Substrates and supplements for hESCs: a critical review

Optimization of bovine embryonic fibroblast feeder layer prepared by Mitomycin C

Feeder cells play important roles in In-vitro culture of stem cells. However, the preparation protocol of feeder cells produced by bovine embryonic fibroblast cells (bEFs) is still lack. In this study, the preparation of bEF-feeder by Mitomycin C was optimized with different concentrations and treatment time. The cell viability of bEFs was detected by CCK8 and 5-Ethynyl-2'-deoxyuridine. The growth of bESCs in each bEFs-feeder group was assessed by alkaline phosphatase staining and CCK8. Quantitative real time PCR was used to detect the mRNA expression of pluripotency-related genes of bESCs. Results showed that the proliferation of bEFs was significantly repressed while bEFs were treated with 14 ug/mL or 16 ug/mL Mitomycin C for 3 h, and the cell viability within 2-4 days after treatment was consistent with the 1st day. The numbers of bESCs clones in bEF-feeder treated with 14 μg/mL Mitomycin C for 3 h or 16 μg/mL Mitomycin C for 3 h were significantly higher than that in bEF-feeder treated with 8 μg/mL Mitomycin C for 8 h or bEFs treated with 6 μg/mL Mitomycin C for 9 h. The mRNA expression of pluripotency-related genes in bESCs cultured by bEF-feeder were higher than the MEF-feeder, the clone morphology of bESCs cultured in bEF-feeder was rounder and sharper than the MEF-feeder. In conclusion, the bEF-feeder prepared with 14 μg/mL Mitomycin C for 3 h or 16 μg/mL Mitomycin C for 3 h could effectively maintains the growth of bESCs, and bEF-feeder is more suitable for bESCs culture than the MEF-feeder.

Interaction of fibroblasts and induced pluripotent stem cells with poly(vinyl alcohol)-based hydrogel substrates

Induced pluripotent stem cells (iPSCs) provide a promising means of creating custom-tailored cell lines for cellular therapies. Their application in regenerative medicine, however, depends on the possibility that the maintenance and differentiation of cells and organs occur under defined conditions. One major component of stem cell culture systems is the substrate, where the cells must attach and proliferate. The present study aimed to investigate the putative cytotoxic effects of poly(vinyl alcohol) (PVA)-based matrices on the in vitro culture of mouse fetal fibroblasts. In addition, the PVA-based hydrogels were used to determine the capacity of bovine induced pluripotent stem cells (biPSCs) to adhere and proliferate on synthetic substrates. Our results show that both cell types interacted with the substrate and presented proliferation during culture. The biPSCs formed new colonies when cell suspensions were placed onto the hydrogel surface for culture. These results may represent a new characterized xeno-free clinical grade culture system to be widely applied in cell-based therapies.

A fully defined static suspension culture system for large-scale human embryonic stem cell production

Human embryonic stem cells (hESCs) play an important role in regenerative medicine due to their potential to differentiate into various functional cells. However, the conventional adherent culture system poses challenges to mass production of high-quality hESCs. Though scientists have made many attempts to establish a robust and economical hESC suspension culture system, there are existing limitations, including suboptimal passage methods and shear force caused by dynamic stirring. Here, we report on an efficient large-scale culture system, which enables long-term, GMP grade, single-cell inoculation, and serial expansion of hESCs with a yield of about 1.5 × 10⁹ cells per 1.5-L culture, while maintaining good pluripotency. The suspension culture system was enlarged gradually from a 100-mm dish to a 1.8-L culture bag with methylcellulose involvement to avoid sphere fusion. Under the optimal experimental protocol, this 3D system resolves current problems that limit mass production and clinical application of hESCs, and thus can be used in commercial-level hESC production for cell therapy and pharmaceutics screening in the future.

High quality clinical grade human embryonic stem cell lines derived from fresh discarded embryos

BACKGROUND

Human embryonic stem cells (hESCs) hold tremendous promise for cell replacement therapies for a range of degenerative diseases. In order to provide cost-effective treatments affordable by public health systems, HLA-matched allogeneic tissue banks of the highest quality clinical-grade hESCs will be required. However only a small number of existing hESC lines are suitable for clinical use; they are limited by moral and ethical concerns and none of them apply Good Manufacturing Practice (GMP) standards to the earliest and critical stages of gamete and embryo procurement. We thus aimed to derive new clinical grade hESC lines of highest quality from fresh surplus GMP grade human embryos.

METHODS

A comprehensive screen was performed for suitable combinations of culture media with supporting feeder cells or feeder-free matrix, at different stages, to support expansion of the inner cell mass and to establish new hESC lines.

RESULTS

We developed a novel two-step and sequential media system of clinical-grade hESC derivation and successfully generated seven new hESC lines of widely varying HLA type, carefully screened for genetic health, from human embryos donated under the highest ethical and moral standards under an integrated GMP system which extends from hESC banking all the way back to gamete and embryo procurement.

CONCLUSIONS

The present study, for the first time, reports the successful derivation of highest-quality clinical-grade hESC lines from fresh poor-quality surplus human embryos generated in a GMP-grade IVF laboratory. The availability of hESC lines of this status represents an important step towards more widespread application of regenerative medicine therapies.

Modeling neurodevelopmental disorders using human pluripotent stem cells

Neurodevelopmental disorders (NDs) are impairments that affect the development and growth of the brain and the central nervous system during embryonic and early postnatal life. Genetically manipulated animals have contributed greatly to the advancement of ND research, but many of them differ considerably from the human phenotype. Cellular in vitro models are also valuable, but the availability of human neuronal cells is limited and their lifespan in culture is short. Human pluripotent stem cells (hPSCs), including embryonic stem cells and induced pluripotent stem cells, comprise a powerful tool for studying developmentally regulated diseases, including NDs. We reviewed all recent studies in which hPSCs were used as in vitro models for diseases and syndromes characterized by impairment of neurogenesis or synaptogenesis leading to intellectual disability and delayed neurodevelopment. We analyzed their methodology and results, focusing on the data obtained following in vitro neural differentiation and gene expression and profiling of the derived neurons. Electrophysiological recording of action potentials, synaptic currents and response to neurotransmitters is pivotal for validation of the neuronal fate as well as for assessing phenotypic dysfunctions linked to the disease in question. We therefore focused on the studies which included electrophysiological recordings on the in vitro-derived neurons. Finally, we addressed specific issues that are critical for the advancement of this area of research, specifically in providing a reliable human pre-clinical research model and drug screening platform.

Redox status in mammalian cells and stem cells during culture in vitro: critical roles of Nrf2 and cystine transporter activity in the maintenance of redox balance

Culturing cells and tissues in vitro has provided valuable insights into the molecular mechanisms regulating redox signaling in cells with implications for medicine. However, standard culture techniques maintain mammalian cells in vitro under an artificial physicochemical environment such as ambient air and 5% CO2. Oxidative stress is caused by the rapid oxidation of cysteine to cystine in culture media catalyzed by transition metals, leading to diminished intracellular cysteine and glutathione (GSH) pools. Some cells, such as fibroblasts and macrophages, express cystine transport activity, designated as system [Formula: see text], which enables cells to maintain these pools to counteract oxidative stress. Additionally, many cells have the ability to activate the redox sensitive transcription factor Nrf2, a master regulator of cellular defenses against oxidative stress, and to upregulate xCT, the subunit of the [Formula: see text] transport system leading to increases in cellular GSH. In contrast, some cells, including lymphoid cells, embryonic stem cells and iPS cells, express relatively low levels of xCT and cannot maintain cellular cysteine and GSH pools. Thus, fibroblasts have been used as feeder cells for the latter cell types based on their ability to supply cysteine. Other key Nrf2 regulated gene products include heme oxygenase 1, peroxiredoxin 1 and sequestosome1. In macrophages, oxidized LDL activates Nrf2 and upregulates the scavenger receptor CD36 forming a positive feedback loop to facilitate removal of the oxidant from the vascular microenvironment. This review describes cell type specific responses to oxygen derived stress, and the key roles that activation of Nrf2 and membrane transport of cystine and cysteine play in the maintenance and proliferation of mammalian cells in culture.