Adjuvant chemotherapy for elderly patients (aged 70 or older) with gastric cancer after a gastrectomy with D2 dissection: A single center experience in Korea.

AIMS: Adjuvant chemotherapy is recommended for gastric cancer after a gastrectomy with D2 dissection. However, its survival benefit in elderly patients is unclear. Here we investigated the use of adjuvant chemotherapy in patients ≥70 years old with stage II or III gastric cancer. METHODS: Patients ≥70 years old diagnosed with stage II or III gastric cancer at Ulsan University Hospital were identified. A retrospective analysis of electronic and paper patient records was performed. RESULTS: From 2008 to 2012, 277 patients ≥70 years old underwent gastrectomy with D2 dissection. Of these patients, 94 were pathologically diagnosed with stage II or III; 55 of these patients (58.5%) received adjuvant chemotherapy and 39 received regular checkups without chemotherapy. Fluoropyrimidine-alone regimens, including TS-1 composed of tegafur, gimestat and otastat potassium (n = 26) and doxifluridine (n = 22), were more commonly used than fluoropyrimidine-platinum combination regimens (n = 7). With a median follow-up of 30.9 (range 0.8-65.5) months, the median relapse-free survival of patients with adjuvant chemotherapy or regular follow-up only was 35.5 and 20.4 months, respectively (P = 0.030). Multivariate analysis revealed that adjuvant chemotherapy is associated with longer relapse-free survival (hazard ratio 0.50; 95% confidence interval 0.27-0.96). There was a trend toward an improved overall survival in the adjuvant chemotherapy group compared with the follow-up only group (P = 0.242). CONCLUSIONS: Although well-designed prospective studies are required, adjuvant chemotherapy may confer a potential survival benefit in elderly patients (aged 70 or older) with stage II or III gastric cancer after a gastrectomy with D2 dissection.

The efficacy of steroids for edema and ecchymosis after rhinoplasty: a meta-analysis.

OBJECTIVES: Postoperative periorbital edema and ecchymosis following rhinoplasty can result in dissatisfaction for both the surgeon and the patient. The goal of this study was to perform a systematic review of the literature on the efficacy of steroids on edema and ecchymosis during rhinoplasty. DATA SOURCES: MEDLINE, SCOPUS, and Cochrane database. REVIEW METHODS: Two authors independently searched the databases from their inception of article collection to February 2014. Studies comparing perioperative steroid administration (steroid group) with no treatment (control group) where the outcomes of interest were edema and ecchymosis on postoperative days were included in the analysis. Overall, a total of nine trials met the inclusion criteria of this study, with a total sample size of 312 patients. RESULTS: The lower and upper eyelid edema during the 7 days postoperatively was statistically decreased in the steroid group versus control group. The lower and upper eyelid ecchymosis in the steroid group was significantly decreased in comparison to the control group for the first 4 days follow surgery. Regarding the outcome comparison between single-dose and multiple-dose administration of steroids, the multiple-dose administration decreased edema and ecchymosis significantly compared to single-dose administration after the fourth day. CONCLUSIONS: Perioperative administration of steroid during rhinoplasty could reduce the level of edema and eyelid ecchymosis. Multiple-dose administration of steroids has more advantages in terms of the outcomes of late postoperative edema and ecchymosis compared to a single-dose regimen.

Role of toll-like receptor 2 in ischemic demyelination and oligodendrocyte death.

White matter is frequently involved in ischemic stroke, and progressive ischemic white matter injuries are associated with various neurologic dysfunctions in the elderly population. Demyelination and oligodendrocyte (OL) loss are prominent features of ischemic white matter injury. Endothelin-1 injection into the internal capsule resulted in a localized demyelinating lesion in mice, where loss of OL lineage cells and inflammatory cell infiltration were observed accompanied by upregulation of toll-like receptor 2 (TLR2). Intriguingly, the extent of demyelinating pathology was markedly larger in TLR2 deficient mice than that of wild-type (WT) mice. TLR2 deficient mice showed enhanced OL death and decreased phosphorylation of ERK1/2 compared with WT animals. Cultured OLs from TLR2 deficient mice were more vulnerable to oxygen-glucose deprivation than WT OLs. Applying TLR2 agonists Pam3CSK4 or Zymosan after oxygen-glucose deprivation substantially rescued WT OL death with augmentation of ERK1/2 phosphorylation. Treatment with Pam3CSK4 also reduced the extent of endothelin-1 induced ischemic demyelination in vivo. Our data indicate TLR2 may provide endogenous protective effects on ischemic demyelination and OL degeneration.

Spatial and temporal correlation in progressive degeneration of neurons and astrocytes in contusion-induced spinal cord injury.

BACKGROUND: Traumatic spinal cord injury (SCI) causes acute neuronal death followed by delayed secondary neuronal damage. However, little is known about how microenvironment regulating cells such as microglia, astrocytes, and blood inflammatory cells behave in early SCI states and how they contribute to delayed neuronal death. METHODS: We analyzed the behavior of neurons and microenvironment regulating cells using a contusion-induced SCI model, examining early (3-6 h) to late times (14 d) after the injury. RESULTS: At the penumbra region close to the damaged core (P1) neurons and astrocytes underwent death in a similar spatial and temporal pattern: both neurons and astrocytes died in the medial and ventral regions of the gray matter between 12 to 24 h after SCI. Furthermore, mRNA and protein levels of transporters of glutamate (GLT-1) and potassium (Kir4.1), functional markers of astrocytes, decreased at about the times that delayed neuronal death occurred. However, at P1 region, ramified Iba-1+ resident microglia died earlier (3 to 6 h) than neurons (12 to 24 h), and at the penumbra region farther from the damaged core (P2), neurons were healthy where microglia were morphologically activated. In addition, round Iba-1/CD45-double positive monocyte-like cells appeared after neurons had died, and expressed phagocytic markers, including mannose receptors, but rarely expressed proinflammatory mediators. CONCLUSION: Loss of astrocyte function may be more critical for delayed neuronal death than microglial activation and monocyte infiltration.

PlexinA2 limits recovery from corticospinal axotomy by mediating oligodendrocyte-derived Sema6A growth inhibition.

Axonal growth from both intact and severed fibers is limited after adult mammalian CNS injury. Myelin proteins contribute to inhibition of axonal growth. Semaphorin6A protein inhibits the extension of developing axons and is highly expressed in adult oligodendrocytes. This expression pattern suggests that a developmental axon guidance cue contributes to the restriction of adult CNS growth. Here, we assessed the role of a Sema6A receptor, PlexinA2, in recovery from adult trauma. Adult sensory neuron inhibition by Sema6A requires PlexinA2, with complete protection in PlexinA2-/- cultures. Mice lacking another myelin inhibitor receptor, NgR1, are known to exhibit greater axonal sprouting and functional recovery after lesions of the corticospinal tract at the medullary pyramid, so we investigated PlexinA2 in this lesion. Without injury, the corticofugal projection into the cervical spinal cord is normal in adult PlexinA2 null mice. After unilateral pyramidotomy, unlesioned PlexinA2-/- corticospinal fibers sprout across the midline to innervate the contralateral gray matter of the spinal cord to a significantly greater extent than do fibers in wild type mice. Sprouted fibers display frequent synaptophysin-positive synaptic puncta. The increased axonal growth in PlexinA2-/- mice after injury is accompanied by improved behavioral recovery in a pellet retrieval task using the impaired forelimb, and in a tape removal task. Thus, PlexinA2, as a receptor for oligodendrocyte-derived Sema6A and for secreted class 3 Semaphorins, plays a role in limiting adult axon growth and recovery after trauma.

Vimentin phosphorylation by Cdc2 in Schwann cell controls axon growth via ß1-integrin activation.

Although preconditioning injury on the peripheral nerve induces axonal regenerative capacity in neurons, it is not known whether similar lesion effects occur in glial cells. Here we demonstrate that Schwann cells are activated by peripheral nerve preinjury and primed to mediate axon regeneration. Cdc2, which was induced from Schwann cells after sciatic nerve injury, phosphorylated vimentin almost exclusively in the distal nerve area. Phospho-vimentin-positive Schwann cells showed increased migration activity and were in close contact with process outgrowth of co-cultured neurons. Vimentin phosphorylation by Cdc2 was involved in ß1-integrin activation leading to FAK phoshorylation and associated with Erk1/2 activation in Schwann cells. Neurite outgrowth of dorsal root ganglion neurons was increased by co-culture with activated Schwann cells, in which phospho-vimentin signaling was transmitted into ß1-integrin activation. Then neurite outgrowth was suppressed by genetic depletion of phospho-vimentin and ß1 integrin as well as inhibition of vimentin phosphorylation by Cdc2 inhibitor purvalanol A. The sciatic nerve graft harboring activated Schwann cells into the spinal cord induced Schwann cell migration beyond the graft-host barrier and facilitated regeneration of spinal axons, which was inhibited by purvalanol A pretreatment of the graft. This is the first report to our knowledge demonstrating that activation of phospho-vimentin linked to ß1-integrin pathway may mediate transcellular signaling to promote axon growth.

Hepatocyte growth factor reduces astrocytic scar formation and promotes axonal growth beyond glial scars after spinal cord injury.

The formation of glial scars impedes growth of regenerating axons after CNS injuries such as spinal cord injury (SCI). Hepatocyte growth factor (HGF), originally identified as a mitogen for hepatocytes, exerts pleiotropic functions in the nervous system. HGF has been implicated in peripheral wound healing via regulation of the transforming growth factor beta (TGFß), which is also a potent inducer of glial scar formation in CNS. In the present study, we found that HGF completely blocked secretion of TGFß1 and ß2 from activated astrocytes in culture. HGF also prevented expression of specific chondroitin sulfate proteoglycan (CSPG) species. To determine whether HGF inhibits glial scar formation in an in vivo SCI model, HGF overexpressing mesenchymal stem cells (HGF-MSCs) were transplanted into hemisection spinal cord lesions at C4. Transplantation of HGF-MSCs markedly diminished TGFß isoform levels and reduced the extent of astrocytic activation. In addition, HGF-MSCs also significantly decreased neurocan expression and glycosaminoglycan chain deposition around hemisection lesions. Furthermore, animals treated with HGF-MSCs showed increased axonal growth beyond glial scars and improvement in recovery of forepaw function. Our results indicate that anti-glial scar effects of HGF, together with its known neurotrophic functions, could be utilized to ameliorate functional deficits following SCI.

Gene transfer mediated by stem cell grafts to treat CNS injury.

INTRODUCTION: Stem cell transplantation holds promise for promoting anatomical repair and functional recovery after traumatic or ischemic injuries to the CNS. Harnessing stem cells with therapeutic genes of interest is regarded as an attractive approach to augment therapeutic benefits of stem cell grafts. AREAS COVERED: The advantage of stem-cell-mediated gene transfer is the engraftibility of stem cells that can ensure a long-term and stable expression of therapeutic genes. In addition, stem-cell-gene interaction may synergistically amplify therapeutic benefits. Delivery of classical neurotrophic factor genes provided neuroprotective and pro-regenerative effects in various injury models. Some studies employed therapeutic genes targeting post-injury microenvironment to support endogenous repair. Recent trials of stem-cell-mediated transfer of nonclassical growth factors showed relatively novel biological effects. Combinatorial strategies seem to have the potential to improve therapeutic efficacy. EXPERT OPINION: Future development of induced pluripotent stem cells and novel scaffolding biomaterials will greatly expedite the advances in ex vivo gene therapy to treat CNS injury. Before moving to a clinical stage, rigorous preclinical evaluations are needed to identify an optimal gene or gene combination in different injury settings. Improving the safety of viral vectors will be a critical prerequisite for the clinical translation.

Differential and cooperative actions of Olig1 and Olig2 transcription factors on immature proliferating cells after contusive spinal cord injury.

Spontaneous remyelination after spinal cord injury (SCI) is limited probably due to inadequate signaling to generate sufficient OLs from progenitor cells. The present study tested a hypothesis that introduction of olig genes, critical regulators of OL development, into immature proliferating cells could increase oligodendrogenesis after contusive SCI in adult rats. Recombinant retroviruses encoding Olig1 and Olig2 transcription factors, separately or in combination, with green fluorescent protein (GFP) were injected into the injured spinal cord. Unexpectedly, introduction of Olig2-GFP retroviruses led to a marked hyperplasia of GFP+ cells at 1 week, and soft agar colony forming assay of isolated GFP+ cells confirmed Olig2-induced tumorous transformation. In contrast, Olig1 did not alter the number of GFP+ cells. Simultaneous expression of Olig1 and Olig2 (Olig1/2) led to a marked increase in the number of GFP+ cells without tumor formation. The proportion of GFP+ cells with OL progenitor markers was increased by Olig1/2. Moreover, Olig1/2 robustly increased the proportion of mature OLs and expression of myelin related proteins, while Olig1 alone exhibited only modest effects. Olig1/2 upregulated Sox10, which drives terminal OL differentiation, implicating Sox 10 as a mediator of Olig1/2 effects on the maturation. Finally, injection of Olig1/2 retroviruses significantly improved a quality of hindpaws locomotion and increased the total number of OLs after SCI. Activation of both Olig1 and Olig2 may be beneficial by both increasing the progenitor cell proliferation and enhancing OL differentiation in the injured spinal cord.

A multi-domain fragment of Nogo-A protein is a potent inhibitor of cortical axon regeneration via Nogo receptor 1.

Nogo-A limits axon regeneration and functional recovery after central nervous system injury in adult mammals. Three regions of Nogo-A (Nogo-A-24, Nogo-66, and Nogo-C39) interact with the neuronal Nogo-66 receptor 1 (NgR1). Nogo-66 also interacts with a structurally unrelated cell surface receptor, paired immunoglobulin-like receptor (PirB). We show here that the other two NgR1-interacting domains, Nogo-A-24 and Nogo-C39, also bind to PirB with high affinity. A purified 22-kDa protein containing all three NgR1- and PirB-interacting domains (Nogo-22) is a substantially more potent growth cone-collapsing molecule than Nogo-66 for chick dorsal root ganglion neurons and mature cortical neurons. Moreover, Nogo-22 inhibits axon regeneration of mature cortical neurons in vitro more potently than does Nogo-66. Although all three NgR1-interacting domains of Nogo-A also interact with PirB, expression of PirB in mature cortical cultures is nearly undetectable. Consistent with a relatively minor role for PirB in mature cortical neurons, Nogo-22 inhibition of axon regeneration is abolished by genetic deletion of NgR1. Thus, NgR1 is the predominant receptor for Nogo-22 in regenerating cortical neurons.

Combination of multifaceted strategies to maximize the therapeutic benefits of neural stem cell transplantation for spinal cord repair.

Neural stem cells (NSCs) possess therapeutic potentials to reverse complex pathological processes following spinal cord injury (SCI), but many obstacles remain that could not be fully overcome by NSC transplantation alone. Combining complementary strategies might be required to advance NSC-based treatments to the clinical stage. The present study was undertaken to examine whether combination of NSCs, polymer scaffolds, neurotrophin-3 (NT3), and chondroitinase, which cleaves chondroitin sulfate proteoglycans at the interface between spinal cord and implanted scaffold, could provide additive therapeutic benefits. In a rat hemisection model, poly(ɛ-caprolactone) (PCL) was used as a bridging scaffold and as a vehicle for NSC delivery. The PCL scaffolds seeded with F3 NSCs or NT3 overexpressing F3 cells (F3.NT3) were implanted into hemisected cavities. F3.NT3 showed better survival and migration, and more frequently differentiated into neurons and oligodendrocytes than F3 cells. Animals with PCL scaffold containing F3.NT3 cells showed the best locomotor recovery, and motor evoked potentials (MEPs) following transcranial magnetic stimulation were recorded only in PCL-F3.NT3 group in contralateral, but not ipsilateral, hindlimbs. Implantation of PCL scaffold with F3.NT3 cells increased NT3 levels, promoted neuroplasticity, and enhanced remyelination of contralateral white matter. Combining chondroitinase treatment after PCL-F3.NT3 implantation further enhanced cell migration and promoted axonal remodeling, and this was accompanied by augmented locomotor recovery and restoration of MEPs in ipsilateral hindlimbs. We demonstrate that combining multifaceted strategies can maximize the therapeutic benefits of NSC transplantation for SCI. Our results may have important clinical implications for the design of future NSC-based strategies.

Endogenous expression of interleukin-4 regulates macrophage activation and confines cavity formation after traumatic spinal cord injury.

Traumatic spinal cord injury (SCI) triggers inflammatory reactions in which various types of cells and cytokines are involved. Several proinflammatory cytokines are up-regulated after SCI and play crucial roles in determining the extent of secondary tissue damage. However, relatively little is known about antiinflammatory cytokines and their roles in spinal cord trauma. Recent studies have shown that an antiinflammatory cytokine, interleukin-4 (IL-4), is expressed and exerts various modulatory effects in CNS inflammation. We found in the present study that IL-4 was highly expressed at 24 hr after contusive SCI in rats and declined thereafter, with concurrent up-regulation of IL-4 receptor subunit IL-4alpha. The majority of IL-4-producing cells were myeloperoxidase-positive neutrophils. Injection of neutralizing antibody against IL-4 into the contused spinal cord did not significantly affect the expression levels of proinflammatory cytokines such as IL-1beta, IL-6, and tumor necrosis factor-alpha or other antiinflammatory cytokines such as IL-10 and transforming growth factor-beta. Instead, attenuation of IL-4 activity led to a marked increase in the extent of ED1-positive macrophage activation along the rostrocaudal extent at 7 days after injury. The enhanced macrophage activation was preceded by an increase in the level of monocyte chemoattractant protein-1 (MCP-1/CCL2). Finally, IL-4 neutralization resulted in more extensive cavitation at 4 weeks after injury. These results suggest that endogenous expression of antiinflammatory cytokine IL-4 regulates the extent of acute macrophage activation and confines the ensuing secondary cavity formation after spinal cord trauma.

Transplantation of human neural stem cells transduced with Olig2 transcription factor improves locomotor recovery and enhances myelination in the white matter of rat spinal cord following contusive injury.

BACKGROUND: Contusive spinal cord injury is complicated by a delayed loss of oligodendrocytes, resulting in chronic progressive demyelination. Therefore, transplantation strategies to provide oligodendrocyte lineage cells and to enhance the extent of myelination appear to be justified for spinal cord repair. The present study investigated whether transplantation of human neural stem cells (NSCs) genetically modified to express Olig2 transcription factor, an essential regulator of oligodendrocyte development, can improve locomotor recovery and enhance myelination in a rat contusive spinal cord injury model. RESULTS: HB1.F3 (F3) immortalized human NSC line was transduced with a retroviral vector encoding Olig2, an essential regulator of oligodendrocyte development. Overexpression of Olig2 in human NSCs (F3.Olig2) induced activation of NKX2.2 and directed differentiation of NSCs into oligodendrocyte lineage cells in vitro. Introduction of Olig2 conferred higher proliferative activity, and a much larger number of F3.Olig2 NSCs were detected by 7 weeks after transplantation into contused spinal cord than that of parental F3 NSCs. F3.Olig2 NSCs exhibited frequent migration towards the white matter, whereas F3 NSCs were mostly confined to the gray matter or around the lesion cavities. Most of F3.Olig2 NSCs occupying the spared white matter differentiated into mature oligodendrocytes. Transplantation of F3.Olig2 NSCs increased the volume of spared white matter and reduced the cavity volume. Moreover, F3.Olig2 grafts significantly increased the thickness of myelin sheath around the axons in the spared white matter. Finally, animals with F3.Olig2 grafts showed an improvement in the quality of hindlimbs locomotion. CONCLUSION: Transplantation of NSCs genetically modified to differentiate into an oligodendrocytic lineage may be an effective strategy to improve functional outcomes following spinal cord trauma. The present study suggests that molecular factors governing cell fate decisions can be manipulated to enhance reparative potential of the cell-based therapy.

Overexpression of Bcl-XL in human neural stem cells promotes graft survival and functional recovery following transplantation in spinal cord injury.

Transplantation of neural stem cells (NSCs) has shown promise for improving functional recovery after spinal cord injury (SCI). The inhospitable milieu of injured spinal cord, however, does not support survival of grafted NSCs, reducing therapeutic efficacy of transplantation. The present study sought to examine whether overexpression of antiapoptotic gene Bcl-X(L) in NSCs could promote graft survival and functional recovery following transplantation in rat contusive SCI model. A human NSC line (HB1.F3) was transduced with a retroviral vector encoding Bcl-X(L) to generate Bcl-X(L)-overexpressing NSCs (HB1.F3.Bcl-X(L)). Overexpression of Bcl-X(L) conferred resistance to staurosporine-mediated apoptosis. The number of HB1.F3.Bcl-X(L) cells was 1.5-fold higher at 2 weeks and 10-fold higher at 7 weeks posttransplantation than that of HB1.F3 cells. There was no decline in the number of HB1.F3.Bcl-X(L) cells between 2 and 7 weeks, indicating that Bcl-X(L) overexpression completely blocked cell death occurring between these two time points. Transplantation of HB1.F3.Bcl-X(L) cells improved locomotor scores and enhanced accuracy of hindlimb placement in a grid walk. Approximately 10% of surviving NSCs differentiated into oligodendrocytes. Surviving NSCs produced brain-derived neurotrophic factor (BDNF), and the level of BDNF was significantly increased only in the HB1.F3.Bcl-X(L) group. Transplantation of HB1.F3.Bcl-X(L) cells reduced cavity volumes and enhanced white matter sparing. Finally, HB1.F3.Bcl-X(L) grafts enhanced connectivity between the red nucleus and the spinal cord below the lesion. These results suggest that enhancing graft survival with antiapoptotic gene can potentiate therapeutic benefits of NSC-based therapy for SCI.

Axonal outgrowth and Erk1/2 activation by training after spinal cord injury in rats.

Abstract Physical training in experimental animals can improve locomotor activity via the regulation of spinal neural circuitry or peripheral nerve regeneration. Here we investigated the effects of treadmill training (TMT) on regenerative responses of the corticospinal tract (CST) after contusive spinal cord injury (SCI). One week after injury of the low thoracic spinal cord, rats were given TMT or sedentary treatment for 1-4 weeks. Anterograde tracing of descending CST axons revealed that TMT enhanced collateral arborization of CST axons surrounding the injury cavity and promoted extension into the caudal spinal cord. The number of oligodendrocytes in the vicinity of the injury cavity was significantly increased at 2 or 4 weeks after TMT compared to sedentary controls. The data further showed that TMT increased phosphorylation of Erk1/2 in the motor cortex as well as the spinal cord injury area, and inhibition of Erk1/2 activity by administration of the MEK1 inhibitors PD98059 and U0126 reduced collateral outgrowth of descending CST axons in TMT animals. TMT for 2-4 weeks significantly improved behavioral scores as assessed by the Basso-Beattie-Bresnahan scale, as well as on motor function and gridwalk testing. Our data imply that Erk1/2 may be an important mediator for transmitting signals from the injury site to the cell body, and further suggest that activation of the Erk1/2 signaling pathway may be involved in enhanced outgrowth of CST axons after TMT.

Ex vivo VEGF delivery by neural stem cells enhances proliferation of glial progenitors, angiogenesis, and tissue sparing after spinal cord injury.

The present study was undertaken to examine multifaceted therapeutic effects of vascular endothelial growth factor (VEGF) in a rat spinal cord injury (SCI) model, focusing on its capability to stimulate proliferation of endogenous glial progenitor cells. Neural stem cells (NSCs) can be genetically modified to efficiently transfer therapeutic genes to diseased CNS. We adopted an ex vivo approach using immortalized human NSC line (F3 cells) to achieve stable and robust expression of VEGF in the injured spinal cord. Transplantation of NSCs retrovirally transduced to overexpress VEGF (F3.VEGF cells) at 7 days after contusive SCI markedly elevated the amount of VEGF in the injured spinal cord tissue compared to injection of PBS or F3 cells without VEGF. Concomitantly, phosphorylation of VEGF receptor flk-1 increased in F3.VEGF group. Stereological counting of BrdU+ cells revealed that transplantation of F3.VEGF significantly enhanced cellular proliferation at 2 weeks after SCI. The number of proliferating NG2+ glial progenitor cells (NG2+/BrdU+) was also increased by F3.VEGF. Furthermore, transplantation of F3.VEGF increased the number of early proliferating cells that differentiated into mature oligodendrocytes, but not astrocytes, at 6 weeks after SCI. F3.VEGF treatment also increased the density of blood vessels in the injured spinal cord and enhanced tissue sparing. These anatomical results were accompanied by improved BBB locomotor scores. The multifaceted effects of VEGF on endogenous gliogenesis, angiogenesis, and tissue sparing could be utilized to improve functional outcomes following SCI.

Modulation of dendritic spine remodeling in the motor cortex following spinal cord injury: effects of environmental enrichment and combinatorial treatment with transplants and neurotrophin-3.

Incomplete spinal cord injury (SCI) elicits structural plasticity of the spared motor system, including the motor cortex, which may underlie some of the spontaneous recovery of motor function seen after injury. Promoting structural plasticity may become an important component of future strategies to improve functional outcomes. We have recently observed dynamic changes in the density and morphology of dendritic spines in the motor cortex following SCI. The present study sought to test whether SCI-induced changes in spine density and morphology could be modulated by potential strategies to enhance functional recovery. We examined the effects of enriched environment, transplants, and neurotrophin-3 on the plasticity of synaptic structures in the motor cortex following SCI. Housing rats in an enriched environment increased spine density in the motor cortex regardless of injury. SCI led to a more slender and elongated spine morphology. Enriched housing mitigated the SCI-induced morphological alterations, suggesting that the environmental modification facilitates maturation of synaptic structures. Transplantation of embryonic spinal cord tissue and delivery of neurotrophin-3 at the injury site further increased spine density when combined with enriched housing. This combinatorial treatment completely abolished the injury-induced changes, restoring a preinjury pattern of spine morphology. These results demonstrated that remodeling of dendritic spines in the motor cortex after SCI can be modulated by enriched housing, and the combinatorial treatment with embryonic transplants and neurotrophin-3 can potentiate the effects of enriched housing. We suggest that synaptic remodeling processes in the motor cortex can be targeted for an intervention to enhance functional recovery after SCI.

Delayed transplantation with exogenous neurotrophin administration enhances plasticity of corticofugal projections after spinal cord injury.

Functional deficits following spinal cord injury (SCI) result from a disruption of corticofugal projections at the lesion site. Not only direct regeneration of the severed axons but also anatomical re-organization of spared corticofugal pathways can reestablish connections between the supraspinal and spinal motor centers. We have previously shown that delayed transplantation of fetal spinal cord tissue and neurotrophin administration by two weeks after SCI supported recovery of forelimb function in adult rats. The current study determined whether the same intervention enhances plasticity of corticofugal fibers at the midbrain and spinal cord level. Anterograde tracing of the left corticorubral fibers revealed that the animals with transplants and neurotrophins (BDNF or NT-3) increased the extent of the traced fibers crossing to the right red nucleus (RN), of which the axons are spared by a right cervical overhemisection lesion. More neurons in the left motor cortex were recruited by the treatment to establish connections with the right RN. The right corticorubral projections also increased the density of midline crossing fibers to the axotomized left RN in response to transplants and neurotrophins. Transplants plus NT-3, but not BDNF, significantly increased the amount of spared corticospinal fibers in the left dorsolateral funiculus at the spinal level both rostral and caudal to the lesion. These results suggest that corticofugal projections retain the capacity until at least two weeks after injury to undergo extensive reorganization along the entire neuraxis in response to transplants and neurotrophins. Targeting anatomical plasticity of corticofugal projections may be a promising strategy to enhance functional recovery following incomplete SCI.

Labeling of dendritic spines with the carbocyanine dye DiI for confocal microscopic imaging in lightly fixed cortical slices.

Visualization of dendritic spines is an important tool for researches on structural synaptic plasticity. Fluorescent labeling of the dendrites and spines followed by confocal microscopy permits imaging a large population of dendritic spines with a higher resolution. We sought to establish an optimal protocol to label neurons in cortical slices with the carbocyanine dye DiI for confocal microscopic imaging of dendritic spines. DiI finely labeled dendrites and spines in slices prefixed (by cardiac perfusion) with 1.5% paraformaldehyde to the similar extent that could be achieved in live preparation. In contrast, fixation with 4% paraformaldehyde severely compromised dye diffusion. Confocal microscopy showed that structural integrity of dendrites and spines was preserved much better in lightly (1.5%) fixed slices than those prepared without fixation. Quantitative measurement revealed that spine density was lower in live slices than that counted in lightly fixed slices, suggesting that fixation is necessary for an adequate evaluation of spine density. The quality of confocal microscopic images obtained from lightly fixed slices allowed us to observe distinctive morphologies such as branched spines and dendritic filopodium, which may be indicative of structural changes at synapses. This method will thus be useful for studying structural synaptic plasticity.

Degradation of chondroitin sulfate proteoglycans potentiates transplant-mediated axonal remodeling and functional recovery after spinal cord injury in adult rats.

Transplantation of growth-permissive cells or tissues was used to bridge a lesion cavity and induce axonal growth in experimental spinal cord injury (SCI). Axonal interactions between host and transplant may be affected by upregulation of inhibitory chondroitin sulfate proteoglycans (CSPGs) following various transplantation strategies. The extent of axonal growth and functional recovery after transplantation of embryonic spinal cord tissue decreases in adult compared to neonatal host. We hypothesized that CSPGs contribute to the decrease in the extent to which transplant supports axonal remodeling and functional recovery. Expression of CSPGs increased after overhemisection SCI in adult rats but not in neonates. Embryonic spinal cord transplant was surrounded by CSPGs deposited in host cord, and the interface between host and transplant seemed to contain a large amount of CSPGs. Intrathecally delivered chondroitinase ABC (C'ase) improved recovery of distal forelimb usage and skilled motor behavior after C4 overhemisection injury and transplantation in adults. This behavioral recovery was accompanied by an increased amount of raphespinal axons growing into the transplant, and raphespinal innervation to the cervical motor region was promoted by C'ase plus transplant. Moreover, C'ase increased the number of transplanted neurons that grew axons to the host cervical enlargement, suggesting that degradation of CSPGs supports remodeling not only of host axons but also axons from transplanted neurons. Our results suggest that CSPGs constitute an inhibitory barrier to prevent axonal interactions between host and transplant in adults, and degradation of the inhibitory barrier can potentiate transplant-mediated axonal remodeling and functional recovery after SCI.