RT Journal Article SR Electronic T1 3D confinement regulates stem cell fate JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.05.02.442094 DO 10.1101/2021.05.02.442094 A1 Oksana Y. Dudaryeva A1 Aurelia Bucciarelli A1 Giovanni Bovone A1 Shibashish Jaydev A1 Nicolas Broguiere A1 Marwa al-Bayati A1 Marco Lütolf A1 Mark W. Tibbitt YR 2021 UL http://biorxiv.org/content/early/2021/05/03/2021.05.02.442094.abstract AB Biophysical properties of the cellular microenvironment, including stiffness and geometry, influence cell fate. Recent findings have implicated geometric confinement as an important regulator of cell fate determination. Our understanding of how mechanical signals direct cell fate is based primarily on two-dimensional (2D) studies. To investigate the role of confinement on stem cell fate in three-dimensional (3D) culture, we fabricated a single cell microwell culture platform and used it to investigate how niche volume and stiffness affect human mesenchymal stem cell (hMSC) fate. The viability and proliferation of hMSCs in confined 3D microniches were compared with the fate of unconfined cells in 2D culture. Physical confinement biased hMSC fate, and this influence was modulated by the niche volume and stiffness. The rate of cell death increased, and proliferation markedly decreased upon 3D confinement. We correlated the observed differences in hMSC fate to YES-associated protein (YAP) localization. In 3D microniches, hMSCs displayed primarily cytoplasmic YAP localization, indicating reduced mechanical activation upon confinement. These results demonstrate that 3D geometric confinement can be an important regulator of cell fate, and that confinement sensing is linked to canonical mechanotransduction pathways.Competing Interest StatementThe authors have declared no competing interest.2Dtwo-dimensional3Dthree-dimensionalDAPI4′, 6-diamidino-2-phenylindoleEYoung′s modulusEdU5-ethynyl-2′-deoxyuridineECMextracellular matrixEthD-1ethidium homodimerDTTdithiothreitolG′shear storage modulusG′′shear loss modulushMSCshuman mesenchymal stem cellsPDMSpolydimethylsiloxanePEGpoly(ethylene glycol)YAPYES-associated protein.