The syncytiotrophoblast, a fused single-cell layer between mother and fetus, constitutively releases extracellular vesicles (STBEV) directly into the maternal circulation. STBEV contain a variety of proteins and RNA which can be targeted to specific cells. In preeclampsia, asymptomatic placental oxidative stress is a precursor to later multi-organ dysfunction in the mother. Increased STBEV release in preeclampsia is considered a manifestation of syncytiotrophoblast stress, which may play a key role in signaling between fetus and mother. STBEV release in preeclampsia changes, both in terms of volume and content. In this review, we outline the latest advances in STBEV isolation and detection. We consider evidence for differential STBEV release, protein cargo and RNA content in preeclampsia, highlighting common pitfalls in study design. We summarise studies to date demonstrating STBEV actions on target cells. Ultimately, we consider how STBEV fit into the pathophysiology of the heterogeneous syndrome of preeclampsia. The key unifying concept in early- and late-onset preeclampsia is syncytiotrophoblast stress. We submit that STBEV are the key stress signal in preeclampsia. We believe that further investigation of STBEV release, content, and actions may offer valuable insights into preeclampsia pathophysiology and potential new clinical diagnostics and therapeutic targets.

The syncytiotrophoblast, a fused single-cell layer between mother and fetus, constitutively releases extracellular vesicles (STBEV) directly into the maternal circulation. STBEV contain a variety of proteins and RNA which can be targeted to specific cells. In preeclampsia, asymptomatic placental oxidative stress is a precursor to later multi-organ dysfunction in the mother. Increased STBEV release in preeclampsia is considered a manifestation of syncytiotrophoblast stress, which may play a key role in signaling between fetus and mother. STBEV release in preeclampsia changes, both in terms of volume and content. In this review, we outline the latest advances in STBEV isolation and detection. We consider evidence for differential STBEV release, protein cargo and RNA content in preeclampsia, highlighting common pitfalls in study design. We summarise studies to date demonstrating STBEV actions on target cells. Ultimately, we consider how STBEV fit into the pathophysiology of the heterogeneous syndrome of preeclampsia. The key unifying concept in early- and late-onset preeclampsia is syncytiotrophoblast stress. We submit that STBEV are the key stress signal in preeclampsia. We believe that further investigation of STBEV release, content, and actions may offer valuable insights into preeclampsia pathophysiology and potential new clinical diagnostics and therapeutic targets.