From marrow to brain: expression of neuronal phenotypes in adult mice

Adult Neurogenesis: Lessons from Crayfish and the Elephant in the Room

The 1st-generation neural precursors in the crustacean brain are functionally analogous to neural stem cells in mammals. Their slow cycling, migration of their progeny, and differentiation of their descendants into neurons over several weeks are features of the neural precursor lineage in crayfish that also characterize adult neurogenesis in mammals. However, the 1st-generation precursors in crayfish do not self-renew, contrasting with conventional wisdom that proposes the long-term self-renewal of adult neural stem cells. Nevertheless, the crayfish neurogenic niche, which contains a total of 200-300 cells, is never exhausted and neurons continue to be produced in the brain throughout the animal's life. The pool of neural precursors in the niche therefore cannot be a closed system, and must be replenished from an extrinsic source. Our in vitro and in vivo data show that cells originating in the innate immune system (but not other cell types) are attracted to and incorporated into the neurogenic niche, and that they express a niche-specific marker, glutamine synthetase. Further, labeled hemocytes that undergo adoptive transfer to recipient crayfish generate cells in neuronal clusters in the olfactory pathway of the adult brain. These hemocyte descendants express appropriate neurotransmitters and project to target areas typical of neurons in these regions. These studies indicate that under natural conditions, the immune system provides neural precursors supporting adult neurogenesis in the crayfish brain, challenging the canonical view that ectodermal tissues generating the embryonic nervous system are the sole source of neurons in the adult brain. However, these are not the first studies that directly implicate the immune system as a source of neural precursor cells. Several types of data in mammals, including adoptive transfers of bone marrow or stem cells as well as the presence of fetal microchimerism, suggest that there must be a population of cells that are able to access the brain and generate new neurons in these species.

Phase 1 Trial of Autologous Bone Marrow Stem Cell Transplantation in Patients with Spinal Cord Injury

Introduction. A total of 18 patients, with complete motor deficits and paraplegia caused by thoracic and lumbar spine trauma without muscle atrophy or psychiatric problems, were included into this study. Materials and Methods. The bone marrow was aspirated from the anterior iliac crest under local anesthesia and the mononuclear fraction was isolated by density gradient method. At least 750 million mononuclear-enriched cells, suspended in 2 mL of saline, were infused intrathecally. Results and Discussion. The study reports demonstrated improvement of motor and sensory functions of various degrees observed in 9 of the 18 (50%) cases after bone marrow stem cell transplantation. Measured by the American Spinal Injury Association (ASIA) scale, 7 (78%) out of the 9 patients observed an improvement by one grade, while two cases (22%) saw an improvement by two grades. However, there were no cases in which the condition was improved by three grades. Conclusions. Analysis of subsequent treatment results indicated that the transplantation of mononuclear-enriched autologous BMSCs is a feasible and safe technique. However, successful application of the BMSCs in the clinical practice is associated with the necessity of executing more detailed examinations to evaluate the effect of BMSCs on the patients with spinal cord injury.

Adipose-Derived Stem Cells Expressing the Neurogenin-2 Promote Functional Recovery After Spinal Cord Injury in Rat

Neurogenin2 (Ngn2) is a proneural gene that directs neuronal differentiation of progenitor cells during development. This study aimed to investigate whether the use of adipose-derived stem cells (ADSCs) over-expressing the Ngn2 transgene (Ngn2-ADSCs) could display the characteristics of neurogenic cells and improve functional recovery in an experimental rat model of SCI. ADSCs from rats were cultured and purified in vitro, followed by genetically modified with the Ngn2 gene. Forty-eight adult female Sprague-Dawley rats were randomly assigned to three groups: the control, ADSCs, and Ngn2-ADSCs groups. The hind-limb motor function of all rats was recorded using the Basso, Beattie, and Bresnahan locomotor rating scale for 8 weeks. Moreover, hematoxylineosin staining and immunohistochemistry were also performed. After neural induction, positive expression rate of NeuN in Ngn2-ADSCs group was upon 90 %. Following transplantation, a great number of ADSCs was found around the center of the injury spinal cord at 1 and 4 weeks, which improved retention of tissue at the lesion site. Ngn2-ADSCs differentiated into neurons, indicated by the expression of neuronal markers, NeuN and Tuj1. Additionally, transplantation of Ngn2-ADSCs upregulated the trophic factors (brain-derived neurotrophic factor and vascular endothelial growth factor), and inhibited the glial scar formation, which was indicated by immunohistochemistry with glial fibrillary acidic protein. Finally, Ngn2-ADSCs-treated animals showed the highest functional recovery among the three groups. These findings suggest that transplantation of Ngn2-overexpressed ADSCs promote the functional recovery from SCI, and improve the local microenvironment of injured cord in a more efficient way than that with ADSCs alone.

Optical Coherence Tomography for Brain Imaging and Developmental Biology

Optical coherence tomography (OCT) is a promising research tool for brain imaging and developmental biology. Serving as a three-dimensional optical biopsy technique, OCT provides volumetric reconstruction of brain tissues and embryonic structures with micrometer resolution and video rate imaging speed. Functional OCT enables label-free monitoring of hemodynamic and metabolic changes in the brain in vitro and in vivo in animal models. Due to its non-invasiveness nature, OCT enables longitudinal imaging of developing specimens in vivo without potential damage from surgical operation, tissue fixation and processing, and staining with exogenous contrast agents. In this paper, various OCT applications in brain imaging and developmental biology are reviewed, with a particular focus on imaging heart development. In addition, we report findings on the effects of a circadian gene (Clock) and high-fat-diet on heart development in Drosophila melanogaster. These findings contribute to our understanding of the fundamental mechanisms connecting circadian genes and obesity to heart development and cardiac diseases.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

LINGO-1-Fc-Transduced Neural Stem Cells Are Effective Therapy for Chronic Stage Experimental Autoimmune Encephalomyelitis

The chronic stage multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), remains refractory to current treatments. This refractory nature may be due to the fact that current treatments are primarily immunomodulatory, which prevent further demyelination but lack the capacity to promote remyelination. Several approaches, including transplantation of neural stem cells (NSCs) or antagonists to LINGO-1, a key part of the receptor complex for neuroregeneration inhibitors, have been effective in suppressing the acute stage of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. However, their effect on the chronic stage EAE is not known. Here, we show that transplantation of NSCs had only a slight therapeutic effect when treatment started at the chronic stage of EAE (e.g., injected at day 40 postimmunization). However, NSCs engineered to produce LINGO-1-Fc, a soluble LINGO-1 antagonist, significantly promoted neurological recovery as demonstrated by amelioration of clinical signs, improvement in axonal integrity, and enhancement of oligodendrocyte maturation and neuron repopulation. Significantly enhanced NAD production and Sirt2 expression were also found in the CNS of mice treated with LINGO-1-Fc-producing NSC. Moreover, differentiation of LINGO-1-Fc-producing NSCs into oligodendrocytes in vitro was largely diminished by an NAMPT inhibitor, indicating that LINGO-1-Fc enhances the NAMPT/NAD/Sirt2 pathway. Together, our study establishes a CNS-targeted, novel LINGO-1-Fc delivery system using NSCs, which represents a novel and effective NSC-based gene therapy approach for the chronic stage of MS.

Calcitonin gene-related peptide is a key factor in the homing of transplanted human MSCs to sites of spinal cord injury

Mesenchymal stem cells (MSCs) can be used to treat many diseases, including spinal cord injury (SCI). Treatment relies mostly on the precise navigation of cells to the injury site for rebuilding the damaged spinal cord. However, the key factors guiding MSCs to the epicenter of SCI remain unknown. Here, we demonstrated that calcitonin gene-related peptide (CGRP), a neural peptide synthesized in spinal cord, can dramatically aid the homing of human umbilical cord mesenchymal stem cells (HUMSCs) in spinal cord-transected SCI rats. First, HUMSCs exhibited chemotactic responses in vitro to CGRP. By time-lapse video analysis, increased chemotactic index (CMI), forward migration index (FMI) and speed contributed to this observed migration. Then, through enzyme immunoassay, higher CGRP concentrations at the lesion site were observed after injury. The release of CGRP directed HUMSCs to the injury site, which was suppressed by CGRP 8-37, a CGRP antagonist. We also verified that the PI3K/Akt and p38MAPK signaling pathways played a critical role in the CGRP-induced chemotactic migration of HUMSCs. Collectively, our data reveal that CGRP is a key chemokine that helps HUMSCs migrate to the lesion site and thereby can be used as a model molecule to study MSCs homing after SCI.

Neurotrophic Enhancers as Therapy for Behavioral Deficits in Rodent Models of Huntington's Disease: Use of Gangliosides, Substituted Pyrimidines, and Mesenchymal Stem Cells

The interest in using neurotrophic factors as potential treatments for neurodegenerative disorders, such as Huntington's disease, has grown in the past decade. A major impediment for the clinical utility of neurotrophic factors is their inability to cross the blood-brain barrier in therapeutically significant amounts. Although several novel mechanisms for delivering exogenous neurotrophins to the brain have been developed, most of them involve invasive procedures or present significant risks. One approach to circumventing these problems is using therapeutic agents that can be administered systemically and have the ability to enhance the activity of neurotrophic factors. This review highlights the use of gangliosides, substituted pyrimidines, and mesenchymal stem cells as neurotrophic enhancers that have significant therapeutic potential while avoiding the pitfalls of delivering exogenous neurotrophic factors through the blood-brain barrier. The review focuses on the potential of these neurotrophic enhancers for treating the behavioral deficits in rodent models of Huntington's disease.

Verification of the Cross Immunoreactivity of A60, a Mouse Monoclonal Antibody against Neuronal Nuclear Protein

A60, the mouse monoclonal antibody against the neuronal nuclear protein (NeuN), is the most widely used neuronal marker in neuroscience research and neuropathological assays. Previous studies identified fragments of A60-immunoprecipitated protein as Synapsin I (Syn I), suggesting the antibody will demonstrate cross immunoreactivity. However, the likelihood of cross reactivity has never been verified by immunohistochemical techniques. Using our established tissue processing and immunofluorescent staining protocols, we found that A60 consistently labeled mossy fiber terminals in hippocampal area CA3. These A60-positive mossy fiber terminals could also be labeled by Syn I antibody. After treating brain slices with saponin in order to better preserve various membrane and/or vesicular proteins for immunostaining, we observed that A60 could also label additional synapses in various brain areas. Therefore, we used A60 together with a rabbit monoclonal NeuN antibody to confirm the existence of this cross reactivity. We showed that the putative band positive for A60 and Syn I could not be detected by the rabbit anti-NeuN in Western blotting. As efficient as Millipore A60 to recognize neuronal nuclei, the rabbit NeuN antibody demonstrated no labeling of synaptic structures in immunofluorescent staining. The present study successfully verified the cross reactivity present in immunohistochemistry, cautioning that A60 may not be the ideal biomarker to verify neuronal identity due to its cross immunoreactivity. In contrast, the rabbit monoclonal NeuN antibody used in this study may be a better candidate to substitute for A60.

Migration of bone marrow progenitor cells in the adult brain of rats and rabbits

Neurogenesis takes place in the adult mammalian brain in three areas: Subgranular zone of the dentate gyrus (DG); subventricular zone of the lateral ventricle; olfactory bulb. Different molecular markers can be used to characterize the cells involved in adult neurogenesis. It has been recently suggested that a population of bone marrow (BM) progenitor cells may migrate to the brain and differentiate into neuronal lineage. To explore this hypothesis, we injected recombinant SV40-derived vectors into the BM and followed the potential migration of the transduced cells. Long-term BM-directed gene transfer using recombinant SV40-derived vectors leads to expression of the genes delivered to the BM firstly in circulating cells, then after several months in mature neurons and microglial cells, and thus without central nervous system (CNS) lesion. Most of transgene-expressing cells expressed NeuN, a marker of mature neurons. Thus, BM-derived cells may function as progenitors of CNS cells in adult animals. The mechanism by which the cells from the BM come to be neurons remains to be determined. Although the observed gradual increase in transgene-expressing neurons over 16 mo suggests that the pathway involved differentiation of BM-resident cells into neurons, cell fusion as the principal route cannot be totally ruled out. Additional studies using similar viral vectors showed that BM-derived progenitor cells migrating in the CNS express markers of neuronal precursors or immature neurons. Transgene-positive cells were found in the subgranular zone of the DG of the hippocampus 16 mo after intramarrow injection of the vector. In addition to cells expressing markers of mature neurons, transgene-positive cells were also positive for nestin and doublecortin, molecules expressed by developing neuronal cells. These cells were actively proliferating, as shown by short term BrdU incorporation studies. Inducing seizures by using kainic acid increased the number of BM progenitor cells transduced by SV40 vectors migrating to the hippocampus, and these cells were seen at earlier time points in the DG. We show that the cell membrane chemokine receptor, CCR5, and its ligands, enhance CNS inflammation and seizure activity in a model of neuronal excitotoxicity. SV40-based gene delivery of RNAi targeting CCR5 to the BM results in downregulating CCR5 in circulating cells, suggesting that CCR5 plays an important role in regulating traffic of BM-derived cells into the CNS, both in the basal state and in response to injury. Furthermore, reduction in CCR5 expression in circulating cells provides profound neuroprotection from excitotoxic neuronal injury, reduces neuroinflammation, and increases neuronal regeneration following this type of insult. These results suggest that BM-derived, transgene-expressing, cells can migrate to the brain and that they become neurons, at least in part, by differentiating into neuron precursors and subsequently developing into mature neurons.

Application potential of bone marrow mesenchymal stem cell (BMSCs) based tissue-engineering for spinal cord defect repair in rat fetuses with spina bifida aperta

Spina bifida aperta are complex congenital malformations resulting from failure of fusion in the spinal neural tube during embryogenesis. Despite surgical repair of the defect, most patients who survive with spina bifida aperta have a multiple system handicap due to neuron deficiency of the defective spinal cord. Tissue engineering has emerged as a novel treatment for replacement of lost tissue. This study evaluated the prenatal surgical approach of transplanting a chitosan-gelatin scaffold seeded with bone marrow mesenchymal stem cells (BMSCs) in the healing the defective spinal cord of rat fetuses with retinoic acid induced spina bifida aperta. Scaffold characterisation revealed the porous structure, organic and amorphous content. This biomaterial promoted the adhesion, spreading and in vitro viability of the BMSCs. After transplantation of the scaffold combined with BMSCs, the defective region of spinal cord in rat fetuses with spina bifida aperta at E20 decreased obviously under stereomicroscopy, and the skin defect almost closed in many fetuses. The transplanted BMSCs in chitosan-gelatin scaffold survived, grew and expressed markers of neural stem cells and neurons in the defective spinal cord. In addition, the biomaterial presented high biocompatibility and slow biodegradation in vivo. In conclusion, prenatal transplantation of the scaffold combined with BMSCs could treat spinal cord defect in fetuses with spina bifida aperta by the regeneration of neurons and repairmen of defective region.

Neurogenesis in Stroke Recovery

Stroke, resulting from limited blood flow to the brain, is one of the most important causes of morbidity and mortality worldwide. Stroke is classified as ischemic, due to lack of blood flow, or hemorrhagic, due to bleeding. Because 87 % of strokes are classified as ischemic, this type will be the predominant focus of this review. Except for thrombolytic therapy, there is no established treatment to reduce the neurological deficits caused by ischemic stroke. Therefore, it is necessary to develop new therapeutic strategies designed to improve neurological functions after ischemic stroke. Recently, therapies to enhance neurogenesis after ischemic stroke have been investigated. However, these approaches have not led to successful clinical outcomes. This review addresses the pathophysiology of stroke, neurogenesis after stroke, and how to stimulate these processes based on the current literature. Finally, ongoing clinical trials to improve neurological functions after stroke by enhancing neurogenesis are discussed in this review.

Articular cartilage: from formation to tissue engineering

Hyaline cartilage is the nonlinear, inhomogeneous, anisotropic, poro-viscoelastic connective tissue that serves as friction-reducing and load-bearing cushion in synovial joints and is vital for mammalian skeletal movements. Due to its avascular nature, low cell density, low proliferative activity and the tendency of chondrocytes to de-differentiate, cartilage cannot regenerate after injury, wear and tear, or degeneration through common diseases such as osteoarthritis. Therefore severe damage usually requires surgical intervention. Current clinical strategies to generate new tissue include debridement, microfracture, autologous chondrocyte transplantation, and mosaicplasty. While articular cartilage was predicted to be one of the first tissues to be successfully engineered, it proved to be challenging to reproduce the complex architecture and biomechanical properties of the native tissue. Despite significant research efforts, only a limited number of studies have evolved up to the clinical trial stage. This review article summarizes the current state of cartilage tissue engineering in the context of relevant biological aspects, such as the formation and growth of hyaline cartilage, its composition, structure and biomechanical properties. Special attention is given to materials development, scaffold designs, fabrication methods, and template-cell interactions, which are of great importance to the structure and functionality of the engineered tissue.

Human olfactory stem cells for injured facial nerve reconstruction in a rat model

BACKGROUND

The purpose of this study was to show the efficacy of olfactory stem cells for injured facial nerve reconstruction in a rat model.

METHODS

Olfactory stem cells were isolated from the olfactory mucosa of human participants. A 2-mm excision was performed on the right facial nerve of all rats. Reconstruction was performed with a conduit in group 1 (n = 9); a conduit and phosphate-buffered saline in group 2 (n = 9); and a conduit and labeled olfactory stem cell in group 3 (n = 9). Rats were followed for whisker movements and electroneuronography (ENoG) analyses.

RESULTS

The whisker-movement scores for group 3 were significantly different from other groups (p < .001). ENoG showed that the amplitude values for group 3 were significantly different from group 1 and group 2 (p = .030; p < .001). Group 3 showed marked olfactory stem cell under a fluorescence microscope.

CONCLUSION

This study suggests that olfactory stem cells may be used as a potent cellular therapy for accelerating the regeneration of peripheral nerve injuries. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2011-E2020, 2016.

Low-dose irradiation prior to bone marrow transplantation results in ATM activation and increased lethality in Atm-deficient mice

Ataxia telangiectasia is a genetic instability syndrome characterized by neurodegeneration, immunodeficiency, severe bronchial complications, hypersensitivity to radiotherapy and an elevated risk of malignancies. Repopulation with ATM-competent bone marrow-derived cells (BMDCs) significantly prolonged the lifespan and improved the phenotype of Atm-deficient mice. The aim of the present study was to promote BMDC engraftment after bone marrow transplantation using low-dose irradiation (IR) as a co-conditioning strategy. Atm-deficient mice were transplanted with green fluorescent protein-expressing, ATM-positive BMDCs using a clinically relevant non-myeloablative host-conditioning regimen together with TBI (0.2-2.0 Gy). IR significantly improved the engraftment of BMDCs into the bone marrow, blood, spleen and lung in a dose-dependent manner, but not into the cerebellum. However, with increasing doses, IR lethality increased even after low-dose IR. Analysis of the bronchoalveolar lavage fluid and lung histochemistry revealed a significant enhancement in the number of inflammatory cells and oxidative damage. A delay in the resolution of γ-H2AX-expression points to an insufficient double-strand break repair capacity following IR with 0.5 Gy in Atm-deficient splenocytes. Our results demonstrate that even low-dose IR results in ATM activation. In the absence of ATM, low-dose IR leads to increased inflammation, oxidative stress and lethality in the Atm-deficient mouse model.

Malignant transformation of bone marrow stromal cells induced by the brain glioma niche in rats

Normal human embryonic stem cells (hESCs) can develop neoplastic cancer stem cell (CSC) properties after coculture with transformed hESCs in vitro. In the present study, the influence of the tumor microenvironment on malignant transformation of bone marrow stromal cells (BMSCs) was studied after allografting a mixture of enhanced green fluorescent protein (EGFP)-labeled BMSCs and C6 glioma cells into the rat brain to understand the influence of the cellular environment, especially the tumor environment, on the transformation of grafted BMSCs in the rat brain. We performed intracerebral transplantation in the rat brain using EGFP-labeled BMSCs coinjected with C6 tumor cells. After transplantation, the EGFP-labeled cells were isolated from the tumor using fluorescence-activated cell sorting, and the characteristics of the recovered cells were investigated. Glioma-specific biomarkers of the sorted cells and the biological characteristics of the tumors were analyzed. The BMSCs isolated from the cografts were transformed into glioma CSCs, as indicated by the marked expression of the glioma marker GFAP in glioma cells, and of Nestin and CD133 in neural stem cells and CSCs, as well as rapid cell growth, decreased level of the tumor suppressor gene p53, increased level of the oncogene murine double minute gene 2 (MDM2), and recapitulation of glioma tissues in the brain. These data suggest that BMSCs can be transformed into CSCs, which can be further directed toward glioma formation under certain conditions, supporting the notion that the tumor microenvironment is involved in transforming normal BMSCs into glial CSCs.

Comparative Study on the Differentiation of Mesenchymal Stem Cells Between Fetal and Postnatal Rat Spinal Cord Niche

In a previous study, we established a prenatal surgical approach and transplanted mesenchymal stem cells (MSCs) into the fetal rat spinal column to treat neural tube defects (NTDs). We found that the transplanted MSCs survived and differentiated into neural lineage cells. Various cytokines and extracellular signaling systems in the spinal cord niche play an important role in cell differentiation. In this study, we observed the differentiation of transplanted MSCs in different spinal cord niches and further observed the expression of neurotrophic factors and growth factors in the spinal cord at different developmental stages to explore the mechanism of MSC differentiation in different spinal cord niches. The results showed that transplanted MSCs expressed markers of neural precursor cells (nestin), neurogliocytes (GFAP), and neurons (β-tubulin). The percentages of GFP(+)/nestin(+) double-positive cells in transplanted MSCs in E16, P1, and P21 rats were 18.31%, 12.18%, and 5.06%, respectively. The percentages of GFP(+)/GFAP(+) double-positive cells in E16, P1, and P21 rats were 32.01%, 15.35%, and 12.56%, respectively. The percentages of GFP(+)/β-tubulin(+) double-positive cells in E16, P1, and P21 were 11.76%, 7.62%, and 4.88%, respectively. The differentiation rates of MSCs in embryonic spinal cords were significantly higher than in postnatal spinal cords (p < 0.05). We found that the transplanted MSCs expressed synapsin-1 at different developmental stages. After MSC transplantation, we observed that neurotrophic factor-3 (NT-3), fibroblast growth factor-2 (FGF-2), FGF-8, transforming growth factor-α (TGF-α), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) significantly increased in the MSC transplantation group compared with the blank injection group. Furthermore, FGF-2 and VEGF expression were positively correlated with the number of surviving MSCs. In addition, we found that the expression of brain-derived neurotrophic factor (BDNF), NT-3, FGF-8, TGF-β, epidermal growth factor (EGF), and insulin-like growth factor (IGF) decreased with age, and the expression of FGF-2, FGF-10, FGF-20, TGF-α, and PDGF increased with age. Our data suggest that the embryonic spinal cord niche is more conducive to MSC differentiation after transplantation.

Stem cells: An insight into the therapeutic aspects from medical and dental perspectives

The recent advancements in the field of stem cell (SC) biology have increased the hope of achieving the definitive treatments for the diseases which are now considered incurable such as diabetes, Parkinson's disease and other chronic long standing conditions. To achieve this possibility, it is necessary to understand the basic concepts of SC biology to utilize in various advanced techniques of regenerative medicine including tissue engineering and gene therapy. This article highlights the types of SCs available and their therapeutic capacity in regenerative medical and dental fields.

Bone marrow-derived macrophages and the CNS: An update on the use of experimental chimeric mouse models and bone marrow transplantation in neurological disorders

The central nervous system (CNS) is a very unique system with multiple features that differentiate it from systemic tissues. One of the most captivating aspects of its distinctive nature is the presence of the blood brain barrier (BBB), which seals it from the periphery. Therefore, to preserve tissue homeostasis, the CNS has to rely heavily on resident cells such as microglia. These pivotal cells of the mononuclear lineage have important and dichotomous roles according to various neurological disorders. However, certain insults can overwhelm microglia as well as compromising the integrity of the BBB, thus allowing the infiltration of bone marrow-derived macrophages (BMDMs). The use of myeloablation and bone marrow transplantation allowed the generation of chimeric mice to study resident microglia and infiltrated BMDM separately. This breakthrough completely revolutionized the way we captured these 2 types of mononuclear phagocytic cells. We now realize that microglia and BMDM exhibit distinct features and appear to perform different tasks. Since these cells are central in several pathologies, it is crucial to use chimeric mice to analyze their functions and mechanisms to possibly harness them for therapeutic purpose. This review will shed light on the advent of this methodology and how it allowed deciphering the ontology of microglia and its maintenance during adulthood. We will also compare the different strategies used to perform myeloablation. Finally, we will discuss the landmark studies that used chimeric mice to characterize the roles of microglia and BMDM in several neurological disorders. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

The hematopoietic system in the context of regenerative medicine

Hematopoietic stem cells (HSC) represent the prototype stem cell within the body. Since their discovery, HSC have been the focus of intensive research, and have proven invaluable clinically to restore hematopoiesis following inadvertent radiation exposure and following radio/chemotherapy to eliminate hematologic tumors. While they were originally discovered in the bone marrow, HSC can also be isolated from umbilical cord blood and can be "mobilized" peripheral blood, making them readily available in relatively large quantities. While their ability to repopulate the entire hematopoietic system would already guarantee HSC a valuable place in regenerative medicine, the finding that hematopoietic chimerism can induce immunological tolerance to solid organs and correct autoimmune diseases has dramatically broadened their clinical utility. The demonstration that these cells, through a variety of mechanisms, can also promote repair/regeneration of non-hematopoietic tissues as diverse as liver, heart, and brain has further increased their clinical value. The goal of this review is to provide the reader with a brief glimpse into the remarkable potential HSC possess, and to highlight their tremendous value as therapeutics in regenerative medicine.

Effectiveness and Safety of Autologous Bone Marrow Stromal Cells Transplantation After Ischemic Stroke: A Meta-Analysis

BACKGROUND

Autologous bone marrow stromal cells (BM-SCs) transplantation might be a potential therapy for stroke. Although a series of clinical trials were performed to assess the effectiveness and safety of BM-SCs transplantation after ischemic stroke, the results are still conflicting. This study aimed to pool previous controlled trials to assess the effectiveness of BM-SCs-based cell therapy after ischemic stroke.

MATERIAL AND METHODS

Relevant studies were searched among online databases. Barthel index (BI) or modified Barthel index (mBI), National Institutes of Health Stroke Scale (NIHSS), and Rankin Score (mRS) were used to assess therapeutic effects. The frequencies of adverse events were extracted for assessing safety of stem cell therapy. Data analysis was performed by using Review Manager 5.3.

RESULTS

Patients who received cell therapy had significantly lower NIHSS score (-1.85) than the controls. In addition, there might be some benefits in daily activity measured by mBI, but this meta-analysis failed to demonstrate significant benefits of BM-SCs-based cell therapy in increasing the proportion of mRS ≤2 patients. We did not find any severe adverse events associated with BM-SCs-based cell therapy.

CONCLUSIONS

Although BM-MNCs/MSCs transplantation might generate some benefits in lowering the grade of impairment caused by ischemic stroke, large RCTs are required to further confirm the effectiveness of BM-MSCs/MNCs-based cell therapy and to optimize the conditions require for best therapeutic effects.

Genetic Cell Ablation Reveals Clusters of Local Self-Renewing Microglia in the Mammalian Central Nervous System

During early embryogenesis, microglia arise from yolk sac progenitors that populate the developing central nervous system (CNS), but how the tissue-resident macrophages are maintained throughout the organism's lifespan still remains unclear. Here, we describe a system that allows specific, conditional ablation of microglia in adult mice. We found that the microglial compartment was reconstituted within 1 week of depletion. Microglia repopulation relied on CNS-resident cells, independent from bone-marrow-derived precursors. During repopulation, microglia formed clusters of highly proliferative cells that migrated apart once steady state was achieved. Proliferating microglia expressed high amounts of the interleukin-1 receptor (IL-1R), and treatment with an IL-1R antagonist during the repopulation phase impaired microglia proliferation. Hence, microglia have the potential for efficient self-renewal without the contribution of peripheral myeloid cells, and IL-1R signaling participates in this restorative proliferation process.

Analyzing cell fusion events within the central nervous system using bone marrow chimerism

It has emerged that cells which typically reside in the bone marrow have the capacity to cross the blood brain barrier and contribute genetic material to a range of neuronal cell types within the central nervous system. One such mechanism to account for this phenomenon is cellular fusion, occurring between migrating bone marrow-derived stem cells and neuronal cells in-situ. Biologically, the significance as to why cells from distinct lineages fuse with cells of the central nervous system is, as yet, unclear. Growing evidence however suggests that these cell fusion events could provide an efficient means of rescuing the highly complex and differentiated neuronal cell types that cannot be replaced in adulthood. To facilitate further understanding of cell fusion within the central nervous system, we describe here a technique to establish chimeric mice that are stably reconstituted with green fluorescent protein expressing sex-mismatched bone marrow. These chimeric mice are known to represent an excellent model for studying bone marrow cell migration and infiltration throughout the body, while in parallel, as will be described here, also provide a means to neatly analyze both bone marrow-derived cell fusion and trans-differentiation events within the central nervous system.

Bioengineered fibrin-based niche to direct outgrowth of circulating progenitors into neuron-like cells for potential use in cellular therapy

OBJECTIVE

Autologous cells are considered to be the best choice for use in transplantation therapy. However, the challenges and risks associated with the harvest of transplantable autologous cells limit their successful therapeutic application. The current study explores the possibility of isolating neural progenitor cells from circulating multipotent adult progenitor cells for potential use in cell-based and patient-specific therapy for neurological diseases.

APPROACH

To enable the selection of neural progenitor cells from human peripheral blood mononuclear cells, and to support their lineage maintenance, the composition of a fibrin-based niche was optimized. Morphological examination and specific marker analysis were carried out, employing a qualitative/quantitative polymerase chain reaction followed by immunocytochemistry to: (i) characterize neural progenitor cells in culture; (ii) monitor proliferation/survival; and (iii) track their differentiation status.

MAIN RESULTS

The presence of neural progenitors in circulation was confirmed by the presence of nestin(+) cells at the commencement of the culture. The isolation, proliferation and differentiation of circulating neural progenitors to neuron-like cells were directed by the engineered niche. Neural cell isolation to near homogeneity was confirmed by the expression of β-III tubulin in ∼95% of cells, whereas microtubule associated protein-2 expression confirmed their ability to differentiate. The concentration of potassium chloride in the niche was found to favour neuron-like cell lengthening, cell-cell contact, and expressions of synaptophysin and tyrosine hydroxylase.

SIGNIFICANCE

The purpose of this research was to find out if peripheral blood could serve as a potential source of neural progenitors for cell based therapy. The study established that neural progenitors could be selectively isolated from peripheral blood mononuclear cells using a biomimetic niche. The selected cells could multiply and slowly differentiate into neuron-like cells. These neuron-like cells expressed functional proteins-tyrosine hydroxylase and synaptophysin. Early progenitors that proliferate while expressing β-III tubulin could be harvested from the culture, suggesting their potential use in cell transplantation therapy.

Neural differentiation of mouse bone marrow-derived mesenchymal stem cells treated with sex steroid hormones and basic fibroblast growth factor

Objective

There are several factors, like environmental agents, neurotrophic factors, serotonin and some hormones such as estrogen, affecting neurogenesis and neural differentiation. Regarding to importance of proliferation and regeneration in central nervous system, and a progressive increase in neurodegenerative diseases, cell therapy is an attractive approach in neuroscience. The aim of the present study was to investigate the effects of sex steroid hormones and basic fibroblast growth factor (bFGF) on neuronal differentiation of mouse bone marrow-derived mesenchymal stem cells (BM-MSCs).

Materials and Methods

This experimental study was established in Kharazmi Univer- sity. BM was isolated from the bones of femur and tibia of 4-6-week old Naval Medical Research Institute (NMRI) mice, and the cells were cultured. The cells were divided into following 4 groups based on the applied treatments: I. control (no treatment), II. steroid hormones (β-estradiol, progesterone and testosterone), III. bFGF and IV. combination of steroid hormones and bFGF. Immunocytochemistry and flow cytometery analyses were applied for beta III-tubulin (β-III tubulin) and microtubule-associated proteins-2 (MAP-2) in 4 days of treatment for all groups.

Results

The cells treated with combination of bFGF and steroid hormones represented more expressions of neural markers as compared to control and to other two groups treated with either bFGF or steroid hormones.

Conclusion

This study showed that BM-MSCs can express specific neural markers after receiving bFGF pretreatment that was followed by sex steroid hormones treatment. More investigations are necessary to specify whether steroid hormones and bFGF can be considered for treatment of CNS diseases and disorders.

Novel nano-composite biomimetic biomaterial allows chondrogenic and osteogenic differentiation of bone marrow concentrate derived cells

In clinical orthopedics suitable materials that induce and restore biological functions together with the right mechanical properties are particularly needed for the regeneration of osteochondral lesions. For this purpose, the ideal scaffold should possess the right properties with respect to degradation, cell binding, cellular uptake, non-immunogenicity, mechanical strength, and flexibility. In addition, it should be easy to handle and serve as a template for chondrocyte and bone cells guiding both cartilage and bone formation. The aim of the present study was to estimate the chondrogenic and osteogenic capability of bone marrow concentrated derived cells seeded onto a novel nano-composite biomimetic material. These properties have been evaluated by means of histological, immunohistochemical and electron microscopy analyses. The data obtained demonstrated that freshly harvested cells obtained from bone marrow were able, once seeded onto the biomaterial, to differentiate either down the chondrogenic and osteogenic pathways as evaluated by the expression and production of specific matrix molecules. These findings support the use, for the repair of osteochondral lesions, of this new nano-composite biomimetic material together with bone marrow derived cells in a "one step" transplantation procedure.

Bone marrow-derived, neural-like cells have the characteristics of neurons to protect the peripheral nerve in microenvironment

Effective repair of peripheral nerve defects is difficult because of the slow growth of new axonal growth. We propose that "neural-like cells" may be useful for the protection of peripheral nerve destructions. Such cells should prolong the time for the disintegration of spinal nerves, reduce lesions, and improve recovery. But the mechanism of neural-like cells in the peripheral nerve is still unclear. In this study, bone marrow-derived neural-like cells were used as seed cells. The cells were injected into the distal end of severed rabbit peripheral nerves that were no longer integrated with the central nervous system. Electromyography (EMG), immunohistochemistry, and transmission electron microscopy (TEM) were employed to analyze the development of the cells in the peripheral nerve environment. The CMAP amplitude appeared during the 5th week following surgery, at which time morphological characteristics of myelinated nerve fiber formation were observed. Bone marrow-derived neural-like cells could protect the disintegration and destruction of the injured peripheral nerve.

Bone marrow-derived mesenchymal stem cells differentiate into nerve-like cells in vitro after transfection with brain-derived neurotrophic factor gene

Bone marrow-derived mesenchymal stem cells can differentiate into a variety of adult cells. Brain-derived neurotrophic factor (BDNF) is briefly active during differentiation and induces mesenchymal stem cells to differentiate into nerve cells. In this study, we cloned human BDNF to generate a recombinant pcDNA3.1(-)-BDNF vector and transfected the vector into bone marrow-derived mesenchymal stem cells. We selected these cells with Geneticin-418 to obtain BDNF-BMSCs, which were induced with retinoic acid to obtain induced BDNF-BMSCs. The transfected cells displayed the typical morphology and surface antigen profile of fibroblasts and were observed to express clusters of differentiation 29, 44, and 90 (observed in matrix and stromal cells), but not clusters of differentiation 31, 34, and 45 (observed in red blood cells and endothelial cells), via flow cytometry. Enzyme-linked immunosorbent assays showed that transfected bone marrow-derived mesenchymal stem cells secreted more BDNF than non-transfected bone marrow-derived mesenchymal stem cells. Immunocytochemistry and real-time reverse transcription polymerase chain reaction analysis showed that non-induced BDNF-BMSCs maintained a higher proliferative capacity and expressed higher amounts of brain-derived neurotrophic factor, nestin, neuron-specific enolase, and glial fibrillary acid protein than non-transfected bone marrow-derived mesenchymal stem cells. An additional increase was observed in the induced BDNF-BMSCs compared to the non-induced BDNF-BMSCs. This expression profile is characteristic of neurocytes. Our data demonstrate that bone marrow-derived mesenchymal stem cells transfected with the BDNF gene can differentiate into nerve-like cells in vitro, which may enable the generation of sufficient quantities of nerve-like cells for treatment of neuronal diseases.

Adult neural stem cells: Long-term self-renewal, replenishment by the immune system, or both?

The current model of adult neurogenesis in mammals suggests that adult-born neurons are generated by stem cells that undergo long-term self-renewal, and that a lifetime supply of stem cells resides in the brain. In contrast, it has recently been demonstrated that adult-born neurons in crayfish are generated by precursors originating in the immune system. This is particularly interesting because studies done many years ago suggest that a similar mechanism might exist in rodents and humans, with bone marrow providing stem cells that can generate neurons. However, the relevance of these findings for natural mechanisms underlying adult neurogenesis in mammals is not clear, because of uncertainties at many levels. We argue here that the recent findings in crayfish send a strong signal to re-examine existing data from rodents and humans, and to design new experiments that will directly test the contributions of the immune system to adult neurogenesis in mammals.

Stem cell transplantation for treating spinal cord injury: A literature comparison between studies of stem cells obtained from various sources

OBJECTIVE:

To identify global research trends of stem cell transplantation for treating spinal cord injury using a bibliometric analysis of the Web of Science.

DATA RETRIEVAL:

We performed a bibliometric analysis of data retrievals for stem cell transplantation for treating spinal cord injury from 2002 to 2011 using the Web of Science.

SELECTION CRITERIA:

Inclusion criteria: (a) peer-reviewed articles on stem cell transplantation for treating spinal cord injury that were published and indexed in the Web of Science; (b) type of articles: original research articles, reviews, meeting abstracts, proceedings papers, book chapters, editorial material, and news items; and (c) year of publication: 2002–2011. Exclusion criteria: (a) articles that required manual searching or telephone access; (b) documents that were not published in the public domain; and (c) a number of corrected papers from the total number of articles.

MAIN OUTCOME MEASURES:

(1) Annual publication output; (2) distribution according to country; (3) distribution according to institution; (4) distribution according to journals; (5) distribution according to funding agencies; and (6) top cited articles over the last 10 years.

RESULTS:

Bone marrow mesenchymal stem cells and embryonic stem cells have been widely used for treating spinal cord injury. In total, 191 studies of bone marrow mesenchymal stem cell transplantation and 236 studies of embryonic stem cell transplantation for treating spinal cord injury appeared in the Web of Science from 2002 to 2011, and almost half of which were derived from American or Japanese authors and institutes. The number of studies of stem cell transplantation for treating spinal cord injury has gradually increased over the past 10 years. Most papers on stem cell transplantation for treating spinal cord injury appeared in journals with a particular focus on stem cell research, such as Stem Cells and Cell Transplantation. Although umbilical cord blood stem cells and adipose-derived stem cells have been studied for treating spinal cord injury, the number of published papers was much smaller, with only 21 and 17 records, respectively, in the Web of Science.

CONCLUSION:

Based on our analysis of the literature and research trends, we found that stem cells transplantation obtained from various sources have been studied for treating spinal cord injury; however, it is difficult for researchers to reach a consensus on this theme.

Novel Insights into NeuN: from Neuronal Marker to Splicing Regulator

Neuronal nuclei (NeuN) is a well-recognized "marker" that is detected exclusively in post-mitotic neurons and was initially identified through an immunological screen to produce neuron-specific antibodies. Immunostaining evidence indicates that NeuN is distributed in the nuclei of mature neurons in nearly all parts of the vertebrate nervous system. NeuN is highly conserved among species and is stably expressed during specific stages of development. Therefore, NeuN has been considered to be a reliable marker of mature neurons for the past two decades. However, this role has been challenged by recent studies indicating that NeuN staining is variable and even absent during certain diseases and specific physiological states. More importantly, despite the widespread use of the anti-NeuN antibody, the natural identity of the NeuN protein remained elusive for 17 years. NeuN was recently eventually identified as an epitope of Rbfox3, which is a novel member of the Rbfox1 family of splicing factors. This identification might provide a novel perspective on NeuN expression during both physiological and pathological conditions. This review summarizes the current progress on the biochemical identity and biological significance of NeuN and recommends caution when applying NeuN immunoreactivity as a definitive marker of mature neurons in certain diseases and specific physiological states.

Partial rescue of mucopolysaccharidosis type VII mice with a lifelong engraftment of allogeneic stem cells in utero

In utero hematopoietic cell transplantation (IUHCT) has been performed in Mucopolysaccharidosis Type VII (MPSVII) mice, but a lifelong engraftment of allogeneic donor cells has not been achieved. In this study, we sought to confirm a lifelong engraftment of allogeneic donor cells immunologically matched to the mother and to achieve partial rescue of phenotypes in the original MPSVII strain through IUHCT by intravenous injection. We performed in vitro fertilization in a MPSVII murine model and transferred affected embryos to ICR/B6-GFP surrogate mothers in cases where fetuses receiving IUHCT were all homozygous. Lineage-depleted cells from ICR/B6-GFP mice were injected intravenously at E14.5. Chimerism was confirmed by flow cytometry at 4 weeks after birth, and β-glucuronidase activity in serum and several phenotypes were assessed at 8 weeks of age or later. Donor cells in chimeric mice from ICR/B6-GFP mothers were detected at death, and were confirmed in several tissues including the brains of sacrificed chimeric mice. Although the serum enzyme activity of chimeric mice was extremely low, the engraftment rate of donor cells correlated with enzyme activity. Furthermore, improvement of bone structure and rescue of reproductive ability were confirmed in our limited preclinical study. We confirmed the lifelong engraftment of donor cells in an original immunocompetent MPSVII murine model using intravenous IUHCT with cells immunologically matched to the mother without myeloablation, and the improvement of several phenotypes.

Bone marrow transplantation for research and regenerative therapies in the central nervous system

Bone marrow stem cells are probably the best known stem cell type and have been employed for more than 50 years, especially in pathologies related to the hematopoietic and immune systems. However, their potential for therapeutic application is much broader (because these cells can differentiate into hepatocytes, myocytes, cardiomyocytes, pneumocytes or neural cells, among others), and they can also presumably be employed to palliate neural diseases. Current research addressing the integration of bone marrow -derived cells in the neural circuits of the central nervous system together with their features and applications are hotspots in current Neurobiology. Nevertheless, as in other leading research lines the efficacy and possibilities of their therapeutic application depend on the technical procedures employed, which are still far from being standardized. In this chapter we shall explain one of these procedures in depth, namely the transplantation of whole bone marrow from harvested bone marrow stem cells for subsequent integration into the encephalon.

Developing stem cell therapies for juvenile and adult-onset Huntington's disease

Stem cell therapies have been explored as a new avenue for the treatment of neurologic disease and damage within the CNS in part due to their native ability to mimic repair mechanisms in the brain. Mesenchymal stem cells have been of particular clinical interest due to their ability to release beneficial neurotrophic factors and their ability to foster a neuroprotective microenviroment. While early stem cell transplantation therapies have been fraught with technical and political concerns as well as limited clinical benefits, mesenchymal stem cell therapies have been shown to be clinically beneficial and derivable from nonembryonic, adult sources. The focus of this review will be on emerging and extant stem cell therapies for juvenile and adult-onset Huntington's disease.

Stem cell therapy in spinal trauma: Does it have scientific validity?

Stem cell-based interventions aim to use special regenerative cells (stem cells) to facilitate neuronal function beyond the site of the injury. Many studies involving animal models of spinal cord injury (SCI) suggest that certain stem cell-based therapies may restore function after SCI. Currently, in case of spinal cord injuries, new discoveries with clinical implications have been continuously made in basic stem cell research, and stem cell-based approaches are advancing rapidly toward application in patients. There is a huge base of preclinical evidence in vitro and in animal models which suggests the safety and clinical efficacy of cellular therapies after SCI. Despite this, data from clinical studies is not very encouraging and at times confounding. Here, we have attempted to cover preclinical and clinical evidence base dealing with safety, feasibility and efficacy of cell based interventions after SCI. The limitations of preclinical data and the reasons underlying its failure to translate in a clinical setting are also discussed. Based on the evidence base, it is suggested that a multifactorial approach is required to address this situation. Need for standardized, stringently designed multi-centric clinical trials for obtaining validated proof of evidence is also highlighted.

Foxc1 dependent mesenchymal signalling drives embryonic cerebellar growth

Loss of Foxc1 is associated with Dandy-Walker malformation, the most common human cerebellar malformation characterized by cerebellar hypoplasia and an enlarged posterior fossa and fourth ventricle. Although expressed in the mouse posterior fossa mesenchyme, loss of Foxc1 non-autonomously induces a rapid and devastating decrease in embryonic cerebellar ventricular zone radial glial proliferation and concurrent increase in cerebellar neuronal differentiation. Subsequent migration of cerebellar neurons is disrupted, associated with disordered radial glial morphology. In vitro, SDF1α, a direct Foxc1 target also expressed in the head mesenchyme, acts as a cerebellar radial glial mitogen and a chemoattractant for nascent Purkinje cells. Its receptor, Cxcr4, is expressed in cerebellar radial glial cells and conditional Cxcr4 ablation with Nes-Cre mimics the Foxc1-/- cerebellar phenotype. SDF1α also rescues the Foxc1-/- phenotype. Our data emphasizes that the head mesenchyme exerts a considerable influence on early embryonic brain development and its disruption contributes to neurodevelopmental disorders in humans.

Safety and neurological assessments after autologous transplantation of bone marrow mesenchymal stem cells in subjects with chronic spinal cord injury

Introduction

The administration of stem cells holds promise as a potential therapy for spinal cord injury (SCI). Mesenchymal stem cells have advantages for clinical applications, since they can be easily obtained, are suitable for autologous transplantation and have been previously shown to induce regeneration of the spinal cord in experimental settings. Here we evaluated the feasibility, safety and potential efficacy of autologous transplantation of mesenchymal stem cells in subjects with chronic complete SCI.

Method

We conducted a phase I, non-controlled study in 14 subjects of both genders aging between 18 to 65 years, with chronic traumatic SCI (>6 months), at thoracic or lumbar levels, classified as American Spinal Injury Association (ASIA) A - complete injury. Baseline somatosensory evoked potentials (SSEP), spinal magnetic resonance imaging (MRI) and urodynamics were assessed before and after treatment. Pain rating was performed using the McGill Pain Questionnaire and a visual analogue score scale. Bone marrow-derived mesenchymal stem cells were cultured and characterized by flow cytometry, cell differentiation assays and G-band karyotyping. Mesenchymal stem cells were injected directly into the lesion following laminectomy and durotomy.

Results

Cell transplantation was an overall safe and well-tolerated procedure. All subjects displayed variable improvements in tactile sensitivity and eight subjects developed lower limbs motor functional gains, principally in the hip flexors. Seven subjects presented sacral sparing and improved American Spinal Injury Association impairment scale (AIS) grades to B or C – incomplete injury. Nine subjects had improvements in urologic function. One subject presented changes in SSEP 3 and 6 months after mesenchymal stem cells transplantation. Statistically significant correlations between the improvements in neurological function and both injury size and level were found.

Conclusion

Intralesional transplantation of autologous mesenchymal stem cells in subjects with chronic, complete spinal cord injury is safe, feasible, and may promote neurological improvements.

Trial registration

ClinicalTrials.gov NCT01325103 – Registered 28 March 2011

Non-enzymatic dissociation of human mesenchymal stromal cells improves chemokine-dependent migration and maintains immunosuppressive function

BACKGROUND AIMS

Human bone marrow-derived mesenchymal stromal cells (MSC) can suppress inflammation; therefore their therapeutic potential is being explored in clinical trials. Poor engraftment of infused MSC limits their therapeutic utility; this may be caused by MSC processing before infusion, in particular the method of their detachment from culture.

METHODS

Enzymatic methods of detaching MSC (Accutase and TrypLE) were compared with non-enzymatic methods (Cell Dissociation Buffer [CDB], ethylenediamine tetra-acetic acid and scraping) for their effect on MSC viability, chemokine receptor expression, multi-potency, immunomodulation and chemokine-dependent migration.

RESULTS

TrypLE detachment preserved MSC viability and tri-lineage potential compared with non-enzymatic methods; however, this resulted in near complete loss of surface chemokine receptor expression. Of the non-enzymatic methods, CDB detachment preserved the highest viability while retaining significant tri-lineage differentiation potential. Once re-plated, CDB-detached MSC regained their original morphology and reached confluence, unlike with the use of other non-enzymatic methods. Viability was significantly reduced with the use of ethylenediamine tetra-acetic acid and further reduced with the use of cell scraping. Addition of 1% serum during CDB detachment led to higher MSC numbers entering autophagy and increased MSC recovery after re-plating. TrypLE and CDB-detached MSC suppressed CD3(+)CD4(+)CD25(-) T-cell proliferation, although TrypLE-detached MSC exhibited superior suppression at 1:20 ratio. CDB detachment retained surface chemokine receptor expression and consequently increased migration to CCL22, CXCL12 and CCL4, in contrast with TrypLE-detached MSC.

CONCLUSIONS

This study demonstrates that non-enzymatic detachment of MSC with the use of CDB minimizes the negative impact on cell viability, multipotency and immunomodulation while retaining chemokine-dependent migration, which may be of importance in MSC delivery and engraftment in sites of injury.

Cell fusion in the brain: two cells forward, one cell back

Adult stem cell populations, notably those which reside in the bone marrow, have been shown to contribute to several neuronal cell types in the rodent and human brain. The observation that circulating bone marrow cells can migrate into the central nervous system and fuse with, in particular, cerebellar Purkinje cells has suggested, at least in part, a potential mechanism behind this process. Experimentally, the incidence of cell fusion in the brain is enhanced with age, radiation exposure, inflammation, chemotherapeutic drugs and even selective damage to the neurons themselves. The presence of cell fusion, shown by detection of increased bi-nucleated neurons, has also been described in a variety of human central nervous system diseases, including both multiple sclerosis and Alzheimer’s disease. Accumulating evidence is therefore raising new questions into the biological significance of cell fusion, with the possibility that it represents an important means of cell-mediated neuroprotection or rescue of highly complex neurons that cannot be replaced in adult life. Here, we discuss the evidence behind this phenomenon in the rodent and human brain, with a focus on the subsequent research investigating the physiological mechanisms of cell fusion underlying this process. We also highlight how these studies offer new insights into endogenous neuronal repair, opening new exciting avenues for potential therapeutic interventions against neurodegeneration and brain injury.

Umbilical cord-derived mesenchymal stem cells retain immunomodulatory and anti-oxidative activities after neural induction

The immunomodulatory and anti-oxidative activities of differentiated mesenchymal stem cells contribute to their therapeutic efficacy in cell-replacement therapy. Mesenchymal stem cells were isolated from human umbilical cord and induced to differentiate with basic fibroblast growth factor, nerve growth factor, epidermal growth factor, brain-derived neurotrophic factor and forskolin. The mesenchymal stem cells became rounded with long processes and expressed the neural markers, Tuj1, neurofilament 200, microtubule-associated protein-2 and neuron-specific enolase. Nestin expression was significantly reduced after neural induction. The expression of immunoregulatory and anti-oxidative genes was largely unchanged prior to and after neural induction in mesenchymal stem cells. There was no significant difference in the effects of control and induced mesenchymal stem cells on lymphocyte proliferation in co-culture experiments. However, the expression of human leukocyte antigen-G decreased significantly in induced neuron-like cells. These results suggest that growth factor-based methods enable the differentiation of mesenchymal stem cell toward immature neuronal-like cells, which retain their immunomodulatory and anti-oxidative activities.

Stable transfection into rat bone marrow mesenchymal stem cells by lentivirus-mediated NT-3

Transplantation of bone marrow mesenchymal stem cells (BMSCs) is the most promising therapeutic strategy in the treatment of spinal cord injuries. BMSCs have a wide variety of sources and are characterized by being exempt from immune rejection, marked secretory functions and neuronal plasticity during differentiation. The lentiviral vector, namely PLV.Ex3d.P/neo-EF1A-NT3-internal ribosome entry site-enhanced green fluorescent protein, was constructed and subsequently transfected into Sprague Dawley (SD) rat BMSCs. The gene and protein expression levels of the nucleic acid neurotrophin-3 (NT-3) were then detected. The results demonstrated that the constructed NT-3 gene lentiviral expression vector matched the expected design and that the NT-3 gene was transfected into the BMSCs via the lentivirus‑mediated method at a transfection efficiency of 60‑70%. NT-3 gene expression was detected within the stably transfected positive cells at the nucleic acid and protein levels. The cell morphology and biological activity of BMSCs did not alter significantly following transfection with NT-3. NT-3-transfected SD BMSCs were successfully constructed and served as effective vector seed cells with stable expression. These results can be used as a reference for subsequent studies on the transplantation therapy of rat spinal cord injuries using lentivirus-mediated NT-3-transfected SD BMSCs.

Cells from the immune system generate adult-born neurons in crayfish

Neurogenesis is an ongoing process in the brains of adult decapod crustaceans. However, the first-generation precursors that produce adult-born neurons, which reside in a neurogenic niche, are not self-renewing in crayfish and must be replenished. The source of these neuronal precursors is unknown. Here, we report that adult-born neurons in crayfish can be derived from hemocytes. Following adoptive transfer of 5-ethynyl-2'-deoxyuridine (EdU)-labeled hemocytes, labeled cells populate the neurogenic niche containing the first-generation neuronal precursors. Seven weeks after adoptive transfer, EdU-labeled cells are located in brain clusters 9 and 10 (where adult-born neurons differentiate) and express appropriate neurotransmitters. Moreover, the number of cells composing the neurogenic niche in crayfish is tightly correlated with total hemocyte counts (THCs) and can be manipulated by raising or lowering THC. These studies identify hemocytes as a source of adult-born neurons in crayfish and demonstrate that the immune system is a key contributor to adult neurogenesis.

Therapeutic effect of bone marrow mesenchymal stem cells on cold stress induced changes in the hippocampus of rats

The present study aims to evaluate the effect of bone marrow mesenchymal stem cells on cold stress induced neuronal changes in hippocampal CA1 region of Wistar rats. Bone marrow mesenchymal stem cells were isolated from a 6-week-old Wistar rat. Bone marrow from adult femora and tibia was collected and mesenchymal stem cells were cultured in minimal essential medium containing 10% heat-inactivated fetal bovine serum and were sub-cultured. Passage 3 cells were analyzed by flow cytometry for positive expression of CD44 and CD90 and negative expression of CD45. Once CD44 and CD90 positive expression was achieved, the cells were cultured again to 90% confluence for later experiments. Twenty-four rats aged 8 weeks old were randomly and evenly divided into normal control, cold water swim stress (cold stress), cold stress + PBS (intravenous infusion), and cold stress + bone marrow mesenchymal stem cells (1 × 10(6); intravenous infusion) groups. The total period of study was 60 days which included 1 month stress period followed by 1 month treatment. Behavioral functional test was performed during the entire study period. After treatment, rats were sacrificed for histological studies. Treatment with bone marrow mesenchymal stem cells significantly increased the number of neuronal cells in hippocampal CA1 region. Adult bone marrow mesenchymal stem cells injected by intravenous administration show potential therapeutic effects in cognitive decline associated with stress-related lesions.