Mol. Hum. Reprod. Advance Access originally published online on April 18, 2006
Molecular Human Reproduction 2006 12(8):491-495; doi:10.1093/molehr/gal019
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Possible involvement of crosstalk cell-adhesion mechanism by endometrial CD26/dipeptidyl peptidase IV and embryonal fibronectin in human blastocyst implantation
Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, Nagoya, Japan
1 To whom correspondence should be addressed at: Infertility Center, Toyohashi Municipal Hospital, 50 Hakken-Nishi, Aotake-cho, Toyohashi, Aichi 441-8570, Japan. E-mail: kotobuki{at}se.starcat.ne.jp
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Abstract |
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When human blastocysts hatch through the zona pellucida, gaining the ability to adhere to the endometrium, crosstalk between the embryo and the uterus may represent a successful outcome of their synchronized development and differentiation. CD26/dipeptidyl peptidase IV is known as a marker molecule of the implantation phase endometrium. To study the role of CD26 in implantation, 35 human hatched blastocysts were prepared by enzymatic treatment of expanded blastocysts that had been grown on schedule from frozen–thawed surplus embryos at the 2- or 4-cell stage. The blastocysts were placed on CD26-overexpressing or mock-transfected control monolayer cell cultures. The CD26-overexpression caused significantly higher blastocyst adhesion rate (53.3% versus 25.0%, P < 0.05) and significantly larger outgrowth area of trophectoderm (1.7-fold, P < 0.05). The second part of the present study was to show the expression of fibronectin, a CD26 ligand, in human preimplantation embryos, using the same donated resources. Fibronectin mRNA was detected by RT-PCR from the single hatched blastocyst (2/2) and from the single early blastocyst (3/6) but not from the single morula (0/5) samples. An indirect immunofluorescence technique verified the localization of fibronectin on the surface of the blastocyst. These results indicate that the adhesion mechanism by endometrial CD26 and embryonal fibronectin may be involved in human blastocyst implantation.
Key words: blastocyst/CD26/cell adhesion/fibronectin/implantation
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Introduction |
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Implantation is the first maternal–embryo crosstalk that only occurs during a restricted period called the ‘implantation window’ or ‘nidation window’. The molecular basis of the crosstalk during the implantation window remains to be defined. After finishing preimplantation processes including hatching or the shedding of the zona pellucida, the first implantation process of apposition may occur. Apposition describes the orientation of the blastocyst towards the endometrial surface epithelium. Although this phase varies among species (Wimsatt, 1975
) and there are no available data on apposition in humans, it is probable that the blastocyst may come in contact with high-molecular-weight proteins on the endometrial cell surface. The second implantation process is the attachment of the blastocyst to the endometrial cell surface. As the possible adhesion molecules are associated with nidation, temporary expression of integrin 
vß3 (Lessey et al., 1992), CD26/dipeptidyl peptidase (DPP) IV (Imai et al., 1992), heparin-binding epidermal growth factor (Das et al., 1994), trophinin (Fukuda et al., 1995) and the L-selectin ligand (Genbacev et al., 2003) has been reported in the implantation phase endometrium in women or in animals. However, direct evidence has not been shown in the previous studies using human embryos.
CD26/DPP IV is a 110-kDa membrane-bound extracellular glycoprotein that is highly expressed on the endometrial epithelium during the implantation period in women (Imai et al., 1992). CD26 has been reported as an adhesion molecule that requires cell-surface associated fibronectin (Cheng et al., 1998). Here, we have investigated whether CD26 on the cell surface increased hatched blastocyst adhesion in vitro. Moreover, we have also studied the expression of fibronectin in the human implanting embryos.
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Materials and methods |
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Embryos
Embryos were donated with written informed consent by infertile patients treated in the IVF Centre at Nagoya University Hospital under the approval of the Review Board and Ethics Committee of Nagoya University School of Medicine. These embryos could be used for research purposes for the following reasons: divorce, death of a spouse, live birth after sibling embryo transfer, loss of the uterus, and two years’ passing after oocyte retrieval. Thereby, a total of 205 surplus frozen embryos at the 2- to 4-cell stage were used in the current study. Preceding IVF and cryopreservation were performed by standard protocols. All embryos had siblings in the same cohort with normal development.
Embryo thawing
Frozen embryos were thawed (defined as day 0) using a commercial embryo-thaw kit (Thawing pack, MediCult a/s, Jyllinge, Denmark) according to the manufacturer’s instructions. Briefly, the embryos were removed from liquid nitrogen and incubated at room temperature for 30 s and then in a 30°C water bath for 1 min. The embryos were incubated at room temperature first in Solution I (1.0 M propanediol and 0.2 M sucrose) for 5 min, in Solution II (0.5 M propanediol and 0.2 M sucrose) for 5 more minutes and in Solution III (0.2 M sucrose) for next 10 min. Finally, the embryos were incubated in PBS with 25 mg/ml human serum albumin at room temperature for further 10 min.
Embryo culture
Embryos were grown to the 8-cell stage in HTF Medium (Irvine Scientific, Santa Ana, CA, USA) supplemented with 10% (v/v) Serum Substitute Supplement (SSS; 6 mg/ml therapeutic-grade human serum albumin and 1 mg/ml globulins; Irvine Scientific), and thereafter in G2.3 Medium (Scandinavian IVF Science Products, Gothenburg, Sweden) supplemented with 10% (v/v) SSS. In the morning of day 4, 35 embryos, reaching the expanded blastocyst stage, were used for the adhesion assay. These blastocysts were treated with protease according to the method described elsewhere (Fong et al., 2001) with minor modifications. Briefly, blastocysts were exposed to 10 IU/ml Pronase P8811 (Sigma, St. Louis, MO, USA) in G2.3 medium at 37°C in 5% CO2, 5% O2 and 90% N2 for 1.5 min to remove the zona pellucida. The incubation time was slightly extended if the zona pellucida of the blastocysts had not dissolved at the end of the treatment. The zona-free blastocysts were washed four times in G2.3 medium before starting the adhesion assay. Some morphologically normal embryos that had grown on schedule, including five morulae, six pre-hatching or early blastocysts and two hatched blastocysts, were used for the RT-PCR experiment as described below. Each single embryo was used as one sample. Enzymatic removal of the zona pellucida was not performed for this purpose. Moreover, four hatched blastocysts and five morulae that had grown on schedule were used for the immunofluorescent staining.
Plasmid construction and transfection
An endometrial carcinoma cell line, AMEC (generously donated by Aichi Medical University, Japan) (Yabushita et al., 1996), was maintained in RPMI-1640 (Sigma) supplemented with 10% (v/v) FCS (Sigma) and penicillin-streptomycin. Cells were incubated at 37°C in a humidified atmosphere of 5% CO2. Full-length cDNA for CD26 was kindly provided by Dr Y. Ikehara (Fukuoka University, Fukuoka, Japan). A cell line that overexpresses CD26 was established as previously described (Kajiyama et al., 2002). In brief, the eukaryotic expression vector pcDNA 3.1 (–) (Invitrogen Japan, Tokyo, Japan) was used to derive the expression of the inserted CD26 cDNA. Transfections were carried out using Lipofectamine (Life Technologies, San Diego, CA, USA) according to the manufacturer’s instructions. AMEC cells were transfected with pcDNA3.1 (–) (AMpcDNA) or pcDNA3.1 (–) with CD26 cDNA inserted. Stable transfectants were selected by growth in media supplemented with 400 µg/ml of G 418 (Sigma). Several hundred clones resistant to G 418 were obtained. Two independent monoclonal cells (AMCD26A, AMCD26B) from these transfectants were used in the following experiments.
Western blot analysis
AMCD26A, AMCD26B or AMpcDNA cells in confluent monolayer on a 10-cm dish were homogenized using a motor-driven Teflon pestle for 10 min on ice in PBS extraction buffer containing 1% (v/v) Triton X-100 and protease inhibitors (1 mM phenylmethylsulfonyl fluoride, 1 µg/ml aprotinin, 10 µg/ml leupeptin). Cell debris and nuclei were removed by centrifugation at 15 000 x g for 30 min at 4°C. Protein concentrations were determined using a protein assay kit (Bio-Rad Laboratories, Hercules, CA, USA). Immunoblot analysis was carried out according to the method reported previously (Towbin et al., 1979) with some modifications. Briefly, 10 µg of protein extract was separated by SDS-7.5% PAGE, transferred onto a nitrocellulose membrane and immunoblotted with anti-CD26 monoclonal antibody (Pharmingen, San Diego, CA, USA) at a dilution of 1 : 100. A biotinylated secondary antibody specific to mouse IgG (Santa Cruz Biotechnology, Santa Cruz, CA, USA) was used at a dilution of 1 : 1000. Immunoreactive proteins were stained using a chemiluminescence kit (ECL: Pharmacia Biotech, Buckinghamshire, UK).
Flow cytometric analysis
Fluorescence-activated cell sorting (FACS) was carried out to quantify the expression levels of CD26 on the cell surface of AMEC. A hundred thousand cells were incubated with phycoerythrin-conjugated monoclonal antibody specific for CD26 (Pharmingen, San Diego, CA, USA) for 30 min at 4°C and washed three times with PBS. FACS data were acquired on a FACS Calibur (Becton Dickinson, San Jose, CA, USA) and analysed using CELL Quest software (Becton Dickinson).
Assays for blastocyst adhesion and spreading evaluation
Blastocyst adhesion and spreading assays were conducted using confluent monolayer culture on 6-cm plastic dishes in RPMI-1640 supplemented with 10% FCS. Hatched blastocysts were randomly allocated into the study (AMCD26A) and the control (AMpcDNA) group. Only the confluent monolayer cultures were co-cultured at 37°C in 5% CO2 in air for 72 h. Eleven independent experiments were performed. To assess the blastocyst adhesion, a small amount of medium was gently flushed on each blastocyst by means of a glass pipette pulled to a very fine bore. Blastocysts that showed no movement during observation under an inverted phase-contrast microscope (Olympus, Tokyo, Japan) were considered to have adhered. Measurements of blastocyst adhesion were made at 24, 48 and 72 h. To determine the extent of spreading, the adhered blastocysts were photographed at a magnification of 200x using a digital camera (Olympus). The area of spreading was measured using a Windows PC with Photoshop 5.5J software (Adobe Systems, San Jose, CA, USA). It was not difficult to trace the border of the spreading area using digital magnification on PC. The same observer (Y.S) produced each tracing without information of the photograph. The final value for each photograph was calculated from the average of three tracings. The spreading of the trophectoderm was determined at 72 h of co-culture.
RT-PCR analysis of fibronectin mRNA in preimplantation embryos
Total RNA from a single embryo was extracted with an RNeasy® Mini Kit (QIAGEN, Valencia, CA, USA) according to the manufacturer’s protocol. RT-PCR was carried out with an RNA-PCR kit (Perkin-Elmer, Norwalk, CT, USA) according to the manufacturer’s protocol. The gene-specific primers used for fibronectin were 5'-GCGACAGGACGGACATCTTTG-3' (sense) and 5'-CGTCCCAGTCTCTGAATCCTG-3' (anti-sense) and for GAPDH were 5'-TGAAGGTCGGTGTCAACGGA-3' (sense) and 5'-GATGGCATGGACTGTGGTCAT-3' (anti-sense) according to the previous report (Koenig et al., 2003). PCR consisted of 40 cycles at 94°C for 1 min, at 62°C for 90 s and at 72°C for 2 min. The RT-PCR amplified samples were visualized on 1.5% agarose gels using ethidium bromide.
Immunofluorescent staining
Only 6- and 7-day-old naturally hatched blastocysts and morulae that had grown on schedule were used. The zona pellucida of the morula was removed by Pronase as described above. These embryos were stained using an indirect immunofluorescent technique essentially as described elsewhere (Morin and Sullivan, 1994). In brief, embryos were washed with 0.4% (w/v) bovine serum albumin fraction V (BSA; Sigma) in Dulbecco’s phosphate buffered saline (DPBS; pH 7.4; Gibco), fixed with 3% (w/v) formaldehyde in DPBS overnight at 4°C, washed with DPBS and incubated for 1 h in 4% (w/v) BSA in DPBS. Then, the embryos were incubated for 1 h at 37°C in the presence of anti-fibronectin monoclonal antibody (Chemicon; Temecula, CA, USA) diluted 1 : 100 in DPBS supplemented with 1% (w/v) BSA. After extensive washing in DPBS supplemented with 1% BSA, components were incubated for 1 h at 37°C in the dark in the presence of fluorescein isothiocynanate (FITC) conjugated goat anti-mouse IgG (Invitrogen, Carlsbad, CA, USA) diluted 1 : 100 in DPBS supplemented with 1% BSA. Following incubation in the presence of the second antibody, embryos were washed five times in DPBS supplemented with 1% BSA and mounted on gelatinized slides. For negative control experiments, incubation with the goat anti-fibronectin antibody was omitted.
CD26-overexpressing or mock-transfected AMEC cells that had been cultured on a glass coverslip for 3 days were rinsed gently with DPBS (pH 7.4) and then fixed for 30 min in 4% paraformaldehyde in 0.1 M DPBS. AMEC cells were rinsed in DPBS supplemented with 1% BSA and incubated in 0.2% Triton X-100 with 0.1 M sodium phosphate buffer (pH 7.4) for 10 min at room temperature. After rinsing three times, AMEC cells were blocked with 4% BSA in PBS for 1 h at room temperature. After rinsing further three times, AMEC cells were incubated overnight at 4°C in the presence of the anti-fibronectin monoclonal antibody diluted 1 : 100 in PBS supplemented with 1% BSA. After rinsing three times, AMEC cells were incubated for 1 h in the dark in the presence of FITC conjugated goat anti-mouse IgG diluted 1 : 100 in PBS supplemented with 1% BSA. Negative control experiments were performed as described above.
Immunofluorescent staining was observed using an Olympus IX70 inverted microscope equipped with a mercury lamp (50 W) and filters for specific FITC fluorescence including an excitation filter BG 12 and KV 418 nm, diachronic mirror 500 nm (transmission) and barrier filter OG 515. Photographs were taken using an ORCA-ER camera (Hamamatsu Photonics K. K., Hamamatsu, Japan).
Statistical analysis
The area of embryo spreading was expressed as the mean ± SEM. Mann–Whitney’s U-test was applied to examine statistical significance. Differences were considered statistically significant at P < 0.05.
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Results |
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To confirm the expression of CD26 by the clones, Western blot analysis and FACS analysis were performed (Figure 1). Only AMCD26A was used in the following embryo implantation experiments due to the limitations of the use of human embryos in the current study.
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Hatched blastocysts adhered to the monolayer cells of AMCD26A within 24 h (Figure 2A and B), while those that failed to adhere floated in the culture medium. Blastocysts that adhered to AMCD26A exhibited extensive outgrowth thereafter (Figure 2C and D).
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The effect of CD26 on the blastocyst adhesion and the outgrowth of trophectoderm were evaluated using the CD26-overexpressing (AMCD26A) and the mock-transfected (AMpcDNA) monolayer cell culture. A total of 35 hatched blastocysts were randomly allocated into the study and the control group. Both adhesion of hatched blastocysts and outgrowth of trophectoderm were significantly promoted (53.3% versus 25.0%, n = 8/15 versus 5/20, P < 0.05; 83 670 ± 9447 µm2 versus 49 190 ± 1026 µm2, P < 0.05) on the AMCD26A cultures (Figure 3).
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As fibronectin is one of the most probable ligands involved in CD26-mediated adhesion, we investigated the embryonal fibronectin mRNA expression using RT-PCR. We selected morphologically normal embryos that had grown on schedule, including five morulae, six pre-hatching blastocysts and two hatched blastocysts. Fibronectin mRNA was amplified in 3/6 pre-hatching and 2/2 hatched blastocyst samples but not in 0/5 morula samples (Figure 4, Table I). The AMEC monolayer also expressed fibronectin mRNA (Figure 4).
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To confirm the expression of fibronectin on the cell surface of the hatched blastocyst, three hatched blastocysts and five morulae were tested for fibronectin expression (another one for a negative control) using an indirect immunofluorescent technique. Cell-surface fibronectin was detected in the polar and mural trophectoderm of the hatched blastocysts (Figure 5). In all the samples, the staining covered the entire surface of the blastocysts. However, the morula stage embryos (n = 5) were not stained for fibronectin. Immunoreactive fibronectin on the CD26-overexpressing or the mock-transfected AMEC cells was detected only on the basal surface of the cells (Figure 5).
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Discussion |
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We have demonstrated that human blastocysts adhered more efficiently on the CD26-overexpressing monolayer cell culture. Moreover, fibronectin mRNA was detected at the blastocyst but not at the morula stage in human embryos. Cell-surface fibronectin immunofluorostaining was also detected in the human hatched blastocysts. Our findings of the CD26 adhesion potency using human growing embryos, as well as the fibronectin expression on the hatched blastocysts, may support the existence of CD26 fibronectin adhesion mechanism during the human blastocyst implantation.
Relationship between the adhesion molecule and its ligand is on a molecular basis that does not depend on the species. However, the data from mouse blastocysts should be reconsidered before they are applied to human reproduction, because mouse blastocysts generally show a >90% adhesion rate and a similar hatching rate under regular culture conditions. In contrast, the hatching rate of human blastocysts is <30%, as shown in our previous study (Ando et al., 2000) and is supported in the preliminary data in the present study. Thus, it appears that the hatching process is one of the major limiting factors for the establishment of pregnancy in humans, although the clinical relevance of assisted hatching within an assisted reproduction program remains controversial and elusive (Edi-Osagie et al., 2003). Assisted hatching may not change the lower implantation potentiality of the pre-hatching blastocyst to the level of the hatched blastocyst. In our adhesion assay, we used protease-treated zona-free expanded blastocysts. In this work, we used human embryos that were morphologically and developmentally normal. We started with 193 frozen–thawed embryos at 2- to 4-cell stages, and only 35 expanded blastocysts, 13 embryos, including two hatched blastocysts, and four hatched blastocysts were used for the adhesion assay, RT-PCR and immunofluorescent staining, respectively. Furthermore, we only used embryos where the mother had given birth to a normal child previously. As Bloor et al. (2002) commented, this may be the best obtainable indicator of embryo quality. Therefore, the human embryos with the best quality were used for the fibronectin expression studies, but the zona-free procedure for the adhesion assay was a compromise. Possibly, fibronectin or other CD26 ligands were not expressed or were removed with the zona-free procedure on some of the expanded blastocysts.
The adhesion rate of the control culture was as low as 25.0%. When CD26 was overexpressed, the adhesion rate increased up to 53.3%. Furthermore, the CD26-mediated adhesion had 1.7-fold the trophectoderm spreading. In the implantation processes, adhesion is followed by penetration of the uterine surface epithelium. Penetration has been distinguished into three types, based on the animal species. They are: (i) displacement implantation, which is characterized by apoptosis of the uterine epithelium, is observed in rats and mice; (ii) fusion implantation occurs in rabbits; and (iii) intrusive implantation is found in rhesus monkeys and marmoset monkeys. It has been observed that human blastocysts penetrate the endometrial surface epithelium by intrusive penetration (Bentin-Ley et al., 2000). As the spreading of the trophectoderm on a monolayer culture is a two-dimensional phenomenon, care must be taken in the interpretation of the result.
Polymeric cell-surface fibronectin has been reported to be the principal ligand for CD26 (Cheng et al., 2003) as well as for integrins (Pierschbacher et al., 1981; Pierschbacher and Ruoslahti, 1984). We have found that the human-hatched blastocysts as well as the mouse blastocysts express fibronectin on the trophectoderm (Morin and Sullivan, 1994). The fibronectin-mediated cell–cell and cell–extracellular matrix adhesion mechanism might exist in human blastocyst adhesion in vivo as well as in lymphocyte adhesion and tumour metastasis (Merviel et al., 2001). It is noteworthy that both fibronectin-deficient mice and CD26-deficient mice are fertile (George et al., 1993; Marguet et al., 2000). One possibility is that the CD26 fibronectin adhesion mechanism may be involved in the pathology of implantation failure, which is clinically important, rather than the essential mechanism of implantation in women. The lower expression of endometrial CD26 or embryonal fibronectin during the early process of implantation might produce unfavourable results of the infertility treatment.
Although we have found the fibronectin expression on the surface of human hatched blastocysts, we could not show the simple control or supporting experiments, such as blocking the interaction with anti-fibronectin antibodies or antibodies to other CD26 interaction partners, due to the limitation of human embryos that we could use for the present study. It has been reported that collagen I, adenosine deaminase and CD45 are also CD26 ligands (Bauvois, 1988; Torimoto et al., 1991; Kameoka et al., 1993). Another possibility is that human hatched blastocysts also express CD26 and that one of the CD26 ligands is sandwiched. However, in our preliminary RT-PCR data with a small number of embryos, CD26 mRNA expression has not been found in human blastocysts. It might also be possible that the peptide produced by the blastocysts may be involved in the temporary molecular interaction with endometrial CD26 as a substrate for DPP IV. Further studies are required to elucidate the crosstalk adhesion mechanism that CD26 and/or fibronectin are involved in human implantation.
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Acknowledgements |
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We are grateful for the technical assistance of Hiroko Sato in the immunofluorescent staining. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (H.A.) and by a research grant from Showa-kai, the Alumni of Department of Obstetrics and Gynecology, Nagoya University School of Medicine (H.A.).
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References |
|---|
|
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|---|
Ando H, Kobayashi M, Toda S, Kikkawa F, Masahashi T and Mizutani S (2000) Establishment of a ciliated epithelial cell line from human Fallopian tube. Hum Reprod 15,1597–1603.
Bauvois B (1988) A collagen-binding glycoprotein on the surface of mouse fibroblasts is identified as dipeptidyl peptidase IV. Biochem J 252,723–731.[Web of Science][Medline]
Bentin-Ley U, Horn T, Sjogren A, Sorensen S, Falck Larsen J and Hamberger L (2000) Ultrastructure of human blastocyst–endometrial interactions in vitro. J Reprod Fertil 120,337–350.[Abstract]
Bloor DJ, Metcalfe AD, Rutherford A, Brison DR and Kimber SJ (2002) Expression of cell adhesion molecules during human preimplantation embryo development. Mol Hum Reprod 8,237–245.
Cheng HC, Abdel-Ghany M, Elble RC and Pauli BU (1998) Lung endothelial dipeptidyl peptidase IV promotes adhesion and metastasis of rat breast cancer cells via tumor cell surface-associated fibronectin. J Biol Chem 273,24207–24215.
Cheng HC, Abdel-Ghany M and Pauli BU (2003) A novel consensus motif in fibronectin mediates dipeptidyl peptidase IV adhesion and metastasis. J Biol Chem 278,24600–24607.
Das SK, Wang XN, Paria BC, Damm D, Abraham JA, Klagsbrun M, Andrews GK and Dey SK (1994) Heparin-binding EGF-like growth factor gene is induced in the mouse uterus temporally by the blastocyst solely at the site of its apposition: a possible ligand for interaction with blastocyst EGF-receptor in implantation. Development 120,1071–1083.[Abstract]
Edi-Osagie E, Hooper L and Seif MW (2003) The impact of assisted hatching on live birth rates and outcomes of assisted conception: a systematic review. Hum Reprod 18,1828–1835.
Fong CY, Bongso A, Sathananthan H, Ho J and Ng SC (2001) Ultrastructural observations of enzymatically treated human blastocysts: zona-free blastocyst transfer and rescue of blastocysts with hatching difficulties. Hum Reprod 16,540–546.
Fukuda MN, Sato T, Nakayama J, Klier G, Mikami M, Aoki D and Nozawa S (1995) Trophinin and tastin, a novel cell adhesion molecule complex with potential involvement in embryo implantation. Genes Dev 15,1199–1210.
Genbacev OD, Prakobphol A, Foulk RA, Krtolica AR, Ilic D, Singer MS, Yang Z-Q, Kiessling LL, Rosen SD and Fisher SJ (2003) Trophoblast L-selectin-mediated adhesion at the maternal–fetal interface. Science 299,405–408.
George EL, Georges-Labouesse EN, Patel-King RS, Rayburn H and Hynes RO (1993) Defects in mesoderm, neural tube and vascular development in mouse embryos lacking fibronectin. Development 119,1079–1091.[Abstract]
Imai K, Maeda M, Fujiwara H, Kariya M, Takakura K, Kanzaki H and Mori T (1992) Dipeptidyl peptidase IV as a differentiation marker of the human endometrial glandular cells. Hum Reprod 7,1189–1194.
Kajiyama H, Kikkawa F, Suzuki T, Shibata K, Ino K and Mizutani S (2002) Prolonged survival and decreased invasive activity attributable to dipeptidyl peptidase IV overexpression in ovarian carcinoma. Cancer Res 62,2753–2757.
Kameoka J, Tanaka T, Nojima Y, Schlossman SF and Morimoto C (1993) Direct association of adenosine deaminase with a T cell activation antigen, CD26. Science 261,466–469.
Koenig AL, Gambillara V and Grainger DW (2003) Correlating fibronectin adsorption with endothelial cell adhesion and signaling on polymer substrates. J Biomed Mater Res A 64,20–37.[CrossRef][Medline]
Lessey BA, Damjanovich L, Coutifaris C, Castelbaum A, Albelda SM and Buck CA (1992) Integrin adhesion molecules in the human endometrium. Correlation with the normal and abnormal menstrual cycle. J Clin Invest 90,188–195.[Web of Science][Medline]
Marguet D, Baggio L, Kobayashi T, Bernard AM and Pierres M (2000) Enhanced insulin secretion and improved glucose tolerance in mice lacking CD26. Proc Natl Acad Sci USA 97,6874–6879.
Merviel P, Challier JC, Carbillon L, Foidart JM and Uzan S (2001) The role of integrins in human embryo implantation. Fetal Diagn Ther 16,364–371.[CrossRef][Web of Science][Medline]
Morin N and Sullivan R (1994) Expression of fibronectin and a fibronectin-binding molecule during preimplantation development in the mouse. Hum Reprod 9,894–901.
Pierschbacher MD, Hayman EG and Ruoslahti E (1981) Location of the cell-attachment site in fibronectin with monoclonal antibodies and proteolytic fragments of the molecule. Cell 26,259–267.[CrossRef][Web of Science][Medline]
Pierschbacher MD and Ruoslahti E (1984) Cell attachment activity of fibronectin can be duplicated by small synthetic fragments of the molecule. Nature 309,30–33.[CrossRef][Medline]
Torimoto Y, Dang NH, Vivier E, Tanaka T, Schlossman SF and Morimoto C (1991) Coassociation of CD26 (dipeptidyl peptidase IV) with CD45 on the surface of human T lymphocytes. J Immunol 147,2514–1517.
Towbin H, Staehelin T and Gordon J (1979) Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci USA 76,4350–4354.
Wimsatt WA (1975) Some comparative aspects of implantation. Biol Reprod 12,1–40.[CrossRef][Web of Science][Medline]
Yabushita H, Hirata M, Noguchi M and Nakanishi M (1996) Vitamin D receptor in endometrial carcinoma and the differentiation-inducing effect of 1,25-dihydroxyvitamin D3 on endometrial carcinoma cell lines. J Obstet Gynaecol Res 22,529–539.[Medline]
Submitted on November 8, 2005; accepted on January 19, 2006.
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