Poly-lactic acid and agarose gelatin play an active role in the recovery of spinal cord injury

Objective To investigate the role of poly-lactic acid and agarose gelatin in promoting the functional recovery of the injured spinal cord. Methods Poly-lactic acid （PLA） or agarose was embedded in the space between two stumps of the hemisectioned spinal cord. Immunohistochemistry was used to show astroglia proliferation and the infiltration of RhoA-positive cells. Locomotor activity recovery was evaluated by testing the function of hindlimbs. Results Astroglias and RhoA labeled non-neuronal cells accumulated in the area adjacent to the implant, while the number of RhoA-posirive cells was decreased dramatically in the absence of implant. Animals implanted with agarose gelatin recovered more quickly than those with PLA, concomitant with a higher survival rate of the neurons. Conclusion Both PLA and agarose gelatin benefited the recovery of spinal cord after injury by providing a scaffold for astroglia processes. Modulation of the rigidity, pore size and inner structure of PLA and agarose gelatin might make these biodegradable materials more effective in the regeneration of the central nervous system （CNS）.     

Autologous sciatic nerve grafts to the rat spinal cord: Immunofluorescence studies with neurofilament and gliofilament (GFA) antisera

Autologous sciatic nerve grafts to the spinal cord contained many regenerating nerve fibers intensely immunofluorescent with neurofilament antisera. Axonal growth was not confined to the graft but also occurred in the surrounding spinal cord. In this location regenerating nerve fibers were invariably associated with Schwann-like cells. The reverse situation, that is, invasion of the graft by GFA-positive astroglia, also occurred but was a more limited phenomenon involving only a few cells.     

Focal phospholipases A2 group III injections induce cervical white matter injury and functional deficits with delayed recovery concomitant with Schwann cell remyelination

Phospholipases A(2) (PLA(2)) are group of enzymes that hydrolyze membrane phospholipids at the sn-2 position. PLA(2) are present in the brain and spinal cord and are implicated in several neurological disorders. Previously, we showed that PLA(2) activity increases following traumatic spinal cord injury and injection of group III secretory PLA(2) (sPLA(2)-III) demyelinates spinal cord axons. Here, we demonstrate that injections of sPLA(2)-III into the cervical dorsolateral funiculus (DLF) resulted in dose-dependent demyelination, loss of oligodendrocytes and astrocytes, as well as axonopathy. Additionally, spared axons within the lesion were remyelinated by Schwann cells between weeks 2 and 3. To assess functional loss and recovery, we employed a modified "Staircase Test" pellet retrieval device and footprint analysis of forelimb function during locomotion. Pellet retrieval assessment sensitively detected the dose dependent lesion and its recovery after sPLA(2)-III injections with greater sensitivity than footprint analysis. We believe that this is the first report of a reaching task being able to discriminate between various grades of cervical white matter damage and varying extents of recovery. Thus, our results indicate that sPLA(2)-III can create white matter pathologies that are remyelinated by Schwann cells 2 to 3 weeks after injury. Additionally, the pellet retrieval test is a sensitive and quantifiable method for assessing the dysfunction and later recovery mediated by sPLA(2)-III injections.     

Aldynoglia cells and modulation of RhoGTPase activity as useful tools for spinal cord injury repair

A combined approach in spinal cord injury (SCI) therapy is the modulation of the cellular and molecular processes involved in glial scarring. Aldaynoglial cells are neural cell precursors with a high capacity to differentiate into neurons, promote axonal growth, wrapping and myelination of resident neurons. These important characteristics of aldaynoglia can be combined with speciifc inhibition of the RhoGTPase ac-tivity in astroglia and microglia that cause reduction of glial proliferation, retraction of glial cell processes and myelin production by oligodendrocytes. Previously we used experimental central nervous system (CNS) injury models, like spinal cord contusion and striatal lacunar infarction and observed that adminis-tration of RhoGTPase glycolipid inhibitor or aldaynoglial cells, respectively, produced a signiifcant gain of functional recovery in treated animals. The combined therapy with neuro-regenerative properties strategy is highly desirable to treat SCI for functional potentiation of neurons and oligodendrocytes, resulting in better locomotor recovery. Here we suggest that treatment of spinal lesions with aldaynoglia from neu-rospheres plus local administration of a RhoGTPase inhibitor could have an additive effect and promote recovery from SCI.     

Collagen containing neonatal astrocytes stimulates regrowth of injured fibers and promotes modest locomotor recovery after spinal cord injury

The use of collagen as a vehicle to transplant neonatal astroglial cells into the lesioned spinal cord of the adult rat allows a precise application of these cells into the lesion gap and minimizes the migration of the transplanted cells. This approach might lead to anatomical and functional recovery. In the present study, 20 adult female Wistar rats were subjected to a dorsal hemisection at thoracic spinal cord levels. Cultured cortical neonatal rat astrocytes were transplanted into the lesion with collagen as a vehicle (N = 10). Prior to transplantation, the cultured astroglial cells were labelled with fast blue. Control rats received collagen implants only (N = 10). During 1 month of survival time, functional recovery of all rats was continuously monitored. Histological data showed that the prelabelled astroglial cells survived transplantation and were localized predominantly in the collagen implant. Virtually no fast blue-labelled GFAP-positive astroglial cells migrated out of the implant into the adjacent host spinal cord. The presence of transplanted neonatal astroglial cells resulted in a significant increase in the number of ingrowing neurofilament-positive fibers (including anterogradely labeled corticospinal axons) into the implant. Ingrowing fibers were closely associated with the transplanted astroglial cells. The implantation of neonatal astroglial cells did result in modest temporary improvements of locomotor recovery as observed during open-field locomotion analysis (BBB subscore) or during crossing of a walkway (catwalk).     

Astroglial reaction in the gray matter lumbar segments after midthoracic transection of the adult rat spinal cord

Previous studies of cordotomized rats revealed a glial reaction in the gray matter of the spinal cord at sites remote from the lesion, and the present study was done to explore this phenomenon further. Seventy-five young adult female rats were cordotomized and 10 hemicordotomized, both operations at T5. Between 1 and 28 days postoperatively, histologic sections of thoracic and lumbar segments stained by phosphotungstic acid hematoxylin (PTAH, pH 2.37), by periodic acid Schiffdimedon (PAS-D) or by an immunocytochemical method for glial fibrillar acidic protein (GFAP) revealed histological changes as follows: PTAH staining showed that astroglia in thoracic and lumbar regions of the cordotomized rats possessed a swollen, pink-staining cytoplasm and enlarged, thick, dark blue-staining fibrous processes. This response, first noted within 4 days, had intensified by 7 days and was maximal at 14 to 17 days postoperatively. By 28 days, the reaction had diminished but was still readily detectable. The more specific GFAP staining procedure confirmed that the reactive cells were astrocytes and demonstrated that their fibrillar density had increased. The PAS-D reaction revealed glycogen accumulation in glia of the lumbar gray matter within 2 days; this response intensified by 4 days and diminished to normal by 14 days. This reaction was largely concentrated in the perivascular end feet of astroglia, but also appeared in conjunction with perineuronal astroglia. The site of glial reactivity included both dorsal and ventral horns and was particularly noticed in the gray matter surrounding the central canal. In the hemicordotomized rats, the thoracic and lumbar glia response was much more pronounced ipsilaterally than contralaterally. These results support the interpretation that an astroglial response, involving hypertrophy, fibrillogenesis, and glycogen accumulation, occurs in response to degenerating nerve fibers caudal to sites of spinal cord injury.     

Engineering angiogenesis following spinal cord injury: a coculture of neural progenitor and endothelial cells in a degradable polymer implant leads to an increase in vessel density and formation of the blood–spinal cord barrier

Angiogenesis precedes recovery following spinal cord injury and its extent correlates with neural regeneration, suggesting that angiogenesis may play a role in repair. An important precondition for studying the role of angiogenesis is the ability to induce it in a controlled manner. Previously, we showed that a coculture of endothelial cells (ECs) and neural progenitor cells (NPCs) promoted the formation of stable tubes in vitro and stable, functional vascular networks in vivo in a subcutaneous model. We sought to test whether a similar coculture would lead to the formation of stable functional vessels in the spinal cord following injury. We created microvascular networks in a biodegradable two-component implant system and tested the ability of the coculture or controls (lesion control, implant alone, implant + ECs or implant + NPCs) to promote angiogenesis in a rat hemisection model of spinal cord injury. The coculture implant led to a fourfold increase in functional vessels compared with the lesion control, implant alone or implant + NPCs groups and a twofold increase in functional vessels over the implant + ECs group. Furthermore, half of the vessels in the coculture implant exhibited positive staining for the endothelial barrier antigen, a marker for the formation of the blood–spinal cord barrier. No other groups have shown positive staining for the blood–spinal cord barrier in the injury epicenter. This work provides a novel method to induce angiogenesis following spinal cord injury and a foundation for studying its role in repair.     

Enhanced regeneration in spinal cord injury by concomitant treatment with granulocyte colony-stimulating factor and neuronal stem cells.

Granulocyte colony-stimulating factor (G-CSF) inhibits programmed cell death and stimulates neuronal progenitor differentiation. Neuronal stem cells transplanted into injured spinal cord can survive, differentiating into astroglia and oligodendroglia, and supporting axon growth and myelination. Herein, we evaluate the combined effects of G-CSF and neuronal stem cells on spinal cord injury. For 40 Sprague-Dawley rats (n=10 in each group) transverse spinal cord resections at the T8-9 level were carried out, leaving an approximately 2-mm gap between the distal and proximal ends of the cord. Neuronal stem cells embedded in fibrin glue treated with or without G-CSF (50 microg/kg x 5 days) (groups III and IV) or fibrin glue with or without G-CSF (50 microg/kg x 5 days) (groups I and II) were transplanted into the gap in the injured spinal cord. Spinal cord regeneration was assessed using a clinical locomotor rating scale scores and electrophysiological, histological and immunohistochemical analysis 3 months after injury. Regeneration was more advanced in group IV than in groups III or II according to the clinical motor score, motor evoked potential, and conduction latency. Most advanced cord regeneration across the gap was observed in group IV rats. Higher densities of bromodeoxyuridine in the injured area and higher expression levels of Neu-N and MAP-2 over the distal end of the injured spinal cord were observed in group IV compared with groups II or III, but there was no significant difference in expression of glial fibrillary acid protein. This synergy between G-CSF and neuronal stem cells may be due to increased proliferation of progenitor cells in the injured area and increased expression of neuronal stem cell markers extrinsically or intrinsically in the distal end of injured cord.     

Vasoactive intestinal polypeptide neurons in fetal cortical homografts to adult rat spinal cord

Transplants of central nervous system to adult spinal cords are considered as potential aids in regeneration of the spinal cord and/or recovery of function after injury. The organization and development of the implant are important issues in seeking the potential for a transplant and host to become functionally integrated. This study uses embryonic cerebral cortex transplanted into the spinal cord of adult rats (T6) and examined the development and organization of the transplant with an antibody to vasoactive intestinal polypeptide (VIP). The cell bodies of VIP neurons are in the implants at 30 days postimplantation, but few of the somata have processes. By 45 days postimplantation, VIP neurons in the implant have dendrites and axons and are clearly recognizable as cortical bipolar cells which are not normally present in the thoracic spinal cord. These data show that neurons in embryonic cerebral cortical implants into the spinal cord elaborate the appropriate biochemical and morphological constituents in spite of the ectopic location. However, the cell processes develop at a slower than normal pace. Morphological interaction between the host spinal cord and the implant can be demonstrated possibly as early as 45 days postimplantation and clearly at 6 months following the implant. Thus, further examination of cerebral cortical implants as a potential aid in allevation of paraplegia subsequent to spinal cord injury is warranted.     

Embryonic radial glia bridge spinal cord lesions and promote functional recovery following spinal cord injury

Radial glial cells are neural stem cells (NSC) that are transiently found in the developing CNS. To study radial glia, we isolated clones following immortalization of E13.5 GFP rat neurospheres with v-myc. Clone RG3.6 exhibits polarized morphology and expresses the radial glial markers nestin and brain lipid binding protein. Both NSC and RG3.6 cells migrated extensively in the adult spinal cord. However, RG3.6 cells differentiated into astroglia slower than NSC, suggesting that immortalization can delay differentiation of radial glia. Following spinal cord contusion, implanted RG3.6 cells migrated widely in the contusion site and into spared white matter where they exhibited a highly polarized morphology. When injected immediately after injury, RG3.6 cells formed cellular bridges surrounding spinal cord lesion sites and extending into spared white matter regions in contrast to GFP fibroblasts that remained in the lesion site. Behavioral analysis indicated higher BBB scores in rats injected with RG3.6 cells than rats injected with fibroblasts or medium as early as 1 week after injury. Spinal cords transplanted with RG3.6 cells or dermal fibroblasts exhibited little accumulation of chondroitin sulfate proteoglycans (CSPG) including NG2 proteoglycans that are known to inhibit axonal growth. Reduced levels of CSPG were accompanied by little accumulation in the injury site of activated macrophages, which are a major source of CSPG. However, increased staining and organization of neurofilaments were found in injured rats transplanted with RG3.6 cells suggesting neuroprotection or regrowth. The combined results indicate that acutely transplanted radial glia can migrate to form bridges across spinal cord lesions in vivo and promote functional recovery following spinal cord injury by protecting against macrophages and secondary damage.     

Astroglia-mediated effects of uric acid to protect spinal cord neurons from glutamate toxicity

Uric acid (UA) has been demonstrated to reduce damage to neurons elicited by oxidative stress. However, our studies utilizing cultures derived from embryonic rat spinal cord indicate that an astroglia-mediated mechanism is involved in the effects of UA to protect neurons from glutamate toxicity. The damage elicted by glutamate to neurons in a mixed culture of spinal cord cells can be reversed by UA. Furthermore, addition of UA after the termination of glutamate exposure suggests that UA plays an active role in mediating neuroprotection rather than purely binding peroxynitrite, as previously thought. Importantly, in pure neuron cultures from the same tissue, UA does not protect against glutamate toxicity. Addition of astroglia to the pure neuron cultures restores the ability of UA to protect the neurons from glutamate-induced toxicity. Our results also suggest that glia provide EAAT-1 and EAAT-2 glutamate transporters to protect neurons from glutamate, that functional EAATs may be necessary to mediate the effects of UA, and that treatment with UA results in upregulation of EAAT-1 protein. Taken together, our data strongly suggest that astroglia in mixed cultures are essential for mediating the effects of UA, revealing a novel mechanism by which UA, a naturally produced substance in the body, may act to protect neurons from damage during insults such as spinal cord injury.     

组织工程脊髓移植治疗大鼠脊髓半切块状损伤

目的 研究组织工程脊髓移植治疗大鼠脊髓半切块状损伤的疗效.方法 以聚乳酸-羟基乙酸(PLGA)为细胞支架,多聚赖氨酸为细胞外基质,神经十细胞(NSCs)为种子细胞,体外构建组织工程脊髓.制作大鼠T10脊髓右半切块状损伤模型,随机分成3组:实验组在损伤区移植组织工程脊髓,对照组A移植NSCs,对照组B移植PLGA.移植治疗12周,每周均行BBB评分定量评价肢体运动功能.伤后第12周辣根过氧化物酶(HRP)神经逆行示踪评价脊髓传导束的恢复程度,并取损伤处脊髓组织行免疫组织化学染色,观察移植区的形态结构修复.结果 伤后12周实验组的BBB运动功能评分较对照组明显提高,差异有统计学意义(P＜0.05).HRP神经逆行示踪显示:实验组鼠右侧大脑组织中可见大量的HRP标记阳性神经元,而两对照组仅见有少量HRP阳性神经元;免疫组织化学染色显示:实验组移植区NF阳性神经元和GAP-43阳性神经轴索数量较多,修复了缺损,而对照组极少,仍留下不同程度的缺损.结论 组织工程脊髓移植治疗促进了半切块状损伤脊髓的形态结构修复和功能恢复,疗效明显优于单纯的NSCs移植和PLGA移植.     

新型三维编织型生物支架的研制及体外生物相容性*☆

背景：脊髓损伤后,由于有胶质瘢痕的阻隔,使再生的轴突难以穿越损伤区域,从而影响脊髓功能的恢复。随着组织工程技术的发展,研究人员尝试利用在三维支架的空间诱导作用下,让再生的轴突和支架内部携带的细胞能够三维有序的生长,穿越瘢痕屏障,连接脊髓损伤断端。 目的：采用编织工艺研制新型以聚乙交酯-丙交酯为原料的三维支架,检测新型支架与许旺细胞的生物相容性。 设计、时间及地点：体外对比观察实验,于2007-06/2008-03在长海医院中心实验室完成。 材料：选择聚乳酸︰聚羟基乙酸为9︰1的聚合材料聚乙交酯-丙交酯,通过熔融纺丝、拉伸、编织等步骤制作聚乙交酯-丙交酯三维支架。取新生3 d SD乳鼠的坐骨神经,分离、纯化许旺细胞。 方法：实验分3组：三维支架组将许旺细胞接种在新型三维支架内培养;明胶海绵组将许旺细胞接种在胶原海绵上培养;细胞培养皿组直接接种在预涂左旋多聚赖氨酸的24孔培养板上培养。 主要观察指标：扫描电镜观察内部微管道的排列规律,测量其孔径大小、孔隙率等指标。通过倒置相差显微镜和扫描电镜观察许旺细胞在支架上生长情况,包括许旺细胞在支架上的黏附、增殖和凋亡情况等。 结果：支架外径为3 mm,微管道内径为100 μm,呈均匀平行排列,支架的孔隙率为68%。三维支架组与细胞培养皿组中的许旺细胞黏附、增殖差异无显著性意义,与明胶海绵组差异有显著性意义。三维支架组与明胶海绵组中细胞凋亡差异无显著性意义,它们均低于细胞培养皿组,差异有显著性意义。 结论：新型三维编织型支架具有良好的生物相容性。 关键词：支架;许旺细胞;组织工程;生物相容性     

丙戊酸对脊髓损伤大鼠内源性神经干细胞增殖的影响

BACKGROUND： Valproic acid has been reported to decrease apoptosis, promote neuronal differentiation of brain-derived neural stem cells, and inhibit glial differentiation of brain-derived neural stem cells.
OBJECTIVE： To investigate the effects of valproic acid on proliferation of endogenous neural stem cells in a rat model of spinal cord injury.
DESIGN, TIME AND SETTING： A randomized, controlled, neuropathological study was performed at Key Laboratory of Trauma, Buming, and Combined Injury, Research Institute of Surgery, Daping Hospital, the Third Military Medical University of Chinese PLA between November 2005 and February 2007.
MATERIALS： A total of 45 adult, Wistar rats were randomly divided into sham surgery （n = 5）, injury （n = 20）, and valproic acid （n = 20） groups. Valproic acid was provided by Sigma, USA. METHODS： Injury was induced to the T10 segment in the injury and valproic acid groups using the metal weight-dropping method. The spinal cord was exposed without contusion in the sham surgery group. Rats in the valproic acid group were intraperitoneally injected with 150 mg/kg valproic acid every 12 hours （twice in total）.
MAIN OUTCOME MEASURES： Nestin expression （5 mm from injured center） was detected using immunohistochemistry at 1,3 days, 1, 4, and 8 weeks post-injury.
RESULTS： Low expression of nestin was observed in the cytoplasm, but rarely in the white matter of the spinal cord in the sham surgery group. In the injury group, nestin expression was observed in the ependyma and pia mater one day after injury, and expression reached a peak at 1 week （P 〈 0.05）. Expression was primarily observed in the ependymal cells, which expanded towards the white and gray matter of the spinal cord. Nestin expression rapidly decreased by 4 weeks post-injury, and had almost completely disappeared by 8 weeks. At 24 hours after spinal cord injury, there was no significant difference in nestin expression between the valproic acid and injury groups. At 1 week, there was a significant increase in the number of nestin-positive cells surrounding the central canal in valproic acid group compared with the injury group （P 〈 0.05）. Expression reached a peak by 4 weeks, and it was still present at 8 weeks.
CONCLUSION： Valproic acid promoted endogenous neural stem cell proliferation following spinal cord injury in rats.     

Effect of valproic acid on endogenous neural stem cell proliferation in a rat model of spinal cord injury

BACKGROUND: Valproic acid has been reported to decrease apoptosis, promote neuronal differentiation of brain-derived neural stem cells, and inhibit glial differentiation of brain-derived neural stem cells.OBJECTIVE: To investigate the effects of valproic acid on proliferation of endogenous neural sterm cells in a rat model of spinal cord injury.DESIGN, TIME AND SETTING: A randomized, controlled, neuropathological study was performed at Key Laboratory of Trauma, Buming, and Combined Injury, Research Institute of Surgery, Daping Hospital, the Third Military Medical University of Chinese PLA between November 2005 and February 2007.MATERIALS: A total of 45 adult, Wistar rats were randomly divided into sham surgery (n=5), injury(n=20), and valproic acid (n=20) groups. Valproic acid was provided by Sigma, USA.METHODS: Injury was induced to the T10 segment in the injury and valproic acid groups using the metal weight-dropping method. The spinal cord was exposed without contusion in the sham surgery group. Rats in the valproic acid group were intraperitoneally injected with 150 mg/kg valproic acid every 12 hours (twice in total).MAIN OUTCOME MEASURES: Nestin expression (5 mm from injured center) was detected using immunohistochemistry at 1, 3 days, 1, 4, and 8 weeks post-injury.RESULTS: Low expression of nestin was observed in the cytoplasm, but rarely in the white matter of the spinal cord in the sham surgery group. In the injury group, nestin expression was observed in the ependyma and pia mater one day after injury, and expression reached a peak at 1 week (P<0.05).Expression was primarily observed in the ependymal cells, which expanded towards the white and gray matter of the spinal cord. Nestin expression rapidly decreased by 4 weeks post-injury, and had almost completely disappeared by 8 weeks. At 24 hours after spinal cord injury, there was nosignificant difference in nestin expression between the valproic acid and injury groups. At 1 week,there was a significant increase in the number of nestin-positive cells surrounding the central canal in valproic acid group compared with the injury group (P<0.05). Expression reached a peak by 4 weeks, and it was still present at 8 weeks.CONCLUSION: Valproic acid promoted endogenous neural stem cell proliferation following spinal cord injury in rats.     

Vasoactive intestinal peptide: a neurotrophic releasing agent and an astroglial mitogen

Vasoactive intestinal peptide (VIP) increases neuronal survival in dissociated spinal cord cultures during a critical period of development. In the present study, two mechanisms contributing to this action of VIP have been observed: 1) VIP was shown to be a secretagogue for neuron survival-promoting activity; and 2) VIP was found to be an astroglial mitogen. A high molecular weight substance (greater than 30 kDa), which increased neuronal survival in tetrodotoxin (TTX)-treated spinal cord cultures, was detected in the medium from nonneuronal cells incubated for 1 hr with 0.1 nM VIP. In addition, 3H-thymidine autoradiography and glial fibrillary acid protein (GFAP) immunocytochemistry were used to show that a 5 day treatment with (VIP) increased astroglial mitosis. This effect was specific for astroglia, as silver grain-positive cells not exhibiting GFAP immunoreactivity did not increase in number after VIP treatment. The dual action of VIP may regulate glial-derived trophic substances that are important for neuronal survival during the course of development.     

A novel role of phospholipase A2 in mediating spinal cord secondary injury

OBJECTIVE: To investigate whether phospholipase A2 (PLA2) plays a role in the pathogenesis of spinal cord injury (SCI). METHODS: Biochemical, Western blot, histological, immunohistochemical, electron microscopic, electrophysiological, and behavior assessments were performed to investigate (1) SCI-induced PLA2 activity, expression, and cellular localization after a contusive SCI; and (2) the effects of exogenous PLA2 on spinal cord neuronal death in vitro and tissue damage, inflammation, and function in vivo. RESULTS: After SCI, both PLA2 activity and cytosolic PLA2 expression increased significantly, with cytosolic PLA2 expression being localized mainly in neurons and oligodendrocytes. Both PLA2 and melittin, an activator of endogenous PLA2, induced spinal neuronal death in vitro, which was substantially reversed by mepacrine, a PLA2 inhibitor. When PLA2 or melittin was microinjected into the normal spinal cord, the former induced confined demyelination and latter diffuse tissue necrosis. Both injections induced inflammation, oxidation, and tissue damage, resulting in corresponding electrophysiological and behavioral impairments. Importantly, the PLA2-induced demyelination was significantly reversed by mepacrine. INTERPRETATION: PLA2, increased significantly after SCI, may play a key role in mediating neuronal death and oligodendrocyte demyelination following SCI. Blocking PLA2 action may represent a novel repair strategy to reduce tissue damage and increase function after SCI.     

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.     

Salvianolic acid B protects the myelin sheath around injured spinal cord axons

Salvianolic acid B,an active pharmaceutical compound present in Salvia miltiorrhiza,exerts a neuroprotective effect in animal models of brain and spinal cord injury.Salvianolic acid B can promote recovery of neurological function;however,its protective effect on the myelin sheath after spinal cord injury remains poorly understood.Thus,in this study,in vitro tests showed that salvianolic acid B contributed to oligodendrocyte precursor cell differentiation,and the most effective dose was 20 μg/m L.For in vivo investigation,rats with spinal cord injury were intraperitoneally injected with 20 mg/kg salvianolic acid B for 8 weeks.The amount of myelin sheath and the number of regenerating axons increased,neurological function recovered,and caspase-3 expression was decreased in the spinal cord of salvianolic acid B-treated animals compared with untreated control rats.These results indicate that salvianolic acid B can protect axons and the myelin sheath,and can promote the recovery of neurological function.Its mechanism of action is likely to be associated with inhibiting apoptosis and promoting the differentiation and maturation of oligodendrocyte precursor cells.     

Prevention of gliotic scar formation by NeuroGel allows partial endogenous repair of transected cat spinal cord

Spinal cords of adult cats were transected and subsequently reconnected with the biocompatible porous poly (N-[2-hydroxypropyl] methacrylamide) hydrogel, NeuroGel. Tissue repair was examined at various time points from 6-21 months post reconstructive surgery. We examined two typical phenomena, astrogliosis and scar formation, in spines reconstructed with the gel and compared them to those from transected non-reconstructed spines. Confocal examination with double immunostaining for glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) showed that the interface formed between the hydrogel and the spine stumps did prevent scar formation and only a moderate gliosis was observed. The gel implant provided an adequate environment for growth of myelinated fibers and we saw angiogenesis within the gel. Electron microscopy showed that regenerating axons were myelinated by Schwann cells rather than oligodendrocytes. Moreover, the presence of the gel implant lead to a considerable reduction in damage to distal caudal portions of the spine as assessed by the presence of more intact myelinated fibers and a reduction of myelin degradation. Neurologic assessments of hindlimb movement at various times confirmed that spinal cord reconstruction was not only structural but also functional. We conclude that NeuroGel lead to functional recovery by providing a favorable substrate for regeneration of transected spinal cord, reducing glial scar formation and allowing angiogenesis.