Figure 4.

Hypoxia-primed monocytes/macrophages promote postinfarction myocardial repair in vivo. (A) Schematic protocol of intramyocardial injection. The animals were monitored for 28 days. (B) Representative laser confocal microscopy images of M_N- and M_H-polarized macrophages. Scale bar: 50 μm. (C) Cumulative survival curve (Kaplan-Meier survival plot) of MI mice after macrophage transplantation and sham-operated mice (n = 46 for MI followed by M_N macrophage transfer, n = 36 for MI followed by M_H macrophage transfer, n = 20 for MI followed by vehicle transfer, and n = 10 for sham-operated mice). (D) The heart weight-to-body weight (HW/BW) ratio was significantly decreased in the MI mice following the M_H macrophage transfer. (E) Left ventricular ejection fraction (LVEF), fractional shortening (LVFS), left ventricular internal diameter at end-systole (LVID, s) and left ventricular volume at end-systole (LV, Vol, s) were measured by echocardiography and are presented. (F) Trichrome staining of longitudinal sections showed enlarged hearts after MI. Scale bar: 1 mm. (G) Quantification of the fibrotic area and LV thickness relative to the myocardium in transverse sections demonstrated a significant decrease in scar formation in the hypoxia-treated MI mice and an increase in scar formation in the hyperoxia-treated mice. (H) Representative images of infarct areas stained with picrosirius red visualized under polarized light. Scale bar: 100 μm. (I) Quantification of picrosirius red polarized light analysis in the infarct areas of MI mice. Dot-plots represent data from individual mice. Statistical significance was determined by a log-rank test (C), two-way ANOVA followed by Sidak's multiple comparisons test (D, E, G) or Kruskal-Wallis test followed by Dunn's posttest to correct for multiple comparisons (G). *P < 0.05, **P < 0.01 and ***P < 0.001 compared to the corresponding control.