MUC5AC and chronic obstructive pulmonary disease: Quantification of the two main mucins, MUC5B and MUC5AC, in supernatants after day 45 of differentiation (at least n = 3 independent experiments for each cell line) showed that MUC5B was the predominant mucin secreted by healthy control (HY03 cells: 0.001 (0.7-4-0.004 fmol/μL) and COPD hiPSC-derived cultures (0.012 (0.8-4-0.06) fmol/μL) (Figure 4I).