Identification and isolation of embryonic stem cells in reproductive endocrinology: theoretical protocols for conservation of human embryos derived from in vitro fertilization

Improved harmonization of critical characterization assays across cell therapies

The field of cell therapy has blossomed, providing exciting new options for treating a variety of diseases. While few cell therapy products have US FDA approval, there are thousands of cell treatments at various stages of development, pointing to a potential revolutionary shift in patient care. The expanding number and nature of cellular therapies necessitate greater standardization. Several international organizations are collaborating to pursue some level of global standardization, especially concerning cell banking. However, less harmonization surrounds assays used for critical quality characterization including: identity, purity, safety and potency. Frequently, there is divergence regarding the terms describing the characterization assays across regulatory authorities and guidances. This review summarizes the critical quality assays currently used for different categories of cell therapies. Areas of harmonization and an absence of standardization are highlighted. We propose potential solutions to facilitate harmonization of critical quality characterization assays and the language used to describe them.

Large-scale expansion of feeder-free mouse embryonic stem cells serially passaged in stirred suspension bioreactors at low inoculation densities directly from cryopreservation

Embryonic stem cells (ESCs) have almost unlimited proliferation capacity in vitro and can retain the ability to contribute to all cell lineages, making them an ideal platform material for cell-based therapies. ESCs are traditionally cultured in static flasks on a feeder layer of murine embryonic fibroblast cells. Although sufficient to generate cells for research purposes, this approach is impractical to achieve large quantities for clinical applications. In this study, we have developed protocols that address a variety of challenges that currently bottleneck clinical translation of ESCs expanded in stirred suspension bioreactors. We demonstrated that mouse ESCs (mESCs) cryopreserved in the absence of feeder cells could be thawed directly into stirred suspension bioreactors at extremely low inoculation densities (100 cells/ml). These cells sustained proliferative capacity through multiple passages and various reactor sizes and geometries, producing clinically relevant numbers (10⁹ cells) and maintaining pluripotency phenotypic and functional properties. Passages were completed in stirred suspension bioreactors of increasing scale, under defined batch conditions which greatly improved resource efficiency. Output mESCs were analyzed for pluripotency marker expression (SSEA-1, SOX-2, and Nanog) through flow cytometry, and spontaneous differentiation and teratoma analysis was used to demonstrate functional maintenance of pluripotency.

Differentiation of neuron-like cells from mouse parthenogenetic embryonic stem cells

Parthenogenetic embryonic stem cells have pluripotent differentiation potentials, akin to fertilized embryo-derived embryonic stem cells. The aim of this study was to compare the neuronal differentiation potential of parthenogenetic and fertilized embryo-derived embryonic stem cells. Before differentiation, karyotype analysis was performed, with normal karyotypes detected in both parthenogenetic and fertilized embryo-derived embryonic stem cells. Sex chromosomes were identified as XX. Immunocytochemistry and quantitative real-time PCR detected high expression of the pluripotent gene, Oct4, at both the mRNA and protein levels, indicating pluripotent differentiation potential of the two embryonic stem cell subtypes. Embryonic stem cells were induced with retinoic acid to form embryoid bodies, and then dispersed into single cells. Single cells were differentiated in N2 differentiation medium for 9 days. Immunocytochemistry showed parthenogenetic and fertilized embryo-derived embryonic stem cells both express the neuronal cell markers nestin, βIII-tubulin and myelin basic protein. Quantitative real-time PCR found expression of neurogenesis related genes (Sox-1, Nestin, GABA, Pax6, Zic5 and Pitx1) in both types of embryonic stem cells, and Oct4 expression was significantly decreased. Nestin and Pax6 expression in parthenogenetic embryonic stem cells was significantly higher than that in fertilized embryo-derived embryonic stem cells. Thus, our experimental findings indicate that parthenogenetic embryonic stem cells have stronger neuronal differentiation potential than fertilized embryo-derived embryonic stem cells.

Human embryonic stem cell lines derived from single blastomeres

The derivation of human embryonic stem (hES) cells currently requires the destruction of ex utero embryos. A previous study in mice indicates that it might be possible to generate embryonic stem (ES) cells using a single-cell biopsy similar to that used in preimplantation genetic diagnosis (PGD), which does not interfere with the embryo's developmental potential. By growing the single blastomere overnight, the resulting cells could be used for both genetic testing and stem cell derivation without affecting the clinical outcome of the procedure. Here we report a series of ten separate experiments demonstrating that hES cells can be derived from single blastomeres. In this proof-of-principle study, multiple biopsies were taken from each embryo using micromanipulation techniques and none of the biopsied embryos were allowed to develop in culture. Nineteen ES-cell-like outgrowths and two stable hES cell lines were obtained. The latter hES cell lines maintained undifferentiated proliferation for more than eight months, and showed normal karyotype and expression of markers of pluripotency, including Oct-4, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, nanog and alkaline phosphatase. These cells retained the potential to form derivatives of all three embryonic germ layers both in vitro and in teratomas. The ability to create new stem cell lines and therapies without destroying embryos would address the ethical concerns of many, and allow the generation of matched tissue for children and siblings born from transferred PGD embryos.

Laser-assisted blastocyst dissection and subsequent cultivation of embryonic stem cells in a serum/cell free culture system: applications and preliminary results in a murine model

Background

To evaluate embryonic stem cell (ESC) harvesting methods with an emphasis on derivation of ESC lines without feeder cells or sera. Using a murine model, laser-assisted blastocyst dissection was performed and compared to conventional immunosurgery to assess a novel laser application for inner cell mass (ICM) isolation.

Methods

Intact blastocysts or isolated ICMs generated in a standard mouse strain were plated in medium with or without serum to compare ESC harvesting efficiency. ESC derivation was also undertaken in a feeder cell-free culture system.

Results

Although ICM growth and dissociation was comparable irrespective of the media components, an enhanced ESC harvest was observed in our serum-free medium (p < 0.01). ESC harvest rate was not affected by ICM isolation technique but was attenuated in the feeder cell-free group.

Conclusion

Achieving successful techniques for human ESC research is fundamentally dependent on preliminary work using experimental animals. In this study, all experimentally developed ESC lines manifested similar features to ESCs obtained from intact blastocysts in standard culture. Cell/sera free murine ESC harvest and propagation are feasible procedures for an embryology laboratory and await refinements for translation to human medical research.

Human embryonic stem cell culture: current limitations and novel strategies

Embryonic stem cells (ESC) are multipotent cells isolated from blastocyst-stage preimplantation embryos. Since their first culture in 1998, human ESC have revolutionized reproductive and regenerative medicine by allowing the establishment of detailed molecular and therapeutic models for certain metabolic pathways and life-threatening disorders. They also offer significant contributions to genetics and pharmacology in designing and analysing disease models that can be closer to in vivo than any other procedures available. However, the procedures by which they are obtained and manipulated also create intense ethical and social debates worldwide. This article discusses the current limitations and recent advances in isolation, culture and differentiation of human ESC from the laboratory perspective.