Abstract P309: Aberrant Corin and PCSK6 in the Placenta of Hyperinsulinemic Dams

Abstract

Introduction: Corin, a serine protease converts pro-atrial natriuretic peptide (pro-ANP) and pro-brain natriuretic peptide (pro-BNP) to the mature respective peptides. There is evidence that the pregnant uterus produces ANP, where it promotes spiral artery remodelling, essential for adequate blood supply to the developing conceptus. Aim: Here we examine corin and PCSK6, a key enzyme in the conversion of pro-corin to corin, in the placenta of hyperinsulinemic dams (HD) in comparison to normal pregnant dams (NPD). Materials and Methods: Female Wistar rats were rendered hyperinsulinemic by subcutaneous insulin pellet, mated and followed to day 21 of pregnancy. Both groups were then sacrificed and their placentas were dissected together with the implantation site designated mesometrial triangle (MT). Placentas and MT were sectioned from the maternal through the fetal surface to the base of the MT. For western blot (WB) the placentas and MT were separated, snap frozen in liquid nitrogen and stored at –80°C. RNA expression of corin was carried out by in-situ hybridization in 5 NPD and 6 HD with corin probe (RNAscope® Assay 2.5 Detection Reagent, Cat No. 507231) and image analysis was performed. Results: As previously described, HD (n=20) developed hypertension as compared with in NPD (n=16). Moreover, HD exhibited lower placental and foetal weights. Corin and PCSK6 mRNA and immunoreactive peptide were detected in the mesometrial tissues. Corin abundance as determined by western blot was significantly decreased in the placenta/ mesometrial triangle by ~40% (P<0.02), as was PCSK6 immunoreactivity. Corin and PCSK6 mRNAs displayed similar pattern of alterations as protein abundance, where in-situ hybridization for corin mRNA revealed a 50% (P<0.001) expression reduction. Corin mRNA was specifically expressed by cytotrophoblasts in the labyrinth. Concomitant with the downregulation of corin/PCSK6, ANP levels decreased in the MT of HD. Summary and Conclusion: Corin, PCSK6 and ANP are all expressed in the placenta of NPD but declined in dams with chronic hyperinsulinemia, suggesting a role of corin/PCSK6 pathway in the prevention of pregnancy-induced hypertension and intrauterine growth restriction, in this setting.