Transplantation of Bone Marrow-Derived Stem Cells: A Promising Therapy for Stroke

An update on stem cell therapy for stroke patients: Where are we now?

With a foundation built upon initial work from the 1980s demonstrating graft viability in cerebral ischemia, stem cell transplantation has shown immense promise in promoting survival, enhancing neuroprotection and inducing neuroregeneration, while mitigating both histological and behavioral deficits that frequently accompany ischemic stroke. These findings have led to a number of clinical trials that have thoroughly supported a strong safety profile for stem cell therapy in patients but have generated variable efficacy. As preclinical evidence continues to expand through the investigation of new cell lines and optimization of stem cell delivery, it remains critical for translational models to adhere to the protocols established through basic scientific research. With the recent shift in approach towards utilization of stem cells as a conjunctive therapy alongside standard thrombolytic treatments, key issues including timing, route of administration, and stem cell type must each be appropriately translated from the laboratory in order to resolve the question of stem cell efficacy for cerebral ischemia that ultimately will enhance therapeutics for stroke patients towards improving quality of life.

Stem Cell Transplantation Therapy and Neurological Disorders: Current Status and Future Perspectives

Neurodegenerative diseases are a global health issue with inadequate therapeutic options and an inability to restore the damaged nervous system. With advances in technology, health scientists continue to identify new approaches to the treatment of neurodegenerative diseases. Lost or injured neurons and glial cells can lead to the development of several neurological diseases, including Parkinson's disease, stroke, and multiple sclerosis. In recent years, neurons and glial cells have successfully been generated from stem cells in the laboratory utilizing cell culture technologies, fueling efforts to develop stem cell-based transplantation therapies for human patients. When a stem cell divides, each new cell has the potential to either remain a stem cell or differentiate into a germ cell with specialized characteristics, such as muscle cells, red blood cells, or brain cells. Although several obstacles remain before stem cells can be used for clinical applications, including some potential disadvantages that must be overcome, this cellular development represents a potential pathway through which patients may eventually achieve the ability to live more normal lives. In this review, we summarize the stem cell-based therapies that have been explored for various neurological disorders, discuss the potential advantages and drawbacks of these therapies, and examine future directions for this field.

Stem cell, Granulocyte-Colony Stimulating Factor and/or Dihexa to promote limb function recovery in a rat sciatic nerve damage-repair model: Experimental animal studies

Background

Optimizing nerve regeneration and re-innervation of target muscle/s is the key for improved functional recovery following peripheral nerve damage. We investigated whether administration of mesenchymal stem cell (MSC), Granulocyte-Colony Stimulating Factor (G-CSF) and/or Dihexa can improve recovery of limb function following peripheral nerve damage in rat sciatic nerve transection-repair model.

Materials and methods

There were 10 experimental groups (n = 6–8 rats/group). Bone marrow derived syngeneic MSCs (2 × 10⁶; passage≤6), G-CSF (200–400 μg/kg b.wt.), Dihexa (2–4 mg/kg b.wt.) and/or Vehicle were administered to male Lewis rats locally via hydrogel at the site of nerve repair, systemically (i.v./i.p), and/or to gastrocnemius muscle. The limb sensory and motor functions were assessed at 1–2 week intervals post nerve repair until the study endpoint (16 weeks).

Results

The sensory function in all nerve boundaries (peroneal, tibial, sural) returned to nearly normal by 8 weeks (Grade 2.7 on a scale of Grade 0–3 [0 = No function; 3 = Normal function]) in all groups combined. The peroneal nerve function recovered quickly with return of function at one week (∼2.0) while sural nerve function recovered rather slowly at four weeks (∼1.0). Motor function at 8–16 weeks post-nerve repair as determined by walking foot print grades significantly (P < 0.05) improved with MSC + G-CSF or MSC + Dihexa administrations into gastrocnemius muscle and mitigated foot flexion contractures.

Conclusions

These findings demonstrate MSC, G-CSF and Dihexa are promising candidates for adjunct therapies to promote limb functional recovery after surgical nerve repair, and have implications in peripheral nerve injury and limb transplantation. IACUC No.215064.

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G-CSF in combination with MSCs improved limb function recovery in sciatic nerve transection- repair model.

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Dihexa in combination with MSC improved limb function recovery in sciatic nerve transection- repair model.

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Foot flexion contractures were reduced with G-CSF & MSC or Dihexa & MSC administration into target muscle gastrocnemius.

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MSC, G-CSF or Dihexa combination therapy is attractive, feasible & promising in peripheral nerve injury repair and have implications in limb transplantation.

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The findings warrant further investigation to understand the cellular/molecular mechanisms.

Bone Marrow-Derived NCS-01 Cells Advance a Novel Cell-Based Therapy for Stroke

Human mesenchymal stem cells have been explored for their application in cell-based therapies targeting stroke. Identifying cell lines that stand as safe, accessible, and effective for transplantation, while optimizing dosage, timing, and method of delivery remain critical translational steps towards clinical trials. Preclinical studies using bone marrow-derived NCS-01 cells show the cells' ability to confer functional recovery in ischemic stroke. Coculturing primary rat cortical cells or human neural progenitor cells with NCS-01 cells protects against oxygen-glucose deprivation. In the rodent middle cerebral artery occlusion model, intracarotid artery administration of NCS-01 cells demonstrate greater efficacy than other mesenchymal stem cells (MSCs) at improving motor and neurological function, as well as reducing infarct volume and peri-infarct cell loss. NCS-01 cells secrete therapeutic factors, including basic fibroblast growth factor and interleukin-6, while also demonstrating a potentially novel mechanism of extending filopodia towards the site of injury. In this review, we discuss recent preclinical advancements using in vitro and in vivo ischemia models that support the transplantation of NCS-01 in human stroke trials. These results, coupled with the recommendations put forth by the consortium of Stem cell Therapeutics as an Emerging Paradigm for Stroke (STEPS), highlight a framework for conducting preclinical research with the ultimate goal of initiating clinical trials.

Drug-like delivery methods of stem cells as biologics for stroke

Introduction: Stem cell therapy is an experimental treatment for brain disorders. Although a cellular product, stem cells can be classified as biologics based on the cells' secretion of therapeutic substances. Treatment with stem cell biologics may appeal to stroke because of the secondary cell death mechanisms, especially neuroinflammation, that are rampant from the onset and remain elevated during the progressive phase of the disease requiring multi-pronged biological targets to effectively abrogate the neurodegenerative pathology. However, the optimal delivery methods, among other logistical approaches (i.e. cell doses and timing of intervention), for stem cell therapy will need to be refined before stem cell biologics can be successfully utilized for stroke in large scale clinical trials. Areas covered: In this review, we discuss how the innate qualities of stem cells characterize them as biologics, how stem cell transplantation may be an ideal treatment for stroke, and the various routes of stem cell administration that have been employed in various preclinical and clinical investigations. Expert opinion: There is a need to optimize the delivery of stem cell biologics for stroke in order to guide the safe and effective translation of this therapy from the laboratory to the clinic.

Concise Review: Stem Cell Therapy for Stroke Patients: Are We There Yet?

Four decades of preclinical research demonstrating survival, functional integration, and behavioral effects of transplanted stem cells in experimental stroke models have provided ample scientific basis for initiating limited clinical trials of stem cell therapy in stroke patients. Although safety of the grafted cells has been overwhelmingly documented, efficacy has not been forthcoming. Two recently concluded stroke clinical trials on mesenchymal stem cells (MSCs) highlight the importance of strict adherence to the basic science findings of optimal transplant regimen of cell dose, timing, and route of delivery in enhancing the functional outcomes of cell therapy. Echoing the Stem Cell Therapeutics as an Emerging Paradigm for Stroke and Stroke Treatment Academic Industry Roundtable call for an NIH‐guided collaborative consortium of multiple laboratories in testing the safety and efficacy of stem cells and their derivatives, not just as stand‐alone but preferably in combination with approved thrombolytic or thrombectomy, may further increase the likelihood of successful fruition of translating stem cell therapy for stroke clinical application. The laboratory and clinical experience with MSC therapy for stroke may guide the future translational research on stem cell‐based regenerative medicine in neurological disorders. stem cells translational medicine2019;8:983&988

"Stem cell therapy to promote limb function recovery in peripheral nerve damage in a rat model" - Experimental research

Background

Optimizing nerve regeneration and mitigating muscle atrophy are the keys to successful outcomes in peripheral nerve damage. We investigated whether mesenchymal stem cell (MSC) therapy can improve limb function recovery in peripheral nerve damage.

Materials and methods

We used sciatic nerve transection/repair (SNR) and individual nerve transection/repair (INR; branches of sciatic nerve - tibial, peroneal, sural) models to study the effect of MSCs on proximal and distal peripheral nerve damages, respectively, in male Lewis rats. Syngeneic MSCs (5 × 10⁶; passage≤6) or saline were administered locally and intravenously. Sensory/motor functions (SF/MF) of the limb were assessed.

Results

Rat MSCs (>90%) were CD29⁺, CD90⁺, CD34⁻, CD31⁻ and multipotent. Total SF at two weeks post-SNR & INR with or without MSC therapy was ∼1.2 on a 0–3 grading scale (0 = No function; 3 = Normal); by 12 weeks it was 2.6–2.8 in all groups (n ≥ 9/group). MSCs accelerated SF onset. At eight weeks post-INR, sciatic function index (SFI), a measure of MF (0 = Normal; −100 = Nonfunctional) was −34 and −77 in MSC and vehicle groups, respectively (n ≥ 9); post-SNR it was −72 and −92 in MSC and vehicle groups, respectively. Long-term MF (24 weeks) was apparent in MSC treated INR (SFI -63) but not in SNR (SFI -100). Gastrocnemius muscle atrophy was significantly reduced (P < 0.05) in INR. Nerve histomorphometry revealed reduced axonal area (P < 0.01) but no difference in myelination (P > 0.05) in MSC treated INR compared to the naive contralateral nerve.

Conclusion

MSC therapy in peripheral nerve damage appears to improve nerve regeneration, mitigate flexion-contractures, and promote limb functional recovery.

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Mesenchymal stem cell (MSC) therapy improved limb functional recovery.

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MSCs improved nerve regeneration and mitigated foot flexion-contractures.

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Limb muscle atrophy was significantly reduced in individual nerve repair (INR).

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Functional recovery in distal nerve repair (INR) was superior to proximal (SNR).

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MSC therapy is attractive, feasible & promising in peripheral nerve injury repair.

Exposing mesenchymal stem cells to chondroitin sulphated proteoglycans reduces their angiogenic and neuro-adhesive paracrine activity

The multifactorial complexity of spinal cord injuries includes the formation of a glial scar, of which chondroitin sulphated proteoglycans (CSPG) are an integral component. Previous studies have shown CSPG to have inhibitory effects on endothelial and neuronal cell growth, highlighting the difficulty of spinal cord regeneration. Mesenchymal stem/stromal cells (MSC) are widely used as a cell therapy, and there is mounting evidence for their angiogenic and neurotrophic paracrine properties. However, in vivo studies have observed poor engraftment and survival of MSC when injected into SCI. Currently, it is not known whether increasing CSPG concentrations seen after SCI may affect MSC; therefore we have investigated the effects of CSPG exposure to MSC in vitro. CSPG-mediated inhibition of MSC adhesion was observed when MSC were cultured on substrates of increasing CSPG concentration, however MSC viability was not affected even up to five days of culture. Culture conditioned medium harvested from these cultures (primed MSC CM) was used as both culture substrata and soluble medium for EA.hy926 endothelial cells and SH-SY5Y neuronal cells. MSC CM was angiogenic, promoting endothelial cell adhesion, proliferation and tubule formation. However, exposing MSC to CSPG reduced the effects of CSPG-primed MSC CM on endothelial cell adhesion and proliferation, but did not reduce MSC-induced endothelial tubule formation. Primed MSC CM also promoted neuronal cell adhesion, which was reduced following exposure to CSPG. There were no marked differences in neurite outgrowth in MSC CM from CSPG primed MSC cultures versus control conditions, although non-primed MSC CM from the same donors was found to significantly enhance neurite outgrowth. Taken together, these studies demonstrate that MSC are resilient to CSPG exposure, but that there is a marked effect of CSPG on their paracrine regenerative activity. The findings increase our understanding of how the wound microenvironment after SCI can mitigate the beneficial effects of MSC transplantation.

New prospects of mesenchymal stem cells for ameliorating temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is present in 30% of epileptic patients and does not respond to conventional treatments. Bone marrow derived mesenchymal stem cells (BMSCs) induce endogenous neural stem cells, inhibit neurodegeneration, and promote brain self-repair mechanisms. The present study addresses the feasibility of BMSCs transplantation against pilocarpine-induced TLE experimentally. BMSCs were injected either intravenously (IV) or in hippocampus bilaterally (IC). Increased cell count of BMSCs was achieved via IC route. BMSCs treatment ameliorated the pilocarpine-induced neurochemical and histological changes, retained amino acid neurotransmitters to the normal level, downregulated the immunoreactivity to insulin growth factor-1 receptor, synaptophysin, and caspase-3 and reduced oxidative insult and inflammatory markers detected in epileptic model. It is worth noting that BMSCs IC-administered showed more pronounced effects than those administered via IV route. BMSCs transplantation presents a promise for TLE treatment that has to be elucidated clinically.

Stem cell therapy for abrogating stroke-induced neuroinflammation and relevant secondary cell death mechanisms

Ischemic stroke is a leading cause of death worldwide. A key secondary cell death mechanism mediating neurological damage following the initial episode of ischemic stroke is the upregulation of endogenous neuroinflammatory processes to levels that destroy hypoxic tissue local to the area of insult, induce apoptosis, and initiate a feedback loop of inflammatory cascades that can expand the region of damage. Stem cell therapy has emerged as an experimental treatment for stroke, and accumulating evidence supports the therapeutic efficacy of stem cells to abrogate stroke-induced inflammation. In this review, we investigate clinically relevant stem cell types, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs), very small embryonic-like stem cells (VSELs), neural stem cells (NSCs), extraembryonic stem cells, adipose tissue-derived stem cells, breast milk-derived stem cells, menstrual blood-derived stem cells, dental tissue-derived stem cells, induced pluripotent stem cells (iPSCs), teratocarcinoma-derived Ntera2/D1 neuron-like cells (NT2N), c-mycER(TAM) modified NSCs (CTX0E03), and notch-transfected mesenchymal stromal cells (SB623), comparing their potential efficacy to sequester stroke-induced neuroinflammation and their feasibility as translational clinical cell sources. To this end, we highlight that MSCs, with a proven track record of safety and efficacy as a transplantable cell for hematologic diseases, stand as an attractive cell type that confers superior anti-inflammatory effects in stroke both in vitro and in vivo. That stem cells can mount a robust anti-inflammatory action against stroke complements the regenerative processes of cell replacement and neurotrophic factor secretion conventionally ascribed to cell-based therapy in neurological disorders.

Intravenously Administered Bone Marrow Cells Migrate to Damaged Brain Tissue and Improve Neural Function in Ischemic Rats

Accumulated evidence suggests that bone marrow stromal cells (BMSCs) are capable of regenerating damaged tissue. This study evaluated whether intravenously (noninvasively) administered, GFP-labeled BMSCs would migrate into damaged brain tissue and improve neurological function after a stroke. Wistar rats were subjected to middle cerebral artery occlusion and reperfusion. Twenty-four hours after injury, the rats received an IV injection of culture medium or BMSCs isolated from adult Wistar rats expressing green fluorescent protein (GFP). Two hours after injury and 1, 3, and 7 days after cell transplantation, neurological function was evaluated using a neurological severity scale. On day 7, the brain scar size was determined using tetrazolium chloride staining, and the implanted cells were identified using confocal microscopy. Immunohistochemistry was used to evaluate apoptosis and angiogenesis in the ischemic region, as well as the spatial distribution of the implanted BMSCs relative to the native neural cells. Implanted BMSCs migrated throughout the territory of the middle cerebral artery by 7 days after transplantation. Most implanted cells were located in the scar area and border zone of the ischemic region, and some expressed the neuronal marker NeuN. Rats receiving BMSC transplantation exhibited reduced scar size, limited apoptosis, and enhanced angiogenic factor expression and vascular density in the ischemic region relative to the control group, as well as significant improvements in the neurological severity scores. Intravenously administrated BMSCs facilitated the structural and functional recovery of neural tissue following ischemic injury, perhaps mediated by enhanced angiogenesis.

Combining Injectable Plasma Scaffold with Mesenchymal Stem/Stromal Cells for Repairing Infarct Cavity after Ischemic Stroke

Stroke survivors are typically left with structural brain damage and associated functional impairment in the chronic phase of injury, for which few therapeutic options exist. We reported previously that transplantation of human embryonic stem cell (hESC)-derived neural stem cells together with Matrigel scaffolding into the brains of rats after focal ischemia reduced infarct volume and improved neurobehavioral performance. Matrigel is a gelatinous protein mixture extracted from mouse sarcoma cells, thus would not be approved for use as a scaffold clinically. In this study, we generated a gel-like scaffold from plasma that was controlled by changing the concentration of CaCl₂. In vitro study confirmed that 10-20 mM CaCl₂ and 10-40% plasma did not affect the viability and proliferation of human and rat bone marrow mesenchymal stem/stromal cells (BMSCs) and neural stem cells (NSCs). We transplanted plasma scaffold in combination of BMSCs into the cystic cavity after focal cerebral ischemia, and found that the atrophy volume was dramatically reduced and motor function was significantly improved in the group transplanted with scaffold/BMSCs compared with the groups treated with vehicle, scaffold or BMSCs only. Our data suggest that plasma-derived scaffold in combination of BMSCs is feasible for tissue engineering approach for the stroke treatment.

Recent Advances in Stem Cell-Based Therapeutics for Stroke

Regenerative medicine for central nervous system disorders, including stroke, has challenged the non-regenerative capacity of the brain. Among the many treatment strategies tailored towards repairing the injured brain, stem cell-based therapeutics have been demonstrated as safe and effective in animal models of stroke, and are being tested in limited clinical trials. We address here key lab-to-clinic translational research that relate to efficacy, safety, and mechanism of action underlying stem cell therapy. Recognizing the multi-pronged cell death processes associated with stroke that will likely require combination therapies, we next discuss potent drugs and novel technologies directed at improving the functional outcomes of stem cell-based therapeutics. We also examine discrepant transplant regimens between preclinical studies and clinical trials, as well as missing appropriate control arm (i.e., stroke subjects undergoing rehabilitation) on which to directly compare the therapeutic benefits of cell therapy. Finally, the bioethics of cell therapy is presented in order to assess its prevailing social status. With preliminary results now being reported from on-going clinical trials of stem cell therapy for stroke, a careful assessment of the true functional benefits of this novel treatment will further direct the future of regenerative medicine for neurological disorders.

Characterization of Insulin-Secreting Porcine Bone Marrow Stromal Cells Ex Vivo and Autologous Cell Therapy in Vivo

Cell therapy could potentially meet the need for pancreas and islet transplantations in diabetes mellitus that far exceeds the number of available donors. Bone marrow stromal cells are widely used in clinical trials mainly for their immunomodulatory effects with a record of safety. However, less focus has been paid to developing these cells for insulin secretion by transfection. Although murine models of diabetes have been extensively used in gene and cell therapy research, few studies have shown efficacy in large preclinical animal models. Here we report optimized conditions for ex vivo expansion and characterization of porcine bone marrow stromal cells and their permissive expression of a transfected insulin gene. Our data show that these cells resemble human bone marrow stromal cells in surface antigen expression, are homogeneous, and can be reproducibly isolated from outbred Yorkshire–Landrace pigs. Porcine bone marrow stromal cells were efficiently expanded in vitro to >1010 cells from 20 ml of bone marrow and remained karyotypically normal during expansion. These cells were electroporated with an insulin expression plasmid vector with high efficiency and viability, and secreted human insulin and C-peptide indicating appropriate processing of proinsulin. We showed that autologous insulin-secreting bone marrow stromal cells implanted and engrafted in the liver of a streptozotocin-diabetic pig that modeled type 1 diabetes resulted in partial, but significant, improvement in hyperglycemia that could not be ascribed to regeneration of endogenous β-cells. Glucose-stimulated insulin secretion in vivo from implanted cells in the treated pig was documented by a rise in serum human C-peptide levels during intravenous glucose tolerance tests. Compared to a sham-treated control pig, this resulted in significantly reduced fasting hyperglycemia, a slower rise in serum fructosamine, and prevented weight loss. Taken together, this study suggests that bone marrow stromal cells merit further development as autologous cell therapy for diabetes.

Therapeutic potential of hepatocyte growth factor against cerebral ischemia (Review)

The effective treatment for cerebral ischemia has not yet been established. Hepatocyte growth factor (HGF) is a potent pleiotropic cytokine that is involved in cell and tissue regeneration, including in the central nervous system. Studies have demonstrated that an exogenous administration of HGF protects brain tissue from ischemic damage. In response to binding to the receptor c-Met, HGF activates the downstream signaling pathways (including the phosphatidylinositol 3-kinase/Akt, Ras/MAPK and signal transducer and activator of transcription pathways) which leads to various cellular responses involved in angiogenesis, glial scar formation, anti-apoptosis and neurogenesis. The purpose of this review is to summarize the present understanding of the therapeutic potential of HGF in cerebral ischemia.

Bone marrow stromal cells as a therapeutic treatment for ischemic stroke

Cerebral ischemia remains the most frequent cause of death and quality-of-life impairments due to neurological deficits, and accounts for the majority of total healthcare costs. However, treatments for cerebral ischemia are limited. Over the last decade, bone marrow stromal cell (BMSC) therapy has emerged as a particularly appealing option, as it is possible to help patients even when initiated days or even weeks after the ischemic insult. BMSCs are a class of multipotent, self-renewing cells that give rise to differentiated progeny when implanted into appropriate tissues. Therapeutic effects of BMSC treatment for ischemic stroke, including sensory and motor recovery, have been reported in pre-clinical studies and clinical trials. In this article, we review the recent progress in BMSC-based therapy for ischemic stroke, focusing on the route of delivery and pre-processing of BMSCs. Selecting an optimal delivery route is of particular importance. The ideal approach, as well as the least risky, for translational applications still requires further identification. Appropriate preprocessing of BMSCs or combination therapy has the benefit of achieving the maximum possible restoration. Further pre-clinical studies are required to determine the time-window for transplantation and the appropriate dosage of cells.

Oligodendrocytes engineered with migratory proteins as effective graft source for cell transplantation in multiple sclerosis

Multiple sclerosis (MS) is characterized by widespread immunomodulatory demyelination of the CNS resulting in nerve cell dysfunction. Accordingly, treatment strategies have been centered on immunodulation and remyelination, with the former primarily focused on reducing the pathology rather than enhancing myelin repair which the latter targets. While conceding to the emerging view of heterogeneity in the pathology of MS, which precludes variations in degree of immune response (i.e., inflammation) and demyelination, the concept of enhancing myelin repair is appealing since it is likely to provide both disease-reducing and disease-inhibiting therapeutic approach to MS. In this regard, we and several others, have proposed that cell replacement therapy is an effective strategy to repair the myelin in MS. Here, we hypothesize that transplantation of mouse bone marrow-derived oligodendrocytes (BMDOs) and BMDOs transfected with Ephrin proteins (BMDO+Ephrin), which are known to enhance cell and axonal migratory capacity, may produce therapeutic benefits in animal models of MS.

Restoration of Intracortical and Thalamocortical Circuits after Transplantation of Bone Marrow Mesenchymal Stem Cells into the Ischemic Brain of Mice

Transplantation of bone marrow mesenchymal stem cells (BMSCs) provides a promising regenerative medicine for stroke. Whether BMSC therapy could repair ischemia-damaged neuronal circuits and recover electrophysiological activity has largely been unknown. To address this issue, BMSCs were implanted into the ischemic barrel cortex of adult mice 1 and 7 days after focal barrel cortex stroke. Two days after the first transplantation (3 days after stroke), the infarct volume determined by TTC staining was significantly smaller in BMSC-treated compared to vehicle-treated stroke mice. The behavioral corner test showed better long-term recovery of sensorimotor function in BMSC-treated mice. Six weeks poststroke, thalamocortical slices were prepared and neuronal circuit activity in the peri-infarct region of the barrel cortex was determined by extracellular recordings of evoked field potentials. In BMSC-transplanted brain slices, the ischemia-disrupted intracortical activity from layer 4 to layer 2/3 was noticeably recovered, and the thalamocortical circuit connection was also partially restored. In contrast, much less and slower recovery was seen in control animals of barrel cortex stroke. Immunohistochemical staining disclosed that the density of neurons, axons, and blood vessels in the peri-infarct region was significantly higher in BMSC-treated mice, accompanied with enhanced local blood flow recovery. Western blotting showed that BMSC treatment increased the expression of stromal cell-derived factor-1 (SDF-1), vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF) in the peri-infarct region. Moreover, the expression of the axonal growth associated protein-43 (GAP-43) was markedly increased, whereas the axonal growth inhibiting proteins ROCK II and NG2 were suppressed in the BMSC-treated brains. BMSC transplantation also promoted directional migration and survival of doublecortin (DCX)-positive neuroblasts in the peri-infarct region. The present investigation thus provides novel evidence that BMSC transplantation has the potential to repair the ischemia-damaged neural networks and restore lost neuronal connections. The recovered circuit activity likely contributes to the improved sensorimotor function after focal ischemic stroke and BMSC transplantation.

Immunological characteristics of human mesenchymal stem cells and multipotent adult progenitor cells

Somatic, also termed adult, stem cells are highly attractive biomedical cell candidates because of their extensive replication potential and functional multilineage differentiation capacity. They can be used for drug and toxicity screenings in preclinical studies, as in vitro model to study differentiation or for regenerative medicine to aid in the repair of tissues or replace tissues that are lost upon disease, injury or ageing. Multipotent adult progenitor cells (MAPCs) and mesenchymal stem cells (MSCs) are two types of adult stem cells derived from bone marrow that are currently being used clinically for tissue regeneration and for their immunomodulatory and trophic effects. This review will give an overview of the phenotypic and functional differences between human MAPCs and MSCs, with a strong emphasis on their immunological characteristics. Finally, we will discuss the clinical studies in which MSCs and MAPCs are already used.

[The role of adult bone marrow derived mesenchymal stem cells in the repair of tissue injuries]

Mesenchymal stem cells, which reside in adult bone marrow are multipotent, have an excellent regeneration potential for tissue repair. These cells are able to differentiate in cell culture not only into mesodermal lineages but also into other lineages of ectodermal and endodermal cells. This regenerative process is assisted by application of bioactive molecules, specific growth factors and biomaterials (scaffolds). The cell therapy is successfully used in the treatment of bone defects, nonunions, osteoblasts formed from the mesenchymal stem cells. At present, there are encouraging data in the clinical practice. The mesenchymal stem cell seems to be successful in the regeneration of articular cartilage. There are further promising data for the application of mesenchymal stem cells in the treatment of myocardial infarction, neurologic diseases, liver and kidney diseases and injuries and diabetes mellitus. The aim of this review is to survey the molecular characteristics of mesenchymal stem cells and specific growth factors using the data of preclinical investigations and to call attention to their possible clinical application.

Mesenchymal stem cell population isolated from the subepithelial layer of umbilical cord tissue

The therapeutic use of stem cells to treat diseases and injuries is a promising tool in regenerative medicine. The umbilical cord provides a rich source of stem cells; we have previously reported a population of stem cells isolated from Wharton's jelly. In this report, we aimed to isolate a novel cell population that was different than those found in Wharton's jelly. We isolated stem cells from the subepithelial layer of the umbilical cord; the cells could be expanded for greater than 90 population doubling and had mesenchymal stem cell characteristics, expressing CD9, SSEA4, CD44, CD90, CD166, CD73, and CD146 but were negative for STRO-1. The cells can be directionally differentiated and undergo osteo-, chondro-, adipo-, and cardiogenesis. In addition, we have identified for the first time that mesenchymal stem cells isolated from umbilical cord can produce microvesicles, termed exosomes. This is the first report describing a stem cell population isolated from the subepithelial layer of the umbilical cord. Given the growth capacity, multilineage potential, and most importantly the low levels of HLA-ABC, we propose that this novel cell isolated from the subepithelial layer of umbilical cord is an ideal candidate for allogeneic cell-based therapy.

Human induced pluripotent stem cells improve stroke outcome and reduce secondary degeneration in the recipient brain

Human induced pluripotent stem cells (hiPSCs) are a most appealing source for cell replacement therapy in acute brain lesions. We evaluated the potential of hiPSC therapy in stroke by transplanting hiPSC-derived neural progenitor cells (NPCs) into the postischemic striatum. Grafts received host tyrosine hydroxylase-positive afferents and contained developing interneurons and homotopic GABAergic medium spiny neurons that, with time, sent axons to the host substantia nigra. Grafting reversed stroke-induced somatosensory and motor deficits. Grafting also protected the host substantia nigra from the atrophy that follows disruption of reciprocal striatonigral connections. Graft innervation by tyrosine hydoxylase fibers, substantia nigra protection, and somatosensory functional recovery were early events, temporally dissociated from the slow maturation of GABAergic neurons in the grafts and innervation of substantia nigra. This suggests that grafted hiPSC-NPCs initially exert trophic effects on host brain structures, which precede integration and potential pathway reconstruction. We believe that transplantation of NPCs derived from hiPSCs can provide useful interventions to limit the functional consequences of stroke through both neuroprotective effects and reconstruction of impaired pathways.

Suppression of astrocyte lineage in adult hippocampal progenitor cells expressing hippocampal cholinergic neurostimulating Peptide precursor in an in vivo ischemic model

Hippocampal cholinergic neurostimulating peptide (HCNP) is known to promote differentiation of septohippocampal cholinergic neurons. The HCNP precursor protein (HCNP-pp) may play several roles, for example, as an ATP-binding protein, a Raf kinase inhibitor protein, and a phosphatidylethanolamine-binding protein, as well as a precursor for HCNP. This study therefore aimed to elucidate the involvement of HCNP-pp in specific neural lineages after stroke using a hypoxic-ischemic (HI) rat model of brain ischemia. The specific neural lineages in the hippocampus were investigated 14 days after ischemia. Some bromodeoxyuridine (BrdU)(+) neural progenitor cells in the hippocampus of hypoxic, HI, or sham-operated rats expressed HCNP-pp. Almost half of the BrdU(+)/HCNP-pp(+) cells also expressed the oligodendrocyte lineage marker 2',3'-cyclic nucleotide 3'-phosphodiesterase, whereas only a few BrdU(+)/HCNP-pp(+) cells in the hippocampus in HI brains expressed the neuronal lineage marker, doublecortin (DCX). Interestingly, no BrdU(+)/HCNP-pp(+) progenitor cells in hypoxic, HI, or sham-operated brains expressed the astrocyte lineage marker, glial fibrillary acidic protein. Together with previous in vitro data, the results of this study suggest that the expression level of HCNP-pp regulates the differentiation of neural progenitor cells into specific neural lineages in the HI hippocampus, indicating that neural stem cell fate can be controlled via the HCNP-pp mediating pathway.

Therapeutic benefit of treatment of stroke with simvastatin and human umbilical cord blood cells: neurogenesis, synaptic plasticity, and axon growth

The therapeutic efficacy of cell-based therapy after stroke can be enhanced by making the host brain tissue more receptive to the administered cells, which thereby facilitates brain plasticity. We hypothesized that simvastatin increases human umbilical cord blood cell (HUCBC) migration into the ischemic brain and promotes brain plasticity and neurological functional outcome after stroke. Rats were subjected to 2-h middle cerebral artery occlusion (MCAo) and administered subtherapeutic doses of simvastatin (0.5 mg/kg, gavaged daily for 7 days), HUCBCs (1 × 10(6), one time injection via tail vein), or combination simvastatin with HUCBCs starting at 24 h after stroke. Combination treatment of stroke showed an interactive effect in improvement of neurological outcome compared with simvastatin or HUCBC monotherapy groups. In addition, combination treatment significantly increased brain-derived neurotrophic factor/TrkB expression and the number of engrafted HUCBCs in the ischemic brain compared with HUCBC monotherapy. The number of engrafted HUCBCs was significantly correlated with functional outcome (modified neurological severity score). Combination treatment significantly increased neurogenesis and synaptic plasticity in the ischemic brain, and promoted neuroblast migration in cultured subventricular zone explants. Using primary cultured neurons (PCNs), we found that combination treatment enhanced neurite outgrowth compared with nontreatment control, simvastatin or HUCBC supernatant monotherapy. Inhibition of TrkB significantly attenuated combination treatment-induced neurite outgrowth. Our data indicate that combination simvastatin and HUCBC treatment of stroke increases BDNF/TrkB expression, enhances HUCBC migration into the ischemic brain, amplifies endogenous neurogenesis, synaptic plasticity and axonal growth, and thereby improves functional outcome after stroke.

Determination of the therapeutic time window for human umbilical cord blood mononuclear cell transplantation following experimental stroke in rats

Experimental treatment strategies using human umbilical cord blood mononuclear cells (hUCB MNCs) represent a promising option for alternative stroke therapies. An important point for clinical translation of such treatment approaches is knowledge on the therapeutic time window. Although expected to be wider than for thrombolysis, the exact time window for hUCB MNC therapy is not known. Our study aimed to determine the time window of intravenous hUCB MNC administration after middle cerebral artery occlusion (MCAO). Male spontaneously hypertensive rats underwent MCAO and were randomly assigned to hUCB MNC administration at 4, 24, 72, and 120 or 14 days. Influence of cell treatment was observed by magnetic resonance imaging on days 1, 8, and 29 following MCAO and by assessment of functional neurological recovery. On day 30, brains were screened for glial scar development and presence of hUCB MNCs. Further, influence of hUCB MNCs on necrosis and apoptosis in postischemic neural tissue was investigated in hippocampal slices cultures. Transplantation within a 72-h time window resulted in an early improvement of functional recovery, paralleled by a reduction of brain atrophy and diminished glial scarring. Cell transplantation 120 h post-MCAO only induced minor functional recovery without changes in the brain atrophy rate and glial reactivity. Later transplantation (14 days) did not show any benefit. No evidence for intracerebrally localized hUCB MNCs was found in any treatment group. In vitro hUCB MNCs were able to significantly reduce postischemic neural necrosis and apoptosis. Our results for the first time indicate a time window of therapeutic hUCB MNC application of at least 72 h. The time window is limited, but wider than compared to conventional pharmacological approaches. The data furthermore confirms that differentiation and integration of administered cells is not a prerequisite for poststroke functional improvement and lesion size reduction.

Differentiated mesenchymal stem cells for sciatic nerve injury

Sciatic nerve injury is common and may cause neurological deficits. Previous studies showed that administration of neurotrophic factors (NTFs), naturally occurring proteins that support the development and survival of neurons, preserved and protected damaged motor neuron in the injured sciatic nerve. We have been successful in converting bone marrow-derived mesenchymal stem cells into astrocyte-like cells that produce and secrete NTFs (NTF(+) cells). These cells demonstrate typical astrocyte morphology, express characteristic astrocyte markers and secrete high levels of NTFs. We have already shown that these cells and their conditioned media can protect neurons in culture and in animal models of neurodegenerative diseases. In the current study we examined whether NTF(+) cells are capable of rescuing motor neurons in a rat sciatic nerve injury model, where the right hind limb sciatic nerve was crushed. Rats were transplanted with NTF(+) cells, MSCs or PBS into the lesion site. In rats injected with the NTF(+) cells motor function was markedly preserved. Moreover, NTF(+) cells significantly inhibited the degeneration of the neuromuscular junctions and preserved the myelinated motor axons. Our findings suggest that autologous therapeutic approach can alleviate signs of sciatic nerve injury and probably other neurological disorders.

The great migration of bone marrow-derived stem cells toward the ischemic brain: therapeutic implications for stroke and other neurological disorders

Accumulating laboratory studies have implicated the mobilization of bone marrow (BM)-derived stem cells in brain plasticity and stroke therapy. This mobilization of bone cells to the brain is an essential concept in regenerative medicine. Over the past ten years, mounting data have shown the ability of bone marrow-derived stem cells to mobilize from BM to the peripheral blood (PB) and eventually enter the injured brain. This homing action is exemplified in BM stem cell mobilization following ischemic brain injury. Various BM-derived cells, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and very small embryonic-like cells (VSELs) have been demonstrated to exert therapeutic benefits in stroke. Here, we discuss the current status of these BM-derived stem cells in stroke therapy, with emphasis on possible cellular and molecular mechanisms of action that mediate the cells' beneficial effects in the ischemic brain. When possible, we also discuss the relevance of this therapeutic regimen in other central nervous system (CNS) disorders.

Bone marrow stem cell mobilization in stroke: a 'bonehead' may be good after all!

Mobilizing bone cells to the head, astutely referred to as 'bonehead' therapeutic approach, represents a major discipline of regenerative medicine. The last decade has witnessed mounting evidence supporting the capacity of bone marrow (BM)-derived cells to mobilize from BM to peripheral blood (PB), eventually finding their way to the injured brain. This homing action is exemplified in BM stem cell mobilization following ischemic brain injury. Here, I review accumulating laboratory studies implicating the role of therapeutic mobilization of transplanted BM stem cells for brain plasticity and remodeling in stroke.

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.

N-isopropylacrylamide-based thermoresponsive polyelectrolyte multilayer films for human mesenchymal stem cell expansion

Human mesenchymal stem cells (hMSCs) are colony-forming unit fibroblasts (CFU-F) derived from adult bone marrow and have significant potential for many cell-based tissue-engineering applications. Their therapeutic potential, however, is restricted by their diminishing plasticity as they are expanded in culture. In this study, we used N-isopropylacrylamide (NIPAM)-based thermoresponsive polyelectrolyte multilayer (N-PEMU) films as culture substrates to support hMSC expansion and evaluated their effects on cell properties. The N-PEMU films were made via layer-by-layer adsorption of thermoresponsive monomers copolymerized with charged monomers, positively charged allylamine hydrochloride (PAH), or negatively charged styrene sulfonic acid (PSS) and compared to fetal bovine serum (FBS) coated surfaces. Surface charges were shown to alter the extracellular matrix (ECM) structure and subsequently regulate hMSC responses including adhesion, proliferation, integrin expression, detachment, and colony forming ability. The positively charged thermal responsive surfaces improved cell adhesion and growth in a range comparable to control surfaces while maintaining significantly higher CFU-F forming ability. Immunostaining and Western blot results indicate that the improved cell adhesion and growth on the positively charged surfaces resulted from the elevated adhesion of ECM proteins such as fibronectin on the positively charge surfaces. These results demonstrate that the layer-by-layer approach is an efficient way to form PNIPAM-based thermal responsive surfaces for hMSC growth and removal without enzymatic treatment. The results also show that surface charge regulates ECM adhesion, which in turn influences not only cell adhesion but also CFU-forming ability and their multi-lineage differentiation potential.

Musashi1 and hairy and enhancer of split 1 high expression cells derived from embryonic stem cells enhance the repair of small-intestinal injury in the mouse

BACKGROUND

Embryonic stem cells have great plasticity. In this study, we repaired impaired small intestine by transplanting putative intestinal epithelial stem cells (Musashi1 and hairy and enhancer of split 1 high expression cells) derived from embryonic stem cells.

METHODS

The differentiation of definitive endoderm in embryoid bodies, derived from male ES-E14TG2a cells by the hanging-drop method, was monitored to define a time point for maximal induction of putative intestinal epithelial stem cells by epidermal growth factor. Furthermore, to evaluate the regenerative potential of intestinal epithelium, these putative stem cells were engrafted into NOD/SCID mice and female mice with enteritis. Donor cells were located by SRY DNA in situ hybridization.

RESULTS

The results revealed that definitive endodermal markers were highly expressed in 5-day embryoid bodies. These embryoid body cells were induced into putative intestinal epithelial stem cells on the 5th day of epidermal growth factor administration. Grafts from these cells consisted of adenoid structures and nonspecific structural cells with strong expression of small-intestinal epithelial cell markers. In situ hybridization revealed that the donor cells could specifically locate in damaged intestinal epithelium, contribute to epithelial structures, and enhance regeneration.

CONCLUSIONS

In conclusion, the Musashi1 and hairy and enhancer of split 1 high expression cells, derived from mouse embryonic stem cells, locate predominantly in impaired small-intestinal epithelium after transplantation and contribute to epithelial regeneration.

Glial cell line-derived neurotrophic factor-secreting genetically modified human bone marrow-derived mesenchymal stem cells promote recovery in a rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of nigrostriatal dopaminergic (DA) neurons. The therapeutic potential of glial cell line-derived neurotrophic factor (GDNF), the most potent neurotrophic factor for DA neurons, has been demonstrated in many experimental models of PD. However, chronic delivery of GDNF to DA neurons in the brain remains an unmet challenge. Here, we report the effects of GDNF-releasing Notch-induced human bone marrow-derived mesenchymal stem cells (MSC) grafted into striatum of the 6-hydroxydopamine (6-OHDA) progressively lesioned rat model of PD. Human MSC, obtained from bone marrow aspirates of young, healthy adult volunteers, were transiently transfected with the intracellular domain of the Notch1 gene (NICD) to generate SB623 cells. SB623 cells expressing GDNF and/or humanized Renilla green fluorescent protein (hrGFP) following lentiviral transduction or nontransduced cells were stereotaxically placed into rat striatum 1 week after a unilateral partial 6-OHDA striatal lesion. At 4 weeks, rats that had received GDNF-transduced SB623 cells had significantly decreased amphetamine-induced rotation compared with control rats, although this effect was not observed in rats that received GFP-transduced or nontransduced SB623 cells. At 5 weeks, rejuvenated tyrosine hydroxylase-immunoreactive (TH-IR) fibers that appeared to be host DA axons were observed in and around grafts. This effect was more prominent in rats that received GDNF-secreting cells and was not observed in controls. These observations suggest that human bone-marrow derived MSC, genetically modified to secrete GDNF, hold potential as an allogeneic or autologous stem cell therapy for PD.

New concepts on the immune modulation mediated by mesenchymal stem cells

Mesenchymal stem cells (MSCs) are the nonhematopoietic multipotent progenitor cells found in various adult tissues. They are characterized by their ease of isolation and their rapid growth in vitro while maintaining their differentiation potential, allowing for extensive expansion in culture that yields large quantities suitable for therapeutic use. This article reviews the immunomodulatory activities associated with MSCs. Numerous studies have demonstrated that MSCs are potently immunosuppressive in vitro and in vivo. However, this article presents a new paradigm in MSC biology, in which MSCs, at least in vitro, can undergo polarization into either a pro-inflammatory or an immunosuppressive phenotype.

An Efficient Approach to Isolation and Characterization of Pre- and Postnatal Umbilical Cord Lining Stem Cells for Clinical Applications

There have been various forms of mesenchymal stem cell-like (MSC-like) cells isolated from umbilical cords (UCs). The isolation of umbilical cord lining stem cells (ULSCs) may be of great value for those interested in a possible treatment to several disease/disorders. Unlike umbilical cord blood cells, these cells are unique because they can be expanded to therapeutically relevant numbers and cryopreserved for several different uses. Here we efficiently isolate stem cells from a small segment of pre- and postnatal UCs, and obtain therapeutically relevant amounts of ULSCs within 3 weeks. We demonstrate their growth potential and characterize them using immunocytochemistry, flow cytometry, and RT-PCR. In addition, we differentiate ULSCs into multiple lineages. Pre- and postnatal ULSCs are morphologically similar to mesenchymal stem cells (MSCs) and easily expand to greater than 70 population doublings. They express pluripotent markers Oct4 and nanog at the protein and RNA level. Flow cytometry demonstrates that they express markers indicative of MSCs in addition to high SSEA-4 expression. ULSCs are easily differentiated into osteogenic, adipogenic, chondrogenic, cardiogenic, and neurogenic cells. Pre- and postnatal ULSCs are characteristically similar in respect to their growth, marker expression, and plasticity, demonstrating they are highly conserved throughout development. ULSCs have phenotypic and genotypic properties of MSCs. These studies demonstrate the therapeutic potential of an otherwise discarded tissue. They are a perfect HLA match for the donor and an excellent match for immediate family members; therefore, they may serve as a therapeutic cell source.

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.

Human umbilical cord blood stem cells: rational for use as a neuroprotectant in ischemic brain disease

The use of stem cells for reparative medicine was first proposed more than three decades ago. Hematopoietic stem cells from bone marrow, peripheral blood and human umbilical cord blood (CB) have gained major use for treatment of hematological indications. CB, however, is also a source of cells capable of differentiating into various non-hematopoietic cell types, including neural cells. Several animal model reports have shown that CB cells may be used for treatment of neurological injuries. This review summarizes the information available on the origin of CB-derived neuronal cells and the mechanisms proposed to explain their action. The potential use of stem/progenitor cells for treatment of ischemic brain injuries is discussed. Issues that remain to be resolved at the present stage of preclinical trials are addressed.

Intravenous infusion of bone marrow mesenchymal stem cells improves brain function after resuscitation from cardiac arrest

OBJECTIVE

Allogeneic bone marrow mesenchymal stem cells were previously shown to improve myocardial function when administered intravenously after resuscitation from cardiac arrest in rats. Coincidental evidence of improved brain function prompted the present study.

DESIGN

Prospective, randomized, controlled study.

SETTING

University-affiliated research institute.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Using an established model in 20 male Sprague-Dawley rats in which 6 mins of untreated cardiac arrest was followed by cardiopulmonary resuscitation, animals were randomized to receive 5 x 10(6) mesenchymal stem cells labeled with PKH26 in phosphate buffer solution or phosphate buffer solution alone as a placebo at 2 hrs after restoration of spontaneous circulation. The stem cells or buffer diluent were injected into a catheter advanced from the jugular vein into the right atrium.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements in addition to 35-day survival included somatosensor testing of capability for removal of an adhesive patch applied to both front paws, testing of motor function using a rotating cylinder, and observational scoring of the severity of neurologic impairment. Labeled mesenchymal stem cells were subsequently identified and counted in 5 microm sections obtained from defined sites in the harvested brain. Immunohistochemistry was used to identify neural cells differentiation of mesenchymal stem cells. Adhesive removal, motor function test, neurologic severity score, and 35-day survival were each significantly improved in comparison with control animals. Labeled mesenchymal stem cells were identified in the hippocampus, cortex, pons, medulla, and cerebellum and expressed protein markers phenotypic neural cells.

CONCLUSIONS

Mesenchymal stem cells injected into the right atrium of rats after resuscitation from cardiac arrest were identified in brains harvested 35 days later. Brain function was significantly improved. Accordingly, venous injection of mesenchymal stem cells after cardiopulmonary resuscitation has promise of minimizing the severity of postresuscitation neurologic impairment.

Hemopoietic and angiogenetic progenitors in healthy athletes: different responses to endurance and maximal exercise

The effects of endurance or maximal exercise on mobilization of bone marrow-derived hemopoietic and angiogenetic progenitors in healthy subjects are poorly defined. In 10 healthy amateur runners, we collected venous blood before, at the end of, and the day after a marathon race (n = 9), and before and at the end of a 1.5-km field test (n = 8), and measured hemopoietic and angiogenetic progenitors by flow cytometry and culture assays, as well as plasma or serum concentrations of several cytokines/growth factors. After the marathon, CD34(+) cells were unchanged, whereas clonogenetic assays showed decreased number of colonies for both erythropoietic (BFU-E) and granulocyte-monocyte (CFU-GM) series, returning to baseline the morning post-race. Conversely, CD34(+) cells, BFU-E, and CFU-GM increased after the field test. Angiogenetic progenitors, assessed as CD34(+)KDR(+) and CD133(+)VE-cadherin(+) cells or as adherent cells in culture expressing endothelial markers, increased after both endurance and maximal exercise but showed a different pattern between protocols. Interleukin-6 increased more after the marathon than after the field test, whereas hepatocyte growth factor and stem cell factor increased similarly in both protocols. Plasma levels of angiopoietin (Ang) 1 and 2 increased after both types of exercise, whereas the Ang-1-to-Ang-2 ratio or vascular endothelial growth factor-A were little affected. These data suggest that circulating hemopoietic progenitors may be utilized in peripheral tissues during prolonged endurance exercise. Endothelial progenitor mobilization after exercise in healthy trained subjects appears modulated by the type of exercise. Exercise-induced increase in growth factors suggests a physiological trophic effect of exercise on the bone marrow.

Human mesenchymal stromal cells and their derivative, SB623 cells, rescue neural cells via trophic support following in vitro ischemia

Cell transplantation is a promising treatment strategy for many neurological disorders, including stroke, which can target multiple therapeutic mechanisms in a sustained fashion. We investigated the ability of human mesenchymal stromal cells (MSCs) and MSC-derived SB623 cells to rescue neural cells via trophic support following an in vitro stroke model. Following oxygen glucose deprivation, cortical neurons or hippocampal slices were cocultured with either MSCs or SB623 cells separated by a semiporous membrane (prohibits cell-cell contact) or with MSC- or SB623 cell-conditioned medium. MSCs, SB623 cells, MSC-conditioned media, and SB623 cell-conditioned media all significantly reduced neural cell damage/death compared to untreated conditions, and the rescue effect of the conditioned media was dose dependent. We identified 11 neurotrophic factors secreted by MSCs and/or SB623 cells. This study emphasizes the importance of trophic support provided by marrow-derived cells, which likely contributes to the efficacy of cell therapy for brain injury.

How useful are stem cells in PD therapy?

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. The onset of PD is usually after the age of 50. Clinical symptoms of PD are not manifested until 60-80% of dopaminergic neurons in the midbrain have been affected. Cell replacement has been a promising approach for the treatment of PD. Fetal mesencephalic dopaminergic neurons seemed to improve the motor disability in patients in some early studies. However, the clinical application of this approach may be limited by ethical and logistic concerns, as well as by side effects. On the other hand, embryonic stem (ES) cells are promising candidates because of their ability to provide an unlimited supply of specific cell types, their accessibility to genetic modifications, and their broad developmental potentials. Transplants of undifferentiated ES cells were able to proliferate and fully differentiate into dopaminergic neurons in a rodent PD model. One of the concerns though is the risk of tumor formation. The tumorigenic potential of ES cells seems to be greatly reduced when cells are predifferentiated into dopaminergic neurons in vitro before implantation. Recent developments in the induction of pluripotent stem cells from somatic adult cells provide a tremendous opportunity for this field. Initial success has been reported in a rodent PD model using iPS cells (induced pluripotent stem cells). However, whether this initial result can be successfully translated into human clinical studies still needs to be determined.