Embryonic stem (ES) cells possess unlimited self-renewal ability and the potential of differentiating to all tissue organs, making ES cells the ideal source for cell therapy and drug screening. However, present culture techniques are both expensive and labor intensive, unable to meet the projected high demand for ES cells.
Three-dimensional culture is capable of mimicking in vivo growth environment and therefore, cells show their native morphology and functions. 3-D culture is superior to 2-D culture by eliminating the necessity of gelatin coating and frequent subculture. The STO cells conditioned medium is capable of replacing expensive cytokine leukemia inhibitory factor (LIF). Dynamic culture of ES cells in spinner flasks showed better cell growth and maintenance of pluripotency. Further scale up to a two stage perfusion culture system was successful, providing higher cell expansion and Oct-4 and SSEA-1 expressions. Human ES cells expansion in perfusion bioreactor also reached the success. hES cells grows faster in FBB than on 2-D surface. The hES cells pluripotency was also maintained well. However, neural differentiation efficiency was lower in 3-D culture than in 2-D system due to the higher possibility of causing de-differentiation in 3-D system. Astrocyte conditioned medium was superior to retinoic acid in inducing neural differentiation.
Hydrodynamics and its influence on cell attachment and growth in 3-D cultures were also studied. Increased mixing intensity enhanced both cell attachment and detachment rates. Cell detachment kinetics can be described by Bell model. The interaction between Kolmogorov eddy size and the scaffold's pore size played a vital role in affecting shear damage to cells growing in the scaffold. When Kolmogorov eddy size is smaller than the pore size, shear damage to cells is apparent.
Mathematical modeling of the fibrous bed bioreactor (FBB) was investigated too. Axial dispersion model can represent the mass transfer in ordered disc packed FBB. However, both radial and axial dispersion plus convection contribute significantly to the mass transfer in spiral wound FBB. Packing methods showed different performance in different scales. Cell aggregate size should be controlled less than at 170 μm if there is 30% DO.
|Commitee:||Koelling, Kurt, Wyslouzil, Barbara|
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Keywords:||3-D culture, Embryonic stem cell, Fibrous bed bioreactor, Pet scaffold|
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