Factorial design models relating signaling input and specific growth rate values of mES cells cultured at different oxygen tensions.

mES cells were expanded for a total of 10 days in culture (five consecutive passages) under normoxic (a, b, and c) or hypoxic conditions (d, e, and f). Effect magnitudes of all main factors, second order effects, and two-way interactions were obtained for 20% O2 (a) and 2% O2 (d). The coefficients of the models were then determined following a sequential backward elimination procedure, where the least significant terms (p>0.05) were eliminated and absorbed into the error. 3D representations for both 20% O2 and 2% O2 models are shown in (b) and (e), respectively, as a function of LIF and CHIR levels. Two-factor interaction heat maps are also shown for 20% O2 (c) and 2% O2 (f). White dots represent conditions that maximize the response. For LIF: 0 U/mL (−1 level) ≤ [LIF] ≤1000 U/mL (1 level); for CHIR: 0 µM (−1 level) ≤ [CHIR] ≤6 µM (1 level).