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

Advances in Genetic Reprogramming: Prospects from Developmental Biology to Regenerative Medicine

The foundations of cell reprogramming were laid by Yamanaka and co-workers, who showed that somatic cells can be reprogrammed into pluripotent cells (induced pluripotency). Since this discovery, the field of regenerative medicine has seen advancements. For example, because they can differentiate into multiple cell types, pluripotent stem cells are considered vital components in regenerative medicine aimed at the functional restoration of damaged tissue. Despite years of research, both replacement and restoration of failed organs/ tissues have remained elusive scientific feats. However, with the inception of cell engineering and nuclear reprogramming, useful solutions have been identified to counter the need for compatible and sustainable organs. By combining the science underlying genetic engineering and nuclear reprogramming with regenerative medicine, scientists have engineered cells to make gene and stem cell therapies applicable and effective. These approaches have enabled the targeting of various pathways to reprogramme cells, i.e., make them behave in beneficial ways in a patient-specific manner. Technological advancements have clearly supported the concept and realization of regenerative medicine. Genetic engineering is used for tissue engineering and nuclear reprogramming and has led to advances in regenerative medicine. Targeted therapies and replacement of traumatized , damaged, or aged organs can be realized through genetic engineering. Furthermore, the success of these therapies has been validated through thousands of clinical trials. Scientists are currently evaluating induced tissue-specific stem cells (iTSCs), which may lead to tumour-free applications of pluripotency induction. In this review, we present state-of-the-art genetic engineering that has been used in regenerative medicine. We also focus on ways that genetic engineering and nuclear reprogramming have transformed regenerative medicine and have become unique therapeutic niches.

Genetically engineered neural stem cells (NSCs) therapy for neurological diseases; state-of-the-art

Neural stem cells (NSCs) are multipotent stem cells with remarkable self-renewal potential and also unique competencies to differentiate into neurons, astrocytes, and oligodendrocytes (ODCs) and improve the cellular microenvironment. In addition, NSCs secret diversity of mediators, including neurotrophic factors (e.g., BDNF, NGF, GDNF, CNTF, and NT-3), pro-angiogenic mediators (e.g., FGF-2 and VEGF), and anti-inflammatory biomolecules. Thereby, NSCs transplantation has become a reasonable and effective treatment for various neurodegenerative disorders by their capacity to induce neurogenesis and vasculogenesis and dampen neuroinflammation and oxidative stress. Nonetheless, various drawbacks such as lower migration and survival and less differential capacity to a particular cell lineage concerning the disease pathogenesis hinder their application. Thus, genetic engineering of NSCs before transplantation is recently regarded as an innovative strategy to bypass these hurdles. Indeed, genetically modified NSCs could bring about more favored therapeutic influences post-transplantation in vivo, making them an excellent option for neurological disease therapy. This review for the first time offers a comprehensive review of the therapeutic capability of genetically modified NSCs rather than naïve NSCs in neurological disease beyond brain tumors and sheds light on the recent progress and prospect in this context.

Transplantation of modified human bone marrow-derived stromal cells affords therapeutic effects on cerebral ischemia in rats

AIMS

SB623 cells are human bone marrow stromal cells transfected with Notch1 intracellular domain. In this study, we examined potential regenerative mechanisms underlying stereotaxic transplantation of SB623 cells in rats with experimental acute ischemic stroke.

METHODS

We prepared control group, empty capsule (EC) group, SB623 cell group (SB623), and encapsulated SB623 cell (eSB623) group. Transient middle cerebral artery occlusion (MCAO) was performed on day 0, and 24 h after MCAO, stroke rats received transplantation into the envisioned ischemic penumbra. Modified neurological severity score (mNSS) was evaluated, and histological evaluations were performed.

RESULTS

In the mNSS, SB623 and eSB623 groups showed significant improvement compared to the other groups. Histological analysis revealed that the infarction area in SB623 and eSB623 groups was reduced. In the eSB623 group, robust cell viability and neurogenesis were detected in the subventricular zone that increased significantly compared to all other groups.

CONCLUSION

SB623 cells with or without encapsulation showed therapeutic effects on ischemic stroke. Encapsulated SB623 cells showed enhanced neurogenesis and increased viability inside the capsules. This study reveals the mechanism of secretory function of transplanted SB623 cells, but not cell-cell interaction as primarily mediating the cells' functional benefits in ischemic stroke.

Using Extracellular Vesicles Released by GDNF-Transfected Macrophages for Therapy of Parkinson Disease

Extracellular vesicles (EVs) are cell-derived nanoparticles that facilitate transport of proteins, lipids, and genetic material, playing important roles in intracellular communication. They have remarkable potential as non-toxic and non-immunogenic nanocarriers for drug delivery to unreachable organs and tissues, in particular, the central nervous system (CNS). Herein, we developed a novel platform based on macrophage-derived EVs to treat Parkinson disease (PD). Specifically, we evaluated the therapeutic potential of EVs secreted by autologous macrophages that were transfected ex vivo to express glial-cell-line-derived neurotrophic factor (GDNF). EV-GDNF were collected from conditioned media of GDNF-transfected macrophages and characterized for GDNF content, size, charge, and expression of EV-specific proteins. The data revealed that, along with the encoded neurotrophic factor, EVs released by pre-transfected macrophages carry GDNF-encoding DNA. Four-month-old transgenic Parkin Q311(X)A mice were treated with EV-GDNF via intranasal administration, and the effect of this therapeutic intervention on locomotor functions was assessed over a year. Significant improvements in mobility, increases in neuronal survival, and decreases in neuroinflammation were found in PD mice treated with EV-GDNF. No offsite toxicity caused by EV-GDNF administration was detected. Overall, an EV-based approach can provide a versatile and potent therapeutic intervention for PD.

Transcorneal Electrical Stimulation Reduces Neurodegenerative Process in a Mouse Model of Glaucoma

Glaucoma is a neurodegenerative disease in which the retinal ganglion cell axons of the optic nerve degenerate concomitant with synaptic changes in the retina, leading finally to death of the retinal ganglion cells (RGCs). Electrical stimulation has been used to improve neural regeneration in a variety of systems, including in diseases of the retina. Therefore, the focus of this study was to investigate whether transcorneal electrical stimulation (TES) in the DBA2/J mouse model of glaucoma could improve retinal or optic nerve pathology and serve as a minimally invasive treatment option. Mice (10 months-old) received 21 sessions of TES over 8 weeks, after which we evaluated RGC number, axon number, and anterograde axonal transport using histology and immunohistochemistry. To gain insight into the mechanism of proposed protection, we also evaluated inflammation by quantifying CD3+ T-cells and Iba1+ microglia; perturbations in metabolism were shown via the ratio pAMPK to AMPK, and changes in trophic support were tested using protein capillary electrophoresis. We found that TES resulted in RGC axon protection, a reduction in inflammatory cells and their activation, improved energy homeostasis, and a reduction of the cell death-associated p75NTR. Collectively, the data indicated that TES maintained axons, decreased inflammation, and increased trophic factor support, in the form of receptor presence and energy homeostasis, suggesting that electrical stimulation impacts several facets of the neurodegenerative process in glaucoma.

Safe nanoengineering and incorporation of transplant populations in a neurosurgical grade biomaterial, DuraGen PlusTM, for protected cell therapy applications

High transplant cell loss is a major barrier to translation of stem cell therapy for pathologies of the brain and spinal cord. Encapsulated delivery of stem cells in biomaterials for cell therapy is gaining popularity but experimental research has overwhelmingly used laboratory grade materials unsuitable for human clinical use - representing a further barrier to clinical translation. A potential solution is to use neurosurgical grade materials routinely used in clinical protocols which have an established human safety profile. Here, we tested the ability of Duragen Plus™ - a clinical biomaterial used widely in neurosurgical duraplasty procedures, to support the growth and differentiation of neural stem cells- a major transplant population being tested in clinical trials for neurological pathology. Genetic engineering of stem cells yields augmented therapeutic cells, so we further tested the ability of the Duragen Plus™ matrix to support stem cells engineered using magnetofection technology and minicircle DNA vectors- a promising cell engineering approach we previously reported (Journal of Controlled Release, 2016 a &b). The safety of the nano-engineering approach was analysed for the first time using sophisticated data-independent analysis by mass spectrometry-based proteomics. We prove that the Duragen Plus™ matrix is a promising biomaterial for delivery of stem cell transplant populations, with no adverse effects on key regenerative parameters. This advanced cellular construct based on a combinatorial nano-engineering and biomaterial encapsulation approach, could therefore offer key advantages for clinical translation.

GDNF-expressing macrophages restore motor functions at a severe late-stage, and produce long-term neuroprotective effects at an early-stage of Parkinson's disease in transgenic Parkin Q311X(A) mice

There is an unmet medical need in the area of Parkinson's disease (PD) to develop novel therapeutic approaches that can stop and reverse the underlying mechanisms responsible for the neuronal death. We previously demonstrated that systemically administered autologous macrophages transfected ex vivo to produce glial cell line-derived neurotrophic factor (GDNF) readily migrate to the mouse brain with acute toxin-induced neuroinflammation and ameliorate neurodegeneration in PD mouse models. We hypothesized that the high level of cytokines due to inflammatory process attracted GDNF-expressing macrophages and ensured targeted drug delivery to the PD brain. Herein, we validated a therapeutic potential of GDNF-transfected macrophages in a transgenic Parkin Q311X(A) mice with slow progression and mild brain inflammation. Systemic administration of GDNF-macrophages at a severe late stage of the disease leaded to a near complete restoration of motor functions in Parkin Q311X(A) mice and improved brain tissue integrity with healthy neuronal morphology. Furthermore, intravenous injections of GDNF-macrophages at an early stage of disease resulted in potent sustained therapeutic effects in PD mice for more than a year after the treatment. Importantly, multiple lines of evidence for therapeutic efficacy were observed including: diminished neuroinflammation and α-synuclein aggregation, increased survival of dopaminergic neurons, and improved locomotor functions. In summary, GDNF-transfected macrophages represent a promising therapeutic strategy for PD at both late- and early-stages of the disease.

Neural regeneration by regionally induced stem cells within post-stroke brains: Novel therapy perspectives for stroke patients

Ischemic stroke is a critical disease which causes serious neurological functional loss such as paresis. Hope for novel therapies is based on the increasing evidence of the presence of stem cell populations in the central nervous system (CNS) and the development of stem-cell-based therapies for stroke patients. Although mesenchymal stem cells (MSCs) represented initially a promising cell source, only a few transplanted MSCs were present near the injured areas of the CNS. Thus, regional stem cells that are present and/or induced in the CNS may be ideal when considering a treatment following ischemic stroke. In this context, we have recently showed that injury/ischemia-induced neural stem/progenitor cells (iNSPCs) and injury/ischemia-induced multipotent stem cells (iSCs) are present within post-stroke human brains and post-stroke mouse brains. This indicates that iNSPCs/iSCs could be developed for clinical applications treating patients with stroke. The present study introduces the traits of mouse and human iNSPCs, with a focus on the future perspective for CNS regenerative therapies using novel iNSPCs/iSCs.

Exogenous neural stem cell transplantation for cerebral ischemia

Cerebral ischemic injury is the main manifestation of stroke, and its incidence in stroke patients is 70–80%. Although ischemic stroke can be treated with tissue-type plasminogen activator, its time window of effectiveness is narrow. Therefore, the incidence of paralysis, hypoesthesia, aphasia, dysphagia, and cognitive impairment caused by cerebral ischemia is high. Nerve tissue regeneration can promote the recovery of the aforementioned dysfunction. Neural stem cells can participate in the reconstruction of the damaged nervous system and promote the recovery of nervous function during self-repair of damaged brain tissue. Neural stem cell transplantation for ischemic stroke has been a hot topic for more than 10 years. This review discusses the treatment of ischemic stroke with neural stem cells, as well as the mechanisms of their involvement in stroke treatment.

MRI‐Visible siRNA Nanomedicine Directing Neuronal Differentiation of Neural Stem Cells in Stroke

A major challenge in stroke treatment is the restoration of neural circuit in which neuron function plays a central role. Although transplantation of exogenous neural stem cells (NSCs) is admittedly a promising therapeutical means, the treatment outcome is greatly affected due to the poor NSCs differentiation into neurons caused by myelin associated inhibitory factors binding to Nogo‐66 receptor (NgR). Herein, a nanoscale polymersome is developed to codeliver superparamagnetic iron oxide nanoparticles and siRNA targeting NgR gene (siNgR) into NSCs. This multifunctional nanomedicine directs neuronal differentiation of NSCs through silencing the NgR gene and meanwhile allows a noninvasive monitoring of NSC migration with magnetic resonance imaging. An improved recovery of neural function is achieved in rat ischemic stroke model. The results demonstrate the great potential of the multifunctional siRNA nanomedicine in stroke treatment based on stem cell transplantation.

Long-Term Potentiation Enhances Neuronal Differentiation in the Chronic Hypoperfusion Model of Rats

Several reports have shown that long-term potentiation (LTP) per se effectively enhances neurogenesis in the hippocampus of intact animals. If LTP can enhance neurogenesis in chronic hypoperfusion, this approach could potentially become a new therapeutic strategy for the restoration of cognitive function and for prevention from deterioration of mild cognitive impairment (MCI). Using an in vivo LTP model of rats, we examined whether LTP per se can enhance neurogenesis in hypoperfusion rats that underwent permanent bilateral common carotid artery occlusion (permanent 2-vessel occlusion, P2VO). High frequency stimulation (HFS) in the subacute phase after P2VO enhanced hippocampal cell proliferation and neurogenesis. However, most enhanced cell proliferation and neurogenesis was seen in the hypoperfusion rats that received HFS and for which LTP could finally be induced. In contrast, the same effect was not seen in the LTP induction in the chronic phase. The present findings, which reveal that most enhanced neurogenesis was seen in hypoperfusion rats for which LTP could be finally induced, could explain the ability of LTP-like activities such as learning paradigms and environmental stimuli to increase the rate of neurogenesis in the hippocampus even under hypoperfusion conditions. Moreover, the present findings, which reveal that LTP induction in the chronic phase after P2VO could not effectively enhance neurogenesis in the hypoperfusion rats, could indicate that patients with MCI and even middle-aged healthy control individuals should start LTP-like activities as early as possible and continue with these activities to prevent age-related deterioration of hippocampal function.

Novel Regenerative Therapies Based on Regionally Induced Multipotent Stem Cells in Post-Stroke Brains: Their Origin, Characterization, and Perspective

Brain injuries such as ischemic stroke cause severe neural loss. Until recently, it was believed that post-ischemic areas mainly contain necrotic tissue and inflammatory cells. However, using a mouse model of cerebral infarction, we demonstrated that stem cells develop within ischemic areas. Ischemia-induced stem cells can function as neural progenitors; thus, we initially named them injury/ischemia-induced neural stem/progenitor cells (iNSPCs). However, because they differentiate into more than neural lineages, we now refer to them as ischemia-induced multipotent stem cells (iSCs). Very recently, we showed that putative iNSPCs/iSCs are present within post-stroke areas in human brains. Because iNSPCs/iSCs isolated from mouse and human ischemic tissues can differentiate into neuronal lineages in vitro, it is possible that a clearer understanding of iNSPC/iSC profiles and the molecules that regulate iNSPC/iSC fate (e.g., proliferation, differentiation, and survival) would make it possible to perform neural regeneration/repair in patients following stroke. In this article, we introduce the origin and traits of iNSPCs/iSCs based on our reports and recent viewpoints. We also discuss their possible contribution to neurogenesis through endogenous and exogenous iNSPC/iSC therapies following ischemic stroke.

A novel polymeric micelle used for in vivo MR imaging tracking of neural stem cells in acute ischemic stroke

Novel cationic polymeric micelles based on biodegradable poly(aspartic acid-dimethylethanediamine)–lysine–cholic acid were synthesized for in vivo tracking therapeutic stem cells using MRI.

Modification of Bone Marrow Stem Cells for Homing and Survival During Cerebral Ischemia

Over the last decade, major advances have been made in stem cell-based therapy for ischemic stroke, which is one of the leading causes of death and disability worldwide. Various stem cells from bone marrow, such as mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and endothelial progenitor cells (EPCs), have shown therapeutic potential for stroke. Concomitant with these exciting findings are some fundamental bottlenecks that must be overcome in order to accelerate their clinical translation, including the low survival and engraftment caused by the harsh microenvironment after transplantation. In this chapter, strategies such as gene modification, hypoxia/growth factor preconditioning, and biomaterial-based methods to improve cell survival and homing are summarized, and the potential strategies for their future application are also discussed.

Lentivirus-mediated Persephin over-expression in Parkinson's disease rats

Persephin, together with glial cell line-derived neurotrophic factor and neurturin, has a neurotrophic effect and promotes the survival of motor neurons cultured in vitro. In this study, dopaminergic neurons in the substantia nigra of rats were transfected with the Persephin gene. One week later 6-hydroxydopamine was injected into the anterior medial bundle to establish a Parkinson's disease model in the rats. Results found that the number of dopaminergic neurons in the substantia nigra increased, tyrosine hydroxylase expression was upregulated and concentrations of dopamine and its metabolites in corpus striatum were increased after pretreatment with Persephin gene. In addition, the rotating effect of the induced Parkinson's disease rats was much less in the group pretreated with the Persephin gene. Persephin has a neuroprotective effect on the 6-hydroxydopamine-induced Parkinson's disease through protecting dopaminergic neurons.

Intra-Arterial Transplantation of Allogeneic Mesenchymal Stem Cells Mounts Neuroprotective Effects in a Transient Ischemic Stroke Model in Rats: Analyses of Therapeutic Time Window and Its Mechanisms

Objective

Intra-arterial stem cell transplantation exerts neuroprotective effects for ischemic stroke. However, the optimal therapeutic time window and mechanisms have not been completely understood. In this study, we investigated the relationship between the timing of intra-arterial transplantation of allogeneic mesenchymal stem cells (MSCs) in ischemic stroke model in rats and its efficacy in acute phase.

Methods

Adult male Wistar rats weighing 200 to 250g received right middle cerebral artery occlusion (MCAO) for 90 minutes. MSCs (1×10⁶cells/ 1ml PBS) were intra-arterially injected at either 1, 6, 24, or 48 hours (1, 6, 24, 48h group) after MCAO. PBS (1ml) was intra-arterially injected to control rats at 1 hour after MCAO. Behavioral test was performed immediately after reperfusion, and at 3, 7 days after MCAO using the Modified Neurological Severity Score (mNSS). Rats were euthanized at 7 days after MCAO for evaluation of infarct volumes and the migration of MSCs. In order to explore potential mechanisms of action, the upregulation of neurotrophic factor and chemotactic cytokine (bFGF, SDF-1α) induced by cell transplantation was examined in another cohort of rats that received intra-arterial transplantation at 24 hours after recanalization then euthanized at 7 days after MCAO for protein assays.

Results

Behavioral test at 3 and 7 days after transplantation revealed that stroke rats in 24h group displayed the most robust significant improvements in mNSS compared to stroke rats in all other groups (p’s<0.05). Similarly, the infarct volumes of stroke rats in 24h group were much significantly decreased compared to those in all other groups (p’s<0.05). These observed behavioral and histological effects were accompanied by MSC survival and migration, with the highest number of integrated MSCs detected in the 24h group. Moreover, bFGF and SDF-1α levels of the infarcted cortex were highly elevated in the 24h group compared to control group (p’s<0.05).

Conclusions

These results suggest that intra-arterial allogeneic transplantation of MSCs provides post-stroke functional recovery and reduction of infarct volumes in ischemic stroke model of rats. The upregulation of bFGF and SDF-1α likely played a key mechanistic role in enabling MSC to afford functional effects in stroke. MSC transplantation at 24 hours after recanalization appears to be the optimal timing for ischemic stroke model, which should guide the design of clinical trials of cell transplantation for stroke patients.

A possible new focus for stroke treatment - migrating stem cells

INTRODUCTION

Stroke is a leading cause of mortality in the US. More so, its infliction often leaves patients with lasting morbidity and deficits. Ischemic stroke comprises nearly 90% of incidents and the majority of medical treatment aims at reestablishing perfusion and preventing recurrence.

AREAS COVERED

Long-term options for neurorestoration are limited by the infancy of their innovative approach. Accumulating evidence suggests the therapeutic potential of stem cells in neurorestoration, however, proper stem cell migration remains a challenge in translating stem cell therapy from the laboratory to the clinic. In this paper, we propose the role that exogenous stem cell transplantation may serve in facilitating the migration of endogenous stem cells to the site of injury, an idea termed 'biobridge'.

EXPERT OPINION

Recent research in the field of traumatic brain injury has provided a foundational understanding that, through the use of exogenous stem cells, native tissue architecture may be manipulated by proteinases to allow better communication between the endogenous sites of neural stem cells and the regions of injury. There is still much to be learned about these mechanisms, though it is the devastating nature of stroke that necessitates continued research into the prospective therapeutic potential of this novel approach.

Using magnetic nanoparticles for gene transfer to neural stem cells: stem cell propagation method influences outcomes

Genetically engineered neural stem cell (NSC) transplants offer a key strategy to augment neural repair by releasing therapeutic biomolecules into injury sites. Genetic modification of NSCs is heavily reliant on viral vectors but cytotoxic effects have prompted development of non-viral alternatives, such as magnetic nanoparticle (MNPs). NSCs are propagated in laboratories as either 3-D suspension “neurospheres” or 2-D adherent “monolayers”. MNPs deployed with oscillating magnetic fields (“magnetofection technology”) mediate effective gene transfer to neurospheres but the efficacy of this approach for monolayers is unknown. It is important to address this issue as oscillating magnetic fields dramatically enhance MNP-based transfection in transplant cells (e.g., astrocytes and oligodendrocyte precursors) propagated as monolayers. We report for the first time that oscillating magnetic fields enhanced MNP-based transfection with reporter and functional (basic fibroblast growth factor; FGF2) genes in monolayer cultures yielding high transfection versus neurospheres. Transfected NSCs showed high viability and could re-form neurospheres, which is important as neurospheres yield higher post-transplantation viability versus monolayer cells. Our results demonstrate that the combination of oscillating magnetic fields and a monolayer format yields the highest efficacy for MNP-mediated gene transfer to NSCs, offering a viable non-viral alternative for genetic modification of this important neural cell transplant population.

Comparison of the effects of human dental pulp stem cells and human bone marrow-derived mesenchymal stem cells on ischemic human astrocytes in vitro

This study assesses the cytoprotective effects of human dental pulp stem cells (hDPSCs) and conditioned medium from hDPSCs (CM-hDPSCs) on ischemic human astrocytes (hAs) in vitro compared with human bone marrow-derived mesenchymal stem cells (hMSCs). Ischemia of hAs was induced by oxygen-glucose deprivation (OGD). CM-hDPSCs and hMSCs were collected after 48 hr of culture. Cell death was determined by 3-[4,5-dimethylthialzol-2-yl]-2,5-diphenyltetrazolium bromide and cellular ATP assays. The expression of glial fibrillary acidic protein (GFAP) and musashi-1 as markers of reactive astrogliosis was examined with immunochemical staining. mRNA expression and reactive oxygen species (ROS) were analyzed by RT-PCR and flow cytometry, respectively. OGD increased cytotoxicity in a time-dependent manner and decreased cellular ATP content concomitantly in hAs. Pretreatment and posttreatment with hDPSCs were associated with greater recovery from OGD-induced cytotoxicity in hAs compared with hMSCs. Similarly, CM-hDPSCs had a greater effect on OGD-induced cytotoxicity in a dose-dependent manner. Pre- and posttreatment with CM-hDPSCs or CM-hMSCs attenuated OGD-induced GFAP, nestin, and musashi-1 expression in hAs. Furthermore, treatment of cells with CM-hDPSCs and hMSCs blocked OGD-induced ROS production and interleukin-1ß upregulation. This study demonstrates for the first time that hDPSCs and CM-hDPSCs confer superior cytoprotection against cell death in an in vitro OGD model compared with hMSCs as shown by cell viability assay. Reactive gliosis, ROS production, and inflammatory mediators might contribute to this protective effect. Therefore, hDPSCs could represent an alternative source of cell therapy for ischemic stroke.

Neuroprotective effects of GDNF-expressing human amniotic fluid cells

Brain injury continues to be one of the leading causes of disability worldwide. Despite decades of research, there is currently no pharmacologically effective treatment for preventing neuronal loss and repairing the brain. As a result, novel therapeutic approaches, such as cell-based therapies, are being actively pursued to repair tissue damage and restore neurological function after injury. In this study, we examined the neuroprotective potential of amniotic fluid (AF) single cell clones, engineered to secrete glial cell derived neurotrophic factor (AF-GDNF), both in vitro and in a surgically induced model of brain injury. Our results show that pre-treatment with GDNF significantly increases cell survival in cultures of AF cells or cortical neurons exposed to hydrogen peroxide. Since improving the efficacy of cell transplantation depends on enhanced graft cell survival, we investigated whether AF-GDNF cells seeded on polyglycolic acid (PGA) scaffolds could enhance graft survival following implantation into the lesion cavity. Encouragingly, the AF-GDNF cells survived longer than control AF cells in serum-free conditions and continued to secrete GDNF both in vitro and following implantation into the injured motor cortex. AF-GDNF implantation in the acute period following injury was sufficient to activate the MAPK/ERK signaling pathway in host neural cells in the peri-lesion area, potentially boosting endogenous neuroprotective pathways. These results were complemented with promising trends in beam walk tasks in AF-GDNF/PGA animals during the 7 day timeframe. Further investigation is required to determine whether significant behavioural improvement can be achieved at a longer timeframe.

Gel phantom study with high-intensity focused ultrasound: influence of metallic stent containing either air or fluid

We aimed to investigate whether a cylindrical structure containing either air or fluid and with or without a metallic stent affects the volume and density of cavitation produced by high-intensity focused ultrasound via a gel phantom study. Sixteen tissue-mimicking phantoms based on a polyacrylamide gel mixed with bovine serum albumin with a cylindrical hole 1 cm in diameter and 7.5 cm in length were divided into four groups of four phantoms with air in the holes (group 1), four phantoms with fluid in the holes (group 2), four phantoms with air-containing metallic stents (group 3) and four phantoms with fluid-containing metallic stents (group 4). A pulsed high-intensity focused ultrasound beam (50% duty cycle, 40-Hz pulse repetition frequency) at 75 W of acoustic power was directed perpendicularly to the longitudinal axis of the hole, with its focus at the posterior wall of the hole. The size of the cavitation on the x-, y-, and z-axes was measured, and the volumes of cavitation and coagulation were calculated using the formula for the volume of an elliptical cone. The density of cavitation was measured in the tissue phantom anterior to the hole with a 1 × 1-cm square region of interest. For statistical analysis, the Kruskal-Wallis test and Mann-Whitney U-test were used. The phantoms with air-containing holes (groups 1 and 3) developed larger and denser cavitations anterior to the focus, without unnecessary coagulation posterior to the focus, compared with the phantoms with fluid-containing holes (groups 2 and 4), regardless of the presence of stents. All of the axes and volumes of the anterior cavitations were significantly larger than those of the posterior cavitations in groups 1 and 3 (all p-values <0.05). The results of this study might be applied to maximize cavitation to enhance drug delivery into tumors.

Stem cell therapies for the treatment of radiation-induced normal tissue side effects

SIGNIFICANCE

Targeted irradiation is an effective cancer therapy but damage inflicted to normal tissues surrounding the tumor may cause severe complications. While certain pharmacologic strategies can temper the adverse effects of irradiation, stem cell therapies provide unique opportunities for restoring functionality to the irradiated tissue bed.

RECENT ADVANCES

Preclinical studies presented in this review provide encouraging proof of concept regarding the therapeutic potential of stem cells for treating the adverse side effects associated with radiotherapy in different organs. Early-stage clinical data for radiation-induced lung, bone, and skin complications are promising and highlight the importance of selecting the appropriate stem cell type to stimulate tissue regeneration.

CRITICAL ISSUES

While therapeutic efficacy has been demonstrated in a variety of animal models and human trials, a range of additional concerns regarding stem cell transplantation for ameliorating radiation-induced normal tissue sequelae remain. Safety issues regarding teratoma formation, disease progression, and genomic stability along with technical issues impacting disease targeting, immunorejection, and clinical scale-up are factors bearing on the eventual translation of stem cell therapies into routine clinical practice.

FUTURE DIRECTIONS

Follow-up studies will need to identify the best possible stem cell types for the treatment of early and late radiation-induced normal tissue injury. Additional work should seek to optimize cellular dosing regimes, identify the best routes of administration, elucidate optimal transplantation windows for introducing cells into more receptive host tissues, and improve immune tolerance for longer-term engrafted cell survival into the irradiated microenvironment.

L-serine treatment may improve neurorestoration of rats after permanent focal cerebral ischemia potentially through improvement of neurorepair

The present study was conducted to clarify whether treatment with L-serine can improve the brain repair and neurorestoration of rats after permanent middle cerebral artery occlusion (pMCAO). After pMCAO, the neurological functions, brain lesion volume, and cortical injury were determined. GDNF, NGF, NCAM L1, tenascin-C, and Nogo-A levels were measured. Proliferation and differentiation of the neural stem cells (NSCs) and proliferation of the microvessels in the ischemic boundary zone of the cortex were evaluated. Treatment with L-serine (168 mg/kg body weight, i.p.) began 3 h after pMCAO and was repeated every 12 h for 7 days or until the end of the experiment. L-Serine treatment: 1) reduced the lesion volume and neuronal loss; 2) improved the recovery of neurological functions; 3) elevated the expression of nerve growth-related factors; and 4) facilitated the proliferation of endogenous NSCs and microvessels activated after pMCAO and increased the number of new-born neurons. 5) D-cycloserine, an inhibitor of serine hydroxymethyltransferase, blunted the effects of L-serine on NSC proliferation, differentiation, microvascular proliferation. In conclusions, L-serine treatment in pMCAO rats can reduce brain injury and facilitate neurorestoration which is partly associated with the improvement of proliferation of NSCs and microvessels, reconstruction of neurovascular units and resultant neurorepair. The effects of L-serine on endogenous NSC proliferation and microvascular proliferation are partly mediated by the action of L-serine as a substrate for the production of one-carbon groups used for purine and pyrimidine synthesis and modulation of the expression of some nerve growth-related factors.

Neuroprotective effects of liraglutide for stroke model of rats

The number of diabetes mellitus (DM) patients is increasing, and stroke is deeply associated with DM. Recently, neuroprotective effects of glucagon-like peptide-1 (GLP-1) are reported. In this study, we explored whether liraglutide, a GLP-1 analogue exerts therapeutic effects on a rat stroke model. Wistar rats received occlusion of the middle cerebral artery for 90 min. At one hour after reperfusion, liraglutide or saline was administered intraperitoneally. Modified Bederson's test was performed at 1 and 24 h and, subsequently, rats were euthanized for histological investigation. Peripheral blood was obtained for measurement of blood glucose level and evaluation of oxidative stress. Brain tissues were collected to evaluate the level of vascular endothelial growth factor (VEGF). The behavioral scores of liraglutide-treated rats were significantly better than those of control rats. Infarct volumes of liraglutide-treated rats at were reduced, compared with those of control rats. The level of derivatives of reactive oxygen metabolite was lower in liraglutide-treated rats. VEGF level of liraglutide-treated rats in the cortex, but not in the striatum significantly increased, compared to that of control rats. In conclusion, this is the first study to demonstrate neuroprotective effects of liraglutide on cerebral ischemia through anti-oxidative effects and VEGF upregulation.

Comparison of ectopic gene expression methods in rat neural stem cells

Neural stem cells (NSCs) have the ability to proliferate and differentiate into various types of cells that compose the nervous system. To study functions of genes in stem cell biology, genes or siRNAs need to be transfected. However, it is difficult to transfect ectopic genes into NSCs. Thus to identify the suitable method to achieve high transfection efficiency, we compared lipid transfection, electroporation, nucleofection and retroviral transduction. Among the methods that we tested, we found that nucleofection and retroviral transduction showed significantly increased transfection efficiency. In addition, with retroviral transduction of Ngn2 that is known to induce neurogenesis in various types of cells, we observed facilitated final cell division in rat NSCs. These data suggest that nucleofection and retroviral transduction provide high efficiency of gene delivery system to study functions of genes in rat NSCs.

Neurotrophin-induced migration and neuronal differentiation of multipotent astrocytic stem cells in vitro

Hypoxic ischemic encephalopathy (HIE) affects 2-3 per 1000 full-term neonates. Up to 75% of newborns with severe HIE die or have severe neurological handicaps. Stem cell therapy offers the potential to replace HIE-damaged cells and enhances the autoregeneration process. Our laboratory implanted Multipotent Astrocytic Stem Cells (MASCs) into a neonatal rat model of hypoxia-ischemia (HI) and demonstrated that MASCs move to areas of injury in the cortex and hippocampus. However, only a small proportion of the implanted MASCs differentiated into neurons. MASCs injected into control pups did not move into the cortex or differentiate into neurons. We do not know the mechanism by which the MASCs moved from the site of injection to the injured cortex. We found neurotrophins present after the hypoxic-ischemic milieu and hypothesized that neurotrophins could enhance the migration and differentiation of MASCs. Using a Boyden chamber device, we demonstrated that neurotrophins potentiate the in vitro migration of stem cells. NGF, GDNF, BDNF and NT-3 increased stem cell migration when compared to a chemokinesis control. Also, MASCs had increased differentiation toward neuronal phenotypes when these neurotrophins were added to MASC culture tissue. Due to this finding, we believed neurotrophins could guide migration and differentiation of stem cell transplants after brain injury.

Neuroprotection by GDNF in the ischemic brain

The glial cell line-derived neurotrophic factor (GDNF) was first identified as a survival factor for midbrain dopaminergic neurons, but additional studies provided evidences for a role as a trophic factor for other neurons of the central and peripheral nervous systems. GDNF regulates cellular activity through interaction with glycosyl-phosphatidylinositol-anchored cell surface receptors, GDNF family receptor-α1, which might signal through the transmembrane Ret tyrosine receptors or the neural cell adhesion molecule, to promote cell survival, neurite outgrowth, and synaptogenesis. The neuroprotective effect of exogenous GDNF has been shown in different experimental models of focal and global brain ischemia, by local administration of the trophic factor, using viral vectors carrying the GDNF gene and by transplantation of GDNF-expressing cells. These different strategies and the mechanisms contributing to neuroprotection by GDNF are discussed in this review. Importantly, neuroprotection by GDNF was observed even when administered after the ischemic injury.

Ischemia-induced neural stem/progenitor cells express pyramidal cell markers

Adult brain-derived neural stem cells have acquired a lot of interest as an endurable neuronal cell source that can be used for central nervous system repair in a wide range of neurological disorders such as ischemic stroke. Recently, we identified injury-induced neural stem/progenitor cells in the poststroke murine cerebral cortex. In this study, we show that, after differentiation in vitro, injury-induced neural stem/progenitor cells express pyramidal cell markers Emx1 and CaMKIIα, as well as mature neuron markers MAP2 and Tuj1. 5-bromo-2-deoxyuridinine-positive neurons in the peristroke cortex also express such pyramidal markers. The presence of newly regenerated pyramidal neurons in the poststroke brain might provide a noninvasive therapeutic strategy for stroke treatment with functional recovery.

Comparing the functional consequences of human stem cell transplantation in the irradiated rat brain

Radiotherapy is a frontline treatment for the clinical management of CNS tumors. Although effective in eradicating tumor cells, radiotherapy also depletes neural stem and progenitor cells in the hippocampus that are important for neurogenesis and cognitive function. Consequently, the use of radiation to control primary and metastatic brain tumors often leads to debilitating and progressive cognitive decrements in surviving patients, representing a serious medical condition that, to date, has no satisfactory, long-term solutions. As a result, we have explored the use of stem cells as therapeutic agents to improve cognition after radiotherapy. Our past work has demonstrated the capability of cranially transplanted human embryonic (hESCs) and neural (hNSCs) stem cells to functionally restore cognition in rats 1 and 4 months after head-only irradiation. We have now expanded our cognitive analyses with hESCs and quantified both survival and differentiated fates of engrafted cells at 1 and 4 months after irradiation. Our findings indicate the capability of hESC transplantation to ameliorate radiation-induced cognitive dysfunction 1 month following cranial irradiation, using a hippocampal-dependent novel place recognition task. Irradiated animals not engrafted with stem cells experienced prolonged and significant cognitive dysfunction. Stereological estimates indicated that 35% and 17% of the transplanted hESCs survived at 1 and 4 months postgrafting, respectively. One month after irradiation and grafting, phenotypic analyses revealed that 26% and 31% of the hESCs differentiated into neurons and astrocytes, while at the 4-month time, neuronal and astrocytic differentiation was 7% and 46%, respectively. Comparison between present and past data with hESCs and hNSCs demonstrates equivalent cognitive restoration and a preference of hNSCs to commit to neuronal versus astrocytic lineages over extended engraftment times. Our data demonstrate the functional utility of human stem cell replacement strategies for ameliorating the adverse effects of cranial irradiation on cognition.

Bystander effect on brain tissue of mesoangioblasts producing neurotrophins

Neurotrophic factors (NTFs) are involved in the regulation of neuronal survival and function and, thus, may be used to treat neurological diseases associated with neuronal death. A major hurdle for their clinical application is the delivery mode. We describe here a new strategy based on the use of progenitor cells called mesoangioblasts (MABs). MABs can be isolated from postnatal mesoderm tissues and, because of a high adhesin-dependent migratory capacity, can reach perivascular targets especially in damaged areas. We generated genetically modified MABs producing nerve growth factor (MABs-NGF) or brain-derived neurotrophic factor (MABs-BDNF) and assessed their bystander effects in vitro using PC12 cells, primary cultures, and organotypic cultures of adult hippocampal slices. MABs-NGF-conditioned medium induced differentiation of PC12 cells, while MABs-BDNF-conditioned medium increased viability of cultured neurons and slices. Slices cultured with MABs-BDNF medium also better retained their morphology and functional connections, and all these effects were abolished by the TrkB kinase blocker K252a or the BDNF scavenger TrkB-IgG. Interestingly, the amount of BDNF released by MABs-BDNF produced greater effects than an identical amount of recombinant BDNF, suggesting that other NTFs produced by MABs synergize with BDNF. Thus, MABs can be an effective vehicle for NTF delivery, promoting differentiation, survival, and functionality of neurons. In summary, MABs hold distinct advantages over other currently evaluated approaches for NTF delivery in the CNS, including synergy of MAB-produced NTF with the neurotrophins. Since MABs may be capable of homing into damaged brain areas, they represent a conceptually novel, promising therapeutic approach to treat neurodegenerative diseases.

Role of SDF1/CXCR4 interaction in experimental hemiplegic models with neural cell transplantation

Much attention has been focused on neural cell transplantation because of its promising clinical applications. We have reported that embryonic stem (ES) cell derived neural stem/progenitor cell transplantation significantly improved motor functions in a hemiplegic mouse model. It is important to understand the molecular mechanisms governing neural regeneration of the damaged motor cortex after the transplantation. Recent investigations disclosed that chemokines participated in the regulation of migration and maturation of neural cell grafts. In this review, we summarize the involvement of inflammatory chemokines including stromal cell derived factor 1 (SDF1) in neural regeneration after ES cell derived neural stem/progenitor cell transplantation in mouse stroke models.

Human neural stem cell transplantation ameliorates radiation-induced cognitive dysfunction

Cranial radiotherapy induces progressive and debilitating declines in cognition that may, in part, be caused by the depletion of neural stem cells. The potential of using stem cell replacement as a strategy to combat radiation-induced cognitive decline was addressed by irradiating athymic nude rats followed 2 days later by intrahippocampal transplantation with human neural stem cells (hNSC). Measures of cognitive performance, hNSC survival, and phenotypic fate were assessed at 1 and 4 months after irradiation. Irradiated animals engrafted with hNSCs showed significantly less decline in cognitive function than irradiated, sham-engrafted animals and acted indistinguishably from unirradiated controls. Unbiased stereology revealed that 23% and 12% of the engrafted cells survived 1 and 4 months after transplantation, respectively. Engrafted cells migrated extensively, differentiated along glial and neuronal lineages, and expressed the activity-regulated cytoskeleton-associated protein (Arc), suggesting their capability to functionally integrate into the hippocampus. These data show that hNSCs afford a promising strategy for functionally restoring cognition in irradiated animals.

Investigational therapies for ischemic stroke: neuroprotection and neurorecovery

Stroke is one of the leading causes of death and disability worldwide. Current treatment strategies for ischemic stroke primarily focus on reducing the size of ischemic damage and rescuing dying cells early after occurrence. To date, intravenous recombinant tissue plasminogen activator is the only United States Food and Drug Administration approved therapy for acute ischemic stroke, but its use is limited by a narrow therapeutic window. The pathophysiology of stroke is complex and it involves excitotoxicity mechanisms, inflammatory pathways, oxidative damage, ionic imbalances, apoptosis, angiogenesis, neuroprotection, and neurorestoration. Regeneration of the brain after damage is still active days and even weeks after a stroke occurs, which might provide a second window for treatment. A huge number of neuroprotective agents have been designed to interrupt the ischemic cascade, but therapeutic trials of these agents have yet to show consistent benefit, despite successful preceding animal studies. Several agents of great promise are currently in the middle to late stages of the clinical trial setting and may emerge in routine practice in the near future. In this review, we highlight select pharmacologic and cell-based therapies that are currently in the clinical trial stage for stroke.

Ambidextrous magnetic nanovectors for synchronous gene transfection and labeling of human MSCs

The synchronization of gene expression and cell trafficking in transfected stem cells is crucial for augmentation of stem cell functions (differentiation and neurotropic factor secretion) and real time in vivo monitoring. We report a magnetic nanoparticle-based gene delivery system that can ensure simultaneous gene delivery and in vivo cell trafficking by high resolution MR imaging. The polar aprotic solvent soluble MnFe₂O₄ nanoparticles were enveloped using cationic polymers (branched polyethyleneimine, PEI) by the solvent shifting method for a gene loading. Using our magnetic nanovector system (PEI-coated MnFe₂O₄ nanoparticles), thus, we synchronized stem cell migration and its gene expression in a rat stroke model.

GDNF-pretreatment enhances the survival of neural stem cells following transplantation in a rat model of Parkinson's disease

Cell transplantation has been shown to be an effective therapy for central nervous system disorders in animal models. Improving the efficacy of cell transplantation depends critically on improving grafted cell survival. We investigated whether glial cell line-derived neurotrophic factor (GDNF)-pretreatment of neural stem cells (NSCs) enhanced grafted cell survival in a rat model of Parkinson's disease (PD). We first examined the neuroprotective effects of GDNF on oxygen-glucose deprivation (OGD) in NSCs. Cells were pretreated with GDNF for 3 days before subjecting them to OGD. After 12h of OGD, GDNF-pretreated NSCs showed significant increases in survival rates compared with PBS-pretreated NSCs. An apoptosis assay showed that the number of apoptotic cells was significantly decreased in GDNF-pretreated NSCs at 1h and 6h after OGD. A PD rat model was then established by unilateral injection of 6-hydroxydopamine (6-OHDA, 9μg) into the medial forebrain bundle. Two weeks after 6-OHDA injection, GDNF-pretreated NSCs, PBS-pretreated NSCs, or PBS were injected into PD rat striatum. The survival of grafted cells in the striatum was significantly increased in the GDNF-pretreated NSC group compared with the control groups. GDNF pretreatment increased survival of NSCs following transplantation, at least partly through suppression of cell apoptosis.

Urinary 8-OHdG elevations in a partial lesion rat model of Parkinson's disease correlate with behavioral symptoms and nigrostriatal dopaminergic depletion

Increased oxidative stress contributes to pathogenesis of Parkinson's disease (PD). 8-hydroxy-2'-deoxyguanosine (8-OHdG) is the oxidation product most frequently measured as an indicator of oxidative DNA damage. Several studies have shown increased 8-OHdG in PD patients. There are few basic laboratory data examining 8-OHdG levels in animal models of PD. In this study, we utilized hemiparkinsonian model of rats induced by intrastriatal injection of 6-hydroxydopamine (6-OHDA). The urinary 8-OHdG level was measured in relation to behavioral and pathological deficits arising from 6-OHDA-induced neurotoxic effects on the nigrostriatal dopaminergic pathway. All rats were subjected to a series of behavioral tests for 42 days after 6-OHDA injection. We collected urine samples with subsequent measurement of 8-OHdG level using ELISA kits. For immunohistochemical evaluation, tyrosine hydroxylase (TH) staining was performed. Significant increments in urinary 8-OHdG level were observed continuously from day 7 until day 35 compared to control group, which showed a trend of elevation as early as day 3. Such elevated urinary 8-OHdG level significantly correlated with all of the behavioral deficits measured here, suggesting that urinary 8-OHdG level provides a good index of severity of parkinsonism. Urinary 8-OHdG level also had a significant positive correlation with the survival rate of dopaminergic fibers or neurons, advancing the concept that oxidative stress during the early phase of 6-OHDA neurotoxicity may correspond to disease progression closely approximating neuronal degeneration in the nigrostriatal dopaminergic system. The present results demonstrate that alterations in urinary 8-OHdG level closely approximate onset and disease progression in PD.

The transfection of multipotent neural precursor/stem cell transplant populations with magnetic nanoparticles

Multipotent neural precursor/stem cells (NPCs) are a major transplant population with key properties to promote repair in several neuropathological conditions. Magnetic nanoparticle (MNP)-based vector systems, in turn, offer a combination of key benefits for cell therapies including (i) safety (ii) delivery of therapeutic biomolecules (DNA/siRNA) enhanceable by 'magnetofection' approaches (iii) magnetic cell targeting of MNP-labelled cells to injury sites and (iv) non-invasive imaging of MNP-labelled transplant populations for cell tracking. However, the applications of the versatile MNP platform for NPC transplantation therapies have received limited attention so far. We have evaluated the potential of MNP vectors for gene transfer to NPCs using a neurosphere culture model system; we also assessed repeat transfection ("multifection") and repeat transfection plus applied magnetic field ("magneto-multifection") strategies [to enhance transfection efficiency]. We show for the first time that MNPs can safely mediate single/combinatorial gene delivery to NPCs. Multifection approaches significantly enhanced transfection with negligible toxicity; no adverse effects were observed on stem cell proliferation/differentiation. "Multifected" NPCs survived and differentiated in 3D neural tissue arrays post-transplantation. Our findings demonstrate that MNPs offer a simple and robust alternative to the viral vector systems currently used widely to transfect neural stem cells in neurobiology/neural transplantation research.

Long-term magnetic resonance imaging of stem cells in neonatal ischemic injury

OBJECTIVE

Quantitative magnetic resonance imaging (MRI) can serially and noninvasively assess the degree of injury in rat pup models of hypoxic ischemic injury (HII). It can also noninvasively monitor stem cell migration following iron oxide prelabeling. Reports have shown that neural stem cells (NSCs) may help mediate neuroprotection or stimulate neuroreparative responses in adult and neonatal models of ischemic injury. We investigated the ability of high-field MRI to monitor and noninvasively quantify the migration, proliferation, and location of iron oxide-labeled NSCs over very long time periods (58 weeks) in real time while contemporaneously correlating this activity with the evolving severity and extent of neural damage.

METHODS

Labeled clonal murine NSCs (mNSCs) were implanted 3 days after unilateral HII in 10-day-old rat pups into the contralateral striatum or ventricle. We developed methods for objectively quantifying key aspects of dynamic NSC behavior (eg, viability; extent, and speed of migration; degree of proliferation; extent of integration into host parenchyma). MRI images were validated with histological and immunohistochemical assessments.

RESULTS

mNSCs rapidly migrated (100 μm/day) to the lesion site. Chains of migrating NSCs were observed in the corpus callosum. In pups subjected to HII, though not in intact control animals, we observed a 273% increase in the MR-derived volume of mNSCs 4 weeks after implantation (correlating with the known proliferative behavior of endogenous and exogenous NSCs) that slowly declined over the 58-week time course, with no adverse consequences. Large numbers of now quiescent mNSCs remained at the site of injury, many retaining their iron oxide label.

INTERPRETATION

Our studies demonstrate that MRI can simultaneously monitor evolving neonatal cerebral injury as well as NSC migration and location. Most importantly, it can noninvasively monitor proliferation dynamically for prolonged time periods. To be able to pursue clinical trials in newborns using stem cell therapies it is axiomatic that safety be insured through the long-term real time monitoring of cell fate and activity, particularly with regard to observing unanticipated risks to the developing brain. This study supports the feasibility of reliably using MRI for this purpose.

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.

Cell-based therapy for stroke

Current treatments for stroke, such as the use of thrombolytic agents, are often limited by a narrow therapeutic time window. However, the regeneration of the brain after damage is still active days even weeks after stroke occurs, which might provide a second window for treatment. Cell-based therapy can be categorized into two strategies. One is transplantation of exogenous cells into the injured brain to replace the lost cells or support the remaining cells. The other strategy is to enhance the proliferation, differentiation, migration of endogenous stem or progenitor cells. Recent development in adult stem cell research and advancement in the induction of pluripotent stem cells from somatic adult cells provide a tremendous opportunity for transplantation therapy. Understanding the mechanisms and regulations involved in the endogenous neurogenesis will also help develop novel therapeutic interventions to promote neurogenesis and functional recovery in stroke. This review describes up-to-date progresses in cell-based therapy for the treatment of stroke.

Intravenous administration of mesenchymal stem cells exerts therapeutic effects on parkinsonian model of rats: focusing on neuroprotective effects of stromal cell-derived factor-1alpha

Background

Mesenchymal stem cells (MSCs) are pluripotent stem cells derived from bone marrow with secretory functions of various neurotrophic factors. Stromal cell-derived factor-1α (SDF-1α) is also reported as one of chemokines released from MSCs. In this research, the therapeutic effects of MSCs through SDF-1α were explored. 6-hydroxydopamine (6-OHDA, 20 μg) was injected into the right striatum of female SD rats with subsequent administration of GFP-labeled MSCs, fibroblasts, (i.v., 1 × 10⁷ cells, respectively) or PBS at 2 hours after 6-OHDA injection. All rats were evaluated behaviorally with cylinder test and amphetamine-induced rotation test for 1 month with consequent euthanasia for immunohistochemical evaluations. Additionally, to explore the underlying mechanisms, neuroprotective effects of SDF-1α were explored using 6-OHDA-exposed PC12 cells by using dopamine (DA) assay and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) staining.

Results

Rats receiving MSC transplantation significantly ameliorated behaviorally both in cylinder test and amphetamine-induced rotation test compared with the control groups. Correspondingly, rats with MSCs displayed significant preservation in the density of tyrosine hydroxylase (TH)-positive fibers in the striatum and the number of TH-positive neurons in the substantia nigra pars compacta (SNc) compared to that of control rats. In the in vitro study, SDF-1α treatment increased DA release and suppressed cell death induced by 6-OHDA administration compared with the control groups.

Conclusions

Consequently, MSC transplantation might exert neuroprotection on 6-OHDA-exposed dopaminergic neurons at least partly through anti-apoptotic effects of SDF-1α. The results demonstrate the potentials of intravenous MSC administration for clinical applications, although further explorations are required.

Effect of cell therapy on recovery of cognitive functions in rats during the delayed period after brain injury

We studied the effect of systemic transplantation of human stem cells from various tissues on cognitive functions of the brain in rats during the delayed period after experimental brain injury. Stem cells were shown to increase the efficacy of medical treatment with metabolic and symptomatic drugs for recovery of cognitive functions. They accelerated the formation of the conditioned defense response. Fetal neural stem cells had a stronger effect on some parameters of cognitive function 2 months after brain injury. The efficacy of bone marrow mesenchymal stem cells from adult humans or fetuses was higher 3 months after brain injury.

In vitro non-viral lipofectamine delivery of the gene for glial cell line-derived neurotrophic factor to human umbilical cord blood CD34+ cells

Using a lipofection technique, we explored a non-viral delivery of plasmid DNA encoding a rat pGDNF (glial cell line-derived neurotrophic factor) to CD34+ cells derived from human umbilical cord blood (HUCB) cells in order to obtain cells stably expressing the GDNF gene. The target gene GDNF was amplified from cortex cells of newborn Sprague-Dawley rats by reverse transcriptase polymerase chain reaction (RT-PCR) and inserted into vector pEGFP-N1 to construct the eukaryotic expression vector pEGFP/GDNF. The positive clones were identified by sequencing and endonuclease digestion. The expression of pEGFP/GDNF-transfected HUCB cells CD34+ was examined by ELISA. Single fragment of 640 bp was obtained after the rat GDNF cDNA was amplified by RT-PCR. Two fragments of about 4.3 kb and 640 pb were obtained after digestion of recombinant plasmid pEGFP/GDNF with XhoI/KpnI. The nucleic acid fragment of 640 bp was confirmed to agree well with the sequence of GDNF gene published by GenBank. The expression of GDNF mRNA and the level of GDNF from pEGFP/GDNF-transfected CD34+ cells were increased substantially, compared with pEGFP control plasmid transfected CD34+ cells (P<0.05). Moreover, co-culture of primary rat cells with the pEGFP/GDNF-transfected CD34+ cells promoted enhanced neuroprotection against oxygen-glucose deprivation induced cell dysfunctions. The present results support the use of the non-viral plasmid liposome for therapeutic gene expression for stem cell therapy.

Endothelial cells support survival, proliferation, and neuronal differentiation of transplanted adult ischemia-induced neural stem/progenitor cells after cerebral infarction

Transplantation of neural stem cells (NSCs) has been proposed as a therapy for a range of neurological disorders. To realize the potential of this approach, it is essential to control survival, proliferation, migration, and differentiation of NSCs after transplantation. NSCs are regulated in vivo, at least in part, by their specialized microenvironment or "niche." In the adult central nervous system, neurogenic regions, such as the subventricular and subgranular zones, include NSCs residing in a vascular niche with endothelial cells. Although there is accumulating evidence that endothelial cells promote proliferation of NSCs in vitro, there is no description of their impact on transplanted NSCs. In this study, we grafted cortex-derived stroke-induced neural stem/progenitor cells, obtained from adult mice, onto poststroke cortex in the presence or absence of endothelial cells, and compared survival, proliferation, and neuronal differentiation of the neural precursors in vivo. Cotransplantation of endothelial cells and neural stem/progenitor cells increased survival and proliferation of ischemia-induced neural stem/progenitor cells and also accelerated neuronal differentiation compared with transplantation of neural precursors alone. These data indicate that reconstitution of elements in the vascular niche enhances transplantation of adult neural progenitor cells.

Rescue of radiation-induced cognitive impairment through cranial transplantation of human embryonic stem cells

Cranial irradiation remains a frontline treatment for the control of tumor growth, and individuals surviving such treatments often manifest various degrees of cognitive dysfunction. Radiation-induced depletion of stem/precursor cell pools in the brain, particularly those residing in the neurogenic region of the hippocampus, is believed, in part, to be responsible for these often-unavoidable cognitive deficits. To explore the possibility of ameliorating radiation-induced cognitive impairment, athymic nude rats subjected to head only irradiation (10 Gy) were transplanted 2 days afterward with human embryonic stem cells (hESC) into the hippocampal formation and analyzed for stem cell survival, differentiation, and cognitive function. Animals receiving hESC transplantation exhibited superior performance on a hippocampal-dependent cognitive task 4 months postirradiation, compared to their irradiated surgical counterparts that did not receive hESCs. Significant stem cell survival was found at 1 and 4 months postirradiation, and transplanted cells showed robust migration to the subgranular zone throughout the dentate gyrus, exhibiting signs of neuron morphology within this neurogenic niche. These results demonstrate the capability to ameliorate radiation-induced normal tissue injury using hESCs, and suggest that such strategies may provide useful interventions for reducing the adverse effects of irradiation on cognition.

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.

Morphofunctional study of the therapeutic efficacy of human mesenchymal and neural stem cells in rats with diffuse brain injury

We studied the effect of transplantation of human stem cells from various tissues on reparative processes in the brain of rats with closed craniocerebral injury. Combined treatment with standard drugs and systemic administration of xenogeneic stem cells had a neuroprotective effect. The morphology of neurons rapidly returned to normal after administration of fetal neural stem cells. Fetal mesenchymal stem cells produced a prolonged effect on proliferative activity of progenitor cells in the subventricular zone of neurogenesis. Adult mesenchymal stem cells had a strong effect on recovery of the vascular bed in ischemic regions.