嗅鞘细胞移植治疗脊髓损伤的应用前景

介绍嗅鞘细胞在脊髓损伤中的研究进展.嗅鞘细胞是神经系统中具有促进神经轴突再生,引导轴突正确生长的独特细胞,为脊髓损伤的修复带来了希望,具有较好的临床应用前景.目前许多研究将基因工程技术和组织工程技术应用于其移植过程中,取得了一定的成果.     

嗅鞘细胞与中枢神经损伤修复

中枢神经损伤特别是脊髓损伤的修复，至今仍然是医学界的一个难题。其原因是中枢神经的再生能力低下及外在环境对轴突再生的抑制作用。国内外已进行了大量的实验来研究中枢神经损伤的修复问题。这些研究主要从以下方面入手：拮抗神经生长的抑制性环境；刺激轴突再生；细胞移植。用来移植的细胞类型有：胶质细胞包括雪旺细胞、少突神经胶质细胞或其前体细胞、嗅鞘细胞；     

嗅鞘细胞治疗脊髓损伤的研究进展

脊髓损伤是一种高致残性神经系统损伤性疾病,目前仍然缺乏有效的治疗方法。研究证实嗅鞘细胞是促进脊髓损伤后神经再生的理想种子细胞之一。嗅鞘细胞能通过分泌作用、与星形胶质细胞相互作用、调节炎症反应、迁移特性、髓鞘形成作用、抗氧化作用、脂质调节作用等方式或特性促进轴突的萌发及定向延长,从而发挥神经保护以及神经修复作用。近年来,一些研究利用生物工程、组织工程、重编程等技术从不同方面增强了嗅鞘细胞的疗效,从而为优化脊髓损伤的细胞治疗提供了新的治疗策略。本文将对嗅鞘细胞修复脊髓损伤的机制加以总结,同时归纳近些年优化嗅鞘细胞治疗脊髓损伤策略的研究进展,为进一步开发脊髓损伤后神经修复潜能提供新的研究思路,优化脊髓损伤的细胞治疗效果。     

嗅鞘胶质细胞的培养、鉴定及在脊髓损伤中的应用

近几年随着对神经系统研究的不断深入，人们发现成熟的嗅觉系统感觉神经细胞与其它中枢神经系统不同，能够不停地进行自我更新，其新形成的轴突长入嗅球后可形成完整的突触功能联系。原因是嗅觉系统含有特殊的胶质细胞———嗅鞘胶质细胞（olfactoryensheathingglia,OEG），兼有雪旺氏细胞和星形胶质细胞的特点［1~3］，既能存在于周围神经系统，又能存在于中枢神经系统。研究发现植入培养的OEG能显著改善脊髓轴突的生长，使轴突再生通过脊髓损伤部位而重新进入损伤远端。国外介绍嗅鞘胶质细胞培养和鉴定的文章很多［4、5］，但不是省略…     

嗅鞘细胞移植治疗脊髓损伤的进展

嗅鞘细胞（Olfactory ensheathing cells,OECs）是一种嗅神经的支持细胞,它起源于嗅基底膜,分布在嗅球,嗅神经和嗅中枢,作为一种具有中枢神经系统（CNS）星形胶质细胞,少突胶质细胞和周围神经系统（PNS）雪旺氏细胞特性的特殊细胞类型,它位于中枢和外周神经系统过渡区,其功能极为活跃,嗅鞘细胞移植能降解有关抑制轴突再生分子,分泌不同种类的神经营养因子和支持因子,促进神经轴突和髓鞘的再生,     

嗅鞘细胞移植治疗脊髓损伤进展

脊髓损伤的治疗一直是科学家和临床医生面临的颇具挑战性问题,近百年来没有多大进展!近年来,髓内细胞移植治疗脊髓横断损伤取得了一定疗效,为严重脊髓损伤的治疗提供了新的方法.其中,移植成髓鞘的细胞取得了较好的疗效,如:雪旺氏细胞,少突胶质细胞,嗅鞘细胞.所有的这些细胞中,嗅鞘细胞(olfactory ensheathing cells OECs)使轴突再生和髓鞘化的效果最好,被许多学者认为是最佳的移植细胞.有可能在脊髓损伤的治疗上取得突破!……     

嗅鞘细胞在脊髓损伤修复重建中的研究现状及最新进展

嗅鞘细胞移植是脊髓损伤修复的研究热点之一，被认为是最有前景的一个方法。研究者观察到嗅神经上皮在人体停止生长发育后，仍能终生有规律地生成新的神经元，而且发出的轴突被切断后仍能再生并穿越外周到达中枢部分的嗅球。这主要归功于嗅神经系统存在的特殊胶质细胞——嗅鞘细胞，能够引导和促进轴突生长。基于这一特性，嗅鞘细胞被大量应用于脊髓损伤后的修复研究中。[第一段]     

大鼠嗅球成鞘细胞的体外原代培养、纯化及鉴定

脊髓损伤所致的瘫痪往往导致显著性的机体功能障碍乃至功能丧失。而脊髓损伤后轴突再生困难是引起上述结果主要原因之一．其治疗亦是医学界公认的难题。19世纪末期西班牙组织学家Blanes Viale首先描述：嗅神经鞘细胞（简称嗅鞘细胞,olfactory ensheathing cells,OECs）具有施旺细胞和星形胶质细胞双重特性,研究者们开始关注之并对其进行了研究。随着实验研究的进展,科学家们发现OECs能促进损伤脊髓神经的再生,同时成功的从大鼠嗅球及嗅粘膜中成功分离培养出OECs,并用于移植治疗大鼠脊髓横断损伤模型。     

对应用嗅神经鞘细胞移植治疗脊髓损伤的看法

近年来国内外在实验性细胞移植治疗脊髓损伤上，对雪旺细胞（SCs）、胚胎干细胞、神经干细胞及嗅神经鞘细胞（OECs）的研究从细胞培养、分离、纯化到实验性脊髓损伤的移植修复都取得了一定的进展。动物实验显示，OECs能分泌多种神经营养因子和粘附分子，具有细胞粘附及促轴突再生的功能。OECs移植用于治疗成年动物脊髓损伤能维持神经元存活和轴突再生．促进下行传导通路纤维的再生和运动功能的恢复：OECs还能穿过星形胶质细胞形成的瘢痕环境．为受损轴突提供有利于其迁移、生长的支架．成为神经再生的桥梁。     

神经营养素-3基因修饰嗅鞘细胞移植对急性脊髓损伤作用的实验研究

目的：观察神经营养素-3（NT-3）基因转染嗅鞘细胞（OEG）移植对急性大鼠脊髓损伤的作用。方法：将自行构建的质粒DEGFP-NT3应用脂质体介导的方法导人体外培养的嗅鞘细胞，并移植入急性脊髓损伤大鼠体内．连续观察12周．与接受单纯OEG、空白质粒转染OEG移植的脊髓损伤大鼠进行比较。结果：移植转染DEGFP-NT3后的OEG能在体内长期存活，表达NT-3基因，与对照组比较能更好地促进脊髓损伤区轴突的再生和后肢功能的恢复。结论：OEG是脊髓损伤基因治疗较好的受体细胞。转染NT-3基因的OEG移植后可以在体内较长时间存活．能明显促进急性脊髓损伤神经纤维的再生和功能恢复，为基因修饰嗅鞘细胞在脊髓损伤治疗中的应用提供了实验和理论依据。     

Olfactory ensheathing cells: bridging the gap in spinal cord injury

Spinal cord injury (SCI) continues to be an insidious and challenging problem for scientists and clinicians. Recent neuroscientific advances have changed the pessimistic notion that axons are not capable of significant extension after transection. The challenges of recovering from SCI have been broadly divided into four areas: 1) cell survival; 2) axon regeneration (growth); 3) correct targeting by growing axons; and 4) establishment of correct and functional synaptic appositions. After acute SCI, there seems to be a therapeutic window of opportunity within which the devastating consequences of the secondary injury can be ameliorated. This is supported by several observations in which apoptotic glial cells have been identified up to 1 week after acute SCI. Moreover, autopsy studies have identified anatomically preserved but unmyelinated axons that could potentially subserve normal physiological properties. These observations suggest that therapeutic strategies after SCI can be directed into two broad modalities: 1) prevention or amelioration of the secondary injury, and 2) restorative or regenerative interventions. Intraspinal transplants have been used after SCI as a means for restoring the severed neuraxis. Fetal cell transplants and, more recently, progenitor cells have been used to restore intraspinal circuitry or to serve as relay for damaged axons. In an attempt to remyelinate anatomically preserved but physiologically disrupted axons, newer therapeutic interventions have incorporated the transplantation of myelinating cells, such as Schwann cells, oligodendrocytes, and olfactory ensheathing cells. Of these cells, the olfactory ensheathing cells have become a more favorable candidate for extensive remyelination and axonal regeneration. Olfactory ensheathing cells are found along the full length of the olfactory nerve, from the basal lamina of the epithelium to the olfactory bulb, crossing the peripheral nervous system-central nervous system junction. In vitro, these cells promote robust axonal growth, in part through cell adhesion molecules and possibly by secretion of neurotrophic growth factors that support axonal elongation and extension. In animal models of SCI, transplantation of ensheathing cells supports axonal remyelination and extensive migration throughout the length of the spinal cord. Although the specific properties of these cells that govern enhanced axon regeneration remain to be elucidated, it seems certain that they will contribute to the establishment of new horizons in SCI research.     

Pharmacological,cell, and gene therapy strategies to promote spinal cord regeneration

In this review, recent studies using pharmacological treatment, cell transplantation, and gene therapy to promote regeneration of the injured spinal cord in animal models will be summarized. Pharmacological and cell transplantation treatments generally revealed some degree of effect on the regeneration of the injured ascending and descending tracts, but further improvements to achieve a more significant functional recovery are necessary. The use of gene therapy to promote repair of the injured nervous system is a relatively new concept. It is based on the development of methods for delivering therapeutic genes to neurons, glia cells, or nonneural cells. Direct in vivo gene transfer or gene transfer in combination with (neuro)transplantation (ex vivo gene transfer) appeared powerful strategies to promote neuronal survival and axonal regrowth following traumatic injury to the central nervous system. Recent advances in understanding the cellular and molecular mechanisms that govern neuronal survival and neurite outgrowth have enabled the design of experiments aimed at viral vector-mediated transfer of genes encoding neurotrophic factors, growth-associated proteins, cell adhesion molecules, and antiapoptotic genes. Central to the success of these approaches was the development of efficient, nontoxic vectors for gene delivery and the acquirement of the appropriate (genetically modified) cells for neurotransplantation. Direct gene transfer in the nervous system was first achieved with herpes viral and El-deleted adenoviral vectors. Both vector systems are problematic in that these vectors elicit immunogenic and cytotoxic responses. Adeno-associated viral vectors and lentiviral vectors constitute improved gene delivery systems and are beginning to be applied in neuroregeneration research of the spinal cord. Ex vivo approaches were initially based on the implantation of genetically modified fibroblasts. More recently, transduced Schwann cells, genetically modified pieces of peripheral nerve, and olfactory ensheathing glia have been used as implants into the injured spinal cord.     

Neuronal populations capable of regeneration following a combined treatment in rats with spinal cord transection

Axonal regeneration after spinal cord injury (SCI) in adult mammals is limited by inhibitors associated with myelin and the glial scar. To overcome these inhibitors, a combined approach will be required. We have previously demonstrated that, following complete SCI in rats, a combination of bridging the lesion with Schwann cell (SC)-filled guidance channels, olfactory ensheathing glia implantation, and chondroitinase ABC delivery promoted regeneration of serotonergic fibers into the lumbar spinal cord. In addition, this combined treatment significantly improved locomotor recovery. To complement these findings, we repeated this combined treatment to assess whether fibers other than serotonergic axons were able to regenerate into the caudal spinal cord. In this experiment, we injected the retrograde tracer FluoroGold (FG) into the spinal cord caudal to a complete transection in a control and a treated group. FG-positive cells rostral to the lesion and in the brainstem of animals in the treated group showed that axons were able to regenerate across the SC bridge and into the caudal spinal cord. Treated rats had labeled cells in the reticulospinal nuclei, vestibular nuclei, and the raphe nucleus as well as in the spinal cord. Cell numbers were highest in the thoracic spinal cord and the lateral vestibular nucleus. Determining the mechanisms for the superior capability of these cell populations to regenerate may provide valuable clues in the design of future treatment approaches.     

Neural precursors as a cell source to repair the demyelinated spinal cord

Schwann cells and neural precursor cells derived from adult human brain (subventricular zone) and from bone marrow were studied anatomically and physiologically after transplantation into the demyelinated rat spinal cord. All cell types formed myelin and restored conduction velocity. Following transection of the dorsal funiculus, Schwann cells and olfactory ensheathing cells facilitated axonal regeneration and restoration of conduction across the lesion site. There is discussion on the challenges of cell type selection and preparation for a potential clinical cell therapy study in human demyelinating diseases.     

Influences of olfactory ensheathing cells transplantation on axonal regeneration in spinal cord of adult rats

Objective: To observe whether offactory ensheathing cells could be used to promote axonal regeneration in a slmntaneously nonregenerating system. Methods: After laminectomy at the lower thoracic level, the spinal cords of adult rats were exposed and completely transected at T10. A suspension of ensheathing cells was injected into the lesion site in 12 adult rats, and control D/F-12 (1:1 mixture of DMEM and Ham‘s F-12) was injected in 12 adult rats. Six weeks and ten weeks after cell transplantation, the rats were evaluated by climbing test and motor evoked potentials (MEPs) monitoring. The samples were procured and studied with histologiel and immounohistochemical methods. Results: At the 6th week after cell transplantation,d the rats in both the transplanted and control groups were paraplegic and the MEPs could not be recorded. At the 10th week after cell transplantation, of 7 rats in the control group, 2 rats had muscles‘ contraction of the lower extremities, 2 rats had hips and/or knees‘ active movement; and 5 rats‘ MEPs could be recorded in the hind limbs in the transplanted group ( n = 7). None of the rats in the control group had functional improvement and no MEPs recorded ( n = 7 ). Numerous regenerating axons were observed through the transplantation and continued to regenerate into the denervated host tract. Cell labelling using anti-Myelin Basic Protein (MBP) and anti-Nerve Growth Factor Receptor (anti-NGFR) indicated that the regenerated axons were derived from the appropriate neuronal source and that donor cells migrated into the denervated host tract. But axonal degeneration existed and regenerating axons were not observed within the spinalcords of the adult rats with only D/F-12 injection. Conclusions: The axonal regeneration in the transected adult rat spinal cord is possible after eusheathing cells transplantation.     

Present situation and future aspects of spinal cord regeneration

The central nervous system (CNS) has a limited capacity for regeneration after injury. In spinal cord injury (SCI) patients, total loss of all motor and sensory function occurs below the level of injury. Advances in treatment are expected for orthopedic and spinal surgeons. Recently, evidence of axonal regeneration and functional recovery has been reported in animal spinal cord injury models. Our studies on the roles of inhibitory molecules with a comparison between neonatal and adult animals may help serve as therapeutic targets to enhance axonal regeneration for the injured spinal cord. Also, our cell replacement study indicates the possibility of transplanting neural stem cells to supply the cell source for immature oligodendrocytes, which are thought to be essential for both the myelination and trophic support of regenerating axons in the spinal cord. Administration of neurotrophic factors, prevention of inhibitory factors, and stem cell technology have clinical applications in SCI patients. However, spinal cord regeneration involves a multistep process, and several factors have to be controlled after injury. A combination of several treatments could overcome a nonpermissive environment for spinal cord regeneration. Further understanding of the mechanisms and finding optimal targets of spinal cord regeneration are necessary to obtain successful therapies for SCI patients.Presented at the 76th Annual Meeting of the Japanese Orthopaedic Association, Kanazawa, Japan, May 23, 2003     

Bioengineered strategies for spinal cord repair

This article reviews bioengineered strategies for spinal cord repair using tissue engineered scaffolds and drug delivery systems. The pathophysiology of spinal cord injury (SCI) is multifactorial and multiphasic, and therefore, it is likely that effective treatments will require combinations of strategies such as neuroprotection to counteract secondary injury, provision of scaffolds to replace lost tissue, and methods to enhance axonal regrowth, synaptic plasticity, and inhibition of astrocytosis. Biomaterials have major advantages for spinal cord repair because of their structural and chemical versatility. To date, various degradable or non-degradable biomaterial polymers have been tested as guidance channels or delivery systems for cellular and non-cellular neuroprotective or neuroregenerative agents in experimental SCI. There is promise that bioengineering technology utilizing cellular treatment strategies, including Schwann cells, olfactory ensheathing glia, or neural stem cells, can promote repair of the injured spinal cord. This review is divided into three parts: (1) degradable and non-degradable biomaterials; (2) device design; and (3) combination strategies with scaffolds. We will show that bioengineering combinations of cellular and non-cellular strategies have enhanced the potential for experimental SCI repair, although further pre-clinical work is required before this technology can be translated to humans.     

嗅球组织块和细胞悬液移植对脊髓损伤的修复

目的探讨嗅球组织块与嗅球细胞悬液髓内移植修复脊髓损伤的可行性和疗效。方法将Wistar大鼠做成脊髓半切模型,随机分成3组,髓内分别移植嗅球组织块、嗅球细胞悬液及DMEM培养液,分期进行功能联合行为学评分(CBS)及组织学检查,评价对脊髓修复情况。结果嗅球组织块与嗅球细胞悬液髓内移植3周后各时段CBS评分明显高于DMEM组(P<0.05),组织学显示前两组有嗅鞘细胞修复的轴突再生。结论嗅球组织块与嗅球细胞悬液髓内移植修复脊髓损伤不但简化了操作而且有较好的疗效,为临床应用提供了实验依据。