3D Confinement Regulates Cell Life and Death

Biophysical properties of the cellular microenvironment, including stiffness and geometry, have been shown to influence cell function. Recent findings have implicated 3D confinement as an important regulator of cell behavior. The understanding of how mechanical signals direct cell function is based primarily on 2D studies. To investigate how the extent of 3D confinement affects cell function, a single cell culture platform is fabricated with geometrically defined and fully enclosed microwells and it is applied to investigate how niche volume and stiffness affect human mesenchymal stem cells (hMSC) life and death. The viability and proliferation of hMSCs in confined 3D microniches are compared with unconfined cells in 2D. Confinement biases hMSC viability and proliferation, and this influence depends on the niche volume and stiffness. The rate of cell death increases and proliferation markedly decreases upon 3D confinement. The observed differences in hMSC behavior are correlated to changes in nuclear morphology and YES‐associated protein (YAP) localization. In smaller 3D microniches, hMSCs display smaller and more rounded nuclei and primarily cytoplasmic YAP localization, indicating reduced mechanical activation upon confinement. Interestingly, these effects scale with the extent of 3D confinement. These results demonstrate that the extent of confinement in 3D can be an important regulator of cell function. An engineered microniche platform is used to culture individual cells in fully enclosed microenvironments under varying extents of 3D confinement. The extent of 3D confinement affects cell viability and proliferation. Confinement effects are mediated via mechanosensitive pathways, including YAP/TAZ signaling, F‐actin accumulation, and nuclear sphericity. This study provides new insight into the understanding of confinement mechanobiology.