Effects of duplicate administration of human neural stem cell after focal cerebral ischemia in the rat

Stem Cell-Based Therapy for Experimental Ischemic Stroke: A Preclinical Systematic Review

Stem cell transplantation offers promise in the treatment of ischemic stroke. Here we utilized systematic review, meta-analysis, and meta-regression to study the biological effect of stem cell treatments in animal models of ischemic stroke. A total of 98 eligible publications were included by searching PubMed, EMBASE, and Web of Science from inception to August 1, 2020. There are about 141 comparisons, involving 5,200 animals, that examined the effect of stem cell transplantation on neurological function and infarct volume as primary outcome measures in animal models for stroke. Stem cell-based therapy can improve both neurological function (effect size, −3.37; 95% confidence interval, −3.83 to −2.90) and infarct volume (effect size, −11.37; 95% confidence interval, −12.89 to −9.85) compared with controls. These results suggest that stem cell therapy could improve neurological function deficits and infarct volume, exerting potential neuroprotective effect for experimental ischemic stroke, but further clinical studies are still needed.

Human placental mesenchymal stem cells improve stroke outcomes via extracellular vesicles-mediated preservation of cerebral blood flow

Background

Besides long-term trans-differentiation into neural cells, benefits of stem cell therapy (SCT) in ischemic stroke may include secretion of protective factors, which partly reflects extracellular vesicle (EVs) released by stem cell. However, the mechanism(s) by which stem cells/EVs limit stroke injury have yet to be fully defined.

Methods

We evaluated the protection effect of human placenta mesenchymal stem cells (hPMSC) as a potential form of SCT in experimental ischemic stroke ‘transient middle cerebral artery occusion (MCAO)/reperfusion’ mice model.

Findings

We found for the first time that intraperitoneal administration of hPMSCs or intravenous hPMSC-derived EVs, given at the time of reperfusion, significantly protected the ipsilateral hemisphere from ischemic injury. This protection was associated with significant restoration of normal blood flow to the post-MCAO brain. More importantly, EVs derived from hPMSC promote paracrine-based protection of SCT in the MCAO model in a cholesterol/lipid-dependent manner.

Interpretation

Together, our results demonstrated beneficial effects of hPMSC/EVs in experimental stroke models which could permit the rapid “translation” of these cells into clinical trials in the near-term.

Woo E, Patten A, Yau SY, Gil-Mohapel J. Beyond the Hippocampus and the SVZ: Adult Neurogenesis Throughout the Brain

Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.

Repeated injections of human umbilical cord blood-derived mesenchymal stem cells significantly promotes functional recovery in rabbits with spinal cord injury of two noncontinuous segments

Background

Spinal cord injuries (SCIs) are sustained by an increasing number of patients each year worldwide. The treatment of SCIs has long been a hard nut to crack for doctors around the world. Mesenchymal stem cells (MSCs) have shown benefits for the repair of SCI and recovery of function. Our present study aims to investigate the effects of intravenously infused human umbilical cord blood-derived MSCs (hUCB-MSCs) on functional recovery after subacute spinal cord compression injury of two noncontinuous segments. In addition, we compared the effects of single infusion and repeated intravenous (i.v.) injections on the recovery of spinal cord function.

Methods

A total of 43 adult rabbits were randomly divided into four groups: control, single injection (SI), repeated injection at a 3-day (3RI) or repeated injection at a 7-day interval (7RI) groups. Non-immunosuppressed rabbits in the transplantation groups were infused with either a single complete dose or three divided doses of 2 × 10⁶ hUCB-MSCs (3-day or 7-day intervals) on the first day post decompression. Behavioural scores and somatosensory evoked potentials (SEPs) were used to evaluate hindlimb functional recovery. The survival and differentiation of the transplanted human cells and the activation of the host glial and inflammatory reaction in the injured spinal cord were studied by immunohistochemical staining.

Results

Our results showed that hUCB-MSCs survived, proliferated, and primarily differentiated into oligodendrocytes in the injured area. Treatment with hUCB-MSCs reduced the extent of astrocytic activation, increased axonal preservation, potentially promoted axonal regeneration, decreased the number of Iba-1+ and TUNEL+ cells, increased the amplitude and decreased the onset latency of SEPs and significantly promoted functional improvement. However, these effects were more pronounced in the 3RI group compared with the SI and 7RI groups.

Conclusions

Our results suggest that treatment with i.v. injected hUCB-MSCs after subacute spinal cord compression injury of two noncontinuous segments can promote functional recovery through the differentiation of hUCB-MSCs into specific cell types and the enhancement of anti-inflammatory, anti-astrogliosis, anti-apoptotic and axonal preservation effects. Furthermore, the recovery was more pronounced in the rabbits repeatedly injected with cells at 3-day intervals. The results of this study may provide a novel and useful treatment strategy for the transplantation treatment of SCI.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0879-0) contains supplementary material, which is available to authorized users.

Effects of Antioxidant Supplements on the Survival and Differentiation of Stem Cells

Although physiological levels of reactive oxygen species (ROS) are required to maintain the self-renewal capacity of stem cells, elevated ROS levels can induce chromosomal aberrations, mitochondrial DNA damage, and defective stem cell differentiation. Over the past decade, several studies have shown that antioxidants can not only mitigate oxidative stress and improve stem cell survival but also affect the potency and differentiation of these cells. Further beneficial effects of antioxidants include increasing genomic stability, improving the adhesion of stem cells to culture media, and enabling researchers to manipulate stem cell proliferation by using different doses of antioxidants. These findings can have several clinical implications, such as improving neurogenesis in patients with stroke and neurodegenerative diseases, as well as improving the regeneration of infarcted myocardial tissue and the banking of spermatogonial stem cells. This article reviews the cellular and molecular effects of antioxidant supplementation to cultured or transplanted stem cells and draws up recommendations for further research in this area.

Mechanisms and Functional Significance of Stroke-Induced Neurogenesis

Stroke affects one in every six people worldwide, and is the leading cause of adult disability. After stroke, some limited spontaneous recovery occurs, the mechanisms of which remain largely unknown. Multiple, parallel approaches are being investigated to develop neuroprotective, reparative and regenerative strategies for the treatment of stroke. For years, clinical studies have tried to use exogenous cell therapy as a means of brain repair, with varying success. Since the rediscovery of adult neurogenesis and the identification of adult neural stem cells in the late nineties, one promising field of investigation is focused upon triggering and stimulating this self-repair system to replace the neurons lost following brain injury. For instance, it is has been demonstrated that the adult brain has the capacity to produce large numbers of new neurons in response to stroke. The purpose of this review is to provide an updated overview of stroke-induced adult neurogenesis, from a cellular and molecular perspective, to its impact on brain repair and functional recovery.

A human neural stem cell line provides neuroprotection and improves neurological performance by early intervention of neuroinflammatory system

A human neural stem cell line, HB1.F3, demonstrated neuroprotective properties in cerebral ischemia animal models. In this study, we have investigated about the mechanisms of such neuroprotection, mainly focusing on the neuroinflammatory system at an earlier time point of the pathology. Cerebral ischemia model was generated by middle cerebral artery occlusion (MCAO) in adult male Wister rats. HB1.F3 cells were transplanted through jugular vein 6h after MCAO. Forty eight hours after MCAO, transplanted rats showed better neurological performance and decreased TUNEL positive apoptotic cell number in the penumbra. However, haematoxylin and eosin staining and immunostaining showed that, HB1.F3 cells did not affect the necrotic cell death. Twenty four hours after MCAO (18h after HB1.F3 transplantation), infiltrated granulocytes and macrophage/microglia number in the core regions were decreased compared to PBS-treated controls. Immunohistochemical analysis further demonstrated that the transplantation decreased inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 expressing cell number in the core and penumbra, respectively. Double immunofluorescence results revealed that iNOS was mainly expressed in granulocytes and macrophage/microglia in the core region, and COX-2 mainly expressed in neurons, endothelial cells and granulocytes in penumbra. Further analysis showed that although the percentage of iNOS expressing granulocytes and macrophage/microglia was not decreased, COX-2 expressing neurons and vessel number was decreased by the transplantation. In vitro mRNA analysis showed that brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (βFGF) and bone morphogenic protein (BMP)-4 expression was high in cultured HB1.F3 cells. Thus, our results demonstrated that HB1.F3 cell transplantation provide neuroprotection possibly through the regulation of early inflammatory events in the cerebral ischemia condition.

Effects of Tetramethylpyrazine on Functional Recovery and Neuronal Dendritic Plasticity after Experimental Stroke

The 2,3,5,6-tetramethylpyrazine (TMP) has been widely used in the treatment of ischemic stroke by Chinese doctors. Here, we report the effects of TMP on functional recovery and dendritic plasticity after ischemic stroke. A classical model of middle cerebral artery occlusion (MCAO) was established in this study. The rats were assigned into 3 groups: sham group (sham operated rats treated with saline), model group (MCAO rats treated with saline) and TMP group (MCAO rats treated with 20 mg/kg/d TMP). The neurological function test of animals was evaluated using the modified neurological severity score (mNSS) at 3 d, 7 d, and 14 d after MCAO. Animals were euthanized for immunohistochemical labeling to measure MAP-2 levels in the peri-infarct area. Golgi-Cox staining was performed to test effect of TMP on dendritic plasticity at 14 d after MCAO. TMP significantly improved neurological function at 7 d and 14 d after ischemia, increased MAP-2 level at 14 d after ischemia, and enhanced spine density of basilar dendrites. TMP failed to affect the spine density of apical dendrites and the total dendritic length. Data analyses indicate that there was significant negative correlation between mNSS and plasticity measured at 14 d after MCAO. Thus, enhanced dendritic plasticity contributes to TMP-elicited functional recovery after ischemic stroke.

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.

The protective effect of melatonin on neural stem cell against LPS-induced inflammation

Stem cell therapy for tissue regeneration has several limitations in the fact that transplanted cells could not survive for a long time. For solving these limitations, many studies have focused on the antioxidants to increase survival rate of neural stem cells (NSCs). Melatonin, an antioxidant synthesized in the pineal gland, plays multiple roles in various physiological mechanisms. Melatonin exerts neuroprotective effects in the central nervous system. To determine the effect of melatonin on NSCs which is in LPS-induced inflammatory stress state, we first investigated nitric oxide (NO) production and cytotoxicity using Griess reagent assays, LDH assay, and neurosphere counting. Also, we investigated the effect of melatonin on NSCs by measuring the mRNA levels of SOX2, TLX, and FGFR-2. In addition, western blot analyses were performed to examine the activation of PI3K/Akt/Nrf2 signaling in LPS-treated NSCs. In the present study, we suggested that melatonin inhibits NO production and protects NSCs against LPS-induced inflammatory stress. In addition, melatonin promoted the expression of SOX2 and activated the PI3K/Akt/Nrf2 signaling under LPS-induced inflammation condition. Based on our results, we conclude that melatonin may be an important factor for the survival and proliferation of NSCs in neuroinflammatory diseases.

Effects of acute versus post-acute systemic delivery of neural progenitor cells on neurological recovery and brain remodeling after focal cerebral ischemia in mice

Intravenous transplantation of neural progenitor cells (NPCs) induces functional recovery after stroke, albeit grafted cells are not integrated into residing neural networks. However, a systematic analysis of intravenous NPC delivery at acute and post-acute time points and their long-term consequences does not exist. Male C57BL6 mice were exposed to cerebral ischemia, and NPCs were intravenously grafted on day 0, on day 1 or on day 28. Animals were allowed to survive for up to 84 days. Mice and tissues were used for immunohistochemical analysis, flow cytometry, ELISA and behavioral tests. Density of grafted NPCs within the ischemic hemisphere was increased when cells were transplanted on day 28 as compared with transplantation on days 0 or 1. Likewise, transplantation on day 28 yielded enhanced neuronal differentiation rates of grafted cells. Post-ischemic brain injury, however, was only reduced when NPCs were grafted at acute time points. On the contrary, reduced post-ischemic functional deficits due to NPC delivery were independent of transplantation paradigms. NPC-induced neuroprotection after acute cell delivery was due to stabilization of the blood–brain barrier (BBB), reduction in microglial activation and modulation of both peripheral and central immune responses. On the other hand, post-acute NPC transplantation stimulated post-ischemic regeneration via enhanced angioneurogenesis and increased axonal plasticity. Acute NPC delivery yields long-term neuroprotection via enhanced BBB integrity and modulation of post-ischemic immune responses, whereas post-acute NPC delivery increases post-ischemic angioneurogenesis and axonal plasticity. Post-ischemic functional recovery, however, is independent of NPC delivery timing, which offers a broad therapeutic time window for stroke treatment.

Stem cell therapy for acute cerebral injury: what do we know and what will the future bring?

PURPOSE OF REVIEW

The central nervous system has limited capacity for regeneration after acute and chronic injury. An attractive approach to stimulate neural plasticity in the brain is to transplant stem cells in order to restore function. Here, we discuss potential mechanisms of action, current knowledge and future perspectives of clinical stem cell research for stroke and traumatic brain injury.

RECENT FINDINGS

Preclinical data using various models suggest stem cell therapy to be a promising therapeutic avenue. Progress has been made in elucidating the mechanism of action of various cell types used, shifting the hypothesis from neural replacement to enhancing endogenous repair processes. Translation of these findings in clinical trials is currently being pursued with emphasis on both safety as well as efficacy.

SUMMARY

Clinical trials are currently recruiting patients in phase I and II trials to gain more insight in the therapeutic potential of stem cells in acute cerebral injury. A close interplay between results of these clinical trials and more extensive basic research is essential for future trial design, choosing the optimal transplantation strategy and selecting the right patients.

Concise review: Preclinical studies on human cell-based therapy in rodent ischemic stroke models: where are we now after a decade?

Stroke, a debilitating brain insult, afflicts millions of individuals globally each year. In the last decade, researchers have investigated cell-based therapy as an alternative strategy to improve neurological outcome following stroke. This concise review critically examines preclinical reports using human adult and fetal stem/progenitor cells in rodent models of ischemic stroke. As we enter the second decade of study, we should aim to optimize our collective likelihood to translational success for stroke victims worldwide. We advocate international consensus recommendations be developed for future preclinical research.

Brain repair: cell therapy in stroke

Stroke affects one in every six people worldwide, and is the leading cause of adult disability. Some spontaneous recovery is usual but of limited extent, and the mechanisms of late recovery are not completely understood. Endogenous neurogenesis in humans is thought to contribute to repair, but its extent is unknown. Exogenous cell therapy is promising as a means of augmenting brain repair, with evidence in animal stroke models of cell migration, survival, and differentiation, enhanced endogenous angiogenesis and neurogenesis, immunomodulation, and the secretion of trophic factors by stem cells from a variety of sources, but the potential mechanisms of action are incompletely understood. In the animal models of stroke, both mesenchymal stem cells (MSCs) and neural stem cells (NSCs) improve functional recovery, and MSCs reduce the infarct volume when administered acutely, but the heterogeneity in the choice of assessment scales, publication bias, and the possible confounding effects of immunosuppressants make the comparison of effects across cell types difficult. The use of adult-derived cells avoids the ethical issues around embryonic cells but may have more restricted differentiation potential. The use of autologous cells avoids rejection risk, but the sources are restricted, and culture expansion may be necessary, delaying treatment. Allogeneic cells offer controlled cell numbers and immediate availability, which may have advantages for acute treatment. Early clinical trials of both NSCs and MSCs are ongoing, and clinical safety data are emerging from limited numbers of selected patients. Ongoing research to identify prognostic imaging markers may help to improve patient selection, and the novel imaging techniques may identify biomarkers of recovery and the mechanism of action for cell therapies.

Long-term effects of magnetically targeted ferumoxide-labeled human neural stem cells in focal cerebral ischemia

The long-term effect of magnetically targeted neural stem cells in a rat focal cerebral ischemia model was investigated. In middle cerebral artery occlusion (MCAO) stroke model rats, ferumoxide-labeled human neural stem cells (hNSCs) were injected into the tail vein. MCAO rats were divided into three groups: ischemia only (IO), ischemia with NSC injection (IC), and ischemia with NSC injection and the use of magnet targeting (IM). Four weeks after MCAO and 3 weeks posttransplantation, a greater number of hNSCs were found in ischemic lesion sites in IM rat brain compared with IO and IC animals. In addition, differentiation of hNSCs into neurons or astrocytes and angiogenesis were markedly increased. In IM rats, infarct volume was considerably reduced, and function was significantly improved. The present study indicates that long-term use of magnetic fields may be a useful way to improve the efficacy of targeted migration of stem cells and functional deficits in stem cell-based therapy for ischemic brain injury.

Method parameters' impact on mortality and variability in rat stroke experiments: a meta-analysis

Background

Even though more than 600 stroke treatments have been shown effective in preclinical studies, clinically proven treatment alternatives for cerebral infarction remain scarce. Amongst the reasons for the discrepancy may be methodological shortcomings, such as high mortality and outcome variability, in the preclinical studies. A common approach in animal stroke experiments is that A) focal cerebral ischemia is inflicted, B) some type of treatment is administered and C) the infarct sizes are assessed. However, within this paradigm, the researcher has to make numerous methodological decisions, including choosing rat strain and type of surgical procedure. Even though a few studies have attempted to address the questions experimentally, a lack of consensus regarding the optimal methodology remains.

Methods

We therefore meta-analyzed data from 502 control groups described in 346 articles to find out how rat strain, procedure for causing focal cerebral ischemia and the type of filament coating affected mortality and infarct size variability.

Results

The Wistar strain and intraluminal filament procedure using a silicone coated filament was found optimal in lowering infarct size variability. The direct and endothelin methods rendered lower mortality rate, whereas the embolus method increased it compared to the filament method.

Conclusions

The current article provides means for researchers to adjust their middle cerebral artery occlusion (MCAo) protocols to minimize infarct size variability and mortality.