Background Cyanotic congenital heart defects with decreased pulmonary blood flow due to lung ischemia,hypoxia,and others lead to infant morbidity and mortality more than acyanotic heart disease does.Despite the great effort of medical research,their genetic link and underlying microRNAs molecular mechanisms remain obscure.In this study,we aimed to investigate microRNAs regulation during cyanotic defects in lung of immature piglets.Methods Cyanotic piglet model was induced by main pulmonary artery-left atrium shunt with distal pulmonary artery banding.Four weeks later,hemodynamic parameters confirmed the development of cyanotic defects and pulmonary lobe RNA was extracted from all animals.We studied the repertoire of porcine lung microRNAs by Solexa deep sequencing technology and quantified highly expressed microRNAs by microarray hybridization.Furthermore,we quantitated selected microRNAs from cyanotic and control piglets by quantitative RT-PCR.Results After surgical procedure 4 weeks later,the cyanotic model produced lower arterial oxygen tension,arterial oxygen saturation,and higher arterial carbon dioxide tension,hematocrit and hemoglobin concentration than controls (all P ＜0.05).In 1273 miRNAs expressed in the immature piglets lungs,2 most abundant microRNAs (miR-370 and miR-320) demonstrated significant difference between cyanotic and control group (all P ＜0.05).Conclusion Our results extended lung microRNA profile in immature piglets and suggested that miR-370 and miR-320 are significantly up-regulated in cyanotic lung tissues.