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Gernot Desoye, PhD:

Obesity effects on growth of first-trimester trophoblasts

Department of Obstetrics and Gynaecology, Medical University of Graz, Auenbruggerplatz 14, A-8036 Graz;
phone: +43-316-385 84605, fax: +43-316-385 12506,  e-mail
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Keywords:

Inflammation, obesity, trophoblast, oxidative stress, DNA damage, growth, cell cycle, placenta

Research interest:

Early human placental (and embryonic) development occurs in a physiologically low oxygen environment supported by histiotrophic secretions from endometrial glands. The low oxygen tension is the result of trophoblasts plugging the spiral arteries such that only a serum filtrate can reach the intervillous space. Under normal conditions these spiral arteries will only get opened after anti-oxidative defense systems have been adequately developed in the placenta. This will prevent that the oxidative stress associated with the gradual opening of the spiral arteries and the ensuing increase in oxygen tension in the intervillous space will compromise the development of the placenta. Conditions such as pre-eclampsia, maternal diabetes or obesity may put these anti-oxidative defense systems under excessive strain through the accompanying hyperglycemia and / or pro-inflammatory state. In pre-eclampsia the growth arrest and DNA damage-inducible 45 (GADD45) protein, a central stress sensor, is overexpressed and influences trophoblast activity through the p38 MAP kinase pathway (1). It may, thus, also be involved on placental growth impairment found in pre-eclampsia.

One focus of the laboratory has been to understand the effects of maternal diabetes and obesity on placental development and trophoblast proliferation (2). We analysed the first trimester trophoblast transcriptome under normo- and hyperglycemic conditions and found most dysregulated transcripts in the cell-cycle / apoptosis / transcription cluster (Maier A, Hiden U and Desoye G, unpublished). We have further demonstrated that the combination of hyperglycemia and high oxygen levels reduces proliferation of human first-trimester trophoblasts involving MAP kinase (3). This may account for reduced placental growth and, therefore, also for reduced embryonic growth, during the first-trimester of pregestational diabetic or hyperglycemic pregnancies, when the oxygen tension increases. Since inflammation and oxidative stress can also induce DNA damage, which may result in reduced proliferation, we hypothesize that obesity-associated enhanced inflammation early in pregnancy leads to DNA damage of the trophoblasts with ensuing cell cycle arrest until single-strand breaks have been repaired. We further hypothesize that GADD45 plays a crucial role in this process by integrating various input signals (e. g. inflammatory cytokines, changing oxygen levels, oxidative stress) and orchestrating the trophoblast response (e. g. cell cycle arrest, DNA repair) (4). We will dissect the sequence of these events and take into account the sex of the fetus, which may show different stress susceptibility and/or response to environmental stimuli.

Illustrations:

 
Fig. 1: Oxidative and inflammatory stress as promoter and inhibitor of insulin signalling [2]
 
 
Fig. 2: Fluorescence microscopy of mitochondrial superoxide levels in a first-trimester trophoblast model after 3 days under hyperglycemia (HG) [3]

References:

  1. Liu X, Deng Q, Luo X, Chen Y, Shan N, Qi H: Oxidative stress-induced Gadd45α inhibits trophoblast invasion and increases sFlt1/sEng secretions via p38 MAPK involving in the pathology of pre-eclampsia. J Matern Fetal Neonatal Med, 2016; 29(23):3776–3785.
  2. Lappas M, Hiden U, Desoye G, Froehlich J, Hauguel-de Mouzon S, Jawerbaum A: The role of oxidative stress in the pathophysiology of gestational diabetes mellitus. Antioxid Redox Signal, 2011; 15:3061–3100.
  3. Fröhlich JD, Huppertz B, Abuja PM, K├Ânig J, Desoye G: Oxygen modulates the response of first-trimester trophoblasts to hyperglycemia. Am J Pathol, 2012; 180:153–164.
  4. Salvador JM, Brown-Clay JD, Fornace AJ Jr.: Gadd45 in stress signaling, cell cycle control, and apoptosis. Adv Exp Med Biol, 2013; 793:1–19.

Collaborations within the DP-iDP:

  • M. Gauster will instruct the students how to work with placental explants from first trimester of pregnancy.
  • A. Heinemann will help the students to carefully and comprehensively characterize the first trimester trophoblast isolations by FACS analysis.
  • B. Huppertz will teach the students in the histology of first trimester placentas.
  • M. van Poppel will assist the students when they statistically analyze their results by multilevel techniques in which each placenta (for explant studies and trophoblast isolations) will be treated as first level.

Collaborating research groups where PhD students could perform their research stay abroad:

  • G. Burton (Trophoblast Research Center, Institute of Anatomy, University of Cambridge, UK) is the world leading expert in first trimester development of the human placenta and will facilitate the analyses of oxidative stress including endoplasmic reticulum stress in first-trimester placental explants with an imaging system.
  • M. Knoefler (University of Vienna, Austria) is a molecular biologist with a strong focus on development and differentiation of first trimester human trophoblasts. He will provide the molecular tools and help with the transfections of first-trimester placental explants.
  • A. Schaefer (Institute of Molecular Biology, Mainz, Germany) is an expert in GADD45 and will supervise the students in the analyses of GADD45 function on DNA.
  • A. G. Beristain, Department of Obstetrics and Gynecology, The University of British Columbia, Vancouver, Canada, has experience in studying the effect of maternal obesity on the development of the human first-trimester placenta.

Industrial partners:

DANONE nutrition, NL.

Know-how and infrastructure of the research group:

The laboratory of Gernot Desoye has more than 30 years expertise in the field of placental metabolism, growth and development in conditions of maternal overnutrition (diabetes, obesity). In addition to having established procedures to isolate primary trophoblasts from first-trimester human placentas, the laboratory is among the very few worldwide, in which several primary cells are available from term placentas (trophoblasts, macrophages, Tregs, endothelial cells). The laboratory has also generated and fully characterized a first-trimester trophoblast cell line, which is particularly suitable for studies into cell-cycle regulation and DNA damage using overexpression and silencing. Various techniques are being used for a detailed functional analysis of these cells in vitro including proliferation / cell cycle and DNA damage assays. All equipment, which is not available at the Department’s research laboratory, such as flow cytometry, real-time PCR systems, microarray and sequencing facilities, ECIS and multiplexing are available either at the collaboration partners or at the core facilities of the clinical research center.

Scientific concepts and techniques that students will learn in this laboratory:

The DP-iDP students will get background knowledge in early human development and will learn about the effect of diabetes and obesity on this process. They will be taught in placental functions relevant for adequate growth of the human fetus with special emphasis on nutrition and maintenance of placental integrity as well as the different growth and survival strategies of female and male fetuses. The students will learn a wide range of techniques beyond conventional molecular biology and biochemistry techniques. Cell culture work with human primary cells and tissue explants will be a strong focus allowing analyses of DNA repair, cell cycle, apoptosis and proliferation by various methods. The knowledge will be applied to develop strategies on how to delineate signaling pathways with emphasis on stress–response pathways (p38, JNK). The student will use immuno­histo­chemistry combined with morphometry to determine changes associated with graded maternal overweight / obesity on structural components of the placenta as well as on target molecules relevant in stress response, DNA repair and cell-cycle regulation. Signalling pathways will be blocked in the tissue explants and trophoblasts using pharmacological inhibitors. Expression and protein levels GADD45 will be quantified in placental explants of mothers with various degrees of overweight / obesity and silenced / overexpressed to establish its key function as stress sensor and inducer of the DNA repair and cell cycle response.