Advantages of the outgrowth model for evaluating the implantation competence of blastocysts

Abstract

The implantation process is highly complex and difficult to mimic <i>in vitro</i>, and a reliable experimental model of implantation has yet to be established. Many researchers have used embryo transfer (ET) to assess implantation potential; however, ET with pseudopregnant mice requires expert surgical skills and numerous sacrificial animals. To overcome those economic and ethical problems, several researchers have tried to use outgrowth models to evaluate the implantation potential of embryos. Many previous studies, as well as our experiments, have found significant correlations between blastocyst outgrowth <i>in vitro</i> and implantation in utero by ET. This review proposes the blastocyst outgrowth model as a possible alternative to animal experimentation involving ET in utero. In particular, the outgrowth model might be a cost- and time-effective alternative method to ET for evaluating the effectiveness of culture conditions or treatments. An advanced outgrowth model and further culture of outgrowth embryos could provide a subtle research model of peri- and postimplantation development, excluding maternal effects, and thereby could facilitate progress in assisted reproductive technologies. Recently, we found that outgrowth embryos secreted extracellular vesicles containing specific microRNAs. The function of microRNAs from outgrowth embryos should be elucidated in further researches.

CDX2 downregulation in mouse mural trophectoderm during peri‐implantation is heteronomous, dependent on the YAP‐TEAD pathway and controlled by estrogen‐induced factors

“… 39 , 40 , 41 , 42 In addition, the blastocyst outgrowth assay has been used as an in vitro implantation model. 43 We then cultured E3.5 blastocysts in KSOM with or without 10% FBS for 24, 48, or 72 h after removing ZP, and compared the morphology and CDX2 expression in the mural TE. This revealed that, whereas blastocysts cultured in KSOM maintained an expanded state and never showed outgrowths, blastocysts cultured in KSOM with 10% FBS (KSOM + FBS) developed outgrowths.…”

A New Microfluidic Concept for Successful in Vitro Culture of Mouse Embryos

“…Under optimal loading conditions, microfluidic device culture had no impact on blastocyst cell number and blastomere partitioning between the ICM and TE. Furthermore the blastocysts grown in microfluidic devices demonstrated equivalent capacity for hatching and out growth in vitro, factors which are indicative of implantation potential in vivo [77]. Taken together, these data indicate that the novel microfluidic device presented here is embryocompatible and can successfully be used to support healthy embryo development to the blastocyst stage without the need for media changes or oil overlay.…”

Probing morphological, genetic and metabolomic changes of in vitro embryo development in a microfluidic device

“…Furthermore, the blastocysts grown in microfluidic devices demonstrated equivalent capacity for hatching and out growth in vitro, factors which are indicative of implantation potential in vivo. 78 Taken together, these data indicate that the novel microfluidic device presented here is embryo-compatible and can successfully be used to However, in this work gene expression levels were measured using relative quantification method, which did not allow to obtain information on the absolute expression value for each gene. Further analyses might use absolute quantification methods to measure expression levels of selected genes, to directly compare our findings with available gene expression datasets and elucidate specific impact of the gene alteration on embryo culture.…”