Fig 2: Histological analysis of rhACE2 patch effect on MI-induced cardiac remodeling.H&E stained section (a), Masson’s trichrome staining (b) and Sirius Red staining (c) of mice hearts at low magnification after heart was obtained 28 days after MI. Scale bars represented 500 μm. d Brain natriuretic peptide (BNP) immunohistochemical staining of hearts from PLLA, intramyocardial injection (IM) and PLLA-HA/ACE2 treatment group 28 days after MI. Scale bars represented 40 μm. Morphometric parameters including the percentage of infarct size percentage of total LV area (e) and the percentage of infarcted thickness of LV anterior wall (f) were measured from the Sirius Red stained slides via ImageJ software. n = 5/group. g The integrated optical density (IOD)/area ratios of BNP were quantified from the immunohistochemical stain by Image-Pro Plus software. n = 5/group. Data were represented as the mean ± SEM and was analyzed for statistical significance using one-way ANOVA followed by Tukey’s multiple comparison test; NS no significant difference, *P < 0.05, ****P < 0.0001.

Fig 3: rhACE2 patch sustained-release activity test.a In vitro releasing curve of PLLA-HA/ACE2 fibrous membranes. b Releasing buffer collected at specified time points during release study was added into culture media of NRCMs undergone 6 h hypoxia. Representative immunofluorescence image of TUNEL (red) and nuclear visualized by DAPI (blue). Scale bars represented 50 μm. c Statistical analysis of TUNEL-positive cell counts. n = 3/group. Data were represented as the mean ± SEM and analyzed for statistical significance using One-way ANOVA followed by Tukey’s multiple comparison test; NS no significant difference; **P < 0.01 compared to the control group.

Fig 4: Biocompatibility tests in vitro.a Representative live/dead fluorescence stained by Calcein AM (green) and Propidium Iodide (red) at day 3. Scale bars represented 50 and 20 μm for zoomed pictures. b Live and dead cell count per HPF of control, PLLA, PLLA-HA/ACE2 groups. n = 4/group. c CCK-8 cell viability quantification results in different groups after 1, 2, or 3 days. n = 4/group. Data were represented as the mean ± SEM and analyzed for statistical significance using One-way ANOVA followed by Tukey’s multiple comparison test; NS no significant difference.

Fig 5: rhACE2 patch preserve left ventricular function after acute myocardial infarction in vivo.a The animal research timeline design with images represented the acute MI model and successful implantation of rhACE2 patch. Echo, echocardiography. b Representative M-mode parasternal long axis view of left ventricle echocardiographic images of different groups at day 28 after LAD coronary artery ligation. Statistical analysis of left ventricular ejection fraction (c), shortening fraction (d), heart weight/body weight ratio (e), LV end-diastolic diameter (f), LV end-systolic diameter (g) and heart weight/tibial length (h) determined by echocardiography obtained from PLLA, intramyocardial injection (IM) and PLLA-HA/ACE2 treatment group at day 7, day 14 and day 28 after operation. n = 5/group. Data were represented as the mean ± SEM and analyzed for statistical significance using two-way ANOVA followed by Tukey’s multiple comparison test; NS no significant difference, *P < 0.05, **P < 0.01.