Abstract
Adequate blood supply to the uterine-placental region is crucial to ensure the transport of oxygen and nutrients to the growing fetus. Multiple factors intervene to achieve appropriate uterine blood flow and the structuring of the placental vasculature during the early stages of pregnancy. Among these factors, oxygen concentrations, growth factors, cytokines, and steroid hormones are the most important. Sex steroids are present in extremely high concentrations in the maternal circulation and are important paracrine and autocrine regulators of a wide range of maternal and placental functions. In this regard, progesterone and estrogens act as modulators of uterine vessels and decrease the resistance of the spiral uterine arteries. On the other hand, androgens have the opposite effect, increasing the vascular resistance of the uterus. Moreover, progesterone and estrogens modulate the synthesis and release of angiogenic factors by placental cells, which regulates trophoblastic invasion and uterine artery remodeling. In this scenario, it is not surprising that women with pregnancy-related pathologies, such as early miscarriages, preterm delivery, preeclampsia, and fetal growth restriction, exhibit altered sex steroid concentrations.
Highlights
During pregnancy, the placenta has important nutritional, metabolic, and endocrine functions that constitute the link between the mother and the fetus
The formation of blood vessels involves two consecutive processes: (1) vasculogenesis, which involves the structuring of primitive vessels from mesenchymal cells; and (2) angiogenesis, which is the generation of new blood vessels from preexisting vessels to form the vascular placental network (Charnock-Jones et al, 2004)
Uterine blood flow increases dramatically mainly through a decrease in the uterine vascular resistance as a result of uterine arteries dilation and remodeling. Many of these effects are produced by changes in the muscular tone of uterine arteries that are mediated by the action of nitric oxide (NO) and prostanoids
Summary
The placenta has important nutritional, metabolic, and endocrine functions that constitute the link between the mother and the fetus. The formation of blood vessels involves two consecutive processes: (1) vasculogenesis, which involves the structuring of primitive vessels from mesenchymal cells; and (2) angiogenesis, which is the generation of new blood vessels from preexisting vessels to form the vascular placental network (Charnock-Jones et al, 2004). Both processes are driven and regulated by multiple factors, including oxygen concentration, growth factors, cytokines, and steroid hormones. The aim of the present review is to summarize the current knowledge regarding the role of progesterone, androgens, and estrogens in the uterine-placental vasculature
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