Endothelial colony-forming cell therapy for heart morphological changes after neonatal high oxygen exposure in rats, a model of complications of prematurity

Abstract

Very preterm birth is associated with increased cardiovascular diseases and changes in myocardial structure. The current study aimed to investigate the impact of endothelial colony-forming cell (ECFC) treatment on heart morphological changes in the experimental model of neonatal high oxygen (O₂ )-induced cardiomyopathy, mimicking prematurity-related conditions. Sprague-Dawley rat pups exposed to 95% O₂ or room air (RA) from day 4 (P4) to day 14 (P14) were randomized to receive (jugular vein) exogenous human cord blood ECFC or vehicle at P14 (n = 5 RA-vehicle, n = 8 RA-ECFC, n = 8 O₂ -vehicle and n = 7 O₂ -ECFC) and the hearts collected at P28. Body and heart weights and heart to body weight ratio did not differ between groups. ECFC treatment prevented the increase in cardiomyocyte surface area in both the left (LV) and right (RV) ventricles of the O₂ group (O₂ -ECFC vs. O₂ -vehicle LV: 121 ± 13 vs. 179 ± 21 μm² , RV: 118 ± 12 vs. 169 ± 21 μm² ). In O₂ rats, ECFC treatment was also associated with a significant reduction in interstitial fibrosis in both ventricles (O₂ -ECFC vs. O₂ -vehicle LV: 1.07 ± 0.47 vs. 1.68 ± 0.41% of surface area, RV: 1.01 ± 0.74 vs. 1.77 ± 0.67%) and in perivascular fibrosis in the LV (2.29 ± 0.47 vs. 3.85 ± 1.23%) but in not the RV (1.95 ± 0.95 vs. 2.74 ± 1.14), and with increased expression of angiogenesis marker CD31. ECFC treatment had no effect on cardiomyocyte surface area or on tissue fibrosis of RA rats. Human cord blood ECFC treatment prevented cardiomyocyte hypertrophy and myocardial and perivascular fibrosis observed after neonatal high O₂ exposure. ECFC could constitute a new regenerative therapy against cardiac sequelae caused by deleterious conditions of prematurity.

Keywords: Cell therapy; heart; oxygen-induced cardiomyopathy; preterm birth.

Figure 1

Effect of ECFC treatment on left and right ventricle cardiomyocyte hypertrophy. (A) Left ventricle and (B) right ventricle cardiomyocytes surface area (μm²) of 28 days old rats exposed to high concentration of oxygen (O₂) versus room air (RA) in the neonatal period and subsequently treated with endothelial colony‐forming cells (ECFC) versus saline (Control). (C) Representative photomicrographs of LV cardiomyocytes stained with hematoxylin‐eosin. Magnification of X400; scale bar, 50 μm. *P < 0.05 versus all other groups.

Figure 2

Effect of ECFC treatment on the left and right ventricle interstitial and perivascular fibrosis. (A) Left ventricle and (B) right ventricle interstitial tissue fibrosis (% total pixels) and (C) Left ventricle and (D) right ventricle perivascular fibrosis (% total pixels) of 28 days old rats exposed to high concentration of oxygen (O₂) versus room air (RA) in the neonatal period and subsequently treated with endothelial colony‐forming cells (ECFC) versus saline (Control). (E) Representative photomicrographs of LV myocardium and (F) LV myocardium vessel stained with Masson's trichrome. Magnification of X400; scale bar, 50 μm. *P < 0.05.

Figure 3

Effect of ECFC treatment on expression of angiogenesis marker CD31 (PECAM‐1) in left and right ventricle. (A) Immunofluorescence showing left ventricle and (B) right ventricle CD31 expression (RFU/μm²: relative fluorescence unit) and (C) Left ventricle and (D) right ventricle perivascular CD31 expression of 28 days old rats exposed to high concentration of oxygen (O₂) versus room air (RA) and subsequently treated with endothelial colony‐forming cells (ECFC) versus saline (Control). (E) Representative photomicrographs of LV myocardium and (F) LV perivascular CD31 immunoflorescence. Magnification of X400; scale bar, 50 μm. *P < 0.05; P = 0.08 O₂‐ECFC versus O₂‐Control in LV.