Interaction of long noncoding RNAs and microRNAs in the pathogenesis of idiopathic pulmonary fibrosis

Long noncoding RNAs (lncRNAs) are transcribed RNAs with more than 200 nucleotides in length. A growing body of evidence supports the notion that lncRNAs act as competitive endogenous RNAs for microRNAs and play roles in physiological and pathological processes. Several studies have demonstrated the roles of microRNAs in the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, it is unknown whether lncRNAs are involved in IPF. To investigate the roles of lncRNAs in IPF, we determined the interaction of lncRNAs and microRNAs by motif search and manual comparison. The sequences of the dysregulated microRNAs in IPF including miR-21, miR-31, miR-101, miR-29, miR-199, and let-7d were used to search NONCODE database containing 33,829 human lncRNAs. A total of 34 lncRNAs with potential binding sites to these microRNAs were identified. We then examined the expression levels of the identified lncRNAs in the lungs of IPF patients by real-time PCR. Of 34 lncRNAs, nine lncRNAs were dysregulated in the IPF lungs. Four of them were inversely correlated to the microRNA expression in IPF. Further studies revealed that silencing the lncRNA CD99 molecule pseudogene 1 (CD99P1) inhibited proliferation and α-smooth muscle actin expression of lung fibroblasts, while knockdown of the lncRNA n341773 increased collagen expression in lung fibroblasts. These results suggest that CD99P1 and n341773 may be involved in the regulation of lung fibroblast proliferation and differentiation. The identification of regulatory functions of lncRNAs in lung fibroblasts may provide new research directions for the therapy of IPF.