Figure 5.

Cardiac fibroblasts interact with cardiomyocytes through gap junctions to share free iron

(A and B) Wild-type mouse heart tissue stained for Fth1 [magenta, (A)] or Ftl [magenta, (B)], with cTnT (green) and DAPI (blue) at 1DPMI after P7 LAD-O. Arrows: non-cardiomyocytes positive for Fth1 (A) or Ftl (B).

(C and D) Mouse heart tissue stained for Fth1 [red, (C)] or Ftl [red, (D)], with Pdgfrα (gray), cTnT (green), and DAPI (blue) at 1 DPMI after P7 LAD-O. Arrows: cells positive for Pdgfrα and Fth1 (C) or Ftl (D).

(E and F) Mouse heart tissue stained for Fth1 [green, (E)] or Ftl [green, (F)], with Pdgfrα (red), MF20 (gray), and DAPI (blue) at 6 DPMI after P7 LAD-O. Arrows: cells positive for Pdgfrα and Fth1 (E) or Ftl (F).

(G) Diagram of cardiomyocyte-fibroblast interaction after MI.

(H and I) Mouse heart section stained for Cx45 [green, (H)] or Cx43 [green, (I)], with Pdgfrα (red), MF20 (gray), and DAPI (blue) after P7 LAD-O. Arrows: potential locations of gap junctions between cardiomyocytes and fibroblasts.

(J–L) Co-cultured iCM and HCF stained for VIMENTIN (VIM, gray), free Fe²⁺ (red), DAPI (blue), and imaged with TITIN-GFP (green) after DMSO (J) or erastin (15 μM) (K, L) treatment. Asterisks: HCFs with accumulation of Fe²⁺.

(M) siRNA knockdown of CX43 and CX45 simultaneously in iCM-HCF co-culture; Fe²⁺ fluorescent intensity ratio of iCMs over HCFs was quantified after erastin or DMSO treatment. LV, left ventricle. All bar graphs represent mean ± SD. ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001 by t test. Scale bar, 75 μm (A, B, E, F, H), 25 μm (C, D, I, J–L). See also Figures S4 and S5.