[PROK1, prognostic marker of embryo implantation?]

Evidence-Based View of Safety and Effectiveness of Prokineticin Receptors Antagonists during Pregnancy

Endocrine gland derived vascular endothelial growth factor (EG-VEGF) is a canonical member of the prokineticin (PROKs) family. It acts via the two G-protein coupled receptors, namely PROKR1 and PROKR2. We have recently demonstrated that EG-VEGF is highly expressed in the human placenta; contributes to placental vascularization and growth and that its aberrant expression is associated with pregnancy pathologies including preeclampsia and fetal growth restriction. These findings strongly suggested that antagonization of its receptors may constitute a potential therapy for the pregnancy pathologies. Two specific antagonists of PROKR1 (PC7) and for PROKR2 (PKRA) were reported to reverse PROKs adverse effects in other systems. In the view of using these antagonists to treat pregnancy pathologies, a proof of concept study was designed to determine the biological significances of PC7 and PKRA in normal pregnancy outcome. PC7 and PKRA were tested independently or in combination in trophoblast cells and during early gestation in the gravid mouse. Both independent and combined treatments uncovered endogenous functions of EG-VEGF. The independent use of antagonists distinctively identified PROKR1 and PROKR2-mediated EG-VEGF signaling on trophoblast differentiation and invasion; thereby enhancing feto-placental growth and pregnancy outcome. Thus, our study provides evidence for the potential safe use of PC7 or PKRA to improve pregnancy outcome.

The Emerging Role of the Prokineticins and Homeobox Genes in the Vascularization of the Placenta: Physiological and Pathological Aspects

Vasculogenesis and angiogenesis are key processes of placental development, which occur throughout pregnancy. Placental vasculogenesis occurs during the first trimester of pregnancy culminating in the formation of hemangioblasts from intra-villous stem cells. Placental angiogenesis occurs subsequently, forming new blood vessels from existing ones. Angiogenesis also takes place at the fetomaternal interface, allowing essential spiral arteriole remodeling to establish the fetomaternal circulation. Vasculogenesis and angiogenesis in animal models and in humans have been studied in a wide variety of in vitro, physiological and pathological conditions, with a focus on the pro- and anti-angiogenic factors that control these processes. Recent studies revealed roles for new families of proteins, including direct participants such as the prokineticin family, and regulators of these processes such as the homeobox genes. This review summarizes recent advances in understanding the molecular mechanisms of actions of these families of proteins. Over the past decade, evidence suggests increased production of placental anti-angiogenic factors, as well as angiogenic factors are associated with fetal growth restriction (FGR) and preeclampsia (PE): the most threatening pathologies of human pregnancy with systemic vascular dysfunction. This review also reports novel clinical strategies targeting members of these family of proteins to treat PE and its consequent effects on the maternal vascular system.

miR‑28‑5p suppresses cell proliferation and weakens the progression of polycystic ovary syndrome by targeting prokineticin‑1

Prokineticin‑1 (PROK1) serves important roles in the pathogenesis of polycystic ovary syndrome (PCOS); however, the association between microRNA (miR)‑28‑5p and PROK1 remains unclear. In the present study, the roles of miR‑28‑5p and PROK1, and their interaction in PCOS were investigated. Rat ovary granule cells were transfected with miR‑28‑5p mimics, and PROK1 expression levels were measured by reverse transcription‑quantitative PCR and western blotting. A dual‑luciferase reporter assay was performed to determine the association between miR‑28‑5p and PROK1. Additionally, pcDNA‑PROK1 was co‑transfected into rat ovary granule cells with miR‑28‑5p mimics. Cell proliferation, apoptosis, cell cycle and the expression of signaling proteins were investigated using Cell Counting Kit‑8 assays, 5‑ethynyl‑2'‑deoxyuridine staining, flow cytometry and western blotting, respectively. PROK1 expression was suppressed in rat ovary granule cells by miR‑28‑5p mimics, but upregulated following transfection with miR‑28‑5p inhibitors. The dual‑luciferase reporter assay revealed that miR‑28‑5p binds to the 3'‑untranslated region of PROK1. Proliferation activity was increased in PROK1‑overexpressing cells; this effect was eliminated by co‑transfection with miR‑28‑5p mimics. PROK1‑overexpressing rat ovary granule cells exhibited significantly suppressed cell apoptosis and a decreased number of cells in G1; miR‑28‑5p mimics reversed these effects. Western blotting revealed that the PI3K/AKT/mTOR signaling pathway was activated by PROK1. The present results suggested that miR‑28‑5p attenuated the progression of PCOS by targeting PROK1, which may promote the pathogenesis of PCOS via the PI3K/AKT/mTOR pathway, indicating that the miR‑28‑5p/PROK1 axis may be a potential therapeutic target for patients with PCOS.

PPARγ controls pregnancy outcome through activation of EG-VEGF: new insights into the mechanism of placental development

PPARγ-deficient mice die at E9.5 due to placental abnormalities. The mechanism by which this occurs is unknown. We demonstrated that the new endocrine factor EG-VEGF controls the same processes as those described for PPARγ, suggesting potential regulation of EG-VEGF by PPARγ. EG-VEGF exerts its functions via prokineticin receptor 1 (PROKR1) and 2 (PROKR2). This study sought to investigate whether EG-VEGF mediates part of PPARγ effects on placental development. Three approaches were used: 1) in vitro, using human primary isolated cytotrophoblasts and the extravillous trophoblast cell line (HTR-8/SVneo); 2) ex vivo, using human placental explants (n = 46 placentas); and 3) in vivo, using gravid wild-type PPARγ(+/-) and PPARγ(-/-) mice. Major processes of placental development that are known to be controlled by PPARγ, such as trophoblast proliferation, migration, and invasion, were assessed in the absence or presence of PROKR1 and PROKR2 antagonists. In both human trophoblast cell and placental explants, we demonstrated that rosiglitazone, a PPARγ agonist, 1) increased EG-VEGF secretion, 2) increased EG-VEGF and its receptors mRNA and protein expression, 3) increased placental vascularization via PROKR1 and PROKR2, and 4) inhibited trophoblast migration and invasion via PROKR2. In the PPARγ(-/-) mouse placentas, EG-VEGF levels were significantly decreased, supporting an in vivo control of EG-VEGF/PROKRs system during pregnancy. The present data reveal EG-VEGF as a new mediator of PPARγ effects during pregnancy and bring new insights into the fine mechanism of trophoblast invasion.

The multiple roles of EG-VEGF/PROK1 in normal and pathological placental angiogenesis

Placentation is associated with several steps of vascular adaptations throughout pregnancy. These vascular changes occur both on the maternal and fetal sides, consisting of maternal uterine spiral arteries remodeling and placental vasculogenesis and angiogenesis, respectively. Placental angiogenesis is a pivotal process for efficient fetomaternal exchanges and placental development. This process is finely controlled throughout pregnancy, and it involves ubiquitous and pregnancy-specific angiogenic factors. In the last decade, endocrine gland derived vascular endothelial growth factor (EG-VEGF), also called prokineticin 1 (PROK1), has emerged as specific placental angiogenic factor that controls many aspects of normal and pathological placental angiogenesis such as recurrent pregnancy loss (RPL), gestational trophoblastic diseases (GTD), fetal growth restriction (FGR), and preeclampsia (PE). This review recapitulates EG-VEGF mediated-angiogenesis within the placenta and at the fetomaternal interface and proposes that its deregulation might contribute to the pathogenesis of several placental diseases including FGR and PE. More importantly this paper argues for EG-VEGF clinical relevance as a potential biomarker of the onset of pregnancy pathologies and discusses its potential usefulness for future therapeutic directions.