Astrocytes Derived from Familial and Sporadic Alzheimer's Disease iPSCs Show Altered Calcium Signaling and Respond Differently to Misfolded Protein Tau

Astrocytes regulate important functions in the brain, and their dysregulation has been linked to the etiology of neurodegenerative diseases, such as Alzheimer’s disease (AD). The role of astroglia in human AD remains enigmatic, owing to the limitations of animal models, which, while recreating some pathological aspects of the disease, do not fully mirror its course. In addition, the recognition of major structural and functional differences between human and mouse astrocytes has also prompted research into human glial cells. In the current study, astrocytes were generated using human iPSCs from patients with sporadic Alzheimer’s disease (sAD), familial Alzheimer’s disease (fAD) and non-demented controls (NDC). All clones gained astrocyte-specific morphological and proteomic characteristics upon in vitro differentiation, without considerable inter-clonal variances. In comparison to NDC, AD astrocytes displayed aberrant calcium dynamics in response to glutamate. When exposed to monomeric and aggregated tau, AD astrocytes demonstrated hypertrophy and elevated GFAP expression, differential expression of select signaling and receptor proteins, and the enhanced production of metalloproteinases (MMPs). Moreover, astrocytic secretomes were able to degrade tau in both monomeric and pathologically aggregated forms, which was mediated by MMP-2 and -9. The capacity to neutralize tau varied considerably between clones, with fAD astrocytes having the lowest degradability relative to sAD and healthy astrocytes. Importantly, when compared to aggregated tau alone, astrocytic secretome pretreatment of tau differentially reduced its detrimental effects on neurons. Our results show crucial differences in sporadic and familial AD astrocytes and suggests that these cells may play distinctive roles in the pathogenesis of early and late onset Alzheimer’s disease.

Corrigendum: Mesenchymal Stem Cells in Treatment of Spinal Cord Injury and Amyotrophic Lateral Sclerosis

[This corrects the article DOI: 10.3389/fcell.2021.695900.].

Mesenchymal Stem Cells in Treatment of Spinal Cord Injury and Amyotrophic Lateral Sclerosis

Preclinical and clinical studies with various stem cells, their secretomes, and extracellular vesicles (EVs) indicate their use as a promising strategy for the treatment of various diseases and tissue defects, including neurodegenerative diseases such as spinal cord injury (SCI) and amyotrophic lateral sclerosis (ALS). Autologous and allogenic mesenchymal stem cells (MSCs) are so far the best candidates for use in regenerative medicine. Here we review the effects of the implantation of MSCs (progenitors of mesodermal origin) in animal models of SCI and ALS and in clinical studies. MSCs possess multilineage differentiation potential and are easily expandable in vitro. These cells, obtained from bone marrow (BM), adipose tissue, Wharton jelly, or even other tissues, have immunomodulatory and paracrine potential, releasing a number of cytokines and factors which inhibit the proliferation of T cells, B cells, and natural killer cells and modify dendritic cell activity. They are hypoimmunogenic, migrate toward lesion sites, induce better regeneration, preserve perineuronal nets, and stimulate neural plasticity. There is a wide use of MSC systemic application or MSCs seeded on scaffolds and tissue bridges made from various synthetic and natural biomaterials, including human decellularized extracellular matrix (ECM) or nanofibers. The positive effects of MSC implantation have been recorded in animals with SCI lesions and ALS. Moreover, promising effects of autologous as well as allogenic MSCs for the treatment of SCI and ALS were demonstrated in recent clinical studies.

Stem Cell Conditioned Medium Treatment for Canine Spinal Cord Injury: Pilot Feasibility Study

Spinal cord injury (SCI) involves nerve damage and often leads to motor, sensory and autonomic dysfunctions. In the present study, we have designed a clinical protocol to assess the feasibility of systemic delivery of allogenic canine bone marrow tissue-derived mesenchymal stem cell conditioned medium (BMMSC CM) to dogs with SCI. Four client-owned dogs with chronic SCI lasting more than six months underwent neurological and clinical evaluation, MRI imaging and blood tests before being enrolled in this study. All dogs received four intravenous infusions with canine allogenic BMMSC CM within one month. Between the infusions the dogs received comprehensive physiotherapy, which continued for three additional months. No adverse effects or complications were observed during the one, three and six months follow-up periods. Neither blood chemistry panel nor hematology profile showed any significant changes. All dogs were clinically improved as assessed using Olby locomotor scales after one, three and six months of BMMSC CM treatment. Furthermore, goniometric measurements revealed partial improvement in the range of joint motion. Bladder function improved in two disabled dogs. We conclude that multiple delivery of allogenic cell-derived conditioned medium to dogs with chronic SCI is feasible, and it might be clinically beneficial in combination with physiotherapy.

Chronic alcohol consumption alters extracellular space geometry and transmitter diffusion in the brain

Already moderate alcohol consumption has detrimental long-term effects on brain function. However, how alcohol produces its potent addictive effects despite being a weak reinforcer is a poorly understood conundrum that likely hampers the development of successful interventions to limit heavy drinking. In this translational study, we demonstrate widespread increased mean diffusivity in the brain gray matter of chronically drinking humans and rats. These alterations appear soon after drinking initiation in rats, persist into early abstinence in both species, and are associated with a robust decrease in extracellular space tortuosity explained by a microglial reaction. Mathematical modeling of the diffusivity changes unveils an increased spatial reach of extrasynaptically released transmitters like dopamine that may contribute to alcohol's progressively enhanced addictive potency.

Metabolic Changes in Focal Brain Ischemia in Rats Treated With Human Induced Pluripotent Stem Cell-Derived Neural Precursors Confirm the Beneficial Effect of Transplanted Cells

There is currently no treatment for restoring lost neurological function after stroke. A growing number of studies have highlighted the potential of stem cells. However, the mechanisms underlying their beneficial effect have yet to be explored in sufficient detail. In this study, we transplanted human induced pluripotent stem cell-derived neural precursors (iPSC-NPs) in rat temporary middle cerebral artery occlusion (MCAO) model. Using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) we monitored the effect of cells and assessed lesion volume and metabolite changes in the brain. We monitored concentration changes of myo-inositol (Ins), Taurine (Tau), Glycerophosphocholine+Phosphocholine (GPC+PCh), N-acetyl-aspartate+N-acetyl-aspartyl-glutamate (NAA+NAAG), Creatine+Phosphocreatine (Cr+PCr), and Glutamate+Glutamine (Glu+Gln) in the brains of control and iPSC-NP-transplanted rats. Based on initial lesion size, animals were divided into small lesion and big lesion groups. In the small lesion control group (SCL), lesion size after 4 months was three times smaller than initial measurements. In the small lesion iPSC-NP-treated group, lesion volume decreased after 1 month and then increased after 4 months. Although animals with small lesions significantly improved their motor skills after iPSC-NP transplantation, animals with big lesions showed no improvement. However, our MRI data demonstrate that in the big lesion iPSC-NP-treated (BTL) group, lesion size increased only up until 1 month after MCAO induction and then decreased. In contrast, in the big lesion control group, lesion size increased throughout the whole experiment. Significantly higher concentrations of Ins, Tau, GPC+PCh, NAA+NAAG, Cr+PCr, and Glu+Gln were found in in contralateral hemisphere in BTL animals 4 months after cell injection. Lesion volume decreased at this time point. Spectroscopic results of metabolite concentrations in lesion correlated with volumetric measurements of lesion, with the highest negative correlation observed for NAA+NAAG. Altogether, our results suggest that iPSC-NP transplantation decreases lesion volume and regulates metabolite concentrations within the normal range expected in healthy tissue. Further research into the ability of iPSC-NPs to differentiate into tissue-specific neurons and its effect on the long-term restoration of lesioned tissue is necessary.

Neuroprotective Potential of Cell-Based Therapies in ALS: From Bench to Bedside

Motor neurons (MN) degeneration is a main feature of amyotrophic lateral sclerosis (ALS), a neurological disorder with a progressive course. The diagnosis of ALS is essentially a clinical one. Most common symptoms include a gradual neurological deterioration that reflect the impairment and subsequent loss of muscle functions. Up-to-date ALS has no therapy that would prevent or cure a disease. Modern therapeutic strategies comprise of neuroprotective treatment focused on antiglutamatergic, antioxidant, antiapoptotic, and anti-inflammatory molecules. Stem cells application and gene therapy has provided researchers with a powerful tool for discovery of new mechanisms and therapeutic agents, as well as opened new perspectives for patients and family members. Here, we review latest progress made in basic, translational and clinical stem cell research related to the ALS. We overviewed results of preclinical and clinical studies employing cell-based therapy to treat neurodegenerative disorders. A special focus has been made on the neuroprotective properties of adult mesenchymal stromal cells (MSC) application into ALS patients. Finally, we overviewed latest progress in the field of embryonic and induced pluripotent stem cells used for the modeling and application during neurodegeneration in general and in ALS in particular.

Highly Efficient Neural Conversion of Human Pluripotent Stem Cells in Adherent and Animal-Free Conditions

Neural differentiation of human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) can produce a valuable and robust source of human neural cell subtypes, holding great promise for the study of neurogenesis and development, and for treating neurological diseases. However, current hESCs and hiPSCs neural differentiation protocols require either animal factors or embryoid body formation, which decreases efficiency and yield, and strongly limits medical applications. Here we develop a simple, animal-free protocol for neural conversion of both hESCs and hiPSCs in adherent culture conditions. A simple medium formula including insulin induces the direct conversion of >98% of hESCs and hiPSCs into expandable, transplantable, and functional neural progenitors with neural rosette characteristics. Further differentiation of neural progenitors into dopaminergic and spinal motoneurons as well as astrocytes and oligodendrocytes indicates that these neural progenitors retain responsiveness to instructive cues revealing the robust applicability of the protocol in the treatment of different neurodegenerative diseases. The fact that this protocol includes animal-free medium and human extracellular matrix components avoiding embryoid bodies makes this protocol suitable for the use in clinic. Stem Cells Translational Medicine 2017;6:1217-1226.

A Comparative Study of Three Different Types of Stem Cells for Treatment of Rat Spinal Cord Injury

Three different sources of human stem cells-bone marrow-derived mesenchymal stem cells (BM-MSCs), neural progenitors (NPs) derived from immortalized spinal fetal cell line (SPC-01), and induced pluripotent stem cells (iPSCs)-were compared in the treatment of a balloon-induced spinal cord compression lesion in rats. One week after lesioning, the rats received either BM-MSCs (intrathecally) or NPs (SPC-01 cells or iPSC-NPs, both intraspinally), or saline. The rats were assessed for their locomotor skills (BBB, flat beam test, and rotarod). Morphometric analyses of spared white and gray matter, axonal sprouting, and glial scar formation, as well as qPCR and Luminex assay, were conducted to detect endogenous gene expression, while inflammatory cytokine levels were performed to evaluate the host tissue response to stem cell therapy. The highest locomotor recovery was observed in iPSC-NP-grafted animals, which also displayed the highest amount of preserved white and gray matter. Grafted iPSC-NPs and SPC-01 cells significantly increased the number of growth-associated protein 43 (GAP43+) axons, reduced astrogliosis, downregulated Casp3 expression, and increased IL-6 and IL-12 levels. hMSCs transiently decreased levels of inflammatory IL-2 and TNF-α. These findings correlate with the short survival of hMSCs, while NPs survived for 2 months and matured slowly into glia- and tissue-specific neuronal precursors. SPC-01 cells differentiated more in astroglial phenotypes with a dense structure of the implant, whereas iPSC-NPs displayed a more neuronal phenotype with a loose structure of the graft. We concluded that the BBB scores of iPSC-NP- and hMSC-injected rats were superior to the SPC-01-treated group. The iPSC-NP treatment of spinal cord injury (SCI) provided the highest recovery of locomotor function due to robust graft survival and its effect on tissue sparing, reduction of glial scarring, and increased axonal sprouting.

Injectable Extracellular Matrix Hydrogels as Scaffolds for Spinal Cord Injury Repair

Restoration of lost neuronal function after spinal cord injury (SCI) still remains a big challenge for current medicine. One important repair strategy is bridging the SCI lesion with a supportive and stimulatory milieu that would enable axonal rewiring. Injectable extracellular matrix (ECM)-derived hydrogels have been recently reported to have neurotrophic potential in vitro. In this study, we evaluated the presumed neuroregenerative properties of ECM hydrogels in vivo in the acute model of SCI. ECM hydrogels were prepared by decellularization of porcine spinal cord (SC) or porcine urinary bladder (UB), and injected into a spinal cord hemisection cavity. Histological analysis and real-time qPCR were performed at 2, 4, and 8 weeks postinjection. Both types of hydrogels integrated into the lesion and stimulated neovascularization and axonal ingrowth into the lesion. On the other hand, massive infiltration of macrophages into the lesion and rapid hydrogel degradation did not prevent cyst formation, which progressively developed over 8 weeks. No significant differences were found between SC-ECM and UB-ECM. Gene expression analysis revealed significant downregulation of genes related to immune response and inflammation in both hydrogel types at 2 weeks post SCI. A combination of human mesenchymal stem cells with SC-ECM did not further promote ingrowth of axons and blood vessels into the lesion, when compared with the SC-ECM hydrogel alone. In conclusion, both ECM hydrogels bridged the lesion cavity, modulated the innate immune response, and provided the benefit of a stimulatory substrate for in vivo neural tissue regeneration. However, fast hydrogel degradation might be a limiting factor for the use of native ECM hydrogels in the treatment of acute SCI.

hiPSC Disease Modeling of Rare Hereditary Cerebellar Ataxias: Opportunities and Future Challenges

Cerebellar ataxias are clinically and genetically heterogeneous diseases affecting primary cerebellar cells. The lack of availability of affected tissue from cerebellar ataxias patients is the main obstacle in investigating the pathogenicity of these diseases. The landmark discovery of human-induced pluripotent stem cells (hiPSC) has permitted the derivation of patient-specific cells with an unlimited self-renewing capacity. Additionally, their potential to differentiate into virtually any cell type of the human organism allows for large amounts of affected cells to be generated in culture, converting this hiPSC technology into a revolutionary tool in the study of the mechanisms of disease, drug discovery, and gene correction. In this review, we will summarize the current studies in which hiPSC were utilized to study cerebellar ataxias. Describing the currently available 2D and 3D hiPSC-based cellular models, and due to the fact that extracerebellar cells were used to model these diseases, we will discuss whether or not they represent a faithful cellular model and whether they have contributed to a better understanding of disease mechanisms.

Human Multipotent Mesenchymal Stromal Cells in the Treatment of Postoperative Temporal Bone Defect: An Animal Model

Canal wall down mastoidectomy is one of the most effective treatments for cholesteatoma. However, it results in anatomical changes in the external and middle ear with a negative impact on the patient's quality of life. To provide complete closure of the mastoid cavity and normalize the anatomy of the middle and external ear, we used human multipotent mesenchymal stromal cells (hMSCs), GMP grade, in a guinea pig model. A method for preparing a biomaterial composed of hMSCs, hydroxyapatite, and tissue glue was developed. Animals from the treated group were implanted with biomaterial composed of hydroxyapatite and hMSCs, while animals in the control group received hydroxyapatite alone. When compared to controls, the group implanted with hMSCs showed a significantly higher ratio of new bone formation ( p = 0.00174), as well as a significantly higher volume percentage of new immature bone ( p = 0.00166). Our results proved a beneficial effect of hMSCs on temporal bone formation and provided a promising tool to improve the quality of life of patients after canal wall down mastoidectomy by hMSC implantation.

Sodium-calcium exchanger and R-type Ca(2+) channels mediate spontaneous [Ca(2+)]i oscillations in magnocellular neurones of the rat supraoptic nucleus

Isolated supraoptic neurones generate spontaneous [Ca(2+)]i oscillations in isolated conditions. Here we report in depth analysis of the contribution of plasmalemmal ion channels (Ca(2+), Na(+)), Na(+)/Ca(2+) exchanger (NCX), intracellular Ca(2+) release channels (InsP3Rs and RyRs), Ca(2+) storage organelles, plasma membrane Ca(2+) pump and intracellular signal transduction cascades into spontaneous Ca(2+) activity. While removal of extracellular Ca(2+) or incubation with non-specific voltage-gated Ca(2+) channel (VGCC) blocker Cd(2+) suppressed the oscillations, neither Ni(2+) nor TTA-P2, the T-type VGCC blockers, had an effect. Inhibitors of VGCC nicardipine, ω-conotoxin GVIA, ω-conotoxin MVIIC, ω-agatoxin IVA (for L-, N-, P and P/Q-type channels, respectively) did not affect [Ca(2+)]i oscillations. In contrast, a specific R-type VGCC blocker SNX-482 attenuated [Ca(2+)]i oscillations. Incubation with TTX had no effect, whereas removal of the extracellular Na(+) or application of an inhibitor of the reverse operation mode of Na(+)/Ca(2+) exchanger KB-R7943 blocked the oscillations. The mitochondrial uncoupler CCCP irreversibly blocked spontaneous [Ca(2+)]i activity. Exposure of neurones to Ca(2+) mobilisers (thapsigargin, cyclopiazonic acid, caffeine and ryanodine); 4-aminopyridine (A-type K(+) current blocker); phospholipase C and adenylyl cyclase pathways blockers U-73122, Rp-cAMP, SQ-22536 and H-89 had no effect. Oscillations were blocked by GABA, but not by glutamate, apamin or dynorphin. In conclusion, spontaneous oscillations in magnocellular neurones are mediated by a concerted action of R-type Ca(2+) channels and the NCX fluctuating between forward and reverse modes.

Physiology of spontaneous [Ca(2+)]i oscillations in the isolated vasopressin and oxytocin neurones of the rat supraoptic nucleus

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Supraoptic fluorescent vasopressin (AVP-eGFP) and oxytocin (OT-mRFP1) neurones exhibit distinct spontaneous [Ca²⁺]_i oscillations.

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Vasopressin triggers [Ca²⁺]_i oscillations, intensifies existing oscillations, and exceptionally stops oscillations.

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Hyper- or hypo-osmotic stimuli have an intensifying or inhibitory effect on oscillations, respectively.

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Nearly 90% of neurones from 3 or 5-day-dehydrated rats exhibit oscillations.

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More than 80% of OT-mRFP1 neurones from 3 to 6-day-lactating rats are oscillatory vs. about 44% in virgins.

The magnocellular vasopressin (AVP) and oxytocin (OT) neurones exhibit specific electrophysiological behaviour, synthesise AVP and OT peptides and secrete them into the neurohypophysial system in response to various physiological stimulations. The activity of these neurones is regulated by the very same peptides released either somato-dendritically or when applied to supraoptic nucleus (SON) preparations in vitro. The AVP and OT, secreted somato-dendritically (i.e. in the SON proper) act through specific autoreceptors, induce distinct Ca²⁺ signals and regulate cellular events. Here, we demonstrate that about 70% of freshly isolated individual SON neurones from the adult non-transgenic or transgenic rats bearing AVP (AVP-eGFP) or OT (OT-mRFP1) markers, produce distinct spontaneous [Ca²⁺]_i oscillations. In the neurones identified (through specific fluorescence), about 80% of AVP neurones and about 60% of OT neurones exhibited these oscillations. Exposure to AVP triggered [Ca²⁺]_i oscillations in silent AVP neurones, or modified the oscillatory pattern in spontaneously active cells. Hyper- and hypo-osmotic stimuli (325 or 275 mOsmol/l) respectively intensified or inhibited spontaneous [Ca²⁺]_i dynamics. In rats dehydrated for 3 or 5 days almost 90% of neurones displayed spontaneous [Ca²⁺]_i oscillations. More than 80% of OT-mRFP1 neurones from 3 to 6-day-lactating rats were oscillatory vs. about 44% (OT-mRFP1 neurones) in virgins. Together, these results unveil for the first time that both AVP and OT neurones maintain, via Ca²⁺ signals, their remarkable intrinsic in vivo physiological properties in an isolated condition.

Specific profiles of ion channels and ionotropic receptors define adipose- and bone marrow derived stromal cells

Adherent, fibroblastic cells from different tissues are thought to contain subsets of tissue-specific stem/progenitor cells (often called mesenchymal stem cells). These cells display similar cell surface characteristics based on their fibroblastic nature, but also exhibit differences in molecular phenotype, growth rate, and their ability to differentiate into various cell phenotypes. The mechanisms underlying these differences remain poorly understood. We analyzed Ca(2+) signals and membrane properties in rat adipose-derived stromal cells (ADSCs) and bone marrow stromal cells (BMSCs) in basal conditions, and then following a switch into medium that contains factors known to modify their character. Modified ADSCs (mADSCs) expressed L-type Ca(2+) channels whereas both L- and P/Q- channels were operational in mBMSCs. Both mADSCs and mBMSCs possessed functional endoplasmic reticulum Ca(2+) stores, expressed ryanodine receptor-1 and -3, and exhibited spontaneous [Ca(2+)]i oscillations. The mBMSCs expressed P2X7 purinoceptors; the mADSCs expressed both P2X (but not P2X7) and P2Y (but not P2Y1) receptors. Both types of stromal cells exhibited [Ca(2+)]i responses to vasopressin (AVP) and expressed V1 type receptors. Functional oxytocin (OT) receptors were, in contrast, expressed only in modified ADSCs and BMSCs. AVP and OT-induced [Ca(2+)]i responses were dose-dependent and were blocked by their respective specific receptor antagonists. Electrophysiological data revealed that passive ion currents dominated the membrane conductance in ADSCs and BMSCs. Medium modification led to a significant shift in the reversal potential of passive currents from -40 to -50mV in cells in basal to -80mV in modified cells. Hence membrane conductance was mediated by non-selective channels in cells in basal conditions, whereas in modified medium conditions, it was associated with K(+)-selective channels. Our results indicate that modification of ADSCs and BMSCs by alteration in medium formulation is associated with significant changes in their Ca(2+) signaling and membrane properties.

Mesenchymal Stem Cells Preserve Working Memory in the 3xTg-AD Mouse Model of Alzheimer's Disease

The transplantation of stem cells may have a therapeutic effect on the pathogenesis and progression of neurodegenerative disorders. In the present study, we transplanted human mesenchymal stem cells (MSCs) into the lateral ventricle of a triple transgenic mouse model of Alzheimer´s disease (3xTg-AD) at the age of eight months. We evaluated spatial reference and working memory after MSC treatment and the possible underlying mechanisms, such as the influence of transplanted MSCs on neurogenesis in the subventricular zone (SVZ) and the expression levels of a 56 kDa oligomer of amyloid β (Aβ*56), glutamine synthetase (GS) and glutamate transporters (Glutamate aspartate transporter (GLAST) and Glutamate transporter-1 (GLT-1)) in the entorhinal and prefrontal cortices and the hippocampus. At 14 months of age we observed the preservation of working memory in MSC-treated 3xTg-AD mice, suggesting that such preservation might be due to the protective effect of MSCs on GS levels and the considerable downregulation of Aβ*56 levels in the entorhinal cortex. These changes were observed six months after transplantation, accompanied by clusters of proliferating cells in the SVZ. Since the grafted cells did not survive for the whole experimental period, it is likely that the observed effects could have been transiently more pronounced at earlier time points than at six months after cell application.

Transfer of mesenchymal stem cells and cyclosporine A on alkali-injured rabbit cornea using nanofiber scaffolds strongly reduces corneal neovascularization and scar formation

The aim of this study was to examine whether nanofiber scaffolds seeded with rabbit bone marrow mesenchymal stem cells (MSCs nanofibers) transferred onto the damaged corneal surface and covered with cyclosporine A (CsA)-loaded nanofiber scaffolds (CsA nanofibers) enable healing of the rabbit cornea injured with 1N NaOH. The healing of damaged corneas was examined morphologically, immunohistochemically and biochemically on day 24 after the injury. Compared to untreated injured corneas, where corneal ulceration or large corneal thinning or even perforation were developed, injured corneas treated with drug free nanofibers healed without profound disturbances in a majority of cases, although with fibrosis and scar formation. In injured corneas treated with CsA nanofibers or MSCs nanofibers, the development of scar formation was reduced. Best healing results were obtained with a combination of MSCs and CsA nanofibers (MSCs-CsA nanofibers). Corneas healed with highly restored transparency. Neovascularization highly expressed in untreated injured corneas and reduced in corneas treated with CsA nanofibers or MSCs nanofibers, was suppressed in corneas treated with MSCs-CsA nanofibers. The levels of matrix metalloproteinase 9, inducible nitric oxide synthase, interleukin 6, α-smooth muscle actin, tumor growth factor β and vascular endothelial growth factor were significantly decreased in these corneas as compared to untreated corneas, where the levels of the above mentioned markers were high. In conclusion, MSCs-CsA nanofibers were effective in the treatment of severe alkali-induced corneal injury.

Concise review: reactive astrocytes and stem cells in spinal cord injury: good guys or bad guys?

Spinal cord injury (SCI) usually results in long lasting locomotor and sensory neuron degeneration below the injury. Astrocytes normally play a decisive role in mechanical and metabolic support of neurons, but in the spinal cord they cause injury, exerting well-known detrimental effects that contribute to glial scar formation and inhibition of axon outgrowth. Cell transplantation is considered a promising approach for replacing damaged cells and promoting neuroprotective and neuroregenerative repair, but the effects of the grafted cells on local tissue and the regenerative properties of endogenous neural stem cells in the injured spinal cord are largely unknown. During the last 2 decades cumulative evidence from diverse animal models has indicated that reactive astrocytes in synergy with transplanted cells could be beneficial for injury in multiple ways, including neuroprotection and axonal growth. In this review, we specifically focus on the dual opposing roles of reactive astrocytes in SCI and how they contribute to the creation of a permissive environment when combined with transplanted cells as the influential components for a local regenerative niche. Modulation of reactive astrocyte function might represent an extremely attractive new therapy to enhance the functional outcomes in patients.

Comparison of intraspinal and intrathecal implantation of induced pluripotent stem cell-derived neural precursors for the treatment of spinal cord injury in rats

Background

Stem cell treatment provides a promising therapy for patients with spinal cord injury (SCI). However, the applied stem cells exert their effects in different manners that are dependent on the route used for administration.

Methods

In the present study, we administered neural precursors derived from induced pluripotent stem cells (iPS-NPs) either intraspinally into the lesion center or intrathecally into the subarachnoid space of rats with a balloon-induced spinal cord compression lesion. Functional locomotor performance, cell survival, astrogliosis, axonal sprouting and the expression of endogenous neurotrophic growth factors were evaluated using behavioral tests (BBB, flat beam test, rotarod, plantar test), morphometric analysis, immunohistochemistry and qPCR.

Results

Both treatments facilitated the functional locomotor recovery of rats with SCI. iPS-NPs injected intraspinally survived well for 2 months and were positive for MAP2, while cells grafted intrathecally were undetectable at the site of administration or in the spinal cord tissue. Intraspinal implantation increased gray and white matter sparing and axonal sprouting and reduced astrogliosis, while intrathecal application resulted only in an improvement of white matter sparing and an increase in axonal sprouting, in parallel with no positive effect on the expression of endogenous neurotrophic growth factor genes or glial scar reduction.

Conclusions

Intrathecally grafted iPS-NPs had a moderate therapeutic benefit on SCI through a paracrine mechanism that does not require the cells to be present in the tissue; however, the extended survival of i.s. grafted cells in the spinal cord may promote long-term spinal cord tissue regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0255-2) contains supplementary material, which is available to authorized users.

Intrathecal delivery of mesenchymal stromal cells protects the structure of altered perineuronal nets in SOD1 rats and amends the course of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder resulting in a lethal outcome. We studied changes in ventral horn perineuronal nets (PNNs) of superoxide dismutase 1 (SOD1) rats during the normal disease course and after the intrathecal application (5 × 10⁵ cells) of human bone marrow mesenchymal stromal cells (MSCs) postsymptom manifestation. We found that MSCs ameliorated disease progression, significantly improved motor activity, and prolonged survival. For the first time, we report that SOD1 rats have an abnormal disorganized PNN structure around the spinal motoneurons and give different expression profiles of chondroitin sulfate proteoglycans (CSPGs), such as versican, aggrecan, and phosphacan, but not link protein-1. Additionally, SOD1 rats had different profiles for CSPG gene expression (Versican, Hapln1, Neurocan, and Tenascin-R), whereas Aggrecan and Brevican profiles remained unchanged. The application of MSCs preserved PNN structure, accompanied by better survival of motorneurons. We measured the concentration of cytokines (IL-1α, MCP-1, TNF-α, GM-CSF, IL-4, and IFN-γ) in the rats' cerebrospinal fluid and found significantly higher concentrations of IL-1α and MCP-1. Our results show that PNN and cytokine homeostasis are altered in the SOD1 rat model of ALS. These changes could potentially serve as biological markers for the diagnosis, assessment of treatment efficacy, and prognosis of ALS. We also show that the administration of human MSCs is a safe procedure that delays the loss of motor function and increases the overall survival of symptomatic ALS animals, by remodeling the recipients' pattern of gene expression and having neuroprotective and immunomodulatory effects. Stem Cells2014;32:3163–3172

The impact of silica encapsulated cobalt zinc ferrite nanoparticles on DNA, lipids and proteins of rat bone marrow mesenchymal stem cells

Nanomaterials are currently the subject of intense research due to their wide variety of potential applications in the biomedical, optical and electronic fields. We prepared and tested cobalt zinc ferrite nanoparticles (Co0.5Zn0.5Fe2O4+γ [CZF-NPs]) encapsulated by amorphous silica in order to find a safe contrast agent and magnetic label for tracking transplanted cells within an organism using magnetic resonance imaging (MRI). Rat mesenchymal stem cells (rMSCs) were labeled for 48 h with a low, medium or high dose of CZF-NPs (0.05; 0.11 or 0.55 mM); silica NPs (Si-NPs; 0.11 mM) served as a positive control. The internalization of NPs into cells was verified by transmission electron microscopy. Biological effects were analyzed at the end of exposure and after an additional 72 h of cell growth without NPs. Compared to untreated cells, Annexin V/Propidium Iodide labeling revealed no significant cytotoxicity for any group of treated cells and only a high dose of CZF-NPs slowed down cell proliferation and induced DNA damage, manifested as a significant increase of DNA-strand breaks and oxidized DNA bases. This was accompanied by high concentrations of 15-F2t-isoprostane and carbonyl groups, demonstrating oxidative injury to lipids and proteins, respectively. No harmful effects were detected in cells exposed to the low dose of CZF-NPs. Nevertheless, the labeled cells still exhibited an adequate relaxation rate for MRI in repeated experiments and ICP-MS confirmed sufficient magnetic label concentrations inside the cells. The results suggest that the silica-coated CZF-NPs, when applied at a non-toxic dose, represent a promising contrast agent for cell labeling.

Alzheimer's Disease: Mechanism and Approach to Cell Therapy

Alzheimer’s disease (AD) is the most common form of dementia. The risk of AD increases with age. Although two of the main pathological features of AD, amyloid plaques and neurofibrillary tangles, were already recognized by Alois Alzheimer at the beginning of the 20th century, the pathogenesis of the disease remains unsettled. Therapeutic approaches targeting plaques or tangles have not yet resulted in satisfactory improvements in AD treatment. This may, in part, be due to early-onset and late-onset AD pathogenesis being underpinned by different mechanisms. Most animal models of AD are generated from gene mutations involved in early onset familial AD, accounting for only 1% of all cases, which may consequently complicate our understanding of AD mechanisms. In this article, the authors discuss the pathogenesis of AD according to the two main neuropathologies, including senescence-related mechanisms and possible treatments using stem cells, namely mesenchymal and neural stem cells.

Role of Serum Levels of Angiogenic Cytokines in Assessment of Angiogenesis after Stem Cell Therapy of Diabetic Patients with Critical Limb Ischemia

The release of proangiogenic cytokines into the circulation after stem cell (SC) therapy and compensatory increase of angiogenesis inhibitors may reflect local vasculogenesis but also can increase the risk of side effects. The aim of our study was to evaluate serum levels of angiogenic cytokines with regard to the assessment of local and systemic vasculogenesis in diabetic patients with no-option critical limb ischemia (NO-CLI). Twenty-five diabetic patients with NO-CLI treated with SCs isolated from bone marrow or stimulated peripheral blood were included in the study. Serum levels of proangiogenic cytokines (VEGF, bFGF, Ang-1, PDGF-AA, and PDGF-BB) and an antiangiogenic cytokine (endostatin) were assessed 6 months after cell treatment, compared to baseline values, and correlated with the number of injected CD34+ cells. The clinical effect of SC therapy (assessed by changes in TcPO2) and potential systemic vasculogenesis (assessed by eye fundus examination) were evaluated after 6 months. Serum levels of angiogenic inhibitor endostatin increased significantly after 1 and 3 months ( p = 0.0003), but no significant increase in serum levels of proangiogenic cytokines was observed. A significant correlation between number of injected CD34+ cells and serum levels of endostatin was observed ( r = 0.41, p < 0.05); however, proangiogenic cytokines did not correlate with CD34+ cells. No correlation between increase in TcPO2 after treatment and serum levels of any of the angiogenic cytokines were seen, and no signs of systemic vasculogenesis in the retina were observed after 6 months. Despite the significant increase in the levels of the angiogenic inhibitor endostatin following SC treatment, there was no risk of systemic vasculogenesis after SC therapy as documented by serum levels of proangiogenic cytokines or changes in the retina.

Beneficial Effect of Human Induced Pluripotent Stem Cell-Derived Neural Precursors in Spinal Cord Injury Repair

Despite advances in our understanding and research of induced pluripotent stem cells (iPSCs), their use in clinical practice is still limited due to lack of preclinical experiments. Neural precursors (NPs) derived from a clone of human iPSCs (IMR90) were used to treat a rat spinal cord lesion 1 week after induction. Functional recovery was evaluated using the BBB, beam walking, rotarod, and plantar tests. Lesion morphology, endogenous axonal sprouting, graft survival, and iPSC-NP differentiation were analyzed immunohistochemically. Quantitative polymerase chain reaction (qPCR) was used to evaluate the effect of transplanted iPSC-NPs on endogenous regenerative processes and also to monitor their behavior after transplantation. Human iPSC-NPs robustly survived in the lesion, migrated, and partially filled the lesion cavity during the entire period of observation. Transplanted animals displayed significant motor improvement already from the second week after the transplantation of iPSC-NPs. qPCR revealed the increased expression of human neurotrophins 8 weeks after transplantation. Simultaneously, the white and gray matter were spared in the host tissue. The grafted cells were immunohistochemically positive for doublecortin, MAP2, βIII-tubulin, GFAP, and CNPase 8 weeks after transplantation. Human iPSC-NPs further matured, and 17 weeks after transplantation differentiated toward interneurons, dopaminergic neurons, serotoninergic neurons, and ChAT-positive motoneurons. Human iPSC-NPs possess neurotrophic properties that are associated with significant early functional improvement and the sparing of spinal cord tissue. Their ability to differentiate into tissue-specific neurons leads to the long-term restoration of the lesioned tissue, making the cells a promising candidate for future cell-based therapy of SCI.

Getting it right before transplantation: example of a stem cell model with regenerative potential for the CNS

The burden of neurodegenerative disorders in an aging population has become a challenge for the modern world. While the biomarkers available and the methods of diagnosis have improved to detect the onset of these diseases at early stages, the question of adapted and efficient therapies is still a major issue. The prospect of replacing the loss of functional neural cells remains an attractive but still audacious approach. A huge progress has been made in the generation of neurons derived from human stem cell lines and transplantation assays are tested in animals for a wide range of pathologies of the central nervous system. Here we take one step back and examine neuronal differentiation and the characterization of neural progenitors derived from human embryonic stem cells. We gather results from our previous studies and present a cell model that was successfully used in functional analyses and engraftment experiments. These neuronal precursors exhibit spontaneous and evoked activity, indicating that their electrophysiological and calcium handling properties are similar to those of matured neurons. Hence this summarized information will serve as a basis to design better stem cell-based therapies to improve neural regeneration.

Human multipotent mesenchymal stem cells improve healing after collagenase tendon injury in the rat

Background

Mesenchymal stromal cells attract much interest in tissue regeneration because of their capacity to differentiate into mesodermal origin cells, their paracrine properties and their possible use in autologous transplantations. The aim of this study was to investigate the safety and reparative potential of implanted human mesenchymal stromal cells (hMSCs), prepared under Good Manufacturing Practice (GMP) conditions utilizing human mixed platelet lysate as a culture supplement, in a collagenase Achilles tendon injury model in rats.

Methods

Eighty-one rats with collagenase-induced injury were divided into two groups. The first group received human mesenchymal stromal cells injected into the site of injury 3 days after lesion induction, while the second group received saline. Biomechanical testing, morphometry and semiquantitative immunohistochemistry of collagens I, II and III, versican and aggrecan, neovascularization, and hMSC survival were performed 2, 4, and 6 weeks after injury.

Results

Human mesenchymal stromal cell-treated rats had a significantly better extracellular matrix structure and a larger amount of collagen I and collagen III. Neovascularization was also increased in hMSC-treated rats 2 and 4 weeks after tendon injury. MTCO2 (Cytochrome c oxidase subunit II) positivity confirmed the presence of hMSCs 2, 4 and 6 weeks after transplantation. Collagen II deposits and alizarin red staining for bone were found in 6 hMSC- and 2 saline-treated tendons 6 weeks after injury. The intensity of anti-versican and anti-aggrecan staining did not differ between the groups.

Conclusions

hMSCs can support tendon healing through better vascularization as well as through larger deposits and better organization of the extracellular matrix. The treatment procedure was found to be safe; however, cartilage and bone formation at the implantation site should be taken into account when planning subsequent in vivo and clinical trials on tendinopathy as an expected adverse event.

Regenerative medicine for the treatment of spinal cord injury: more than just promises?

Spinal cord injury triggers a complex set of events that lead to tissue healing without the restoration of normal function due to the poor regenerative capacity of the spinal cord. Nevertheless, current knowledge about the intrinsic regenerative ability of central nervous system axons, when in a supportive environment, has made the prospect of treating spinal cord injury a reality. Among the range of strategies under investigation, cell-based therapies offer the most promising results, due to the multifactorial roles that these cells can fulfil. However, the best cell source is still a matter of debate, as are clinical issues that include the optimal cell dose as well as the timing and route of administration. In this context, the role of biomaterials is gaining importance. These can not only act as vehicles for the administered cells but also, in the case of chronic lesions, can be used to fill the permanent cyst, thus creating a more favourable and conducive environment for axonal regeneration in addition to serving as local delivery systems of therapeutic agents to improve the regenerative milieu. Some of the candidate molecules for the future are discussed in view of the knowledge derived from studying the mechanisms that facilitate the intrinsic regenerative capacity of central nervous system neurons. The future challenge for the multidisciplinary teams working in the field is to translate the knowledge acquired in basic research into effective combinatorial therapies to be applied in the clinic.

Suppression of alkali-induced oxidative injury in the cornea by mesenchymal stem cells growing on nanofiber scaffolds and transferred onto the damaged corneal surface

The purpose of this study was to investigate whether rabbit bone marrow-derived mesenchymal stem cells (MSCs) effectively decrease alkali-induced oxidative stress in the rabbit cornea. The alkali (0.15 N NaOH) was applied on the corneas of the right eyes and then rinsed with tap water. In the first group of rabbits the injured corneas remained untreated. In the second group MSCs were applied on the injured corneal surface immediately after the injury and eyelids sutured for two days. Then the sutures were removed. In the third group nanofiber scaffolds seeded with MSCs (and in the fourth group nanofibers alone) were transferred onto the corneas immediately after the injury and the eyelids sutured. Two days later the eyelid sutures were removed together with the nanofiber scaffolds. The rabbits were sacrificed on days four, ten or fifteen after the injury, and the corneas were examined immunohistochemically, morphologically, for the central corneal thickness (taken as an index of corneal hydration) using an ultrasonic pachymeter and by real-time PCR. Results show that in untreated injured corneas the expression of malondialdehyde (MDA) and nitrotyrosine (NT) (important markers of lipid peroxidation and oxidative stress) appeared in the epithelium. The antioxidant aldehyde dehydrogenase 3A1 (ALDH3A1) decreased in the corneal epithelium, particularly in superficial parts, where apoptotic cell death (detected by active caspase-3) was high. (In control corneal epithelium MDA and NT are absent and ALDH3A1 highly present in all layers of the epithelium. Cell apoptosis are sporadic). In injured untreated cornea further corneal disturbances developed: The expressions of matrix metalloproteinase 9 (MMP9) and proinflammatory cytokines, were high. At the end of experiment (on day 15) the injured untreated corneas were vascularized and numerous inflammatory cells were present in the corneal stroma. Vascular endothelial growth factor (VEGF) expression and number of macrophages were high. The results obtained in injured corneas covered with nanofiber scaffolds alone (without MSCs) or in injured corneas treated with MSCs only (transferred without scaffolds) did not significantly differ from the results found in untreated injured corneas. In contrast, in the injured corneas treated with MSCs on nanofiber scaffolds, ALDH3A1 expression remained high in the epithelium (as in the control cornea) and positive expression of the other immunohistochemical markers employed was very low (MMP9) or absent (NT, MDA, proinflammatory cytokines), also similarly as in the control cornea. Corneal neovascularization and the infiltration of the corneal stroma with inflammatory cells were significantly suppressed in the injured corneas treated with MSCs compared to the untreated injured ones. The increased central corneal thickness together with corneal opalescency appearing after alkali injury returned to normal levels over the course of ten days only in the injured corneas treated with MSCs on nanofiber scaffolds. The expression of genes for the proinflammatory cytokines corresponded with their immunohistochemical expression. In conclusion, MSCs on nanofiber scaffolds protected the formation of toxic peroxynitrite (detected by NT residues), lowered apoptotic cell death and decreased matrix metalloproteinase and pro-inflammatory cytokine production. This resulted in reduced corneal inflammation as well as neovascularization and significantly accelerated corneal healing.

The impact of alpha-syntrophin deletion on the changes in tissue structure and extracellular diffusion associated with cell swelling under physiological and pathological conditions

Aquaporin-4 (AQP4) is the primary cellular water channel in the brain and is abundantly expressed by astrocytes along the blood-brain barrier and brain-cerebrospinal fluid interfaces. Water transport via AQP4 contributes to the activity-dependent volume changes of the extracellular space (ECS), which affect extracellular solute concentrations and neuronal excitability. AQP4 is anchored by α-syntrophin (α-syn), the deletion of which leads to reduced AQP4 levels in perivascular and subpial membranes. We used the real-time iontophoretic method and/or diffusion-weighted magnetic resonance imaging to clarify the impact of α-syn deletion on astrocyte morphology and changes in extracellular diffusion associated with cell swelling in vitro and in vivo. In mice lacking α-syn, we found higher resting values of the apparent diffusion coefficient of water (ADCW) and the extracellular volume fraction (α). No significant differences in tortuosity (λ) or non-specific uptake (k'), were found between α-syn-negative (α-syn -/-) and α-syn-positive (α-syn +/+) mice. The deletion of α-syn resulted in a significantly smaller relative decrease in α observed during elevated K(+) (10 mM) and severe hypotonic stress (-100 mOsmol/l), but not during mild hypotonic stress (-50 mOsmol/l). After the induction of terminal ischemia/anoxia, the final values of ADCW as well as of the ECS volume fraction α indicate milder cell swelling in α-syn -/- in comparison with α-syn +/+ mice. Shortly after terminal ischemia/anoxia induction, the onset of a steep rise in the extracellular potassium concentration and an increase in λ was faster in α-syn -/- mice, but the final values did not differ between α-syn -/- and α-syn +/+ mice. This study reveals that water transport through AQP4 channels enhances and accelerates astrocyte swelling. The substantially altered ECS diffusion parameters will likely affect the movement of neuroactive substances and/or trophic factors, which in turn may modulate the extent of tissue damage and/or drug distribution.

Both autologous bone marrow mononuclear cell and peripheral blood progenitor cell therapies similarly improve ischaemia in patients with diabetic foot in comparison with control treatment

BACKGROUND

The aim of our study was to compare the effect of bone marrow mononuclear cell and peripheral blood progenitor cell therapies in patients with diabetic foot disease and critical limb ischaemia unresponsive to revascularization with conservative therapy.

METHODS

Twenty-eight patients with diabetic foot disease (17 treated by bone marrow cells and 11 by peripheral blood cell) were included into an active group and 22 patients into a control group without cell treatment. Transcutaneous oxygen pressure and rate of major amputation, as the main outcome measures, were compared between bone marrow cells, peripheral blood cell and control groups over 6 months; both cell therapy methods were also compared by the characteristics of cell suspensions. Possible adverse events were evaluated by changes of serum levels of angiogenic cytokines and retinal fundoscopic examination.

RESULTS

The transcutaneous oxygen pressure increased significantly (p < 0.05) compared with baseline in both active groups after 6 months, with no significant differences between bone marrow cells and peripheral blood cell groups; however, no change of transcutaneous oxygen pressure in the control group was observed. The rate of major amputation by 6 months was significantly lower in the active cell therapy group compared with that in the control group (11.1% vs. 50%, p = 0.0032), with no difference between bone marrow cells and peripheral blood cell. A number of injected CD34+ cells and serum levels of angiogenic cytokines after treatment did not significantly differ between bone marrow cells and peripheral blood cell.

CONCLUSIONS

Our study showed a superior benefit of bone marrow cells and peripheral blood cell treatments of critical limb ischaemia in patients with diabetic foot disease when compared with conservative therapy. There was no difference between both cell therapy groups, and no patient demonstrated signs of systemic vasculogenesis.

Conditionally immortalized stem cell lines from human spinal cord retain regional identity and generate functional V2a interneurons and motorneurons

Introduction

The use of immortalized neural stem cells either as models of neural development in vitro or as cellular therapies in central nervous system (CNS) disorders has been controversial. This controversy has centered on the capacity of immortalized cells to retain characteristic features of the progenitor cells resident in the tissue of origin from which they were derived, and the potential for tumorogenicity as a result of immortalization. Here, we report the generation of conditionally immortalized neural stem cell lines from human fetal spinal cord tissue, which addresses these issues.

Methods

Clonal neural stem cell lines were derived from 10-week-old human fetal spinal cord and conditionally immortalized with an inducible form of cMyc. The derived lines were karyotyped, transcriptionally profiled by microarray, and assessed against a panel of spinal cord progenitor markers with immunocytochemistry. In addition, the lines were differentiated and assessed for the presence of neuronal fate markers and functional calcium channels. Finally, a clonal line expressing eGFP was grafted into lesioned rat spinal cord and assessed for survival, differentiation characteristics, and tumorogenicity.

Results

We demonstrate that these clonal lines (a) retain a clear transcriptional signature of ventral spinal cord progenitors and a normal karyotype after extensive propagation in vitro, (b) differentiate into relevant ventral neuronal subtypes with functional T-, L-, N-, and P/Q-type Ca²⁺ channels and spontaneous calcium oscillations, and (c) stably engraft into lesioned rat spinal cord without tumorogenicity.

Conclusions

We propose that these cells represent a useful tool both for the in vitro study of differentiation into ventral spinal cord neuronal subtypes, and for examining the potential of conditionally immortalized neural stem cells to facilitate functional recovery after spinal cord injury or disease.

Human conditionally immortalized neural stem cells improve locomotor function after spinal cord injury in the rat

Introduction

A growing number of studies have highlighted the potential of stem cell and more-differentiated neural cell transplantation as intriguing therapeutic approaches for neural repair after spinal cord injury (SCI).

Methods

A conditionally immortalized neural stem cell line derived from human fetal spinal cord tissue (SPC-01) was used to treat a balloon-induced SCI. SPC-01 cells were implanted into the lesion 1 week after SCI. To determine the feasibility of tracking transplanted stem cells, a portion of the SPC-01 cells was labeled with poly-L-lysine-coated superparamagnetic iron-oxide nanoparticles, and the animals grafted with labeled cells underwent magnetic resonance imaging. Functional recovery was evaluated by using the BBB and plantar tests, and lesion morphology, endogenous axonal sprouting and graft survival, and differentiation were analyzed. Quantitative polymerase chain reaction (qPCR) was used to evaluate the effect of transplanted SPC-01 cells on endogenous regenerative processes.

Results

Transplanted animals displayed significant motor and sensory improvement 2 months after SCI, when the cells robustly survived in the lesion and partially filled the lesion cavity. qPCR revealed the increased expression of rat and human neurotrophin and motor neuron genes. The grafted cells were immunohistologically positive for glial fibrillary acidic protein (GFAP); however, we found 25% of the cells to be positive for Nkx6.1, an early motor neuron marker. Spared white matter and the robust sprouting of growth-associated protein 43 (GAP43)⁺ axons were found in the host tissue. Four months after SCI, the grafted cells matured into Islet2⁺ and choline acetyltransferase (ChAT)⁺ neurons, and the graft was grown through with endogenous neurons. Grafted cells labeled with poly-L-lysine-coated superparamagnetic nanoparticles before transplantation were detected in the lesion on T₂-weighted images as hypointense spots that correlated with histologic staining for iron and the human mitochondrial marker MTCO2.

Conclusions

The transplantation of SPC-01 cells produced significant early functional improvement after SCI, suggesting an early neurotrophic action associated with long-term restoration of the host tissue, making the cells a promising candidate for future cell therapy in patients with SCI.

Plasticity of calcium signaling cascades in human embryonic stem cell-derived neural precursors

Human embryonic stem cell-derived neural precursors (hESC NPs) are considered to be a promising tool for cell-based therapy in central nervous system injuries and neurodegenerative diseases. The Ca(2+) ion is an important intracellular messenger essential for the regulation of various cellular functions. We investigated the role and physiology of Ca(2+) signaling to characterize the functional properties of CCTL14 hESC NPs during long-term maintenance in culture (in vitro). We analyzed changes in cytoplasmic Ca(2+) concentration ([Ca(2+)]i) evoked by high K(+), adenosine-5'-triphosphate (ATP), glutamate, γ-aminobutyric acid (GABA), and caffeine in correlation with the expression of various neuronal markers in different passages (P6 through P10) during the course of hESC differentiation. We found that only differentiated NPs from P7 exhibited significant and specific [Ca(2+)]i responses to various stimuli. About 31% of neuronal-like P7 NPs exhibited spontaneous [Ca(2+)]i oscillations. Pharmacological and immunocytochemical assays revealed that P7 NPs express L- and P/Q-type Ca(2+) channels, P2X2, P2X3, P2X7, and P2Y purinoreceptors, glutamate receptors, and ryanodine (RyR1 and RyR3) receptors. The ATP- and glutamate-induced [Ca(2+)]i responses were concentration-dependent. Higher glutamate concentrations (over 100 μM) caused cell death. Responses to ATP were observed in the presence or in the absence of extracellular Ca(2+). These results emphasize the notion that with time in culture, these cells attain a transient period of operative Ca(2+) signaling that is predictive of their ability to act as stem elements.

Stem cells in regenerative medicine

BACKGROUND

A number of cardiovascular, neurological, musculoskeletal and other diseases have a limited capacity for repair and only a modest progress has been made in treatment of brain diseases. The discovery of stem cells has opened new possibilities for the treatment of these maladies, and cell therapy now stands at the cutting-edge of modern regenerative medicine and tissue engineering. Experimental data and the first clinical trials employing stem cells have shown their broad therapeutic potential and have brought hope to patients suffering from devastating pathologies of different organs and systems.

AIMS

Here, we briefly review the main achievements and trends in cell-based therapy, with an emphasis on the main types of stem cells: embryonic, mesenchymal stromal and induced pluripotent cells.

DISCUSSION

Many questions regarding the application of stem cells remain unanswered, particularly tumorigenicity, immune rejection and danger of gene manipulation. Currently, only MSC seems to be safe and might be considered to be a leading candidate for human application to treat pathologies that affect the cardiovascular, neurological and musculoskeletal systems.

Stem cells in regenerative medicine

BACKGROUND

A number of cardiovascular, neurological, musculoskeletal and other diseases have a limited capacity for repair and only a modest progress has been made in treatment of brain diseases. The discovery of stem cells has opened new possibilities for the treatment of these maladies, and cell therapy now stands at the cutting-edge of modern regenerative medicine and tissue engineering. Experimental data and the first clinical trials employing stem cells have shown their broad therapeutic potential and have brought hope to patients suffering from devastating pathologies of different organs and systems.

AIMS

Here, we briefly review the main achievements and trends in cell-based therapy, with an emphasis on the main types of stem cells: embryonic, mesenchymal stromal and induced pluripotent cells.

DISCUSSION

Many questions regarding the application of stem cells remain unanswered, particularly tumorigenicity, immune rejection and danger of gene manipulation. Currently, only MSC seems to be safe and might be considered to be a leading candidate for human application to treat pathologies that affect the cardiovascular, neurological and musculoskeletal systems.

Controlled gentamicin release from multi-layered electrospun nanofibrous structures of various thicknesses

Polyvinyl alcohol nanofibers incorporating the wide spectrum antibiotic gentamicin were prepared by Nanospider™ needleless technology. A polyvinyl alcohol layer, serving as a drug reservoir, was covered from both sides by polyurethane layers of various thicknesses. The multilayered structure of the nanofibers was observed using scanning electron microscopy, the porosity was characterized by mercury porosimetry, and nitrogen adsorption/desorption measurements were used to determine specific surface areas. The stability of the gentamicin released from the electrospun layers was proved by high-performance liquid chromatography (HPLC) and inhibition of bacterial growth. Drug release was investigated using in vitro experiments with HPLC/MS quantification, while the antimicrobial efficacy was evaluated on Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Both experiments proved that the released gentamicin retained its activity and showed that the retention of the drug in the nanofibers was prolonged with the increasing thickness of the covering layers.

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.

The extracellular matrix and diffusion barriers in focal cortical dysplasias

Focal cortical dysplasias (FCDs) of the brain are recognized as a frequent cause of intractable epilepsy. To contribute to the current understanding of the mechanisms of epileptogenesis in FCD, our study provides evidence that not only cellular alterations and synaptic transmission, but also changed diffusion properties of the extracellular space (ECS), induced by modified extracellular matrix (ECM) composition and astrogliosis, might be involved in the generation or spread of seizures in FCD. The composition of the ECM in FCD and non-malformed cortex (in 163 samples from 62 patients) was analyzed immunohistochemically and correlated with the corresponding ECS diffusion parameter values determined with the real-time iontophoretic method in freshly resected cortex (i.e. the ECS volume fraction and the geometrical factor tortuosity, describing the hindrances to diffusion in the ECS). The ECS in FCD was shown to differ from that in non-malformed cortex, mainly by the increased accumulation of certain ECM molecules (tenascin R, tenascin C, and versican) or by their reduced expression (brevican), and by the presence of an increased number of astrocytic processes. The consequent increase of ECS diffusion barriers observed in both FCD type I and II (and, at the same time, the enlargement of the ECS volume in FCD type II) may alter the diffusion of neuroactive substances through the ECS, which mediates one of the important modes of intercellular communication in the brain - extrasynaptic volume transmission. Thus, the changed ECM composition and altered ECS diffusion properties might represent additional factors contributing to epileptogenicity in FCD.

The use of dopamine-hyaluronate associate-coated maghemite nanoparticles to label cells

Sodium hyaluronate (HA) was associated with dopamine (DPA) and introduced as a coating for maghemite (γ-Fe₂O₃) nanoparticles obtained by the coprecipitation of iron(II) and iron(III) chlorides and oxidation with sodium hypochlorite. The effects of the DPA anchorage of HA on the γ-Fe₂O₃ surface on the physicochemical properties of the resulting colloids were investigated. Nanoparticles coated at three different DPA-HA/γ-Fe₂O₃ and DPA/HA ratios were chosen for experiments with rat bone marrow mesenchymal stem cells and human chondrocytes. The nanoparticles were internalized into rat bone marrow mesenchymal stem cells via endocytosis as confirmed by Prussian Blue staining. The efficiency of mesenchymal stem cell labeling was analyzed. From among the investigated samples, efficient cell labeling was achieved by using DPA-HA-γ-Fe₂O₃ nanoparticles with DPA-HA/γ-Fe₂O₃ = 0.45 (weight/ weight) and DPA/HA = 0.038 (weight/weight) ratios. The particles were used as a contrast agent in magnetic resonance imaging for the labeling and visualization of cells.

Bral1: "Superglue" for the extracellular matrix in the brain white matter

Bral1 is a link protein that stabilizes the binding between lecticans and hyaluronic acid and thus maintains the extracellular matrix assembly in the CNS. Bral1 is specifically located in the white matter around the nodes of Ranvier. Recent studies suggest its function in promoting saltatory neural conduction. This article reviews the current knowledge about the structure, expression and function of this link protein.

Oxidative damage to biological macromolecules in human bone marrow mesenchymal stromal cells labeled with various types of iron oxide nanoparticles

The biological effects of several superparamagnetic iron oxide nanoparticles (SPIONs) varying in their surface coating were tested using human bone marrow mesenchymal stromal cells from two donors - hBMSCs-1 and hBMSCs-2. The measurements were performed at two intervals - after 72 h exposure to the nanoparticles and after an additional 72 h cell growth without nanoparticles. The dose of SPIONs used (15.4 μg Fe/ml) was selected as being sufficient for in vivo cell tracking using magnetic resonance imaging (MRI). Concerning cell viability and cell death, only the hBMSCs-2 seemed to be sensitive to the action of SPIONs. However, an increase of oxidative injury to lipids, proteins and DNA as a consequence of exposure to SPIONs was detected in cells from both donors. Particularly the levels of lipid peroxidation were high and increased further with time, regardless of the type of nanoparticle. Lowering intracellular label concentrations and authenticating oxidative stress levels using in vivo experiments are required to ensure the safety of SPIONs for biomedical applications.

Cyclosporine A-loaded and stem cell-seeded electrospun nanofibers for cell-based therapy and local immunosuppression

Cyclosporine A (CsA), a potent immunosuppressive drug with low water solubility, was dissolved in poly(L-lactic acid) (PLA) solution, and nanofibers were fabricated from this mixture by electrospinning technology. The addition of CsA into the PLA solution and the conditions of the electrospinning process did not influence the structure of the nanofibers nor affect the pharmacological activity of CsA. Study of the CsA release behavior in culture medium showed a release for at least 96 h. After the topical application of CsA-loaded nanofibers on skin allografts in vivo, the release was significantly slower and about 35% of the drug was still retained in the nanofibers on day 8. The addition of CsA-loaded nanofibers into cultures of mouse spleen cells stimulated with Concanavalin A selectively inhibited T cell functions; the activity of stimulated macrophages or the growth of non-T-cell populations was not suppressed in the presence of CsA-loaded nanofibers. The covering of skin allografts with CsA-loaded nanofibers significantly attenuated the local production of the proinflammatory cytokines IL-2, IFN-γ and IL-17. These results suggest that CsA-loaded electrospun nanofibers can serve as effective drug carriers for the local/topical suppression of an inflammatory reaction and simultaneously could be used as scaffolds for cell-based therapy.