Both apoptosis and necrosis occur early after intracerebral grafting of ventral mesencephalic tissue: a role for protease activation

Bcl-xL Promotes the Survival of Motor Neurons Derived from Neural Stem Cells

Neural stem cell (NSC) transplantation creates new hope for the treatment of neurodegenerative disorders by direct differentiation into neurons. However, this technique is limited by poor survival and functional neuron deficiency. In this research study, we generated pro-survival murine NSCs (mNSCs) via the ectopic expression of Bcl-xL. A doxycycline (Dox)-inducible Ngn2-Isl1-Lhx3 system was also integrated into the mNSC genome. The four gene-modified mNSCs can rapidly and effectively differentiate into motor neurons after Dox treatments. Ectopic Bcl-xL could resist replating-induced stress, glutamate toxicity, neuronal apoptosis and remarkably promote the survival of motor neurons. Taken together, we established genetically modified mNSCs with improved survival, which may be useful for motor neuron degenerative diseases.

Multifactoriality of Parkinson's Disease as Explored Through Human Neural Stem Cells and Their Transplantation in Middle-Aged Parkinsonian Mice

Parkinson's disease (PD) is an age-associated neurodegenerative disorder for which there is currently no cure. Cell replacement therapy is a potential treatment for PD; however, this therapy has more clinically beneficial outcomes in younger patients with less advanced PD. In this study, hVM1 clone 32 cells, a line of human neural stem cells, were characterized and subsequently transplanted in middle-aged Parkinsonian mice in order to examine cell replacement therapy as a treatment for PD. In vitro analyses revealed that these cells express standard dopamine-centered markers as well as others associated with mitochondrial and peroxisome function, as well as glucose and lipid metabolism. Four months after the transplantation of the hVM1 clone 32 cells, striatal expression of tyrosine hydroxylase was minimally reduced in all Parkinsonian mice but that of dopamine transporter was decreased to a greater extent in buffer compared to cell-treated mice. Behavioral tests showed marked differences between experimental groups, and cell transplant improved hyperactivity and gait alterations, while in the striatum, astroglial populations were increased in all groups due to age and a higher amount of microglia were found in Parkinsonian mice. In the motor cortex, nonphosphorylated neurofilament heavy was increased in all Parkinsonian mice. Overall, these findings demonstrate that hVM1 clone 32 cell transplant prevented motor and non-motor impairments and that PD is a complex disorder with many influencing factors, thus reinforcing the idea of novel targets for PD treatment that tend to be focused on dopamine and nigrostriatal damage.

Fabrication, characterization and evaluation of the effect of PLGA and PLGA-PEG biomaterials on the proliferation and neurogenesis potential of human neural SH-SY5Y cells

In recent years with regard to the development of nanotechnology and neural stem cell discovery, the combinatorial therapeutic strategies of neural progenitor cells and appropriate biomaterials have raised the hope for brain regeneration following neurological disorders. This study aimed to explore the proliferation and neurogenic effect of PLGA and PLGA-PEG nanofibers on human SH-SY5Y cells in in vitro condition. Nanofibers of PLGA and PLGA-PEG biomaterials were synthesized and fabricated using electrospinning method. Physicochemical features were examined using HNMR, FT-IR, and water contact angle assays. Ultrastructural morphology, the orientation of nanofibers, cell distribution and attachment were visualized by SEM imaging. Cell survival and proliferation rate were measured. Differentiation capacity was monitored by immunofluorescence staining of Map-2. HNMR, FT-IR assays confirmed the integration of PEG to PLGA backbone. Water contact angel assay showed increasing surface hydrophilicity in PLGA-PEG biomaterial compared to the PLGA substrate. SEM analysis revealed the reduction of PLGA-PEG nanofibers' diameter compared to the PLGA group. Cell attachment was observed in both groups while PLGA-PEG had a superior effect in the promotion of survival rate compared to other groups (p < .05). Compared to the PLGA group, PLGA-PEG increased the number of Ki67⁺ cells (p < .01). PLGA-PEG biomaterial induced neural maturation by increasing protein Map-2 compared to the PLGA scaffold in a three-dimensional culture system. According to our data, structural modification of PLGA with PEG could enhance orientated differentiation and the dynamic growth of neural cells.

Electroacupuncture Promotes the Survival of the Grafted Human MGE Neural Progenitors in Rats with Cerebral Ischemia by Promoting Angiogenesis and Inhibiting Inflammation

Stem cells have the potential as a regenerative therapy for cerebral ischemia by improving functional outcomes. However, cell transplantation has some limitations, including a low rate of the grafted cell survival. There is still a major challenge of promoting the harmonious symbiosis between grafted cells and the host. Acupuncture can effectively improve the functional outcome after cerebral ischemia. The present study evaluated the therapeutic effects and explored the mechanism of combined medial ganglionic eminence (MGE) neural progenitors differentiated from human embryonic stem cells (hESCs) with electroacupuncture (EA) in a bilateral common carotid artery occlusion (2VO) rat model. The results showed that EA could promote the survival of the grafted MGE neural progenitors differentiated from hESCs and alleviate learning and memory impairment in rats with cerebral ischemia. This may have partially resulted from inhibited expression of TNF-α and IL-1β and increased vascular endothelial growth factor (VEGF) expression and blood vessel density in the hippocampus. Our findings indicated that EA could promote the survival of the grafted MGE neural progenitors and enhance transplantation therapy's efficacy by promoting angiogenesis and inhibiting inflammation.

Dose-dependent effect of mesenchymal stromal cells co-grafted with dopaminergic neurons in a Parkinson's disease rat model

A major limiting factor for cell therapy in Parkinson's disease is the poor survival and reinnervation capacity of grafted dopaminergic neurons, independently of the cell source. Mesenchymal stromal cells (MSCs) have high capability to regulate the local environment through the release of trophic, antiapoptotic and immunomodulatory factors. In this work, we investigated whether co-grafting of MSCs could improve the survival and reinnervation ability of dopaminergic precursors transplanted in animal models of Parkinson's disease. Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic precursors (500,000 cells) with or without a high (200,000 cells) or low (25,000 cells) number of MSCs. Eight weeks after grafting, rats were tested for motor behaviour and sacrificed for histological analysis. Our results showed that the survival of dopaminergic neurons and graft-derived striatal dopaminergic innervation was higher in rats that received co-grafts containing a low number of MSCs than in non-co-grafted controls. However, the survival of dopaminergic neurons and graft-derived dopaminergic reinnervation was lower in rats receiving co-grafts with high number of MSCs than in non-co-grafted controls. In conclusion, co-grafting with MSCs or MSCs-derived products may constitute a useful strategy to improve dopaminergic graft survival and function. However, a tight control of MSCs density or levels of MSCs-derived products is necessary.

Current Developments in Cell Replacement Therapy for Parkinson's Disease

Parkinson's disease (PD) is characterized by tremor, rigidity, and bradykinesia. PD is caused mainly by depletion of the nigrostriatal pathway. Conventional medications such as levodopa are highly effective in the early stage of PD; however, these medications fail to prevent the underlying neurodegeneration. Cell replacement therapy (CRT) is a strategy to achieve long-term motor improvements by preventing or slowing disease progression. Replacement therapy can also increase the number of surviving dopaminergic neurons, an outcome confirmed by positron emission tomography and immunostaining. Several promising cell sources offer authentic and functional dopaminergic replacement neurons. These cell sources include fetal ventral mesencephalic tissue, embryonic stem cells (ESCs), neural stem cells (NSCs), mesenchymal stem cells (MSCs) from various tissues, induced pluripotent stem cells (iPSCs), and induced neural cells. To fully develop the potential of CRT, we need to recognize the advantages and limitations of these cell sources. For example, although fetal ventral midbrain is efficacious in some patients, its ethical issues and the existence of graft-induced dyskinesias (GID) have prevented its use in large-scale clinical applications. ESCs have reliable isolation protocols and the potential to differentiate into dopaminergic progenitors. iPSCs and induced neural cells are suitable for autologous grafting. Here we review milestone improvements and emerging sources for cell-based PD therapy to serve as a framework for clinicians and a key reference to develop replacement therapy for other neurological disorders.

Polycaprolactone fumarate acts as an artificial neural network to promote the biological behavior of neural stem cells

Herein, we investigated the effect of electrospun polycaprolactone fumarate (PCLF) nanofibers on neural stem cell (NSC) behavior in the in vitro setting. Murine NSCs were isolated from adult mice subventricular zone and immunophenotyped by flow cytometry assay and immunofluorescence staining. Cells were cultured on the plastic surface, laminin-coated surface, and electrospun PCLF nanofibers. Cell morphology, attachment, and spreading were evaluated by scanning electron microscopy analysis. Cell viability and proliferation rates were evaluated by MTT assay. The proliferation of plated cells was investigated by monitoring Ki-67-positive cells using flow cytometry analysis. The protein levels of Map-2 and GFAP were detected by using immunofluorescence staining to show neural and astrocyte differentiation capacity. Scanning electron microscopy images revealed an extensive distribution, morphological adaptation, and cell-to-cell connectivity in NSCs upon culture on the PCLF surface. MTT analysis showed that the NSCs had more survival rates on the PCLF surface compared to the laminin and control groups over time (p < 0.05). In contrast to the laminin group, Ki-67 analysis showed a decrease of proliferating cells in the PCLF group. Immunofluorescence staining revealed the prominent increase of Map-2 and GFAP reduction in NSCs from the PCLF group compared to the laminin and control groups, showing the stimulatory effect of PCLF on targeted maturation of NSCs (p < 0.05). In brief, PCLF based construct promotes NSCs morphological adaptation and neuronal differentiation, suggesting PCLF as an appropriate and applicable substrate in neural tissue engineering.

Hypoxia-Inducible Factor 1α (HIF-1α) Counteracts the Acute Death of Cells Transplanted into the Injured Spinal Cord

Cellular transplantation is in clinical testing for a number of central nervous system disorders, including spinal cord injury (SCI). One challenge is acute transplanted cell death. To prevent this death, there is a need to both establish when the death occurs and develop approaches to mitigate its effects. Here, using luciferase (luc) and green fluorescent protein (GFP) expressing Schwann cell (SC) transplants in the contused thoracic rat spinal cord 7 d postinjury, we establish via in vivo bioluminescent (IVIS) imaging and stereology that cell death occurs prior to 2–3 d postimplantation. We then test an alternative approach to the current paradigm of enhancing transplant survival by including multiple factors along with the cells. To stimulate multiple cellular adaptive pathways concurrently, we activate the hypoxia-inducible factor 1α (HIF-1α) transcriptional pathway. Retroviral expression of VP16-HIF-1α in SCs increased HIF-α by 5.9-fold and its target genes implicated in oxygen transport and delivery (VEGF, 2.2-fold) and cellular metabolism (enolase, 1.7-fold). In cell death assays in vitro, HIF-1α protected cells from H₂O₂-induced oxidative damage. It also provided some protection against camptothecin-induced DNA damage, but not thapsigargin-induced endoplasmic reticulum stress or tunicamycin-induced unfolded protein response. Following transplantation, VP16-HIF-1α increased SC survival by 34.3%. The increase in cell survival was detectable by stereology, but not by in vivo luciferase or ex vivo GFP IVIS imaging. The results support the hypothesis that activating adaptive cellular pathways enhances transplant survival and identifies an alternative pro-survival approach that, with optimization, could be amenable to clinical translation.

Columnar Injection for Intracerebral Cell Therapy

BACKGROUND

Surgical implantation of cellular grafts into the brain is of increasing importance, as stem cell-based therapies for Parkinson and other diseases continue to develop. The effect of grafting technique on development and survival of the graft has received less attention. Rate and method of graft delivery may impact the cell viability and success of these therapies. Understanding the final location of the graft with respect to the intended target location is also critical.

OBJECTIVE

To describe a "columnar injection" technique designed to reduce damage to host tissue and result in a column of graft material with greater surface area to volume ratio than traditional injection techniques.

METHODS

Using a clinically relevant model system of human embryonic stem cell-derived dopaminergic progenitors injected into athymic rat host brain, we describe a novel device that allows separate control of syringe barrel and plunger, permitting precise deposition of the contents into the cannula tract during withdrawal. Controls consist of contralateral injection using traditional techniques. Graft histology was examined at graft maturity.

RESULTS

Bolus grafts were centered on the injection tract but were largely proximal to the "target" location. These grafts displayed a conspicuous peripheral distribution of cells, particularly of mature dopaminergic neurons. In contrast, column injections remained centered at the intended target, contained more evenly distributed cells, and had significantly more mature dopaminergic neurons.

CONCLUSION

We suggest that this columnar injection technique may allow better engraftment and development of intracerebral grafts, enhancing outcomes of cell therapy, compared to fixed-point injection techniques.

Peptide-Based Scaffolds for the Culture and Transplantation of Human Dopaminergic Neurons

Cell replacement therapy is a promising treatment strategy for Parkinson's disease (PD); however, the poor survival rate of transplanted neurons is a critical barrier to functional recovery. In this study, we used self-assembling peptide nanofiber scaffolds (SAPNS) based on the peptide RADA16-I to support the in vitro maturation and in vivo post-transplantation survival of encapsulated human dopaminergic (DA) neurons derived from induced pluripotent stem cells. Neurons encapsulated within the SAPNS expressed mature neuronal and midbrain DA markers and demonstrated in vitro functional activity similar to neurons cultured in two dimensions. A microfluidic droplet generation method was used to encapsulate cells within monodisperse SAPNS microspheres, which were subsequently used to transplant adherent, functional networks of DA neurons into the striatum of a 6-hydroxydopamine-lesioned PD mouse model. SAPNS microspheres significantly increased the in vivo survival of encapsulated neurons compared with neurons transplanted in suspension, and they enabled significant recovery in motor function compared with control lesioned mice using approximately an order of magnitude fewer neurons than have been previously needed to demonstrate behavioral recovery. These results indicate that such biomaterial scaffolds can be used as neuronal transplantation vehicles to successfully improve the outcome of cell replacement therapies for PD. Impact Statement Transplantation of dopaminergic (DA) neurons holds potential as a treatment for Parkinson's disease (PD), but low survival rates of transplanted neurons is a barrier to successfully improving motor function. In this study, we used hydrogel scaffolds to transplant DA neurons into PD model mice. The hydrogel scaffolds enhanced survival of the transplanted neurons compared with neurons that were transplanted in a conventional manner, and they also improved recovery of motor function by using significantly fewer neurons than have typically been transplanted to see functional benefits. This cell transplantation technology has the capability to improve the outcome of neuron transplantation therapies.

Intra-cerebral implantation of a variety of collagenous scaffolds with nervous embryonic cells

Collagenous scaffolds provide good conditions for embryonic nerve cell growth. The aim of the current study was to assess the brains reaction to the implantation of 3D sponge-shaped scaffolds. These scaffolds consisted of collagen (Col) and Col with chondroitin sulphate, which is modified by carbodiimide, or Col crosslinked with dialdehyde cellulose. The current study also evaluated the expression of integrins α2 and β1 in embryonic nerve cells. Embryonic nerve cells were isolated from the brains of rat embryos. Acellular scaffolds, or scaffolds populated with embryonic nerve cells, were implanted into the rats brain. The fibers of all the implanted scaffolds remained intact and served as a template for cell infiltration. The implants induced minimal to moderate inflammatory responses and minimal glial scar formations. Immunohistochemical studies did not indicate any microtubule-associated protein 2 or glial fibrillary acidic protein-positive cells inside the scaffolds. Acellular and cell-populated scaffolds yielded similar responses in the brain. The expression of integrin α2 and β1 was observed in embryonic nervous cells. TC-I15, the integrin α2β1 inhibitor, was not demonstrated to modify cell entrapment within the collagenous scaffolds. All applied scaffolds were well tolerated by the tissue and were indicated to support blood vessel formation. Therefore, all tested biomaterials are recommended for further studies. Additional chemical modifications of the material are suggested to protect the seeded cells from apoptosis after implantation into the brain.

Interfacing cells with microengineered scaffolds for neural tissue reconstruction

The development of cellular microenvironments suitable for neural tissue engineering purposes involves a plethora of research fields ranging from cell biology to biochemistry, neurosciences, physics, nanotechnology, mechanobiology. In the last two decades, this multi-disciplinary activity has led to the emergence of numerous strategies to create architectures capable of reproducing the topological, biochemical and mechanical properties of the extracellular matrix present in the central (CNS) and peripheral nervous system (PNS). Some of these approaches have succeeded in inducing the functional recovery of damaged areas in the CNS and the PNS to address the current lack of effective medical treatments for this type of injury. In this review, we analyze recent developments in the realization of two-dimensional and three-dimensional neuronal scaffolds following either top-down or bottom-up approaches. After providing an overview of the different fabrication techniques employed for tailoring the biomaterials, we draw on specific examples to describe the major features of the developed approaches. We then conclude with prospective proof of concept studies on guiding scaffolds and regenerative models on macro-scale brain implants targeting neural regeneration.

Effect of canine mesenchymal stromal cells overexpressing heme oxygenase-1 in spinal cord injury

Heme oxygenase-1 (HO-1) is a stress-responsive enzyme that modulates the immune response and oxidative stress associated with spinal cord injury (SCI). This study aimed to investigate neuronal regeneration via transplantation of mesenchymal stromal cells (MSCs) overexpressing HO-1. Canine MSCs overexpressing HO-1 were generated by using a lentivirus packaging protocol. Eight beagle dogs with experimentally-induced SCI were divided into GFP-labeled MSC (MSC-GFP) and HO-1-overexpressing MSC (MSC-HO-1) groups. MSCs (1 × 10⁷ cells) were transplanted at 1 week after SCI. Spinal cords were harvested 8 weeks after transplantation, after which histopathological, immunofluorescence, and western blot analyses were performed. The MSC-HO-1 group showed significantly improved functional recovery at 7 weeks after transplantation. Histopathological results showed fibrotic changes and microglial cell infiltration were significantly decreased in the MSC-HO-1 group. Immunohistochemical (IHC) results showed significantly increased expression levels of HO-1 and neuronal markers in the MSC-HO-1 group. Western blot results showed significantly decreased expression of tumor necrosis factor-alpha, interleukin-6, cycloogygenase 2, phosphorylated-signal transducer and activator of transcription 3, and galactosylceramidase in the MSC-HO-1 group, while expression levels of glial fibrillary acidic protein, β3-tubulin, neurofilament medium, and neuronal nuclear antigen were similar to those observed in IHC results. Our results demonstrate that functional recovery after SCI can be promoted to a greater extent by transplantation of HO-1-overexpressing MSCs than by normal MSCs.

Combining Neuroprotective Treatment of Embryonic Nigral Donor Tissue with Mild Hypothermia of the Graft Recipient

Around 80–95% of the immature dopaminergic neurons die when embryonic ventral mesencephalic tissue is transplanted. Cell death occurs both during the preparation of donor tissue and after graft implantation, but the effect of combining successful neuroprotective treatments before and after transplantation has not been extensively investigated. We therefore treated embryonic rat mesencephalic tissue with a combination of the lipid peroxidation inhibitor tirilazad mesylate (3 μM) and the caspase inhibitor Ac.YVAD.cmk (500 μM) and transplanted the tissue into hemiparkinsonian rats kept hypothermic (32–33°C) or normothermic (37°C) during, and 90 min following, graft surgery. Suspension cell number did not differ between untreated or tirilazad/YVAD-treated preparations prior to transplantation. When graft survival was evaluated 6 weeks after implantation, both tirilazad/YVAD pretreatment and mild hypothermia increased the survival of transplanted dopaminergic neurons. Approximately 50–57% of the embryonic dopaminergic neurons survived the dissociation and grafting procedure in rats rendered hypothermic, but there was no significant additive effect on graft survival with a combined treatment. All groups of rats exhibited behavioral recovery in the amphetamine-induced rotation test. There was a significantly enhanced functional capacity of grafts placed in hypothermic as compared to normothermic rats. However, tirilazad/YVAD pretreated implants did not afford greater behavioral improvement than control-treated grafts. Our results suggest that neuroprotective treatments administered prior to and immediately after neural graft implantation may under certain conditions rescue, at least in part, the same subset of dopaminergic neurons. The study also emphasizes the importance of the immediate time after grafting for transplant survival, with relevance both for primary mesencephalic implants and stem cell grafts.

β1 Integrin as a Xenoantigen in Fetal Porcine Mesencephalic Cells Transplanted into the Rat Brain

Xenografts of fetal porcine mesencephalic cells implanted into the rat striatum are generally rejected within several weeks. The fetal donor mesencephalon predominantly consists of neurons, but also contains microglial and endothelial cells, which are more immunogenic. In the present work, we investigated the occurrence of donor endothelial cells in grafts of porcine mesencephalic cells implanted into the rat striatum. Pig endothelial cells were monitored by immunochemical methods, using a monoclonal antibody (mAb) that recognizes a peptidic epitope of the porcine β1 integrin, and isolectin IB4, for the staining of the Galα1,3Gal epitope. The analysis also involved the detection of the pig hyaluronate receptor CD44, and the cell adhesion molecule CD31. The anti-β1 integrin mAb revealed endothelial-like cells in grafts of porcine mesencephalic cells as soon as 1 week after implantation. A similar staining pattern was obtained with the IB4 lectin. Unlike aortic endothelial cells, these pig brain-derived endothelial-like cells were not recognized by the anti-CD44 antibody. They also failed to express the CD31 adhesion molecule, a fact which suggests that they remained poorly mature, even in grafts maintained during 45 days in immunosuppressed rats. Interestingly, a strong expression of β1 integrin immunoreactivity was noticed in a large proportion (80%) of the cells freshly dissociated from the fetal pig mesencephalic tissue. The immunoreactivity decreased progressively after transplantation of the cells into the rat brain. This observation suggests that dissociated neuroblasts are capable of a temporary expression of β1 integrin. This molecule is known to participate in the process of cell sorting and migration in the developing brain. Hence, its expression could be the hallmark of a rescue mechanism triggered by the disruption of the cell/matrix interactions during the dissociation of the fetal mesencephalon. This disruption might account for part of the dramatic cell death process that occurs during the manipulation of the donor tissue.

Derivation of Functional Dopamine Neurons from Embryonic Stem Cells

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the selective degeneration of dopaminergic (DA) neurons in the substantia nigra of the midbrain. Pharmacological treatment of PD has been a prevailing strategy. However, it has some limitations because its effectiveness gradually decreases and side effects develop. As an alternative, cell transplantation therapy has been tried. Although transplantation of fetal ventral mesencephalic cells looks promising for the treatment of PD in some cases, ethical and technical problems in obtaining large numbers of human fetal brain tissues also lead to difficulty in its clinical application. Our recent studies showed that a high yield of DA neurons could be derived from embryonic stem (ES) cells and they efficiently induced behavioral recovery in a PD animal model. Here we summarize methods for generation of functional DA neurons from ES cells for application to PD models.

Pretreatment of Mouse Neural Stem Cells with Carbon Monoxide-Releasing Molecule-2 Interferes with NF-κB p65 Signaling and Suppresses Iron Overload-Induced Apoptosis

Neural stem cell (NSC) transplantation is a promising approach to repair the damaged brain after hemorrhagic stroke; however, it is largely limited by the poor survival of donor cells. Breakdown products of the hematoma and subsequent iron overload contribute to the impairment of survival of neural cells. There is little information regarding the mechanism involved in the death of grafted cells. Furthermore, therapeutic research targeted to improving the survival of grafted neural stem cells (NSCs) is strikingly lacking. Here, we showed that iron overload induced apoptosis of C17.2 cells, a cell line originally cloned from mouse NSCs and immortalized by v-myc. Pretreatment with carbon monoxide-releasing molecule-2 (CORM-2) markedly protected C17.2 cells against iron overload in a dose-dependent manner. Moreover, CORM-2 interfered with NF-κB signaling, including inhibition of nuclear translocation and down-regulation of NF-κB p65. TUNEL staining showed that preconditioning C17.2 cells with CORM-2 enhanced their resistance to apoptosis induced by iron overload, which was concomitant with down-regulation of the pro-apoptotic proteins (Bax and cleaved caspase-3) and up-regulation of the anti-apoptotic protein Bcl2. The protective effect of CORM-2 could be simulated by BAY11-7082, a special inhibitor of NF-κB p65. These results provide a novel and effective strategy to enhance the survival of NSCs after transplantation and, therefore, their efficacy in repairing brain injury due to hemorrhagic stroke.

Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity

Cell transplantation therapies in the nervous system are frequently hampered by glial scarring and cell drain from the damaged site, among others. To improve this situation, new biomaterials may be of help. Here, novel single-channel tubular conduits based on hyaluronic acid (HA) with and without poly-l-lactide acid fibers in their lumen were fabricated. Rat Schwann cells were seeded within the conduits and cultured for 10days. The conduits possessed a three-layered porous structure that impeded the leakage of the cells seeded in their interior and made them impervious to cell invasion from the exterior, while allowing free transport of nutrients and other molecules needed for cell survival. The channel's surface acted as a template for the formation of a cylindrical sheath-like tapestry of Schwann cells continuously spanning the whole length of the lumen. Schwann-cell tubes having a diameter of around 0.5mm and variable lengths can thus be generated. This structure is not found in nature and represents a truly engineered tissue, the outcome of the specific cell-material interactions. The conduits might be useful to sustain and protect cells for transplantation, and the biohybrids here described, together with neuronal precursors, might be of help in building bridges across significant distances in the central and peripheral nervous system.

STATEMENT OF SIGNIFICANCE

The paper entitled "Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity" reports on the development of a novel tubular scaffold and on how this scaffold acts on Schwann cells seeded in its interior as a template to produce macroscopic hollow continuous cylinders of tightly joined Schwann cells. This cellular structure is not found in nature and represents a truly engineered novel tissue, which obtains as a consequence of the specific cell-material interactions within the scaffold.

Polyglutamine (PolyQ) diseases: genetics to treatments

The polyglutamine (polyQ) diseases are a group of neurodegenerative disorders caused by expanded cytosine-adenine-guanine (CAG) repeats encoding a long polyQ tract in the respective proteins. To date, a total of nine polyQ disorders have been described: six spinocerebellar ataxias (SCA) types 1, 2, 6, 7, 17; Machado-Joseph disease (MJD/SCA3); Huntington's disease (HD); dentatorubral pallidoluysian atrophy (DRPLA); and spinal and bulbar muscular atrophy, X-linked 1 (SMAX1/SBMA). PolyQ diseases are characterized by the pathological expansion of CAG trinucleotide repeat in the translated region of unrelated genes. The translated polyQ is aggregated in the degenerated neurons leading to the dysfunction and degeneration of specific neuronal subpopulations. Although animal models of polyQ disease for understanding human pathology and accessing disease-modifying therapies in neurodegenerative diseases are available, there is neither a cure nor prevention for these diseases, and only symptomatic treatments for polyQ diseases currently exist. Long-term pharmacological treatment is so far disappointing, probably due to unwanted complications and decreasing drug efficacy. Cellular transplantation of stem cells may provide promising therapeutic avenues for restoration of the functions of degenerative and/or damaged neurons in polyQ diseases.

Endogenous cerebellar neurogenesis in adult mice with progressive ataxia

OBJECTIVE

Transplanting exogenous neuronal progenitors to replace damaged neurons in the adult brain following injury or neurodegenerative disorders and achieve functional amelioration is a realistic goal. However, studies so far have rarely taken into consideration the preexisting inflammation triggered by the disease process that could hamper the effectiveness of transplanted cells. Here, we examined the fate and long-term consequences of human cerebellar granule neuron precursors (GNP) transplanted into the cerebellum of Harlequin mice, an adult model of progressive cerebellar degeneration with early-onset microgliosis.

METHODS

Human embryonic stem cell-derived progenitors expressing Atoh1, a transcription factor key to GNP specification, were generated in vitro and stereotaxically transplanted into the cerebellum of preataxic Harlequin mice. The histological and functional impact of these transplants was followed using immunolabeling and Rotarod analysis.

RESULTS

Although transplanted GNPs did not survive beyond a few weeks, they triggered the proliferation of endogenous nestin-positive precursors in the leptomeninges that crossed the molecular layer and differentiated into mature neurons. These phenomena were accompanied by the preservation of the granule and Purkinje cell layers and delayed ataxic changes. In vitro neurosphere generation confirmed the enhanced neurogenic potential of the cerebellar leptomeninges of Harlequin mice transplanted with exogenous GNPs.

INTERPRETATION

The cerebellar leptomeninges of adult mice contain an endogenous neurogenic niche that can be stimulated to yield mature neurons from an as-yet unidentified population of progenitors. The transplantation of human GNPs not only stimulates this neurogenesis, but, despite the potentially hostile environment, leads to neuroprotection and functional amelioration.

Cell-microsphere constructs formed with human adipose-derived stem cells and gelatin microspheres promotes stemness, differentiation, and controlled pro-angiogenic potential

Translation of stem cell therapies to clinical stage requires viable delivery vehicles that can control stem cell behavior. In this study, the suitability of gelatin microspheres (GMs) as such a tissue engineering platform for human adipose derived stem cells (ADSCs) is investigated. ADSCs on GMs, show a significant upregulation of well known pluripotent marker genes, together with the ability to differentiate into multiple cell lineages of adipocytes, osteocytes, and hepatocytes. In addition, the pro-angiogenic ability of ADSC-GMs is also enhanced compared to ADSCs on 2D culture plates. These results suggest that GMs can be a suitable culture platform for ADSCs with enhanced therapeutic potential.

Maintenance of Viability and Function of Rat Islets With the Use of ROCK Inhibitor Y-27632

The number of patients with diabetes is on an increasing trend, thus leading to the belief that diabetes will be the largest medical problem of the 21st century. Islet transplantation can improve glycometabolic control in patients with type 1 diabetes. We studied the viability of Rho-associated protein kinase (ROCK) inhibitor Y-27632 in a culture system in vitro on freshly isolated rat islets. Islet isolation was conducted on a Lewis rat, and studies of culture solutions were split into two groups, one group using ROCK inhibitor Y-27632, and another without. On the seventh day of culture, we evaluated the differences for the cell morphology, viability, and insulin secretion. The Y-27632 group maintained form better than the group without Y-27632. With strong expression of Bcl-2 observed with the Y-27632 group, and expression suppressed with Bax, inhibition of apoptosis by Y-27632 was confirmed. The Y-27632 group predominantly secreted insulin. For islet transplantation, Y-27632 inhibited cell apoptosis in a graft and was also effective in promoting insulin secretion. We were able to confirm effective morphological and functional culture maintenance by separating islets from a rat and adding ROCK inhibitor Y-27632 to the medium.

Acute stimulation of transplanted neurons improves motoneuron survival, axon growth, and muscle reinnervation

Few options exist for treatment of pervasive motoneuron death after spinal cord injury or in neurodegenerative diseases such as amyotrophic lateral sclerosis. Local transplantation of embryonic motoneurons into an axotomized peripheral nerve is a promising approach to arrest the atrophy of denervated muscles; however, muscle reinnervation is limited by poor motoneuron survival. The aim of the present study was to test whether acute electrical stimulation of transplanted embryonic neurons promotes motoneuron survival, axon growth, and muscle reinnervation. The sciatic nerve of adult Fischer rats was transected to mimic the widespread denervation seen after disease or injury. Acutely dissociated rat embryonic ventral spinal cord cells were transplanted into the distal tibial nerve stump as a neuron source for muscle reinnervation. Immediately post-transplantation, the cells were stimulated at 20 Hz for 1 h. Other groups were used to control for the cell transplantation and stimulation. When neurons were stimulated acutely, there were significantly more neurons, including cholinergic neurons, 10 weeks after transplantation. This led to enhanced numbers of myelinated axons, reinnervation of more muscle fibers, and more medial and lateral gastrocnemius muscles were functionally connected to the transplant. Reinnervation reduced muscle atrophy significantly. These data support the concept that electrical stimulation rescues transplanted motoneurons and facilitates muscle reinnervation.

The survival of engrafted neural stem cells within hyaluronic acid hydrogels

Successful cell-based therapy of neurological disorders is highly dependent on the survival of transplanted stem cells, with the overall graft survival of naked, unprotected cells in general remaining poor. We investigated the use of an injectable hyaluronic acid (HA) hydrogel for enhancement of survival of transplanted mouse C17.2 cells, human neural progenitor cells (ReNcells), and human glial-restricted precursors (GRPs). The gelation properties of the HA hydrogel were first characterized and optimized for intracerebral injection, resulting in a 25 min delayed-injection after mixing of the hydrogel components. Using bioluminescence imaging (BLI) as a non-invasive readout of cell survival, we found that the hydrogel can protect xenografted cells as evidenced by the prolonged survival of C17.2 cells implanted in immunocompetent rats (p < 0.01 at day 12). The survival of human ReNcells and human GRPs implanted in the brain of immunocompetent or immunodeficient mice was also significantly improved after hydrogel scaffolding (ReNcells, p < 0.05 at day 5; GRPs, p < 0.05 at day 7). However, an inflammatory response could be noted two weeks after injection of hydrogel into immunocompetent mice brains. We conclude that hydrogel scaffolding increases the survival of engrafted neural stem cells, justifying further optimization of hydrogel compositions.

Neurotrophic effects of leukemia inhibitory factor on neural cells derived from human embryonic stem cells

Various growth factor cocktails have been used to proliferate and then differentiate human neural progenitor (NP) cells derived from embryonic stem cells (ESC) for in vitro and in vivo studies. However, the cytokine leukemia inhibitory factor (LIF) has been largely overlooked. Here, we demonstrate that LIF significantly enhanced in vitro survival and promoted differentiation of human ESC-derived NP cells. In NP cells, as well as NP-derived neurons, LIF reduced caspase-mediated apoptosis and reduced both spontaneous and H2O2-induced reactive oxygen species in culture. In vitro, NP cell proliferation and the yield of differentiated neurons were significantly higher in the presence of LIF. In NP cells, LIF enhanced cMyc phosphorylation, commonly associated with self-renewal/proliferation. Also, in differentiating NP cells LIF activated the phosphoinositide 3-kinase and signal transducer and activator of transcription 3 pathways, associated with cell survival and reduced apoptosis. When differentiated in LIF+ media, neurite outgrowth and ERK1/2 phosphorylation were potentiated together with increased expression of gp130, a component of the LIF receptor complex. NP cells, pretreated in vitro with LIF, were effective in reducing infarct volume in a model of focal ischemic stroke but LIF did not lead to significantly improved initial NP cell survival over nontreated NP cells. Our results show that LIF signaling significantly promotes human NP cell proliferation, survival, and differentiation in vitro. Activated LIF signaling should be considered in cell culture expansion systems for future human NP cell-based therapeutic transplant studies.

Encapsulation of Mesenchymal Stem Cells by Bioscaffolds Protects Cell Survival and Attenuates Neuroinflammatory Reaction in Injured Brain Tissue after Transplantation

Since the brain is naturally inefficient in regenerating functional tissue after injury or disease, novel restorative strategies including stem cell transplantation and tissue engineering have to be considered. We have investigated the use of such strategies in order to achieve better functional repair outcomes. One of the fundamental challenges of successful transplantation is the delivery of cells to the injured site while maintaining cell viability. Classical cell delivery methods of intravenous or intraparenchymal injections are plagued by low engraftment and poor survival of transplanted stem cells. Novel implantable devices such as 3D bioactive scaffolds can provide the physical and metabolic support required for successful progenitor cell engraftment, proliferation, and maturation. In this study, we performed in situ analysis of laminin-linked dextran and gelatin macroporous scaffolds. We revealed the protective action of gelatin–laminin (GL) scaffolds seeded with mesenchymal stem cells derived from donated human Wharton's jelly (hUCMSCs) against neuroinflammatory reactions of injured mammalian brain tissue. These bioscaffolds have been implanted into (i) intact and (ii) ischemic rat hippocampal organotypic slices and into the striatum of (iii) normal and (iv) focally injured brains of adult Wistar rats. We found that transplantation of hUCMSCs encapsulated in GL scaffolds had a significant impact on the prevention of glial scar formation (low glial acidic fibrillary protein) and in the reduction of neuroinflammation (low interleukin-6 and the microglial markers ED1 and Iba1) in the recipient tissue. Moreover, implantation of hUCMSCs encapsulated within GL scaffolds induced matrix metalloproteinase-2 and -9 proteolytic activities in the surrounding brain tissue. This facilitated scaffold biodegradation while leaving the remaining grafted hUCMSCs untouched. In conclusion, transplanting GL scaffolds preseeded with hUCMSCs into mammalian brain tissue escaped the host's immune system and protected neural tissue from neuroinflammatory injury. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Characterization of embryonic cortical neuron death in prolonged cell suspension

Cell transplantation may be an effective therapeutic strategy for many neurodegenerative diseases. However, difficulty in obtaining a sufficient amount of donor cells and low graft survival are two major limiting factors. Dissociation of cells from tissues or culture is an inevitable step for cell transplantation, and cell viability in suspension may influence the outcome of the cell therapy. To this end, we asked whether the suspension time of freshly dissociated neurons in vitro affects their viability. Following 4-24h cell suspension, primary cortical neurons underwent cell death. Interestingly, the neurons exhibited only marginal caspase-3 immunoreactivity with very few sub-G1 apoptotic cell proportions in flow cytometry. In addition, the suppression of caspase-3 or Bax action failed to prevent cell death of primary cortical neurons, indicating minimal apoptotic cell death. On the other hand, there was a marked increase in the TdT-mediated dUTP nick end labeling-positive and propidium iodide-labeled necrotic cells (∼50%) with enhanced poly [ADP-ribose] polymerase-1 activity. Therefore, prevention against necrosis rather than apoptosis may be required for optimal benefits in cell transplantation.

Parkinson's disease: from genetics to treatments

Parkinson's disease (PD) is a common neurodegenerative disease and typically presents with tremor, rigidity, bradykinesia, and postural instability. The hallmark pathological features of PD are loss of dopaminergic neurons in the substantia nigra (SN) and the presence of neuronal intracellular Lewy body (LB) inclusions. In general, PD is sporadic; however, familial PD, while uncommon, can be inherited in an autosomal dominant (AD) or autosomal recessive (AR) manner. The molecular investigations of proteins encoded by PD-linked genes have clarified that ADPD is associated with α-synuclein and LRRK2, while ARPD is linked to Parkin, PINK1, DJ1, and ATP13A2. Understanding these genes can bring insights into this disease and create possible genetic tests for early diagnosis. Long-term pharmacological treatment is so far disappointing, probably due to unwanted complications and decreasing drug efficacy. Several strategies have been proposed and tested as alternatives for PD. Cellular transplantation of dopamine-secreting stem cells opens the door to new therapeutic avenues for restoration of the functions of degenerative and/or damaged neurons in PD.

Motoneuron replacement for reinnervation of skeletal muscle in adult rats

Reinnervation is needed to rescue muscle when motoneurons die in disease or injury. Embryonic ventral spinal cord cells transplanted into peripheral nerve reinnervate muscle and reduce atrophy, but low motoneuron survival may limit motor unit formation. We tested whether transplantation of a purified population of embryonic motoneurons into peripheral nerve (mean ± SE, 146,458 ± 4,011 motoneurons) resulted in more motor units and reinnervation than transplantation of a mixed population of ventral spinal cord cells (72,075 ± 12,329 motoneurons). Ten weeks after either kind of transplant, similar numbers of neurons expressed choline acetyl transferase and/or Islet-1. Motoneuron numbers always exceeded the reinnervated motor unit count. Most motor end plate were simple plaques. Reinnervation significantly reduced muscle fiber atrophy. These data show that the number of transplanted motoneurons and motoneuron survival do not limit muscle reinnervation. Incomplete differentiation of motoneurons in nerve and lack of muscle activity may result in immature neuromuscular junctions that limit reinnervation and function.

Functional recovery after spinal cord injury in dogs treated with a combination of Matrigel and neural-induced adipose-derived mesenchymal Stem cells

BACKGROUND AIMS

Previous studies have reported that scaffold or cell-based transplantation may improve functional recovery following spinal cord injury (SCI), but these results were based on neuronal regeneration and cell replacement. In this study, we investigated whether a combination of Matrigel and neural-induced mesenchymal stem cells (NMSC) improved hindlimb function in dogs with SCI, and what mechanisms were involved.

METHODS

We pre-differentiated canine adipose-derived mesenchymal stem cells into NMSC. A total of 12 dogs subjected to SCI procedures were assigned to one of the following three transplantation treatment groups: phosphate-buffered saline (PBS); Matrigel; or Matrigel seeded with NMSC. Treatment occurred 1 week after SCI. Basso, Beattie and Bresnahan (B.B.B.) and Tarlov scores, histopathology, immunofluorescence staining and Western blot analysis were used to evaluate the treatment effects.

RESULTS

Compared with dogs administered PBS or Matrigel alone, dogs treated with Matrigel + NMSC showed significantly better functional recovery 8 weeks after transplantation. Histology and immunochemical analysis revealed that the combination of Matrigel + NMSC reduced fibrosis from secondary injury processes and improved neuronal regeneration more than the other treatments. In addition, the combination of Matrigel + NMSC decreased the expression of inflammation and/or astrogliosis markers. Increased expressions of intracellular molecules related to neuronal extension, neuronal markers and neurotrophic factors were also found in the Matrigel + NMSC group. However, the expression of nestin as a neural stem cell marker was increased with Matrigel alone.

CONCLUSIONS

The combination of Matrigel + NMSC produced beneficial effects in dogs with regard to functional recovery following SCI through enhancement of anti-inflammation, anti-astrogliosis, neuronal extension and neuronal regeneration effects.

Evaluation of the use of an induced puripotent stem cell sheet for the construction of tissue-engineered vascular grafts

OBJECTIVE

The development of a living, tissue-engineered vascular graft (TEVG) holds great promise for advancing the field of cardiovascular surgery. However, the ultimate source and time needed to procure these cells remain problematic. Induced puripotent stem (iPS) cells have recently been developed and have the potential for creating a pluripotent cell line from a patient's own somatic cells. In the present study, we evaluated the use of a sheet created from iPS cell-derived vascular cells as a potential source for the construction of TEVG.

METHODS

Male mouse iPS cells were differentiated into embryoid bodies using the hanging-drop method. Cell differentiation was confirmed by a decrease in the proportion of SSEA-1-positive cells over time using fluorescence-activated cell sorting. The expression of endothelial cell and smooth muscle cell markers was detected using real-time polymerase chain reaction (PCR). The differentiated iPS cell sheet was made using temperature-responsive dishes and then seeded onto a biodegradable scaffold composed of polyglycolic acid-poly-l-lactide and poly(l-lactide-co-ε-caprolactone) with a diameter of 0.8 mm. These scaffolds were implanted as interposition grafts in the inferior vena cava of female severe combined immunodeficiency/beige mice (n = 15). Graft function was serially monitored using ultrasonography. The grafts were analyzed at 1, 4, and 10 weeks with histologic examination and immunohistochemistry. The behavior of seeded differentiated iPS cells was tracked using Y-chromosome fluorescent in situ hybridization and SRY real-time PCR.

RESULTS

All mice survived without thrombosis, aneurysm formation, graft rupture, or calcification. PCR evaluation of iPS cell sheets in vitro demonstrated increased expression of endothelial cell markers. Histologic evaluation of the grafts demonstrated endothelialization with von Willebrand factor and an inner layer with smooth muscle actin- and calponin-positive cells at 10 weeks. The number of seeded differentiated iPS cells was found to decrease over time using real-time PCR (42.2% at 1 week, 10.4% at 4 weeks, 9.8% at 10 weeks). A fraction of the iPS cells were found to be Y-chromosome fluorescent positive at 1 week. No iPS cells were found to co-localize with von Willebrand factor or smooth muscle actin-positive cells at 10 weeks.

CONCLUSIONS

Differentiated iPS cells offer an alternative cell source for constructing TEVG. Seeded iPS cells exerted a paracrine effect to induce neotissue formation in the acute phase and were reduced in number by apoptosis at later time points. Sheet seeding of our TEVG represents a viable mode of iPS cell delivery over time.

A calpain inhibitor enhances the survival of Schwann cells in vitro and after transplantation into the injured spinal cord

Despite the diversity of cells available for transplantation into sites of spinal cord injury (SCI), and the known ability of transplanted cells to integrate into host tissue, functional improvement associated with cellular transplantation has been limited. One factor potentially limiting the efficacy of transplanted cells is poor cell survival. Recently we demonstrated rapid and early death of Schwann cells (SCs) within the first 24 h after transplantation, by both necrosis and apoptosis, which results in fewer than 20% of the cells surviving beyond 1 week. To enhance SC transplant survival, in vitro and in vivo models to rapidly screen compounds for their ability to promote SC survival are needed. The current study utilized in vitro models of apoptosis and necrosis, and based on withdrawal of serum and mitogens and the application of hydrogen peroxide, we screened several inhibitors of apoptosis and necrosis. Of the compounds tested, the calpain inhibitor MDL28170 enhanced SC survival both in vitro in response to oxidative stress induced by application of H2O2, and in vivo following delayed transplantation into the moderately contused spinal cord. The results support the use of calpain inhibitors as a promising new treatment for promoting the survival of transplanted cells. They also suggest that in vitro assays for cell survival may be useful for establishing new compounds that can then be tested in vivo for their ability to promote transplanted SC survival.

Cell transplantation and gene therapy in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disorder affecting, in part, dopaminergic motor neurons of the ventral midbrain and their terminal projections that course to the striatum. Symptomatic strategies focused on dopamine replacement have proven effective at remediating some motor symptoms during the course of disease but ultimately fail to deliver long-term disease modification and lose effectiveness due to the emergence of side effects. Several strategies have been experimentally tested as alternatives for Parkinson's disease, including direct cell replacement and gene transfer through viral vectors. Cellular transplantation of dopamine-secreting cells was hypothesized as a substitute for pharmacotherapy to directly provide dopamine, whereas gene therapy has primarily focused on restoration of dopamine synthesis or neuroprotection and restoration of spared host dopaminergic circuitry through trophic factors as a means to enhance sustained controlled dopamine transmission. This seems now to have been verified in numerous studies in rodents and nonhuman primates, which have shown that grafts of fetal dopamine neurons or gene transfer through viral vector delivery can lead to improvements in biochemical and behavioral indices of dopamine deficiency. However, in clinical studies, the improvements in parkinsonism have been rather modest and variable and have been plagued by graft-induced dyskinesias. New developments in stem-cell transplantation and induced patient-derived cells have opened the doors for the advancement of cell-based therapeutics. In addition, viral-vector-derived therapies have been developed preclinically with excellent safety and efficacy profiles, showing promise in clinical trials thus far. Further progress and optimization of these therapies will be necessary to ensure safety and efficacy before widespread clinical use is deemed appropriate.

Enhanced functional properties of corneal epithelial cells by coculture with embryonic stem cells via the integrin β1-FAK-PI3K/Akt pathway

Adult stem cells are important cell sources in regenerative medicine, but isolating them is technically challenging. This study employed a novel strategy to generate stem-like corneal epithelial cells and promote the functional properties of these cells by coculture with embryonic stem cells. The primary corneal epithelial cells were labelled with GFP and cocultured with embryonic stem cells in a transwell or by direct cell-cell contact. The embryonic stem cells were pre-transfected with HSV-tk-puro plasmids and became sensitive to ganciclovir. After 10 days of coculture, the corneal epithelial cells were isolated by treating the cultures with ganciclovir to kill the embryonic stem cells. The expression of stem cell-associated markers (ABCG2, p63) increased whereas the differentiation mark (Keratin 3) decreased in corneal epithelial cells isolated from the cocultures as evaluated by RT-PCR and flow cytometry. Their functional properties of corneal epithelial cells, including cell adhesion, migration and proliferation, were also enhanced. These cells could regenerate a functional stratified corneal epithelial equivalent but did not form tumors. Integrin β1, phosphorylated focal adhesion kinase and Akt were significantly upregulated in corneal epithelial cells. FAK Inhibitor 14 that suppressed the expression of phosphorylated focal adhesion kinase and Akt inhibited cell adhesion, migration and proliferation. LY294002 that suppressed phosphorylated Akt but not phosphorylated focal adhesion kinase inhibited cell proliferation but had no effect on cell adhesion or migration. These findings demonstrated that the functional properties of stem-like corneal epithelial cells were enhanced by cocultured embryonic stem cells via activation of the integrin β1-FAK-PI3K/Akt signalling pathway.

TGF-β2 treatment enhances cytoprotective factors released from embryonic stem cells and inhibits apoptosis in infarcted myocardium

We investigated whether factors released from mouse embryonic stem (ES) cells primed with and without transforming growth factor (TGF)-β2 inhibit iodoacetic acid (IAA)- and H(2)O(2)-induced apoptosis in the cell culture system as well as after transplantation in the infarcted heart. We generated conditioned media (CMs) from ES cells primed with and without TGF-β2 and determined their effects on IAA- and H(2)O(2)-induced apoptosis in H9c2 cells. We also transplanted both ES-CMs in the infarcted heart to determine the effects on apoptosis and cardiac function after myocardial infarction (MI) at day (D)1 and D14. Terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining, apoptotic ELISA, and cell viability data demonstrated significantly (P < 0.05) reduced apoptosis with ES-CM compared with controls in both cell culture models. Moreover, TGF-β2-primed ES-CM (T-ES-CM) demonstrated enhanced beneficial effects, with further reduced (P < 0.05) apoptosis compared with ES-CM, suggesting the a presence of additional cytoprotective released factors after TGF-β2 treatment. Next, our in vivo apoptosis data suggested significant decrease in apoptosis with both ES-CMs compared with MI alone at D1 and D14. Notably, T-ES-CM demonstrated significant (P < 0.05) inhibition of apoptosis and fibrosis with improved cardiac function compared with ES-CM at D14, whereas no such effects were observed at D1. Next, we confirmed that apoptosis is mediated through a prosurvival Akt pathway. Moreover, we determined that after TGF-β2 treatment there was a two- to fivefold increase in cytoprotective released factors (interleukin-10, stem cell factor, tissue inhibitor of matrix metalloproteinase-1, and VEGF) with T-ES-CM compared with ES-CM. In conclusion, we suggest that factors released from ES cells with and without TGF-β2 treatment contain antiapoptotic factors that inhibit apoptosis in vitro and in vivo. We also suggest that T-ES-CM demonstrates additional beneficial effects that provide useful information for future therapeutic applications in regenerative medicine.

Neurotrophic factors improve muscle reinnervation from embryonic neurons

Motoneurons die in diseases like amyotrophic lateral sclerosis and after spinal cord trauma, inducing muscle denervation. We tested whether transplantation of embryonic cells with neurotrophic factors into peripheral nerve of adult rats improves muscle reinnervation and motor unit function more than cells alone. One week after sciatic nerve section, embryonic ventral spinal cord cells were transplanted into the tibial nerve with or without glial cell line-derived neurotrophic factor, hepatocyte growth factor, and insulin-like growth factor-1. These cells represented the only neuron source for muscle reinnervation. Ten weeks after transplantation, all medial gastrocnemius muscles contracted in response to electrical stimulation of cell transplants with factors. Only 80% of muscles responded with cells alone. Factors and cells resulted in survival of more motoneurons and reinnervation of more muscle fibers for a given axon (motor unit) number. Greater reinnervation from embryonic cells may enhance muscle excitation by patterned electrical stimulation.

Enhancement of long-term proliferative capacity of rabbit corneal epithelial cells by embryonic stem cell conditioned medium

Induction of autologous stem cells for directed differentiation has become a predominant method to obtain autologous cells for tissue reconstruction. However, the low inducing efficiency and contamination with other type of cells hinder its clinical utilization. Here we report a novel phenomenon that the corneal epithelial cells maintain long-term proliferative capacity and tissue-specific cell phenotype by factors secreted from murine embryonic stem cells (ESCs). The rabbit corneal epithelial cells grew very well in culture medium with addition of 40% ESC conditioned medium (ESC-CM). These corneal epithelial cells have been serially subcultured for more than 20 passages and maintained high cell purity, cobble-stone-like morphology, enhanced colony forming efficiency, normal diploid, and capacity to regenerate a functional stratified corneal epithelial equivalent. More importantly, these cells did not form tumor, and the cells lost their proliferative capacity after withdrawal of ESC-CM. The long-term proliferative capacity of corneal epithelial cells is partly resulted from enhancement of cell survival and colony formation, and mediated by ectopic expression of telomerase. Our findings indicate that this new ESC-CM culture system can generate low-immunogenic autologous cells sufficiently for use in regenerative medicine.

Organotypic spinal cord slice culture to study neural stem/progenitor cell microenvironment in the injured spinal cord

The molecular microenvironment of the injured spinal cord does not support survival and differentiation of either grafted or endogenous NSCs, restricting the effectiveness of the NSC-based cell replacement strategy. Studying the biology of NSCs in in vivo usually requires a considerable amount of time and cost, and the complexity of the in vivo system makes it difficult to identify individual environmental factors. The present study sought to establish the organotypic spinal cord slice culture that closely mimics the in vivo environment. The cultured spinal cord slices preserved the cytoarchitecture consisting of neurons in the gray matter and interspersed glial cells. The majority of focally applied exogenous NSCs survived up to 4 weeks. Pre-exposure of the cultured slices to a hypoxic chamber markedly reduced the survival of seeded NSCs on the slices. Differentiation into mature neurons was severely limited in this co-culture system. Endogenous neural progenitor cells were marked by BrdU incorporation, and applying an inflammatory cytokine IL-1β significantly increased the extent of endogenous neural progenitors with the oligodendrocytic lineage. The present study shows that the organotypic spinal cord slice culture can be properly utilized to study molecular factors from the post-injury microenvironment affecting NSCs in the injured spinal cord.

Hepatocyte growth factor protects human embryonic stem cell derived-neural progenitors from hydrogen peroxide-induced apoptosis

Promoting human embryonic stem cell (hESC)-derived-neural progenitor survival in the pro-apoptotic niche is pivotal for stem cell replacement therapy. The present study was designed to investigate the protective effect of hepatocyte growth factor (HGF) on hESC-derived neural progenitor injured by hydrogen peroxide (H(2)O(2)) exposure. Treatment of hESC-derived neural progenitor cells with HGF prior to H(2)O(2) exposure conferred protective effect against oxidative stress-induced apoptosis. HGF treatment increased both phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation. However, selective inhibition of each pathway supported that the activation of PI3K/AKT, but not ERK1/2, provides survival advantage to the neural progenitor cells. Further investigation indicated that HGF pretreatment could attenuate the decrease of the expression of Bcl-2 protein induced by H(2)O(2), whereas the level of Bax was not affected. Additionally, we observed that H(2)O(2)-induced decrease of mitochondrial transmembrane potential, release of cytochrome c and increase of caspase-3 activation were alleviated by HGF pretreatment. These effects of HGF could be reversed by inhibition of the PI3K/Akt and ERKs pathways, indicating PI3K/Akt and ERKs signaling might be involved in HGF-mediated regulation of mitochondrial apoptotic pathway mediated by H(2)O(2). The neuroprotective effect of HGF might potentially be useful in stem cell-based therapies for neurodegenerative disorders.

Cell-based therapeutic approaches for Parkinson's disease: progress and perspectives

Motor dysfunctions in Parkinson's disease are believed to be primarily due to the degeneration of dopaminergic neurons located in the substantia nigra pars compacta. Because a single-type cell population is depleted, Parkinson's disease is considered a primary target for cell replacement-based therapeutic strategies. Extensive studies have confirmed transplantation of donor neurons could be beneficial, yet identifying an alternative cell source is clearly essential. Human embryonic stem cells (hESCs) have been proposed as a renewable source of dopaminergic neurons for transplantation in Parkinson's disease; other potential sources could include neural stem cells (hNSCs) and adult mesenchymal stem cells (hMSCs). However, numerous difficulties avert practical application of stem cell-based therapeutic approaches for the treatment of Parkinson's disease. Among the latter, ethical, safety (including xeno- and tumor formation-associated risks) and technical issues stand out. This review aims to provide a balanced and updated outlook on various issues associated with stem cells in regard to their potential in the treatment of Parkinson's disease. Essential features of the individual stem cell subtypes, principles of available differentiation protocols, transplantation, and safety issues are discussed extensively.

Matrigel supports survival and neuronal differentiation of grafted embryonic stem cell-derived neural precursor cells

Cell replacement therapy holds great promise as a means of treating neurological disorders, including Parkinson's disease. However, one of the major obstacles to the success of this treatment is the low survival rate of grafted cells, which probably results from mechanical damage, acute inflammation, and immunological rejection. To overcome this problem, we investigated the effect of different types of extracellular matrix (ECM) on the survival and differentiation of embryonic stem (ES) cell-derived neural precursor cells (NPCs). We tested materials from natural sources, including collagen, ornithine/laminin, and growth factor-reduced Matrigel (gfrMG), as well as the synthetic biomaterial PuraMatrix, which consists of self-assembling polypeptides. GfrMG efficiently supported cell survival, migration, and neurite outgrowth in vitro and promoted proliferation of grafted cells in vivo, resulting in larger graft volume and an increase in the number of TH-positive dopaminergic neurons in the graft. GfrMG did not induce dopaminergic differentiation directly; rather, it reduced the invasion of pan-leukocytic CD45-positive cells into the graft. Insofar as the inflammatory or immune response in the host brain inhibits neuronal differentiation of grafted NPCs, gfrMG may increase the number of TH-positive cells by suppressing this effect. Thus, gfrMG appears to provide a suitable scaffold that supports survival and differentiation of NPCs. However, because it is derived from mouse sarcomas, a human-derived matrix or synthetic biomaterial must be developed for clinical applications.

Embryonic stem cells in cardiac repair and regeneration

Cell transplantation is a subject of fast-growing research with a potential of a therapeutic approach for the treatment of heart diseases. Clinical applications require preparation of large number of donor cells. Stem cell studies published to date demonstrate that scientists have not reached the general consensus to use an optimal cell type for better cardiac repair and regeneration. We used embryonic stem (ES) cells and their released factors for cardiac repair and regeneration. The major concern of cardiac regeneration with stem cells includes engraftment, differentiation, and teratoma formation after ES cell transplantation. Our current knowledge of ES cell transplantation in the heart is very limited. This review discusses the use of various growth factors to enhance ES cells engraftment and differentiation, as well as the issue of teratoma formation.

Laminin and fibronectin scaffolds enhance neural stem cell transplantation into the injured brain

Cell transplantation offers the potential to treat central nervous system injuries, largely because multiple mechanisms can be targeted in a sustained fashion. It is crucial that cells are transplanted into an environment that is favourable for extended survival and integration within the host tissue. Given the success of using fetal tissue grafts for traumatic brain injury, it may be beneficial to mimic key aspects of these grafts (e.g. three-dimensionality, cell-cell and cell-matrix support) to deliver cells. Extracellular matrix proteins such as fibronectin and laminin are involved in neural development and may provide adhesive support for donor cells and mediate subsequent cell signalling events. In this study, neural stem cells were transplanted into the traumatically injured mouse brain within a tissue-engineered construct containing either a laminin- or fibronectin-based scaffold. Cells delivered within the scaffolds were more widely distributed in the injured brain compared to cells delivered in media alone. There were no differences in donor cell survival at 1 week post-transplant; however, by 8 weeks post-transplant, cells delivered within the scaffolds showed improved survival compared to those transplanted in media alone. Survival was more enhanced with the laminin-based scaffold compared to the fibronectin-based scaffold. Furthermore, behavioural analyses indicated that mice receiving neural stem cells within the laminin-based scaffold performed significantly better than untreated mice on a spatial learning task, supporting the notion that functional recovery correlates positively with donor cell survival. Together these results suggest that the use of appropriate extracellular matrix-based scaffolds can be exploited to improve cell transplantation therapy.