Changes in microRNA and mRNA expression with differentiation of human bronchial epithelial cells [miRNA]

Normal human bronchial epithelial (NHBE) cells cultured in an air-liquid interface (ALI) system form a polarized, pseudostratified epithelium composed of basal, ciliated and goblet cells that closely resemble the in vivo airway epithelium structure. ALI cultures of NHBE cells provide a unique in vitro system to investigate airway epithelial biology, including developmental, structural and physiologic aspects. MicroRNAs (miRNAs) are short, single-stranded, non-coding RNAs of 20-23 nucleotides that down-regulate gene expression by either inducing degradation of target mRNAs or impairing their translation. They are phylogenetically well conserved, which probably implies an important role of miRNAs in biological processes. In this way, we wanted to shed some light on miRNA specific roles and the relationship with their mRNA targets during airway epithelium differentiation. By using microarrays, we studied the changes in expression of microRNAs in normal human bronchial epithelial cells as they differentiate from an undifferentiated monolayer to a differentiated pseudostratified epithelium after 28 days of air-liquid interface (ALI) culture, when epithelial cells differentially express basal, ciliated and goblet cell markers. Normal human bronchial epithelial cells were cultured in an air-liquid interface (ALI) system and harvested at three different time-points: subconfluent, confluent and day 28 of ALI. Samples were processed for total RNA (including small RNAs) extraction and hybridization on Affymetrix microarrays. All the experiments were performed by triplicate.