The enzyme heme oxygenase-1 (HO-1) is pivotal in reproductive processes, particularly in placental and vascular development. This study investigated the role of HO-1 and its byproduct, carbon monoxide (CO), in trophoblastic spheroid implantation. In order to deepen our understanding of the role of HO-1 during implantation, we conducted in vivo experiments on virgin and pregnant mice, aiming to unravel the cellular and molecular mechanisms. Using siRNA, HO-1 was knocked down in JEG-3 and BeWo cells and trophoblastic spheroids were generated with or without CO treatment. Adhesion assays were performed after transferring the spheroids to RL-95 endometrial epithelial cell layers. Additionally, angiogenesis, stress, and toxicity RT2-Profiler™ PCR SuperArray and PCR analyses were performed in uterine murine samples. HO-1 knockdown by siRNA impeded implantation in the 3D culture model, but this effect could be reversed by CO. Uteruses from virgin Hmox1-/- females exhibited altered expression of angiogenesis and stress markers. Furthermore, there was a distinct expression pattern of cytokines and chemokines in uteruses from gestation day 14 in Hmox1-/- females compared to Hmox1+/+ females. This study strongly supports the essential role of HO-1 during implantation. Moreover, CO appears to have the potential to compensate for the lack of HO-1 during the spheroid attachment process. The absence of HO-1 results in dysregulation of angiogenesis and stress-related genes in the uterus, possibly contributing to implantation failure.
Keywords: angiogenesis; heme oxygenase-1; implantation; pregnancy.