Figure 2: MagBICE₁ targets injured myocardium and recruits endogenous cells in vivo.

(a) Schematic of in vivo targeting experiment in rats with ischemia/injury injury. (b) T₂* weighted MRI images showing the specific targeting of MagBICE₁ to injured myocardium. The presence of iron-created signal void (dark area; pointed with yellow arrows). The images were inverted so the signal void (dark area) from the iron signal led to higher value of ‘hypointensity’. The iron signal intensity of the heart anterior wall was quantified and normalized to adjacent tissue (P=0.0015; n=3 animals). *P<0.05 when compared with control. (c) Confocal microscopic images showing the co-localization of MagBICE₁ (green) with cardiomyocytes (red) in the infarct area. The binding of MagBICE₁ to healthy myocytes in the non-infarcted (remote) area was negligible (P<0.0001; n=3 animals and 6 microscopic fields). *P<0.05 when compared with FH-infarct. (d) Confocal microscopic images showing MagBICE₁ recruited endogenous CD45-positive cells (green) to the infarct area (P<0.0001; n=3 animals and 27 microscopic fields). *P<0.05. (e) Confocal microscopic images showing CD68-positive macrophages (magenta) in the infarct area. MagBICE₁ was detected by anti-rabbit FITC secondary antibodies (green). Most macrophages were MagBICE₁-free (yellow arrows) but a few macrophages had endocytosized MagBICE₁ (white arrow). MagBICE₁ infusion did not increase the number of macrophages in the post-MI heart (P=0.5596; n=3 animals and 27 microscopic fields). All data are mean±s.d. Comparisons between any two groups were performed using two-tailed unpaired Student’s t-test. Comparisons among more than two groups were performed using one-way ANOVA followed by post-hoc Bonferroni test. DAPI, 4′,6-diamidino-2-phenylindole.