Neurotrophic properties of olfactory ensheathing glia

Olfactory ensheathing cells (OEC) constitute a specialized population of glia that accompany primary olfactory axons and have been reported to facilitate axonal regeneration after spinal cord injury in vivo. In the present report we describe OEC neurotrophic factor expression and neurotrophic properties of OECs in vitro. Investigation of the rat olfactory system during development and adulthood by radioactive in situ hybridization revealed positive labeling in the olfactory nerve layer for the neurotrophic molecules S-100beta, CNTF, BMP-7/OP-1, and artemin, as well as for the neurotrophic factor receptors RET and TrkC. Ribonuclease protection assay of cultured OEC revealed expression of NGF, BDNF, GDNF, and CNTF mRNA, while NT3 and NT4 mRNA were not detectable. In vitro bioassays of neurotrophic activity involved coculturing of adult OEC with embryonic chick ganglia and demonstrated increased neurite outgrowth from sympathetic, ciliary, and Remak's ganglia. However, when culturing the ganglia with OEC-conditioned medium, neurite outgrowth was not stimulated to any detectable extent. Our results suggest that the neurotrophic properties of OEC may involve secretion of neurotrophic molecules but that cellular interactions are crucial.     

Expression of neural properties in olfactory cytokeratin-positive basal cell line

A cytokeratin (CK)(+), horizontal basal cell (HBC)-like cell line from murine olfactory epithelium, DBC1.2, was characterized. Histochemically, it is CK14(+), CK18(-), neuron-specific tubulin (NST)(+) and capable of binding Bandeiraea simplicifolia lectin I. RT-PCR studies revealed that it expresses mRNAs for EGF receptor, NST, Pax-6, but not for Mash-1 and neurogenin-1. Retinoic acid reduced the expression of CK14 and CKs recognized by polyclonal anti-keratin antibody, whereas it induced nestin. These results suggest that DBC1.2 shares the properties of HBCs and neural cells.     

嗅鞘细胞的可塑性研究

2004年诺贝尔医学和生理学奖得主Richard Axel和Linda Buck证实：原来认为不具备分化能力的小鼠嗅感觉神经元能够再次进入细胞周期发生分裂．这一发现是嗅觉神经系统可塑性的典型体现。嗅鞘细胞（olfactory ensheathing cells，OECs）作为嗅觉系统内一种特殊类型的胶质细胞．大量研究证实其可促进中枢神经系统（central nervous system．CNS）损伤的修复。但目前对OECs生物学特性的认识仍存在不同观点．其可塑性的研究近年来逐渐受到关注。可塑性指在变化的内外环境刺激下细胞改变自身特性．在形态、抗原表达和功能上呈现很大程度的可变性。目前被证实OECS表达的抗原有S100β、神经生长因子低亲和力受体（p751、胶质纤维酸性蛋白（glial fibrill aryacidicprotein，GFAP）、神经肽Y（neuropeptide Y．NPY）、O4和神经细胞黏附分子（neural cell adhesion molecule，NCAM）等。     

Remyelination after olfactory ensheathing cell transplantation into diverse demyelinating environments

Olfactory ensheathing cells (OECs) can remyelinate demyelinated spinal cord axons when transplanted into chemically induced demyelinated lesions. Cell transplantation is typically performed within a few days after lesion induction, i.e. during active demyelination when myelin debris, cytokine level increases and macrophage/microglia activation is extensive. Inflammatory signaling has been suggested to facilitate remyelination in cell transplant studies. In this review we discuss the migration and remyelination properties of OECs transplanted into various demyelinating lesion environments including conditions when inflammation is active and when it is largely subsided. While sharing many common properties, comparisons of the in vivo fate between OECs and SCs suggest unique properties of OECs as compared to SCs. A complicating factor in the assessment of experimental remyelination by transplantation of myelin-forming cells in general is the rapidity of endogenous myelin repair in most rodent models of demyelination. Alternative persistent demyelination models are discussed as potential tools to study both the competency of chronic demyelinated axons for remyelination and the remyelination potential of cells such as human progenitors that require longer times to mobilize and remyelinate axons. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.     

Glial cell line-derived neurotrophic factor promotes olfactory ensheathing cells migration

Olfactory ensheathing cells (OECs) are a unique type of macroglia with axonal growth-promoting properties. The migrating ability of OECs in CNS is essential for neural regeneration. However, little is known about the extracellular and intracellular factors that regulate OEC migration. In the present study, we examined the effects of glial cell line-derived neurotrophic factor (GDNF) on OECs migration. Initially, the "scratch" migration assay, Boyden chamber assay, and explant migration assay showed that GDNF could promote OECs migration in vitro. Treatment of OECs with GDNF also induced cytoskeleton reorganization and up-regulated expression of cytoskeleton proteins. GDNF-induced OECs migration was demonstrated depending on GFRalpha-1 and Ret receptor, and activation of JNK and Src signaling cascades. Furthermore, GDNF was found to promote implanted OECs migration in a spinal cord hemisection injury model. Together, we report, to our knowledge for the first time, that GDNF stimulate OECs migration in vitro and in vivo.     

Neurosphere cell differentiation to aldynoglia promoted by olfactory ensheathing cell conditioned medium

Cells from central nervous system with morphology similar to radial glia and properties intermediate between astrocytes and Schwann cells were called growth‐promoting glia or aldynoglia. These cells are present in adult brain olfactory bulb, hypothalamus, hypophysis, pineal gland and in the developing brain, and spinal cord (Cameron and Rakic ( 1991 ) Glia 4:124–137; Gudiño‐Cabrera and Nieto‐Sampedro ( 2000 ) 30:49–63). We report now that neurosphere cells, abundantly generated from E15 rat or E13 mouse corpus striatum, differentiate to aldynoglia‐like cells when plated onto an adhesive substrate, and cultured in the presence of olfactory ensheathing cell conditioned medium, supplemented with EGF and bFGF. The immunophenotype, mRNA expression (microarray and RT‐PCR analysis), neurite growth‐promoting and ensheathing properties of the cells derived from neurospheres were similar to those of aldynoglia. Neurosphere‐derived, aldynoglia‐like cells expressed, with respect to neurospheres, very increased levels of GFAP, high levels of nestin and vimentin, extracellular matrix proteins, and inhibitors of the catabolism of those extracellular matrix proteins. © 2009 Wiley‐Liss, Inc.     

Insights into olfactory ensheathing cell development from a laser-microdissection and transcriptome-profiling approach

Olfactory ensheathing cells (OECs) are neural crest-derived glia that ensheath bundles of olfactory axons from their peripheral origins in the olfactory epithelium to their central targets in the olfactory bulb. We took an unbiased laser microdissection and differential RNA-seq approach, validated by in situ hybridization, to identify candidate molecular mechanisms underlying mouse OEC development and differences with the neural crest-derived Schwann cells developing on other peripheral nerves. We identified 25 novel markers for developing OECs in the olfactory mucosa and/or the olfactory nerve layer surrounding the olfactory bulb, of which 15 were OEC-specific (that is, not expressed by Schwann cells). One pan-OEC-specific gene, Ptprz1, encodes a receptor-like tyrosine phosphatase that blocks oligodendrocyte differentiation. Mutant analysis suggests Ptprz1 may also act as a brake on OEC differentiation, and that its loss disrupts olfactory axon targeting. Overall, our results provide new insights into OEC development and the diversification of neural crest-derived glia.     

Delayed olfactory ensheathing cell transplants reduce nociception after dorsal root injury

Injury to cervical dorsal roots mimics the deafferentation component of brachial plexus injury in humans, with intractable neuropathic pain in the deafferented limb being a common consequence. Such lesions are generally not amenable to surgical repair. The use of olfactory ensheathing cells (OECs) for dorsal root repair, via acute transplantation, has been successful in several studies. From a clinical point of view, delayed transplantation of OECs would provide a more realistic timeframe for repair. In this study we investigated the effect of delayed OEC transplantation on functional recovery of skilled forepaw movements and amelioration of neuropathic pain, using a C7 and C8 dorsal root injury rat model previously established in our lab. We found that OEC transplantation to the dorsal horn 1 week after root injury effectively attenuated neuropathic disturbances associated with dorsal root injury, including spontaneous pain behavior, tactile allodynia and thermal hyperalgesia. The sensory controls of complex, goal-oriented skilled reaching and ladder walking, however, were not improved by delayed OEC transplantation. We did not detect any significant influence of transplanted OECs on injury-induced central reorganisation and afferent sprouting. The anti-nociceptive effect mediated by OEC transplants may therefore be explained by alternative mechanisms such as modification of inflammation and astrogliosis. The significant effect of OEC transplants in mitigating neuropathic pain may be clinically useful in intractable pain syndromes arising from deafferentation. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.     

Comparative gene expression profiling of olfactory ensheathing cells from olfactory bulb and olfactory mucosa

Olfactory ensheathing cells (OEC) have the ability to promote regeneration in the nervous system. Hence, they hold promise for cell therapy. Most of the experimental studies have investigated the role of OECs taken from olfactory bulb (OB). However, for a clinical human application, olfactory mucosa (OM) seems to be the only acceptable source for OECs. Many studies have compared the distinct ability of OECs from OB and OM to improve functional nerve regeneration after lesion of the nervous system. Nevertheless, the two populations of OECs may differ in several points, which might affect all fate after transplantation in vivo. We report here the first study which compares gene expression profiling between these two populations of OECs. It appears that OB‐OECs and OM‐OECs display distinct gene expression pattern, which suggest that they may be implicated in different physiological processes. Notably, OM‐OECs overexpress genes characteristic of wound healing and regulation of extra cellular matrix. In contrast, OB‐OECs gene profile suggests a prominent role in nervous system development. Hence, OB‐OECs and OM‐OECs fundamentally differ in their gene expression pattern, which may represent a crucial point for future clinical application. © 2010 Wiley‐Liss, Inc.     

嗅鞘细胞条件培养液中神经生长因子的保护作用

背景：近年研究证实嗅鞘细胞具有支持和促进多种神经元存活和轴突再生的作用,与其分泌的神经营养活性物质相关,如神经生长因子、脑源性神经营养因子等。神经营养活性物质在维持神经元存活、生长以及损伤后修复与再生方面的作用值得关注。 目的：探讨神经生长因子是否在嗅鞘细胞条件培养液的神经保护中发挥重要作用。 设计、时间及地点：细胞学体外对照观察,于2006-01/2007-03在解放军南京军区南京总医院神经内科实验室完成。 材料：成年SD大鼠30只用于嗅鞘细胞培养,出生24 h内的SD乳鼠60只用于脑海马神经元培养。 方法：采用差速贴壁法纯化大鼠嗅鞘细胞,添加Forskolin和碱性成纤维细胞生长因子促进细胞增殖,培养至10 d,取生长状态良好的细胞,按1×109 L-1密度接种,待细胞贴壁后加入含B27的Neurobasal培养基,48 h后收集上清液。待所有嗅鞘细胞条件培养液收集完毕后,将其混合,低温离心后收集浓缩的嗅鞘细胞条件培养液,-80 ℃保存备用。取体外分离培养的乳鼠脑海马神经元,设立正常组、谷氨酸损伤模型组、嗅鞘细胞条件培养液组、抗神经生长因子抗体+嗅鞘细胞条件培养液组。 主要观察指标：海马神经元活性,上清液中乳酸脱氢酶浓度,神经元凋亡率。 结果：与正常组比较,其余3组神经元活性均明显下降（P < 0.05或0.01）;与谷氨酸损伤模型组比较,嗅鞘细胞条件培养液组、抗神经生长因子抗体+嗅鞘细胞条件培养液组神经元活性均明显增高（P < 0.01或0.05）,且前者升高幅度大于后者（F=5.85,P < 0.05）。与正常组比较,其余3组乳酸脱氢酶浓度及神经元凋亡率均明显增高（P < 0.05或0.01）;与谷氨酸损伤模型组比较,嗅鞘细胞条件培养液组、抗神经生长因子抗体+嗅鞘细胞条件培养液组乳酸脱氢酶浓度及神经元凋亡率均明显下降（P < 0.01或0.05）,且前者下降幅度大于后者（F =5.04,F =5.16,P < 0.05）。 结论：嗅鞘细胞条件培养液可提高损伤海马神经元活性,抑制上清液中乳酸脱氢酶释放和神经元凋亡;消除神经生长因子后,以上保护作用减弱,提示嗅鞘细胞条件培养液中存在多种营养物质共同发挥神经保护作用,尤以神经生长因子为重。     

不同来源嗅鞘细胞移植治疗脑出血的比较

背景：嗅鞘细胞是目前已知用于移植细胞中惟一可以跨越周围神经系统与中枢神经系统边界的细胞。在众多的国内外文献中,大多以嗅球来源嗅鞘细胞作为观察对象;但采用嗅黏膜嗅鞘细胞移植具有来源方便、损伤小、可自体取材等优势。 目的：比较嗅球来源嗅鞘细胞和嗅黏膜嗅鞘细胞移植对脑出血后神经功能损伤恢复作用的差异。 设计、时间及地点：免疫组织化学水平的随机对照动物实验,于2005-10/2007-10在无锡市第三人民医院细胞实验室完成。 材料：选用健康雄性SD大鼠30只,按随机数字表法分为3组,对照组、嗅球来源嗅鞘细胞移植组及嗅黏膜嗅鞘细胞移植组各10只。 方法：分别获取人鼻中隔黏膜、人胚嗅球,进行嗅鞘细胞的分离培养纯化,取培养10 d的细胞用作细胞移植。取SD大鼠制备尾状核出血模型,嗅球来源嗅鞘细胞移植组及嗅黏膜嗅鞘细胞移植组各取10μL细胞悬液在立体定向下引导微量注射器向大鼠脑组织内匀速注射(1 μL/min),对照组注入等量培养基,注射点为右侧尾状核。 主要观察指标：观察两种来源嗅鞘细胞的体外培养情况。嗅鞘细胞移植后对动物行定期行为学评定,功能损伤越重,得分越高;并观察组织切片靶区域免疫细胞化学分析结果。 结果：从体外培养结果看,无论在形态上还是表型上,两者无明显区别。嗅球来源嗅鞘细胞移植组及嗅黏膜嗅鞘细胞移植组大鼠的Longa 5分制法及前肢放置试验评分在移植后第14,28,56天显著低于对照组（P < 0.05）,两移植组差异无显著性意义（P > 0.05）,移植组各时间段差异无显著性意义（P > 0.05）。 结论：用于移植修复神经功能的两种嗅鞘细胞在细胞特性、移植效果方面均无明显差异。     

嗅鞘细胞移植修复大鼠脊髓损伤的组织病理学变化☆

背景：对于脊髓损伤,目前临床尚无有效的治疗对策,近年来嗅鞘细胞移植对脊髓损伤修复取得了一定的进展。 目的：观察嗅鞘细胞移植在缓解损伤脊髓的病理反应和超微结构变化,及其在发生发展中的作用。 方法：60只大鼠随机分为空白组,模型组,嗅鞘胞移植组和DF12组,每组15只。空白组：仅切开T10全椎板及T9,T11部分椎板,对脊髓未作其他处理,明胶海绵轻柔压迫止血;模型组：仅切断脊髓,未作特殊处理;嗅鞘细胞移植组和DF12组：切断脊髓后用微量注射器分别注射嗅鞘细胞和DF12培养液,随后缝合切口。脊髓损伤后1,3,7,14,28,42,56 d每组麻醉2只受检大鼠,取材做光镜观察和电镜观察。 结果与结论：单纯脊髓横切损伤后,发生了出血、水肿、变性、坏死以及囊腔形成,胶质细胞增生和神经纤维再生。嗅鞘细胞移植后,明显减轻了神经元和神经纤维的坏死变性程度,减轻病理反应,并能对损伤神经元实施保护;防止了胶质细胞过度增生形成瘢痕屏障,明显增加了再生神经纤维的数量。提示嗅鞘细胞移植对损伤脊髓具有减轻病理反应和促进修复的作用。     

壳聚糖与大鼠嗅鞘细胞的生物相容性

背景：众多研究证实,嗅鞘细胞移植和生物导管在修复中枢神经系统损伤中发挥了显著的作用,课题组前期研究已证实了壳聚糖在大鼠体内神经系统具有良好的生物相容性。 目的：观察壳聚糖与大鼠嗅鞘细胞的生物相容性。 设计、时间及地点：体外细胞学对比观察,于2005-12/2006-05在武汉协和医院泌尿外科实验室完成。 材料：将壳聚糖粉溶于10 g/L的乙酸溶液中,配制成10 g/L的壳聚糖溶液;显微剥离成年大鼠嗅球表面层,按常规方法行原代细胞培养。 方法：实验分为3组,每组10孔。壳聚糖组将制备好的壳聚糖溶液0.1 mL加入到培养板中,50 ℃烘箱至成膜干燥,加入40 g/L氢氧化钠溶液中和乙酸,双蒸水漂洗,晾干即可。多聚赖氨酸组按常规方法赖氨酸包被培养板。未包被组不用任何材料包被。将原代培养的嗅鞘细胞分别接种至壳聚糖包被、多聚赖氨酸包被和未包被的培养板上进行培养。 主要观察指标：于培养第3,5天显微镜下观察细胞形态学变化,MTT比色实验检测细胞存活和增殖状况。 结果：嗅鞘细胞可在壳聚糖膜上贴壁生长,细胞形态及数量与未包被组相比差异无显著性意义,但与多聚赖氨酸组相比细胞数量偏低。 结论：嗅鞘细胞与壳聚糖有良好的生物相容性。     

Adult olfactory bulbs from primates provide reliable ensheathing glia for cell therapy

Olfactory bulb ensheathing glia (OB-OEG) from adult rodents promote functional and morphological repair after grafting into injured spinal cords. To provide insight into the feasibility of using OB-OEG in human therapy, we studied OB-OEG in primates to determine their suitability for spinal cord transplantation. Here, we show that OEG can be obtained from olfactory bulbs of adult macaca mulatta and nemestrina monkeys and compare their characteristics to those obtained from rats. In contrast to rodent OB-OEG, primate OB-OEG are nonsenescent, exhibit a longer lifespan, are less sensitive to high oxygen culture environment, and maintain a phenotype suitable for grafting for up to 2.5 months in vitro. Three-week cultures (short term) derived from a single macaca olfactory bulb provide enough OEG for autologous transplantation at the acute stage of injury, and after long-term cultures (2.5 months) may yield an additional 20 billion. OEG can be frozen for later use. Therefore, primate adult olfactory bulbs constitute a reliable source of OEG for cell therapy, and successful culture of these cells make autologous transplantation feasible.     

胰酶限时消化在嗅鞘细胞培养中的运用

目的探索出一套高效、实用的大鼠嗅球嗅鞘细胞(OECs)的培养和纯化方案。方法分离SD大鼠嗅球的外两层组织,剪切消化成细胞悬液进行接种。采用3种方法进行OECs的培养和纯化:(1)A组分别经6h、24h两次差速贴壁去除杂质细胞,培养至12d左右消化重悬细胞进行爬片分析。(2)B组分别经6h、24h两次差速贴壁去除杂质细胞,培养至12d左右经胰酶限时消化,留成纤维细胞于瓶壁,重悬的细胞进行爬片分析。(3)C组采用经典的Nash法(分别经18h、36h两次差速贴壁去除杂质细胞),培养至11d左右消化重悬细胞进行爬片分析。采用NGFRP75与碘化丙啶(PI)双染的方法进行OECs的鉴定和纯度分析。结果在共聚焦显微镜下呈双染阳性的细胞为OECs,OECs多数突起细长,呈双极或三极,少量呈单极或多极。A、B、C组所纯化的OECs纯度分别为(67.3±6.2)%、(83.7±7.7)%和(74.6±9.5)%,3组间比较有统计学差异(F=13.633,P<0.01),B组所得OECs纯度均较另两组高(P<0.05)。结论经6h、24h两次差速贴壁+胰酶限时消化可以获得较高纯度的OECs,能够满足动物实验的需要。     

嗅鞘细胞移植治疗脊髓损伤的临床验证

背景: 一系列基础研究证实在动物脊髓损伤的模型中,嗅鞘细胞移植能够促进脊髓损伤的再生和恢复脊髓的部分神经功能。部分临床实验证明嗅鞘细胞的移植的确能改善脊髓损伤患者的神经功能,从而改善其生活质量。 目的：验证嗅鞘细胞移植对脊髓损伤患者神经功能修复的作用及安全性。 方法：取流产胚胎嗅球并消化成为单个嗅鞘细胞,培养纯化2周左右,制成嗅鞘细胞悬液。选择脊髓损伤患者213例,全麻下将制备好的嗅鞘细胞悬液采用区域性多靶点注射方法移植于损伤脊髓的周围。采用ASIA量表对患者移植前1d及移植后3周~2个月进行评分,评价患者脊髓恢复状况。 结果与结论：所有患者的脊髓神经功能于术后3周均有不同程度的改变,脊髓功能评分及感觉与运动功能均较移植前明显提高(P < 0.001),且随时间延长呈不断改善趋势;最长患者随访5年,未见已恢复的神经功能 减退及移植不良反应。证实嗅鞘细胞移植对脊髓损伤患者的神经功能恢复有促进作用,可以部分恢复及改善其部分脊髓神经功能,且治疗方法安全。     

Olfactory ensheathing cells from the nasal mucosa and olfactory bulb have distinct membrane properties

Transplantation of olfactory ensheathing cells (OECs) is a potential therapy for the regeneration of damaged neurons. While they maintain tissue homeostasis in the olfactory mucosa (OM) and olfactory bulb (OB), their regenerative properties also support the normal sense of smell by enabling continual turnover and axonal regrowth of olfactory sensory neurons (OSNs). However, the molecular physiology of OECs is not fully understood, especially that of OECs from the mucosa. Here, we carried out whole-cell patch-clamp recordings from individual OECs cultured from the OM and OB of the adult rat, and from the human OM. A subset of OECs from the rat OM cultured 1–3 days in vitro had large weakly rectifying K⁺ currents, which were sensitive to Ba²⁺ and desipramine, blockers of Kir4-family channels. Kir4.1 immunofluorescence was detectable in cultured OM cells colabeled for the OEC marker S100, and in S100-labeled cells found adjacent to OSN axons in mucosal sections. OECs cultured from rat OB had distinct properties though, displaying strongly rectifying inward currents at hyperpolarized membrane potentials and strongly rectifying outward currents at depolarized potentials. Kir4.1 immunofluorescence was not evident in OECs adjacent to axons of OSNs in the OB. A subset of human OECs cultured from the OM of adults had membrane properties comparable to those of the rat OM that is dominated by Ba²⁺-sensitive weak inwardly rectifying currents. The membrane properties of peripheral OECs are different to those of central OECs, suggesting they may play distinct roles during olfaction.     

Extracellular matrix protein anosmin‐1 modulates olfactory ensheathing cell maturation in chick olfactory bulb development

Olfactory ensheathing cells (OECs) are a specialized class of glia, wrapping around olfactory sensory axons that target the olfactory bulb (OB) and cross the peripheral nervous system/central nervous system boundary during development and continue to do so post‐natally. OEC subpopulations perform distinct subtype‐specific functions dependent on their maturity status. Disrupted OEC development is thought to be associated with abnormal OB morphogenesis, leading to anosmia, a defining characteristic of Kallmann syndrome. Hence, anosmin‐1 encoded by Kallmann syndrome gene (KAL‐1) might modulate OEC differentiation/maturation in the OB. We performed in ovo electroporation of shRNA in the olfactory placode to knock‐down kal in chick embryos, resulting in abnormal OB morphogenesis and loss of olfactory sensory axonal innervation into OB. BLBP‐expressing OECs appeared to form a thinner and poorly organized outmost OB layer where SOX10 expressing OECs were completely absent with emergence of GFAP‐expressing OECs. Furthermore, in embryonic day 10 chick OB explant cultures, GFAP expression in OECs accumulating along the OB nerve layers was dramatically reduced by recombinant anosmin‐1. We then purified immature OECs from embryonic day 10 chick OB. These cells express GFAP after 7 days in vitro, exhibiting a multipolar morphology. Overexpression of chick anosmin, exogenous anosmin‐1 or FGF2 could inhibit GFAP expression with cells presenting elongated morphology, which was blocked by the FGF receptor inhibitor Su5402. These data demonstrate that anosmin‐1 functions via FGF signalling in regulating OEC maturation, thereby providing a permissive glial environment for axonal innervation into the OB during development.