Fig. 2 Hydrogel stress relaxation regulates cell cycle progression from the G1 phase to the S phase. Hydrogel stress relaxation regulates cell cycle progression from the G1 phase to the S phase. (A) Cell cycle analysis of cells cultured in slow-, medium-, and fast-relaxing gels for 10 days, measured by flow cytometry. Inset, fluorescence intensity (FI) versus forward scatter (FSC). Red rectangle indicates a gate of cell population. A.U., arbitrary units. (B) Population of cells in G0/G1, S, and G2/M phases in soft (3 kPa) and stiff (16 kPa) gels with varying relaxation (n = 2 to 4 per each condition). (C) Population of cells in the G0/G1 phase as a function of relaxation time. (D) A schematic of cell cycle progression including a mechanical checkpoint associated with hydrogel relaxation or mechanical confinement identified by the studies. Data are shown as means ± SD. Sungmin Nam et al. Sci Adv 2019;5:eaaw6171 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).