Cell Replacement Therapy For Diseases Research Articles

Graphene Oxide and Reduced Derivatives, as Powder or Film Scaffolds, Differentially Promote Dopaminergic Neuron Differentiation and Survival.

Emerging scaffold structures made of carbon nanomaterials, such as graphene oxide (GO) have shown efficient bioconjugation with common biomolecules. Previous studies described that GO promotes the differentiation of neural stem cells and may be useful for neural regeneration. In this study, we examined the capacity of GO, full reduced (FRGO), and partially reduced (PRGO) powder and film to support survival, proliferation, differentiation, maturation, and bioenergetic function of a dopaminergic (DA) cell line derived from the mouse substantia nigra (SN4741). Our results show that the morphology of the film and the species of graphene (GO, PRGO, or FRGO) influences the behavior and function of these neurons. In general, we found better biocompatibility of the film species than that of the powder. Analysis of cell viability and cytotoxicity showed good cell survival, a lack of cell death in all GO forms and its derivatives, a decreased proliferation, and increased differentiation over time. Neuronal maturation of SN4741 in all GO forms, and its derivatives were assessed by increased protein levels of tyrosine hydroxylase (TH), dopamine transporter (DAT), the glutamate inward rectifying potassium channel 2 (GIRK2), and of synaptic proteins, such as synaptobrevin and synaptophysin. Notably, PRGO-film increased the levels of Tuj1 and the expression of transcription factors specific for midbrain DA neurons, such as Pitx3, Lmx1a, and Lmx1b. Bioenergetics and mitochondrial dysfunction were evaluated by measuring oxygen consumption modified by distinct GO species and were different between powder and film for the same GO species. Our results indicate that PRGO-film was the best GO species at maintaining mitochondrial function compared to control. Finally, different GO forms, and particularly PRGO-film was also found to prevent the loss of DA cells and the decrease of the α-synuclein (α-syn) in a molecular environment where oxidative stress has been induced to model Parkinson's disease. In conclusion, PRGO-film is the most efficient graphene species at promoting DA differentiation and preventing DA cell loss, thus becoming a suitable scaffold to test new drugs or develop constructs for Parkinson's disease cell replacement therapy.

BMP/SMAD Pathway Promotes Neurogenesis of Midbrain Dopaminergic Neurons In Vivo and in Human Induced Pluripotent and Neural Stem Cells.

The embryonic formation of midbrain dopaminergic (mDA) neurons in vivo provides critical guidelines for the in vitro differentiation of mDA neurons from stem cells, which are currently being developed for Parkinson's disease cell replacement therapy. Bone morphogenetic protein (BMP)/SMAD inhibition is routinely used during early steps of stem cell differentiation protocols, including for the generation of mDA neurons. However, the function of the BMP/SMAD pathway for in vivo specification of mammalian mDA neurons is virtually unknown. Here, we report that BMP5/7-deficient mice (Bmp5-/-; Bmp7-/-) lack mDA neurons due to reduced neurogenesis in the mDA progenitor domain. As molecular mechanisms accounting for these alterations in Bmp5-/-; Bmp7-/- mutants, we have identified expression changes of the BMP/SMAD target genes MSX1/2 (msh homeobox 1/2) and SHH (sonic hedgehog). Conditionally inactivating SMAD1 in neural stem cells of mice in vivo (Smad1Nes) hampered the differentiation of progenitor cells into mDA neurons by preventing cell cycle exit, especially of TH+SOX6+ (tyrosine hydroxylase, SRY-box 6) and TH+GIRK2+ (potassium voltage-gated channel subfamily-J member-6) substantia nigra neurons. BMP5/7 robustly increased the in vitro differentiation of human induced pluripotent stem cells and induced neural stem cells to mDA neurons by up to threefold. In conclusion, we have identified BMP/SMAD signaling as a novel critical pathway orchestrating essential steps of mammalian mDA neurogenesis in vivo that balances progenitor proliferation and differentiation. Moreover, we demonstrate the potential of BMPs to improve the generation of stem-cell-derived mDA neurons in vitro, highlighting the importance of sequential BMP/SMAD inhibition and activation in this process.SIGNIFICANCE STATEMENT We identify bone morphogenetic protein (BMP)/SMAD signaling as a novel essential pathway regulating the development of mammalian midbrain dopaminergic (mDA) neurons in vivo and provide insights into the molecular mechanisms of this process. BMP5/7 regulate MSX1/2 (msh homeobox 1/2) and SHH (sonic hedgehog) expression to direct mDA neurogenesis. Moreover, the BMP signaling component SMAD1 controls the differentiation of mDA progenitors, particularly to substantia nigra neurons, by directing their cell cycle exit. Importantly, BMP5/7 increase robustly the differentiation of human induced pluripotent and induced neural stem cells to mDA neurons. BMP/SMAD are routinely inhibited in initial stages of stem cell differentiation protocols currently being developed for Parkinson's disease cell replacement therapies. Therefore, our findings on opposing roles of the BMP/SMAD pathway during in vitro mDA neurogenesis might improve these procedures significantly.

193. Establishment of an Optimization Procedure for Large-Scale Production of Patient-Specific Cardiomyocytes from hiPSCs

Cardiovascular diseases are a leading cause of morbidity and mortality worldwide. Human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs), with their ability of indefinite self-renewal and capability to differentiate into all three germ layers, provide a powerful tool in developmental biology, for drug screening, disease modeling, and potentially cell replacement therapy for diseases, such as myocardial infarction and heart failure. Unlike hESCs, hiPSCs are generated from reprogrammed somatic cells without using of human embryos and thus hold a great promise for cell-based therapy as they avoid ethical and immune rejection issues. However, due to scalability limitation of current hiPSC adherent culture platform and potential variation of culture and differentiation conditions among hiPSC lines, production of hiPSC-derived cells to a scale sufficient for therapeutic application in a timely manner has been challenging. Previously we have developed a scalable, defined, and cGMP-compliant suspension culture system for hPSC expansion and cardiac differentiation using spinner flasks by optimizing critical culture parameters we identified. In the present study, we tested the feasibility of applying our suspension culture platform and optimization strategy to establish a process for scale-up production of cardiomyocytes (CM) from individual hiPSC lines in a timely manner. We optimized cell seeding density, agitation rate, concentration of differentiation inducer, and timing for differentiation induction to determine an optimal condition for large-scale CM production. The process from suspension adaptation, differentiation optimization to CM production was accomplished in 3 months. With optimized culture and differentiation conditions, we showed that the hiPSC suspension culture can be serially passaged and expanded, and maintained normal karyotype. At a scale of 500mL suspension culture, 4-5×108 cells with 70-90% CM purity were manufactured. In summary, we demonstrated the feasibility of applying the suspension culture platform and optimization strategy we developed to establish a production process for individual hiPSC line to manufacture CM in a large scale in a timely manner.

Liver Growth Factor Promotes the Survival of Grafted Neural Stem Cells in a Rat Model of Parkinson's Disease

Neural stem cells (NSCs) with self-renewal and multilineage potential are considered good candidates for cell replacement of damaged nerve tissue. Several studies have focused on the ability of the neurotrophic factors coadministration to improve the efficiency of grafted NSCs. Liver growth factor (LGF) is an hepatic mitogen that promotes regeneration of damaged tissues, including brain tissue. It has neurogenic activity and has partially restored the nigrostriatal dopaminergic system in an experimental model of Parkinson's disease. Present results demonstrate that in the dopamine- depleted striatum of 6-hydroxydopamine-lesioned rats, grafted NSCs retained their ability to differentiate into neurons, astrocytes, and oligodendrocytes. NSCs also differentiated into microglia/macrophages and endothelial cells. Thus, 23 ± 5.6% of them were inmunoreactive for isolectin IB4, and a small population integrated into blood vessels, showing an endothelial-like morphology. Intrastriatal infusion of LGF promoted the viability of the implants, and favored their differentiation to an endothelial-like phenotype. Moreover, LGF infusion raised the expression of the anti-apoptotic protein Bcl-2 by 3.9 ± 0.9 fold without affecting the levels of the pro-apoptotic protein Bax. Since LGF-treated rats also showed a significant reduction in apomorphine-induced rotational behavior, our results suggest that administration of this factor might be a convenient treatment for Parkinson's disease cell replacement therapies based on NSCs transplantation.

α-Chemokines Regulate Proliferation, Neurogenesis, and Dopaminergic Differentiation of Ventral Midbrain Precursors and Neurospheres

Increasing evidence suggests that alpha-chemokines serve several important functions in the nervous system, including regulation of neuroimmune responses, neurotransmission, neuronal survival, and central nervous system development. In this study, we first examined the function of two alpha-chemokines, chemokine ligand (CXCL) 6 and CXCL8, and their receptors, CXCR1 and CXCR2, in the developing rat ventral midbrain (VM). We found that CXCR2 and CXCL6 are regulated during VM development and that CXCL6 promotes the differentiation of nurr77-related receptor (Nurr1)+ precursors into dopaminergic (DA) neurons in vitro. Intriguingly, CXCL8, a ligand expressed only in Homo sapiens, enhanced progenitor cell division, neurogenesis, and tyrosine hydroxylase-positive (TH+) cell number in rodent precursor and neurosphere cultures. CXCL1, the murine ortholog of CXCL8, was developmentally regulated in the VM and exhibited activities similar but not identical to those of CXCL8. TH+ cells derived from chemokine-treated VM neurospheres coexpressed Nurr1 and VMAT and were functionally active, as shown by calcium (Ca(2+)) fluxes in response to AMPA. In conclusion, our data demonstrate that CXCL1, CXCL6, and CXCL8 increase the number of DA neurons in VM precursor and neurosphere cultures by diverse mechanisms. Thus, alpha-chemokines may find an application in the preparation of cells for drug development or Parkinson's disease cell replacement therapy.

An efficient and safe xeno-free cryopreservation method for the storage of human embryonic stem cells.

Human embryonic stem cells (hESCs) promise to revolutionize reparative medicine through their potential in developing cell replacement therapies for diseases like diabetes and parkinsonism. Most of the existing hESC lines available for research, including all National Institutes of Health-registered lines, have been derived and maintained on mouse embryonic fibroblast feeders in the presence of xenoproteins. For future clinical application, many more hESC lines derived and grown in current good manufacturing practice, good tissue culture practice, and xeno-free conditions need to be developed. Concurrently, effective cryopreservation methods that prevent or limit the accidental contact of hESCs with nonsterile liquid nitrogen during periods of long-term storage have to be formulated. We describe a safe, xeno-free cryopreservation protocol for hESCs involving vitrification in closed sealed straws using human serum albumin as opposed to fetal calf serum as the main protein source in the cryoprotectant and long-term storage in the vapor phase of liquid nitrogen. After thaw, hESCs exhibited high thaw-survival rates and low differentiation rates, remained pluripotent, and maintained normal diploid karyotypes throughout extended passage. The cryopreservation technique we describe here should complement xeno-free culture conditions for hESCs already in refinement and will prove very useful for the setting up of hESC banks throughout the world.