The high integration and differentiation potential of autologous neural stem cell transplantation compared with allogeneic transplantation in adult rat hippocampus

Autologous cell transplantation for treatment of colorectal aganglionosis in mice

Neurointestinal diseases cause significant morbidity and effective treatments are lacking. This study aimes to test the feasibility of transplanting autologous enteric neural stem cells (ENSCs) to rescue the enteric nervous system (ENS) in a model of colonic aganglionosis. ENSCs are isolated from a segment of small intestine from Wnt1::Cre;R26iDTR mice in which focal colonic aganglionosis is simultaneously created by diphtheria toxin injection. Autologous ENSCs are isolated, expanded, labeled with lentiviral-GFP, and transplanted into the aganglionic segment in vivo. ENSCs differentiate into neurons and glia, cluster to form neo-ganglia, and restore colonic contractile activity as shown by electrical field stimulation and optogenetics. Using a non-lethal model of colonic aganglionosis, our results demonstrate the potential of autologous ENSC therapy to improve functional outcomes in neurointestinal disease, laying the groundwork for clinical application of this regenerative cell-based approach.

Isolation, Expansion, and Endoscopic Delivery of Autologous Enteric Neuronal Stem Cells in Swine

The enteric nervous system (ENS) is an extensive network of neurons and glia within the wall of the gastrointestinal (GI) tract that regulates many essential GI functions. Consequently, disorders of the ENS due to developmental defects, inflammation, infection, or age-associated neurodegeneration lead to serious neurointestinal diseases. Despite the prevalence and severity of these diseases, effective treatments are lacking as they fail to directly address the underlying pathology. Neuronal stem cell therapy represents a promising approach to treating diseases of the ENS by replacing the absent or injured neurons, and an autologous source of stem cells would be optimal by obviating the need for immunosuppression. We utilized the swine model to address key questions concerning cell isolation, delivery, engraftment, and fate in a large animal relevant to human therapy. We successfully isolated neural stem cells from a segment of small intestine resected from 1-month-old swine. Enteric neuronal stem cells (ENSCs) were expanded as neurospheres that grew optimally in low-oxygen (5%) culture conditions. Enteric neuronal stem cells were labeled by lentiviral green fluorescent protein (GFP) transduction, then transplanted into the same swine from which they had been harvested. Endoscopic ultrasound was then utilized to deliver the ENSCs (10,000-30,000 neurospheres per animal) into the rectal wall. At 10 and 28 days following injection, autologously derived ENSCs were found to have engrafted within rectal wall, with neuroglial differentiation and no evidence of ectopic spreading. These findings strongly support the feasibility of autologous cell isolation and delivery using a clinically useful and minimally invasive technique, bringing us closer to first-in-human ENSC therapy for neurointestinal diseases.

Schwann Cells in the Aganglionic Colon of Hirschsprung Disease Can Generate Neurons for Regenerative Therapy

Cell therapy offers the potential to replace the missing enteric nervous system (ENS) in patients with Hirschsprung disease (HSCR) and to restore gut function. The Schwann cell (SC) lineage has been shown to generate enteric neurons pre- and post-natally. Here, we aimed to isolate SCs from the aganglionic segment of HSCR and to determine their potential to restore motility in the aganglionic colon. Proteolipid protein 1 (PLP1) expressing SCs were isolated from the extrinsic nerve fibers present in the aganglionic segment of postnatal mice and patients with HSCR. Following 7-10 days of in vitro expansion, HSCR-derived SCs were transplanted into the aganglionic mouse colon ex vivo and in vivo. Successful engraftment and neuronal differentiation were confirmed immunohistochemically and calcium activity of transplanted cells was demonstrated by live cell imaging. Organ bath studies revealed the restoration of motor function in the recipient aganglionic smooth muscle. These results show that SCs isolated from the aganglionic segment of HSCR mouse can generate functional neurons within the aganglionic gut environment and restore the neuromuscular activity of recipient mouse colon. We conclude that HSCR-derived SCs represent a potential autologous source of neural progenitor cells for regenerative therapy in HSCR.

Stem cell membrane, stem cell-derived exosomes and hybrid stem cell camouflaged nanoparticles: A promising biomimetic nanoplatforms for cancer theranostics

Nanomedicine research has advanced dramatically in recent decades. Nonetheless, traditional nanomedicine faces significant obstacles such as the low concentration of the drug at target sites and accelerated removal of the drug from blood circulation. Various techniques of nanotechnology, including cell membrane coating, have been developed to address these challenges and to improve targeted distribution and redcue cell membrane-mediated immunogenicity. Recently, stem cell (SC) membranes, owing to their immunosuppressive and regenerative properties, have grabbed attention as attractive therapeutic carriers for targeting specific tissues or organs. Bioengineering strategies that combine synthetic nanoparticles (NPs) with SC membranes, because of their homing potential and tumor tropism, have recently received a lot of publicity. Several laboratory experiments and clinical trials have indicated that the benefits of SC-based technologies are mostly related to the effects of SC-derived exosomes (SC-Exos). Exosomes are known as nano-sized extracellular vehicles (EVs) that deliver particular bioactive molecules for cell-to-cell communication. In this regard, SC-derived exosome membranes have recently been employed to improve the therapeutic capability of engineered drug delivery vehicles. Most recently, for further enhancing NPs' functionality, a new coating approach has been offered that combines membranes from two separate cells. These hybrid membrane delivery vehicles have paved the way for the development of biocompatible, high-efficiency, biomimetic NPs with varying hybrid capabilities that can overcome the drawbacks of present NP-based treatment techniques. This review explores stem cell membranes, SC-Exos, and hybrid SC-camouflaged NPs preparation methods and their importance in cancer therapy.

Characterization of rat liver bud-derived cells

Cells derived from the fetal liver have been shown to be a rich source of progenitor stem cells, constituting a promising source for Tissue Engineering and Regenerative Medicine. In this study, embryo and fetal liver-bud derived cells from Fischer 344 rats were obtained at E12.5, E14.5 and E16.5 gestational days and evaluated for cell phenotype, survival and proliferation. Liver transaminase (AST and ALT) and AFP levels were lower in embryo liver-bud-derived cells on day 12.5. Markers for stem cells, cell cycle progression and cell death were differentially expressed in E12.5 cell cultures. Analysis of mitochondrial electric potential on 14.5 and 16.5 days showed a tendency for cells with lower functional or metabolic ability, in comparison to cultures derived from day 12.5. The results demonstrated that the majority of the E16.5 cells were in the G0 / G1 phase. The capacity of synthesis (S) and cellular division (G2 / M) of embryo and fetal liver bud-derived cells was constant over all gestational periods. In conclusion, embryo and fetal liver-bud-derived cells during the periods of 12.5 and 14.5 days, showed expression profile of progenitor cells, cell activity and hematopoietic function in culture.

Combination of curcumin with autologous transplantation of adult neural stem/progenitor cells leads to more efficient repair of damaged cerebral tissue of rat

NEW FINDINGS

What is the central question of this study? Can the neuroprotective agent curcumin affect restorative action of neural stem/progenitor cells in the injured rat brain? What is the main finding and its importance? In the presence of curcumin, transplantation of neural stem/progenitor cells in the context of PuraMatrix reduced lesion size and reactive inflammatory responses, and boosted survival rate of grafted neurons. In addition it improved the neurological status of injured animals. This could be beneficial in designing new therapeutic approaches for brain injury based on this combination therapy.

ABSTRACT

Traumatic brain injury (TBI) is catastrophic neurological damage associated with substantial morbidity and mortality. To date, there is no specific treatment for restoring lost brain tissue. In light of the complex pathology of brain injury, the present study evaluated the effects of combination therapy using autologous neural stem/progenitor cells (NS/PCs), PuraMatrix (PM) and curcumin in an animal model of brain injury. After stereotactic biopsy of subventricular zone tissue and culture of NS/PCs, 36 male Wistar rats (150-200 g) were randomly divided into six groups receiving dimethyl sulfoxide (DMSO),  curcumin (100 mg kg^-1 in DMSO), PM + curcumin (100 mg kg^-1 in DMSO), NS/PCs + curcumin (100 mg kg^-1 in DMSO), NS/PCs + PM + curcumin (100 mg kg^-1 in DMSO) and NS/PCs + PM + curcumin (1 µm) following acute brain injury. The animals were evaluated in term of neurological status for 4 weeks, then decapitated. Nissl and TUNEL staining and immunohistochemistry for bromodeoxyuridine, glial fibrillary acidic protein, doublecortin, Map2, Olig2, Iba1 and CD68 were performed. We found that combination therapy by NS/PCs + PM + curcumin reduced the lesion size, astrogliosis, macrophage and microglial reaction as well as the number of apoptotic cells. Moreover, the transplanted cells were able to survive and differentiate after 4 weeks. Besides these findings, transplantation of NS/PCs in the context of PM and curcumin improved the neurological status of injured animals. In conclusion, our data suggest that this combination therapy can be beneficial in developing future therapeutic approaches for brain injury.

Engineered stem cells targeting multiple cell surface receptors in tumors

Multiple stem cell types exhibit inherent tropism for cancer, and engineered stem cells have been used as therapeutic agents to specifically target cancer cells. Recently, stem cells have been engineered to target multiple surface receptors on tumor cells, as well as endothelial and immune cells in the tumor microenvironment. In this review, we discuss the rationales and strategies for developing multiple receptor-targeted stem cells, their mechanisms of action, and the promises and challenges they hold as cancer therapeutics.

Intra-cavity stem cell therapy inhibits tumor progression in a novel murine model of medulloblastoma surgical resection

Background

Cytotoxic neural stem cells (NSCs) have emerged as a promising treatment for Medulloblastoma (MB), the most common malignant primary pediatric brain tumor. The lack of accurate pre-clinical models incorporating surgical resection and tumor recurrence limits advancement in post-surgical MB treatments. Using cell lines from two of the 5 distinct MB molecular sub-groups, in this study, we developed an image-guided mouse model of MB surgical resection and investigate intra-cavity NSC therapy for post-operative MB.

Methods

Using D283 and Daoy human MB cells engineered to express multi-modality optical reporters, we created the first image-guided resection model of orthotopic MB. Brain-derived NSCs and novel induced NSCs (iNSCs) generated from pediatric skin were engineered to express the pro-drug/enzyme therapy thymidine kinase/ganciclovir, seeded into the post-operative cavity, and used to investigate intra-cavity therapy for post-surgical MB.

Results

We found that surgery reduced MB volumes by 92%, and the rate of post-operative MB regrowth increased 3-fold compared to pre-resection growth. Real-time imaging showed NSCs rapidly homed to MB, migrating 1.6-fold faster and 2-fold farther in the presence of tumors, and co-localized with MB present in the contra-lateral hemisphere. Seeding of cytotoxic NSCs into the post-operative surgical cavity decreased MB volumes 15-fold and extended median survival 133%. As an initial step towards novel autologous therapy in human MB patients, we found skin-derived iNSCs homed to MB cells, while intra-cavity iNSC therapy suppressed post-surgical tumor growth and prolonged survival of MB-bearing mice by 123%.

Conclusions

We report a novel image-guided model of MB resection/recurrence and provide new evidence of cytotoxic NSCs/iNSCs delivered into the surgical cavity effectively target residual MB foci.

Stem Cells Engineered During Different Stages of Reprogramming Reveal Varying Therapeutic Efficacies

Stem cells are emerging as promising treatment strategies for several brain disorders and pathologies. In this study, we explored the potential of creating induced pluripotent stem cell-derived neural stem cells (ipNSC) by using either unmodified or gene-modified somatic cells and tested their fate and therapeutic efficacies in vitro and in vivo. We show that cells engineered in somatic state lose transgene-expression during the neural induction process, which is partially restored by histone deacetylase inhibitor treatment whereas cells engineered at the ipNSC state have sustained expression of transgenes. In vivo, bimodal mouse and human ipNSCs engineered to express tumor specific death-receptor ligand and suicide-inducing therapeutic proteins have profound anti-tumor efficacy when encapsulated in synthetic extracellular matrix and transplanted in mouse models of resected-glioblastoma. This study provides insights into using somatic cells for treating CNS disorders and presents a receptor-targeted cancer therapeutic approach for brain tumors. Stem Cells 2018;36:932-942.

A Novel Biopsy Method for Isolating Neural Stem Cells from the Subventricular Zone of the Adult Rat Brain for Autologous Transplantation in CNS Injuries

Despite all attempts the problem of regeneration in damaged central nervous system (CNS) has remained challenging due to its cellular complexity and highly organized and sophisticated connections. In this regard, stem cell therapy might serve as a viable therapeutic approach aiming either to support the damaged tissue and hence to reduce the subsequent neurological dysfunctions and impairments or to replace the lost cells and re-establish damaged circuitries. Adult neural stem/progenitor cells (NS/PCs) are one of the outstanding cell sources that can be isolated from the subventricular zone (SVZ) of the lateral ventricles. These cells can differentiate into neurons, astrocytes, and oligodendrocytes. Implanting autologous NS/PCs will greatly benefit the patients by avoiding immune rejection after implantation, better survival, and integration with the host tissue. Developing safe and efficient methods in small animal models will provide us with the opportunity to optimize procedures required to achieve successful human autologous NS/PC transplantation in near future. In this chapter, a highly controlled and safe biopsy method for harvesting stem cell containing tissue from the SVZ of adult rat brain is introduced. Then, isolation and expansion of NS/PCs from harvested specimen as well as the techniques to verify proliferation and differentiation capacity of the resulting NS/PCs are discussed. Finally, a method for assessing the biopsy lesion volume in the brain is described. This safe biopsy method in rat provides a unique tool to study autologous NS/PC transplantation in different CNS injury models.

A new method for evaluating regional cerebral blood flow changes: Laser speckle contrast imaging in a C57BL/6J mouse model of photothrombotic ischemia

The present study aimed to improve the processing of data acquired from laser speckle contrast imaging (LSCI) to provide a standardization method to explore changes in regional cerebral blood flow (rCBF) and to determine the correlations among rCBF, cerebral ischemic lesion volume and microvascular density over time in a focal ischemic region. C57BL/6J mice were subjected to focal photothrombotic (PT) ischemia. rCBF was measured using LSCI at different time points before and after PT ischemia through an intact skull. Standardized rCBF (SrCBF), defined as the ratio of rCBF measured in the ipsilateral region of interest (ROI) to that in the corresponding contralateral region, was calculated to evaluate potential changes. In addition, the volume of the ischemic lesion and the microvascular density were determined using Nissl staining and immunofluorescence, respectively. The relationships among the ischemic lesion volume, microvascular density and SrCBF were analyzed over time. The results showed that the cortical rCBF measured using LSCI following PT ischemia in the C57BL/6J mice gradually increased. Changes in the cerebral ischemic lesion volume were negatively correlated with SrCBF in the ischemic region. Changes in the microvascular density were similar to those observed in SrCBF. Our findings indicate that LSCI is a practical technique for observing changes in murine cortical rCBF without skull opening and for analyzing the relationships among the ischemic lesion volume, microvascular density and SrCBF following focal cerebral ischemia. Preliminary results also suggest that the use of LSCI to observe the formation of collateral circulation is feasible.

Electrical Stimulation Elicits Neural Stem Cells Activation: New Perspectives in CNS Repair

Researchers are enthusiastically concerned about neural stem cell (NSC) therapy in a wide array of diseases, including stroke, neurodegenerative disease, spinal cord injury, and depression. Although enormous evidences have demonstrated that neurobehavioral improvement may benefit from NSC-supporting regeneration in animal models, approaches to endogenous and transplanted NSCs are blocked by hurdles of migration, proliferation, maturation, and integration of NSCs. Electrical stimulation (ES) may be a selective non-drug approach for mobilizing NSCs in the central nervous system. This technique is suitable for clinical application, because it is well established and its potential complications are manageable. Here, we provide a comprehensive review of the emerging positive role of different electrical cues in regulating NSC biology in vitro and in vivo, as well as biomaterial-based and chemical stimulation of NSCs. In the future, ES combined with stem cell therapy or other cues probably becomes an approach for promoting brain repair.

Stem cell-based therapies for cancer treatment: separating hope from hype

Stem cell-based therapies are emerging as a promising strategy to tackle cancer. Multiple stem cell types have been shown to exhibit inherent tropism towards tumours. Moreover, when engineered to express therapeutic agents, these pathotropic delivery vehicles can effectively target sites of malignancy. This perspective considers the current status of stem cell-based treatments for cancer and provides a rationale for translating the most promising preclinical studies into the clinic.

The glial response to intracerebrally delivered therapies for neurodegenerative disorders: is this a critical issue?

The role of glial cells in the pathogenesis of many neurodegenerative conditions of the central nervous system (CNS) is now well established (as is discussed in other reviews in this special issue of Frontiers in Neuropharmacology). What is less clear is whether there are changes in these same cells in terms of their behavior and function in response to invasive experimental therapeutic interventions for these diseases. This has, and will continue to become more of an issue as we enter a new era of novel treatments which require the agent to be directly placed/infused into the CNS such as deep brain stimulation (DBS), cell transplants, gene therapies and growth factor infusions. To date, all of these treatments have produced variable outcomes and the reasons for this have been widely debated but the host astrocytic and/or microglial response induced by such invasively delivered agents has not been discussed in any detail. In this review, we have attempted to summarize the limited published data on this, in particular we discuss the small number of human post-mortem studies reported in this field. By so doing, we hope to provide a better description and understanding of the extent and nature of both the astrocytic and microglial response, which in turn could lead to modifications in the way these therapeutic interventions are delivered.

A new and safe method for stereotactically harvesting neural stem/progenitor cells from the adult rat subventricular zone

BACKGROUND

Adult neural stem/progenitor cells (NS/PCs) are one of the outstanding cell sources for therapeutic purposes in the central nervous system diseases. Autologous transplantation of NS/PCs still is a matter of controversy due to the safety issue as well as efficiency of harvesting these cells from the live mammalian brain subventricular zone (SVZ).

NEW METHOD

In this new and safe method, a 16-guage semi-automatic biopsy needle was used stereotactically to remove a piece of SVZ. Then, the proliferation and differentiation capacity of obtained cells were assessed. In addition, the safety of the biopsy procedure was analyzed employing the Morris water maze, modified neurologic severity score, passive avoidance and open field tests.

RESULTS

Despite being very small in size, the SVZ specimen could generate a large number of progeny with the ability to differentiate into neuronal and glial cells. The biopsy procedure introduced in this study did not have any impact on the behavioral and neurological processes.

COMPARISON WITH EXISTING METHOD(S)

existing SVZ biopsy methods were uncontrollable techniques which harvested brain tissue by aspiration using a syringe not a semi-automatic biopsy needle. Also, previous methods were not evaluated in terms of behavior and cognition.

CONCLUSIONS

This study revealed a considerable safety and efficacy for the stereotactical removal of the adult rat SVZ to harvest NS/PCs for autologous transplantation.

Current challenges for the advancement of neural stem cell biology and transplantation research

Transplantation of neural stem cells (NSC) is hoped to become a promising primary or secondary therapy for the treatment of various neurodegenerative disorders of the central nervous system (CNS), as demonstrated by multiple pre-clinical animal studies in which functional recovery has already been demonstrated. However, for NSC therapy to be successful, the first challenge will be to define a transplantable cell population. In the first part of this review, we will briefly discuss the main features of ex vivo culture and characterisation of NSC. Next, NSC grafting itself may not only result in the regeneration of lost tissue, but more importantly has the potential to improve functional outcome through many bystander mechanisms. In the second part of this review, we will briefly discuss several pre-clinical studies that contributed to a better understanding of the therapeutic potential of NSC grafts in vivo. However, while many pre-clinical animal studies mainly report on the clinical benefit of NSC grafting, little is known about the actual in vivo fate of grafted NSC. Therefore, the third part of this review will focus on non-invasive imaging techniques for monitoring cellular grafts in the brain under in vivo conditions. Finally, as NSC transplantation research has evolved during the past decade, it has become clear that the host micro-environment itself, either in healthy or injured condition, is an important player in defining success of NSC grafting. The final part of this review will focus on the host environmental influence on survival, migration and differentiation of grafted NSC.

Wip1-dependent signaling pathways in health and diseases

Spatial and temporal regulation of protein phosphorylation is key to the control of different molecular networks. This regulation is achieved in part through dephosphorylation of numerous signaling molecules, and emerging evidence highlights the importance of a new member of the PP2C family of phosphatase, Wild-type p53 induced phosphatase 1 (Wip1), in regulating stress-induced and DNA damage-induced networks. In recent years, analysis of Wip1 has focused primarily on its role in tumorigenesis because of its overexpression in human tumors and a profound tumor-resistant phenotype of Wip1-deficient mice. Recently, Wip1 has also been shown to play an important role in several physiological processes including adult neurogenesis and organismal aging. This review addresses how Wip1 phosphatase regulates different signaling networks in a spatial and temporal manner and how these differences contribute to various biological outcomes in the context of physiological and pathological conditions.

Proton MR spectroscopy of neural stem cells: does the proton-NMR peak at 1.28 ppm function as a biomarker for cell type or state?

Recently, a peak at 1.28 ppm in proton magnetic resonance spectroscopy ((1)H-MRS) of neural stem cells (NSCs) was introduced as a noninterventional biomarker for neurogenesis in vivo. This would be an urgently needed requisite for translational studies in humans regarding the beneficial role of adult neurogenesis for the structural and functional integrity of the brain. However, many concerns have risen about the validity of the proposed signal as a specific marker for NSCs. The peak has also been related to cell-type-independent phenomena such as apoptosis or necrosis. Thus, we compared the 1.28-ppm peak in various immature stem cell populations, including embryonic stem cells, mouse embryonic fibroblasts, embryonic stem cell- and induced pluripotent stem cell-derived NSCs, ex vivo isolated embryonic NSCs, as well as mature and tumor cell types from different germ layers. To correlate the integral peak intensity with cell death, we induced both apoptosis with camptothecin and necrosis with sodium azide. A peak at 1.28 ppm was found in most cell types, and in most, but not all, NSCH cultures, demonstrating no specificity for NSCs. The intensities of the 1.28-ppm resonance significantly correlated with the rate of apoptosis, but not with the rate of necrosis, cell cycle phase distribution, cell size, or type. Multiple regression analysis displayed a significant predictive value of the peak intensity for apoptosis only. In this context, its specificity for apoptosis as a major selection process during neurogenesis may suggest this resonance as an indirect marker for neurogenesis in vivo.

Striatal stimulation nurtures endogenous neurogenesis and angiogenesis in chronic-phase ischemic stroke rats

Deep brain stimulation (DBS) is used to treat a variety of neurological disorders including Parkinson's disease. In this study, we explored the effects of striatal stimulation (SS) in a rat model of chronic-phase ischemic stroke. The stimulation electrode was implanted into the ischemic penumbra at 1 month after middle cerebral artery occlusion (MCAO) and thereafter continuously delivered SS over a period of 1 week. Rats were evaluated behaviorally coupled with neuroradiological assessment of the infarct volumes using magnetic resonance imaging (MRI) at pre- and post-SS. The rats with SS showed significant behavioral recovery in the spontaneous activity and limb placement test compared to those without SS. MRI visualized that SS also significantly reduced the infarct volumes compared to that at pre-SS or without SS. Immunohistochemical analyses revealed a robust neurogenic response in rats that received SS characterized by a stream of proliferating cells from the subventricular zone migrating to and subsequently differentiating into neurons in the ischemic penumbra, which exhibited a significant GDNF upregulation. In tandem with this SS-mediated neurogenesis, enhanced angiogenesis was also recognized as revealed by a significant increase in VEGF levels in the penumbra. These results provide evidence that SS affords neurorestoration at the chronic phase of stroke by stimulating endogenous neurogenesis and angiogenesis.

Long-term fate of allogeneic neural stem cells following transplantation into injured spinal cord

To characterize the fate of allogeneic neural stem cells (NSCs) following transplantation into injured spinal cord, green fluorescent protein (GFP)-NSCs isolated from GFP transgenic Sprague-Dawley rat embryos were transplanted into contused spinal cords of Wistar rats. The GFP-NSCs survived for at least 6 months in injured spinal cord; most of them differentiated rapidly into astrocytes, and a few were able to undergo proliferation. After transplantation, the GFP-NSCs remained in the transplantation site at the early stage, and then migrated along white-matter, and gathered around the injured cavity. At 6 months post-transplantation, CD8 T-lymphocytes infiltrated the spinal cord, and mixed lymphocyte culture from host and donor showed that lymphocytes from the host spleen were primed by allogeneic GFP-NSCs. At 12 months post-transplantation, most GFP cells in the spinal cord lost their morphology and disintegrated. The Basso, Beattie and Bresnahan score and footprint analysis indicated that the improvement of locomotor function in transplanted rats appeared only at the early stage, and was not seen even at 6 months after transplantation All these results suggest that the allogeneic NSCs, after transplantation into injured spinal cord, activate the host immune system. Therefore, if immunosuppressive agents are not used, the grafted allogeneic NSCs, although they can survive for a long time, are subjected to host immune rejection, and the effect of NSCs on functional recovery is limited.

Immune influence on adult neural stem cell regulation and function

Neural stem cells (NSCs) lie at the heart of central nervous system development and repair, and deficiency or dysregulation of NSCs or their progeny can have significant consequences at any stage of life. Immune signaling is emerging as one of the influential variables that define resident NSC behavior. Perturbations in local immune signaling accompany virtually every injury or disease state, and signaling cascades that mediate immune activation, resolution, or chronic persistence influence resident stem and progenitor cells. Some aspects of immune signaling are beneficial, promoting intrinsic plasticity and cell replacement, while others appear to inhibit the very type of regenerative response that might restore or replace neural networks lost in injury or disease. Here we review known and speculative roles that immune signaling plays in the postnatal and adult brain, focusing on how environments encountered in disease or injury may influence the activity and fate of endogenous or transplanted NSCs.

Electrical stimulation of the cerebral cortex exerts antiapoptotic, angiogenic, and anti-inflammatory effects in ischemic stroke rats through phosphoinositide 3-kinase/Akt signaling pathway

BACKGROUND AND PURPOSE

Neuroprotective effects of electric stimulation have been recently shown in ischemic stroke, but the underlying mechanisms remain poorly understood.

METHODS

Adult Wistar rats weighing 200 to 250 g received occlusion of the right middle cerebral artery for 90 minutes. At 1 hour after reperfusion, electrodes were implanted to rats on the right frontal epidural space. Electric stimulation, at preset current (0 to 200 microA) and frequency (0 to 50 Hz), was performed for 1 week. Stroke animals were subjected to behavioral tests at 3 days and 1 week postmiddle cerebral artery and then immediately euthanized for protein and immunohistochemical assays. After demonstration of behavioral and histological benefits, subsequent experiments pursued the mechanistic hypothesis that electric stimulation exerted antiapoptotic effects through the phosphoinositide 3-kinase-dependent pathway; thus, cortical stimulation was performed in the presence or absence of specific inhibitors of phosphoinositide 3-kinase (LY294002) in stroke rats.

RESULTS

Cortical stimulation abrogated the ischemia-associated increase in apoptotic cells in the injured cortex by activating antiapoptotic cascades, which was reversed by the phosphoinositide 3-kinase inhibitor LY294002 as reflected behaviorally and immunohistochemically. Furthermore, brain levels of neurotrophic factors (glial cell line-derived neurotrophic factor, brain-derived neurotrophic factor, vascular endothelial growth factor) were upregulated, which coincided with enhanced angiogenesis and suppressed proliferation of inflammatory cells in the ischemic cortex.

CONCLUSIONS

These results suggest that electric stimulation prevents apoptosis through the phosphoinositide 3-kinase pathway. Consequently, the ischemic brain might have been rendered as a nurturing microenvironment characterized by robust angiogenesis and diminished microglial/astrocytic proliferation, resulting in the reduction of infarct volumes and behavioral recovery. Electric stimulation is a novel and potent therapeutic tool for cerebral ischemia.

Unconditioned adult-derived neurosphere cells mainly differentiate towards astrocytes upon transplantation in sclerotic rat hippocampus

PURPOSE

Cell transplantation is being investigated as an alternative treatment for medically refractory temporal lobe epilepsy (TLE). In this study the fate of adult-derived neurosphere cells was evaluated after transplantation in the lesioned hippocampus of the intrahippocampal kainic acid (KA) model for TLE.

METHODS

Neurosphere-forming cells were derived from the subventricular zone (SVZ) of transgenic green fluorescent protein (GFP) reporter mice and expanded in culture. After 10 passages in vitro neurosphere-derived cells were transplanted in the hippocampus three days (KA3d group) and three weeks (KA3w group) after intrahippocampal KA injection. Survival and differentiation of neurosphere cells were evaluated three and six weeks after transplantation.

RESULTS

A fraction (about 1%) of GFP-expressing neurosphere cells survived for at least six weeks after transplantation with a higher and more robust survival rate in the KA3d compared to the KA3w group. Although a small fraction of the cells expressed the neuronal marker NeuN, neurosphere cells mainly differentiated towards astrocytes.

DISCUSSION

Our results indicate that adult-derived neurosphere cells are able to survive upon transplantation in the sclerotic hippocampus. The transplanted cells do not or hardly contribute to neuronal replacement and mainly adopt an astrogliotic fate.

The combined therapy of intrahippocampal transplantation of adult neural stem cells and intraventricular erythropoietin-infusion ameliorates spontaneous recurrent seizures by suppression of abnormal mossy fiber sprouting

Adult neural stem cells (NSCs) possess the potentials to self-renew and exert neuroprotection. In this study, we examined whether adult NSCs had anti-epileptic effects in rats with status epilepticus (SE) induced by kainic acid (KA) and whether co-administration of erythropoietin (EPO) enhanced anti-epileptic effects or cell survival. Adult NSCs were transplanted into KA-lesioned hippocampus with or without intracerebroventricular EPO infusion. Electronic encephalography (EEG) was recorded for 3 weeks after transplantation. The frequency of abnormal spikes in rats with NSC transplantation decreased significantly compared to those of rats without NSC transplantation. Most of the transplanted NSCs differentiated into GFAP-positive astrocytes. EPO infusion significantly enhanced the survival of NSCs, but not neuronal differentiation or migration. NSC transplantation increased the number of neuropeptide Y (NPY) and glutamic acid decarboxylase 67 (GAD67)-positive interneurons. NSC transplantation also suppressed mossy fiber sprouting into the inner molecular layer with subsequent reduction of hippocampal excitability, which finally prevented the development of spontaneous recurrent seizures in adult rats after KA-induced SE. This study might shed light on the cytoarchitectural mechanisms of temporal lobe epilepsy as well as clarify the effect of adult NSC transplantation with intracerebroventricular EPO infusion for temporal lobe epilepsy.

Cdk5 regulates accurate maturation of newborn granule cells in the adult hippocampus

Newborn granule cells become functionally integrated into the synaptic circuitry of the adult dentate gyrus after a morphological and electrophysiological maturation process. The molecular mechanisms by which immature neurons and the neurites extending from them find their appropriate position and target area remain largely unknown. Here we show that single-cell-specific knockdown of cyclin-dependent kinase 5 (cdk5) activity in newborn cells using a retrovirus-based strategy leads to aberrant growth of dendritic processes, which is associated with an altered migration pattern of newborn cells. Even though spine formation and maturation are reduced in cdk5-deficient cells, aberrant dendrites form ectopic synapses onto hilar neurons. These observations identify cdk5 to be critically involved in the maturation and dendrite extension of newborn neurons in the course of adult neurogenesis. The data presented here also suggest a mechanistic dissociation between accurate dendritic targeting and subsequent synapse formation.

Neuronal differentiation potential of human adipose-derived mesenchymal stem cells

Adult mesenchymal stem cells derived from adipose tissue (A-MSC) have the capacity to differentiate in vitro into mesenchymal as well as endodermal and ectodermal cell lineages. We investigated the neuronal differentiation potential of human A-MSC with a protocol which included sphere formation and sequential culture in brain-derived neurotrophic factor (BDNF) and retinoic acid (RA). After 30 days, about 57% A-MSC showed morphological, immunocytochemical and electrophysiological evidence of initial neuronal differentiation. In fact, A-MSC displayed elongated shape with protrusion of two or three cellular processes, selectively expressed nestin and neuronal molecules (including GABA receptor and tyroxine hydroxilase) in the absence of glial phenotypic markers. Differentiated cells showed negative membrane potential (-60 mV), delayed rectifier potassium currents and TTX-sensitive sodium currents. Such changes were stable for at least 7 days after removal of differentiation medium. In view of these results and the easy availability of adipose tissue, A-MSC may be a ready source of adult MSC with neuronal differentiation potential, an useful tool to treat neurodegenerative diseases.

Potential of adult neural stem cells in stroke therapy

Despite state-of-the-art therapy, clinical outcome after stroke remains poor, with many patients left permanently disabled and dependent on care. Stem cell therapy has evolved as a promising new therapeutic avenue for the treatment of stroke in experimental studies, and recent clinical trials have proven its feasibility and safety in patients. Replacement of damaged cells and restoration of function can be accomplished by transplantation of different cell types, such as embryonic, fetal or adult stem cells, human fetal tissue and genetically engineered cell lines. Adult neural stem cells offer the advantage of avoiding the ethical problems associated with embryonic or fetal stem cells and can be harvested as autologous grafts from the individual patients. Furthermore, stimulation of endogenous adult stem cell-mediated repair mechanisms in the brain might offer new avenues for stroke therapy without the necessity of transplantation. However, important scientific issues need to be addressed to advance our understanding of the molecular mechanisms underlying the critical steps in cell-based repair to allow the introduction of these experimental techniques into clinical practice. This review describes up-to-date experimental concepts using adult neural stem cells for the treatment of stroke.

Embryonic stem cell-derived neural precursor cells improve memory dysfunction in Abeta(1-40) injured rats

The versatility of neural precursor cells (NPCs) derived from mouse embryonic stem cells (ESCs) has recently rekindled interests in cell replacement strategies aimed at neurodegenerative diseases. We observed the survival, migration, differentiation and functional recovery of NPCs transplanted into the hippocampus of aggregated beta-amyloid (Abeta) peptide injured rats. Congo Red plaques, Fluro-jade B positive degenerating neurons and neuronal loss were observed in the Abeta-injured hippocampus of rats, accompanied with significant increases in escape latency and decrease in the ratio of exploratory time in a Morris water maze test. EGFP-expressing mouse ES cells were induced into Nestin-positive NPCs before transplantation into the Abeta-injured hippocampus. A marked decrease in escape latency and exploratory time were observed at least 16 weeks after transplantation compared to Abeta-injured animals without grafts. Grafted EGFP-expressing NPCs spread away from the injection tract and about 12.01+/-0.67% and 9.41+/-0.78% of NPCs differentiated into, respectively, GFAP- and NF200-positive cells 4 W after transplantation. These ratios gradually increased to 40.25+/-0.57% and 19.35+/-0.84% by 16 W. The restoration of hippocampal function by ESCs suggests that cell transplantation may be the effective choice to improve the cognitive function caused by Abeta injured.

Targeted migration and differentiation of engrafted neural precursor cells in amyloid beta-treated hippocampus in rats

OBJECTIVE

To observe the migration and differentiation of the neural precursor cells (NPCs) that derived from murine embryonic stem cells (ESCs) when they were transplanted into amyloid beta (A beta)-treated rat hippocampus.

METHODS

MESPU35, a murine ESC cell line that express the enhanced green fluorescent protein (EGFP), was induced differentiation into nestin-positive NPCs by modified serum-free methods. The A beta plaques and the differentiation of the grafted cells were observed by immunofluorescent staining.

RESULTS

Comparing 16 weeks with 4 weeks post-transplantation, the migration distance increased about 5 times; the rate of migratory NPCs differentiating into glial fibrillary acidic protein (GFAP)-positive cells kept rising from (30.41+/-1.45) % to (49.25+/-1.23) %, and the rate of NPCs differentiating into neurofilament 200 (NF200) positive cells increased from (16.68+/-0.95) % to (27.94+/-1.21) %. Meanwhile, the GFAP-positive cells targeting to the ipsilateral side of A beta plaques increased from 60.2% to 81.3%, while the NF200-positive cells increased from 61.3% to 84.1%. The migration distance had significant positive linear correlations to the neuronal differentiation rate (r = 0.991) and to the astrocytic differentiation rate (r = 0.953).

CONCLUSION

Engrafted NPCs migrate targetedly to the A beta injection site and differentiate into neurons and astrocytes.

Comparison of the therapeutic potential of adult and embryonic neural precursor cells in a rat model of Parkinson disease

Object

The therapeutic effects of adult and embryonic neural precursor cells (NPCs) were evaluated and their therapeutic potential compared in a rat model of Parkinson disease.

Methods

Adult NPCs were obtained from the subventricular zone and embryonic NPCs were taken from the ganglionic eminence of 14-day-old embryos. Each NPC type was cultured with epidermal growth factor. The in vitro neuronal differentiation rate of adult NPCs was approximately equivalent to that of embryonic NPCs after two passages. Next, the NPCs were transfected with either green fluorescent protein or glial cell line–derived neurotrophic factor (GDNF) by adenoviral infection and transplanted into the striata in a rat model of Parkinson disease (PD) induced by unilateral intrastriatal injection of 6-hydroxydopamine. An amphetamine-induced rotation test was used to evaluate rat behavioral improvement, and immunohistochemical analysis was performed to compare grafted cell survival, differentiation, and host tissue changes.

Results

The rats with GDNF-transfected NPCs had significantly fewer amphetamine-induced rotations and less histological damage. Except for the proportion of surviving grafted cells, there were no significant differences between adult and embryonic NPCs.

Conclusions

Adult and embryonic NPCs have a comparable therapeutic potential in a rat model of PD.

Adult neural stem and progenitor cells modified to secrete GDNF can protect, migrate and integrate after intracerebral transplantation in rats with transient forebrain ischemia

Adult neural stem and progenitor cells (NSPCs) are important autologous transplantation tools in regenerative medicine, as they can secrete factors that protect the ischemic brain. We investigated whether adult NSPCs genetically modified to secrete more glial cell line-derived neurotrophic factor (GDNF) could protect against transient ischemia in rats. NSPCs were harvested from the subventricular zone of adult Wistar rats and cultured for 3 weeks in the presence of epidermal growth factor. The NSPCs were treated with fibre-mutant Arg-Gly-Asp adenovirus containing the GDNF gene (NSPC-GDNF) or enhanced green fluorescent protein (EGFP) gene (NSPC-EGFP; control group). In one experiment, cultured cells were transplanted into the right ischemic boundary zone of Wistar rat brains. One week later, animals underwent 90 min of intraluminal right middle cerebral artery occlusion followed by magnetic resonance imaging and behavioural tests. The NSPC-GDNF group had higher behavioural scores and lesser infarct volume than did controls at 1, 7 and 28 days postocclusion. In the second experiment, we transplanted NSPCs 3 h after ischemic insult. Compared to controls, rats receiving NSPC-GDNF had decreased infarct volume and better behavioural assessments at 7 days post-transplant. Animals were killed on day 7 and brains were collected for GDNF ELISA and morphological assessment. Compared to controls, more GDNF was secreted, more NSPC-GDNF cells migrated toward the ischemic core and more NSPC-GDNF cells expressed immature neuronal marker. Moreover, the NSPC-GDNF group showed more effective inhibition of microglial invasion and apoptosis. These findings suggest that NSPC-GDNF may be useful in treatment of cerebral ischemia.

Embryonic stem cells and retinal repair

In this review we examine the potential of embryonic stem cells (ESCs) for use in the treatment of retinal diseases involving photoreceptors and retinal pigment epithelium (RPE). We outline the ontogenesis of target retinal cell types (RPE, rods and cones) and discuss how an understanding of developmental processes can inform our manipulation of ESCs in vitro. Due to their potential for cellular therapy, special emphasis is placed upon the derivation and culture of human embryonic stem cells (HESCs) and their differentiation towards a retinal phenotype. In terms of achieving this goal, we suggest that much of the success to date reflects permissive in vitro environments provided by established protocols for HESC derivation, propagation and neural differentiation. In addition, we summarise key factors that may be important for enhancing efficiency of retinal cell-type derivation from HESCs. The retina is an amenable component of the central nervous system (CNS) and as such, diseases of this structure provide a realistic target for the application of HESC-derived cellular therapy to the CNS. In order to further this goal, the second component of our review focuses on the cellular and molecular cues within retinal environments that may influence the survival and behaviour of transplanted cells. Our analysis considers both the potential barriers to transplant integration in the retina itself together with the remodelling in host visual centres that is known to accompany retinal dystrophy.

Prospects for neural stem cell-based therapies for neurological diseases

Neural stem and progenitor cells have great potential for the treatment of neurological disorders. However, many obstacles remain to translate this field to the patient's bedside, including rationales for using neural stem cells in individual neurological disorders; the challenges of neural stem cell biology; and the caveats of current strategies of isolation and culturing neural precursors. Addressing these challenges is critical for the translation of neural stem cell biology to the clinic. Recent work using neural stem cells has yielded novel biologic concepts such as the importance of the reciprocal interaction between neural stem cells and the neurodegenerative environment. The prospect of using transplants of neural stem cells and progenitors to treat neurological diseases requires a better understanding of the molecular mechanisms of both neural stem cell behavior in experimental models and the intrinsic repair capacity of the injured brain.

Survival of transplanted neural progenitor cells enhanced by brain irradiation

OBJECT

Authors of previous studies have reported that adult transplanted neural progenitor cells (NPCs) are suitable for brain cell replacement or gene delivery. In this study, the authors evaluated survival and integration of adult rat-derived NPCs after transplantation and explored the potential impact on transplant survival of various mechanical and biological factors of clinical importance.

METHODS

Adult female Fischer 344 rats were used both as a source and recipient of transplanted NPCs. Both 9L and RG2 rat glioma cells were used to generate in vivo brain tumor models. On the 5th day after tumor implantation, NPCs expressing green fluorescent protein (GFP) were administered either intravenously (3.5 x 10(7) cells) or by stereotactic injection (1 x 10(4)-1 x 10(6) cells) into normal or tumor-bearing brain. The authors evaluated the effect of delivery method (sharp compared with blunt needles, normal compared with zero-volume needles, phosphate-buffered saline compared with medium as vehicle), delivery sites (intravenous compared with intratumoral compared with intraparenchymal), and pretreatment with an immunosuppressive agent (cyclosporin) or brain irradiation (20-40 Gy) on survival and integration of transplanted NPCs.

RESULTS

Very few cells survived when less than 10(5) cells were transplanted. When 10(5) cells or more were transplanted, only previously administered brain irradiation significantly affected survival and integration of NPCs. Although GFP-containing NPCs could be readily detected 1 day after injection, few cells survived 4 days to 1 week unless preceded by whole-brain radiation (20 or 40 Gy in a single fraction), which increased the number of GFP-containing NPCs within the tissue more than fivefold.

CONCLUSIONS

The authors' findings indicate that most NPCs, including those from a syngeneic autologous source, do not survive at the site of implantation, but that brain irradiation can facilitate subsequent survival in both normal and tumor-bearing brain. An understanding of the mechanisms of this effect could lead to improved survival and clinical utility of transplanted NPCs.

Allorecognition of human neural stem cells by peripheral blood lymphocytes despite low expression of MHC molecules: role of TGF-beta in modulating proliferation

Neural stem cells (NSCs) transplantation has been proposed as a means of restoring damaged brain tissue, a possibility rendered more likely by reports of low NSCs immunogenicity in various experimental models because of low expression of MHC class I and II as well as co-stimulatory molecules. We investigated the immunogenicity of a human NSC line grown in normal culture conditions and in the presence of pro-inflammatory cytokines IFN-gamma and tumor necrosis factor alpha by one-way mixed lymphocyte reaction (MLR) experiments with peripheral blood lymphocytes from eight HLA-incompatible donors. NSCs stimulated lymphocyte proliferation in almost all donors tested, with stimulation indices in the range of the low-end distribution curve of MLR between donors. The healthy subject that gave negative MLR results was the best compatible donor with respect to NSC haplotype. Since we observed low MLR responses overall, we studied if NSCs might exert any immunomodulatory activity. We detected transcription and release of the immunomodulatory molecule transforming growth factor beta (TGF-beta)-1; moreover, the addition of TGF-beta1 in MLR experiments down-regulated proliferative responses. To further confirm the immunological potential of human NSCs, we studied xenogeneic recognition of NSCs by immunocompetent cells derived from C57BL/6 mice, showing that NSCs can elicit an allo(xeno) response ex vivo. Our data indicate that NSCs have low but not negligible immunogenic potential that is sufficient to activate peripheral lymphocytes. Secretion of TGF-beta1 might balance the immunogenicity of NSCs. Nevertheless, the possibility that allo-NSCs grafting might induce in the long term an immune activation, thus vanishing their therapeutical effect, should not be overlooked and deserves further investigation.

Migration of neural precursor cells derived from olfactory bulb in cochlear nucleus exposed to an augmented acoustic environment

The regeneration of the auditory neural system remains a challenge in hearing restoration. Acoustic signals may induce a site-specific cell replacement in the auditory system. This hypothesis was tested with grafted implantation of neural precursor cells (NPCs) along the cochlear nucleus in the adult host followed by an augmented acoustic stimulation. NPCs were obtained from the olfactory bulbs at embryonic day 14-16 and were transplanted into the inside border of cochlear nucleus. The labeled cells survived at least 2 weeks, verified by Hoechst 33342 fluorescence, and by immunostaining for a neuronal marker. In some cases NPCs had migrated directionally to the root of the auditory nerve. This observation demonstrates the survival and migration of NPCs from the olfactory bulb (OB) along the adult auditory nerve in an augmented acoustic environment following implantation.

Generation of functional dopamine neurons from neural precursor cells isolated from the subventricular zone and white matter of the adult rat brain using Nurr1 overexpression

Neural precursor (NP) cells from adult mammalian brains can be isolated, expanded in vitro, and potentially used as cell replacement source material for treatment of intractable brain disorders. Reduced ethical concerns, lack of teratoma formation, and possible ex vivo autologous transplantation are critical advantages to using adult NP donor cells over cells from fetal brain tissue or embryonic stem cells. However, the usage of adult NP cells is limited by the ability to induce specific neurochemical phenotypes in these cells. Here, we demonstrate induction of a dopaminergic phenotype in NP cells isolated from the subventricular zone (SVZ) and white matter of rodent adult brains using overexpression of the nuclear receptor Nurr1 in vitro. Forced expression of Nurr1, a transcriptional factor specific to midbrain dopamine (DA) neuron development, caused in the adult cells an acquisition of the DA neurotransmitter phenotype and sufficient differentiation toward morphologically, phenotypically, and ultrastructurally mature DA neurons. Co-expression of neurogenic factor Mash1 and treatment with neurogenic cytokines brain-derived neurotrophic factor and neurotrophin-3 greatly enhanced Nurr1-induced DA neuron yield. The Nurr1-induced DA neurons demonstrated in vitro presynaptic DA neuronal functionality, releasing DA neurotransmitter in response to depolarization stimuli and specific DA reuptake. Furthermore, Nurr1-engineered adult SVZ NP cells survived, integrated, and differentiated into DA neurons in vivo that can reverse the behavioral deficit in the host striatum of parkinsonian rats. These findings open the possibility for the use of precursor cells from adult brains as a cell source for neuronal replacement treatment of Parkinson disease. Disclosure of potential conflicts of interest is found at the end of this article.