In humans the vast majority of maternal-fetal exchanges of nutrients, toxins or harmful organisms is mediated by the placenta. It is therefore of great importance to our understanding of fetal and neonatal nutritional and health problems to ascertain the mechanisms by which the placental trophoblast selectively absorbs substances from the maternal blood. The experiments encompassed in this proposal will examine various structural and functional aspects of placental trophoblast. An important feature of placental development and function is the differentiation of cytotrophoblast into syncytiotrophoblast, accompanied by the process of cell fusion. At present, little is known about the regulation of this critical, but unusual, transition. In the first specific aim, we will take advantage of our ability to isolate a pure cytotrophoblast population and examine the regulation of trophoblast differentiation in vitro, employing a variety of factors known to affect differentiation in other systems, particularly those few where cell fusion occurs. These agents include EGF, insulin, IGF's, prostaglandins, conditioned media from cultures of placental fibroblasts and macrophages, drugs which perturb the cytoskeleton, and extracellular matrix components. We will determine the extent of syncytium formation by a variety of morphological and biochemical techniques. As the trophoblast undergoes differentiation we will examine changes in the distribution and synthesis of two important proteins expressed on the cell surface, transferrin receptor and EGF receptor, and changes in two important cytoskeletal proteins, cytokeratin and desmoplakin. The latter are of particular interest in a cell system undergoing fusion since rearrangement of the cytoskeleton and disappearance of cell junctions would accompany this transition.
Specific aim two will extend our earlier studies of iron metabolism by trophoblast cells. We will examine the transferrin-mediated uptake of iron and the release of iron at different stages of differentiation. Other studies will examine developmental changes in the regulation of transferrin receptor synthesis and distribution. Related studies will define the role of ferritin in trophoblast iron metabolism by examining its uptake, biosynthesis and release. The third specific aim is to demonstrate the distribution of acidic intracellular compartments in placental villi and in isolated trophoblast cells. Acidic intracellular compartments are important locations of receptor-ligand dissociation and sorting and are also the site of iron dissociation from transferrin. Together these aims should result in significant new information on trophoblast differentiation and function.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD011658-16
Application #
3311636
Study Section
Reproductive Biology Study Section (REB)
Project Start
1978-07-01
Project End
1994-03-31
Budget Start
1992-04-01
Budget End
1993-03-31
Support Year
16
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of California Davis
Department
Type
Schools of Medicine
DUNS #
094878337
City
Davis
State
CA
Country
United States
Zip Code
95618
Douglas, G C; Thirkill, T L; Sideris, V et al. (2001) Chemokine receptor expression by human syncytiotrophoblast. J Reprod Immunol 49:97-114
Douglas, G C; Thirkill, T L; LaSalle, J (2001) Automated quantitation of cell-mediated HIV type 1 infection of human syncytiotrophoblast cells by fluorescence in situ hybridization and laser scanning cytometry. AIDS Res Hum Retroviruses 17:507-16
Douglas, G C; Thirkill, T L; Blankenship, T N (1999) Vitronectin receptors are expressed by macaque trophoblast cells and play a role in migration and adhesion to endothelium. Biochim Biophys Acta 1452:36-45
Thirkill, T L; Douglas, G C (1999) The vitronectin receptor plays a role in the adhesion of human cytotrophoblast cells to endothelial cells. Endothelium 6:277-90
Douglas, G C; Moreira-Cali, P; King, B F et al. (1998) Uptake of 125I-labelled alpha2-macroglobulin and albumin by human placental syncytiotrophoblast in vitro. J Cell Biochem 68:427-35
Douglas, G C; Fazely, F; Hu, J J (1998) Transmission of HIV to the placenta, fetus and mother and implications of gametic infection. J Reprod Immunol 41:321-9
Kennedy, M L; Douglas, G C; King, B F (1997) Effect of iron on transferrin receptor expression by human placental syncytiotrophoblast cells. Reprod Fertil Dev 9:609-16
Fazeley, F; Hu, J; Thirkill, T L et al. (1997) Infection of primary human placental fibroblasts with HIV-1, HIV-2, and SIV. Arch Virol 142:2237-48
Thirkill, T L; Douglas, G C (1997) Differentiation of human trophoblast cells in vitro is inhibited by dimethylsulfoxide. J Cell Biochem 65:460-8
Douglas, G C; Hu, J; Thirkill, T L et al. (1995) Cyclohexylamine inhibits the adhesion of lymphocytic cells to human syncytiotrophoblast. Biochim Biophys Acta 1266:229-34

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