Sphingosine-1-Phosphate Promotes Extravillous Trophoblast Cell Invasion by Activating MEK/ERK/MMP-2 Signaling Pathways via S1P/S1PR1 Axis Activation

Successful placentation depends on the proper invasion of extravillous trophoblast (EVT) cells into maternal tissues. Previous reports demonstrated that S1P receptors are expressed in the EVT cells and S1P could regulate migration and function of trophoblast cells via S1P receptors. However, little is known about roles of S1P in the invasion of EVT cells. Our study was performed to investigate S1P effect on the invasion of EVT cells. We used the extravillous trophoblast cell line HTR8/SVneo cells to evaluate the effect. In vitro invasion assay was employed to determine the invasion of HTR8/SVneo cells induced by S1P. MMP-2 enzyme activity and relative level in the supernatants of HTR8/SVneo was assessed by gelatin zymography and western blot. Based on the above, siRNA and specific inhibitors were used for the intervention and study of potential signal pathways, and Real-time qPCR and western blot were used to test the mRNA and protein level of potential signal targets. We found that S1P could promote HTR8/SVneo cell invasion and upregulates activity and level of MMP-2. The promotion requires activation of MEK-ERK and is dependent on the axis of S1P/S1PR1. Our investigation of S1P may provide new insights into the molecular mechanisms of EVT invasion.     

Bone morphogenetic protein 2 induces the activation of WNT/β-catenin signaling and human trophoblast invasion through up-regulating BAMBI

Both bone morphogenetic protein 2 (BMP2) and WNT/β-catenin signaling promote human trophoblast cell invasion. BMP2 has been shown to up-regulate bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) in granulosa cells. Besides, studies indicate BAMBI is a positive regulator for WNT/β-catenin signaling. However, whether BMP2 can increase BAMBI expression to induce WNT/β-catenin signaling for trophoblast cell invasion is still unknown. To study the roles of BAMBI in BMP2-induced activation of WNT/β-catenin signaling and human trophoblast invasion, we used immortalized human extravillous trophoblast (EVT) cell line (HTR8/SVneo) and primary human EVT cells as study models. Messenger RNA and protein levels of target genes were checked with RT-qPCR and Western blot assay respectively. The function of target proteins was studied via small interfering RNA (siRNA)-mediated knockdown. In addition, trophoblast cell invasiveness was examined by matrigel-coated transwell assays. Our results demonstrate that BMP2 treatment increased BAMBI mRNA levels and the activation of WNT/β-catenin signaling including the raised phosphorylation of GSK3β, the up-regulation of active (non-phosphorylated) β-catenin as well as its downstream target molecule cyclin D1, all of which were totally blocked by the activin receptor-like kinases (ALK) 2/3 inhibitor DMH1 or siRNA-mediated knockdown of BAMBI in HTR8/SVneo cells. Consistently, in primary human EVT cells, BMP2 also induced the up-regulation of BAMBI and the activation of WNT/β-catenin signaling indicated by the increased levels of active β-catenin and cyclin D1, which were completely blocked by BAMBI knockdown. In conclusion, BMP2 promotes the activation of canonical WNT/β-catenin signaling and human trophoblast cell invasion by up-regulating BAMBI.     

CUL1 promotes trophoblast cell invasion at the maternal–fetal interface

Human trophoblast progenitor cells differentiate via two distinct pathways, to become the highly invasive extravillous cytotrophoblast (CTB) cells (EVT) or fuse to form syncytiotrophoblast. Inadequate trophoblast differentiation results in poor placenta perfusion, or even complications such as pre-eclampsia (PE). Cullin1 (CUL1), a scaffold protein in cullin-based ubiquitin ligases, plays an important role in early embryonic development. However, the role of CUL1 in trophoblast differentiation during placenta development has not been examined. Here we show that CUL1 was expressed in CTB cells and EVT in the first trimester human placentas by immunohistochemistry. CUL1 siRNA significantly inhibited outgrowth of extravillous explants in vitro, as well as invasion and migration of HTR8/SVneo cells of EVT origin. This inhibition was accompanied by decreased gelatinolytic activities of matrix metalloproteinase (MMP)-9 and increased expression of tissue inhibitors of MMPs (TIMP-1 and -2). Consistently, exogenous CUL1 promoted invasion and migration of HTR8/SVneo cells. Notably, CUL1 was gradually decreased during trophoblast syncytialization and CUL1 siRNA significantly enhanced forskolin-induced fusion of choriocarcinoma BeWo cells. CUL1 protein levels in human pre-eclamptic placental villi were significantly lower as compared to their matched control placentas. Taken together, our results suggest that CUL1 promotes human trophoblast cell invasion and dysregulation of CUL1 expression may be associated with PE.     

Dissimilar microRNA-21 functions and targets in trophoblastic cell lines of different origin

Trophoblast cells express a singular miRNA expression profile which varies during pregnancy and whose alteration may be associated with pregnancy complications. miR-21, a widely known oncomir, is highly expressed in human placenta but its role in regulating trophoblast cells remains unclear. The aim of this study was to investigate miR-21 functions and targets in HTR-8/SVneo immortalized trophoblast and JEG-3 choriocarcinoma cells, which are trophoblast cell models that differ in their cellular origin. Cells were transfected with miR-21-antagomir, -mimic or their respective controls. Following, cell proliferation (BrdU), migration (Transwell and scratch wound-healing assays), invasion (Matrigel assays) and apoptosis (flow cytometry, TUNEL assay and Western blotting) were assessed. Expression of the potential miR-21 targets phosphatase and tensin homolog (PTEN) and programmed cell death 4 (PDCD4) were analyzed by Western blotting. Inhibition of miR-21 decreased cell proliferation, migration, and invasion in JEG-3 and HTR-8/SVneo cells and additionally, induced apoptosis in JEG-3 cells. Silencing of miR-21 enhanced PDCD4 expression only in JEG-3 cells, and PTEN expression only in HTR-8/SVneo cells. Inhibition of miR-21 significantly increased phosphorylation of AKT in HTR-8/SVneo cells. In conclusion, miR-21 has cell-specific targets depending upon the origin of trophoblastic cells. Furthermore, miR-21 regulates major cellular processes including cell growth, migration, invasion and apoptosis suggesting that its impairment may lead to placental disorders.     

Increased immortalization‐upregulated protein 2 (IMUP‐2) by hypoxia induces apoptosis of the trophoblast and pre‐eclampsia

In regulation of the developmental process, the balance between cellular proliferation and cell death is critical. Placental development tightly controls this mechanism, and increased apoptosis of placental trophoblasts can cause a variety of gynecological diseases. Members of the immortalization‐upregulated protein (IMUP) family are nuclear proteins implicated in SV40‐mediated immortalization and cellular proliferation; however, the mechanisms by which their expression is regulated in placental development are still unknown. We compared IMUP‐2 expression in normal and pre‐eclamptic placental tissues and evaluated the function of IMUP‐2 in HTR‐8/SVneo trophoblast cells under hypoxic conditions. IMUP‐2 was expressed in syncytiotrophoblasts and syncytial knots of the placental villi. IMUP‐2 expression was significantly higher in preterm pre‐eclampsia patients than in patients who went to term (P < 0.001); however, we observed no differences in IMUP‐2 expression between normal term patients with and without pre‐eclampsia. Hypoxic conditions increased apoptosis of HTR8/SVneo trophoblast cells and induced IMUP‐2 expression. Also, apoptosis of HTR‐8/SVneo trophoblast cells was increased after IMUP‐2 gene transfection. These results suggest that IMUP‐2 expression is specifically elevated in preterm pre‐eclampsia and under hypoxic conditions, and that IMUP‐2 induces apoptosis of the trophoblast. Therefore, IMUP‐2 might have functional involvement in placental development and gynecological diseases such as pre‐eclampsia. J. Cell. Biochem. 110: 522–530, 2010. © 2010 Wiley‐Liss, Inc.     

MicroRNA‐210 regulates human trophoblast cell line HTR‐8/SVneo function by attenuating Notch1 expression: Implications for the role of microRNA‐210 in pre‐eclampsia

Successful pregnancy depends on the precise regulation of extravillous trophoblast cell invasion ability. MicroRNA‐210‐3p (miR‐210), which is increased in the placenta of pre‐eclampsia. Furthermore, miR‐210 could inhibit trophoblasts invasion and might act as a serum biomarker for pre‐eclampsia. Previous studies have demonstrated that miR‐210 regulates HUVEC (human umbilical vein endothelial cell)‐mediated angiogenesis by regulating the NOTCH1 signaling pathway. Studies by our group have previously identified that NOTCH1 plays a positive role in regulating trophoblast functions. However, the miR‐210/NOTCH1 signaling pathway in the regulation of trophoblasts and pre‐eclampsia has not been characterized. Therefore, this study was conducted to investigate the role of miR‐210 and its relationship with NOTCH1 in trophoblasts. We first examined the expression levels of miR‐210 and NOTCH1 in pre‐eclamptic and normals placentas. Next, the expression and location of miR‐210 and NOTCH1 in the first‐trimester villi, maternal decidua, and placenta of late pregnancy were shown via in situ hybridization and immunohistochemistry. The trophoblast cell line HTR‐8/SVneo was used to investigate the effects of miR‐210 on the expression of NOTCH1 and cell bioactivity by upregulation and downregulation strategies. The results showed that miR‐210 expression was increased, whereas NOTCH1 expression was decreased in pre‐eclamptic placenta compared with controls. Upregulation of miR‐210 decreased NOTCH1 expression, impaired HTR‐8/SVneo proliferation, migration, invasion, and tube‐like formation capabilities, and promoted apoptosis. In contrast, downregulation of miR‐210 resulted in the opposite effects. These findings suggested that miR‐210 might act as a contributor to trophoblast dysfunction by attenuating NOTCH1 expression.     

The effect of zinc on human trophoblast proliferation and oxidative stress

Adequate Zinc (Zn) intake is required to prevent multiple teratogenic effects however deviations from adequate Zn intake, including high maternal Zn status, have been linked to increased incidence of pregnancy complications, including those associated with inadequate placentation. Using placental trophoblast HTR8/SVneo cells and first trimester human placental explants (n = 12), we assessed the effects of varying Zn concentrations on trophoblast proliferation, viability, apoptosis and oxidative stress. Compared to physiologically normal Zn levels (20 µM), HTR-8/SVneo cell proliferation index was significantly lower in the presence of physiologically elevated (40 µM; P = .020) and supra-physiological (80 µM; P = .007) Zn. The latter was also associated with reduced proliferation (P = .004) and viability (P < .0001) in cultured placental explants, but not apoptosis. Reactive oxygen species production in HTR8/SVneo cultures was significantly higher in the presence of 80 µM Zn compared to all physiologically relevant levels. Oxidative stress, induced by an oxidizing agent menadione, was further exacerbated by high (80 µM) Zn. Zn did not affect lipid peroxidation in either HTR8/SVneo cells or placental explants or antioxidant defense mechanisms that included glutathione reductase and superoxide dismutase. Further study should focus on elucidating mechanisms behind impaired trophoblast proliferation and increased oxidative stress as a result of elevated Zn levels.     

ERp29 affects the migratory and invasive ability of human extravillous trophoblast HTR‐8/SVneo cells via modulating the epithelial‐mesenchymal transition

Dysfunction of trophoblast metastasis into the endometrium is the main cause of pre‐eclampsia (PE); however, the factors affecting this process are still unclear. In this study, we found that endoplasmic reticulum protein 29 (ERp29), one molecular chaperone of the endoplasmic reticulum, was aberrantly upregulated in the placenta of pre‐eclamptic patients compared with healthy controls. Then, an in vitro study using human extravillous trophoblast HTR‐8/SVneo cells showed that ERp29 upregulation could inhibit the migratory and invasive ability of HTR‐8/SVneo cells, while ERp29 downregulation had the opposite effect. Mechanical experiments confirmed that ERp29 blocked trophoblast metastasis via inhibiting the process of epithelial‐mesenchymal transition and affecting the Wnt/β‐catenin signaling pathway. In conclusion, this study revealed the important role of ERp29 in trophoblast metastasis and improved the mechanical understanding of PE occurrence.     

Lysophosphatidic acid‐triggered pathways promote the acquisition of trophoblast endovascular phenotype in vitro

Successful implantation and placentation requires that extravillous cytotrophoblast acquires an endovascular phenotype and remodels uterine spiral arteries. Defects in this mechanism correlate with severe obstetric complications as implantation failure and preeclampsia. Lysophosphatidic acid (LPA) participates in embryo implantation and contributes to vascular physiology in different biological systems. However, the role of LPA on trophoblast endovascular transformation has not been studied. Due to difficulties in studying human pregnancy in vivo, we adopted a pharmacological approach in vitro to investigate LPA action in various aspects of trophoblast endovascular response, such as the formation of endothelial capillary‐like structures, migration, and proliferation. The HTR‐8/SVneo cell line established from human first trimester cytotrophoblast was used to model the acquisition of the endovascular phenotype by the invading trophoblast. LPA increased HTR‐8/SVneo tube formation, migration (wound healing assay and phalloidin staining) and proliferation (MTT assay). LPA G protein‐coupled receptors, LPA₁ and LPA₃, were expressed in HTR‐8/SVneo. By using selective antagonists, we showed that enhanced tubulogenesis was mediated by LPA₃. In addition, cyclooxygenase‐2 and inducible nitric oxide synthase pathways participated in LPA‐stimulated tubulogenesis. Inducible nitric oxide synthase was activated downstream cyclooxygenase‐2. Furthermore, prostaglandin E2 and a nitric oxide donor (SNAP) increased trophoblast tube formation in a concentration‐dependent manner. Finally, we observed that cyclooxygenase‐2 and inducible nitric oxide synthase were localized in the nucleus, and LPA did not modify their cellular distribution. Our results show that LPA‐triggered regulatory pathways promote trophoblast endovascular response in vitro, suggesting a new role for LPA during spiral artery remodeling at the maternal‐fetal interface.     

Advanced Maternal Age‐associated SIRT1 Deficiency Compromises Trophoblast Epithelial−Mesenchymal Transition through an Increase in Vimentin Acetylation

Advanced maternal age (AMA) pregnancies are rapidly increasing and are associated with aberrant trophoblast cell function, poor placentation, and unfavorable pregnancy outcomes, presumably due to premature placental senescence. SIRT1 is an NAD⁺‐dependent deacetylase with well‐known antiaging effects, but its connection with placental senescence is unreported. In this study, human term placentas and first‐trimester villi were collected from AMA and normal pregnancies, and a mouse AMA model was established by cross breeding young and aged male and female C57 mice. SIRT1 expression and activity in HTR8/SVneo cells were genetically or pharmacologically manipulated. Trophoblast‐specific Sirt1‐knockout (KO) mouse placentas were generated by mating Elf5‐Cre and Sirt1 ^fl/fl mice. Trophoblast cell mobility was assessed with transwell invasion and wound‐healing assays. SIRT1‐binding proteins in HTR8/SVneo cells and human placental tissue were identified by mass spectrometry. We identified SIRT1 as the only differentially expressed sirtuin between AMA and normal placentas. It is downregulated in AMA placentas early in the placental life cycle and is barely impacted by paternal age. SIRT1 loss upregulates P53 acetylation and P21 expression and impairs trophoblast invasion and migration. Sirt1‐KO mouse placentas exhibit senescence markers and morphological disruption, along with decreased fetal weight. In trophoblasts, SIRT1 interacts with vimentin, regulating its acetylation. In conclusion, SIRT1 promotes trophoblast epithelial−mesenchymal transition (EMT) to enhance invasiveness by modulating vimentin acetylation. AMA placentas are associated with premature senescence during placentation due to SIRT1 loss. Therefore, SIRT1 may be an antiaging therapeutic target for improving placental development and perinatal outcomes in AMA pregnancies.     

Schistosoma japonicum Soluble Egg Antigens Attenuate Invasion in a First Trimester Human Placental Trophoblast Model

Background

Schistosomiasis affects nearly 40 million women of reproductive age, and is known to elicit a pro-inflammatory signature in the placenta. We have previously shown that antigens from schistosome eggs can elicit pro-inflammatory cytokine production from trophoblast cells specifically; however, the influence of these antigens on other characteristics of trophoblast function, particularly as it pertains to placentation in early gestation, is unknown. We therefore sought to determine the impact of schistosome antigens on key characteristics of first trimester trophoblast cells, including migration and invasion.

Methods

First trimester HTR8/SVneo trophoblast cells were co-cultured with plasma from pregnant women with and without schistosomiasis or schistosome soluble egg antigens (SEA) and measured cytokine, cellular migration, and invasion responses.

Results

Exposure of HTR8 cells to SEA resulted in a pro-inflammatory, anti-invasive signature, characterized by increased pro-inflammatory cytokines (IL-6, IL-8, MCP-1) and TIMP-1. Additionally, these cells displayed 62% decreased migration and 2.7-fold decreased invasion in vitro after treatment with SEA. These results are supported by increased IL-6 and IL-8 in the culture media of HTR8 cells exposed to plasma from Schistosoma japonica infected pregnant women.

Conclusions

Soluble egg antigens found in circulation during schistosome infection increase pro-inflammatory cytokine production and inhibit the mobility and invasive characteristics of the first trimester HTR8/SVneo trophoblast cell line. This is the first study to assess the impact of schistosome soluble egg antigens on the behavior of an extravillous trophoblast model and suggests that schistosomiasis in the pre-pregnancy period may adversely impact placentation and the subsequent health of the mother and newborn.     

Hypoxia‐induced downregulation of XIAP in trophoblasts mediates apoptosis via interaction with IMUP‐2: Implications for placental development during pre‐eclampsia

The regulation of trophoblast apoptosis is essential for normal placentation, and increased placental trophoblast cell apoptosis is the cause of pathologies such as intrauterine growth retardation (IUGR) and pre‐eclampsia. X‐linked inhibitor of apoptosis (XIAP) is expressed in trophoblasts, but little is known about the role of XIAP in placental development. In the present study, the function of XIAP in the placenta and in HTR‐8/SVneo trophoblasts under hypoxic conditions was examined. In addition, the correlation between XIAP and immortalization‐upregulated protein‐2 (IMUP‐2) was demonstrated in HTR‐8/SVneo trophoblasts under hypoxia, based on a previous study showing that increased IMUP‐2 induces trophoblast apoptosis and pre‐eclampsia. XIAP was downregulated in pre‐eclamptic placentas (P < 0.05). In HTR‐8/SVneo trophoblasts, XIAP expression was decreased and the expression of apoptosis‐related genes was increased in response to hypoxia. Ectopic expression of hypoxia inducible factor (HIF)‐1α in HRT‐8 SV/neo cells induced the nuclear translocation of XIAP and alterations of XIAP protein stability. Furthermore, hypoxia induced nuclear translocated XIAP co‐localized with upregulated IMUP‐2 in trophoblast nuclei, and the interaction between XIAP and IMUP‐2 induced apoptosis in HRT‐8 SV/neo cells. The present results suggest that hypoxia‐induced down‐regulation of XIAP mediates apoptosis in trophoblasts through interaction with increased IMUP‐2, and that this mechanism underlies the pathogenesis of pre‐eclampsia. J. Cell. Biochem. 114: 89–98, 2012. © 2012 Wiley Periodicals, Inc.     

Curcumin stimulates angiogenesis through VEGF and expression of HLA‐G in first‐trimester human placental trophoblasts

Curcumin has a protective role in placental diseases like preeclampsia and preterm birth. Very little is known about its functional effects on growth, angiogenesis, and epigenetic activities of human first trimester placenta. HTR8/SVneo trophoblasts cells were used as model for human first trimester placenta. Effects of curcumin (≥80%) in these cells were investigated using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT), radioactive thymidine uptake, quantitative real‐time polymerase chain reaction (qRT‐PCR), promoter DNA methylation, qRT‐PCR array, tube formation, wound healing, and immunoblot assays. PC3 (prostate cancer), JEG‐3 (trophoblast), and HMEC‐1 (endothelial) cells were used as control in various experiments. Unlike in PC3 cells, curcumin stimulated growth, proliferation, and viability in HTR8/SVneo cells. Curcumin increased tube formation, and messenger RNA (mRNA) expression of angiogenic factors such as vascular endothelial growth factor A (VEGFA) and protein expression of proangiogenic factor VEGF receptor‐2 and fatty acid‐binding protein‐4 (FABP4) in these cells. Curcumin‐stimulated tube formation was associated with an increased expression of VEGFR2 and FABP4. The stimulatory effects of curcumin were inhibited by VEGFR2 (SU5416) and FABP4 (BMS309403) inhibitors. Curcumin also significantly increased both mRNA and protein expression of HLA‐G in HTR8/SVneo cells. Curcumin increased mRNA expression of DNMT3A and NOTCH signaling system whereas down‐regulated mRNA expression of HSD11β2. Curcumin enhanced hypomethylation of gene promoters against oxidative stress and DNA damage pathway mediators. Curcumin promotes cell growth, migration, and thus angiogenic potential of these cells. Increased expression of HLA‐G by curcumin, hitherto unknown, is a novel finding since HLA‐G not only favors the immune environment for invasive trophoblasts but also positively modulates angiogenesis.     

人脐带间充质干细胞条件培养基联合白藜芦醇对人滋养层细胞的作用

目的:探讨人脐带间充质干细胞条件培养基联合白藜芦醇对人绒毛膜外滋养层细胞凋亡的影响。方法:通过CCK8细胞活力检测试剂盒测定白藜芦醇及其与人脐带间充质干细胞条件培养基共同处理人绒毛膜外滋养层细胞HTR8后对细胞增殖及活性的影响;细胞迁移试验检测白藜芦醇和人脐带间充质干细胞条件培养基对细胞迁移能力的影响;显微镜观察细胞形态,并用流式细胞仪检测细胞凋亡率的变化;Western blot检测白藜芦醇和人脐带间充质干细胞条件培养基对细胞凋亡相关蛋白Bax、Bcl-2以及迁移相关蛋白MMP-9表达的影响。结果:白藜芦醇能够抑制HTR8细胞增殖,抑制细胞迁移及MMP-9蛋白的表达,改变Bax和Bcl-2蛋白表达诱导细胞凋亡的作用。而人脐带间充质干细胞条件培养基能够逆转白藜芦醇对细胞的抑制作用。结论:人脐带间充质干细胞条件培养基能够通过调控Bax、Bcl-2、MMP-9的蛋白表达逆转白藜芦醇对人绒毛膜外滋养层细胞的抑制作用。人脐带间充质干细胞条件培养基可作为潜在的治疗人绒毛膜外滋养层细胞功能障碍的临床手段,孕妇需要小心使用白藜芦醇。     

Downregulation of BRD4 attenuates high glucose-induced damage of trophoblast cells by inhibiting activation of AKT/mTOR pathway

It was elucidated that bromodomain-containing protein 4 (BRD4) has involvement with diabetic complication. However, the role and molecular mechanism of BRD4 in gestational diabetes mellitus (GDM) are still unclear. In this study, the mRNA and protein contents of BRD4 in placenta tissues of GDM patients and high glucose (HG)-induced HTR8/SVneo cells were detected by qRT-PCR and western blot assay. CCK-8, EdU staining, flow cytometry as well as western blot were applied for the appraisement of cell viability and apoptosis. Wound healing assay and transwell assay were conducted for the assessment of cell migration and invasion. Oxidative stress and inflammatory factors were detected. Additionally, the contents of AKT/mTOR pathway-related proteins were estimated applying western blot. It was discovered that BRD4 expression was ascended in tissues and HG-induced HTR8/SVneo cells. BRD4 downregulation cut down the contents of p-AKT and p-mTOR but had no effects on the total protein levels of AKT or mTOR in HG-induced HTR8/SVneo cells. BRD4 depletion promoted cell viability, enhanced proliferative capability, and reduced cell apoptotic level. Moreover, BRD4 depletion facilitated cell migrative and invasive capabilities, and repressed the oxidative stress as well as inflammatory damage in HG-induced HTR8/SVneo cells. The activation of Akt reversed the protective impacts of BRD4 depletion on HG-induced HTR8/SVneo cells. To sum up, BRD4 silencing may alleviate HG-induced HTR8/SVneo cell damage through the inhibition of the AKT/mTOR pathway.     

Human-specific LAIR2 contributes to the high invasiveness of human extravillous trophoblast cells

The placenta is a temporary vital organ for intra-uterine development and growth. The anatomical structure of the placenta has evolved substantially, resulting in broad inter-species diversity. In particular, human placental extravillous trophoblast cells (EVTs) have evolved aggressive features, although the mechanism underlying this aggressiveness remains elusive. In the present study, we compared the human and mouse homologous gene databases and obtained 2272 human-specific genes, 807 of which are expressed in the placenta according to the UniGene database. Using the human trophoblast cell line HTR8/SVneo, we further verified the expression and function of one of these genes, the leukocyte-associated immunoglobulin-like receptor 2 (LAIR2). This gene shows increased expression during pregnancy and its reduced expression is associated with pregnancy complications. Although LAIR2 was expressed in the human placenta villus and decidua in the first trimester of pregnancy, it was not expressed in mouse tissues. Knockdown of LAIR2 markedly improved cell viability and inhibited the invasive ability of HTR8/SVneo cells. These data suggest that species-specific genes are pivotal to the evolution of a more aggressive human placenta to match the physiological demands of human development. Further investigation is required to obtain evidence on the function of LAIR2 and other specific genes in the placenta, providing insight on the mechanism, properties, and possible applications of this in humans.