Fig 2: CD44 mediates cardiac ischemic angiogenesis in vivo. A Representative images of infarcted myocardium in CD44 WT and KO mice post 1 week MI, double-stained by Evans Blue and TTC. The black dotted line shows the area of myocardial infarction (white). The white dotted line shows the area of Evans Blue and TTC staining in LV (Blue + Red). Scale bar: 1 mm. B The percentages of area at risk (AAR) per left ventricle (LV), infarcted zone (IZ) per AAR, and IZ per LV in WTMI (n = 5) and KOMI mice (n = 6). C Representative results of Masson’s trichrome staining of heart sections from ligation to apex in the WTMI (n = 7) and KOMI (n = 8) groups. Scale bar: 1 mm. D Quantitative analysis of infarct size and infarct wall thickness. E Heart tissues were immunofluorescently stained for CD31 (endothelial marker, red), DAPI (nuclei, blue), and cTnT (green) and photographed by confocal microscopy. Scale bar: 100 µm (left panel); 10 µm (middle; right panels). F The statistical data of the density of blood vessels in the WTMI (n = 5) and KOMI (n = 7) groups. G Representative images of TUNEL (red) and CD31 (green) costaining of WTMI and KOMI mice hearts. White arrowheads denote the CD31-positive TUNEL-positive cells in cardiac border zone. Scale bar: 25 µm. H Immunofluorescence results of CD31 (red) staining in Matrigel plugs. Scale bar: 50 µm (right panel). DAPI (blue) labeled cell nuclei. Representative morphology of the Matrigel plugs in CD44 WT (a, n = 5) and KO (b, n = 5) mice. Scale bar: 2 mm (left panel). I The statistical data of CD31 relative fluorescence intensity in the WT and KO groups. *P < 0.05, ***P < 0.001, ns no significance. Epi, epicardium; Endo, endocardium; LV, left ventricular

Fig 3: CD44 regulates cardiac remodeling and cardiac function in the early stage of MI. A CD44 is highly expressed in the heart in the early stage of MI. Representative confocal microscopy images of CD44 (red) expressed in cardiac border zone (c, f) and infarct zone (d, e) in 1-week MI mouse hearts and normal hearts (a, b). DAPI (blue) stained nuclei and cTnT (green) labeled cardiomyocytes. Scale bars: 400 µm (upper panel); 100 µm (lower panel). B The statistical data of CD44 relative fluorescence intensity in normal hearts (Sham), infarct zone (MI-I), border zone (MI-B), and remote area (MI-B) in MI mouse hearts. n = 3. C Schematic illustration of the mouse MI experiment. D The echocardiography results of the WTSham, KOSham, WTMI, and KOMI groups 1 week post-MI. LVIDd, left ventricular internal dimension at end-diastole; LVIDs, left ventricular internal dimension at end-systole. E The statistical data of left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular end-diastolic volume (LVEDV), and left ventricular end-systolic volume (LVESV) of WTSham (n = 10), KOSham (n = 11), WTMI (n = 24), and KOMI (n = 19) groups. *P < 0.05, **P < 0.01, ***P < 0.001, ns no significance. Echo, echocardiography