Galectins are proteins that bind to glycans in targeted cells and function in cell-to-cell signaling throughout the body. Galectins have been found to be involved in various reproductive processes, including placental dysfunction, but this has not been investigated in the horse. Therefore, the objective of this study was to assess alterations in galectin expression of the abnormal placenta in pregnant mares. Next-generation RNA sequencing was performed on the postpartum chorioallantois of two placental pathologies following clinical cases of ascending placentitis (n = 7) and focal mucoid placentitis (n = 4), while chorioallantois from healthy postpartum pregnancies (n = 8; 4 control samples per disease group) served as the control. When evaluating ascending placentitis, both galectin-1 (p < 0.001) and galectin-3BP (p = 0.05) increased in the postpartum chorioallantois associated with disease, while galectin-8 (p < 0.0001) and galectin-12 (p < 0.01) decreased in the diseased chorioallantois in comparison with those in the control. In mares with focal mucoid placentitis, numerous galectins increased in the diseased chorioallantois, and this included galectin-1 (p < 0.01), galectin-3BP (p = 0.03), galectin-9 (p = 0.02), and galectin-12 (p = 0.04), in addition to a trend toward increases in galectin-3 (p = 0.08) and galectin-13 (p = 0.09). In contrast, galectin-8 expression decreased (p = 0.04) in the diseased chorioallantois in comparison with that of the controls. In conclusion, galectins alter in abnormal placentae with variations observed among two forms of placental pathologies. These cytokine-like proteins may further our understanding of placental pathophysiology and warrant attention as potential markers of placental inflammation and dysfunction in the horse.
Keywords: chorioallantois; equine; galectin; placentitis.