Figure 3. Collagen fiber deposition in the infarct region of iRhom2-deficient hearts at day 21 after myocardial infarction (MI).

(A and B) Masson’s trichrome staining revealed wild-type hearts with strong collagen expression in the infarct region, with minimal viable myocardial tissue remaining 21 days after injury. However, iRhom2-deficient (iRhom2^–/–) hearts had reduced collagen staining within the scar, with evidence of viable myocardium (arrows). Representative images are based on 3 biological replicates. (C and D) Immunohistochemistry showed a significant reduction in type I collagen expression in the scar of iRhom2^–/– hearts compared with wild-type hearts, and (right panel) collagen expression was quantified. (E and F) Picrosirius red staining imaged using bright-field microscopy showed a less uniform distribution of collagen in iRhom2^–/– hearts at 21 days after MI compared with controls. (G and H) Polarized-light microscopy revealed reduced mature type I collagen (red) in iRhom2^–/– compared with control injured hearts, while no differences in immature type III collagen (green) were observed, (right panel), which was quantified. Scale bars: 1 mm and 100 μm (insets). Data are shown as the mean ± SEM, n = 3 per experimental group. *P ≤ 0.05, Student’s t test.