Human rIL-13 promotes phosphorylation of STAT6 and maturation and proliferation in SPEM cells in human metaplastic gastroids. (A) Representative bright field images of Matrigel domes containing human metaplastic gastroids treated with either rIL-13 or control (BSA). Quantitation of matched gastroid diameters showed significantly higher sizes in gastroids treated with rIL-13 compared with control after 5 days of treatment. Scale bar: 500 μm for brightfield. Mean ± SD (N = 3 independent experiments). ∗∗∗∗P < .0001. (B) Immunoblotting shows up-regulation of pSTAT6 in human metaplastic gastroids treated with rIL-13. Mean ± SD (N = 3 independent experiments). ∗∗∗P < .001. (C) Immunofluorescence staining of human metaplastic gastroids cross sections for Ki67, a proliferation marker, and SPEM-related markers, MUC6 and CD44v9. Quantitation of MUC6 and CD44v9 double positive cells demonstrated significant increase in proportion of mature SPEM cells in rIL-13–treated gastroids. (D) Quantitation of MUC6, CD44v9, and Ki67 triple positive cells demonstrated significant increase in proportion of proliferative SPEM cells. Yellow arrowheads indicate triple positive mature and proliferative SPEM cells. Scale bar: 50 μm. Mean ± SD (N = 8 from 3 independent experiments). ∗∗∗∗P < .0001.