Induced neural stem cells from Macaca fascicularis show potential of dopaminergic neuron specification and efficacy in a mouse Parkinson's disease model.

Induced neural stem cells (iNSCs) can be reprogrammed from somatic cells and have shown potentials in treatment of various neurological diseases/disorders. Obtaining iNSCs of nonhuman primates serves as an important bridge for clinical translation using iNSCs. In the current study, cynomolgus (Macaca fascicularis) bone marrow mesenchymal stromal cells (MSCs) were reprogrammed into iNSCs by transduction of non-integrative Sendai virus encoding transgenes OCT4, SOX2, KLF4 and C-MYC. The obtained iNSCs showed characteristics of normal neural stem cells (NSCs) and could differentiate into neurons, astrocytes and oligodendrocytes. Furthermore, iNSCs could give rise to dopaminergic neural cells in vitro, which showed safety and efficacy after transplantation into the striatum of an immunodeficient mouse Parkinson's disease (PD) model.

Characterization of Human-Induced Neural Stem Cells and Derivatives following Transplantation into the Central Nervous System of a Nonhuman Primate and Rats.

Neural stem cells (NSCs) and derivatives are potential cellular sources to treat neurological diseases. In the current study, we reprogrammed human peripheral blood mononuclear cells into induced NSCs (iNSCs) and inserted GFP gene into the AAVS1 site for graft tracing. Targeted integration of GFP does not affect the proliferation and differentiation capacity of iNSCs. iNSC-GFP can be further differentiated into dopaminergic precursors (DAPs) and motor neuron precursors (MNPs), respectively. iNSCs were engrafted into the motor cortex and iNSC-DAPs into the striatum and substantia nigra (SN) of a nonhuman primate, respectively. The surviving iNSCs could respond to the microenvironment of the cortex and spontaneously differentiate into mature neurons that extended neurites. iNSC-DAPs survived well and matured into DA neurons following transplantation into the striatum and SN. iNSC-MNPs could also survive and turn into motor neurons after being engrafted into the spinal cord of rats. The results suggest that iNSCs and derivatives have a potential to be used for the treatment of neurological diseases.

TNFα-induced Up-regulation of Ascl2 Affects the Differentiation and Proliferation of Neural Stem Cells.

The molecular mediators underlying the effects of inflammation on neural stem cells (NSCs) are not fully characterized. In this study, we identified Ascl2 as a downstream basic helix-loop-helix (bHLH) transcription factor in NSCs following exposure to TNFα. Under normal conditions, Ascl2 expression is inhibited at post-transcriptional levels by miR-26a, which targets the 3' untranslated region (UTR) of Ascl2. Upon exposure to TNFα, miR-26a expression is reduced, which leads to up-regulation of Ascl2. Overexpression of Ascl2 promotes neuronal differentiation, reduces proliferation, and increases the level of cleaved CASPASE 3 in NSCs, as observed in the in vitro and in ovo experiments. Ascl2 may serve in NSCs as a standby factor that readily responds to TNFα, which is often induced in inflammatory situations. In a chronic inflammatory condition with consistent up-regulation of TNFα, overexpression of Ascl2 may inhibit neurogenesis as a net result.

Dopaminergic precursors differentiated from human blood-derived induced neural stem cells improve symptoms of a mouse Parkinson's disease model.

Autologous neural stem cells (NSCs) may offer a promising source for deriving dopaminergic (DA) cells for treatment of Parkinson's disease (PD). Methods: By using Sendai virus, human peripheral blood mononuclear cells (PBMNCs) were reprogrammed to induced NSCs (iNSCs), which were then differentiated to dopaminergic neurons in vitro. Whole-genome deep sequencing was performed to search for mutations that had accumulated during the reprogramming and expansion processes. To find the optimal differentiation stage of cells for transplantation, DA precursors obtained at various differentiation time points were tested by engraftment into brains of naïve immunodeficient mice. At last, the safety and efficacy of iNSC-derived DA precursors were tested by transplantation into the striatum of immunodeficient PD mouse models. Results: PBMNC-derived iNSCs showed similar characteristics to fetal NSCs, and were able to specifically differentiate to DA neurons with high efficiency in vitro. The sequencing data proved that no harmful SNVs, Indels and CNVs were generated during the reprogramming and expansion processes. DA precursors obtained between differentiation day 10 to 13 in vitro were most suitable for transplantation when a balanced graft survival and maturation were taken into account. Two weeks after transplantation of DA precursors into mouse PD models, the motor functions of PD mice started to improve, and continued to improve until the end of the experiments. No graft overgrowth or tumor was observed, and a significant number of A9-specific midbrain DA neurons were surviving in the striatum. Conclusion: This study confirmed the efficacy of iNSC-derived DA precursors in a mouse PD model, and emphasized the necessity of genomic sequencing and vigorous safety assessment before any clinical translation using iNSCs.

Ectopic hTERT expression facilitates reprograming of fibroblasts derived from patients with Werner syndrome as a WS cellular model.

The induced pluripotent stem cell (iPSC) technology has provided a unique opportunity to develop disease-specific models and personalized treatment for genetic disorders, and is well suitable for the study of Werner syndrome (WS), an autosomal recessive disease with adult onset of premature aging caused by mutations in the RecQ like helicase (WRN) gene. WS-derived fibroblasts were previously shown to be able to generate iPSCs; however, it remains elusive how WS-derived iPSCs behave and whether they are able to mimic the disease-specific phenotype. The present study was designed to address these issues. Unexpectedly, we found that a specific WS fibroblast line of homozygous truncation mutation was difficult to be reprogrammed by using the Yamanaka factors even under hypoxic conditions due to their defect in induction of hTERT, the catalytic unit of telomerase. Ectopic expression of hTERT restores the ability of this WS fibroblast line to form iPSCs, although with a low efficiency. To examine the phenotype of WRN-deficient pluripotent stem cells, we also generated WRN knockout human embryonic stem (ES) cells by using the CRISPR/Cas9 method. The iPSCs derived from WS-hTERT cells and WRN-/- ESCs are fully pluripotent, express pluripotent markers and can differentiate into three germ layer cells; however, WS-iPSCs and WRN-/- ESCs show S phase defect in cell cycle progression. Moreover, WS-iPSCs and WRN-/- ESCs, like WS patient-derived fibroblasts, remain hypersensitive to topoisomerase inhibitors. Collectively, WS-derived iPSCs and WRN-/- ESCs mimic the intrinsic disease phenotype, which may serve as a suitable disease model, whereas not be good for a therapeutic purpose without gene correction.

Intravenously Delivered Allogeneic Mesenchymal Stem Cells Bidirectionally Regulate Inflammation and Induce Neurotrophic Effects in Distal Middle Cerebral Artery Occlusion Rats Within the First 7 Days After Stroke.

BACKGROUND/AIMS: Neurotrophic effects and immunosuppression are the main therapeutic mechanisms of mesenchymal stem cells (MSCs) in stroke treatment. Neurotrophins are produced by graft cells, host neurons, astrocytes, and even microglia/macrophages. Meanwhile, MSCs can increase inflammation if they are not sufficiently induced by pro-inflammatory cytokines. We examined whether intravenously transplanted bone marrow MSCs (BM-MSCs) increase inflammation in distal middle cerebral artery occlusion (dMCAO) rats, how long the increased inflammation effect persists for, and what the final therapeutic outcomes will be. We also tested the neurotrophic role of BM-MSCs and attempted to identify the neurotrophin-producing cells. METHODS: At 1 h after dMCAO was performed on Sprague-Dawley rats, allogeneic BM-MSCs were transplanted intravenously. The infarct volume was examined by Tetrazolium Red staining at 2 days (day 2), and the behavioral tests (cylinder test and grid walking test) were performed at 2, 4 (day 4) and 7 days (day 7) after transplantation. The concentrations of inflammation related cytokines and neurotrophins in the ischemic cortex, ipsilateral striatum, and serum, were measured using ELISA at days 2-7. The cell source of neurotrophins was observed by immunohistochemistry. RESULTS: The transplanted cells were mainly found in the infarct border zone (IBZ) of the brain. Infarct volume was reduced and behavioral outcomes were improved at 2 days after ischemia. In the striatum and circulation, BM-MSC transplantation increased inflammation at day 2 and decreased it at day 7. At days 2-7, insulin-like growth factor-1 (IGF-1) and brain-derived neurotrophic factor (BDNF) concentrations in the ischemic core of the cortex were significantly higher in the BM-MSC group than in the ischemia vehicle group. IGF-1 and BDNF were derived mainly from host microglia/macrophages in the ischemic core, and transplanted cells in the IBZ. At day 2, BM-MSC transplantation significantly increased the number of IGF-1+CD68+ and BDNF+Iba-1+ double positive cells in the ischemic core cortex. CONCLUSIONS: Although increased inflammation, BM-MSCs were still beneficial to dMCAO recovery at day 2. The immunopromoting effect of MSCs was transient and shifted to an immunosuppressive action at day 7. The neurotrophic factors IGF-1 and BDNF, which were mainly derived from transplanted BM-MSCs and host microglia/macrophages, contributed to the therapeutic effects from day 2 to day 7.

Accelerated generation of oligodendrocyte progenitor cells from human induced pluripotent stem cells by forced expression of Sox10 and Olig2.

Oligodendrocyte progenitor cells (OPCs) hold great promise for treatment of dysmyelinating disorders, such as multiple sclerosis and cerebral palsy. Recent studies on generation of human OPCs mainly use human embryonic stem cells (hESCs) or neural stem cells (NSCs) as starter cell sources for the differentiation process. However, NSCs are restricted in availability and the present method for generation of oligodendrocytes (OLs) from ESCs often requires a lengthy period of time. Here, we demonstrated a protocol to efficiently derive OPCs from human induced pluripotent stem cells (hiPSCs) by forced expression of two transcription factors (2TFs), Sox10 and Olig2. With this method, PDGFRα+ OPCs can be obtained in 14 days and O4+ OPCs in 56 days. Furthermore, OPCs may be able to differentiate to mature OLs that could ensheath axons when co-cultured with rat cortical neurons. The results have implications in the development of autologous cell therapies.

Multiparameter Characterization Confirms Apoptosis as the Primary Cause of Reduced Self-renewal Capacity in Cultured Human Fetal Neural Stem Cells.

BACKGROUND: Human fetal striatum-derived neural stem cells (hfsNSCs) are important in regenerative medicine; however, their ability to self-renew diminishes quickly following passages in culture. Typically when hfsNSC-derived neurospheres are dissociated by accutase, more than 90% of the cells survive, but only 6-8% of the cells are able to form secondary neurospheres. Our hypothesis is that the hfsNSCs that are unable to form new neurospheres become apoptotic. METHODS/RESULTS: Because the NSC apoptosis process has never been characterized in detail, we characterized hfsNSC apoptosis using multiparameter analysis and determined that the majority of hfsNSCs undergo apoptosis after passaging, which leads to a reduction in self-renewal. The replacement of trituration with vortexing decreases apoptosis, increases self-renewal, and does not affect NSC differentiation. When we used live cell staining with Annexin V, Hoechst 33342, and PI together, the apoptotic index was in agreement with what could be obtained using fixed-cell staining methods, including TUNEL and activated caspase-3 immunocytochemistry. NSC apoptosis could be divided into 9 stage types based on our live cell assay. Several types during early and late stages had similar staining profiles that could be further discriminated based on cell size. CONCLUSION: Apoptosis largely contributes to the low self-renewal of neurospheres, and replacing trituration with vortexing aided in alleviating NSC apoptosis. Multiparameter analysis is required for the identification of NSC apoptosis, particularly when live cell staining is used.

Differentiation of human induced pluripotent stem cells to mature functional Purkinje neurons.

It remains a challenge to differentiate human induced pluripotent stem cells (iPSCs) or embryonic stem (ES) cells to Purkinje cells. In this study, we derived iPSCs from human fibroblasts and directed the specification of iPSCs first to Purkinje progenitors, by adding Fgf2 and insulin to the embryoid bodies (EBs) in a time-sensitive manner, which activates the endogenous production of Wnt1 and Fgf8 from EBs that further patterned the cells towards a midbrain-hindbrain-boundary tissue identity. Neph3-positive human Purkinje progenitors were sorted out by using flow cytometry and cultured either alone or with granule cell precursors, in a 2-dimensional or 3-dimensional environment. However, Purkinje progenitors failed to mature further under above conditions. By co-culturing human Purkinje progenitors with rat cerebellar slices, we observed mature Purkinje-like cells with right morphology and marker expression patterns, which yet showed no appropriate membrane properties. Co-culture with human fetal cerebellar slices drove the progenitors to not only morphologically correct but also electrophysiologically functional Purkinje neurons. Neph3-posotive human cells could also survive transplantation into the cerebellum of newborn immunodeficient mice and differentiate to L7- and Calbindin-positive neurons. Obtaining mature human Purkinje cells in vitro has significant implications in studying the mechanisms of spinocerebellar ataxias and other cerebellar diseases.

Autologous iPSC-derived dopamine neuron transplantation in a nonhuman primate Parkinson's disease model.

Autologous dopamine (DA) neurons are a new cell source for replacement therapy of Parkinson's disease (PD). In this study, we tested the safety and efficacy of autologous induced pluripotent stem cell (iPSC)-derived DA cells for treatment of a cynomolgus monkey PD model. Monkey bone marrow mesenchymal cells were isolated and induced to iPSCs, followed by differentiation into DA cells using a method with high efficiency. Autologous DA cells were introduced into the brain of a cynomolgus monkey PD model without immunosuppression; three PD monkeys that had received no grafts served as controls. The PD monkey that had received autologous grafts experienced behavioral improvement compared with that of controls. Histological analysis revealed no overgrowth of grafts and a significant number of surviving A9 region-specific graft-derived DA neurons. The study provided a proof-of-principle to employ iPSC-derived autologous DA cells for PD treatment using a nonhuman primate PD model.

Lmx1a enhances the effect of iNSCs in a PD model.

Lmx1a plays a central role in the specification of dopaminergic (DA) neurons, which potentially could be employed as a key factor for trans-differentiation to DA neurons. In our previous study, we have converted somatic cells directly into neural stem cell-like cells, namely induced neural stem cells (iNSCs), which further can be differentiated into subtypes of neurons and glia in vitro. In the present study, we continued to test whether these iNSCs have therapeutic effects when transplanted into a mouse model of Parkinson's disease (PD), especially when Lmx1a was introduced into these iNSCs under a Nestin enhancer. iNSCs that over-expressed Lmx1a (iNSC-Lmx1a) gave rise to an increased yield of dopaminergic neurons and secreted a higher level of dopamine in vitro. When transplanted into mouse models of PD, both groups of mice showed decreased ipsilateral rotations; yet mice that received iNSC-Lmx1a vs. iNSC-GFP exhibited better recovery. Although few iNSCs survived 11weeks after transplantation, the improved motor performance in iNSC-Lmx1a group did correlate with a greater tyrosine hydroxylase (TH) signal abundance in the lesioned area of striatum, suggesting that iNSCs may have worked through a non-autonomous manner to enhance the functions of remaining endogenous dopaminergic neurons in brain.

Ischemia, immunosuppression, and SSEA-1-negative cells all contribute to tumors resulting from mouse embryonic stem cell-derived neural progenitor transplantation.

Neural progenitor cells (NPCs) derived from mouse embryonic stem (mES) cells can lead to tumors after transplantation. The cellular source of such tumors remains under debate. We investigated the tumor formation resulting from mES cell-derived NPCs in a rat stroke model and in nude mice. After 2 hr of ischemia and 48 hr of reperfusion, the NPCs were transplanted into the ischemic core of the xenogeneic rats. Four weeks after transplantation, the grafted cells were found to be viable at the border of the necrosis and had differentiated into neurons. Transplanted rats did not exhibit any behavioral improvement, because tumor formed in 90% of the animals. Immunosuppression facilitated tumor formation. Tumors were observed in 40% of normal rats after NPC transplantation when cyclosporin A was administered. Meanwhile, no tumor formation was observed without cyclosporin A. Ischemic damage also facilitated tumor formation, because NPCs gave rise to tumors in 90% of ischemic rats, a percentage significantly higher than that in intact rats, which was 40%. The SSEA-1-positive cells isolated from stage 4 are not exactly undifferentiated ES cells. They exhibited a marker gene transcription profile different from that of ES cells and did not form tumors in transplanted nude mice. The undifferentiated ES cells remaining after differentiation did not contribute to tumors either. First, the tumor formation rate resulting from undifferentiated ES cells in the brains of normal rats is 0%, significantly lower than that of NPCs. Second, transplanted NPCs that led to 100% tumors in nude mice contained approximately 1.5 × 10(3) Oct-4-positive cells; however, even 5 × 10(5) undifferentiated ES cells formed neoplasm only in 40% nude mice.

Autologous transplantation of GDNF-expressing mesenchymal stem cells protects against MPTP-induced damage in cynomolgus monkeys.

Glial cell-derived neurotrophic factor (GDNF) has shown beneficial effects in models of Parkinson's disease. The mild results observed in the double-blind clinical trial by intraputamenal infusion of recombinant GDNF proteins warrant a search for alternative delivery methods. In this study, we investigated the function of autologous mesenchymal stem cells (MSCs) expressing GDNF (GDNF-MSCs) for protection against MPTP-induced injury in cynomolgus monkeys. MSCs were obtained from the bone marrow of individual monkeys and gene-modified to express GDNF. Following unilateral engraftment of GDNF-MSCs into the striatum and substantia nigra, the animals were challenged with MPTP to induce a stable systemic Parkinsonian state. The motor functions were spared in the contralateral limbs of monkeys receiving GDNF-MSCs, but not in those receiving MSCs alone. In the striatum of the grafted hemisphere, dopamine levels were higher and dopamine uptake was enhanced. The results suggest that autologous MSCs may be a safe vehicle to deliver GDNF for enhancing nigro-striatum functions.

Spontaneous transformation of cynomolgus mesenchymal stem cells in vitro: further confirmation by short tandem repeat analysis.

It remains a highly debatable issue whether mesenchymal stem cells (MSCs) can undergo spontaneous transformation in culture. Recently, two groups retracted their previous publications due to the finding that the claimed transformed cells are actually contaminating cancer cells, which calls for a more stringent identification of transformed cells in the field. In this study, we continued with our previous finding of spontaneous transformation of cynomolgus MSCs and provided further evidence using short tandem repeat analysis that the transformed mesenchymal stem cells were indeed derived from cynomolgus MSCs.

Effect of monolayer cells on sphere cells--two types of cells that emerge during the neural differentiation of mouse embryonic stem cells.

Embryonic stem (ES) cells represent a valuable resource for transplantation and tissue engineering applications. For derivation of neural cells, a five-stage differentiation protocol has been widely applied, which involves the propagation of ES cells, formation of embryoid bodies (EBs), selection of neural stem cells (NSCs), expansion of NSCs, and further maturation of NSCs to neurons. During the expansion stage (the fourth stage), two types of cells with distinct morphologies normally emerge, with one type being monolayer cells and the other sphere-like aggregates growing on top of the monolayer cells. In this study, we focus on how the monolayer cells may affect different aspects of aggregate cells, which may have important implications for regenerative medicine. We find that monolayer cells can support the proliferation and decrease the apoptosis rate of sphere cells, as well as facilitate the production of Tuj1-positive cells from sphere cells. In addition, transplantation of monolayer cells into nude mice does not result in tumor formation nor affects the tumorigenicity of sphere cells, when grafted together with monolayer cells.

Spontaneous transformation of adult mesenchymal stem cells from cynomolgus macaques in vitro.

Mesenchymal stem cells (MSCs) have shown potential clinical utility in cell therapy and tissue engineering, due to their ability to proliferate as well as to differentiate into multiple lineages, including osteogenic, adipogenic, and chondrogenic specifications. Therefore, it is crucial to assess the safety of MSCs while extensive expansion ex vivo is a prerequisite to obtain the cell numbers for cell transplantation. Here we show that MSCs derived from adult cynomolgus monkey can undergo spontaneous transformation following in vitro culture. In comparison with MSCs, the spontaneously transformed mesenchymal cells (TMCs) display significantly different growth pattern and morphology, reminiscent of the characteristics of tumor cells. Importantly, TMCs are highly tumorigenic, causing subcutaneous tumors when injected into NOD/SCID mice. Moreover, no multiple differentiation potential of TMCs is observed in vitro or in vivo, suggesting that spontaneously transformed adult stem cells may not necessarily turn into cancer stem cells. These data indicate a direct transformation of cynomolgus monkey MSCs into tumor cells following long-term expansion in vitro. The spontaneous transformation of the cultured cynomolgus monkey MSCs may have important implications for ongoing clinical trials and for models of oncogenesis, thus warranting a more strict assessment of MSCs prior to cell therapy.

Efficient human iPS cell derivation by a non-integrating plasmid from blood cells with unique epigenetic and gene expression signatures.

To identify accessible and permissive human cell types for efficient derivation of induced pluripotent stem cells (iPSCs), we investigated epigenetic and gene expression signatures of multiple postnatal cell types such as fibroblasts and blood cells. Our analysis suggested that newborn cord blood (CB) and adult peripheral blood (PB) mononuclear cells (MNCs) display unique signatures that are closer to iPSCs and human embryonic stem cells (ESCs) than age-matched fibroblasts to iPSCs/ESCs, thus making blood MNCs an attractive cell choice for the generation of integration-free iPSCs. Using an improved EBNA1/OriP plasmid expressing 5 reprogramming factors, we demonstrated highly efficient reprogramming of briefly cultured blood MNCs. Within 14 days of one-time transfection by one plasmid, up to 1000 iPSC-like colonies per 2 million transfected CB MNCs were generated. The efficiency of deriving iPSCs from adult PB MNCs was approximately 50-fold lower, but could be enhanced by inclusion of a second EBNA1/OriP plasmid for transient expression of additional genes such as SV40 T antigen. The duration of obtaining bona fide iPSC colonies from adult PB MNCs was reduced to half (∼14 days) as compared to adult fibroblastic cells (28-30 days). More than 9 human iPSC lines derived from PB or CB blood cells are extensively characterized, including those from PB MNCs of an adult patient with sickle cell disease. They lack V(D)J DNA rearrangements and vector DNA after expansion for 10-12 passages. This facile method of generating integration-free human iPSCs from blood MNCs will accelerate their use in both research and future clinical applications.

[Improving infection efficiency of adult cynomolgus monkey mesenchymal stem cells with lentiviral vectors].

Mesenchymal stem cells (MSCs) have received considerable attention for various therapeutic approaches in recent years. MSCs are also easy to genetically modify to express therapeutic genes by using lentiviral vectors. Because of the similarities in genetics, physiology and metabolism between non-human primates (NHPs) and humans, NHPs models are invaluable for researching human disorders and for developing therapeutic strategies. Therefore, MSCs derived from NHPs could be a powerful tool for cell therapy and genetic engineering. Studies from captive and free-ranging adult NHPs show that up to 100% were infected with simian foamy virus (SFV). In this study, we found that all cultured MSCs derived from adult cynomolgus monkey were infected with SFV by RT-PCR. Therefore, antiviral drugs must be added in MSCs culture. However, because of SFV infection and additive antiviral drugs, the infection efficiency of the lentiviral vectors reduced significantly. In this study, we improved the infection efficiency by disabled antiviral drugs before lentiviral infection. It might be provide technical assistance for the culture of adult cynomolgus monkey MSCs as genetically engineered cells applied to clinical and experimental research.

Comparative characterization of mesenchymal stem cells from different age groups of cynomolgus monkeys.

Bone marrow mesenchymal stem cells (BM-MSCs) are a potential tool for cell therapy and tissue engineering. In this study, we carried on a comparative study of the characteristics of MSCs from different age cynomolgus monkeys. A variety of factors, including donor age, must be considered before further applications, and various tests should be used to properly assess MSCs before the clinical application, especially when a prolonged culture and ex vivo expansion is necessary.