Bioengineering Considerations for a Nurturing Way to Enhance Scalable Expansion of Human Pluripotent Stem Cells

Abstract

Understanding how defects in mechanotransduction affect cell‐to‐cell variability will add to the fundamental knowledge of human pluripotent stem cell (hPSC) culture, and may suggest new approaches for achieving a robust, reproducible, and scalable process that result in consistent product quality and yields. Here, the current state of the understanding of the fundamental mechanisms that govern the growth kinetics of hPSCs between static and dynamic cultures is reviewed, the factors causing fluctuations are identified, and culture strategies that might eliminate or minimize the occurrence of cell‐to‐cell variability arising from these fluctuations are discussed. The existing challenges in the development of hPSC expansion methods for enabling the transition from process development to large‐scale production are addressed, a mandatory step for industrial and clinical applications of hPSCs.

Induced pluripotency in the context of stem cell expansion bioprocess development, optimization, and manufacturing: a roadmap to the clinic

“…The lack of success leading to suspension of many iPSC clinical trials specifically highlights a need to further elucidate the interplay between variables over the course of the bioprocess and their influence on stem-cell-derived product identity and function. Further, a lack of process robustness in conventional systems and protocols result in a high degree of in-process heterogeneity observed within batch populations and between-culture batches 22 . This heterogeneity reflects the high phenotypic plasticity of pluripotent stem cells, and the non-uniform spatiotemporal conditions observed across bioprocess systems 23 .…”

Mechanobiological conceptual framework for assessing stem cell bioprocess effectiveness

“…Understanding the prevalence of pre‐existing intrinsic and extrinsic variability over external noise is important for developing key indicators to identify and predict bioprocess variability. The phenomenon of “intrinsic disorder” has been widely studied in bioprocess conditions, and understanding and controlling the sources of variability should play important roles in improving bioprocess control and optimization (Kim & Kino‐oka, 2018, 2020a; Misener et al, 2018). Figure 2 illustrates the major mechanical forces generated by cells and their environment, which are factors that cause intrinsic disorder in the bioprocess.…”

Mechanobiological conceptual framework for assessing stem cell bioprocess effectiveness

“…For successful development and optimization of stem cell bioprocesses, we must study the fluctuations in current bioprocesses and the variability in stem cells and derived products allowed by regulators and their applications to obtain an understanding of improvement areas (Kim and Kino-oka, 2020a;Kim and Kino-oka, 2020b). The main problem is the lack of biological indicators that use formulas to facilitate their assessment and comparability of bioprocess effectiveness for various external stimuli.…”

“…Many studies have focused on the development of culture strategies that can recapitulate the physico-chemical properties of the complex native cellular microenvironment (Jo et al, 2020;Li et al, 2021). A large effort has been made over the last decades to propose various strategies to develop affordable high-quality cell-based products in a reproduceable and robust manner (Kim and Kino-oka, 2018;Kim and Kino-oka, 2020a). However, a knowledge gap that still exists in the mechanobiological sciences for the stem cell bioprocess development, optimization and characterization is not currently being filled by the bioprocess research.…”