Cardiopulmonary bypass reduces myocardial oxidative stress, inflammation and increases c-kit(+)CD45(-) cell population in newborns.

BACKGROUND: The aim of this study was to characterize the influence of cardiopulmonary bypass (CPB) on myocardial remodeling in newborns and children. METHODS: Biopsies from the right atrium were taken before and after CPB from 4 newborns (5-11 days old) and 7 children (8 months-16 years old). Immunostainings on 10 µm heart tissue frozen sections were performed to detect c-kit(+) cells, leukocytes (CD45(+) cells), Ki67(+) cycling cells. The percentage of 8-hydroxy-guanosine (8-dOHG)(+)cardiomyocytes and non-cardiomyocytes [(8-dOHG)(+)-index] were determined to quantify oxidative stress. RESULTS: Δ c-kit(+)CD45(-) cells (resident cardiac stem cells) were increased in newborns (2.2 ± 1.9/mm(2)) and decreased in children - 1.5 ± 0.7/mm(2), p < 0.01. The (8-dOHG)(+)-index was reduced by 43% in newborns and by 20% in children. CPB did not influence cardiac cell turnover; high cell proliferation was seen in newborns before and after CPB. Cardiopulmonary bypass significantly decreased the leucocyte infiltration in newborns to 40 ± 8%, p < 0.05, but not in children. Infiltration with eosinophils (eosinophils/CD45%) was completely abolished in the myocardium of newborns p < 0.05 and reduced to 22 ± 8% in children after CPB, n.s. CONCLUSIONS: Immediate response and remodeling of the myocardium to CPB differs between newborns, older infants and children. Especially an increased number of c-kit expressing CD45 cells after CPB were seen in neonates in comparison to children. The clinical value of such observation needs to be further assessed in larger cohorts of patients.