Microscale biomechanics: Studies of Neurogenesis and Stem Cell Differentiation under Micromechanical Influences

Two types of stem cells, one from neonatal rat brains and the other from hydra body columns, are being studied with quantified mechanical stimulations. MEMS polysilicon clamp and ratchet microstructure has been designed to exert mechanical tension along radial glial processes between groups of neural stem cells to study the effect of tension on cerebral cortex neurogenesis. Preliminary studies show that embryonic brain tissue survives under tension for at least six days. Neurospheres have been successfully cultured on poly-dimethyl-siloxane (PDMS) substrate for eight days and exhibit radial extensions which appear to support neuronal migration. Stretching the PDMS using the clamp and ratchet would produce tension in these radial extensions which may modulate neuronal migration, a key process in cerebral cortex development. To study the responses of hydra stem cells to mechanical stimuli, a 6-foot water column is constructed to observe hydra regeneration, and thus stem cell differentiation, under various levels of static pressure. Several dissected hydras were injected into a PDMS trap and then lowered into the water column at specific depths. There appears a connection between the level of environmental pressure, available resources, and the ability of the hydra to regenerate. The preliminary results from these two diverse types of stem cells support the hypothesis that mechanical stimulations are important factors that influence stem cell fates