Olfactory ensheathing cells (OECs) and the treatment of CNS injury: advantages and possible caveats

One of the main research strategies to improve treatment for spinal cord injury involves the use of cell transplantation. This review looks at the advantages and possible caveats of using glial cells from the olfactory system in transplant-mediated repair. These glial cells, termed olfactory ensheathing cells (OECs), ensheath the axons of the olfactory receptor neurons. The primary olfactory system is an unusual tissue in that it can support neurogenesis throughout life. In addition, newly generated olfactory receptor neurons are able to grow into the CNS environment of the olfactory bulb tissue and reform synapses. It is thought that this unique regenerative property depends in part on the presence of OECs. OECs share some of the properties of both astrocytes and Schwann cells but appear to have advantages over these and other glial cells for CNS repair. In particular, OECs are less likely to induce hypertrophy of CNS astrocytes. As well as remyelinating demyelinated axons, OEC grafts appear to promote the restoration of functions lost following a spinal cord lesion. However, much of the evidence for this is based on behavioural tests, and the mechanisms that underlie their potential benefits in transplant-mediated repair remain to be clarified.     

Combined transplantation of neural stem cells and olfactory ensheathing cells for the repair of spinal cord injuries

Spinal cord repair is a problem that has long puzzled neuroscientists. The failure of the spinal cord to regenerate and undergo reconstruction after spinal cord injury (SCI) can be attributed to secondary axonal demyelination and neuronal death followed by cyst formation and infarction as well as to the nature of the injury environment, which promotes glial scar formation. Cellular replacement and axon guidance are both necessary for SCI repair. Multipotent neural stem cells (NSCs) have the potential to differentiate into both neuronal and glial cells and are, therefore, likely candidates for cell replacement therapy following SCI. However, NSC transplantation alone is not sufficient for spinal cord repair because the majority of the NSCs engrafted into the spinal cord have been shown to differentiate with a phenotype which is restricted to glial lineages, further promoting glial scaring. Olfactory ensheathing cells (OECs) are a unique type of glial cell that occur both peripherally and centrally along the olfactory nerve. The ability of olfactory neurons to grow axons in the mature central nervous system (CNS) milieu has been attributed to the presence of OECs. It has been shown that transplanted OECs are capable of migrating into and through astrocytic scars and thereby facilitating axonal regrowth through an injury barrier. Given the complementary properties of NSCs and OECs, we predict that the co-transplantation of NSCs and OECs into an injured spinal cord would have a synergistic effect, promoting neural regeneration and functional reconstruction. The lost neurocytes would be replaced by NSCs, while the OECs would build "bridges" crossing the glial scaring that conduct axon elongation and promote myelinization simultaneously. Furthermore, the two types of cells could first be seeded into a bioactive scaffold and then the cell seeded construct could be implanted into the defect site. We believe that this type of treatment would lead to improved neural regeneration and functional reconstruction after SCI.     

嗅鞘细胞静脉移植治疗脊髓损伤

背景：嗅鞘细胞移植治疗脊髓损伤在众多疗法中效果较佳,成为最有前景的治疗方法之一。目前移植方法为局部移植,存在操作复杂、创伤大、重复移植治疗困难等缺点。寻找一种简单易行且疗效好的移植方法成为各国学者研究的热点。 目的：分析嗅鞘细胞静脉移植治疗脊髓损伤的可行性和疗效。 方法：制备Wistar大鼠脊髓半切模型,随机分4组：嗅鞘细胞髓内局部移植组、嗅鞘细胞静脉移植组、D/F12静脉移植组和空白对照组。定期行CBS功能评分及组织学检查,评价脊髓修复情况。 结果与结论：嗅鞘细胞髓内局部移植组、嗅鞘细胞静脉移植组的功能恢复和组织学改变优于D/F12静脉移植组和空白对照组,嗅鞘细胞髓内局部移植组、嗅鞘细胞静脉移植组间无显著差别。说明嗅鞘细胞静脉移植可向脊髓损伤部位迁移并修复脊髓损伤,其疗效与嗅鞘细胞髓内局部移植相当。     

嗅鞘细胞移植和左旋硝基精氨酸对大鼠脊髓损伤后背核神经元存活及其轴突再生的影响

目的 探讨嗅鞘细胞(OECs)移植和一氧化氮合酶(NOS)抑制剂左旋硝基精氨酸(LNNA)对大鼠脊髓损伤后,背核神经元存活及其轴突再生的影响.方法 将20只大鼠行脊髓半横断术后分为对照组、OECs组、L-NNA组和OECs L-NNA组.OECs L-NNA组在脊髓损伤处移植嗅鞘细胞,并注射L-NNA.术后30d时,应用NADPH酶组织化学、免疫组织化学、中性红染色、HE染色和荧光金逆行标记等方法,观察4组大鼠L1背核神经元存活及其轴突再生情况.结果 1.0ECs组、L-NNA组L1背核神经元存活数量均高于对照组,且分类计数显示,这两组对脊髓背核大、中、小神经元的存活均有促进作用,而OECs L-NNA组的促存活作用最显著.2.0ECs组和OECs L-NNA组脊髓损伤处可见再生的轴突,且L1背核可观察到被荧光金逆行标记的神经元胞体.3.与对照组比较,OECs组L1背核NOS阳性神经元增加,L-NNA组NOS阳性神经元减少,OECs L-NNA组NOS阳性神经元数量差异不明显.结论 嗅鞘细胞移植和L-NNA均可促进脊髓受损伤背核神经元的存活,两者联合应用可更好地促进受损伤的背核神经元存活及其轴突再生.     

Morphological and functional plasticity of olfactory ensheathing cells

In the primary olfactory pathway, olfactory ensheathing cells (OECs) extend processes to envelop bundles of olfactory axons as they course towards their termination in the olfactory bulb. The expression of growth-promoting adhesion and extracellular matrix molecules by OECs, and their spatially close association with olfactory axons are consistent with OECs being involved in promoting and guiding olfactory axon growth. Because of this, OECs have been employed as a possible tool for inducing axonal regeneration in the injured adult CNS, resulting in significant functional recovery in some animal models and promising outcomes from early clinical applications. However, fundamental aspects of OEC biology remain unclear. This brief review discusses some of the experimental data that have resulted in conflicting views with regard to the identity of OECs. We present here recent findings which support the notion of OECs as a single but malleable phenotype which demonstrate extensive morphological and functional plasticity depending on the environmental stimuli. The review includes a discussion of the normal functional role of OECs in the developing primary olfactory pathway as well as their interaction with regenerating axons and reactive astrocytes in the novel environment of the injured CNS. The use of OECs to induce repair in the injured nervous system reflects the functional plasticity of these cells. Finally, we will explore the possibility that recent microarray data could point to OECs assuming an innate immune function or playing a role in modulating neuroinflammation.     

Therapeutic effect of co-transplantation of neuregulin 1-transfected-Schwann cells and bone marrow stromal cells on spinal cord hemisection syndrome

The aim of this present study is to evaluate the therapeutic effect of co-transplantation of neuregulin-1-transfected-Schwann cells (SCs) and bone marrow stromal cells (BMSCs) on a rat model of spinal cord hemi-section injuries (Brown–Séquard syndrome), which is relevant to human clinical spinal cord injury. Both in vivo and in vitro data we received demonstrated that co-transplantation BMSCs with NRG1-transfected SCs reduced the size of cystic cavities, promoted axonal regeneration and hind limb functional recovery in comparison with SCs or BMSCs transplantation alone or together, and this treatment could provide important insights into potential therapies of spinal cord hemi-section injuries.     

自体嗅鞘细胞联合β-七叶皂甙钠修复大鼠脊髓全横断损伤

背景：神经损伤时移植嗅鞘细胞能促进轴突再生,减少星形胶质细胞增生。 目的：探讨自体嗅鞘细胞移植联合中药β-七叶皂甙钠对脊髓继发性损伤的保护作用。 方法：制作SD大鼠脊髓损伤模型,随机分为对照组(注射生理盐水)、自体嗅鞘细胞移植组、自体嗅鞘细胞移植联合β-七叶皂甙钠治疗组。 结果与结论：脊髓损伤后脊髓血管源性水肿、基质金属蛋白酶9表达上调,大鼠运动功能缺失,经自体嗅鞘细胞移植及自体嗅鞘细胞联合β-七叶皂甙钠治疗后脊髓水肿明显减轻、基质金属蛋白酶9表达下调,大鼠运动功能恢复,以自体嗅鞘细胞移植联合β-七叶皂甙钠治疗效果更明显。说明自体嗅鞘细胞移植联合β-七叶皂甙钠可更有效修复损伤脊髓,发挥保护作用。     

移植微囊化嗅鞘细胞对神经病理性疼痛及L4-5段脊髓P2X7受体表达的影响

目的 探讨微囊化嗅鞘细胞移植对坐骨神经损伤引起病理性疼痛及L4-5段脊髓P2X7受体的表达影响。 方法 取1只健康SD大鼠,取其嗅球组织并运用差速贴壁方法,在体外进行嗅鞘细胞培养扩增。取48只健康SD大鼠,随机分成4组,即对照组（control）、慢性压迫性坐骨神经损伤组（CCI）、嗅鞘细胞移植组（OECs）及微囊化嗅鞘细胞移植组（MC-OECs）。术后7 d及14 d,运用行为学方法检测各组大鼠机械缩足反射阈值,运用原位杂交方法检测各组大鼠L4-5段脊髓P2X7受体阳性细胞百分比及平均吸光度表达情况。 结果 术后7 d及14 d,与对照组比较,CCI组大鼠机械缩足反射阈值明显减低,L4-5段脊髓P2X7受体阳性细胞百分比及平均吸光度明显增加（P<0.05）;与CCI组比,OECs组大鼠机械缩足反射阈值明显增高,P2X7受体阳性细胞百分比及平均吸光度明显减低（P<0.05）,与OECs组对比,MC-OECs组大鼠机械缩足反射更高。P2X7受体阳性细胞百分比及平均吸光度更低（P<0.05）。 结论 微囊化嗅鞘细胞移植能更好地缓解神经病理性疼痛,减低L4-5段脊髓内P2X7受体的表达水平,修复坐骨神经损伤。     

成年大鼠嗅球和鼻腔嗅粘膜成鞘细胞的分离、培养与鉴定

目的　在嗅球成鞘细胞 (OECs)移植到脊髓可有助于损伤神经纤维再生的基础上 ,分别对嗅球和嗅粘膜的OECs进行培养 ,探索自体嗅粘膜作为OECs供体的可能性。　方法　根据OECs、成纤维细胞和星形胶质细胞贴壁时间的不同 ,采用差时贴壁方法分离出OECs,培养 14div后进行NGFRp75和GDNF的免疫细胞化学染色。　结果　按形态学和免疫组织化学特性 ,培养的嗅球和嗅粘膜OECs可分为 3类 :双极细胞、三级细胞和扁圆细胞 ,其中以双极细胞最多。嗅粘膜的双极成鞘细胞的突起更加细长。　结论　差时贴壁细胞分离法是一种简单、经济、实用的成鞘细胞分离方法。鼻腔嗅粘膜OECs的形态学和免疫细胞化学特性与嗅球OECs基本相同 ,本实验为临床开展自体嗅粘膜OECs修复脊髓损伤的研究提供参考     

移植微囊化嗅鞘细胞对P2X2、P2X3受体介导神经病理性疼痛影响的实验研究

目的 探讨微囊化嗅鞘细胞移植对大鼠P2X2、P2X3受体介导神经病理性疼痛在L_4～5段脊髓表达的影响。方法 2014年9月—2015年7月采用差速贴壁法培养SD大鼠嗅球来源的嗅鞘细胞并进行传代扩增,取第9代嗅鞘细胞免疫荧光染色鉴定细胞纯度,符合要求后制作微囊化嗅鞘细胞。按随机化要求将48只健康SD大鼠随机分成对照组、模型组、嗅鞘细胞移植组(OECs组)、微囊化嗅鞘细胞移植组(MC-OECs组),每组12只。模型组、OECs组、MC-OECs组建立SD大鼠坐骨神经损伤的动物模型,OECs组、MC-OECs组分别将吸附嗅鞘细胞悬液和微囊化嗅鞘细胞悬液的可吸收明胶海绵置于坐骨神经损伤两侧,于术后第7、14天取各组SD大鼠的L_4～5段脊髓,采用原位杂交技术观察对比各组P2X2、P2X3受体阳性细胞的表达情况。结果 原位杂交结果显示,P2X2、P2X3受体主要表达于脊髓灰质中,以细胞核表达明显,细胞质内少量表达。术后第7、14天模型组、OECs组、MC-OECs组和对照组P2X2、P2X3受体的阳性细胞百分比及细胞平均吸光度均依次降低,且各组间比较,差异均有统计学意义(P值均<0.05)。结论 MC-OECs移植能明显降低坐骨神经损伤动物模型脊髓内P2X2、P2X3受体的表达水平,具有抑制P2X2、P2X3受体介导的神经病理性疼痛的作用。     

人骨髓间质干细胞和嗅鞘细胞移植对大鼠急性脊髓损伤功能修复的比较研究

目的对比人骨髓基质细胞(BMSCs)与人胚嗅鞘细胞(OECs)移植对大鼠脊髓损伤功能修复的影响。方法将45只SD大鼠分成脊髓损伤后BMSCs移植组(BMSCs组)、OECs移植组(OECs组)和PBS对照组(PBS组),通过BBB评分、运动诱发电位(MEP)评估脊髓传导功能的改善状况,免疫组织化学方法检测移植细胞存活和分化情况,病理形态学方法观察组织结构修复情况。结果BMSCs组BBB评分高于OECs组(P<0.05);两细胞治疗组MEP潜伏期明显缩短(P<0.05);BMSCs组嗜银染色可见脊髓损伤近端有较多再生纤维向远端延伸,形成神经纤维束,而OECs组再生纤维较少;两种移植细胞均可在损伤处部分存活,BMSCs组可见BMSCs来源的细胞Nestin、NF、GFAP的阳性表达。结论BMSCs移植比OECs移植能更有效促进大鼠急性脊髓损伤修复。     

Use of a cell line to investigate olfactory ensheathing cell-enhanced axonal regeneration

Olfactory ensheathing cells (OECs), a unique type of macroglia required for normal olfactory axonal regeneration throughout the lifetime of an individual, have been shown to have regeneration-enhancing properties when used to treat various neuronal injuries. Availability of OECs is a hurdle facing future clinical use of the cells for spinal cord injury (SCI) therapy. The number of OECs that can realistically be harvested from each animal is limited, and ensuring a pure cell population is difficult. We have begun to characterize a nonsyngeneic strain of OECs, i.e., from a homogenous OEC clonal cell line (nOECs). The purpose of this study was to determine whether nOECs have the same properties and provide the same functional recovery after SCI, as primary cultures of OECs. The results indicate that nOECs survive in vivo, produce growth-promoting proteins, and possess regeneration-promoting capabilities. Spinal cord injured rats that were treated with nOECs performed significantly better on functional tests than injured control animals beginning at 5 weeks after operation. In summary, evidence of nOEC regeneration-promoting capabilities suggests that this cell line can be used as potential therapy in SCI research.     

嗅鞘细胞移植联合督脉电针治疗大鼠前脊髓综合征

背景：电针在脊髓损伤的康复过程中有其一定的临床作用,同时以嗅鞘细胞为代表的细胞治疗在部分患者的康复过程中亦起到了一定的作用,两者是否具有协同应用尚不清楚。 目的：观察督脉电针联合嗅鞘细胞移植对前脊髓综合征大鼠神经营养因子3水平及P75NTR表达的影响。 方法：将40只成年大鼠随机分为对照组、督脉电针组、嗅鞘细胞移植组、督脉电针+嗅鞘细胞移植组,经嗅鞘细胞移植和督脉电针治疗2周后 ELISA法检测脊髓组织神经营养因子3水平,免疫组化检测P75NTR的表达。 结果与结论：督脉电针+嗅鞘细胞移植组神经营养因子3水平较对照组及其他实验组高(P < 0.05);嗅鞘细胞移植组和督脉电针+嗅鞘细胞移植组的脊髓损伤部位以及相邻的组织内均有P75NTR表达,且督脉电针+嗅鞘细胞移植组阳性表达明显较嗅鞘细胞移植组多。实验证实督脉电针联合嗅鞘细胞移植能够明显增高大鼠前脊髓综合征邻近组织的神经营养因子3水平;督脉电针可以有效促进移植的嗅鞘细胞在宿主内存活。     

嗅鞘细胞移植脊髓全横断损伤大鼠大脑皮质运动区转化生长因子β表达的影响

背景：多项研究已证实嗅鞘细胞能促进脊髓损伤大鼠神经功能的恢复,但其分子机制还不清楚。 目的：观察嗅鞘细胞移植对脊髓全横断大鼠大脑皮质运动区转化生长因子β mRNA表达的影响。 方法：采用酶消化法培养GFP转基因小鼠嗅鞘细胞,制成细胞悬液。建立SD大鼠T9脊髓全横断模型,造模后分为假手术组、模型组和嗅鞘细胞移植组。应用RT-PCR方法检测各组大鼠大脑皮质运动区转化生长因子β mRNA的表达变化,用β-actin作内参。 结果与结论：模型组大鼠造模后3 d大脑皮质运动区转化生长因子β mRNA的表达量高于假手术组(P < 0.05),造模后7,14,21和28 d回到假手术组水平。嗅鞘细胞移植后21 d,嗅鞘细胞移植组转化生长因子β mRNA的表达量低于模型组(P < 0.05)。提示全横断脊髓损伤致大脑皮质运动区转化生长因子β mRNA早期表达上调,随后与假手术组相比无差别;嗅鞘细胞移植后期可逆转转化生长因子β mRNA的表达变化,有助于脊髓损伤的恢复。     

不同时间点静脉移植嗅鞘细胞修复脊髓损伤

背景:嗅鞘细胞具有促进轴突再生、为受伤的宿主细胞提供营养支持以及调节炎症反应的能力,是修复脊髓损伤具有潜力的细胞。目的:探讨通过静脉移植嗅鞘细胞治疗脊髓损伤的最佳移植时间窗。方法:SPF雄性SD大鼠30只,采用脊髓半横断建立大鼠脊髓损伤模型,并随机分为5组:脊髓损伤后注射嗅鞘细胞1 d移植组、3 d移植组、7 d移植组、10 d移植组及PBS对照组。应用荧光量子点标记嗅鞘细胞;分别于1,3,7,10 d时间点通过尾静脉移植应用量子点标记的嗅鞘细胞;PBS对照组脊髓损伤后注射PBS。注射后1 d取损伤处的脊髓;应用小动物成像仪测定不同时间点转移到损伤处荧光的数值,通过荧光的强度衡量转移到损伤处细胞的量;应用嗅鞘细胞Anti-p75 NGF Receptor抗体做损伤处脊髓的免疫组织化学。实验方案经宁夏医科大学动物实验伦理委员会批准(编号:2017-073)。结果与结论:①荧光量子点可以标记嗅鞘细胞;②荧光测定结果与免疫组织化学染色结果:1,3,7,10 d时间点通过尾静脉移植的嗅鞘细胞均有细胞转移到损伤处,7 d移植的嗅鞘细胞转移到损伤处的最多;③结果说明,脊髓损伤不同时间点注射的嗅鞘细胞均可以转移到脊髓损伤处,损伤后7 d移植的嗅鞘细胞转移到损伤处的细胞数量最多,可以作为移植的最佳时间窗。     

Schwann cell and olfactory ensheathing cell implantation for repair of the contused spinal cord

A contusion injury to the spinal cord results in impaired neurological functions due to neuronal death, and axonal damage and demyelination. In time, a fluid-filled cyst forms at the site of the initial impact. There are no effective endogenous repair mechanisms and, consequently, injury-induced functional deficits are permanent. One aspect of spinal cord repair is that severed descending and ascending axons need to regenerate beyond the site of injury towards the denervated spinal regions where they can become part of axonal circuits involved in motor and sensory function. Implantation of cells into the injured cord has been studied extensively as a means to promote axonal regeneration in the injured spinal cord. Depending on the overall damage, different cell types may be appropriate in different types of injury. To accomplish axonal regeneration in the contused spinal cord, the strengths and limitations of two glial cell types in particular will be discussed; Schwann cells and olfactory ensheathing cells. It is known that with these implants, axonal regeneration is frustrated by the presence of a glial scar surrounding the contused area. I will review current approaches aimed at overcoming this axonal growth inhibitory scar. Future studies need to focus on identifying interventions that, in combination with cellular implants, will elicit substantial axonal growth beyond the contusion injury, which may then be the basis for biologically significant functional recovery.     

一种新颖的神经胶质细胞-嗅鞘细胞

嗅鞘细胞(OECs)移植治疗脊髓损伤(SC I)已显示出良好的应用前景,不同来源的OECs体外培养时,在不同发育阶段和不同生长环境中具有不同的生物学特性。OECs具有特异性的标志蛋白,如S-100、p75NTR、GFAP等。体外培养的OECs分泌NGF、BDNF、NT-3/4、GDNF等多种促进神经细胞生长、分化和神经纤维再生的神经营养因子。将OECs植入脊髓损伤部位,该细胞能分裂增殖,并可抑制胶质瘢痕的形成,拮抗Nogo等神经再生抑制性因子的活性,包绕再生轴突形成髓鞘。由于OECs具有上述独特的生物学功能,被认为是继神经干细胞和雪旺氏细胞之后可用于移植治疗脊髓损伤的一种新颖的神经胶质细胞。     

Transplantation of olfactory ensheathing cells fails to promote significant axonal regeneration from dorsal roots into the rat cervical cord

The olfactory ensheathing cell (OEC) is a class of glial cell that has been reported to support regeneration in the central nervous system after various types of lesions, including rhizotomy of spinal dorsal roots at thoracic, lumbar and sacral levels. We have therefore carried out a detailed anatomical analysis to assess the efficacy of dorsal horn OEC transplants at promoting regeneration of primary afferents across the dorsal root entry zone (DREZ) at the cervical level in the adult rat. OECs were cultured from adult rat olfactory bulb and immunopurified (90% purity). Regeneration by large diameter afferents and by both peptidergic and non-peptidergic small diameter afferents was assessed using respectively cholera toxin B (CTB) labelling and immunocytochemistry for calcitonin gene-related peptide (CGRP) and the purinoceptor P2X3. Following an extensive (C3-T3) rhizotomy, CGRP and P2X3 immunoreactive axons regenerated across the rhizotomy site as far as the DREZ but there was no evidence of regeneration across the DREZ, except through sites where the OEC transplant was directly grafted into the DREZ. No evidence of regeneration into the dorsal horn by CTB-labelled axons was obtained. In addition, there was little sign of sprouting by intact axons in the vicinity of OEC transplant sites. In contrast to these results in vivo, cocultures of OECs and adult dorsal root ganglion cells showed that OECs stimulate extensive neurite outgrowth. The failure of the OECs to promote regeneration in vivo following cervical rhizotomy is therefore most likely due to factors in the environment of the graft site and/or the method of transplantation.     

Olfactory ensheathing cells: historical perspective and therapeutic potential

Olfactory ensheathing cells (OECs) are the glial cells that ensheath the axons of the first cranial nerve. They are attracting increasing attention from neuroscientists as potential therapeutic agents for use in the repair of spinal cord injury and as a source of myelinating glia for use in remyelinating axons in demyelinating diseases such as multiple sclerosis. This review mainly addresses the cell biological aspects of OECs pertinent to addressing two questions. Namely, where do OECs fit into the groupings of central nervous system (CNS)/peripheral nervous system (PNS) glial cells and should OECs be viewed as a clinically relevant alternative to Schwann cells in the treatment of spinal cord injury? The evidence indicates that OECs are indeed a clinically relevant alternative to Schwann cells. However, much more work needs to be done before we can even come close to answering the first question as to the lineage and functional relationship of OECs to the other types of CNS and PNS glial cells.