Fate of Immortalized Human Neuronal Progenitor Cells Transplanted in Rat Spinal Cord

Advances in regenerative medicine applications of tetrahedral framework nucleic acid-based nanomaterials: an expert consensus recommendation

With the emergence of DNA nanotechnology in the 1980s, self-assembled DNA nanostructures have attracted considerable attention worldwide due to their inherent biocompatibility, unsurpassed programmability, and versatile functions. Especially promising nanostructures are tetrahedral framework nucleic acids (tFNAs), first proposed by Turberfield with the use of a one-step annealing approach. Benefiting from their various merits, such as simple synthesis, high reproducibility, structural stability, cellular internalization, tissue permeability, and editable functionality, tFNAs have been widely applied in the biomedical field as three-dimensional DNA nanomaterials. Surprisingly, tFNAs exhibit positive effects on cellular biological behaviors and tissue regeneration, which may be used to treat inflammatory and degenerative diseases. According to their intended application and carrying capacity, tFNAs could carry functional nucleic acids or therapeutic molecules through extended sequences, sticky-end hybridization, intercalation, and encapsulation based on the Watson and Crick principle. Additionally, dynamic tFNAs also have potential applications in controlled and targeted therapies. This review summarized the latest progress in pure/modified/dynamic tFNAs and demonstrated their regenerative medicine applications. These applications include promoting the regeneration of the bone, cartilage, nerve, skin, vasculature, or muscle and treating diseases such as bone defects, neurological disorders, joint-related inflammatory diseases, periodontitis, and immune diseases.

Administration of C5a receptor antagonist improves the efficacy of human iPSCs-derived NS/PC transplantation in the acute phase of spinal cord injury

Human-induced pluripotent stem cell-derived neural stem/progenitor cell (hiPSC-NS/PCs) transplantation during the acute phase of spinal cord injury (SCI) is not effective due to the inflammatory response occurring immediately after SCI, which negatively impacts transplanted cell survival. Therefore, we chose to study the powerful chemoattractant complement C5a as a method to generate a more favorable transplantation environment. We hypothesized that suppression of the inflammatory response immediately after SCI by C5a receptor antagonist (C5aRA) would improve the efficacy of hiPSC-NS/PCs transplantation for acute phase SCI. Here, we evaluated the influence of C5aRA on the inflammatory reaction during the acute phase after SCI, and observed significant reductions in several inflammatory cytokines, macrophages, neutrophils and apoptotic markers. Next, we divided the SCI mice into 4 groups: i) Phosphate-buffered saline (PBS) only, ii) C5aRA only, iii) PBS + transplantation (PBS+TP), and iv) C5aRA + transplantation (C5aRA+TP). Immediately after SCI, C5aRA or PBS was injected once a day for 4 consecutive days, followed by hiPSC-NS/PC transplantation or PBS into the lesion epicenter on day 4. The C5aRA+TP group had better functional improvement as compared to the PBS only group. The C5aRA+TP group also had a significantly higher cell survival rate compared to the PBS+TP group. This study demonstrates that administration of C5aRA can suppress the inflammatory response during the acute phase of SCI, while improving the survival rate of transplanted hiPSC-NS/PCs as well as enhancing motor functional restoration. hiPSC-NS/PC transplantation with C5aRA is a promising treatment during the acute injury phase for SCI patients.

Tetrahedral DNA nanostructures facilitate neural stem cell migration via activating RHOA/ROCK2 signalling pathway

OBJECTIVES

The main purpose of current study was to explore the effects of tetrahedral DNA nanostructures (TDNs) on neuroectodermal (NE-4C) stem cells migration and unveil the potential mechanisms.

MATERIALS AND METHODS

The successfully self-assembled TDNs were also determined by dynamic light scattering (DLS). A bidirectional wound-healing assay and transwell chamber assay were employed to test the migrating behaviour of NE-4C stem cells cultured under different conditions.

RESULTS

Through an in vitro study, we found that stem cells could internalize TDNs quickly, and the cells' parallel and vertical migration was promoted effectively. Besides, the effects of TDNs were found being exerted by upregulating the gene and protein expression levels of RhoA, Rock2 and Vinculin, indicating that the RHOA/ROCK2 pathway was activated by the TDNs during the cell migration.

CONCLUSIONS

In conclusion, TDNs could enter NSCs without the aid of other transfection reagents in large amounts, whereas only small amounts of ssDNA could enter the cells. TDNs taken up by NSCs activated the RHOA/ROCK2 signalling pathway, which had effects on the relevant genes and proteins expression, eventually promoting the migration of NE-4C stem cells. These findings suggested that TDNs have great potential in application for the repair and regeneration of neural tissue.

Self-Assembled Tetrahedral DNA Nanostructures Promote Neural Stem Cell Proliferation and Neuronal Differentiation

Stem cell-based therapy is considered a promising approach for the repair of nervous tissues. Neural stem cells (NSCs) cannot proliferate or differentiate efficiently; hence, different biomaterials have been explored to improve NSC proliferation and differentiation. However, these agents either had low bioavailability or poor biocompatibility. In this work, our group investigated the effects of tetrahedral DNA nanostructures (TDNs), a novel DNA biological material, on the self-renew and differentiation of neuroectodermal (NE-4C) stem cells. We observed that TDN treatment promoted self-renew of the stem cells via activating the Wnt/β -catenin pathway. In addition, our findings suggested that NE-4C stem cells' neuronal differentiation could be promoted effectively by TDNs via inhibiting the notch signaling pathway. In summary, this is the first report about the effects of TDNs on the proliferation and differentiation of NE-4C stem cells and the results demonstrate that TDNs have a great potential in nerve tissue regeneration.

Serial in vivo imaging of transplanted allogeneic neural stem cell survival in a mouse model of amyotrophic lateral sclerosis

Neural stem cells (NSCs) are being investigated as a possible treatment for amyotrophic lateral sclerosis (ALS) through intraspinal transplantation, but no longitudinal imaging studies exist that describe the survival of engrafted cells over time. Allogeneic firefly luciferase-expressing murine NSCs (Luc⁺-NSCs) were transplanted bilaterally (100,000 cells/2μl) into the cervical spinal cord (C5) parenchyma of pre-symptomatic (63day-old) SOD1^G93A ALS mice (n=14) and wild-type age-matched littermates (n=14). Six control SOD1^G93A ALS mice were injected with saline. Mice were immunosuppressed using a combination of tacrolimus+sirolimus (1mg/kg each, i.p.) daily. Compared to saline-injected SOD1^G93A ALS control mice, a transient improvement (p<0.05) in motor performance (rotarod test) was observed after NSC transplantation only at the early disease stage (weeks 2 and 3 post-transplantation). Compared to day one post-transplantation, there was a significant decline in bioluminescent imaging (BLI) signal in SOD1^G93A ALS mice at the time of disease onset (71.7±17.9% at 4weeks post-transplantation, p<0.05), with a complete loss of BLI signal at endpoint (120day-old mice). In contrast, BLI signal intensity was observed in wild-type littermates throughout the entire study period, with only a 41.4±8.7% decline at the endpoint. In SOD1^G93A ALS mice, poor cell survival was accompanied by accumulation of mature macrophages and the presence of astrogliosis and microgliosis. We conclude that the disease progression adversely affects the survival of engrafted murine Luc⁺-NSCs in SOD1^G93A ALS mice as a result of the hostile ALS spinal cord microenvironment, further emphasizing the challenges that face successful cell therapy of ALS.

Protective Effects of Human iPS-Derived Retinal Pigmented Epithelial Cells in Comparison with Human Mesenchymal Stromal Cells and Human Neural Stem Cells on the Degenerating Retina in rd1 mice

Retinitis pigmentosa (RP) is a group of visual impairments characterized by progressive rod photoreceptor cell loss due to a genetic background. Pigment epithelium-derived factor (PEDF) predominantly secreted by the retinal pigmented epithelium (RPE) has been reported to protect photoreceptors in retinal degeneration models, including rd1. In addition, clinical trials are currently underway outside Japan using human mesenchymal stromal cells and human neural stem cells to protect photoreceptors in RP and dry age-related macular degeneration, respectively. Thus, this study aimed to investigate the rescue effects of induced pluripotent stem (iPS)-RPE cells in comparison with those types of cells used in clinical trials on photoreceptor degeneration in rd1 mice. Cells were injected into the subretinal space of immune-suppressed 2-week-old rd1 mice. The results demonstrated that human iPS-RPE cells significantly attenuated photoreceptor degeneration on postoperative days (PODs) 14 and 21 and survived longer up to at least 12 weeks after operation than the other two types of graft cells with less immune responses and apoptosis. The mean PEDF concentration in the intraocular fluid in RPE-transplanted eyes was more than 1 µg/ml at PODs 14 and 21, and this may have contributed to the protective effect of RPE transplantation. Our findings suggest that iPS-RPE cells serve as a competent source to delay photoreceptor degeneration through stable survival in degenerating ocular environment and by releasing neuroprotective factors such as PEDF.

History of Neural Stem Cell Research and Its Clinical Application

"Once development was ended…in the adult centers, the nerve paths are something fixed and immutable. Everything may die, nothing may be regenerated," wrote Santiago Ramón y Cajal, a Spanish neuroanatomist and Nobel Prize winner and the father of modern neuroscience. This statement was the central dogma in neuroscience for a long time. However, in the 1960s, neural stem cells (NSCs) were discovered. Since then, our knowledge about NSCs has continued to grow. This review focuses on our current knowledge about NSCs and their surrounding microenvironment. In addition, the clinical application of NSCs for the treatment of various central nervous system diseases is also summarized.

Impurity of stem cell graft by murine embryonic fibroblasts - implications for cell-based therapy of the central nervous system

Stem cells have been demonstrated to possess a therapeutic potential in experimental models of various central nervous system disorders, including stroke. The types of implanted cells appear to play a crucial role. Previously, groups of the stem cell network NRW implemented a feeder-based cell line within the scope of their projects, examining the implantation of stem cells after ischemic stroke and traumatic brain injury. Retrospective evaluation indicated the presence of spindle-shaped cells in several grafts implanted in injured animals, which indicated potential contamination by co-cultured feeder cells (murine embryonic fibroblasts - MEFs). Because feeder-based cell lines have been previously exposed to a justified criticism with regard to contamination by animal glycans, we aimed to evaluate the effects of stem cell/MEF co-transplantation. MEFs accounted for 5.3 ± 2.8% of all cells in the primary FACS-evaluated co-culture. Depending on the culture conditions and subsequent purification procedure, the MEF-fraction ranged from 0.9 to 9.9% of the cell suspensions in vitro. MEF survival and related formation of extracellular substances in vivo were observed after implantation into the uninjured rat brain. Impurity of the stem cell graft by MEFs interferes with translational strategies, which represents a threat to the potential recipient and may affect the graft microenvironment. The implications of these findings are critically discussed.

Potential protective effect of biphasic electrical stimulation against growth factor-deprived apoptosis on olfactory bulb neural progenitor cells through the brain-derived neurotrophic factor-phosphatidylinositol 3'-kinase/Akt pathway

Stem cell therapy may provide a therapeutic method for the replacement and regeneration of damaged neurons of the central nervous system. However, neural stem cells (NSCs) and neural precursor cells (NPCs) are especially vulnerable after transplantation due to a lack of sufficient growth factors at the transplant site. Electrical stimulation (ES) has recently been found to participate in the regulation of cell proliferation, growth, differentiation, and migration, but its underlying anti-apoptotic effects remain unclear. This study investigated the protective effects of biphasic electrical stimulation (BES) on olfactory bulb NPCs against growth factor-deprived apoptosis, examining the survival and apoptotic features of the cells. Differentiation was assessed by neuronal and glial markers. Brain-derived neurotrophic factor-phosphatidylinositol 3'-kinase (BDNF)-PI3K/Akt pathway activation was determined by enzyme-linked immunosorbent assay and Western blot. The chemical inhibitor wortmannin was used to inhibit the PI3K/Akt pathway. BES exerts a protective effect against growth factor-deprived apoptosis in the NPCs. BES enhanced cell survival and decreased the apoptotic/necrotic rate. Expression of phosphorylated Akt and BDNF secretion increased with BES for 12 h. Furthermore, the protective effects of BES were inhibited by blocking PI3K/AKT signalling. These results suggest that BES prevents growth factor-deprived apoptosis through the BDNF-PI3K/Akt signalling. This work strengthens the opinion that BES may be used as an auxiliary strategy for improving cell survival and preventing cell apoptosis in stem cell-based transplantation therapy.

Ferumoxytol: a new, clinically applicable label for stem-cell tracking in arthritic joints with MRI

AIM

To develop a clinically applicable MRI technique for tracking stem cells in matrix-associated stem-cell implants, using the US FDA-approved iron supplement ferumoxytol.

MATERIALS & METHODS

Ferumoxytol-labeling of adipose-derived stem cells (ADSCs) was optimized in vitro. A total of 11 rats with osteochondral defects of both femurs were implanted with ferumoxytol- or ferumoxides-labeled or unlabeled ADSCs, and underwent MRI up to 4 weeks post matrix-associated stem-cell implant. The signal-to-noise ratio of different matrix-associated stem-cell implant was compared with t-tests and correlated with histopathology.

RESULTS

An incubation concentration of 500 µg iron/ml ferumoxytol and 10 µg/ml protamine sulfate led to significant cellular iron uptake, T2 signal effects and unimpaired ADSC viability. In vivo, ferumoxytol- and ferumoxides-labeled ADSCs demonstrated significantly lower signal-to-noise ratio values compared with unlabeled controls (p < 0.01). Histopathology confirmed engraftment of labeled ADSCs, with slow dilution of the iron label over time.

CONCLUSION

Ferumoxytol can be used for in vivo tracking of stem cells with MRI.

Neural stem cell-based treatment for neurodegenerative diseases

Human neurodegenerative diseases such as Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) are caused by a loss of neurons and glia in the brain or spinal cord. Neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells (ESCs), mesenchymal stem cells (MSCs) and neural stem cells (NSCs), and stem cell-based cell therapies for neurodegenerative diseases have been developed. A recent advance in generation of a new class of pluripotent stem cells, induced pluripotent stem cells (iPSCs), derived from patients' own skin fibroblasts, opens doors for a totally new field of personalized medicine. Transplantation of NSCs, neurons or glia generated from stem cells in animal models of neurodegenerative diseases, including PD, HD, ALS and AD, demonstrates clinical improvement and also life extension of these animals. Additional therapeutic benefits in these animals can be provided by stem cell-mediated gene transfer of therapeutic genes such as neurotrophic factors and enzymes. Although further research is still needed, cell and gene therapy based on stem cells, particularly using neurons and glia derived from iPSCs, ESCs or NSCs, will become a routine treatment for patients suffering from neurodegenerative diseases and also stroke and spinal cord injury.

Olfactory ensheathing cell neurorestorotherapy for amyotrophic lateral sclerosis patients: benefits from multiple transplantations

Our previous series of studies have proven that olfactory ensheathing cell (OEC) transplantation appears to be able to slow the rate of clinical progression after OEC transplantation in the first 4 months and cell intracranial (key points for neural network restoration, KPNNR) and/or intraspinal (impaired segments) implants provide benefit for patients (including both the bulbar onset and limb onset subtypes) with amyotrophic lateral sclerosis (ALS). Here we report the results of cell therapy in patients with ALS on the basis of long-term observation following multiple transplants. From March of 2003 to January of 2010, 507 ALS patients received our cellular treatment. Among them, 42 patients underwent further OEC therapy by the route of KPNNR for two or more times (two times in 35 patients, three times in 5 patients, four times in 1 patient, and five times in 1 patient). The time intervals are 13.1 (6-60) months between the first therapy and the second one, 15.2 (8-24) months between the second therapy and the third one, 16 (6-26) months between the third therapy and the fourth one, and 9 months between the fourth therapy and the fifth time. All of the patients exhibited partial neurological functional recovery after each cell-based administration. Firstly, the scores of the ALS Functional Rating Scale (ALS-FRS) and ALS Norris Scale increased by 2.6 + 2.4 (0-8) and 4.9 + 5.2 (0-20) after the first treatment, 1.1 + 1.3 (0-5) and 2.3 + 2.9 (0-13) after the second treatment, 1.1 + 1.5 (0-4), and 3.4 + 6.9 (0-19) after the third treatment, 0.0 + 0.0 (0-0), and 2.5 + 3.5 (0-5) after the fourth treatment, and 1 point after the fifth cellular therapy, which were evaluated by independent neurologists. Secondly, the majority of patients have achieved improvement in electromyogram (EMG) assessments after the first, second, third, and fourth cell transplantation. After the first treatment, among the 42 patients, 36 (85.7%) patients' EMG test results improved, the remaining 6 (14.3%) patients' EMG results showed no remarkable change. After the second treatment, of the 42 patients, 30 (71.4%) patients' EMG results improved, 11 (26.2%) patients showed no remarkable change, and 1 (2.4%) patient became worse. After the third treatment, out of the 7 patients, 4 (57.1%) patients improved, while the remaining 3 (42.9%) patients showed no change. Thirdly, the patients have partially recovered their breathing ability as demonstrated by pulmonary functional tests. After the first treatment, 20 (47.6%) patients' pulmonary function ameliorated. After the second treatment, 18 (42.9%) patients' pulmonary function improved. After the third treatment, 2 (28.6%) patients recovered some pulmonary function. After the fourth and fifth treatment, patients' pulmonary function did not reveal significant change. The results show that multiple doses of cellular therapy definitely serve as a positive role in the treatment of ALS. This repeated and periodic cell-based therapy is strongly recommended for the patients, for better controlling this progressive deterioration disorder.

[Stem cell-based treatment of neurologic diseases]

Therapeutic strategies based on stem cells are being increasingly used to treat a wide range of neurological diseases. Although these strategies were initially designed to replace dead cells in injured tissue, the potential of stem cells to migrate, secrete trophic factors, and immunomodulate allows their therapeutic use as a vehicle for gene therapy, as in Parkinson's disease, or as immunomodulators and neuroprotectors in diseases such as multiple sclerosis. This review will focus on current clinical and experimental evidence on the treatment of neurological disorders with strategies based on stem cells.

Stem cell-based cell therapy in neurological diseases: a review

Human neurological disorders such as Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis (ALS), Alzheimer's disease, multiple sclerosis (MS), stroke, and spinal cord injury are caused by a loss of neurons and glial cells in the brain or spinal cord. Cell replacement therapy and gene transfer to the diseased or injured brain have provided the basis for the development of potentially powerful new therapeutic strategies for a broad spectrum of human neurological diseases. However, the paucity of suitable cell types for cell replacement therapy in patients suffering from neurological disorders has hampered the development of this promising therapeutic approach. In recent years, neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells, mesenchymal stem cells, and neural stem cells, and extensive efforts by investigators to develop stem cell-based brain transplantation therapies have been carried out. We review here notable experimental and preclinical studies previously published involving stem cell-based cell and gene therapies for Parkinson's disease, Huntington's disease, ALS, Alzheimer's disease, MS, stroke, spinal cord injury, brain tumor, and lysosomal storage diseases and discuss the future prospects for stem cell therapy of neurological disorders in the clinical setting. There are still many obstacles to be overcome before clinical application of cell therapy in neurological disease patients is adopted: 1) it is still uncertain what kind of stem cells would be an ideal source for cellular grafts, and 2) the mechanism by which transplantation of stem cells leads to an enhanced functional recovery and structural reorganization must to be better understood. Steady and solid progress in stem cell research in both basic and preclinical settings should support the hope for development of stem cell-based cell therapies for neurological diseases.

Intrathecal transplantation of human neural stem cells overexpressing VEGF provide behavioral improvement, disease onset delay and survival extension in transgenic ALS mice

Amyotrophic lateral sclerosis (ALS) is the most common adult onset motoneuron disease. The etiology and precise pathogenic mechanisms of the disease remain unknown, and there is no effective treatment. Vascular endothelial growth factor (VEGF) has recently been shown to exert direct neurotrophic and neuroprotective effects in animal models of ALS. Here we show that intrathecal transplantation of immortalized human neural stem cells (NSCs) overexpressing human VEGF gene (HB1.F3.VEGF) significantly delayed disease onset and prolonged the survival of the SOD1G93A mouse model of ALS. At 4 weeks, post-transplantation grafted cells were found within the gray matter of the spinal cord. Furthermore, transplanted F3.VEGF cells that express neuronal phenotype (MAP2+) were found in the anterior horn of the spinal cord gray matter indicating that the transplanted human NSCs migrated into the gray matter, took the correct structural position, integrated into the spinal cord anterior horn and differentiated into motoneurons. Intrathecal transplantation of F3.VEGF cells provides a neuroprotective effect in the diseased spinal cord by concomitant downregulation of proapoptotic proteins and upregulation of antiapoptotic proteins. Our results suggest that this treatment modality of intrathecal transplantation of human NSCs genetically modified to overexpress neurotrophic factor(s) might be of value in the treatment of ALS patients without significant adverse effects.

Transplanted human embryonic neural stem cells survive, migrate, differentiate and increase endogenous nestin expression in adult rat cortical peri-infarction zone

Transplantation of stem cells is a potential therapeutic strategy for stroke damage. The survival, migration, and differentiation of transplanted human embryonic neural stem cells in the acute post-ischemic environment were characterized and endogenous nestin expression after transplantation was investigated. Human embryonic neural stem cells obtained from the temporal lobe cortex were cultured and labeled with fluorescent 1,1'-dioctadecy-6,6'-di (4-sulfopheyl)-3,3,3',3'-tetramethylindocarbocyanin (DiI) in vitro. Labeled cells were transplanted into cortical peri-infarction zones of adult rats 24 h after permanent middle cerebral artery occlusion. Survival, migration, and differentiation of grafted cells were quantified in immunofluorescence-stained sections from rats sacrificed at 7, 14, and 28 days after transplantation. Endogenous nestin-positive cells in the cortical peri-infarction zone were counted at serial time points. The cells transplanted into the cortical peri-infarction zone displayed the morphology of living cells and became widely located around the ischemic area. Moreover, some of the transplanted cells expressed nestin, GFAP, or NeuN in the peri-infarction zone. Furthermore, compared with the control group, endogenous nestin-positive cells in the peri-infarction zone had increased significantly 7 days after cell transplantation. These results confirm the survival, migration, and differentiation of transplanted cells in the acute post-ischemic environment and enhanced endogenous nestin expression within a brief time window. These findings indicate that transplantation of neural stem cells into the peri-infarction zone may be performed as early as 24 h after ischemia.

Class III beta-tubulin is constitutively coexpressed with glial fibrillary acidic protein and nestin in midgestational human fetal astrocytes: implications for phenotypic identity

Class III beta-tubulin isotype (betaIII-tubulin) is widely regarded as a neuronal marker in developmental neurobiology and stem cell research. To test the specificity of this marker protein, we determined its expression and distribution in primary cultures of glial fibrillary acidic protein (GFAP)-expressing astrocytes isolated from the cerebral hemispheres of 2 human fetuses at 18 to 20 weeks of gestation. Cells were maintained as monolayer cultures for 1 to 21 days without differentiation induction. By immunofluorescence microscopy, coexpression of betaIII-tubulin and GFAP was detected in cells at all time points but in spatially distinct patterns. The numbers of GFAP+ cells gradually decreased from Days 1 to 21 in vitro, whereas betaIII-tubulin immunoreactivity was present in 100% of cells at all time points. beta-III-tubulin mRNA and protein expression were demonstrated in cultured cells by reverse-transcriptase-polymerase chain reaction and immunoblotting, respectively. Glial fibrillary acidic protein+/beta-III-tubulin-positive cells coexpressed nestin and vimentin but lacked neurofilament proteins, CD133, and glutamate-aspartate transporter. Weak cytoplasmic staining was detected with antibodies against microtubule-associated protein 2 isoforms. Confocal microscopy, performed on autopsy brain samples of human fetuses at 16 to 20 gestational weeks, revealed widespread colocalization of GFAP and betaIII-tubulin in cells of the ventricular/subventricular zones and the cortical plate. Our results indicate that in the midgestational human brain, betaIII-tubulin is not neuron specific because it is constitutively expressed in GFAP+/nestin+ presumptive fetal astrocytes.

Harvested human neurons engineered as live nervous tissue constructs: implications for transplantation. Laboratory investigation

OBJECT

Although neuron transplantation to repair the nervous system has shown promise in animal models, there are few practical sources of viable neurons for clinical application and insufficient approaches to bridge extensive nerve damage in patients. Therefore, the authors sought a clinically relevant source of neurons that could be engineered into transplantable nervous tissue constructs. The authors chose to evaluate human dorsal root ganglion (DRG) neurons due to their robustness in culture.

METHODS

Cervical DRGs were harvested from 16 live patients following elective ganglionectomies, and thoracic DRGs were harvested from 4 organ donor patients. Following harvest, the DRGs were digested in a dispase-collagenase treatment to dissociate neurons for culture. In addition, dissociated human DRG neurons were placed in a specially designed axon expansion chamber that induces continuous mechanical tension on axon fascicles spanning 2 populations of neurons originally plated approximately 100 microm apart.

RESULTS

The adult human DRG neurons, positively identified by neuronal markers, survived at least 3 months in culture while maintaining the ability to generate action potentials. Stretch-growth of axon fascicles in the expansion chamber occurred at the rate of 1 mm/day to a length of 1 cm, creating the first engineered living human nervous tissue constructs.

CONCLUSIONS

These data demonstrate the promise of adult human DRG neurons as an alternative transplant material due to their availability, viability, and capacity to be engineered. Also, these data show the feasibility of harvesting DRGs from living patients as a source of neurons for autologous transplant as well as from organ donors to serve as an allograft source of neurons.

Labeling stem cells in vitro for identification of their differentiated phenotypes after grafting into the CNS

Grafting neural stem cells is a widely used experimental approach to central nervous system (CNS) repair after trauma or neurodegeneration. It is likely to be a realistic clinical therapy for human CNS disorders in the near future. One of the challenges of this approach is the ability to identify both the survival and differentiated phenotype of various stem cell populations after engraftment into the CNS. There is no single protocol that will work for all cell types and all applications. Labeling stem cells for CNS grafting is an empirical process. The type of stem cell, its fate after engraftment, and the context in which it is anatomically and histologically evaluated all contribute to a decision as to the best approach to take. We have provided the range of conditions under which various labels have been successfully used in CNS grafting studies and delineated the parameters that have to be empirically established. Given a clear understanding of the limitations of the respective labels and the expected outcome of the grafting experiment, these labeling guidelines should enable any investigator to develop a successful approach. Our own personal bias is to use labels that cannot be transferred to host cells. Initially, we preferred 5-bromo-2'-deoxyuridine, or retrovirally delivered enhanced green fluorescent protein or lacZ. More recently, we have found syngeneic grafts of human placental alkaline phosphatase stem cells to work very well. However, each investigator will have to decide what is optimal for his or her cell population and experimental design. We summarize the various approaches to labeling and identifying stem cells, pointing out both the limitations and strengths of the various approaches delineated.

Murine brain progenitor cells have the ability to differentiate into functional neurons and integrate into the CNS

Although neural stem and progenitor cells have been shown to differentiate into neurons, few studies have examined the physiological properties of the differentiated neurons derived from stem cells. Here we show that mouse brain progenitor cells (mBPCs) differentiated in culture by removal of mitogenic factors or addition of BDNF or GDNF express neuronal-specific proteins including MAP-2 and synaptobrevin II. However, these cells demonstrate small voltage-gated Na+ currents and are not able to generate action potentials. When the mBPCs are cocultured with developing rat hippocampal neurons, the stem cells differentiate into neurons expressing MAP-2, develop large voltage-gated Na+ currents, and are able to generate action potentials. To investigate the influence of a mature CNS environment on survival, differentiation, migration, and morphological integration, mBPCs were transplanted into the spinal cord of adult mice. Undifferentiated cells transplanted into the spinal cord exhibited limited migration and expressed NG2, but did not differentiate to express MAP-2. Predifferentiated cells migrated to both gray and white matter with about 23% cells developing MAP-2 immunoreactivity after 8 weeks. These results suggest that both the environment and state of differentiation may dictate migration and the differentiation pathway of stem cells after transplantation.

Trauma-associated inflammatory response impairs embryonic stem cell survival and integration after implantation into injured rat brain

Pluripotent embryonic stem cells were shown to survive and differentiate into mature neuronal cells after implantation in experimental models of Parkinson disease and cerebral ischemia. Embryonic stem cell transplantation has also been proposed as a potential therapy for cerebral trauma, characteristic of massive loss of multiple cell types due to primary insult and secondary sequelae. Green fluorescent protein (GFP)-transfected murine embryonic stem cells were implanted into the ipsi or contralateral cortex of male Sprague-Dawley rats 72 h after fluid-percussion injury. Animals were sacrificed at day 5 or week 7 postimplantation. Brain sections were examined using conventional and fluorescent double-labelling immunohistochemistry. Five days after implantation, clusters of GFP-positive cells undergoing partial differentiation along neuronal pathway, were detected at the implantation site. However, after 7 weeks, only a few GFP-positive cells were found, indicating an extensive loss of stem cells during this time period. For the first time, we proved the observed cell loss to be mediated via phagocytosis of implanted cells by activated macrophages. Cerebral trauma, induced 3 days prior to implantation, has activated the inflammatory potential of otherwise immunologically privileged tissue. Subsequent cell implantation was accompanied by reactive astrogliosis, activation of microglia, as well as a massive invasion of macrophages into transplantation sites even if the grafts were placed into contralateral healthy hemispheres, remote from the traumatic lesion. Our results demonstrate a significant post-traumatic inflammatory response, which impairs survival and integration of implanted stem cells and has generally not been taken into account in designs of previous transplantation studies.

Localization of bone marrow stromal cells in injured spinal cord treated by intravenous route depends on the hemorrhagic lesions in traumatized spinal tissues

OBJECTIVES

Bone marrow stromal cells (BMSCs) have been reported to improve movement deficit in adult rats with spinal cord injury (SCI). The purpose of this study is to determine the distribution of BMSCs in the spinal cord lesion of the contusion model of SCI.

METHODS

Laminectomy was carried out at L1 vertebra level and SCI was carried out using the weight drop method. BMSCs were isolated from adult rats, labeled with bromodeoxyuridine (BrdU) and administered intravenously to the rats 1 week after SCI, which were killed after 4 weeks. The non-treated animals were used as negative control, which showed cavitations of the spinal cord after 5 weeks of SCI. Rats in another group were killed immediately and used to study the hemorrhagic lesions. The volume densities (Vv) of the hemorrhage and cavitation were the highest at the site of direct trauma.

RESULTS

The numerical densities of the transmigrated cells per area (Nat) were as follows: 0.3 +/- 0.2, 3.9 +/- 0.4, 5.4 +/- 0.4, 8.4 +/- 0.5, 5.5 +/- 0.3, 3.6 +/- 0.3 and 0.4 +/- 0.2 at the end and the middle of the thoracic vertebra 13 (T13), the region between T13 and the first lumbar vertebra, the middle of L1, the region between L1 and L2, and the middle and the end of L2 vertebra, respectively. The distribution of Nat at the above regions was a Gaussian model. The volume densities of hemorrhage in the spinal cord taken from the above regions showed that hemorrhage with the highest volume density occurred at the impact site and the volume density declined as the samples taken were more distant from the impact site.

DISCUSSION

The migration of BMSCs in the injured region depends on the amount of the hemorrhage and damage to blood vessels of the spinal cord.

Combined immunosuppressive agents or CD4 antibodies prolong survival of human neural stem cell grafts and improve disease outcomes in amyotrophic lateral sclerosis transgenic mice

Amyotrophic lateral sclerosis (ALS) is a target for cell-replacement therapies, including therapies based on human neural stem cells (NSCs). These therapies must be first tested in the appropriate animal models, including transgenic rodents harboring superoxide dismutase (SOD1) mutations linked to familial ALS. However, these rodent subjects reject discordant xenografts. In the present investigation, we grafted NSCs from human embryonic spinal cord into the ventral lumbar cord of 2-month-old SOD1-G93A transgenic mice. Animals were immunosuppressed with FK506, FK506 plus rapamycin, FK506 plus rapamycin plus mycophenolate mofetil, or CD4 antibodies. With FK506 monotherapy, human NSC grafts were rejected within 1 week, whereas combinations of FK506 with one or two of the other agents or CD4 antibodies protected grafts into end-stage illness (i.e., more than 2 months after grafting). The combination of FK506 with rapamycin appeared to be optimal with respect to efficacy and simplicity of administration. Graft protection was achieved via the blockade of CD4- and CD8-cell infiltration and attenuation of the microglial phagocytic response from the host. Surviving NSCs differentiated extensively into neurons that began to establish networks with host nerve cells, including alpha-motor neurons. Immunosuppressed animals with live cells showed later onset and a slower progression of motor neuron disease and lived longer compared with immunosuppressed control animals with dead NSC grafts. Our findings indicate that combined immunosuppression promotes the survival of human NSCs grafted in the spinal cord of SOD1-G93A mice and, in doing so, allows the differentiation of NSCs into neurons and leads to the improvement of key parameters of motor neuron disease.