3 days after SCI no remarkable changes were observed. Hystological analysis revealed that 8 weeks after SCI our scaffold increased cellular infiltration, basement membrane deposition and axon regeneration/sprouting within the cyst. Moreover the functionalized SAP showed to be compatible with the surrounding nervous tissue and to at least partially fill the cavities. Finally SAP injection resulted in a statistically significant improvement of both hindlimbs' motor performance and forelimbs-hindlimbs coordination. Altogether, these results indicate that RADA16-4G-BMHP1 induced favourable reparative processes, such as matrix remodelling, and provided a physical and trophic support to nervous tissue ingrowth. Thus this biomaterial, eventually combined with cells and growth factors, may constitute a promising biomimetic scaffold for regenerative applications in the injured central nervous system.

Early profiles of axonal growth and astroglial response after spinal cord hemisection and implantation of Schwann cell-seeded guidance channels in adult rats

We previously demonstrated that transplantation of Schwann cell-seeded channels promoted the regrowth of injured axons in the adult spinal cord. It is not clear, however, whether injured axons recapitulate the developmental scenarios to accomplish regeneration. In the present study, we investigated the early events associated with axonal regrowth after spinal cord hemisection at the eighth thoracic level and implantation of a Schwann cell-seeded minichannel in adult rats. Animals were sacrificed at postoperative days (PO) 2, 4, 7, and 14. Anterograde tracing with fluoro-ruby showed that regenerating axons grew into the graft prior to PO2 and reached the distal end of the channel at PO7. These axons expressed both embryonic neural cell adhesion molecule (E-NCAM) and growth associated protein-43 (GAP-43). Although the expression of E-NCAM decreased by PO7, that of GAP-43 remained high throughout the first 2 weeks after implantation. A close relation of vimentin-positive astroglia to the growing axons in the host tissue suggested a contact-mediated role of these cells in axon guidance. Aggregation of glial fibrillary acidic protein (GFAP)-positive astrocytes together with the increased expression of chondroitin sulfate proteoglycans (CSPGs) starting at PO7 appeared to inhibit axonal growth at the host-graft interface. Thus, adult regenerating axons and astroglia do express developmentally related molecules that may facilitate axonal growth into a permissive graft at the early phase of injury and regeneration. These results suggest that molecules and astroglia essential to development are both important in influencing axonal regrowth in the adult spinal cord.

Temporal and spatial distribution of growth-associated molecules and astroglial cells in the rat corticospinal tract during development

To understand better the role of growth-promoting and -inhibiting molecules in the development of the corticospinal tract (CST), temporospatial expression of embryonic neural cell adhesion molecule (E-NCAM), growth-associated protein-43 (GAP-43), and chondroitin sulfate proteoglycan (CSPG) was studied in developing rats. Transverse sections of the seventh cervical (C7), seventh thoracic (T7), and fourth lumbar (L4) segments were examined at postnatal days (P) 2, 6, 10, 14, and 28. The highest E-NCAM immunoreactivity appeared at the C7 level on P2 and shifted caudally to the T7 on P6 and L4 on P10, which correlated closely with the time course of CST development. The peak expression of GAP-43 emerged at C7 on P2 and shifted to the T7 and L4 levels at a relatively lagging pace compared with that of E-NCAM. Conversely, a transient reduction in CSPG immunoreactivity was found within the CST at the C7 level on P2, T7 level on P6, and L4 level on P10, corresponding well with the arrival of CST-leading axons at these levels. Interestingly, higher levels of CSPG were found to surround the growing CST, suggesting a repulsive environment that channels the growth of CST. Moreover, a transition from immature to mature astrocytes in a rostrocaudal direction during CST development was evidenced by anti-vimentin and anti-glial fibrillary acidic protein (GFAP) immunostaining, suggesting a guidance role of immature astroglia in axonal outgrowth. Our study thus demonstrated dynamic changes of multiple growth-related molecules and astroglial environment that contribute to postnatal development of the CST.

Neuronal plasticity after spinal cord injury: identification of a gene cluster driving neurite outgrowth

Functional recovery after spinal cord injury (SCI) may result in part from axon outgrowth and related plasticity through coordinated changes at the molecular level. We employed microarray analysis to identify a subset of genes the expression patterns of which were temporally coregulated and correlated to functional recovery after SCI. Steady-state mRNA levels of this synchronously regulated gene cluster were depressed in both ventral and dorsal horn neurons within 24 h after injury, followed by strong re-induction during the following 2 wk, which paralleled functional recovery. The identified cluster includes neuritin, attractin, microtubule-associated protein 1a, and myelin oligodendrocyte protein genes. Transcriptional and protein regulation of this novel gene cluster was also evaluated in spinal cord tissue and in single neurons and was shown to play a role in axonal plasticity. Finally, in vitro transfection experiments in primary dorsal root ganglion cells showed that cluster members act synergistically to drive neurite outgrowth.

Secretion of tenascin-C by cultured astrocytes: regulation of cell proliferation and process elongation

Tenascin-C (TNC), an extracellular matrix glycoprotein, is involved in tissue morphogenesis like embryogenesis, wound healing or tumorigenesis. Quiescent astroglia in long-term primary cultures are known to show rapid morphological changes after subculture and serum deprivation/re-addition (SSDR). To elucidate roles of TNC in the morphogenetic processes of cultured astrocytes, we have revealed morphological changes in association with soluble TNC contents in the medium and expression of TNC mRNA, TNC, glial fibrillary acidic protein (GFAP) and integrin beta1, one of its cell surface receptors, in glial cells after SSDR. Soluble TNC in the medium rapidly increased in amount at 4 h when GFAP-positive cells expressed TNC mRNA, TNC and integrin beta1. Cellular proliferation and growth occurred in colonies expressing TNC mRNA, TNC and integrin beta1 during the first 24 h. During the next 24 h, process elongation and cell migration occurred in association with increased GFAP expression and re-elevation of soluble TNC in the medium. Cell bodies became flat and larger with increased GFAP and reduced TNC expression at 72 h, while cultures became confluent with reduced GFAP and TNC expression at 96 h after SSDR. Functional blocking with anti-TNC antibody reduced cell proliferation and induced morphological change from a process-bearing slender shape to a flat and wide shape presumably due to increased cell adhesion. These findings strongly support the idea that endogenous TNC produced and released by astrocytes in response to serum stimulation induces their proliferation and process elongation through a paracrine/autocrine mechanism.

Spatiotemporal distribution of neuronal calcium sensor-1 in the developing rat spinal cord

The present study revealed the localization of neuronal calcium sensor (NCS)-1 immunoreactivity (IR) in the developing rat spinal cord. The NCS-1 IR first appeared at embryonic day 12 in the peripheral nerves and their somata. Intense NCS-1 IR was expressed in ascending and descending tracts in the white matter during the late prenatal period, which gradually decreased to the faint level during postnatal development. Intense NCS-1 IR was colocalized with growth associated protein (GAP)-43 IR in the marginal zone and with the glutamate-aspartate transporter (GLAST) IR in the radial processes traversing the marginal zone. In the adult rat white matter, radially oriented astrocytes and astrocytes in the glia limitans were double-labeled for NCS-1 and glial fibrillary acidic protein (GFAP), whereas small dots on finger-like dendritic projections were double-labeled for NCS-1 and synaptophysin. In the developing gray matter, the NCS-1 IR appeared at embryonic day 12 and gradually increased in the neuronal somata and neuropil, reaching a plateau after the end of the 4th postnatal week. The small dots in neuropil were colabeled for NCS-1 and GFAP or NCS-1 and synaptophysin in the adult rat gray matter. These results strongly suggest that NCS-1 is involved in axogenesis and synaptogenesis in the developing rat spinal cord. NCS-1 can serve as a Ca(2+)-sensor not only in neurons but also in radial glial cells or even in radially oriented astrocytes in the adult rat spinal cord.

Ependymal cell reactions in spinal cord segments after compression injury in adult rat

Recently, it has been suggested that neural stem cells and neural progenitor cells exist in the ependyma that forms the central canal of the spinal cord. In this study, we produced various degrees of thoracic cord injury in adult rats using an NYU-weight-drop device, assessed the degree of recovery of lower limb motor function based on a locomotor rating scale, and analyzed the kinetics of ependymal cell proliferation and differentiation by proliferating cell nuclear antigen (PCNA), nestin, glial fibrillary acidic protein (GFAP), or GAP-43 immunostaining. The results showed that the time course of the ependymal cell proliferation and differentiation reactions differed according to the severity of injury, and that the responses occurred not only in the neighborhood of the injury but in the entire spinal cord. An increase in the locomotor rating score was related to an increase in the number of PCNA-positive cells, and the differentiation of ependymal cells into reactive astrocytes was involved in injury repair. No apoptotic cells in the ependyma were detectable by the TUNEL method. These results indicate that the ependymal cells of the spinal central canal are themselves multipotent, can divide and proliferate according to the severity of injury, and differentiate into reactive astrocytes within the ependyma without undergoing apoptosis or cell death.

Development of the regenerative capacity of postnatal axotomized rat spinal motoneurons

The present study examined whether a peripheral nerve (PN) graft can rescue developing motoneurons from degeneration and determined when immature motoneurons begin to express a regenerative capacity. Transplantation of a PN graft was unable to rescue motoneurons from degeneration if spinal root avulsion was performed in animals younger than P14. However, this procedure did enhance motoneuron survival when root avulsion was performed at P14 or later. Immature (P1 or P7) motoneurons were unable to regenerate their axons into the transplanted PN graft following root avulsion, whereas in older animals (P14-P28) motoneurons were able to regenerate axons into the PN graft. The percentage of regenerated motoneurons increased from P21 to P28 and was similar to that of adult animals. Therefore, the regenerative capacity of rat spinal motoneurons first begins at about P14, which seems to be critical.