SPP1 expression in the mouse uterus and placenta: Implications for implantation

Osteopontin expression in dromedary camel's conceptuses during the peri-implantation period

The reproductive efficiency of dromedary camels is hindered by challenges such as early embryonic mortality, which may be attributed to a lack of synchronization between conceptus signalling and uterine receptivity. Understanding the intricate biological processes involved in feto-maternal interactions during implantation is crucial to address these limitations. Osteopontin (OPN) is a protein involved in cell signalling and adhesion, playing a crucial role in embryonic implantation. Previous studies have shown the presence of OPN in the uterine endometrium of various mammalian species including dromedary camels. However, the expression pattern of OPN in dromedary conceptuses remains unexplored. Thus, the current study aimed, for the first time, to investigate the temporospatial expression of OPN in dromedary conceptuses during the peri-implantation period at Days 8, 10, and 12 of pregnancy. Twelve conceptuses were recovered non-surgically from pregnant females on Days 8, 10, 12 of pregnancy. Quantitative real-time PCR (qrt-PCR), immunohistochemistry (IHC), and immunofluorescence (IF) were employed for analysis of the expression of OPN mRNA and protein. The results revealed significant increases in both OPN mRNA and protein expression started on Day 10 and peaked at Day 12 of pregnancy. Immuno-localization confirmed the presence of OPN protein in the trophectoderm and endoderm of dromedary conceptuses. In conclusion, the expression and localization of OPN during the peri-implantation period in dromedary conceptuses imply its involvement as a crucial reproductive factor and its upregulation during this period, with a pronounced increase close to attachment time (Day 12 of pregnancy) further supports its role in embryo adhesion, implantation, and placentation.

Deciphering decidual deficiencies in recurrent spontaneous abortion and the therapeutic potential of mesenchymal stem cells at single-cell resolution

BACKGROUND

Recurrent spontaneous abortion (RSA) is a challenging condition that affects the health of women both physically and mentally, but its pathogenesis and treatment have yet to be studied in detail. In recent years, Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) have been shown to be effective in treating various diseases. Current understanding of RSA treatment using WJ-MSCs is limited, and the exact mechanisms of WJ-MSCs action in RSA remains largely unclear. In this study, we explored the decidual deficiencies in RSA and the therapeutic potential of WJ-MSCs at single-cell resolution.

METHODS

Three mouse models were established: a normal pregnancy group, an RSA group, and a WJ-MSC treatment group. Decidual tissue samples were collected for single-cell RNA sequencing (scRNA-seq) and functional verification, including single-cell resolution in situ hybridization on tissues (SCRINSHOT) and immunofluorescence.

RESULTS

We generated a single-cell atlas of decidual tissues from normal pregnant, RSA, and WJ-MSC-treated mice and identified 14 cell clusters in the decidua on day 14. Among these cell populations, stromal cells were the most abundant cell clusters in the decidua, and we further identified three novel subclusters (Str_0, Str_1, and Str_2). We also demonstrated that the IL17 and TNF signaling pathways were enriched for upregulated DEGs of stromal cells in RSA mice. Intriguingly, cell-cell communication analysis revealed that Str_1 cell-related gene expression was greatly reduced in the RSA group and rescued in the WJ-MSC treatment group. Notably, the interaction between NK cells and other cells in the RSA group was attenuated, and the expression of Spp1 (identified as an endometrial toleration-related marker) was significantly reduced in the NK cells of the RSA group but could be restored by WJ-MSC treatment.

CONCLUSION

Herein, we implemented scRNA-seq to systematically evaluate the cellular heterogeneity and transcriptional regulatory networks associated with RSA and its treatment with WJ-MSCs. These data revealed potential therapeutic targets of WJ-MSCs to remodel the decidual subpopulations in RSA and provided new insights into decidua-derived developmental defects at the maternal-foetal interface.

Behind the Curtain of Abnormal Placentation in Pre-Eclampsia: From Molecular Mechanisms to Histological Hallmarks

Successful human pregnancy needs several highly controlled steps to guarantee an oocyte's fertilization, the embryo's pre-implantation development, and its subsequent implantation into the uterine wall. The subsequent placenta development ensures adequate fetal nutrition and oxygenation, with the trophoblast being the first cell lineage to differentiate during this process. The placenta sustains the growth of the fetus by providing it with oxygen and nutrients and removing waste products. It is not surprising that issues with the early development of the placenta can lead to common pregnancy disorders, such as recurrent miscarriage, fetal growth restriction, pre-eclampsia, and stillbirth. Understanding the normal development of the human placenta is essential for recognizing and contextualizing any pathological aberrations that may occur. The effects of these issues may not become apparent until later in pregnancy, during the mid or advanced stages. This review discusses the process of the embryo implantation phase, the molecular mechanisms involved, and the abnormalities in those mechanisms that are thought to contribute to the development of pre-eclampsia. The review also covers the histological hallmarks of pre-eclampsia as found during the examination of placental tissue from pre-eclampsia patients.

Effects of recombinant osteopontin expressed in Escherichia coli on the recovery of the endometrial epidermal growth factor profile and fertility in repeat breeder dairy cows

Endometrial epidermal growth factor (EGF) shows a cyclic change with two peaks on days 2-4 and days 13-14 of the estrous cycle. In repeat breeder cows, loss of the peaks has been associated with reduced fertility. By infusing seminal plasma (SP) and osteopontin (OPN) derived from SP and milk into the vagina, their EGF profile and fertility are restored. However, SP is difficult to obtain, and both SP and OPN can transmit infectious diseases. While OPN can be sourced from recombinant protein without this risk, recombinant bovine OPN (rOPN) expressed in Escherichia coli should be examined for its effects on the EGF profile, since it does not undergo posttranslational modification, which is important for its biological activity. In study 1, PBS, SP (0.5 mL), and rOPN (0.3 mg) were infused into the vagina at estrus (day 0) in 74, 37, and 105 repeat breeder Holstein cows, respectively, with an altered EGF profile. The endometrial EGF concentrations were measured on day 3. Some cows (n = 58, 20, and 83, respectively) were inseminated immediately before the infusion and then diagnosed for pregnancy between days 30 and 35. The normalization rate of the EGF profile and conception rate in the rOPN group (58.1 % and 47.0 %, respectively) were not significantly different from those in the SP group (62.2 % and 45.0 %, respectively) but higher than those in PBS group (29.7 % and 28.1 %, respectively) (P < 0.05). In study 2, repeat breeder cows with an altered EGF profile were infused with PBS (n = 18) and rOPN (n = 17), while fertile controls with a normal EGF profile (n = 18) were infused with PBS. Two or three embryos were transferred into cows on day 7 and then recovered on day 14. Embryo recovery rates of the rOPN and fertile groups were comparable (58.7 % vs. 58.3 %) but higher than that of the PBS group (58.7 % vs. 32.0 %) (P < 0.05). The embryo recovery rate of cows with normalized EGF profile was higher than that of cows with unnormalized EGF profile (64.4 % vs. 16.7 %) (P < 0.05). The embryo sizes of cows in the rOPN and fertile groups were comparable but larger than those in the PBS group (P < 0.05). However, the embryo size was not correlated to the corresponding endometrial EGF concentrations. In conclusion, rOPN without posttranslational modifications normalized the EGF profile in repeat breeder cows. Improved fertility by normalization of the EGF profile could be attributed partly to the increased embryo viability up to day 14.

Synthesis of phospholipids in human placenta

INTRODUCTION

Placental phospholipid synthesis is critical for the expansion of the placental exchange surface area and for production of signaling molecules. Despite their importance, it is not yet established which enzymes involved in the de novo synthesis and remodeling of placental phospholipids are expressed and active in the human placenta.

METHODS

We identified phospholipid synthesis enzymes by immunoblotting in placental homogenates and immunofluorescence in placenta tissue sections. Primary human trophoblast (PHT) cells from term healthy placentas (n = 10) were cultured and exposed to 13C labeled fatty acids (16:0, 18:1 and 18:2 n-6, 22:6 n-3) for 2 and 24 h. Three phospholipid classes; phosphatidic acid, phosphatidylcholine, and lysophosphatidylcholine containing 13C fatty acids were quantified by Liquid Chromatography with tandem mass spectrometry (LC/MS-MS).

RESULTS

Acyl transferase and phospholipase enzymes were detected in human placenta homogenate and primarily expressed in the syncytiotrophoblast. Three representative 13C fatty acids (16:0, 18:1 and 18:2 n-6) were incorporated rapidly into phosphatidic acid in trophoblasts, but 13C labeled docosahexaenoic acid (DHA; 22:6 n-3) incorporation was not detected. 13C DHA was incorporated into phosphatidylcholine. Lysophosphatidylcholine containing all four 13C labeled fatty acids were found in high abundance.

CONCLUSIONS

Phospholipid synthesis and remodeling enzymes are present in the syncytiotrophoblast. 13C labeled fatty acids were rapidly incorporated into cellular phospholipids. 13C DHA was incorporated into phospholipids through the remodeling pathway rather than by de novo synthesis. These understudied pathways are highly active and critical for structure and function of the placenta.

Screening the optimal housekeeping genes (HKGs) of placenta tissues by RNA-sequence and qRT-PCR throughout gestation in goat (Capra Hircus)

Selection of stable housekeeping genes (HKGs) is very important for accurate calculation of relative expression levels of target genes by quantitative real-time polymerase chain reaction (qRT-PCR). At present, the appropriate HKGs have not been identified in placental tissues throughout the pregnancy of the goat. In our study, 20 HKGs were tentatively selected from RNA-seq data and previous reports. The cycle threshold (Ct) of HKGs was determined by qRT-PCR in trophoblast membrane and cotyledon villus collected from 38 Dazu Black goats on gestation days of 20, 25, 30, 45, 60, 90, 120, and 150 (birth). The expression stability of the HKGs was analyzed by geNorm, Normfinder, Bestkeeper and Delta Ct algorithms, and comprehensively evaluated by ReFinder and ComprFinder. In addition, the optimal HKGs were further verified by placenta-specific genes (SPP1, VEGFA and PAG6). The 16 candidate HKGs (except POP4, TBP, RNF10, UBC) showed a qualified Ct value, less than 28. Among them, YWHAZ, EIF3K and PPIB showed the most stable expression in placental tissues during early, mid-late pregnancy and postpartum, but the least stable expression was B2M at early and mid-late stage, and PPIB at postpartum. After comprehensive analysis, RPLP0, EIF3K and YWHAZ were found to be the most stable placental HKGs throughout pregnancy. The classical HKGs, ACTB, GAPDH and 18S RNA have unstable expressions and even ranked at the bottom of the list from comprehensive index, suggesting an inappropriate for target gene normalization. Taken together, our study confirmed that YWHAZ, EIF3K, HMBS and RPLP0 may be the optimal HKGs in goat placenta at different stage of pregnancy, which provided a valuable reference of HKGs on functional gene expression detection for further research on placenta development and growth in ruminants.

Integrins and their potential roles in mammalian pregnancy

Integrins are a highly complex family of receptors that, when expressed on the surface of cells, can mediate reciprocal cell-to-cell and cell-to-extracellular matrix (ECM) interactions leading to assembly of integrin adhesion complexes (IACs) that initiate many signaling functions both at the membrane and deeper within the cytoplasm to coordinate processes including cell adhesion, migration, proliferation, survival, differentiation, and metabolism. All metazoan organisms possess integrins, and it is generally agreed that integrins were associated with the evolution of multicellularity, being essential for the association of cells with their neighbors and surroundings, during embryonic development and many aspects of cellular and molecular biology. Integrins have important roles in many aspects of embryonic development, normal physiology, and disease processes with a multitude of functions discovered and elucidated for integrins that directly influence many areas of biology and medicine, including mammalian pregnancy, in particular implantation of the blastocyst to the uterine wall, subsequent placentation and conceptus (embryo/fetus and associated placental membranes) development. This review provides a succinct overview of integrin structure, ligand binding, and signaling followed with a concise overview of embryonic development, implantation, and early placentation in pigs, sheep, humans, and mice as an example for rodents. A brief timeline of the initial localization of integrin subunits to the uterine luminal epithelium (LE) and conceptus trophoblast is then presented, followed by sequential summaries of integrin expression and function during gestation in pigs, sheep, humans, and rodents. As appropriate for this journal, summaries of integrin expression and function during gestation in pigs and sheep are in depth, whereas summaries for humans and rodents are brief. Because similar models to those illustrated in Fig. 1, 2, 3, 4, 5 and 6 are present throughout the scientific literature, the illustrations in this manuscript are drafted as Viking imagery for entertainment purposes.

Screening of Candidate Housekeeping Genes in Uterus Caruncle by RNA-Sequence and qPCR Analyses in Different Stages of Goat (Capra hircus)

The uterus is a critical pregnancy organ for mammals. The normal growth and development of ruminant uterus caruncles are crucial to maintain gestation and fetal health in goats. Quantitative real-time polymerase chain reaction (qRT-PCR) is a reliable tool to study gene expression profiling for exploring the intrinsic mechanism underlying the conversion process of uterus caruncle tissue. However, the candidate housekeeping genes (HKGs) are required for normalizing the expression of function genes. In our study, 22 HKGs were selected from analyzing transcriptome data at non-pregnancy and pregnancy processes and previous reports about HKGs in goat tissues. We assessed them for expression suitability in 24 samples from uterus tissues at 15 non-pregnant days (Stage 1), early (Stage 2), and medium-later pregnant days (Stage 3). The expression stability of these genes was evaluated by using geNorm, Normfinder, Bestkeeper, and Delta Ct algorithms and, comprehensively, by ReFinder. In addition, the most and least stable HKGs were used to normalize the target genes expression of SPP1, VEGFA, and PAG8. It was found that traditional reference genes, such as ACTB and GAPDH, were not suitable for target gene normalization. In contrast, PPIB selected from RNA sequencing data and EIF3K selected from previous references showed the least variation and were recommended as the best HKGs during the nonpregnant stage and the whole stages of goat uterus caruncle tissue, respectively. It is the first time the HKGs genes in uterus during the non-pregnant day and throughout the total pregnancy have been explored. These findings found suitable HKGs in uterus caruncle tissues at various stages of non-pregnancy and pregnancy; these can be useful for gene expression studies to reveal the molecular mechanisms of uterus development in goats.

Interleukin-15 deficient rats have reduced osteopontin at the maternal-fetal interface

Introduction: Uterine Natural Killer (NK) cells are the predominant immune cells within the decidua during early pregnancy. These cells are thought to regulate aspects of decidualization and placental development, but their functions remain poorly characterized, especially in species with deeply invading trophoblasts such as humans and rats. Interleukin-15 (IL-15) is a cytokine required for NK cell development and survival. IL-15 mutant (IL15Δ/Δ) rats lack NK cells and exhibit altered placental development with precocious trophoblast invasion. In this study, we profiled gene expression differences between wild-type and IL15Δ/Δ implantation sites to reveal candidate factors produced by uterine NK cells that may regulate placentation and trophoblast invasion. Methods: Clariom S gene expression profiling was performed using implantation sites collected from pregnant wild-type and IL15Δ/Δ rats on gestational day 9.5. Levels and localization of perforin and osteopontin in implantation sites from wild-type and IL15Δ/Δ rats were further analyzed. The effect of osteopontin on the invasive capacity of rat trophoblasts was evaluated using Matrigel-based Transwell assays. Results: There were 257 genes differentially expressed between wild-type and IL15Δ/Δ implantation sites on gestational day 9.5, including decreased expression of various NK cell markers in IL15Δ/Δ rats, as well as Spp1, which encodes osteopontin. In wild-type rats, osteopontin was present within the decidua basalis and adjacent to the primitive placenta, and osteopontin colocalized with the NK cell marker perforin. Osteopontin was also detectable in uterine glands. Conversely, in IL15Δ/Δ rats, osteopontin and perforin were not readily detectable in the decidua despite robust osteopontin levels in uterine glands. Neutralization of osteopontin in media conditioned by cells isolated from the decidua decreased invasion of rat trophoblasts, suggesting that reduced levels of osteopontin are unlikely to account for the precocious trophoblast invasion in IL15Δ/Δ rats. Conclusion: Osteopontin is expressed by NK cells at the maternal-fetal interface in rats and may contribute to modulation of trophoblast invasion.

Integrative Proteomics and Transcriptomics Profiles of the Oviduct Reveal the Prolificacy-Related Candidate Biomarkers of Goats (Capra hircus) in Estrous Periods

The oviduct is a dynamic reproductive organ for mammalian reproduction and is required for gamete storage, maturation, fertilization, and early embryonic development, and it directly affects fecundity. However, the molecular regulation of prolificacy occurring in estrous periods remain poorly understood. This study aims to gain a better understanding of the genes involved in regulating goat fecundity in the proteome and transcriptome levels of the oviducts. Twenty female Yunshang black goats (between 2 and 3 years old, weight 52.22 ± 0.43 kg) were divided into high- and low-fecundity groups in the follicular (FH and FL, five individuals per group) and luteal (LH and LL, five individuals per group) phases, respectively. The DIA-based high-resolution mass spectrometry (MS) method was used to quantify proteins in twenty oviducts. A total of 5409 proteins were quantified, and Weighted gene co-expression network analysis (WGCNA) determined that the tan module was highly associated with the high-fecundity trait in the luteal phase, and identified NUP107, ANXA11, COX2, AKP13, and ITF140 as hub proteins. Subsequently, 98 and 167 differentially abundant proteins (DAPs) were identified in the FH vs. FL and LH vs. LL comparison groups, respectively. Parallel reaction monitoring (PRM) was used to validate the results of the proteomics data, and the hub proteins were analyzed with Western blot (WB). In addition, biological adhesion and transporter activity processes were associated with oviductal function, and several proteins that play roles in oviductal communication with gametes or embryos were identified, including CAMSAP3, ITGAM, SYVN1, EMG1, ND5, RING1, CBS, PES1, ELP3, SEC24C, SPP1, and HSPA8. Correlation analysis of proteomics and transcriptomic revealed that the DAPs and differentially expressed genes (DEGs) are commonly involved in the metabolic processes at the follicular phase; they may prepare the oviductal microenvironment for gamete reception; and the MAP kinase activity, estrogen receptor binding, and angiotensin receptor binding terms were enriched in the luteal phase, which may be actively involved in reproductive processes. By generating the proteome data of the oviduct at two critical phases and integrating transcriptome analysis, we uncovered novel aspects of oviductal gene regulation of fecundity and provided a reference for other mammals.

Aclonifen could induce implantation failure during early embryonic development through apoptosis of porcine trophectoderm and uterine luminal epithelial cells

Aclonifen is a diphenyl-ether herbicide that is used to control the growth of weeds while growing crops such as corn and wheat. Although the biochemical effects of aclonifen are well characterized, including its ability to inhibit protoporphyrinogen oxidase and carotenoid synthesis, the toxicity of aclonifen in embryonic implantation and development during early pregnancy, has not been reported. Thus, in this study, we investigated the potential interference of aclonifen in embryonic implantation using porcine trophectoderm (pTr) and uterine luminal epithelial (pLE) cells isolated during implantation period of early pregnancy. Cell viability in both pTr and pLE cells significantly decreased in a dose-dependent manner following aclonifen treatment. Moreover, the proportion of cells in the sub-G1 phase of the cell cycle gradually increased upon treatment with increasing concentrations of aclonifen, which in turn led to an increase in the number of apoptotic cells, as determined by annexin V and propidium iodide staining. Aclonifen treatment caused mitochondrial dysfunction by increasing the depolarization of the mitochondrial membrane potential and the mitochondrial calcium concentration. Aclonifen inhibited cell mobility by suppressing the expression of implantation-related genes in pTr and pLE cells. To explore the underlying mechanism, we evaluated the phosphorylation of PI3K and MAPK signaling molecules. The phosphorylation of AKT, S6, JNK, and ERK1/2 were significantly increased by aclonifen. Collectively, our results suggest that aclonifen may interrupt implantation during early pregnancy by disrupting maternal-fetal interaction.

Role of osteopontin (OPN) in uterine spiral artery remodeling

Uterine spiral artery (SpA) remodeling is critical for a successful pregnancy. The deficiency of SpA remodeling seriously affects the blood perfusion of the placenta, impacting the nutritional supply to the fetus and therefore fetal growth and development, which is one of the pathological causes of pregnancy related diseases. This process involves the interaction between all cells and related factors at the maternal-fetal interface, especially extravillous trophoblast cells (EVT), vascular smooth muscle cells (VSMCs) and decidual immune cells. Osteopontin (OPN), as a glycosylated protein, is widely localized in the extracellular matrix and participates in a variety of cellular activities such as migration, adhesion, differentiation and survival. OPN plays an important role in placental development, uterine decidualization and pregnancy success. This study focuses on the role of OPN in uterine spiral artery remodeling and its related molecular mechanism.