P46 Studies on the bivalent interaction of IGF-II with the insulin and type 1 IGF receptors

Abstract

demonstrated the role of the IGF system in the regulation of trophoblast proliferation and survival and alterations in the IGF ligands or the receptors could have implications in the pathogenesis of trophoblastic diseases. The aim of this study was to investigate the role of the IGF system in trophoblast cell differentiation by evaluating the expression of genes of the IGF system during the process. We utilized the HTR8/Svneo extra villous trophoblast cell line and induced differentiation by stimulation with forskolin (FSK), an agonist of adenylyl cyclase, We found that cells treated with FSK 25mM for 72 hours secreted high levels of chorionic gonadotropin (hCG), a common differentiation marker of syncitiotrophoblast. Interestingly we found a hCG related increase in IGF-II and IGF-IIR mRNAs expression, suggesting an important role of this growth factor and its receptor during differentiation. To investigate the potential role of an autocrine IGF-II/IGF-IIR loop we obtained a stable IGF-IIR silenced HTR8/Svneo cell line by shRNA tranfection and induced differentiation aspreviously. After 72 hours of treatment with FSK we found a marked reduction in IGF-II mRNA levels, in comparison with the non-silenced cell line, together with a decrease in the expression in the IGF-I and Insulin receptors. In addition we observed a direct relation between IGF-IIR silencing with a delayed kinetic pattern of differentiation. In conclusion this study presents a first approximation to the autocrine role of IGFII/IGF-IIR system in trophoblastic cell differentiation.