The effect of fibrin sealant on mouse embryos

Fibrin-mediated growth restriction of early-stage human trophoblasts is switched to growth promotion through fibrinolysis

STUDY QUESTION

Does fibrin promote trophoblast growth in human and mouse blastocysts during early embryo implantation?

SUMMARY ANSWER

Mouse blastocysts were unaffected by fibrin; however, human blastocysts were significantly suppressed by fibrin in trophoblast growth and then switched to growth promotion through increased fibrinolysis with urokinase-type plasminogen activator (uPA) activity.

WHAT IS KNOWN ALREADY

Fibrin(ogen) plays an important role in various physiological processes and is also critical for maintaining feto-maternal attachment during pregnancy. The addition of fibrin to embryo transfer media has been used to increase implantation rates in human ART; however, its mechanism of action' in vitro has not yet been characterized.

STUDY DESIGN, SIZE, DURATION

Vitrified mouse and human blastocysts were warmed and individually cultured in vitro for up to 120 and 168 h, respectively, on a fibrin substrate. Blastocysts were cultured at 37°C in 6% CO2, 5% O2 and 89% N2. Blastocyst development and related fibrinolytic factors were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ICR strain mouse embryos were purchased from a commercial supplier. Human blastocysts were donated with informed consent from two fertility centers. Mouse and human blastocysts cultured on fibrin-coated plates were compared to those on non-coated and collagen-coated plates in vitro. Trophoblast growth and fibrin degradation were assessed based on the cell area and fibrin-free area, respectively. Fibrinolytic factors were detected in supernatants using plasminogen-casein zymography. The fibrinolytic activity of blastocysts was investigated using a selective uPA inhibitor, exogenous uPA, plasminogen activator inhibitor-1 (PAI-1) inhibitor and fibrin degradation products (FDPs). Fibrinolysis-related mRNA expression level was detected using quantitative real-time PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Fibrin did not affect the developmental speed or morphology of mouse blastocysts, and a large fibrin-degrading region was observed in the attachment stage. In contrast, fibrin significantly suppressed the outgrowth of trophoblasts in human blastocysts, and trophoblasts grew after the appearance of small fibrin-degrading regions. uPA was identified as a fibrinolytic factor in the conditioned medium, and uPA activity was significantly weaker in human blastocysts than in mouse blastocysts. The inhibition of uPA significantly reduced the outgrowth of trophoblasts in mouse and human blastocysts. Human blastocysts expressed PLAU (uPA), PLAUR (uPA receptor), SERPINE1 (PAI-1) and SERPINB2 (PAI-2), whereas mouse blastocysts were limited to Plau, Plaur and Serpine1. In a subsequent experiment on human blastocysts, the addition of exogenous uPA and the PAI-1 inhibitor promoted trophoblast growth in the presence of fibrin, as did the addition of FDPs.

LIMITATIONS, REASONS FOR CAUTION

This model excludes maternal factors and may not be fully reproduced in vivo. Donated human embryos are surplus embryos that may inherently exhibit reduced embryonic development. In addition, donated ART-derived embryos may exhibit weak uPA activity, because women with sufficient uPA-active embryos may not originally require ART. The present study used orthodox culture methods, and results may change with the application of recently developed protocols for culture blastocysts beyond the implantation stage.

WIDER IMPLICATIONS OF THE FINDINGS

The present results suggest that the distinct features of trophoblast outgrowth in human blastocysts observed in the presence of fibrin are regulated by a phenotypic conversion induced by contact with fibrin and FDPs. Mouse embryos did not exhibit the human phenomenon, indicating that the present results may be limited to humans.

STUDY FUNDING/COMPETING INTEREST(S)

The present study was supported by the Department of Obstetrics and Gynecology at the Hamamatsu University School of Medicine and Kishokai Medical Corporation. None of the authors have any conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Fibrin glue improves pregnancy rates in women of advanced reproductive age and in patients in whom in vitro fertilization attempts repeatedly fail

OBJECTIVE

To evaluate the possible contribution of fibrin sealant to the ET stage of IVF.

DESIGN

Case-control study.

SETTING

An assisted reproductive technology unit that performed 2,535 treatment cycles from 1996-1997.

PATIENT(S)

All consecutively seen patients who underwent ET from January 1996 to September 1997.

INTERVENTION(S)

All women who underwent ET with the aid of fibrin sealant during the study period were compared with those who underwent standard ET (controls). Thereafter, a case-control study was conducted on the first consecutively seen 174 women who underwent ET with fibrin sealant and a control group that was matched for age and number of previous unsuccessful cycles.

MAIN OUTCOME MEASURE(S)

Patient age, number of previous unsuccessful IVF attempts, number of embryos transferred, and pregnancy rates.

RESULT(S)

During the study period, ET was performed with fibrin sealant in 265 women and by the standard procedure in 1,402 women. Women in the fibrin sealant group were significantly older. The pregnancy rate was not significantly different between the groups in the whole-cohort study (20.4% versus 23.1%), but it was significantly higher in the fibrin sealant group in the case-control study (25.3% versus 14.9%). This also was true when the older women (>35 years) and the women with > or =4 previous failed IVF attempts were analyzed separately (23.2% versus 9.8% and 26.1% versus 13.4%, respectively).

CONCLUSION(S)

The use of fibrin sealant in ET appears to be beneficial in women of advanced reproductive age and in patients in whom IVF attempts repeatedly fail.