Cellular composition of long-term human spinal cord- and forebrain-derived neurosphere cultures

In Vitro Study of Human Immune Responses to Hyaluronic Acid Hydrogels, Recombinant Spidroins and Human Neural Progenitor Cells of Relevance to Spinal Cord Injury Repair

Scaffolds of recombinant spider silk protein (spidroin) and hyaluronic acid (HA) hydrogel hold promise in combination with cell therapy for spinal cord injury. However, little is known concerning the human immune response to these biomaterials and grafted human neural stem/progenitor cells (hNPCs). Here, we analyzed short- and long-term in vitro activation of immune cells in human peripheral blood mononuclear cells (hPBMCs) cultured with/without recombinant spidroins, HA hydrogels, and/or allogeneic hNPCs to assess potential host-donor interactions. Viability, proliferation and phenotype of hPBMCs were analyzed using NucleoCounter and flow cytometry. hPBMC viability was confirmed after exposure to the different biomaterials. Short-term (15 h) co-cultures of hPBMCs with spidroins, but not with HA hydrogel, resulted in a significant increase in the proportion of activated CD69+ CD4+ T cells, CD8+ T cells, B cells and NK cells, which likely was caused by residual endotoxins from the Escherichia coli expression system. The observed spidroin-induced hPBMC activation was not altered by hNPCs. It is resource-effective to evaluate human compatibility of novel biomaterials early in development of the production process to, when necessary, make alterations to minimize rejection risk. Here, we present a method to evaluate biomaterials and hPBMC compatibility in conjunction with allogeneic human cells.

Transplantation of Human Neural Precursor Cells Reverses Syrinx Growth in a Rat Model of Post-Traumatic Syringomyelia

Posttraumatic syringomyelia (PTS) is a serious condition of progressive expansion of spinal cord cysts, affecting patients with spinal cord injury years after injury. To evaluate neural cell therapy to prevent cyst expansion and potentially replace lost neurons, we developed a rat model of PTS. We combined contusive trauma with subarachnoid injections of blood, causing tethering of the spinal cord to the surrounding vertebrae, resulting in chronically expanding cysts. The cysts were usually located rostral to the injury, extracanalicular, lined by astrocytes. T2*-weighted magnetic resonance imaging (MRI) showed hyperintense fluid-filled cysts but also hypointense signals from debris and iron-laden macrophages/microglia. Two types of human neural stem/progenitor cells-fetal neural precursor cells (hNPCs) and neuroepithelial-like stem cells (hNESCs) derived from induced pluripotent stem cells-were transplanted to PTS cysts. Cells transplanted into cysts 10 weeks after injury survived at least 10 weeks, migrated into the surrounding parenchyma, but did not differentiate during this period. The cysts were partially obliterated by the cells, and cyst walls often merged with thin layers of cells in between. Cyst volume measurements with MRI showed that the volumes continued to expand in sham-transplanted rats by 102%, while the cyst expansion was effectively prevented by hNPCs and hNESCs transplantation, reducing the cyst volumes by 18.8% and 46.8%, respectively. The volume reductions far exceeded the volume of the added human cells. Thus, in an animal model closely mimicking the clinical situation, we provide proof-of-principle that transplantation of human neural stem/progenitor cells can be used as treatment for PTS.

Effect of Long-Term 3D Spheroid Culture on WJ-MSC

The aim of our work was to develop a protocol enabling a derivation of mesenchymal stem/stromal cell (MSC) subpopulation with increased expression of pluripotent and neural genes. For this purpose we used a 3D spheroid culture system optimal for neural stem cells propagation. Although 2D culture conditions are typical and characteristic for MSC, under special treatment these cells can be cultured for a short time in 3D conditions. We examined the effects of prolonged 3D spheroid culture on MSC in hope to select cells with primitive features. Wharton Jelly derived MSC (WJ-MSC) were cultured in 3D neurosphere induction medium for about 20 days in vitro. Then, cells were transported to 2D conditions and confront to the initial population and population constantly cultured in 2D. 3D spheroids culture of WJ-MSC resulted in increased senescence, decreased stemness and proliferation. However long-termed 3D spheroid culture allowed for selection of cells exhibiting increased expression of early neural and SSEA4 markers what might indicate the survival of cell subpopulation with unique features.

Human ex vivo spinal cord slice culture as a useful model of neural development, lesion, and allogeneic neural cell therapy

Background

There are multiple promising treatment strategies for central nervous system trauma and disease. However, to develop clinically potent and safe treatments, models of human-specific conditions are needed to complement in vitro and in vivo animal model-based studies.

Methods

We established human brain stem and spinal cord (cross- and longitudinal sections) organotypic cultures (hOCs) from first trimester tissues after informed consent by donor and ethical approval by the Regional Human Ethics Committee, Stockholm (lately referred to as Swedish Ethical Review Authority), and The National Board of Health and Welfare, Sweden. We evaluated the stability of hOCs with a semi-quantitative hOC score, immunohistochemistry, flow cytometry, Ca²⁺ signaling, and electrophysiological analysis. We also applied experimental allogeneic human neural cell therapy after injury in the ex vivo spinal cord slices.

Results

The spinal cord hOCs presented relatively stable features during 7–21 days in vitro (DIV) (except a slightly increased cell proliferation and activated glial response). After contusion injury performed at 7 DIV, a significant reduction of the hOC score, increase of the activated caspase-3⁺ cell population, and activated microglial populations at 14 days postinjury compared to sham controls were observed. Such elevation in the activated caspase-3⁺ population and activated microglial population was not observed after allogeneic human neural cell therapy.

Conclusions

We conclude that human spinal cord slice cultures have potential for future structural and functional studies of human spinal cord development, injury, and treatment strategies.

Optimized Clump Culture Methods for Adult Human Multipotent Neural Cells

Adult human multipotent neural cell (ahMNC) is a candidate for regeneration therapy for neurodegenerative diseases. Here, we developed a primary clump culture method for ahMNCs to increase the efficiency of isolation and in vitro expansion. The same amount of human temporal lobe (1 g) was partially digested and then filtered through strainers with various pore sizes, resulting in four types of clumps: Clump I > 100 µm, 70 µm < Clump II < 100 µm, 40 µm < Clump III < 70 µm, and Clump IV < 40 µm. At 3 and 6 days after culture, Clump II showed significantly higher number of colonies than the other Clumps. Moreover, ahMNCs derived from Clump II (ahMNCs-Clump II) showed stable proliferation, and shortened the time to first passage from 19 to 15 days, and the time to 1 × 10⁹ cells from 42 to 34 days compared with the previous single-cell method. ahMNCs-Clump II had neural differentiation and pro-angiogenic potentials, which are the characteristics of ahMNCs. In conclusion, the novel clump culture method for ahMNCs has significantly higher efficiency than previous techniques. Considering the small amount of available human brain tissue, the clump culture method would promote further clinical applications of ahMNCs.

Neurogenin-2-transduced human neural progenitor cells attenuate neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic (HI) brain injury leads to high mortality and neurodevelopmental disabilities. Multipotent neural progenitor cells (NPCs) with self-renewing capacity have the potential to reduce neuronal loss and improve the compromised environment in the HI brain injury. However, the therapeutic efficacy of neuronal-committed progenitor cells and the underlying mechanisms of recovery are not yet fully understood. Therefore, this study investigated the regenerative ability and action mechanisms of neuronally committed human NPCs (hNPCs) transduced with neurogenin-2 (NEUROG2) in neonatal HI brain injury. NEUROG2- or green fluorescent protein (GFP)-encoding adenoviral vector-transduced hNPCs (NEUROG2- or GFP-NPCs) were transplanted into neonatal mouse brains with HI injury. Grafted NEUROG2-NPCs showed robust dispersion and engraftment, prolonged survival, and neuronal differentiation in HI brain injury. NEUROG2-NPCs significantly improved neurological behaviors, decreased cellular apoptosis, and increased the neurite outgrowth and axonal sprouting in HI brain injury. In contrast, GFP-NPC grafts moderately enhanced axonal extension with limited behavioral recovery. Notably, NEUROG2-NPCs showed increased secretion of multiple factors, such as nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NTF3), fibroblast growth factor 9 (FGF9), ciliary neurotrophic factor (CNTF), and thrombospondins 1 and 2 (THBS 1/2), which promoted SH-SY5Y neuroblastoma cell survival and neurite outgrowth. Thus, we postulate that NEUROG2-expressing human NPCs facilitate functional recovery after neonatal HI brain injury via their ability to secrete multiple factors that enhance neuronal survival and neuroplasticity.

Insights in spatio-temporal characterization of human fetal neural stem cells

Primary human fetal cells have been used in clinical trials of cell replacement therapy for the treatment of neurodegenerative disorders such as Huntington's disease (HD). However, human fetal primary cells are scarce and difficult to work with and so a renewable source of cells is sought. Human fetal neural stem cells (hfNSCs) can be generated from human fetal tissue, but little is known about the differences between hfNSCs obtained from different developmental stages and brain areas. In the present work we characterized hfNSCs, grown as neurospheres, obtained from three developmental stages: 4-5, 6-7 and 8-9weeks post conception (wpc) and four brain areas: forebrain, cortex, whole ganglionic eminence (WGE) and cerebellum. We observed that, as fetal brain development proceeds, the number of neural precursors is diminished and post-mitotic cells are increased. In turn, primary cells obtained from older embryos are more sensitive to the dissociation process, their viability is diminished and they present lower proliferation ratios compared to younger embryos. However, independently of the developmental stage of derivation proliferation ratios were very low in all cases. Improvements in the expansion rates were achieved by mechanical, instead of enzymatic, dissociation of neurospheres but not by changes in the seeding densities. Regardless of the developmental stage, neurosphere cultures presented large variability in the viability and proliferation rates during the initial 3-4 passages, but stabilized achieving significant expansion rates at passage 5 to 6. This was true also for all brain regions except cerebellar derived cultures that did not expand. Interestingly, the brain region of hfNSC derivation influences the expansion potential, being forebrain, cortex and WGE derived cells the most expandable compared to cerebellar. Short term expansion partially compromised the regional identity of cortical but not WGE cultures. Nevertheless, both expanded cultures were multipotent and kept the ability to differentiate to region specific mature neuronal phenotypes.

Therapeutic potential of human olfactory bulb neural stem cells for spinal cord injury in rats

STUDY DESIGN

Adult human olfactory bulb neural stem cells (OBNSCs) were isolated from human patients undergoing craniotomy for tumor resection. They were genetically engineered to overexpresses green fluorescent protein (GFP) to help trace them following engraftment. Spinal cord injury (SCI) was induced in rats using standard laminectomy protocol, and GFP-OBNSC were engrafted into rat model of SCI at day 7 post injury. Three rat groups were used: (i) Control group, (ii) Sham group (injected with cerebrospinal fluid) and treated group (engrafted with OBNSCs). Tissues from different groups were collected weekly up to 2 months. The collected tissues were fixed in 4% paraformaldehyde, processed for paraffin sectioning, immunohistochemically stained for different neuronal and glial markers and examined with bright-field fluorescent microscopy. Restoration of sensory motor functions we assessed on a weekly bases using the BBB score.

OBJECTIVES

To assess the therapeutic potential of OBNSCs-GFP and their ability to survive, proliferate, differentiate and to restore lost sensory motor functions following their engraftment in spinal cord injury (SCI).

METHODS

GFP-OBNSC were engrafted into a rat model of SCI at day 7 post injury and were followed-up to 8 weeks using behavioral and histochemical methods.

RESULTS

All transplanted animals exhibited successful engraftment. The survival rate was about 30% of initially transplanted cells. Twenty-seven percent of the engrafted cells differentiated along the NG2 and O4-positive oligodendrocyte lineage, 16% into MAP2 and β-tubulin-positive neurons, and 56% into GFAP-positive astrocytes.

CONCLUSION

GFP-OBNSCs had survived for >8 weeks after engraftment and were differentiated into neurons, astrocytes and oligodendrocytes, The engrafted cells were distributed throughout gray and white matter of the cord with no evidence of abnormal morphology or any mass formation indicative of tumorigenesis. However, the engrafted cells failed to restore lost sensory and motor functions as evident from behavioral analysis using the BBB score test.

Importance of being Nernst: Synaptic activity and functional relevance in stem cell-derived neurons

Functional synaptogenesis and network emergence are signature endpoints of neurogenesis. These behaviors provide higher-order confirmation that biochemical and cellular processes necessary for neurotransmitter release, post-synaptic detection and network propagation of neuronal activity have been properly expressed and coordinated among cells. The development of synaptic neurotransmission can therefore be considered a defining property of neurons. Although dissociated primary neuron cultures readily form functioning synapses and network behaviors in vitro, continuously cultured neurogenic cell lines have historically failed to meet these criteria. Therefore, in vitro-derived neuron models that develop synaptic transmission are critically needed for a wide array of studies, including molecular neuroscience, developmental neurogenesis, disease research and neurotoxicology. Over the last decade, neurons derived from various stem cell lines have shown varying ability to develop into functionally mature neurons. In this review, we will discuss the neurogenic potential of various stem cells populations, addressing strengths and weaknesses of each, with particular attention to the emergence of functional behaviors. We will propose methods to functionally characterize new stem cell-derived neuron (SCN) platforms to improve their reliability as physiological relevant models. Finally, we will review how synaptically active SCNs can be applied to accelerate research in a variety of areas. Ultimately, emphasizing the critical importance of synaptic activity and network responses as a marker of neuronal maturation is anticipated to result in in vitro findings that better translate to efficacious clinical treatments.

Cross-talk between human neural stem/progenitor cells and peripheral blood mononuclear cells in an allogeneic co-culture model

Transplantation of human neural stem/progenitor cells (hNSCs) as a regenerative cell replacement therapy holds great promise. However, the underlying mechanisms remain unclear. We, here, focused on the interaction between hNSCs and allogeneic peripheral blood mononuclear cells (PBMCs) in a co-culture model. We found that hNSCs significantly decrease the CD3⁺ and CD8⁺ T cells, reduce the gamma delta T cells and increase the regulatory T cells, along with reduced pro-inflammatory cytokines and increased anti-inflammatory cytokines after co-culture. We also found that PBMCs, in turn, significantly promote the proliferation and differentiation of hNSCs. Our data suggest that hNSCs cross-talk with immune cells.

Transplantation of purified autologous leukapheresis-derived CD34+ and CD133+ stem cells for patients with chronic spinal cord injuries: long-term evaluation of safety and efficacy

This study is aimed at describing a novel method for treating patients with chronic complete spinal cord injuries (SCIs) by utilizing autologous, purified CD34(+) and CD133(+) stem cells (SCs). The study focuses on the safety and efficacy of transplanting unmanipulated, autologous, purified stem cells in treated patients during a 5-year follow-up period. In this report, 19 patients were included (16 males and 3 females) who presented with a complete SCI (ASIA-A) in the thoracic region. The patients' endogenous cells were mobilized with subcutaneous granulocyte-colony-stimulating factor (G-CSF) for 5 days. We utilized the CliniMACS magnetic separation system to purify leukapheresis-derived CD34(+) and CD133(+) SCs. Purified SCs were directly transplanted into the SCI site. Patients were then monitored and followed for up to 5 years. On average, 76 × 10(6) purified SCs were obtained from each patient, with 95.2% purity and >98% viability. SC transplantation into the cyst cavity or the subarachnoid space was successful and well tolerated in all 19 patients and did not cause any allergic or inflammatory reactions within the CNS in the early or late periods after transplantation. Ten patients (53%) showed no improvement after 42-60 months (ASIA-A), while seven patients (37%) demonstrated segmental sensory improvement (ASIA-B), and the remaining two patients (10%) had motor improvement (ASIA-C). This study presents a safe method for transplanting specific populations of purified autologous SCs that can be used to treat SCIs in a clinical setting. The results may be utilized as a stepping-stone for future investigations in the field of regenerative medicine for treatment of SCIs and other neurological diseases. This manuscript is published as part of the International Association of Neurorestoratology (IANR) special issue of Cell Transplantation.

Regionally-specified second trimester fetal neural stem cells reveals differential neurogenic programming

Neural stem/progenitor cells (NSC) have the potential for treatment of a wide range of neurological diseases such as Parkinson Disease and multiple sclerosis. Currently, NSC have been isolated only from hippocampus and subventricular zone (SVZ) of the adult brain. It is not known whether NSC can be found in all parts of the developing mid-trimester central nervous system (CNS) when the brain undergoes massive transformation and growth. Multipotent NSC from the mid-trimester cerebra, thalamus, SVZ, hippocampus, thalamus, cerebellum, brain stem and spinal cord can be derived and propagated as clonal neurospheres with increasing frequencies with increasing gestations. These NSC can undergo multi-lineage differentiation both in vitro and in vivo, and engraft in a developmental murine model. Regionally-derived NSC are phenotypically distinct, with hippocampal NSC having a significantly higher neurogenic potential (53.6%) over other sources (range of 0%–27.5%, p<0.004). Whole genome expression analysis showed differential gene expression between these regionally-derived NSC, which involved the Notch, epidermal growth factor as well as interleukin pathways. We have shown the presence of phenotypically-distinct regionally-derived NSC from the mid-trimester CNS, which may reflect the ontological differences occurring within the CNS. Aside from informing on the role of such cells during fetal growth, they may be useful for different cellular therapy applications.

A cGMP-applicable expansion method for aggregates of human neural stem and progenitor cells derived from pluripotent stem cells or fetal brain tissue

A cell expansion technique to amass large numbers of cells from a single specimen for research experiments and clinical trials would greatly benefit the stem cell community. Many current expansion methods are laborious and costly, and those involving complete dissociation may cause several stem and progenitor cell types to undergo differentiation or early senescence. To overcome these problems, we have developed an automated mechanical passaging method referred to as "chopping" that is simple and inexpensive. This technique avoids chemical or enzymatic dissociation into single cells and instead allows for the large-scale expansion of suspended, spheroid cultures that maintain constant cell/cell contact. The chopping method has primarily been used for fetal brain-derived neural progenitor cells or neurospheres, and has recently been published for use with neural stem cells derived from embryonic and induced pluripotent stem cells. The procedure involves seeding neurospheres onto a tissue culture Petri dish and subsequently passing a sharp, sterile blade through the cells effectively automating the tedious process of manually mechanically dissociating each sphere. Suspending cells in culture provides a favorable surface area-to-volume ratio; as over 500,000 cells can be grown within a single neurosphere of less than 0.5 mm in diameter. In one T175 flask, over 50 million cells can grow in suspension cultures compared to only 15 million in adherent cultures. Importantly, the chopping procedure has been used under current good manufacturing practice (cGMP), permitting mass quantity production of clinical-grade cell products.

Multiplex mapping of chromatin accessibility and DNA methylation within targeted single molecules identifies epigenetic heterogeneity in neural stem cells and glioblastoma

Human tumors are comprised of heterogeneous cell populations that display diverse molecular and phenotypic features. To examine the extent to which epigenetic differences contribute to intratumoral cellular heterogeneity, we have developed a high-throughput method, termed MAPit-patch. The method uses multiplexed amplification of targeted sequences from submicrogram quantities of genomic DNA followed by next generation bisulfite sequencing. This provides highly scalable and simultaneous mapping of chromatin accessibility and DNA methylation on single molecules at high resolution. Long sequencing reads from targeted regions maintain the structural integrity of epigenetic information and provide substantial depth of coverage, detecting for the first time minority subpopulations of epigenetic configurations formerly obscured by existing genome-wide and population-ensemble methodologies. Analyzing a cohort of 71 promoters of genes with exons commonly mutated in cancer, MAPit-patch uncovered several differentially accessible and methylated promoters that are associated with altered gene expression between neural stem cell (NSC) and glioblastoma (GBM) cell populations. In addition, considering each promoter individually, substantial epigenetic heterogeneity was observed across the sequenced molecules, indicating the presence of epigenetically distinct cellular subpopulations. At the divergent MLH1/EPM2AIP1 promoter, a locus with three well-defined, nucleosome-depleted regions (NDRs), a fraction of promoter copies with inaccessible chromatin was detected and enriched upon selection of temozolomide-tolerant GBM cells. These results illustrate the biological relevance of epigenetically distinct subpopulations that in part underlie the phenotypic heterogeneity of tumor cell populations. Furthermore, these findings show that alterations in chromatin accessibility without accompanying changes in DNA methylation may constitute a novel class of epigenetic biomarker.

Healthy human CSF promotes glial differentiation of hESC-derived neural cells while retaining spontaneous activity in existing neuronal networks

The possibilities of human pluripotent stem cell-derived neural cells from the basic research tool to a treatment option in regenerative medicine have been well recognized. These cells also offer an interesting tool for in vitro models of neuronal networks to be used for drug screening and neurotoxicological studies and for patient/disease specific in vitro models. Here, as aiming to develop a reductionistic in vitro human neuronal network model, we tested whether human embryonic stem cell (hESC)-derived neural cells could be cultured in human cerebrospinal fluid (CSF) in order to better mimic the in vivo conditions. Our results showed that CSF altered the differentiation of hESC-derived neural cells towards glial cells at the expense of neuronal differentiation. The proliferation rate was reduced in CSF cultures. However, even though the use of CSF as the culture medium altered the glial vs. neuronal differentiation rate, the pre-existing spontaneous activity of the neuronal networks persisted throughout the study. These results suggest that it is possible to develop fully human cell and culture-based environments that can further be modified for various in vitro modeling purposes.

Optimized surface markers for the prospective isolation of high-quality hiPSCs using flow cytometry selection

hiPSC derivation and selection remains inefficient; with selection of high quality clones dependent on extensive characterization which is not amenable to high-throughput (HTP) approaches. We recently described the use of a cocktail of small molecules to enhance hiPSC survival and stability in single cell culture and the use of flow cytometry cell sorting in the HTP-derivation of hiPSCs. Here we report an enhanced protocol for the isolation of bona fide hiPSCs in FACS-based selection using an optimized combination of cell surface markers including CD30. Depletion of CD30(+) cells from reprogramming cultures almost completely abolished the NANOG and OCT4 positive sub-population, suggesting it is a pivotal marker of pluripotent cells. Combining CD30 to SSEA4 and TRA-1-81 in FACS greatly enhanced specificity and efficiency of hiPSC selection and derivation. The current method allows for the efficient and automated, prospective isolation of high-quality hiPSC from the reprogramming cell milieu.

The globoseries glycosphingolipid SSEA-4 is a marker of bone marrow-derived clonal multipotent stromal cells in vitro and in vivo

The therapeutic potential of multipotent stromal cells (MSC) may be enhanced by the identification of markers that allow their discrimination and enumeration both in vivo and in vitro. Here, we investigated the ability of embryonic stem cell-associated glycosphingolipids to isolate human MSC from both whole-bone-marrow (BM) and stromal cell cultures. Only SSEA-4 was consistently expressed on cells within the CD45loCD105hi marrow fraction and could be used to isolate cells with the capacity to give rise to stromal cultures containing MSC. Human stromal cultures, generated in either the presence or absence of serum, contained heterogeneous cell populations discriminated by the quantity of SSEA-4 epitopes detected on their surface. A low level of surface SSEA-4 (SSEA-4lo) correlated with undetectable levels of the α2,3-sialyltransferase-II enzyme required to synthesize SSEA-4; a reduced proliferative potential; and the loss of fat-, bone-, and cartilage-forming cells during long-term culture. In vitro, single cells with the capacity to generate multipotent stromal cultures were detected exclusively in the SSEA-4hi fraction. Our data demonstrate that a high level of surface epitopes for SSEA-4 provides a definitive marker of MSC from human BM.

Advances in stem cell therapy for spinal cord injury

Spinal cord injury (SCI) is a devastating condition producing great personal and societal costs and for which there is no effective treatment. Stem cell transplantation is a promising therapeutic strategy, though much preclinical and clinical research work remains. Here, we briefly describe SCI epidemiology, pathophysiology, and experimental and clinical stem cell strategies. Research in stem cell biology and cell reprogramming is rapidly advancing, with the hope of moving stem cell therapy closer to helping people with SCI. We examine issues important for clinical translation and provide a commentary on recent developments, including termination of the first human embryonic stem cell transplantation trial in human SCI.

Online 3-D tracking of suspension living cells imaged with phase-contrast microscopy

Neural stem cells/neural progenitors (NSCs/NPs) are cells that give rise to the main cell types of the nervous system: oligodendrocytes, neurons, and astrocytes. Studying NSCs/NPs with time-lapse microscopy is critical to the understanding of the biology of these cells. However, NSCs/NPs are very sensitive to phototoxic damage, and therefore, fluorescent dyes cannot be used to follow these cells. Also, since in most of NSC/NP-related experiments, a large number of cells neesd to be monitored. Consequently, the acquisition of a huge amount of images is required. An additional difficulty is related to our original suspension living, tracking objective, behavior much closer to the natural, in vivo, way of development of the cells. Indeed, unlike adherent cells, suspension cells float freely in a liquid solution, thus, making their dynamics very different from that of adherent cells. As a result, existing visual tracking algorithms that have primarily been developed to track adherent cells are no longer adequate to tackle living cells in suspension. This paper presents a novel automated 3-D visual tracking of suspension living cells for time-lapse image acquisition using phase-contrast microscopy. This new tracking method can potentially strongly impact on current 3-D video microscopy methods, paving the way for innovative analysis of NSCs/NPs and as a result, on the study of neurodegenerative diseases.

Targeted Intra-arterial Transplantation of Stem Cells to the Injured CNS is more Effective than Intravenous Administration: Engraftment is Dependent on Cell Type and Adhesion Molecule Expression

Stem cell transplantation procedures using intraparenchymal injections cause tissue injury in addition to associated surgical risks. Intravenous cell administration give engraftment in parenchymal lesions although the method has low efficacy and specificity. In pathological conditions with inflammation, such as traumatic brain injury, there is a transient up-regulation of ICAM-1 and VCAM-1 which might provide environmental cues for migration of stem cells from blood to parenchyma. The aim of this study was to i) analyze the effect of intra-arterial administration on cellular engraftment, ii) compare engraftment and side effects between three different stem cell systems, and iii) analyze gene expression in these three systems. We performed specific intra-arterial transplantations with human mesenchymal stem cells (hMSCs), human neural progenitor cells (hNPCs), and rat neural progenitor cells (rNPCs) in a rat model of traumatic brain injury. These results were compared to the intravenous route for each cell type, respectively. Analysis of engraftment and recipient characterization was performed by immunohistochemistry. We further characterized the different types of cells by microarray and RT-qPCR analysis. Specific intra-arterial transplantations produced significantly higher engraftment compared to intravenous transplantation with hMSCs and rNPCs. No engraftment was detected after intra-arterial or intravenous administration of hNPCs. Characterization of integrin expression indicated that CD49dVCAM-1 and possibly ICAM-1 interactions through CD18 and CD11a, respectively, are important for engraftment after intravascular cell administration. No side effects, such as thromboembolic complications, were detected. When translating stem cell therapies to clinical practice, the route of transplantation and the properties of the cell lines (homing, diapedesis, and migration) become important. This study supports the use of selective intra-arterial transplantation for improving engraftment after traumatic brain injury. In addition, we conclude that careful analysis of cells intended for local, intra-arterial transplantation with respect to integrin expression is important.

Neural stem/progenitor cells from the adult human spinal cord are multipotent and self-renewing and differentiate after transplantation

Neural stem/progenitor cell (NSPC) transplantation is a promising therapy for spinal cord injury (SCI). However, little is known about NSPC from the adult human spinal cord as a donor source. We demonstrate for the first time that multipotent and self-renewing NSPC can be cultured, passaged and transplanted from the adult human spinal cord of organ transplant donors. Adult human spinal cord NSPC require an adherent substrate for selection and expansion in EGF (epidermal growth factor) and FGF2 (fibroblast growth factor) enriched medium. NSPC as an adherent monolayer can be passaged for at least 9 months and form neurospheres when plated in suspension culture. In EGF/FGF2 culture, NSPC proliferate and primarily express nestin and Sox2, and low levels of markers for differentiating cells. Leukemia inhibitory factor (LIF) promotes NSPC proliferation and significantly enhances GFAP expression in hypoxia. In differentiating conditions in the presence of serum, these NSPC show multipotentiality, expressing markers of neurons, astrocytes, and oligodendrocytes. Dibutyryl cyclic AMP (dbcAMP) significantly enhances neuronal differentiation. We transplanted the multipotent NSPC into SCI rats and show that the xenografts survive, are post-mitotic, and retain the capacity to differentiate into neurons and glia.

Together, these findings reveal that multipotent self-renewing NSPC cultured and passaged from adult human spinal cords of organ transplant donors, respond to exogenous factors that promote selective differentiation, and survive and differentiate after transplantation into the injured spinal cord.

Biogrid--a microfluidic device for large-scale enzyme-free dissociation of stem cell aggregates

Culturing stem cells as free-floating aggregates in suspension facilitates large-scale production of cells in closed systems, for clinical use. To comply with GMP standards, the use of substances such as proteolytic enzymes should be avoided. Instead of enzymatic dissociation, the growing cell aggregates may be mechanically cut at passage, but available methods are not compatible with large-scale cell production and hence translation into the clinic becomes a severe bottle-neck. We have developed the Biogrid device, which consists of an array of micrometerscale knife edges, micro-fabricated in silicon, and a manifold in which the microgrid is placed across the central fluid channel. By connecting one side of the Biogrid to a syringe or a pump and the other side to the cell culture, the culture medium with suspended cell aggregates can be aspirated, forcing the aggregates through the microgrid, and ejected back to the cell culture container. Large aggregates are thereby dissociated into smaller fragments while small aggregates pass through the microgrid unaffected. As proof-of-concept, we demonstrate that the Biogrid device can be successfully used for repeated passage of human neural stem/progenitor cells cultured as so-called neurospheres, as well as for passage of suspension cultures of human embryonic stem cells. We also show that human neural stem/progenitor cells tolerate transient pressure changes far exceeding those that will occur in a fluidic system incorporating the Biogrid microgrids. Thus, by using the Biogrid device it is possible to mechanically passage large quantities of cells in suspension cultures in closed fluidic systems, without the use of proteolytic enzymes.

Forced Runx1 expression in human neural stem/progenitor cells transplanted to the rat dorsal root ganglion cavity results in extensive axonal growth specifically from spinal cord-derived neurospheres

Cell replacement therapy holds great promise for treating a wide range of human disorders. However, ensuring the predictable differentiation of transplanted stem cells, eliminating their risk of tumor formation, and generating fully functional cells after transplantation remain major challenges in regenerative medicine. Here, we explore the potential of human neural stem/progenitor cells isolated from the embryonic forebrain (hfNSPCs) or the spinal cord (hscNSPCs) to differentiate to projection neurons when transplanted into the dorsal root ganglion cavity of adult recipient rats. To stimulate axonal growth, we transfected hfNSPC- and hscNSPC-derived neurospheres, prior to their transplantation, with a Tet-Off Runx1-overexpressing plasmid to maintain Runx1 expression in vivo after transplantation. Although pronounced cell differentiation was found in the Runx1-expressing transplants from both cell sources, we observed extensive, long-distance growth of axons exclusively from hscNSPC-derived transplants. These axons ultimately reached the dorsal root transitional zone, the boundary separating peripheral and central nervous systems. Our data show that hscNSPCs have the potential to differentiate to projection neurons with long-distance axonal outgrowth and that Runx1 overexpression is a useful approach to induce such outgrowth in specific sources of NSPCs.

New bioengineering insights into human neural precursor cell expansion in culture

Understanding initial cell growth, interactions associated with the process of expansion of human neural precursor cells (hNPCs), and cellular events pre- and postdifferentiation are important for developing bioprocessing protocols to reproducibly generate multipotent cells that can be used in basic research or the treatment of neurodegenerative disorders. Herein, we report the in vitro responses of telencephalon hNPCs grown in a serum-free growth medium using time-lapse live imaging as well as cell-surface marker, aggregate size, and immunocytochemical analyses. Time-lapse analysis of hNPC initial expansion indicated that cell-surface attachment in stationary culture and the frequency of cell-cell interaction in suspension conditions are important for subsequent aggregate formation and hNPC growth. In the absence of cell-surface attachment in low-attachment stationary culture, large aggregates of cells were formed and expansion was adversely affected. The majority of the telencephalon hNPCs expressed CD29, CD90, and CD44 (cell surface markers involved in cell-ECM and cell-cell interactions to regulate biological functions such as proliferation), suggesting that cell-surface attachment and cell-cell interactions play a significant role in the subsequent formation of cell aggregates and the expansion of hNPCs. Before differentiation, about 90% of the cells stained positive for nestin and expressed two neural precursor cells surface markers (CD133 and CD24). Upon withdrawal of growth cytokines, hNPCs first underwent cell division and then differentiated preferentially towards a neuronal rather than a glial phenotype. This study provides key information regarding human NPC behavior under different culture conditions and favorable culture conditions that are important in establishing reproducible hNPC expansion protocols.

Human neurospheres: From stained sections to three-dimensional assembly

Human neurospheres are free-floating spherical clusters generated from a single neural stem cell and comprising cells at different stages of maturation in the neuronal and glial lineages. Although recent findings have disproved the original idea of clonally derived neurospheres according to the paradigm of one stem cell — one neurosphere, they still represent a valid model for growing neural stem cell cultures in vitro. While the immunocytochemical approach to the identification of stem cells, progenitor cells, and mature cells has been extensively used, scant data are available about the ultrastructural arrangement of different cell types within the neurosphere. This paper provides, by means of scanning electron microscopy, some new insights into the three-dimensional assembly of human neurospheres, trying to correlate some parameters such as cell density, shape and growing strategies with the immunolocalization of some antigens such as nestin, GFAP, α-internexin and βIII-tubulin. The major findings from this study are: a) regardless of the stage of in vitro maturation, the growth of the spheres is the result of mitotic divisions producing the aspect of an irregular budding mechanism in the outermost layer look like; b) analysis of the volumetric composition of the inner core has revealed the presence of two alternative shape pattern (pyramidal vs rounded cells) possibly related to both the ongoing maturation stages and GFAP and internexin expression.

Markers of pluripotency and differentiation in human neural precursor cells derived from embryonic stem cells and CNS tissue

Cell transplantation therapies for central nervous system (CNS) deficits such as spinal cord injury (SCI) have been shown to be effective in several animal models. One cell type that has been transplanted is neural precursor cells (NPCs), for which there are several possible sources. We have studied NPCs derived from human embryonic stem cells (hESCs) and human fetal CNS tissue (hfNPCs), cultured as neurospheres, and the expression of pluripotency and neural genes during neural induction and in vitro differentiation. mRNA for the pluripotency markers Nanog, Oct-4, Gdf3, and DNMT3b were downregulated during neural differentiation of hESCs. mRNA for these markers was found in nonpluripotent hfNPC at higher levels compared to hESC-NPCs. However, Oct-4 protein was found in hESC-NPCs after 8 weeks of culture, but not in hfNPCs. Similarly, SSEA-4 and CD326 were only found in hESC-NPCs. NPCs from both sources differentiated as expected to cells with typical features of neurons and astrocytes. The expressions of neuronal markers in hESC-NPCs were affected by the composition of cell culture medium, while this did not affect hfNPCs. Transplantation of hESC-NPC or hfNPC neurospheres into immunodeficient mouse testis or subcutaneous tissue did not result in tumor formation. In contrast, typical teratomas appeared in all animals after transplantation of hESC-NPCs to injured or noninjured spinal cords of immunodeficient rats. Our data show that transplantation to the subcutaneous tissue or the testes of immunodeficient mice is not a reliable method for evaluation of the tumor risk of remaining pluripotent cells in grafts.

Distinct effects of sonic hedgehog and Wnt-7a on differentiation of neonatal neural stem/progenitor cells in vitro

Sonic hedgehog (Shh) and Wnt-7a are morphogens involved in embryonic as well as ongoing adult neurogenesis. Their effects on the differentiation and membrane properties of neonatal neural stem/progenitor cells (NS/PCs) were studied in vitro using NS/PCs transduced with either Shh or Wnt-7a. Eight days after the onset of in vitro differentiation the cells were analyzed for the expression of neuronal and glial markers using immunocytochemical and Western blot analysis, and their membrane properties were characterized using the patch-clamp technique. Our results showed that both Shh and Wnt-7a increased the numbers of cells expressing neuronal markers; however, quantitative immunocytochemical analysis showed that only Wnt-7a enhanced the outgrowth and the development of processes in these cells. In addition, Wnt-7a markedly suppressed gliogenesis. The electrophysiological analysis revealed that Wnt-7a increased, while Shh decreased the incidence of cells displaying a neuron-like current pattern, represented by outwardly rectifying K(+) currents and tetrodotoxin-sensitive Na(+) currents. Additionally, Wnt-7a increased cell proliferation only at the early stages of differentiation, while Shh promoted proliferation within the entire course of differentiation. Thus we can conclude that Shh and Wnt-7a interfere differently with the process of neuronal differentiation and that they promote distinct stages of neuronal differentiation in neonatal NS/PCs.

Human neural stem cells differentiate and promote locomotor recovery in an early chronic spinal cord injury NOD-scid mouse model

Background

Traumatic spinal cord injury (SCI) results in partial or complete paralysis and is characterized by a loss of neurons and oligodendrocytes, axonal injury, and demyelination/dysmyelination of spared axons. Approximately 1,250,000 individuals have chronic SCI in the U.S.; therefore treatment in the chronic stages is highly clinically relevant. Human neural stem cells (hCNS-SCns) were prospectively isolated based on fluorescence-activated cell sorting for a CD133⁺ and CD24^−/lo population from fetal brain, grown as neurospheres, and lineage restricted to generate neurons, oligodendrocytes and astrocytes. hCNS-SCns have recently been transplanted sub-acutely following spinal cord injury and found to promote improved locomotor recovery. We tested the ability of hCNS-SCns transplanted 30 days post SCI to survive, differentiate, migrate, and promote improved locomotor recovery.

Methods and Findings

hCNS-SCns were transplanted into immunodeficient NOD-scid mice 30 days post spinal cord contusion injury. hCNS-SCns transplanted mice demonstrated significantly improved locomotor recovery compared to vehicle controls using open field locomotor testing and CatWalk gait analysis. Transplanted hCNS-SCns exhibited long-term engraftment, migration, limited proliferation, and differentiation predominantly to oligodendrocytes and neurons. Astrocytic differentiation was rare and mice did not exhibit mechanical allodynia. Furthermore, differentiated hCNS-SCns integrated with the host as demonstrated by co-localization of human cytoplasm with discrete staining for the paranodal marker contactin-associated protein.

Conclusions

The results suggest that hCNS-SCns are capable of surviving, differentiating, and promoting improved locomotor recovery when transplanted into an early chronic injury microenvironment. These data suggest that hCNS-SCns transplantation has efficacy in an early chronic SCI setting and thus expands the “window of opportunity” for intervention.

Developmental cues and persistent neurogenic potential within an in vitro neural niche

Background

Neurogenesis, the production of neural cell-types from neural stem cells (NSCs), occurs during development as well as within select regions of the adult brain. NSCs in the adult subependymal zone (SEZ) exist in a well-categorized niche microenvironment established by surrounding cells and their molecular products. The components of this niche maintain the NSCs and their definitive properties, including the ability to self-renew and multipotency (neuronal and glial differentiation).

Results

We describe a model in vitro NSC niche, derived from embryonic stem cells, that produces many of the cells and products of the developing subventricular zone (SVZ) and adult SEZ NSC niche. We demonstrate a possible role for apoptosis and for components of the extracellular matrix in the maintenance of the NSC population within our niche cultures. We characterize expression of genes relevant to NSC self-renewal and the process of neurogenesis and compare these findings to gene expression produced by an established neural-induction protocol employing retinoic acid.

Conclusions

The in vitro NSC niche shows an identity that is distinct from the neurally induced embryonic cells that were used to derive it. Molecular and cellular components found in our in vitro NSC niche include NSCs, neural progeny, and ECM components and their receptors. Establishment of the in vitro NSC niche occurs in conjunction with apoptosis. Applications of this culture system range from studies of signaling events fundamental to niche formation and maintenance as well as development of unique NSC transplant platforms to treat disease or injury.

Long-Term Survival, Robust Neuronal Differentiation, and Extensive Migration of Human Forebrain Stem/Progenitor Cells Transplanted to the Adult Rat Dorsal Root Ganglion Cavity

Neurons in dorsal root ganglia (DRGs) transmit sensory information from peripheral tissues to the spinal cord. This pathway can be interrupted, for example, as the result of physical violence, traffic accidents, or complications during child delivery. As a consequence, the patient permanently loses sensation and often develops intractable neuropathic pain in the denervated area. Here we investigate whether human neural stem/progenitor cells (hNSPCs) transplanted to the DRG cavity can serve as a source for repairing lost peripheral sensory connections. We found that hNSPCs robustly differentiate to neurons, which survive long-term transplantation. The neuronal population in the transplants was tightly surrounded by astrocytes, suggesting their active role in neuron survival. Furthermore, 3 months after grafting hNSPCs were found in the dorsal root transitional zone (DRTZ) and within the spinal cord. The level of differentiation of transplanted cells was high in the core of the transplants whereas cells that migrated to the DRTZ and spinal cord were undifferentiated, nestin-expressing precursors. These data indicate that peripherally transplanted hNPSCs can be used for repair of dorsal root avulsion or spinal cord injuries; however, additional factors are required to guide their differentiation to the desired type of neurons. Furthermore, hNPSCs that migrate from the DRG cavity graft site to the DRTZ and spinal cord may provide trophic support for regenerating dorsal root axons, thereby allowing them to reenter the host spinal cord.

CD marker expression profiles of human embryonic stem cells and their neural derivatives, determined using flow-cytometric analysis, reveal a novel CD marker for exclusion of pluripotent stem cells

Human embryonic stem cells (hESCs) are pluripotent cells that can differentiate into neural cell lineages. These neural populations are usually heterogeneous and can contain undifferentiated pluripotent cells that are capable of producing teratomas in cell grafts. The characterization of surface protein profiles of hESCs and their neural derivatives is important to determine the specific markers that can be used to exclude undifferentiated cells from neural populations. In this study, we analyzed the cluster of differentiation (CD) marker expression profiles of seven undifferentiated hESC lines using flow-cytometric analysis and compared their profiles to those of neural derivatives. Stem cell and progenitor marker CD133 and epithelial adhesion molecule marker CD326 were more highly expressed in undifferentiated hESCs, whereas neural marker CD56 (NCAM) and neural precursor marker (chemokine receptor) CD184 were more highly expressed in hESC-derived neural cells. CD326 expression levels were consistently higher in all nondifferentiated hESC lines than in neural cell derivatives. In addition, CD326-positive hESCs produced teratomas in SCID mouse testes, whereas CD362-negative neural populations did not. Thus, CD326 may be useful as a novel marker of undifferentiated hESCs to exclude undifferentiated hESCs from differentiated neural cell populations prior to transplantation.

Laminin enhances the growth of human neural stem cells in defined culture media

Background

Human neural stem cells (hNSC) have the potential to provide novel cell-based therapies for neurodegenerative conditions such as multiple sclerosis and Parkinson's disease. In order to realise this goal, protocols need to be developed that allow for large quantities of hNSC to be cultured efficiently. As such, it is important to identify factors which enhance the growth of hNSC. In vivo, stem cells reside in distinct microenvironments or niches that are responsible for the maintenance of stem cell populations. A common feature of niches is the presence of the extracellular matrix molecule, laminin. Therefore, this study investigated the effect of exogenous laminin on hNSC growth.

Results

To measure hNSC growth, we established culture conditions using B27-supplemented medium that enable neurospheres to grow from human neural cells plated at clonal densities. Limiting dilution assays confirmed that neurospheres were derived from single cells at these densities. Laminin was found to increase hNSC numbers as measured by this neurosphere formation. The effect of laminin was to augment the proliferation/survival of the hNSC, rather than promoting the undifferentiated state. In agreement, apoptosis was reduced in dissociated neurospheres by laminin in an integrin β1-dependent manner.

Conclusion

The addition of laminin to the culture medium enhances the growth of hNSC, and may therefore aid their large-scale production.

Human neural stem cells and astrocytes, but not neurons, suppress an allogeneic lymphocyte response

Transplantation of human neural stem cells (NSCs) and their derivatives is a promising future treatment for neurodegenerative disease and traumatic nervous system lesions. An important issue is what kind of immunological reaction the cellular transplant and host interaction will result in. Previously, we reported that human NSCs, despite expressing MHC class I and class II molecules, do not trigger an allogeneic T cell response. Here, the immunocompetence of human NSCs, as well as differentiated neural cells, was further studied. Astrocytes expressed both MHC class I and class II molecules to a degree equivalent to that of the NSCs, whereas neurons expressed only MHC class I molecules. Neither the NSCs nor the differentiated cells triggered an allogeneic lymphocyte response. Instead, these potential donor NSCs and astrocytes, but not the neurons, exhibited a suppressive effect on an allogeneic immune response. The suppressive effect mediated by NSCs most likely involves cell-cell interaction. When the immunogenicity of human NSCs was tested in an acute spinal cord injury model in rodent, a xenogeneic rejection response was triggered. Thus, human NSCs and their derived astrocytes do not initiate, but instead suppress, an allogeneic response, while they cannot block a graft rejection in a xenogeneic setting.

Stem and progenitor cell therapies: recent progress for spinal cord injury repair

Mechanical trauma to the spinal cord is often accompanied by irreversible tissue damage, limited endogenous repair and permanent loss of motor, sensory and autonomic function. The implantation of exogenous cells or the stimulation of endogenous cells, to repopulate and replace or to provide a conducive environment for repair, offers a promising therapeutic direction for overcoming the multitude of obstacles facing successful recovery from spinal cord injury. Although relatively new to the scene of cell based therapies for reparative medicine, stem cells and their progenitors have been labeled as the 'cell of the future' for revolutionizing the treatment of CNS injury and neurodegenerative disorders. The following review examines the different types of stem cells and their progenitors, their utility in experimental models of spinal cord injury and explores the outstanding issues that still need to be addressed before they move towards clinical implementation.

Maintenance of regional difference in cellular composition of neurospheres derived from adult mouse olfactory bulb

Neurospheres are potentially good tools to study olfactory neurogenesis. For this purpose, it is necessary to characterize neurospheres derived from the olfactory system. This study is aimed at identifying the regional difference of cellular composition within neurospheres derived from the adult mouse olfactory bulb, and studying whether these characteristics are maintained throughout the long-term culture. Neural cells were obtained from the olfactory bulbs of 8-week-old Balb/c mice and the dissociated cells were cultured in serum-free media containing epidermal growth factor and basic fibroblast growth factor to form neurospheres. These neurospheres were subjected to characterization by confocal microscopy after immunofluorescence staining with nestin, proliferating cell nuclear antigen (PCNA), neuronal cell adhesion molecule (NCAM), glial fibrillary acidic protein (GFAP), O4, and olfactory marker protein (OMP). Confocal microscopy showed that nestin-reactive cells, which are stem cell-like cells, were present at the periphery of neurospheres and PCNA-reactive cells undergoing proliferation were found throughout the neurospheres. Neuronal cell markers, NCAM-reactive cells, were observed at the center of neurospheres while glial cell markers, GFAP- or O4-reactive cells, were present at the periphery of neurospheres. No cells were found to be reactive for OMP, a differentiated olfactory neuron marker. This regional distribution of cells in neurospheres was maintained through 17 passages for a year. The neural lineage of cells showed different distribution within neurospheres and this localization was preserved throughout the culture period. These findings in the neurosphere culture system of the olfactory bulb may help to study olfactory neurogenesis.

Late human cytomegalovirus (HCMV) proteins inhibit differentiation of human neural precursor cells into astrocytes

Human cytomegalovirus (HCMV) is the most common cause of congenital infections in developed countries, with an incidence varying between 0.5-2.2%. Such infection may be the consequence of either a primary infection or reactivation of a latent infection in the mother and the outcome may vary from asymptomatic to severe brain disorders. Moreover, infants that are asymptomatic at the time of birth may still develop neurologic sequelae at a later age. Our hypothesis is that infection of stem cells of the central nervous system by HCMV alters the proliferation, differentiation or migration of these cells, and thereby gives rise to the brain abnormalities observed. We show that infection of human neural precursor cells (NPCs) with the laboratory strain Towne or the clinical isolate TB40 of HCMV suppresses the differentiation of these cells into astrocytes even at an multiplicity of infection (MOI) as low as 0.1 (by 33% and 67%, respectively). This inhibition required active viral replication and the expression of late HCMV proteins. Infection as late as 24 hr after the onset of differentiation, but not after 72 hr, also prevented the maturation of infected cultures. Furthermore, in cultures infected with TB40 (at an MOI of 1), approximately 54% of the cells were apoptotic and cell proliferation was significantly attenuated. Clearly, HCMV can reduce the capacity of NPCs to differentiate into astrocytes and this effect may provide part of the explanation for the abnormalities in brain development associated with congenital HCMV infection.