Division of Obstetrics and Gynecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland.
Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland; Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland.
Placenta. 2021 Feb;105:50-60. doi: 10.1016/j.placenta.2021.01.019. Epub 2021 Jan 26.
The uptake of low- and high-density lipoproteins (LDL and HDL) through the LDL receptor (LDLR) and the scavenger receptor class B type I (SR-BI) mediates maternal to fetal cholesterol transfer in syncytiotrophoblast (STB) cells. STB cells deliver cholesterol via cholesterol efflux through the ATP-binding cassette transporters A1 (ABCA1, to ApoA-I), G1 (ABCG1, to HDL), and SR-BI (to HDL). In the human placenta, these proteins are localized in the apical (LDLR, SR-BI, ABCA1) and basal (SR-BI, ABCA1, ABCG1) membrane of STB cells. However, whether these proteins in polarized primary culture models of STB show a similar localization to those in the human placenta is currently unknown.
Primary human trophoblasts (PHT) were isolated from normal placentas and cultured in Transwells® with Matrigel to obtain a polarized STB monolayer, proteins were determined by immunofluorescence and cholesterol efflux determined to different acceptors.
At day 5, LDLR and ABCA1 localized mainly in the apical membrane, ABCG1 in the basal membrane, and SR-BI in both. Cholesterol efflux towards the apical compartment was higher to adult and neonatal HDL compared to ApoA-I. When acceptors were added in the basal compartment, cholesterol was retained in the Matrigel.
Polarized STB monolayers express LDLR, SR-BI, ABCA1 and ABCG1, and their apical/basal localization resembles the one described in human placental tissue. This study confirms the high physiological value and suitability of this model for use in functional studies. Our findings also suggest that ABCA1 and SR-BI participate in cholesterol efflux to the maternal side of the cells.
低密度脂蛋白（LDL）和高密度脂蛋白（HDL）通过 LDL 受体（LDLR）和清道夫受体 B 类 I 型（SR-BI）被摄取，介导合体滋养层（STB）细胞中的母胎胆固醇转移。STB 细胞通过 ABC 转运蛋白 A1（ABCA1，向 ApoA-I）、G1（ABCG1，向 HDL）和 SR-BI（向 HDL）的胆固醇外排来输送胆固醇。在人胎盘组织中，这些蛋白定位于 STB 细胞的顶膜（LDLR、SR-BI、ABCA1）和基底膜（SR-BI、ABCA1、ABCG1）。然而，这些蛋白在极化的 STB 细胞原代培养模型中的定位是否与在人胎盘组织中的定位相似，目前尚不清楚。
从正常胎盘组织中分离出原代人滋养层细胞（PHT），并在 Transwell®与 Matrigel 中培养，以获得极化的 STB 单层，通过免疫荧光法测定蛋白，并测定不同受体的胆固醇外排。
在第 5 天，LDLR 和 ABCA1 主要定位于顶膜，ABCG1 定位于基底膜，而 SR-BI 则同时定位于两者。与 ApoA-I 相比，胆固醇向顶室的外排到成人和新生儿 HDL 更高。当受体添加到底室时，胆固醇被保留在 Matrigel 中。
极化的 STB 单层表达 LDLR、SR-BI、ABCA1 和 ABCG1，其顶/基底定位与在人胎盘组织中描述的定位相似。本研究证实了该模型在功能研究中的高生理价值和适用性。我们的发现还表明，ABCA1 和 SR-BI 参与了胆固醇向细胞母体侧的外排。
