Evidence for Imbalanced Polarization of Caruncle Macrophages in Retained Placenta of Dairy Cows

Macrophages at the maternal-fetal interface exhibit remarkable plasticity and polarization, playing a crucial role in placental expulsion by regulating the clearance of apoptotic cells and extracellular matrix remodeling. In the present study, we observed increased collagen deposition and reduced apoptosis at the maternal-fetal interface in the placental tissue collectedfrom retained placenta (RP) cows within 30 minutes postpartum. Additionally, we found a reduced population of caruncle macrophages in RP cows, with a predominance of M2-polarized macrophages. These findings suggest that the imbalance of M1/M2 macrophage ratio may contribute to abnormal collagen deposition and impaired cell death at the interface, leading to the occurrence of RP.