THBS1 and preeclampsia: For a day 30 equine conceptus heading to placentation, paradoxically, TGFBI (Transforming Growth Factor Beta Induced) known as a negative factor for cell attachment (Skonier et al., 1994), and THBS1 (Thrombospondin-1), which can inhibit syncytiotrophoblast formation to trigger preeclampsia during placentation in human (Duan et al., 2021), is highly expressed in its VC (Figure 3E).