Normotensive placental extracellular vesicles provide long-term protection against hypertension and cardiovascular disease.

BACKGROUND: Women with normotensive pregnancy are at a reduced risk of developing cardiovascular disease postpartum compared with those who experience hypertensive conditions during pregnancy. However, the underlying mechanisms remain poorly understood. During normotensive pregnancy, vast numbers of placental extracellular vesicles are released into the maternal circulation, which protect endothelial cells from activation and alter maternal vascular tone. We hypothesized that placental extracellular vesicles play a mechanistic role in lowering the risk of cardiovascular disease following normotensive pregnancy. OBJECTIVE: This study aimed to investigate the long-term effects of placental extracellular vesicles derived from normotensive term placentae on the cardiovascular system and explore the mechanisms underlying their biological effects. STUDY DESIGN: Spontaneously hypertensive rats were injected with placental extracellular vesicles from normotensive term pregnancies (2 mg/kg each time, n=8) or vehicle control (n=9) at 3 months of age. Blood pressure and cardiac function were regularly monitored from 3 months to 15 months of age. The response of mesenteric resistance arteries to vasoactive substances was investigated to evaluate vascular function. Cardiac remodeling, small artery remodeling, and renal function were investigated to comprehensively assess the impact of placental extracellular vesicles on cardiovascular and renal health. RESULTS: Compared with vehicle-treated control animals, rats treated with normotensive placental extracellular vesicles exhibited a significantly lower increase in blood pressure and improved cardiac function. Furthermore, the vasodilator response to the endothelium-dependent agonist acetylcholine was significantly enhanced in the normotensive placental extracellular vesicle-treated spontaneously hypertensive rats compared with the control. Moreover, treatment with placental extracellular vesicles reduced wall thickening of small renal vessels and attenuated renal fibrosis. CONCLUSION: Placental extracellular vesicles from normotensive term pregnancies have long-lasting protective effects reducing hypertension and mitigating cardiovascular damage in vivo.

Extracellular vesicles and their effect on vascular haemodynamics: a systematic review.

Extracellular vesicles (EVs) are released from all cell types studied to date and act as intercellular communicators containing proteins, nucleic acids and lipid cargos. They have been shown to be involved in maintaining homoeostasis as well as playing a role in the development of pathology including hypertension and cardiovascular disease. It is estimated that there is 109-1010 circulating EVs/mL in the plasma of healthy individuals derived from various sources. While the effect of EVs on vascular haemodynamic parameters will be dependent on the details of the model studied, we systematically searched and summarized current literature to find patterns in how exogenously injected EVs affected vascular haemodynamics. Under homoeostatic conditions, evidence from wire and pressure myography data demonstrate that injecting isolated EVs derived from cell types found in blood and blood vessels resulted in the impairment of vasodilation in blood vessels ex vivo. Impaired vasodilation was also observed in rodents receiving intravenous injections of human plasma EVs from cardiovascular diseases including valvular heart disease, acute coronary syndrome, myocardial infarction and end stage renal disease. When EVs were derived from models of metabolic syndromes, such as diabetes, these EVs enhanced vasoconstriction responses in blood vessels ex vivo. There were fewer publications that assessed the effect of EVs in anaesthetised or conscious animals to confirm whether effects on the vasculature observed in ex vivo studies translated into alterations in vascular haemodynamics in vivo. In the available conscious animal studies, the in vivo data did not always align with the ex vivo data. This highlights the importance of in vivo work to determine the effects of EVs on the integrative vascular haemodynamics.

Forgotten Circulation: Reduced Mesenteric Venous Capacitance in Hypertensive Rats Is Improved by Decreasing Sympathetic Activity.

BACKGROUND: The mesenteric venous reservoir plays a vital role in mediating blood volume and pressure changes and is richly innervated by sympathetic nerves; however, the precise nature of venous sympathetic regulation and its role during hypertension remains unclear. We hypothesized that sympathetic drive to mesenteric veins in spontaneously hypertensive (SH) rats is raised, increasing mean circulatory filling pressure (MCFP), and impairing mesenteric capacitance. METHODS: Arterial pressure, central venous pressure, mesenteric arterial, and venous blood flow were measured simultaneously in conscious male Wistar and SH rats. MCFP was assessed using an intraatrial balloon. Hemodynamic responses to volume changes (±20%) were measured before and after ganglionic blockade and carotid body denervation. Sympathetic venoconstrictor activity was measured in situ. RESULTS: MCFP in vivo (10.8±1.6 versus 8.0±2.1 mm Hg; P=0.0005) and sympathetic venoconstrictor drive in situ (18±1 versus 10±2 µV; P<0.0001) were higher in SH rats; MCFP decreased in SH rats after hexamethonium and carotid body denervation (7.6±1.4; P<0.0001 and 8.5±1.0 mm Hg; P=0.0045). During volume changes, arterial pressure remained stable. With blood loss, net efflux of blood from the mesenteric bed was measured in both strains. However, during volume infusion, we observed net influx in Wistar (+2.3±2.6 mL/min) but efflux in SH rats (-1.0±1.0 mL/min; P=0.0032); this counterintuitive efflux was abolished by hexamethonium and carotid body denervation (+0.3±1.7 and 0.5±1.6 mL/min, respectively). CONCLUSIONS: In SH rats, excessive sympathetic venoconstriction elevates MCFP and reduces capacitance, impairing volume buffering by mesenteric veins. We propose selective targeting of mesenteric veins through sympathetic drive reduction as a novel therapeutic opportunity for hypertension.