Immunomodulation by neural stem cells

Neural (stem) cell transplantation has been proposed as a means of cell replacement therapy. Multipotential neural precursor cells (NPCs) that expand in floating spheres, and are (partially) committed to a glial fate, showed excellent remyelinating properties in a focal, chemically induced demyelinated lesion in the rat spinal cord. When transplanted into the CNS of rodents with acute and chronic EAE the NPCs were attracted by the inflammatory process to migrate exclusively into inflamed white matter but not into adjacent gray matter. Following magnetic labeling, mouse NPCs and human ESC-derived neural precursors' migration was detected by high-resolution magnetic resonance images. Intraventricular transplantation of neural spheres attenuated brain inflammation in acute and chronic EAE, reduced the clinical severity of disease, and reduced demyelination and axonal pathology. Intravenous (IV) NPC injection also inhibited EAE and reduced CNS inflammation and tissue injury. However, NPCs did not enter the CNS but were transiently found in lymph nodes and spleen, where they inhibited the activation and proliferation of T cells and markedly reduced their encephalitogenicity. Thus, IV administration of neural precursors inhibits EAE by a peripheral immunosuppression, involving a profound bystander inhibitory effect of NPCs on T cell activation and proliferation in lymph nodes. In conclusion, neural precursor cells exert an immunomodulatory effect that inhibits CNS inflammation. Cell therapy in MS should be optimized to utilize both regenerative and immunologic properties of the cells.     

Neural progenitor cells transplanted into the uninjured brain undergo targeted migration after stroke onset

Endogenous neural stem cells normally reside in their niche, the subventricular zone, in the uninjured rodent brain. Upon stroke, these cells become more proliferative and migrate away from the subventricular zone into the surrounding parenchyma. It is not known whether this stroke-induced behavior is due to changes in the niche or introduction of attractive cues in the infarct zone, or both. A related question is how transplanted neural stem cells respond to subsequent insults, including whether exogenous stem cells have the plasticity to respond to subsequent injuries after engraftment. We addressed this issue by transplanting neural progenitor cells (NPCs) into the uninjured brain and then subjecting the animal to stroke. We were able to follow the transplanted NPCs in vivo by labeling them with superparamagnetic iron oxide particles and imaging them via high-resolution magnetic resonance imaging (MRI) during engraftment and subsequent to stroke. We find that transplanted NPCs that are latent can be activated in response to stroke and exhibit directional migration into the parenchyma, similar to endogenous neural NPCs, without a niche environment.     

Time limited immunomodulatory functions of transplanted neural precursor cells

Fetal neural stem/precursor cells (NPCs) possess powerful immunomodulatory properties which enable them to protect the brain from immune‐mediated injury. A major issue in developing neural stem/precursor cell (NPC) therapy for chronic neuroinflammatory disorders such as multiple sclerosis is whether cells maintain their immune‐regulatory properties for prolonged periods of time. Therefore, we studied time‐associated changes in NPC immunomodulatory properties. We examined whether intracerebrally‐transplanted NPCs are able to inhibit early versus delayed induction of autoimmune brain inflammation and whether allogeneic NPC grafts continuously inhibit host rejection responses. In two experimental designs, intraventricular fetal NPC grafts attenuated clinically and pathologically brain inflammation during early EAE relapse but failed to inhibit the disease relapse if induced at a delayed time point. In correlation, long‐term cultured neural precursors lost their capacity to inhibit immune cell proliferation in vitro. Loss of NPC immune functions was associated with transition into a quiescent undifferentiated state. Also, allogeneic fetal NPC grafts elicited a strong immune reaction of T cell and microglial infiltration and were rejected from the host brain. We conclude that long‐term functional changes in transplanted neural precursor cells lead to loss of their therapeutic immune‐regulatory properties, and render allogeneic grafts vulnerable to immunologic rejection. Thus, the immunomodulatory effects of neural precursor cell transplantation are limited in time. © 2012 Wiley Periodicals, Inc.     

Unique gene expression patterns indicate microglial contribution to neural stem cell recovery following irradiation

Ionizing radiation results in damage to neural stem cells and reduced neurogenesis. The aim of the present study was to determine intrinsic and extrinsic factors that influence neural stem cell survival following irradiation, using qPCR. Gene expression of hippocampal and SVZ neurospheres were analyzed following irradiation, and results demonstrated that irradiated hippocampal and SVZ stem cells displayed similar gene expression profiles for intrinsic genes. Irradiated microglia (extrinsic factor) isolated from the SVZ exhibited increased gene expression of growth factors involved in stem cell maintenance, proliferation, and survival. However, microglial genes in the irradiated hippocampus responded less favorably with respect to stem cell recovery. This might explain the superior recovery of SVZ compared to hippocampal stem cells following in vivo irradiation. In addition, our results show that a combination of growth factors, which were upregulated in SVZ microglia, increased the proliferation and decreased cell death of irradiated neurospheres in vitro.     

神经干细胞移植治疗大鼠脑缺血再灌注损伤实验研究

目的探讨大鼠胚胎神经干细胞移植治疗局灶性脑缺血再灌注损伤的可行性。方法孕龄8~10d的大鼠神经干细胞在体外扩增后,用免疫组织化学方法分别检测神经干细胞及其分化后代的特异性标志蛋白nestin、胶质纤维酸性蛋白(GFAP)和神经元特异性烯醇化酶(NSE)的表达。分别于缺血后不同时间窗将神经干细胞移植到局灶性脑缺血大鼠模型的缺血半暗带和梗塞中心,移植4w后比较不同移植部位神经干细胞存活、增殖和迁移的差异。结果从胎鼠中成功培养出悬浮生长的可表达nestin的神经球,其在含血清条件下可分化为表达GFAP的胶质细胞和表达NSE的神经元。神经干细胞移植4w后可见所有移植动物的细胞都存活,梗塞中心移植的细胞存活、增殖水平明显低于半暗带移植的细胞。结论大鼠胚胎神经干细胞移植到局灶性脑缺血再灌注损伤大鼠梗塞中心和半暗带均可长期存活,其增殖能力与移植部位密切相关。     

大鼠胚胎脑皮层神经干细胞的分离和培养

目的探讨分离、培养、纯化大鼠胚胎神经干细胞(neuralstem cell,NSCs)的最佳条件,以获得充足的神经干细胞来源,用于中枢神经系统疾病的治疗.方法分离孕13～15 d胎鼠大脑皮层,在无血清含神经生长因子N2培养液中培养,利用有限稀释法单克隆培养和改良法连续传代纯化并扩增NSCs,免疫组织化学法对NSCs及分化细胞进行鉴定.结果可以通过体外培养获得大量神经源性干细胞,在体外经多次传代后仍具有很强的增殖能力和多向分化潜能.结论NSCs的存活和分裂依赖于神经生长因子和N2添加剂的浓度,胚胎脑组织和神经球分离方法影响NSCs的形成速度和数量.掌握NSCs的体外纯化培养和鉴定手段可为进一步研究NSCs生物学特性及神经系统损伤的治疗提供新方法.     

Lithium enhances proliferation and neuronal differentiation of neural progenitor cells in vitro and after transplantation into the adult rat spinal cord

Transplantation of neural progenitor cells (NPCs) holds great potential for the treatment of spinal cord injuries. The survival and differential fates of transplanted NPCs in the cord are key factors contributing to the success of the therapy. In this study, we investigate the effects of lithium, a widely used antidepressant drug, on the survival, proliferation and differentiation of spinal cord-derived NPCs in cultures and after transplantation into the spinal cord. Our results show that clinically relevant doses of lithium increase the proliferation of grafted NPCs at 2 weeks post-grafting and neuronal generation by grafted NPCs at 2 weeks and 4 weeks post-grafting. However, lithium does not cause preferential differentiation of NPCs into astrocytes or oligodendrocytes both in vitro and after transplantation. Our results also show that chronic treatment with lithium (up to 4 weeks) reduces microglia and macrophage activation, indicating that lithium treatment can affect the host immune response. The results of the present study provide evidence that lithium may have therapeutic potential in cell replacement strategies for CNS injury due to its ability to promote proliferation and neuronal generation of grafted NPCs and reduce the host immune reaction.     

Neural progenitor cell transplants promote long-term functional recovery after traumatic brain injury

Studies demonstrating the versatility of neural progenitor cells (NPCs) have recently rekindled interest in neurotransplantation methods aimed at treating traumatic brain injury (TBI). However, few studies have evaluated the safety and functional efficacy of transplanted NPCs beyond a few months. The purpose of this study was to assess the long-term survival, migration, differentiation and functional significance of NPCs transplanted into a mouse model of TBI out to 1 year post-transplant. NPCs were derived from E14.5 mouse brains containing a transgene-expressing green fluorescent protein (GFP) and cultured as neurospheres in FGF2-containing medium. Neurospheres were injected into the ipsilateral striatum of adult C57BL/6 mice 1 week following unilateral cortical impact injury. Behavioral testing revealed significant improvements in motor abilities in NPC-treated mice as early as 1 week, and the recovery was sustained out to 1 year post-transplant. In addition, mice receiving NPC transplants showed significant improvement in spatial learning abilities at 3 months and 1 year, whereas an intermediate treatment effect on this behavioral parameter was detected at 1 month. At 14 months post-transplant, GFP(+) NPCs were observed throughout the injured hippocampus and adjacent cortical regions of transplanted brains. Immunohistochemical analysis revealed that the majority of transplanted cells co-labeled for NG2, an oligodendrocyte progenitor cell marker, but not for neuronal, astrocytic or microglial markers. In conclusion, transplanted NPCs survive in the host brain up to 14 months, migrate to the site of injury, enhance motor and cognitive recovery, and may play a role in trophic support following TBI.     

Transplanted neural precursor cells reduce brain inflammation to attenuate chronic experimental autoimmune encephalomyelitis

Stem cell transplantation was introduced as a mean of cell replacement therapy, but the mechanism by which it confers clinical improvement in experimental models of neurological diseases is not clear. Here, we transplanted neural precursor cells (NPCs) into the ventricles of mice at day 6 after induction of chronic experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS). Transplanted cells migrated into white matter tracts and attenuated the clinical course of disease. NPC transplantation down-regulated the inflammatory brain process at the acute phase of disease, as indicated by a reduction in the number of perivascular infiltrates and of brain CD3+ T cells, an increase in the number and proportion of regulatory T cells and a reduction in the expression of ICAM-1 and LFA-1 in the brain. Demyelination and acute axonal injury in this model are considered to result mainly from the acute inflammatory process and correlate well with the chronic neurological residua. In consequence to inhibition of brain inflammation, precursor cell transplantation attenuated the primary demyelinating process and reduced the acute axonal injury. As a result, the size of demyelinated areas and extent of chronic axonal pathology were reduced in the transplanted brains. We suggest that the beneficial effect of transplanted NPCs in chronic EAE is mediated, in part, by decreasing brain inflammation and reducing tissue injury.     

Isolation of neural stem cells from the forebrain of deceased early postnatal and adult rats with protracted post-mortem intervals

Neural stem cells were isolated from deceased early postnatal and adult rats with varying post-mortem intervals. Animals were killed by deep anesthesia and stored in a refrigerator at 4 degrees C for 1-6 days before use. Neurospheres were obtained from the forebrain tissue, including the lateral ventricle in the early postnatal rats, and from the striatal wall of lateral ventricle, including the subventricular zone (SVZ) in adult rats. The number of neurospheres obtained in the primary culture from early postnatal animals was much larger than that from the adult rats. There was no significant difference in the population of neurospheres between the living and the deceased animals at least within 2 days after death. A few neurospheres were still obtainable at 6 days after death in early postnatal animals, but almost no neurospheres were obtained at 5 days after death in the adult rats. The differentiation capacity of neural stem cells in neurospheres was similar between the deceased and the living animals. The rich vascular bed in the SVZ of the lateral ventricle suggests that the vascular architecture might be in part responsible for the survival of the neural stem cells in the deceased animals. Neurosphere cells derived from deceased adult rats survived and differentiated mainly into glial cells in the host spinal cord tissue after transplantation into the injured spinal cord. Therefore, the neural stem cells from deceased animals express the same phenotypes as those from living animals in terms of neurosphere formation, proliferation, and differentiation at least 2 days after death. The neural stem cells from cadavers have great significance in terms of their clinical use as homografts for CNS regeneration.     

Conserved fate and function of ferumoxides‐labeled neural precursor cells in vitro and in vivo

Recent progress in cell therapy research for brain diseases has raised the need for non‐invasive monitoring of transplanted cells. For therapeutic application in multiple sclerosis, transplanted cells need to be tracked both spatially and temporally, in order to assess their migration and survival in the host tissue. Magnetic resonance imaging (MRI) of superparamagnetic iron oxide‐(SPIO)‐labeled cells has been widely used for high resolution monitoring of the biodistribution of cells after transplantation into the central nervous system (CNS). Here we labeled mouse glial‐committed neural precursor cells (NPCs) with the clinically approved SPIO contrast agent ferumoxides and examined their survival and differentiation in vitro, as well as their functional response to environmental signals present within the inflamed brain of experimental autoimmune encephalomyelitis (EAE) mice in vivo. We show that ferumoxides labeling does not affect NPC survival and pluripotency in vitro. Following intracerebroventricular (ICV) transplantation in EAE mice, ferumoxides‐labeled NPCs responded to inflammatory cues in a similar fashion as unlabeled cells. Ferumoxides‐labeled NPCs migrated over comparable distances in white matter tracts and differentiated equally into the glial lineages. Furthermore, ferumoxides‐labeled NPCs inhibited lymph node cell proliferation in vitro, similarly to non‐labeled cells, suggesting a preserved immunomodulatory function. These results demonstrate that ferumoxides‐based MRI cell tracking is well suited for non‐invasive monitoring of NPC transplantation. © 2009 Wiley‐Liss, Inc.     

小鼠胚胎干细胞诱导的神经前体细胞纹状体移植对PD大鼠的治疗作用

目的 观察来源于小鼠胚胎干细胞的神经前体细胞移植PD大鼠纹状体后的存活、分化以及细胞移植对PD大鼠的治疗作用。方法 采用无血清方法将小鼠胚胎干细胞定向诱导为神经前体细胞，免疫组化技术观察移植细胞的存活、分化。结果 胚胎体在N2选择性培养基选择生长5d后，85％以上的小鼠胚胎干细胞分化为nestin阳性的神经前体细胞。移植到PD大鼠纹状体后大部分神经前体细胞存活良好，移植细胞分别保持为未分化的nestin阳性的神经前体细胞和TH阳性的神经元。移植后3周，PD大鼠的旋转次数明显减少。结论 胚胎干细胞来源的神经前体细胞移植PD大鼠纹状体后能分化为TH阳性的神经细胞，对PD有治疗作用。     

昆明种小鼠胚胎神经干细胞的分离与培养

背景: 对于神经干细胞的分离培养,目前多采用胰蛋白酶对组织细胞予以消化,但消化时间较难把握。 目的：采用胰酶消化与机械分离法相结合的方式对昆明种小鼠胚胎脑神经干细胞进行分离、培养,并进行初步的免疫组织化学检测。 设计、时间及地点：细胞学体外观察,于2006-10/2007-09在广西医科大学基础医学实验室完成。 材料：孕14~16 d的昆明种小鼠由广西医科大学实验动物中心提供。 方法：分离昆明种小鼠胎鼠的脑组织,经胰酶消化加机械吹打后,在加入碱性成纤维细胞生长因子和表皮细胞生长因子的B27无血清DMEM/F12培养基中培养。 主要观察指标：用免疫细胞化学方法鉴定分离的神经干细胞。 结果：培养24 h后,细胞以悬浮方式生长,聚集成团;48 h后形成由数十个细胞组成的细胞球,形态规则,体积大小不等,细胞无突起,形成典型的神经球,可传代扩增。免疫细胞化学染色结果示细胞巢蛋白呈阳性表达。 结论：在含有表皮细胞生长因子、碱性成纤维细胞生长因子的无血清B27培养基条件下,有利于小鼠胚胎神经干细胞的体外培养和传代增殖。     

Intraventricular transplantation of neural precursor cell spheres attenuates acute experimental allergic encephalomyelitis

Brain transplantation of neural precursor cells (NPCs) has been proposed to enhance CNS regeneration. As the pathogenesis of most acute CNS diseases involves an inflammatory component, we studied whether NPC transplantation affects brain inflammation. Newborn rat multipotential NPCs were transplanted intraventriculary into acute experimental allergic encephalomyelitis (EAE) rats, a model for disseminated brain inflammation. Cells migrated into inflamed white matter and differentiated into glial cells. NPC transplantation attenuated the clinical severity of EAE and the brain inflammation, indicated by reduction in perivascular infiltrates and decreased expression of ICAM-1 and LFA-1. NPCs inhibited basal proliferation and proliferative responses to Concavalin-A and to MOG peptide of EAE rat-derived lymphocytes in vitro. Purified astrocytes inhibited lymphocyte proliferation in vitro, but did not migrate into EAE brains in vivo, and did not reduce EAE severity or brain inflammation. Thus, transplanted NPCs attenuate acute EAE via an anti-inflammatory mechanism which depends on cell ability to migrate into inflamed brain tissue.     

Stimulation of adult neural stem cells with a novel glycolipid biosurfactant

Glycolipids are amphipathic molecules which are highly expressed on cell membranes in skin and brain where they mediate several key cellular processes. Neural stem cells are defined as undifferentiated, proliferative, multipotential cells with extensive self-renewal and are responsive to brain injury. Di-rhamnolipid: α-l-rhamnopyranosyl-(1-2)α-l-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoic acid, also referred to as di-rhamnolipid BAC-3, is a glycolipid isolated from the bacteria Pseudomonas aeruginosa. In the previous studies, di-rhamnolipid enhanced dermal tissue healing and regeneration. The present study provides the first assessment of di-rhamnolipid, and glycolipid biosurfactants in general, on the nervous system. Treatment of neural stem cells isolated from the lateral ventricle of adult mice and cultured in defined media containing growth factors at 0.5 and 1 μg/ml of di-rhamnolipid increased the number of neurospheres (2.7- and 2.8-fold, respectively) compared to controls and this effect remained even after passaging in the absence of di-rhamnolipid. In addition, neural stem cells treated with di-rhamnolipid at 50 and 100 μg/ml in defined media supplemented with fetal calf serum and without growth factors exhibited increased cell viability, indicating an interaction between di-rhamnolipid and serum components in the regulation of neural stem cells and neuroprogenitors. Intracerebroventricular administration of di-rhamnolipid at 300 and 120 ng/day increased the number of neurospheres (1.3- and 1.63-fold, respectively) that could be derived from the anterior lateral ventricles of adult mice. These results indicate that di-rhamnolipid stimulates proliferation of neural stem cells and increases their endogenous pools which may have therapeutic potential in managing neurodegenerative or neuropsychiatric disorders and promoting nervous tissue regeneration following injury.     

Long‐term fate of grafted hippocampal neural progenitor cells following ischemic injury

The adult CNS has a very limited capacity to regenerate neurons after insult. To overcome this limitation, the transplantation of neural progenitor cells (NPCs) has developed into a key strategy for neuronal replacement. This study assesses the long‐term survival, migration, differentiation, and functional outcome of NPCs transplanted into the ischemic murine brain. Hippocampal neural progenitors were isolated from FVB‐Cg‐Tg(GFPU)5Nagy/J transgenic mice expressing green fluorescent protein (GFP). Syngeneic GFP‐positive NPCs were stereotactically transplanted into the hippocampus of FVB mice following a transient global cerebral ischemia model. Behavioral tests revealed that ischemia/reperfusion induced spatial learning disturbances in the experimental animals. The NPC transplantation promoted cognitive function recovery after ischemic injury. To study the long‐term fate of grafted GFP‐positive NPCs in a host brain, immunohistochemical approaches were applied. Confocal microscopy revealed that grafted cells survived in the recipient tissue for 90 days following transplantation and differentiated into mature neurons with extensive dendritic trees and apparent spines. Immunoelectron microscopy confirmed the formation of synapses between the transplanted GFP‐positive cells and host neurons that may be one of the factors underlying cognitive function recovery. Repair and functional recovery following brain damage represent a major challenge for current clinical and basic research. Our results provide insight into the therapeutic potential of transplanted hippocampal progenitor cells following ischemic brain injury. © 2014 Wiley Periodicals, Inc.     

Long-term expansion of human foetal neural progenitors leads to reduced graft viability in the neonatal rat brain

We previously reported that early passage human foetal neural progenitors (hFNPs) survive long-term in the rodent host brain whereas late passage cells disappear at later post-graft survival times. The extent to which this finding is related to changes in the expanded FNPs or in the adult host brain environment was not determined. Here we report the effect of expanding hFNPs for different periods of time in vitro on their ability to survive transplantation into the neonatal rat hippocampus, a generally more permissive environment than the adult rat brain. After 2 and 8 weeks in vitro, transplanted hFNPs formed large grafts, most of which survived well until at least 12 weeks. However, following continued expansion, hFNPs formed smaller grafts, and cells transplanted after 20 weeks expansion produced no surviving grafts, even at early survival times. To determine whether this could be due to a dilution of "true" neural stem cells through more differentiated progeny over time in culture, we derived homogeneous neural stem (NS) cells grown as a monolayer from the 8 week expanded hFNPs. These cells homogeneously expressed the neural stem cell markers sox-2, 3CB2 and nestin and were expanded for 5 months before transplantation into the neonatal rat brain. However, these cells exhibited a similar survival profile to the long-term expanded FNPs. These results indicate that, while the cellular phenotype of neural stem cells may appear to be stable in vitro using standard markers, expansion profoundly influences the ability of such cells to form viable grafts.     

Connexin43 and connexin47 alterations after neural precursor cells transplantation in experimental autoimmune encephalomyelitis

Exogenous transplanted neural precursor cells (NPCs) exhibit miscellaneous immune‐modulatory effects in models of autoimmune demyelination. However, the regional interactions of NPCs with the host brain tissue in remissive inflammatory events have not been adequately studied. In this study we used the chronic MOG‐induced Experimental Autoimmune Encephalomyelitis (EAE) model in C57BL/six mice. Based on previous data, we focused on neuropathology at Day 50 post‐induction (D50) and studied the expression of connexin43 (Cx43) and Cx47, two of the main glial gap junction (GJ) proteins, in relation to the intraventricular transplantation of GFP⁺NPCs and their integration with the host tissue. By D50, NPCs had migrated intraparenchymally and were found in the corpus callosum at the level of the lateral ventricles and hippocampus. The majority of GFP⁺ cells differentiated with simple or ramified processes expressing mainly markers of mature GLIA (GFAP and NogoA) and significantly less of precursor glial cells. GFP⁺NPCs expressed connexins and formed GJs around the hippocampus more than lateral ventricles. The presence of NPCs did not alter the increase in Cx43 GJ plaques at D50 EAE, but prevented the reduction of oligodendrocytic Cx47, increased the number of oligodendrocytes, local Cx47 levels and Cx47 GJ plaques per cell. These findings suggest that transplanted NPCs may have multiple effects in demyelinating pathology, including differentiation and direct integration into the panglial syncytium, as well as amelioration of oligodendrocyte GJ loss, increasing the supply of potent myelinating cells to the demyelinated tissue. GLIA 2015;63:1772–1783     

Multipotential neural precursors transplanted into the metachromatic leukodystrophy brain fail to generate oligodendrocytes but contribute to limit brain dysfunction

Neural stem cells appear to be best suited for regenerative therapy in neurological diseases. However, the effects of high levels of potentially toxic substances such as sulfatides--which accumulate in metachromatic leukodystrophy (MLD)--on this regenerative ability are still largely unclear. To start addressing this question, in vitro and in vivo experiments were used to examine the behavior of multipotential neural precursors exposed to abnormally high levels of sulfatides. Following transplantation of dissociated neurospheres into the brain of presymptomatic MLD pups, the majority of donor-derived cells were distributed in a caudal to rostral direction, with higher numbers in the cortex. Most if not all of the donor cells acquired an astroglial phenotype. We found no evidence of oligodendrocyte or neuronal commitment of transplanted cells in long-term-treated MLD mice (e.g. up to 1.5 years of age). This was in line with our in vitro findings of sulfatides blocking oligodendrocyte formation after induction of differentiation in sulfatide-treated epidermal growth factor/fibroblast growth factor responsive neurospheres. Transplanted MLD mice showed an improved arylsulfatase A (ARSA) activity and a significant amelioration of sulfatide metabolism, neurodegeneration and motor-learning/memory deficits. Furthermore, transplanted cells were shown to act as a source of ARSA enzyme that accumulated in endogenous brain cells, indicating the occurrence of enzyme cross-correction between transplanted and host cells. These results provide a first insight into the effect of sulfatides on the stemness properties of neural stem cells and on the effects of the MLD environment on the in vivo expectations of using neural stem cells in cell therapy.     

Platelet Microparticles Promote Neural Stem Cell Proliferation, Survival and Differentiation

Platelet microparticles (PMP) are small subcellular fragments, shed upon platelet activation. PMP host a variety of cytokines and growth factor that were previously shown to affect angiogenesis and postischemic tissue regeneration. This study attempted to explore the effect of PMP on neural stem cell (NSC) proliferation, survival and differentiation. Cells were grown as neurospheres and treated with PMP, or relevant growth factors, sphere size and cell fates were evaluated. PMP treatment led to larger neurospheres with increased cell survival. PMP treatment was comparable with the effect of acceptable single growth factors such as fibroblastic growth factor (FGF), vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF). PMP treatment also increased the differentiation potential of NSC to glia and neurons. Specific growth factor inhibitors only partly blocked these effects, which were associated with increments in ERK and Akt phosphorylation. In this study, we show that various growth factors contained within the PMP promote neuronal cell proliferation, survival and differentiation. The results suggest a role for platelet microparticles in augmenting endogenous neural progenitor and stem cells angiogenesis and neurogenesis that might be utilized for treatment following brain injury.