1.    INTRODUCTION
Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in infants born prematurely.1,2 Although the underlying pathogenesis is not fully understood, pulmonary inflammation is now considered to be the common signal pathway in lung and the main clinicopathological characteristic in BPD.3,4
MicroRNAs (miRNAs), small non-coding RNAs, which are involved in various biological processes, including tumorigenesis, inflammation, and immune regulation.1,5,6. Using newborn mouse models, we previously demonstrated that miRNAs are associated with lung development and that altered miRNA levels contribute to the development of BPD.1
With the development of gene expression profiles, comparisons of differentially expressed mRNAs or miRNAs have been carried out in many diseases including BPD.1,7-9 Although microarray technologies are convenient, most studies focus on a single cohort study, and different studies report contrasting results. Integrated advanced bioinformatics methods may offer a way to overcome these disadvantages and elucidate the molecular mechanism involved in BPD.
In the present study, we used mRNA and miRNA microarrays to assess differential expression profiles in BPD and control lung tissues.
Bioinformatics methods including Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses for differentially expressed genes, and protein-protein interaction (PPI) network and miRNA-mRNA regulatory network construction were performed to analyze the key genes and pathways associated with inflammation and immune regulation. These data would provide novel insights into the development of new promising biomarkers for the treatment of BPD.
2.1 Animal model
The experimental BPD mouse model was induced as we previously described.1 Briefly, newborn Kunming mice (the Chinese Academy of Sciences Beijing, China) were randomly assigned to room air and oxygen exposure (FiO2= 60% for 21days) beginning at birth (n=15 each group).1 Animals were euthanized with intraperitoneal sodium pentobarbital after exposure on postnatal day 2 (P2), P7, and P21(n=5 each) and lung tissues were stored in liquid nitrogen.1 All experiments involving animals were approved by the Animal Care and Use Committee of The General Military Hospital of Beijing PLA, Beijing, China.