Analysis of drug transporter expression in syncytiotrophoblast derived from human placental stem cells: Expression and function of efflux transporters

Objective: The placenta is a vital organ for exchanging nutrients, endogenous substances, and xenobiotics between mother and fetus. The syncytiotrophoblast (ST) is crucial in maintaining the placental barrier. Human trophoblast stem cells (hTSCs) have been recently established; however, their utility in studying placental transport functions has not been fully elucidated. This study investigated the expression and function of transporters in hTSC-derived ST cells. Methods: TSCT cells, as hTSCs, were differentiated into ST-like cells (ST-TSCT), and the gene expression of 84 transporters in ST-TSCT cells was evaluated using a PCR array. BeWo cells, a widely used trophoblast model, were used for comparison. BeWo cells were differentiated into ST-like cells using forskolin [BeWo (FK)]. The protein levels of efflux transporters were examined by western blotting, and functional assays were performed using typical fluorescent substrates. Results: Transporter gene expression levels were higher in ST-TSCT than in BeWo (FK) cells, with 27 genes showing more than a 3-fold increase. Ten of these genes were exclusively expressed in ST-TSCT. Western blotting revealed the presence of efflux transporters, including P-glycoprotein (P-gp/ABCB1), breast cancer resistance protein (BCRP/ABCG2), and multidrug resistance-associated protein 2 (MRP2/ABCC2). Furthermore, the accumulation of typical substrates (Rhodamine123 for P-gp, Hoechst33342 and BODIPYTM FL Prazosin for BCRP, and 5(6)-carboxy-2 ',7 '-dichlorofluorescein diacetate for MRP) significantly increased when transporter inhibitors (elacridar, Ko143, and MK571) were applied. Conclusion: This study showed higher transporter expression in ST-TSCT than that in a traditional trophoblast model. Furthermore, the functional expression of efflux transporters was observed. ST-TSCT is valuable for investigating placental transport functions.