Figure 6: STAT6 signaling expression and function in histamine-medicated regulation of cardiac fibrosis post-MI.

(a) Western blotting showed that exogenous histamine (10⁻⁵ M) could increase phosphorylated STAT6 expression in the heart fibroblasts of WT mice (n = 3). (b) Exogenous histamine (10⁻⁵ M) had no inhibitive effect on the heart fibroblasts of STAT6^−/− mice (n = 3). (c) The inhibitive effect of histamine on the proliferation of heart fibroblasts of WT mice could be blocked by CP-690550 (n = 3). (d) H&E staining showed that STAT6 knockout caused larger infarct sizes at 4 weeks post-MI (scale bar = 500 μm; n = 8–10). (e–g) Echocardiography showed that STAT6^−/− mice had worse cardiac remodeling and function post-MI than WT mice and that exogenous histamine had no beneficial effect on STAT6^−/− mice (n = 10–12). (h) Masson trichrome staining showed that cardiac fibrosis was significantly enhanced in STAT6^−/− mice compared with WT mice and that exogenous histamine had no beneficial effect on STAT6^−/− mice (the top scale bar = 500 μm and other scale bars = 50 μm; n = 6–8). NS, not statistically significant, *p < 0.05, **p < 0.01.