Advances in understanding canine pregnancy: Endocrine and morpho-functional regulation.

Canine pregnancy relies on luteal steroidogenesis for progesterone (P4) production. The canine placenta responds to P4, depending on the nuclear P4 receptor (PGR). This has sparked interest in investigating the interaction between ovarian luteal steroids and the placenta in dogs. Canine placentation is characterized by restricted (shallow) trophoblast invasion, making the dog an interesting model for studying decidua-derived modulation of trophoblast invasion, compared with the more invasive (hemochorial) placentation. The PGR is expressed in maternally derived decidual cells and plays a crucial role in feto-maternal communication during pregnancy maintenance. Understanding PGR-mediated signalling has clinical implications for improving reproductive performance control in dogs. Altering the PGR signalling induces the release of PGF2α from the foetal trophoblast, hindering placental homeostasis, which can also be achieved with antigestagens like aglepristone. Consequently, luteolysis, both natural and antigestagen-induced, involves apoptosis, vascular lesion, and immune cell infiltration in the placenta, resulting in placentolysis and foetal membranes expulsion. Our laboratory developed the immortalized dog uterine stromal (DUS) cell line to study canine-specific decidualization. We study canine reproduction by observing physiological processes and investigating evidence-based mechanisms of decidualization and feto-maternal interaction. Our focus on morphology, function and molecular aspects enhances understanding and enables targeted and translational studies.