Mass transfer limitations in embryoid bodies during human embryonic stem cell differentiation

Area of Science:

• Stem cell biology
• Biomedical engineering
• Developmental biology

Background:

• Embryonic stem cells (ESCs) can differentiate into all cell types, offering therapeutic potential.
• Human embryonic stem cell (hESC) differentiation is influenced by embryoid body (EB) size.
• Nutrient and growth factor diffusion dynamics within EBs are critical for controlling differentiation.

Purpose of the Study:

• To investigate the relationship between nutrient mass transfer, EB size, and hESC differentiation.
• To model the impact of EB size on oxygen and cytokine concentration gradients.
• To correlate model predictions with experimental data on stem cell differentiation.

Main Methods:

• Development of a transient mass diffusion model for a single hESC EB.
• Simulation of oxygen and cytokine concentration profiles within EBs of varying sizes (200-μm and 400-μm radius).
• Comparison of model outputs with published experimental data on hESC differentiation.

Main Results:

• Larger EBs (400-μm radius) exhibited 50% lower oxygen concentration at their centers compared to smaller EBs (200-μm radius).
• Cytokine concentration profiles within EBs were highly dependent on depletion rates, leading to significant spatial variations.
• Model results showed a strong correlation between cell differentiation fractions and exposure to specific oxygen or cytokine concentrations.

Conclusions:

• Diffusive mass transfer significantly influences hESC differentiation within EBs by controlling the spatial distribution of soluble factors.
• EB size and mass transfer dynamics are critical parameters for controlling stem cell differentiation trajectories.
• These findings have implications for designing effective stem cell differentiation protocols and bioprocesses.