MiPsummer Programme pdf - Mitochondrial Physiology Society

71
Abstract # 40
Linking placental mitochondrial dysfunction and taurine deficiency to development of
pregnancy complications in maternal obesity.
Michelle Desforges
Maternal & Fetal Health Research Centre, University of Manchester, Manchester, UK.
Background: The last decade has seen an alarming rise in the number of obese women of
reproductive age. Maternal obesity increases the risk of developing pre-eclampsia (PE), fetal growth
restriction (FGR) and stillbirth but reasons for this are unclear. Each of these serious pregnancy
complications is associated with increased oxidative stress and placental pathology, particularly in
the outer syncytiotrophoblast (STB) layer and underlying cytotrophoblast (CTB). STB is renewed
to preserve its function as a solute transporting epithelium and endocrine/paracrine organ,
maintaining nutrient delivery to the fetus and producing hormones that sustain pregnancy. STB
renewal occurs by CTB that proliferate, differentiate, and fuse with the multinucleated STB. In PE
and FGR there is reduced CTB proliferation and fusion, and increased CTB apoptosis which leads
to placental insufficiency. Reduced STB taurine transporter (TauT) activity is also a feature of PE
and FGR as well as maternal obesity during the first trimester and at term 1 . In non-placental cells,
taurine protects against damage caused by factors which are elevated in obesity such as
inflammatory cytokines and reactive oxygen species. Emerging evidence suggests taurine’s
cytoprotective role is related to its ability to promote mitochondrial function 2 . Interestingly,
mitochondrial dysfunction has been demonstrated in placentas from PE and FGR 3 . In addition to
supplying cellular energy, mitochondria are involved in a range of processes important for
maintenance and function of STB, such as intracellular signalling, cellular differentiation, and cell
death. This project is beginning to test the hypothesis that reduced placental taurine transport causes
mitochondrial dysfunction which leads to compromised STB renewal and increased susceptibility to
damage, providing a link between maternal obesity and development of pregnancy complications.
Objective: To investigate CTB differentiation and susceptibility of STB/CTB to death and damage
following inhibition of TauT in term human placenta.
Methods: Two in vitro approaches were used: i) STB model: CTB isolated from normal pregnancy
(NP) were maintained in primary culture for 66 hrs during which time they differentiate into
multinucleated STB. TauT was inhibited using siRNA technology. Immunofluorescent staining of
desmosomes allowed visualisation of multinucleation (used to assess differentiation). In parallel
experiments to investigate susceptibility to cell death, prior to fixation at 66 hrs, cells were cultured
overnight +/- the inflammatory cytokine TNF. Apoptosis was measured by presence of cleaved
cytokeratin 18, detected by immunohistochemistry (IHC). ii) Explant model: Placental villous
explants from NP were maintained in culture for 7 days. TauT was inhibited by incubating explants
with the taurine antagonist -alanine. To investigate susceptibility to damage, explants were treated
+/- H 2 O 2 from day 5 and oxidative damage to DNA was assessed by 8-hydroxyguanosine IHC.
Results: siRNA-mediated TauT knockdown in CTBs inhibits their differentiation into
multinucleated syncytia (n=7, p