Wnt7b/beta-catenin signaling pathway mediated by retinoid acid involved in the transdifferentiation of primary fetal alveolar epithelial type II cells

This study was designed to investigate the roles of retinoic acid (RA) in transdifferentiation of primary fetal alveolar epithelial type II cells (AECIIs) into alveolar epithelial type I cells (AECIs). Primary fetal AECIIs isolated from rats at a gestational of 19 days were divided into: (i) DMSO group treated using 0.1% DMSO; (ii) RA group, treated with 1 mu M RA; and (iii) RA+BMS493 group treated with 1 mu M RA and 10(-8) M BMS493 (served as a pan-RA receptor antagonist). Then we determined the roles of AQP5 (a specific marker of AECIs), SP-C (a specific marker for AECIIs) and Wnt7b/beta-catenin signaling pathway in the transdifferentiation of AECIIs to AECIs. SP-C mRNA and protein expression was significantly down-regulated in AECIIs exposure to RA for 24 h and 48 h, however, significant up-regulation was noticed after exposure for 72 h. AQP5 mRNA and protein expression showed significant increase in RA group, but showed significant decline in the RA+BMS493 group. Wnt7b mRNA, nucleus beta-catenin and cyclin D1 were significantly up-regulated in RA group compared with DMSO group. RA may promote fetal AECIIs transdifferentiation into AECIs through activating Wnt7b/beta-catenin signaling pathway. Our study contributed to the understanding on the pulmonary regeneration in cases of pulmonary injuries, together with the prevention and treatment of neonatal respiratory distress syndrome.