Stimulation of soluble guanylate cyclase diminishes intrauterine growth restriction in a rat model of placental ischemia

Guidelines for in vivo models of developmental programming of cardiovascular disease risk

Research using animals depends on the generation of offspring for use in experiments or for the maintenance of animal colonies. Although not considered by all, several different factors preceding and during pregnancy, as well as during lactation, can program various characteristics in the offspring. Here, we present the most common models of developmental programming of cardiovascular outcomes, important considerations for study design, and provide guidelines for producing and reporting rigorous and reproducible cardiovascular studies in offspring exposed to normal conditions or developmental insult. These guidelines provide considerations for the selection of the appropriate animal model and factors that should be reported to increase rigor and reproducibility while ensuring transparent reporting of methods and results.

Reduced uterine perfusion pressure as a model for preeclampsia and fetal growth restriction in murine: a systematic review and meta-analysis

The reduced uterine perfusion pressure (RUPP) model is frequently used to study preeclampsia and fetal growth restriction. An improved understanding of influential factors might improve reproducibility and reduce animal use considering the variability in RUPP phenotype. We performed a systematic review and meta-analysis by searching Medline and Embase (until 28 March, 2023) for RUPP studies in murine. Primary outcomes included maternal blood pressure (BP) or proteinuria, fetal weight or crown-rump length, fetal reabsorptions, or antiangiogenic factors. We aimed to identify influential factors by meta-regression analysis. We included 155 studies. Our meta-analysis showed that the RUPP procedure results in significantly higher BP (MD = 24.1 mmHg; [22.6; 25.7]; n = 148), proteinuria (SMD = 2.3; [0.9; 3.8]; n = 28), fetal reabsorptions (MD = 50.4%; [45.5; 55.2]; n = 42), circulating soluble FMS-like tyrosine kinase-1 (sFlt-1) (SMD = 2.6; [1.7; 3.4]; n = 34), and lower fetal weight (MD = -0.4 g; [-0.47; -0.34]; n = 113. The heterogeneity (variability between studies) in primary outcomes appeared ≥90%. Our meta-regression identified influential factors in the method and time point of BP measurement, randomization in fetal weight, and type of control group in sFlt-1. The RUPP is a robust model considering the evident differences in maternal and fetal outcomes. The high heterogeneity reflects the observed variability in phenotype. Because of underreporting, we observed reporting bias and a high risk of bias. We recommend standardizing study design by optimal time point and method chosen for readout measures to limit the variability. This contributes to improved reproducibility and thereby eventually improves the translational value of the RUPP model.

The evolution of small molecule enzyme activators

There is a myriad of enzymes within the body responsible for maintaining homeostasis by providing the means to convert substrates to products as and when required. Physiological enzymes are tightly controlled by many signaling pathways and their products subsequently control other pathways. Traditionally, most drug discovery efforts focus on identifying enzyme inhibitors, due to upregulation being prevalent in many diseases and the existence of endogenous substrates that can be modified to afford inhibitor compounds. As enzyme downregulation and reduction of endogenous activators are observed in multiple diseases, the identification of small molecules with the ability to activate enzymes has recently entered the medicinal chemistry toolbox to afford chemical probes and potential therapeutics as an alternative means to intervene in diseases. In this review we highlight the progress made in the identification and advancement of non-kinase enzyme activators and their potential in treating various disease states.

Growth Restriction in Preeclampsia: Lessons from Animal Models

Preeclampsia remains a major health concern for mother and child. Yet, treatment options remain limited to early delivery. Placental dysfunction in preeclampsia occurs in response to an increase in oxidative stress and inflammatory cytokines with vasoactive and anti-angiogenic factors contributing to impaired maternal and fetal health. Moreover, recent studies indicate a potential role for epigenetic mediators in the pathophysiology of placental ischemia. Numerous animal models are utilized to explore the pathogenesis of preeclampsia and fetal growth restriction. This review provides a brief overview of recent progress in preclinical studies regarding potential therapeutic targets for the treatment and prevention of preeclampsia with an emphasis on fetal growth restriction and the fetal programming of increased cardiovascular risk.

Inhibition of the AT1R agonistic autoantibody in a rat model of preeclampsia improves fetal growth in late gestation

Placenta ischemia, the initiating event in preeclampsia (PE), is associated with fetal growth restriction. Inhibition of the agonistic autoantibody against the angiotensin type 1 receptor AT1-AA, using an epitope-binding inhibitory peptide ('n7AAc') attenuates increased blood pressure at gestational day (G)19 in the clinically relevant reduced uterine perfusion pressure (RUPP) model of PE. Thus we tested the hypothesis that maternal administration of 'n7AAc' does not transfer to the fetus, improves uterine blood flow and fetal growth, and attenuates elevated placental expression of miRNAs implicated in PE and FGR. Sham or RUPP surgery was performed at G14 with vehicle or 'n7AAc' (144 µg/day) administered via an osmotic pump from G14 to G20. Maternal plasma levels of the peptide on G20 were 16.28 ± 4.4 nM, and fetal plasma levels were significantly lower at 1.15 ± 1.7 nM (P = 0.0007). The uterine artery resistance index was significantly elevated in RUPP (P < 0.0001) but was not increased in 'n7AAc'-RUPP or 'n7AAc'-Sham versus Sham. A significant reduction in fetal weight at G20 in RUPP (P = 0.003) was not observed in 'n7AAc'-RUPP. Yet, percent survival was reduced in RUPP (P = 0.0007) and 'n7AAc'-RUPP (P < 0.0002). Correlation analysis indicated the reduction in percent survival during gestation was specific to the RUPP (r = 0.5342, P = 0.043) and independent of 'n7AAc'. Placental miR-155 (P = 0.0091) and miR-181a (P = 0.0384) expression was upregulated in RUPP at G20 but was not elevated in 'n7AAc'-RUPP. Collectively, our results suggest that maternal administration of 'n7AAc' does not alter fetal growth in the RUPP implicating its potential as a therapeutic for the treatment of PE.NEW & NOTEWORTHY The seven amino acid inhibitory peptide to the AT1-AA ('n7AAc') has limited transfer to the fetus at gestational day 20, improves uterine blood flow and fetal growth in the reduced uterine perfusion pressure model of preeclampsia (PE), and does not impair fetal survival during gestation in sham-operated or placental ischemic rats. Collectively, these findings suggest that maternal administration of 'n7AAc' as an effective strategy for the treatment of PE is associated with improved outcomes in the fetus.

Alteration of LncRNA expression in mice placentae after frozen embryo transfer is associated with increased fetal weight

The birthweight after frozen embryo transfer (FET) was significantly higher compared with fresh embryo transfer (fresh ET), while the mechanism remains unclear. In this study, we transferred vitrified-warmed or fresh mice blastocysts into pseudopregnant recipients (n = 11 each group) produced by natural mating to avoid the influence of superovulation. The fetal weight, placental weight, placental efficiency and placental architecture were studied at E18.5. Placental RNA-Seq analysis was used to identify candidate different lncRNAs and mRNAs between the FET group and the fresh ET group. We found that the fetal weight was increased in the FET group, with increased placental efficiency and the proportion of placental function related labyrinth zone area. 554 lncRNAs and 1012 mRNAs were differentially expressed. KEGG and GO enrichment analyses showed these differentially expressed lncRNAs and their targeted mRNAs might be related to placental morphogenesis. Furthermore, the most differentially expressed 15 lncRNAs and 15 mRNAs were validated by qRT-PCR, we found the LncRNA embryonic stem cells expressed 1 (Lncenc1) was significantly decreased, and Gjb5, which played an important role in labyrinth zone development, was increased. Gjb5 protein increase was further confirmed by Western blot. Lncenc1 and Gjb5 had 48 predicted co-targeted miRNAs, while the correlation analysis of Lncenc1 and Gjb5 mRNA showed a significant inverse correlation. The results showed that FET treatment might enhance the placental function to increase mouse fetal weight via the network diagram of Lncenc1-miRNA-Gjb5.

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which resembles human placentation. Uterine spiral arteries are extensively remodeled to deliver sufficient supply of maternal blood and nutrients to the developing fetus. Inadequacies in these key processes negatively impact fetal growth and development. Recent innovations in genome editing combined with effective phenotyping strategies have provided new insights into placental development. Application of these research approaches has highlighted both conserved and species-specific features of hemochorial placentation. The review provides foundational information on rat hemochorial placental development and function during physiological and pathological states, especially as related to the invasive trophoblast cell-guided transformation of uterine spiral arteries. Our goal is to showcase the utility of the rat as a model for in vivo mechanistic investigations targeting regulatory events within the uterine-placental interface.

Placental Ischemia Says "NO" to Proper NOS-Mediated Control of Vascular Tone and Blood Pressure in Preeclampsia

In this review, we first provide a brief overview of the nitric oxide synthase (NOS) isoforms and biochemistry. This is followed by describing what is known about NOS-mediated blood pressure control during normal pregnancy. Circulating nitric oxide (NO) bioavailability has been assessed by measuring its metabolites, nitrite (NO₂) and/or nitrate (NO₃), and shown to rise throughout normal pregnancy in humans and rats and decline postpartum. In contrast, placental malperfusion/ischemia leads to systemic reductions in NO bioavailability leading to maternal endothelial and vascular dysfunction with subsequent development of hypertension in PE. We end this article by describing emergent risk factors for placental malperfusion and ischemic disease and discussing strategies to target the NOS system therapeutically to increase NO bioavailability in preeclamptic patients. Throughout this discussion, we highlight the critical importance that experimental animal studies have played in our current understanding of NOS biology in normal pregnancy and their use in finding novel ways to preserve this signaling pathway to prevent the development, treat symptoms, or reduce the severity of PE.

Soluble guanylate cyclase stimulation in late gestation does not mitigate asymmetric intrauterine growth restriction or cardiovascular risk induced by placental ischemia in the rat

Stimulation of soluble guanylate cyclase (sGC) improves fetal growth at gestational day 20 in the reduced uterine perfusion pressure (RUPP) rat model of placental ischemia suggesting a role for sGC in the etiology of intrauterine growth restriction (IUGR). This study tested the hypothesis that stimulation of sGC until birth attenuates asymmetric IUGR mitigating increased cardiovascular risk in offspring. Sham or RUPP surgery was performed at gestational day 14 (G14); vehicle or the sGC stimulator Riociguat (10 mg/kg/day sc) was administered G14 until birth. Birth weight was reduced in offspring from RUPP [intrauterine growth restricted (IUGR)], sGC RUPP (sGC IUGR), and sGC Sham (sGC Control) compared with Sham (Control). Crown circumference was maintained, but abdominal circumference was reduced in IUGR and sGC IUGR compared with Control indicative of asymmetrical growth. Gestational length was prolonged in sGC RUPP, and survival at birth was reduced in sGC IUGR. Probability of survival to postnatal day 2 was also significantly reduced in IUGR and sGC IUGR versus Control and in sGC IUGR versus IUGR. At 4 mo of age, blood pressure was increased in male IUGR and sGC IUGR but not male sGC Control born with symmetrical IUGR. Global longitudinal strain was increased and stroke volume was decreased in male IUGR and sGC IUGR compared with Control. Thus late gestational stimulation of sGC does not mitigate asymmetric IUGR or increased cardiovascular risk in male sGC IUGR. Furthermore, late gestational stimulation of sGC is associated with symmetrical growth restriction in sGC Control implicating contraindications in normal pregnancy.NEW & NOTEWORTHY The importance of the soluble guanylate cyclase-cGMP pathway in a rat model of placental ischemia differs during critical windows of development, implicating other factors may be critical mediators of impaired fetal growth in the final stages of gestation. Moreover, increased blood pressure at 4 mo of age in male intrauterine growth restriction offspring is associated with impaired cardiac function including an increase in global longitudinal strain in conjunction with a decrease in stroke volume, ejection fraction, and cardiac output.