Is the metrial gland really a gland?

Label-free differentiation of functional zones in mature mouse placenta using micro-Raman imaging

In histopathology, it is highly crucial to have chemical and structural information about tissues. Additionally, the segmentation of zones within a tissue plays a vital role in investigating the functions of these regions for better diagnosis and treatment. The placenta plays a vital role in embryonic and fetal development and in diagnosing some diseases associated with its dysfunction. This study provides a label-free approach to obtain the images of mature mouse placenta together with the chemical differences between the tissue compartments using Raman spectroscopy. To generate the Raman images, spectra of placental tissue were collected using a custom-built optical setup. The pre-processed spectra were analyzed using statistical and machine learning methods to acquire the Raman maps. We found that the placental regions called decidua and the labyrinth zone are biochemically distinct from the junctional zone. A histologist performed a comparison and evaluation of the Raman map with histological images of the placental tissue, and they were found to agree. The results of this study show that Raman spectroscopy offers the possibility of label-free monitoring of the placental tissue from mature mice while simultaneously revealing crucial structural information about the zones.

Histology Atlas of the Developing Mouse Placenta

The use of the mouse as a model organism is common in translational research. This mouse-human similarity holds true for placental development as well. Proper formation of the placenta is vital for development and survival of the maturing embryo. Placentation involves sequential steps with both embryonic and maternal cell lineages playing important roles. The first step in placental development is formation of the blastocyst wall (approximate embryonic days [E] 3.0-3.5). After implantation (∼E4.5), extraembryonic endoderm progressively lines the inner surface of the blastocyst wall (∼E4.5-5.0), forming the yolk sac that provides histiotrophic support to the embryo; subsequently, formation of the umbilical vessels (∼E8.5) supports transition to the chorioallantoic placenta and hemotrophic nutrition. The fully mature ("definitive") placenta is established by ∼E12.5. Abnormal placental development often leads to embryonic mortality, with the timing of death depending on when placental insufficiency takes place and which cells are involved. This comprehensive macroscopic and microscopic atlas highlights the key features of normal and abnormal mouse placental development from E4.5 to E18.5. This in-depth overview of a transient (and thus seldom-analyzed) developmental tissue should serve as a useful reference to aid researchers in identifying and describing mouse placental changes in engineered, induced, and spontaneous disease models.

Molecular regulation of vascular smooth muscle cell phenotype switching by trophoblast cells at the maternal-fetal interface

INTRODUCTION

Establishment of hemochorial placenta is associated with development and remodelling of uterine vasculature at the maternal fetal interface. This results in calibration of high resistance uterine arteries to flaccid low resistance vessels resulting in increased blood flow to the placenta and fetus in humans and rodents. Mechanisms underlying these remodelling events are poorly understood. In this report, we examine regulation of vascular remodelling using vascular smooth muscle cell (VSMC) phenotype switching as a primary parameter.

METHODS

Cellular dynamics was assessed by Immunofluorescence, qRT-PCR, western blotting in timed pregnant rat tissue. In vitro co-culture of trophoblast cells with vascular smooth muscle cells was used to understand regulation mechanism.

RESULTS

Analysis of cellular dynamics on days 13.5, 16.5 and 19.5 of gestation in the rat metrial gland, the entry point of uterine arteries, revealed that invasion of trophoblast cells preceded disappearance of VSMC α-SMA, a contractile state marker. Co-culture of VSMCs with trophoblast cells in vitro recapitulated trophoblast-induced de-differentiation of VSMCs in vivo. Interestingly, co-culturing with trophoblast cells activated PDGFRβ signalling in VSMCs, an effect mediated by secreted PDGF-BB from trophoblast cells. Trophoblast cells failed to elicit its effect on VSMC de-differentiation upon inhibition of PDGFRβ signalling using a selective inhibitor. Moreover, co-culturing with trophoblast cells also led to substantial increase in Akt activation and a modest increase in Erk phosphorylation in VSMCs and this effect was abolished by PDGFRβ inhibition.

DISCUSSION

Our results highlight that trophoblast cells direct VSMC phenotype switching and trophoblast derived PDGF-BB is one of the modulator.

Dexamethasone-induced Intra-Uterine Growth Restriction impacts NOSTRIN and its downstream effector genes in the rat mesometrial uterus

Intra-Uterine Growth Restriction (IUGR) is a major cause of fetal and neonatal mortality. Understanding the impact of IUGR on utero-placental gene expression is key to developing effective therapy. In this report we elucidated the impact of IUGR on NOSTRIN and its downstream effector gene expression in the utero-placental compartments. We showed here that induction of IUGR by maternal dexamethasone administration in rats led to up-regulation of NOSTRIN transcript and protein in the mesometrial triangle of the uterus (MG) and not in other utero-placental compartments as compared to control. This was associated with down-regulation of twelve genes and four cytokines that were known to be regulated by NOSTRIN and also required for maintenance of pregnancy. Interestingly, there was remarkable decrease in phosphorylation of RelA transcription factor in the MG during IUGR in line with the fact that the down regulated genes harbour RelA transcription activation domain in their promoters. Furthermore, HIF-1α level was reciprocal to NOSTRIN expression pattern in the mesometrial compartment during IUGR and also in CoCl₂ treated endothelial cells. Over-expression of HIF-1α led to a decrease in NOSTRIN levels suggesting inhibition of Nostrin transcription by HIF-1α. Our findings highlight the importance of NOSTRIN in uterine pathophysiology during IUGR.

Rat placentation: an experimental model for investigating the hemochorial maternal-fetal interface

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-directed uterine spiral artery remodeling; features shared with human placentation. Recognition of these similarities spurred the establishment of in vitro and in vivo research methods using the rat as an animal model to address mechanistic questions regarding development of the hemochorial placenta. The purpose of this review is to provide the requisite background to help move the rat to the forefront in placentation research.

Spatiotemporal patterns of macrophage migration inhibitory factor (Mif) expression in the mouse placenta

BACKGROUND

Macrophage migration inhibitory factor (MIF) has special pro-inflammatory roles, affecting the functions of macrophages and lymphocytes and counter-regulating the effects of glucocorticoids on the immune response. The conspicuous expression of MIF during human implantation and early embryonic development also suggests this factor acts in reproductive functions. The overall goal of this study was to evaluate Mif expression by trophoblast and embryo placental cells during mouse pregnancy.

METHODS

Mif was immunolocalized at implantation sites on gestation days (gd) 7.5, 10.5, 13.5 and 17.5. Ectoplacental cones and fetal placentas dissected from the maternal tissues were used for Western blotting and qRT-PCR assays on the same gestation days.

RESULTS

During the post-implantation period (gd7.5), trophoblast giant cells showed strong Mif reactivity. In later placentation phases (gds 10.5-17.5), Mif appeared to be concentrated in the junctional zone and trophoblast giant cells. Mif protein expression increased significantly from gd7.5 to 10.5 (p = 0.005) and from gd7.5 to 13.5 (p = 0.03), remaining at high concentration as gestation proceeded. Higher mRNA expression was found on gd10.5 and was significantly different from gd13.5 (p = 0.048) and 17.5 (p = 0.009).

CONCLUSIONS

The up-regulation of Mif on gd10.5 coincides with the stage in which the placenta assumes its three-layered organization (giant cells, spongiotrophoblast and labyrinth zones), fetal blood circulation begins and population of uNK cells reaches high proportions at the maternal counter part of the placenta, suggesting that Mif may play a role in either the placentation or in the adaptation of the differentiated placenta to the uterus or still in gestational immunomodulatory responses. Moreover, it reinforces the possibility of specific activities for Mif at the maternal fetal interface.

Maternal hypoxia activates endovascular trophoblast cell invasion

Oxygen is a critical regulator of placentation. Early placental development occurs in a predominantly low oxygen environment and is, at least partially, under the control of hypoxia signaling pathways. In the present study, in vivo hypobaric hypoxia was used as an experimental tool to delineate hypoxia-sensitive events during placentation. Pregnant rats were exposed to the equivalent of 11% oxygen between days 6.5 and 13.5 of gestation. Pair-fed pregnant animals exposed to ambient conditions were included as a control group. Uterine mesometrial blood vessels in the hypoxia-exposed animals were greatly expanded and some contained large cuboidal cells that were positive for cytokeratin and other markers characteristic of invasive trophoblast cells. Unlike later in gestation, the route of trophoblast cell invasion in the hypoxia-exposed animals was restricted to endovascular, with no interstitial invasion observed. Hypoxia-activated endovascular trophoblast invasion required exposure to hypoxia from gestation day 8.5 to day 9.5. Activation of the invasive trophoblast lineage was also associated with an enlargement of the junctional zone of the chorioallantoic placenta, a source of invasive trophoblast cell progenitors. In summary, maternal hypoxia during early stages of placentation activates the invasive endovascular trophoblast cell lineage and promotes uterine vascular remodeling.