Effect of 32/67 kDa laminin-binding protein antibody on mouse embryo implantation

The role of extracellular matrix on unfavorable maternal–fetal interface: focusing on the function of collagen in human fertility

Extracellular matrix (ECM) is characterized as widespread, abundant, and pluripotent. Among ECM members, collagen is widely accepted as one of the most prominent components for its essential structural property that can provide a scaffold for other components of ECM and the rich biological functions, which has been extensively used in tissue engineering. Emerging evidence has shown that the balance of ECM degradation and remodeling is vital to regulations of maternal–fetal interface including menstrual cycling, decidualization, embryo implantation and pregnancy maintenance. Moreover, disorders in these events may eventually lead to failure of pregnancy. Although the improvement of assisted conception and embryo culture technologies bring hope to many infertile couples, some unfavorable outcomes, such as recurrent implantation failure (RIF), recurrent pregnancy loss (RPL) or recurrent miscarriage (RM), keep troubling the clinicians and patients. Recently, in vitro three-dimensional (3D) model mimicking the microenvironment of the maternal–fetal interface is developed to investigate the physiological and pathological conditions of conception and pregnancy. The progress of this technology is based on clarifying the role of ECM in the endometrium and the interaction between endometrium and conceptus. Focusing on collagen, the present review summarized the degradation and regulation of ECM and its role in normal menstruation, endometrium receptivity and unsatisfying events occurring in infertility treatments, as well as the application in therapeutic approaches to improve pregnancy outcomes. More investigations about ECM focusing on the maternal–fetal interface interaction with mesenchymal stem cells or local immunoregulation may inspire new thoughts and advancements in the clinical application of infertility treatments.

Graphical abstract

Expression of adhesion and extracellular matrix genes in human blastocysts upon attachment in a 2D co-culture system

STUDY QUESTION

What are the changes in human embryos, in terms of morphology and gene expression, upon attachment to endometrial epithelial cells?

SUMMARY ANSWER

Apposition and adhesion of human blastocysts to endometrial epithelial cells are predominantly initiated at the embryonic pole and these steps are associated with changes in expression of adhesion and extracellular matrix (ECM) genes in the embryo.

WHAT IS KNOWN ALREADY

Both human and murine embryos have been co-cultured with Ishikawa cells, although embryonic gene expression associated with attachment has not yet been investigated in an in vitro implantation model.

STUDY DESIGN, SIZE, DURATION

Vitrified human blastocysts were warmed and co-cultured for up to 48 h with Ishikawa cells, a model cell line for receptive endometrial epithelium.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Six days post-fertilization (6dpf) human embryos were co-cultured with Ishikawa cells for 12, 24 (7dpf) or 48 h (8dpf) and attachment rate and morphological development investigated. Expression of 84 adhesion and ECM genes was analysed by quantitative PCR. Immunofluorescence microscopy was used to assess the expression of three informative genes at the protein level. Data are reported on 145 human embryos. Mann-Whitney U was used for statistical analysis between two groups, with P < 0.05 considered significant.

MAIN RESULTS AND THE ROLE OF CHANCE

The majority of embryos attached to Ishikawa cells at the level of the polar trophectoderm; 41% of co-cultured embryos were loosely attached after 12 h and 86% firmly attached after 24 h. Outgrowth of hCG-positive embryonic cells at 8dpf indicated differentiation of trophectoderm into invasive syncytiotrophoblast. Gene expression analysis was performed on loosely attached and unattached embryos co-cultured with Ishikawa cells for 12 h. In contrast to unattached embryos, loosely attached embryos expressed THBS1, TNC, COL12A1, CTNND2, ITGA3, ITGAV and LAMA3 and had significantly higher CD44 and TIMP1 transcript levels (P = 0.014 and P = 0.029, respectively). LAMA3, THBS1 and TNC expressions were validated at the protein level in firmly attached 7dpf embryos. Thrombospondin 1 (THBS1) resided in the cytoplasm of embryonic cells whereas laminin subunit alpha 3 (LAMA3) and tenascin C (TNC) were expressed on the cell surface of trophectoderm cells. Incubation with a neutralizing TNC antibody did not affect the rate of embryo attachment or hCG secretion.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

This in vitro study made use of an endometrial adenocarcinoma cell line to mimic receptive luminal epithelium. Also, the number of embryos was limited. Contamination of recovered embryos with Ishikawa cells was unlikely based on their differential gene expression profiles.

WIDER IMPLICATIONS OF THE FINDINGS

Taken together, we provide a 'proof of concept' that initiation of the implantation process coincides with the induction of specific embryonic genes. Genome-wide expression profiling of a larger sample set may provide insights into the molecular embryonic pathways underlying successful or failed implantation.

STUDY FUNDING AND COMPETING INTEREST(S)

A.A. was supported by a grant from the 'Instituut voor Innovatie door Wetenschap en Technologie' (IWT, 121716, Flanders, Belgium). This work was supported by the 'Wetenschappelijk Fonds Willy Gepts' (WFWG G142 and G170, Universitair Ziekenhuis Brussel). The authors declare no conflict of interest.

Uterine and placental distribution of selected extracellular matrix (ECM) components in the dog

For many years, modifications of the uterine extracellular matrix (ECM) during gestation have not been considered as critical for successful canine (Canis lupus familiaris) pregnancy. However, previous reports indicated an effect of free-floating blastocysts on the composition of the uterine ECM. Here, the expression of selected genes involved in structural functions, cell-to-cell communication and inhibition of matrix metalloproteinases were targeted utilizing qPCR and immunohistochemistry. We found that canine free-floating embryos affect gene expression of FN1, ECM1 and TIMP4 This seems to be associated with modulation of trophoblast invasion, and proliferative and adhesive functions of the uterus. Although not modulated at the beginning of pregnancy, the decrease of structural ECM components (i.e. COL1, -3, -4 and LAMA2) from pre-implantation toward post-implantation at placentation sites appears to be associated with softening of the tissue in preparation for trophoblast invasion. The further decrease of these components at placentation sites at the time of prepartum luteolysis seems to be associated with preparation for the release of fetal membranes. Reflecting a high degree of communication, intercellular cell adhesion molecules are induced following placentation (Cx26) or increase gradually toward prepartum luteolysis (Cx43). The spatio-temporal expression of TIMPs suggests their active involvement in modulating fetal invasiveness, and together with ECM1, they appear to protect deeper endometrial structures from trophoblast invasion. With this, the dog appears to be an interesting model for investigating placental functions in other species, e.g. in humans in which Placenta accreta appears to share several similarities with canine subinvolution of placental sites (SIPS). In summary, the canine uterine ECM is only moderately modified in early pregnancy, but undergoes vigorous reorganization processes in the uterus and placenta following implantation.

Integrins functioning in uterine endometrial stromal and epithelial cells in estrus

Here, as a basic study in the construction of a non-cellular niche that supports artificial organization of three-dimensional endometrial tissue, we defined the types of integrin heterodimers that are expressed transcriptionally, translationally and functionally in endometrial stromal (ES) and endometrial epithelial (EE) cells isolated from the mouse uterus in estrus. Gene and protein expression of integrin subunits were analyzed at the transcriptional and translational level by real-time PCR and fluorescent immunoassay, respectively. Moreover, the functionality of integrin heterodimers was confirmed by attachment and antibody inhibition assays. Itga2, Itga5, Itga6, Itga9, Itgav, Itgb1, Itgb3 and Itgb5 in ES cells, and Itga2, Itga5, Itga6, Itga7, Itga9, Itgav, Itgb1, Itgb3, Itgb4, Itgb5 and Itga6 and in EE cells showed significantly higher transcriptional levels than the other integrin subunits. Furthermore, translational expression of the total integrin α and β subunit genes that showed increased transcription was determined in ES and EE cells. ES cells showed significantly increased adhesion to collagen I, fibronectin and vitronectin, and functional blocking of integrin α2, α5 or αV significantly inhibited adhesion to these molecules. Moreover, EE cells showed significantly increased adhesion to collagen I, fibronectin, laminin and vitronectin, and functional blocking of integrin α2, α5, α6 or αV significantly inhibited adhesion to these molecules. Accordingly, we confirmed that integrin α2β1, α5β1, αVβ1, αVβ3 and/or αVβ5, and integrin α2β1, α5β1, α6β1 and/or α6β4, αVβ1, αVβ3 and/or αVβ5, actively function on the surface of ES and EE cells from mouse uterus in estrus phase, respectively.

Anti-laminin-1 antibodies in serum and follicular fluid of women with Hashimoto's thyroiditis undergoing in vitro fertilization

The aim of this study is to evaluate the presence of anti-laminin-1 antibodies (aLN-1) in sera and follicular fluid (FF) of infertile women affected by Hashimoto's thyroiditis (HT) undergoing in vitro fertilization (IVF) and its impact on oocyte maturation and IVF outcome. aLN-1 were measured by a home-made enzyme linked immunosorbent assay (ELISA) in: (1) sera and FF from 44 infertile women affected by HT (HTIW) with tubal factor or male factor as primary cause of infertility; (2) in sera and FF from 28 infertile women without HT, with tubal factor or male factor as cause of infertility (infertile controls-ICTR); and (3) in sera from 50 fertile women (FW). aLN-1 serum levels were significantly higher in HTIW when compared with both fertile women and ICTR (P <0.001and P <0.01, respectively). Assuming as cutoff the 99th percentile of values obtained in sera of FW, 43.2% of HTIW and 3.6% of ICTR were aLN-1 positive (P = 0.0001). Also aLN-1 detected in FF from HTIW were significantly higher in comparison with those found in FF of ICTR (P = 0.006). In HTIW, metaphase II oocyte count showed inverse correlation with both serum and FF aLN-1 levels (r = 0.34, P = 0.02 and r = 0.33, P = 0.03, respectively). Implantation and pregnancy rates were significantly lower in HTIW (7.9% and 9.1%, respectively) when compared with ICTR (23% and 31.1%, respectively) (P = 0.015 and P = 0.03, respectively). Our results demonstrated for the first time the presence of aLN-1 in a relevant percentage of HTIW and suggest that these auto-antibodies may impair IVF outcome.

Extracellular matrix remodelling in rat endometrium during early pregnancy: the role of fibronectin and laminin

The endometrial extracellular matrix (ECM) remodelling has a crucial role in the establishment of a successful pregnancy. In addition to its basic function such as regulation of cell function, differentiation, migration, proliferation, the substantial alterations in the endometrial ECM may play a specific role in the trophoblast invasion, placentation, cell death and formation of the proper and functional implantation chamber around the embryo. In the present study, immunolocalizations of fibronectin and laminin were determined using avidin-biotin complex-peroxidase in rat implantation sites during 7-10 days of pregnancy. Both proteins were present in the basal membrane of blood vessels and in decidual matrix whereas they were absent or had very weak reactivity in the primary decidual zone on day 7. When placentation has begun, the immunoreactivity of both proteins was increased in the placental bed and in the basal membrane of blood vessels of the mesometrial region. The immunolocalization of both proteins seemed to be decreased in the antimesometrial decidua, however, it was increased in the mesometrial decidual matrix on days 9 and 10. Therefore, it could be suggested laminin and fibronectin demonstrating dynamic expressions in relation with the morphological differentiation of endometrial stroma may play crucial roles in the control of trophoblast adhesion and invasion, in placentation and angiogenesis, in the determination of cell shape and fate thus contributing the endometrial receptivity and a successful pregnancy.

Distribution of laminin, vimentin and desmin in the rat uterus during initial stages of implantation

The aim of this study was to investigate the immunohistochemical distribution of laminin, vimentin and desmin during the implantation period in the rat since ECM remodelling and the expression of intermediate filaments (Ifs) is essential for successful decidualization and implantation. On day 4 of pregnancy, laminin was found in a few endometrial stromal cells (ESC), the basement membrane of the numerous endometrial blood vessels, in endometrial glands and as well as in the uterine epithelium. The localization of vimentin on day 4 of pregnancy was widespread in the ESC. However, desmin immunoreactivity was low in ESC on this day of pregnancy. On day 6 of pregnancy, laminin and vimentin were localized in the decidual area underlying luminal epithelium and around the implanting embryo. Additionally, desmin was found to be present densely in decidual cells of the anti-mesometrial region where implantation takes place. Finally, on day 8 of pregnancy, laminin was present in decidual and parietal endodermal cells, whereas vimentin was immunolocalized in primary and secondary decidual regions in the endometrium. In contrast, desmin was detected in some parts of the secondary decidual zone. In conclusion, these proteins could have crucial roles in decidualization and implantation.

The p67 laminin receptor identifies human erythroid progenitor and precursor cells and is functionally important for their bone marrow lodgment

The laminins are a group of extracellular matrix proteins with constitutive expression in all tissues, including bone marrow stroma. A functional role for the nonintegrin laminin receptor p67 has been described for cancer metastasis and lymphocyte trafficking. Expression of p67 was also reported for other subsets of mature leukocytes and for malignant hematopoietic or nonhematopoietic cells. We explored p67 expression on normal hematopoietic progenitor cells (HPCs) and its putative role in bone marrow retention of transplanted HPCs. We found p67 expression on a subset of primary human CD34(+) cells coexpressing erythroid markers. Of importance, p67 recognizes early erythroid progenitors, since sorted p67(+) cells were significantly enriched for burst-forming units-erythroid (BFU-Es) and depleted of colony-forming units--granulocyte/macrophage (CFU-GMs). Blockade of p67 binding of donor cells, using antifunctional antibody, reduced bone marrow homing of BFU-Es. These studies identify p67 as a novel phenotypic marker for erythroid HPCs of functional importance for lineage-specific homing/retention among adult transplanted HPCs.

Laminin-induced signaling in tumor cells: the role of the M(r) 67,000 laminin receptor

The expression of the M(r) 67,000 laminin receptor, a nonintegrin laminin receptor, was found to be up-regulated in neoplastic cells and to directly correlate with invasion and metastatic potential. In the present study, we investigated the role of laminin receptor in mediating laminin effects and the involvement of the mitogen-activated protein kinases (MAPK) cascades and dual-specificity phosphatases in laminin signaling in human melanoma cells. Using stable transfection of A375SM melanoma cells, we established lines expressing reduced or elevated laminin receptor. The antisense-transfected cells demonstrated reduced attachment to laminin and reduced invasion through Matrigel-coated filters. In addition, both matrix metalloproteinase-2 (MMP-2) mRNA expression and activity were significantly reduced in the antisense-transfected cells. Antisense-transfected cells showed a reduction in mRNA level of the alpha6B integrin subunit isoform, whereas no change in the mRNA level of the alpha6A isoform was observed. We found that exogenous laminin reduced the phosphorylated (active) form of extracellular signal-regulated kinase, c-Jun NH(2)-terminal protein kinase, and p38 in all of the cells, irrespective of the expression of the laminin receptor. Furthermore, the phosphorylation of extracellular signal-regulated kinase, c-Jun NH(2)-terminal protein kinase, and p38 was significantly higher in the cell lines expressing reduced laminin receptor, regardless of the exposure to exogenous laminin. This increase of MAPK phosphorylation was accompanied by a significant reduction in MKP-1 phosphatase mRNA level and a significant increase in PAC-1 phosphatase mRNA level. In conclusion, our results confirm the involvement of the laminin receptor in different mechanisms related to tumor dissemination and provide first evidence of the involvement of MAPK and dual-specificity phosphatases in its signal transduction pathway.

Effects of leukaemia inhibitory factor on embryo implantation in the mouse

Leukaemia inhibitory factor (LIF) is a pleiotrophic cytokine. Recent reports indicate that LIF is relevant to murine embryo implantation. In this work, results of indirect immunofluorescence under a confocal microscope illustrated that LIF was mainly located in the uterine lumen and uterine epithelial cells in pregnant mice on day 4. The number of embryos implanted in pregnant mice on day 8 decreased significantly after injection of 3 microg LIF antibodies into a uterine horn (P<0.001), which demonstrated again that LIF is a critical factor for embryo implantation. In a co-culture system, LIF (0.1 ng/ml, 1 ng/ml, 10 ng/ml and 100 ng/ml) significantly enhanced the blastocyst outgrowth after 24, 48 or 72 h of co-culture, and outgrowth areas after 72 h of co-culture. Conversely, 5 microg/ml and 10 microg/ml, but not 1 microg/ml, LIF antibodies decreased the percentage of blastocysts with outgrowth; only 10 microg/ml LIF antibody inhibited blastocyst outgrowth area significantly (P<0.001). However, neither LIF nor its antibodies changed embryo attachment. Analysis of correlation showed that the effects of LIF or its antibodies on the blastocyst outgrowth were dose-dependent. In summary, different pathways may exist to regulate the blastocyst attachment and outgrowth on a monolayer of uterine epithelial cells. LIF protein from the maternal uterus exerts an essential role in embryo implantation in the mouse, which is mediated by stimulating trophoblast outgrowth, but not by promoting the attachment.