Approach for differentiating trophoblast cell lineage from human induced pluripotent stem cells with retinoic acid in the absence of bone morphogenetic protein 4.

INTRODUCTION

Placental transport is the first step in chemotherapeutic safety evaluations during pregnancy. However, a well-established in vitro model is not available. We previously reported that a trophoblast layer model using differentiating choriocarcinoma JEG-3 cells (DJEGs) can be used for placental drug transport studies. However, it was necessary to increase the similarities between the syncytiotrophoblast, the main layer of the placental barrier, and the in vitro evaluation model in order for the model to be useful for placental drug transport evaluations. We focused on in vivo similarities of differentiating induced pluripotent stem cells (iPSCs). iPSCs can achieve a syncytiotrophoblast-like form and secrete human chorionic gonadotropin (hCG) following bone morphogenetic protein 4 (BMP4) treatment. However, BMP4-treated iPSCs can differentiate into several cell types. In the placental transport model, a dense syncytiotrophoblast cell layer is necessary for appropriate differentiation.

METHODS

The conditions permitting differentiation of iPSCs into syncytiotrophoblasts with retinoic acid (RA) treatment without BMP4 were investigated. The presence of syncytiotrophoblast-like cells was confirmed by measurement of mRNA expression levels of breast cancer resistance protein (BCRP) and paternally expressed 10 (PEG10) in syncytiotrophoblasts. In addition, immunofluorescence imaging of cytokeratin 7 (CK7) induced in trophoblasts was performed.

RESULTS

and Discussion: RA-induced iPSCs exhibited these syncytiotrophoblast-like features and hCG secretion was maintained for at least 28 days after treatment with RA (500 nM) without BMP4. These results suggest that RA-induced iPSCs are a suitable in vitro syncytiotrophoblast model that can be used as an indicator of drug placental transport for pharmacotherapy during pregnancy.