Influence of Low Protein Diet-Induced Fetal Growth Restriction on the Neuroplacental Corticosterone Axis in the Rat

Amelioration of oxygen-induced retinopathy in neonatal mice with fetal growth restriction

Introduction: With the aim of optimizing the balance of maintaining a safe oxygen saturation and reducing the risk of retinopathy of prematurity in human neonates with fetal growth restriction (FGR), the present study investigated the distinct effects of oxygen supplementation on the retinal neovasculature using a murine premature neonatal oxygen-induced retinopathy (OIR) model with or without fetal growth restriction. Methods: For comparison with normal birth-weight neonates, maternal low-protein diet-induced FGR neonates were subjected to fluctuating oxygen levels to generate oxygen-induced retinopathy. The retinal neovasculature was histologically evaluated, and comprehensive transcriptome analysis was conducted. Results: Compared to OIR neonates with normal birth weight, significant amelioration of the neovasculature, as indicated by decreases in the number of branch junctions, vascular distribution, maximal vascular radius and microaneurysm-like tufts, was observed in OIR mice with FGR. The results of retinal RNA-sequencing revealed downregulation of angiogenic factors that trigger pathological retinal neovascularization, such as the mitogen-activated protein kinase pathway and corresponding upstream signaling pathways in OIR mice with FGR. Conclusion: Our findings demonstrated that FGR neonates have a higher capacity for retinal oxygen stress, and the risk of OIR development is attenuated compared to that in mature neonates with normal birth weight.

No evidence of the unfolded protein response in the placenta of two rodent models of preeclampsia and intrauterine growth restriction

In humans, intrauterine growth restriction (IUGR) and preeclampsia (PE) are associated with induction of the unfolded protein response (UPR) and increased placental endoplasmic reticulum (ER) stress. Especially in PE, oxidative stress occurs relative to the severity of maternal vascular underperfusion (MVU) of the placental bed. On the premise that understanding the mechanisms of placental dysfunction could lead to targeted therapeutic options for human IUGR and PE, we investigated the roles of the placental UPR and oxidative stress in two rodent models of these human gestational pathologies. We employed a rat IUGR model of gestational maternal protein restriction, as well as an endothelial nitric oxide synthase knockout mouse model (eNOS-/-) of PE/IUGR. Placental expression of UPR members was analyzed via qRT-PCR (Grp78, Calnexin, Perk, Chop, Atf6, and Ern1), immunohistochemistry, and Western blotting (Calnexin, ATF6, GRP78, CHOP, phospho-eIF2α, and phospho-IRE1). Oxidative stress was determined via Western blotting (3-nitrotyrosine and 4-hydroxy-2-nonenal). Both animal models showed a significant reduction of fetal and placental weight. These effects did not induce placental UPR. In contrast to human data, results from our rodent models suggest retention of placental plasticity in the setting of ER stress under an adverse gestational environment. Oxidative stress was significantly increased only in female IUGR rat placentas, suggesting a sexually dimorphic response to maternal malnutrition. Our study advances understanding of the involvement of the placental UPR in IUGR and PE. Moreover, it emphasizes the appropriate choice of animal models researching various aspects of these pregnancy complications.

Disruption of paternal circadian rhythm affects metabolic health in male offspring via nongerm cell factors

Circadian rhythm synchronizes each body function with the environment and regulates physiology. Disruption of normal circadian rhythm alters organismal physiology and increases disease risk. Recent epidemiological data and studies in model organisms have shown that maternal circadian disruption is important for offspring health and adult phenotypes. Less is known about the role of paternal circadian rhythm for offspring health. Here, we disrupted circadian rhythm in male mice by night-restricted feeding and showed that paternal circadian disruption at conception is important for offspring feeding behavior, metabolic health, and oscillatory transcription. Mechanistically, our data suggest that the effect of paternal circadian disruption is not transferred to the offspring via the germ cells but initiated by corticosterone-based parental communication at conception and programmed during in utero development through a state of fetal growth restriction. These findings indicate paternal circadian health at conception as a newly identified determinant of offspring phenotypes.

Phosphorylation of Yes-associated protein impairs trophoblast invasion and migration: implications for the pathogenesis of fetal growth restriction†

Fetal growth restriction (FGR) is a condition in which a newborn fails to achieve his or her prospective hereditary growth potential. This condition is associated with high newborn mortality, second only to that associated with premature birth. FGR is associated with maternal, fetal, and placental abnormalities. Although the placenta is considered to be an important organ for supplying nutrition for fetal growth, research on FGR is limited, and treatment through the placenta remains challenging, as neither proper uterine intervention nor its pathogenesis have been fully elucidated. Yes-associated protein (YAP), as the effector of the Hippo pathway, is widely known to regulate organ growth and cancer development. Therefore, the correlation of the placenta and YAP was investigated to elucidate the pathogenic mechanism of FGR. Placental samples from humans and mice were collected for histological and biomechanical analysis. After investigating the location and role of YAP in the placenta by immunohistochemistry, we observed that YAP and cytokeratin 7 have corresponding locations in human and mouse placentas. Moreover, phosphorylated YAP (p-YAP) was upregulated in FGR and gradually increased as gestational age increased during pregnancy. Cell function experiments and mRNA-Seq demonstrated impaired YAP activity mediated by extracellular signal-regulated kinase inhibition. Established FGR-like mice also recapitulated a number of the features of human FGR. The results of this study may help to elucidate the association of FGR development with YAP and provide an intrauterine target that may be helpful in alleviating placental dysfunction.

Expression of Retinoid Acid Receptor-Responsive Genes in Rodent Models of Placental Pathology

In humans, retinoic acid receptor responders (RARRES) have been shown to be altered in third trimester placentas complicated by the pathologies preeclampsia (PE) and PE with intrauterine growth restriction (IUGR). Currently, little is known about the role of placental Rarres in rodents. Therefore, we examined the localization and expression of Rarres1 and 2 in placentas obtained from a Wistar rat model of isocaloric maternal protein restriction (E18.5, IUGR-like features) and from an eNOS-knockout mouse model (E15 and E18.5, PE-like features). In both rodent models, Rarres1 and 2 were mainly localized in the placental spongiotrophoblast and giant cells. Their placental expression, as well as the expression of the Rarres2 receptor chemokine-like receptor 1 (CmklR1), was largely unaltered at the examined gestational ages in both animal models. Our results have shown that RARRES1 and 2 may have different expression and roles in human and rodent placentas, thereby underlining immanent limitations of comparative interspecies placentology. Further functional studies are required to elucidate the potential involvement of these proteins in early placentogenesis.