Optimization of chemical and physical factors toward clinically enabling culture of pluripotent stem cells

Since the original derivation of human embryonic stem cells (hESC) in 1998, development of efficient culture systems to produce and expand clinical-grade human pluripotent stem cells (hPSC) has been an extremely active research field. Despite the significant progress over the last decade, however, the pathways and signaling cues associated with survival, self-renewal and differentiation of hPSC have not been fully understood yet. Recent development in 2D adherent culture methods has given a wealth of information in hPSC regulations, but limitations in scalability, reproducibility and control in culture parameters and chemical gradients still represent a daunting task to improve the cell expansion rate. Advancing from 2D cultures, cultivating hPSC in 3D culture systems sets a more promising standard for large-scale production and establishing a good manufacturing practice (GMP). Here we will first discuss the potential of 3D culture systems, such as suspended cells in a bioreactor. We will then review mechanisms that help the cells to grow under suspension. Moreover, an advantage of using 3D system, besides scalability, is the enhanced control in culture conditions and reproducibility. In light of these advantages, we will discuss our strategy to minimize unknown variables by setting consistent conditions. Further, we will discuss how these variations may be instituted to optimize the parameters to meet the best condition for survival, self-renewal and differentiation.