Glycocalyx Syndecan-1 in Trophoblast Lipid Transport

 描述（由申请人提供）：合体滋养层（STB）具有关键功能，包括向胎儿运输气体和营养物质。母体极低密度脂蛋白（VLDL）是游离脂肪酸（FFA）的重要来源，对胎儿的生长和发育至关重要。VLDL甘油三酯通过STB微绒毛膜（MVM）上表达的脂肪酶水解为FFA，FFA转移至胎儿。然而，或者，母体脂蛋白与STB MVM上的受体相互作用，具有内吞作用和细胞内水解。然而，相对知之甚少的滋养层微绒毛膜上的脂蛋白受体的功能，特别是关于极低密度脂蛋白的运输。胎盘脂质转移的整个系统的破坏会对胎儿的发育产生负面影响。细胞表面硫酸乙酰肝素蛋白聚糖（HSPG），syndecan-1（SDC-1）作为各种大分子货物的受体发挥作用。在肝细胞的微绒毛上，SDC-1介导VLDL和残余脂蛋白的细胞内化。我们的初步数据表明，滋养层细胞同样结合和内化VLDL的HSP依赖性机制，和滋养层细胞表达的SDC-1显着减少先兆子痫妊娠。该R 03建议的假设是滋养层通过HSP依赖性机制结合和内化VLDL，并且SDC-1是影响这种摄取的主要HSP。这将使用培养中的细胞进行测试，主要是1）人HTR-8/SVneo滋养层细胞系（HTR-8）; 2）人Hep 3B肝癌细胞作为SDC-1介导的VLDL摄取的阳性对照;和3）不表达低密度脂蛋白（LDL）受体和不表达SDC-1的人成纤维细胞系（GM 00701），但表达高水平的功能性LRP 1（LDL受体超家族的多功能成员）。目的1，这是建立在我们的初步数据，是为了确定滋养层细胞表面HSPGs的作用，在极低密度脂蛋白结合/摄取。目的2是确定HSPG依赖性VLDL结合/摄取是否主要由SDC-1完成。目的3是排除LRP 1参与VLDL的滋养细胞内化。目的4是测量VLDL结合/吸收胎盘绒毛在外植体培养，比较绒毛与先兆子痫与无并发症的妊娠。这项工作将进一步加深我们对STB处理脂蛋白和HSPG在这方面功能的理解。鉴于胎盘营养转运的重要性，该研究具有重要的临床意义。

 DESCRIPTION (provided by applicant): The syncytiotrophoblast (STB) has critical functions including transport of gases and nutrients to the fetus. Maternal very low-density lipoproteins (VLDL) provide a significant source of free fatty acids (FFA), important for fetal growth and development. VLDL triglycerides are hydrolyzed to FFA by lipases expressed on the STB microvillous membrane (MVM), with FFA transferred to the fetus. Alternatively, however, maternal lipoproteins interact with receptors on the STB MVM, with endocytosis and intracellular hydrolysis. However, relatively little is known about the function of lipoprotein receptors on the trophoblast microvillous membrane, especially with regard to VLDL transport. Disruption of the overall system of placental lipid transfer can have a negative impact on the development of the fetus. The cell surface heparan sulfate proteoglycan (HSPG), syndecan-1 (SDC-1) functions as a receptor for various macromolecular cargo. On microvilli of hepatocytes, SDC-1 mediates cellular internalization of VLDL and remnant lipoproteins. Our preliminary data suggest that trophoblasts likewise bind and internalize VLDL by an HSPG-dependent mechanism, and that trophoblast expression of SDC-1 is significantly reduced in preeclamptic pregnancies. The hypothesis of this R03 proposal is that trophoblasts bind and internalize VLDL by an HSPG-dependent mechanism, and SDC-1 is the primary HSPG effecting this uptake. This will be tested using cells in culture, primarily 1) the human HTR-8/SVneo trophoblast cell line (HTR-8); 2) human Hep3B hepatocarcinoma cells as a positive control for SDC-1 -mediated VLDL uptake; and 3) a line of human fibroblasts (GM00701) that do not express the low-density lipoprotein (LDL) receptor and do not express SDC-1, but express high levels of functional LRP1 (multifunctional member of the LDL receptor superfamily). Aim 1, which builds upon our preliminary data, is to ascertain the role of trophoblast cell surface HSPGs in VLDL binding/uptake. Aim 2 is to determine whether the HSPG-dependent VLDL binding/uptake is primarily accomplished by SDC-1. Aim 3 is to rule out involvement of LRP1 in trophoblast internalization of VLDL. Aim 4 is to measure VLDL binding/uptake by placental villi in explant culture, comparing villi from women with preeclampsia versus uncomplicated pregnancy. The proposed work will further our understanding of lipoprotein handling by STB, and HSPG function in this regard. The research has important clinical implications given the vital importance of placental nutrient transport.