Embryoid body formation from embryonic and induced pluripotent stem cells:Benefits of bioreactors

Embryonic stem(ES)cells have the ability to differ-entiate into all germ layers,holding great promise not only for a model of early embryonic development but also for a robust cell source for cell-replacement therapies and for drug screening.Embryoid body (EB)formation from ES cells is a common method for producing different cell lineages for further applications. However,conventional techniques such as hanging drop or static suspension culture are either inherently incapable of large scale production or exhibit limited control over cell aggregation during EB formation and subsequent EB aggregation.For standardized mass EB production,a well defined scale-up platform is necessary.Recently,novel scenario methods of EB formation in hydrodynamic conditions created by bioreactor culture systems using stirred suspension systems(spinner flasks),rotating cell culture system and rotary orbital culture have allowed large-scale EB formation.Their use allows for continuous monitoring and control of the physical and chemical environment which is difficult to achieve by traditional methods.This review summarizes the current state of production of EBs derived from pluripotent cells in various culture systems.Furthermore,an overview of high quality EB formation strategies coupled with systems for in vitro differentiation into various cell types to be applied in cell replacement therapy is provided in this review. Recently,new insights in induced pluripotent stem(iPS) cell technology showed that differentiation and lineage commitment are not irreversible processes and this has opened new avenues in stem cell research.These cells are equivalent to ES cells in terms of both self-renewal and differentiation capacity.Hence,culture systems for expansion and differentiation of iPS cells can also apply methodologies developed with ES cells,although direct evidence of their use for iPS cells is still limited.

Gene targeting and Calcium handling efficiencies in mouse embryonic stem cell lines

AIM:To compare gene targeting efficiencies,expression profiles,and Ca2+ handling potentials in two widely used mouse embryonic stem cell lines.METHODS:The two widely used mouse embryonic stem cell lines,R1 and HM-1,were cultured and maintained on Mitomycin C treated mouse embryonic fibroblast feeder cell layers,following standard culture procedures.Cells were incubated with primary and secondary antibodies before fluorescence activated cell sorting analysis to compare known pluripotency markers.Moreover,cells were harvested by trypsinization and transfected with a kinase-inactive murine Tyk2 targeting construct,following the BioRad and Amaxa transfection procedures.Subsequently,the cells were cultured and neomycin-resistant cells were picked after 13 d of selection.Surviving clones were screened twice by polymerase chain reaction(PCR) and finally confirmed by Southern blot analysis before comparison.Global gene expression profiles of more than 20 400 probes were also compared and significantly regulated genes were conf irmed by real time PCR analysis.Calcium handling potentials of these cell lines were also compared using various agonists.RESULTS:We found signif icant differences in transfection eff iciencies of the two cell lines(91% ± 6.1% vs 75% ± 4.2%,P = 0.01).Differences in the targeting efficiencies were also significant whether the Amaxa or BioRad platforms were used for comparison.We did not observe signif icant differences in the levels of many known pluripotency markers.However,our genomewide expression analysis using more than 20 400 spotted cDNA arrays identified 55 differentially regulated transcripts(P < 0.05) implicated in various important biological processes,including binding molecular functions(particularly Ca2+ binding roles).Subsequently,we measured Ca2+ signals in these cell lines in response to various calcium agonists,both in high and low Ca2+ solutions,and found signif icant differences(P < 0.05) in the regulation of Ca2+ homeostasis between the investigated cell lines.Then we further compared the detection and expression of various membrane and in-tracellular Ca2+ receptors and similarly found signif icant(P < 0.05) variations in a number of calcium receptors between these cell lines.CONCLUSION:Results of this study emphasize the importance of considering intrinsic cellular variations,during selection of cell lines for experiments and interpretations of experimental results.