Peripheral glial cell differentiation from neurospheres derived from adipose mesenchymal stem cells

Mesenchymal stem cells derived from bone marrow and adipose tissue are being considered for use in neural repair because they can differentiate after appropriate induction in culture into neurons and glia. The question we asked was if neurospheres could be harvested from adipose-derived stem cells and if they then could differentiate in culture to peripheral glial-like cells. Here, we demonstrate that adipose-derived mesenchymal stem cells can form nestin-positive non-adherent neurosphere cellular aggregates when cultured with basic fibroblast growth factor and epidermal growth factor. Dissociation of these neurospheres and removal of mitogens results in expression of the characteristic Schwann cell markers S100 and p75 nerve growth factor receptor and GFAP. The simultaneous expression of these glia markers are characteristic features of Schwann cells and olfactory ensheathing cells which have unique properties regarding remyelination and enhancement of axonal regeneration. When co-cultured with dorsal root ganglion neurons, the peripheral glial-like cells derived from adipose mesenchymal stem cells aligned with neuritis and stimulated neuritic outgrowth. These results indicate that neurospheres can be generated from adipose-derived mesenchymal stem cells, and upon mitogen withdrawal can differentiate into peripheral glial cells with neurotrophic effects.     

BDNF-GFP转染神经干细胞修复大鼠脊髓损伤：发挥干细胞与神经因子的双重效应？

摘要 背景：神经干细胞移植入大鼠脊髓损伤模型可以促进功能恢复,基因治疗已被广泛用于治疗脊髓损伤。 目的：确定BDNF-GFP转染后神经干细胞移植对大鼠脊髓损伤的修复效果。 设计,时间和背景：本实验是在中国医科大学基础医学院发育生物学实验室与2009年5月至2010年1月完成。 材料：10只新生Wistar大鼠和88只2-3个月大,雌雄不限的Wistar大鼠。 方法：以携带BDNF-GFP基因的腺病毒转染神经干细胞。88只Wistar大鼠中假手术组8只, 80只大鼠制成T9左侧横断模型,并随机分成四组：BDNF和GFP修饰的神经干细胞移植组,GFP修饰的神经干细胞移植组;单纯神经干细胞移植组和模型组。在各神经干细胞移植组,脊髓损伤后向横断处显微注射等体积细胞,模型组在相同的部位注射等体积的PBS。 主要观察指标： BBB评分检测脊髓损伤模型运动功能恢复情况;制备脊髓损伤模型2周后取材,免疫组化评估BDNF-GFP转染的神经干细胞移植后的细胞学特点;制备脊髓损伤模型2、4、6、8周Real-time PCR检测脊髓横断处BDNF表达情况。 结果： BDNF-GFP转染后神经干细胞在脊髓半切模型中存活并表达BDNF和GFP,移植该细胞后的大鼠体内高表达具有生物活性的BDNF,且脊髓损伤动物运动功能较对照组明显恢复。 结论：移植BDNF-GFP转染后神经干细胞可能是一种修复脊髓损伤的有效的方法。 关键词：神经干细胞,脑源性神经营养因子;绿色荧光蛋白;脊髓损伤;移植。     

The interaction of stem cells and vascularity in peripheral nerve regeneration

The degree of nerve regeneration after peripheral nerve injury can be altered by the microenvironment at the site of injury. Stem cells and vascularity are postulated to be a part of a complex pathway that enhances peripheral nerve regeneration; however, their interaction remains unexplored. This review aims to summarize current knowledge on this interaction, including various mechanisms through which trophic factors are promoted by stem cells and angiogenesis. Angiogenesis after nerve injury is stimulated by hypoxia, mediated by vascular endothelial growth factor, resulting in the growth of preexisting vessels into new areas. Modulation of distinct signaling pathways in stem cells can promote angiogenesis by the secretion of various angiogenic factors. Simultaneously, the importance of stem cells in peripheral nerve regeneration relies on their ability to promote myelin formation and their capacity to be influenced by the microenvironment to differentiate into Schwann-like cells. Stem cells can be acquired through various sources that correlate to their differentiation potential, including embryonic stem cells, neural stem cells, and mesenchymal stem cells. Each source of stem cells serves its particular differentiation potential and properties associated with the promotion of revascularization and nerve regeneration. Exosomes are a subtype of extracellular vesicles released from cell types and play an important role in cell-to-cell communication. Exosomes hold promise for future transplantation applications, as these vesicles contain fewer membrane-bound proteins, resulting in lower immunogenicity. This review presents pre-clinical and clinical studies that focus on selecting the ideal type of stem cell and optimizing stem cell delivery methods for potential translation to clinical practice. Future studies integrating stem cell-based therapies with the promotion of angiogenesis may elucidate the synergistic pathways and ultimately enhance nerve regeneration.     

Role of stem cells in the regeneration and repair of peripheral nerves

Peripheral nerve regeneration is a complex process, with Wallerian degeneration the most elementary reaction and Schwann cells playing an important role. In recent years, stem cells have been widely used to repair injured peripheral nerves. The sources of these stem cells are widespread and their effectiveness in the treatment of peripheral nerve injury may lie in their ability to differentiate into Schwann cells, secrete neurotrophic factors, and assist in myelin formation. Stem cells have been used as seed cells in tissue-engineered nerve grafts. The understanding of stem cell homing, novel repair material, and the ability to mobilize endogenous stem cells to assist peripheral nerve regeneration constitute a research direction of great interest.     

Human umbilical cord blood-derived mesenchymal stem cells promote regeneration of crush-injured rat sciatic nerves

Several studies have demonstrated that human umbilical cord blood-derived mesenchymal stem cells can promote neural regeneration following brain injury. However, the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells in guiding peripheral nerve regeneration remain poorly understood. This study was designed to investigate the effects of human umbilical cord blood-derived mesenchymal stem cells on neural regeneration using a rat sciatic nerve crush injury model. Human umbilical cord blood-derived mesenchymal stem cells (1 × 10 6 ) or a PBS control were injected into the crush-injured segment of the sciatic nerve. Four weeks after cell injection, brain-derived neurotrophic factor and tyrosine kinase receptor B mRNA expression at the lesion site was increased in comparison to control. Furthermore, sciatic function index, Fluoro Gold-labeled neuron counts and axon density were also significantly increased when compared with control. Our results indicate that human umbilical cord blood-derived mesenchymal stem cells promote the functional recovery of crush-injured sciatic nerves.     

间充质干细胞移植修复脊髓损伤的研究现状

骨髓间充质干细胞在体外没有外界因素作用下连续传50代仍可保持原来的特性,亦可在一些条件的诱导下分化成神经细胞。实验研究表明,间充质干细胞移植能促进脊髓损伤的神经结构修复及神经功能恢复,其机制可能与替代作用、营养作用、诱导作用、桥接作用等有关。携带外源功能基因的骨髓间充质干细胞移植到体内存活、迁徙、分化并基因表达脑源性生长因子、神经生长因子等细胞因子,明显促进脊髓损伤的恢复,成为了新的研究热点。随着对间充质干细胞的生物学特性进一步深入研究,一些未解决的问题将会逐步得到解决,为脊髓损伤和其他神经系统疾病的患者带来新的希望。     

视神经损伤与组织工程修复技术*★

视神经由视网膜神经节细胞轴索组成，因其周围无许旺细胞，属于中枢神经，故损伤后不能再生。1985年So和Aguayo进行周围神经视网膜移植成功,彻底改变了视神经损伤后不能再生的观念。目前神经损伤修复的方法有以下几种：①采用神经营养因子，如神经生长因子、睫状神经营养因子、脑源性神经营养因子等，这些因子具有促进视网膜神经节细胞再生和修复的作用。②基因矫正治疗与基因调控治疗通过改变宿主基因的表达，减少疾病所产生的效应，减缓疾病病程进展或提供对疾病的保护。③神经干细胞移植与组织工程化许旺细胞移植。但这些治疗方法尚处于动物实验阶段，如何及时有效地减少节细胞的凋亡和提高节细胞的存活率，在此基础上进一步促进神经的再生与修复，至今还没有一个完善的方法。     

Extracellular matrix from human umbilical cord-derived mesenchymal stem cells as a scaffold for peripheral nerve regeneration

The extracellular matrix, which includes collagens, laminin, or fibronectin, plays an important role in peripheral nerve regeneration. Recently, a Schwann cell-derived extracellular matrix with classical biomaterial was used to mimic the neural niche. However, extensive clinical use of Schwann cells remains limited because of the limited origin, loss of an autologous nerve, and extended in vitro culture times. In the present study, human umbilical cord-derived mesenchymal stem cells (hUCMSCs), which are easily accessible and more proliferative than Schwann cells, were used to prepare an extracellular matrix. We identiifed the morphology and function of hUCMSCs and investi-gated their effect on peripheral nerve regeneration. Compared with a non-coated dish tissue culture, the hUCMSC-derived extracellular matrix enhanced Schwann cell proliferation, upregulated gene and protein expression levels of brain-derived neurotrophic factor, glial cell-derived neurotrophic factor, and vascular endothelial growth factor in Schwann cells, and enhanced neurite outgrowth from dorsal root ganglion neurons. These ifndings suggest that the hUCMSC-derived extracellular matrix promotes peripheral nerve repair and can be used as a basis for the rational design of engineered neural niches.     

骨髓干细胞移植梗死心肌区域交感神经重构的研究与进展

心肌梗死后存在着交感神经重构现象，表现为交感神经再生和过度再生。交感神经的过度再生与心肌梗死慢性期室性心律失常和猝死的发生关系密切。骨髓干细胞心肌移植可增加有功能的心肌细胞数目，体外研究表明骨髓干细胞可促进神经元的生长，植入动物心肌梗死心脏后，可使神经生长因子生成增多，其交感神经密度增加。干细胞植入心肌后刺激心肌神经萌生的机制仍不明确，干细胞植入后是否有神经细胞形成再迁移至心肌梗死远隔区，另外有可能是干细胞分化成过表达神经营养因子和其他生长因子的细胞，转而刺激神经萌生还需探讨。目前骨髓干细胞移植所面临的问题包括移植时选用的细胞类型、横向分化的调控机制不明、移植时机及移植方式、移植的安全性等。     

Neural stem cells constitutively secrete neurotrophic factors and promote extensive host axonal growth after spinal cord injury

Neural stem cells (NSCs) offer the potential to replace lost tissue after nervous system injury. This study investigated whether grafts of NSCs (mouse clone C17.2) could also specifically support host axonal regeneration after spinal cord injury and sought to identify mechanisms underlying such growth. In vitro, prior to grafting, C17.2 NSCs were found for the first time to naturally constitutively secrete significant quantities of several neurotrophic factors by specific ELISA, including nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. When grafted to cystic dorsal column lesions in the cervical spinal cord of adult rats, C17.2 NSCs supported extensive growth of host axons of known sensitivity to these growth factors when examined 2 weeks later. Quantitative real-time RT-PCR confirmed that grafted stem cells expressed neurotrophic factor genes in vivo. In addition, NSCs were genetically modified to produce neurotrophin-3, which significantly expanded NSC effects on host axons. Notably, overexpression of one growth factor had a reciprocal effect on expression of another factor. Thus, stem cells can promote host neural repair in part by secreting growth factors, and their regeneration-promoting activities can be modified by gene delivery.     

Influence of endogenous ciliary neurotrophic factor on neural differentiation of adult rat hippocampal progenitors

Ciliary neurotrophic factor is the only known neurotrophic factor that can promote differentiation of hippocampal neural progenitor cells to glial cells and neurons in adult rats. This process is similar to spontaneous differentiation. Therefore, ciliary neurotrophic factor may be involved in spontaneous differentiation of neural stem cells. To verify this hypothesis, the present study isolated neural progenitor cells from adult male rats and cultured them in vitro. Results showed that when neural progenitor cells were cultured in the absence of mitogen fibroblast growth factor-2 or epidermal growth factor, they underwent spontaneous differentiation into neurons and glial cells. Western blot and immunocytochemical staining showed that exogenous ciliary neurotrophic factor strongly induced adult hippocampal progenitor cells to differentiate into neurons and glial cells. Moreover, passage 4 adult hippocampal progenitor cells expressed high levels of endogenous ciliary neurotrophic factor, and a neutralizing antibody against ciliary neurotrophic factor prevented the spontaneous neuronal and glial differentiation of adult hippocampal progenitor cells. These results suggest that the spontaneous differentiation of adult hippocampal progenitor cells is mediated partially by endogenous ciliary neurotrophic factor.     

Human umbilical cord mesenchymal stem cells promote peripheral nerve repair via paracrine mechanisms

Human umbilical cord-derived mesenchymal stem cells(h UCMSCs) represent a promising young-state stem cell source for cell-based therapy. h UCMSC transplantation into the transected sciatic nerve promotes axonal regeneration and functional recovery. To further clarify the paracrine effects of h UCMSCs on nerve regeneration, we performed human cytokine antibody array analysis, which revealed that h UCMSCs express 14 important neurotrophic factors. Enzyme-linked immunosorbent assay and immunohistochemistry showed that brain-derived neurotrophic factor, glial-derived neurotrophic factor, hepatocyte growth factor, neurotrophin-3, basic fibroblast growth factor, type I collagen, fibronectin and laminin were highly expressed. Treatment with h UCMSC-conditioned medium enhanced Schwann cell viability and proliferation, increased nerve growth factor and brain-derived neurotrophic factor expression in Schwann cells, and enhanced neurite growth from dorsal root ganglion explants. These findings suggest that paracrine action may be a key mechanism underlying the effects of h UCMSCs in peripheral nerve repair.     

腺病毒载体Ad-BDNF-EGFP构建及其在神经干细胞中的表达

摘要 目的 研究腺病毒载体Ad-BDNF -EGFP的构建及在神经干细胞（NSCs）中的表达。方法 通过RT-PCR从在大鼠的海马中获得BDNF基因,通过基因克隆以及HEK293包装,获得了含增强绿色荧光蛋白(EGFP)基因的重组腺病毒表达载体pAd-BDNF-EGFP,将其感染原代培养的神经干细胞,观察EGFP及BDNF两种基因的表达,镜下测定转染率,并检测RT-PCR产物,证实BDNF的存在。转染后的神经干细胞经G418筛选,抗性细胞传代扩增后获得成功转染BDNF基因的NSCs克隆。结果 荧光显微镜下可见感染后的NSCs表达EGFP而发出绿色荧光;通过RT-PCR证明感染后的NSCs具有表达BDNF的能力;用ELISA鉴定细胞上清中分泌的BDNF, 72h的含量达到最高值,为12.78ng/ml;证明通过构建病毒的感染可以使神经干细胞获得分泌BDNF的能力,且EGFP基因可作为神经干细胞移植研究中良好的示踪剂。结论 腺病毒病毒介导EGFP基因及BDNF基因在大鼠胚胎神经干细胞中成功表达,为应用以神经干细胞直接作为基因靶细胞,介导基因治疗中枢神经系统疾病莫定了基础。     

Peripheral nerve injury induced changes in the spinal cord and strategies to counteract/enhance the changes to promote nerve regeneration

Peripheral nerve injury leads to morphological, molecular and gene expression changes in the spinal cord and dorsal root ganglia, some of which have positive impact on the survival of neurons and nerve regeneration, while the effect of others is the opposite. It is crucial to take prompt measures to capitalize on the positive effects of these reactions and counteract the negative impact after peripheral nerve injury at the level of spinal cord, especially for peripheral nerve injuries that are severe, located close to the cell body, involve long distance for axons to regrow and happen in immature individuals. Early nerve repair, exogenous supply of neurotrophic factors and Schwann cells can sustain the regeneration inductive environment and enhance the positive changes in neurons. Administration of neurotrophic factors, acetyl-L-carnitine, N-acetyl-cysteine, and N-methyl-D-aspartate receptor antagonist MK-801 can help counteract axotomy-induced neuronal loss and promote regeneration, which are all time-dependent. Sustaining and reactivation of Schwann cells after denervation provides another effective strategy. FK506 can be used to accelerate axonal regeneration of neurons, especially after chronic axotomy. Exploring the axotomy-induced changes after peripheral nerve injury and applying protective and promotional measures in the spinal cord which help to retain a positive functional status for neuron cell bodies will inevitably benefit regeneration of the peripheral nerve and improve functional outcomes.     

Don't fence me in: harnessing the beneficial roles of astrocytes for spinal cord repair

Astrocytes comprise a heterogeneous cell population that plays a complex role in repair after spinal cord injury. Reactive astrocytes are major contributors to the glial scar that is a physical and chemical barrier to axonal regeneration. Yet, consistent with a supportive role in development, astrocytes secrete neurotrophic factors and protect neurons and glia spared by the injury. In development and after injury, local cues are modulators of astrocyte phenotype and function. When multipotent cells are transplanted into the injured spinal cord, they differentiate into astrocytes and other glial cells as opposed to neurons, which is commonly viewed as a challenge to be overcome in developing stem cell technology. However, several examples show that astrocytes provide support and guidance for axonal growth and aid in improving functional recovery after spinal cord injury. Notably, transplantation of astrocytes of a developmentally immature phenotype promotes tissue sparing and axonal regeneration. Furthermore, interventions that enhance endogenous astrocyte migration or reinvasion of the injury site result in greater axonal growth. These studies demonstrate that astrocytes are dynamic, diverse cells that have the capacity to promote axon growth after injury. The ability of astrocytes to be supportive of recovery should be exploited in devising regenerative strategies.     

Exogenous nerve growth factor protects the hypoglossal nerve against crush injury

Studies have shown that sensory nerve damage can activate the p38 mitogen-activated protein kinase(MAPK)pathway,but whether the same type of nerve injury after exercise activates the p38MAPK pathway remains unclear.Several studies have demonstrated that nerve growth factor may play a role in the repair process after peripheral nerve injury,but there has been little research focusing on the hypoglossal nerve injury and repair.In this study,we designed and established rat models of hypoglossal nerve crush injury and gave intraperitoneal injections of exogenous nerve growth factor to rats for 14 days.p38MAPK activity in the damaged neurons was increased following hypoglossal nerve crush injury;exogenous nerve growth factor inhibited this increase in acitivity and increased the survival rate of motor neurons within the hypoglossal nucleus.Under transmission electron microscopy,we found that the injection of nerve growth factor contributed to the restoration of the morphology of hypoglossal nerve after crush injury.Our experimental findings indicate that exogenous nerve growth factor can protect damaged neurons and promote hypoglossal nerve regeneration following hypoglossal nerve crush injury.     

Transplantation of olfactory ensheathing cells for promoting regeneration following spinal cord injury

OBJECTIVE: To investigate the status of olfactory ensheathing cells (OECs) transplantation in facilitating the regeneration of spinal cord injury. DATA SOURCES: Articles about OECs transplantation in treating spinal cord injury were searched in Pubmed database published in English from January 1981 to December 2005 by using the keywords of "olfactory ensheathing cells, transplantation, spinal cord injury". STUDY SELECTION: The data were checked primarily, literatures related to OECs transplantation and the regeneration of spinal cord injury were selected, whereas the repetitive studies and reviews were excluded. DATA EXTRACTION: Totally 43 articles about OECs transplantation and the regeneration and repair of spinal cord injury were collected, and the repetitive ones were excluded. DATA SYNTHESIS: There were 35 articles accorded with the criteria. OECs are the olfactory ensheathing glias isolated from olfactory bulb and olfactory nerve tissue. OECs have the characters of both Schwann cells in central nervous system and peripheral astrocytes. The transplanted OECs can migrate in the damaged spinal cord of host, can induce and support the regeneration, growth and extension of damaged neuritis. Besides, transgenic technique can enable it to carry some exogenous genes that promote neuronal regeneration, and express some molecules that can facilitate neural regeneration, so as to ameliorate the internal environment of nerve injury, induce the regeneration of damaged spinal cord neurons, which can stimulate the regeneration potential of the damaged spinal cord to reach the purpose of spinal cord regeneration and functional recovery. CONCLUSION: OECs are the glial cells with the energy for growth at mature phase, they can myelinize axons, secrete various biological nutrition factors, and then protect and support neurons, also facilitate neural regeneration. OECs have been successfully isolated from nasal olfactory mucosa and olfactory nerve. Therefore, autologous transplantation of OECs and objective genes modified OECs carrying various neurotrophic factors may become an effective method to treat spinal cord injury in the future.     

Application of neurotrophic and proangiogenic factors as therapy after peripheral nervous system injury

The intrinsic ability of peripheral nerves to regenerate after injury is extremely limited,especially in case of severe injury.This often leads to poor motor function and permanent disability.Existing approaches for the treatment of injured nerves do not provide appropriate conditions to support survival and growth of nerve cells.This drawback can be compensated by the use of gene therapy and cell therapy-based drugs that locally provide an increase in the key regulators of nerve growth,including neurotrophic factors and extracellular matrix proteins.Each growth factor plays its own specific angiotrophic or neurotrophic role.Currently,growth factors are widely studied as accelerators of nerve regeneration.Particularly noteworthy is synergy between various growth factors,that is essential for both angiogenesis and neurogenesis.Fibroblast growth factor 2 and vascular endothelial growth factor are widely known for their proangiogenic effects.At the same time,fibroblast growth factor 2 and vascular endothelial growth factor stimulate neural cell growth and play an important role in neurodegenerative diseases of the peripheral nervous system.Taken together,their neurotrophic and angiogenic properties have positive effect on the regeneration process.In this review we provide an in-depth overview of the role of fibroblast growth factor 2 and vascular endothelial growth factor in the regeneration of peripheral nerves,thus demonstrating their neurotherapeutic efficacy in improving neuron survival in the peripheral nervous system.     

Transplantation of olfactory ensheathing cells for promoting regeneration following spinal cord injury

OBJECTIVE： To investigate the status of olfactory ensheathing cells （OECs） transplantation in facilitating the regeneration of spinal cord injury. DATA SOURCES： Articles about OECs transplantation in treating spinal cord injury were searched in Pubmed database published in English from January 1981 to December 2005 by using the keywords of ＂olfactory ensheathing cells, transplantation, spinal cord injury＂. STUDY SELECTION： The data were checked primarily, literatures related to OECs transplantation and the regeneration of spinal cord injury were selected, whereas the repetitive studies and reviews were excluded. DATA EXTRACTION： Totally 43 articles about OECs transplantation and the regeneration and repair of spinal cord injury were collected, and the repetitive ones were excluded. DATA SYNTHESIS： There were 35 articles accorded with the criteria. OECs are the olfactory ensheathing glias isolated from olfactory bulb and olfactory nerve tissue. OECs have the characters of both Schwann cells in central nervous system and peripheral astrocytes. The transplanted OECs can migrate in the damaged spinal cord of host, can induce and support the regeneration, growth and extension of damaged neuritis. Besides, transgenic technique can enable it to carry some exogenous genes that promote neuronal regeneration, and express some molecules that can facilitate neural regeneration, so as to ameliorate the internal environment of nerve injury, induce the regeneration of damaged spinal cord neurons, which can stimulate the regeneration potential of the damaged spinal cord to reach the purpose of spinal cord regeneration and functional recovery. CONCLUSION： OECs are the glial cells with the energy for growth at mature phase, they can myelinize axons, secrete various biological nutrition factors, and then protect and support neurons, also facilitate neural regeneration. OECs have been successfully isolated from nasal olfactory mucosa and olfactory nerve. Therefore, autologous transplantation of OECs and objective genes modified OECs carrying various neurotrophic factors may become an effective method to treat spinal cord injury in the future.     

Repair of peripheral nerve defects with chemically extracted acellular nerve allografts loaded with neurotrophic factors-transfected bone marrow mesenchymal stem cells

Chemically extracted acellular nerve allografts loaded with brain-derived neurotrophic factor-transfected or ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells have been shown to repair sciatic nerve injury better than chemically extracted acellular nerve allografts alone, or chemically extracted acellular nerve allografts loaded with bone marrow mesenchymal stem cells. We hypothesized that these allografts compounded with both brain-derived neurotrophic factor- and ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells may demonstrate even better effects in the repair of peripheral nerve injury. We cultured bone marrow mesenchymal stem cells expressing brain-derived neurotrophic factor and/or ciliary neurotrophic factor and used them to treat sciatic nerve injury in rats. We observed an increase in sciatic functional index, triceps wet weight recovery rate, myelin thickness, number of myelinated nerve fibers, amplitude of motor-evoked potentials and nerve conduction velocity, and a shortened latency of motor-evoked potentials when allografts loaded with both neurotrophic factors were used, compared with allografts loaded with just one factor. Thus, the combination of both brain-derived neurotrophic factor and ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells can greatly improve nerve injury.