BMI dependent regulation of macrophages and monocytes in pregnancy

Adaptation of the maternal immune system to accommodate the semi-allogeneic
fetus is necessary for pregnancy success. Dysregulation of the maternal immune
adaptation is implicated in reproductive disorders such as infertility,
recurrent miscarriage, fetal growth restriction, and preeclampsia, which
together affect at least 25% of women in the reproductive age. The exact
mechanisms being responsible for fetal tolerance are not known, however T
cells, natural killer (NK) cells, monocytes, and macrophages are all regarded
as important players in the adaptation of the maternal immune response.

Several factors are known to influence pregnancy outcome, including obesity.
During pregnancy, obesity is associated with various unfavorable pregnancy
outcomes, such as: spontaneous miscarriage, congenital anomalies, preeclampsia,
and fetal macrosomia. Thus far, the biological mechanisms behind the
association between obesity and unfavorable pregnancy outcomes are only partly
understood. Possibly, a disturbed maternal immune balance, such as altered
macrophage characteristics are involved in the complicated pregnancy outcomes.
Our previous study indicated altered macrophages subsets in the decidua in
women with a BMI >30.

Whether these cells are functionally altered, or whether macrophage precursor
cells within blood (monocytes) are altered in women with a BMI >30 is not
known. Evidence indicates that the polarization in monocyte subsets is also
dependent on the local tissue environment in which they differentiate. Adipose
tissue produces immune active substances as cytokines and complement factors
which might influence the polarization of monocytes and macrophages. Monocytes
and adipose tissue come in close contact with each other and therefore might
local adipose tissue environments influence systemic monocyte differentiation.
We will analyse this by using flowcytometry, functionality tests and rtPCR on
postpartum placental tissues, maternal peripheral blood and umbilical cord
blood.

We hypothesize that in pregnancies with women with a BMI >30, the maternal
immune system is differently activated (less tolerant) compared to women with a
BMI <25.

Primary Objective: analyse the effect of maternal BMI on levels of macrophage
cell and monocyte subsets in decidual tissue and maternal blood. Secondary
Objective: analyse differences in the effect of maternal blood stimulation with
conditioned medium of adipose tissue and LPS and differences in monocyte
subsets in umbilical cord blood.

This study is an observational study in which levels of monocytes and
macrophages will be analysed. Both pregnant women with a BMI>30 and with a BMI
between 19-25 will be included. Levels of monocyte subsets will be analysed in
maternal blood (obtained around 12 and 30 weeks pregnancy and around delivery,
and umbilical cord blood).

Furthermore, maternal peripheral blood will be stimulated. Adipose tissue for
the stimulation of monocytes will be derived from visceral and subcutaneous
biopsies, taken during caesarean section. Adipose tissue will be cultured for
one day and analysed and supernatant of the conditioned medium will be added to
the monocytes. Monocytes will be cultured consequently for 6 days in the
presence of growth factors which turn the monocytes into macrophages.

Macrophages will be derived from decidual biopts, taken from the placenta after
delivery and from the stimulation of monocytes with adipose tissue. They will
be analysed using multicolour flowcytometry and RT-PCR. Levels and subsets of
macrophages and its deriving cytokines will be analysed.

If possible maternal blood will be taken during routine blood sampling around
12 and 30 weeks of pregnancy and around delivery, and cord blood will be taken
after fetal cord clamping.

Placental sampling does not carry any risk for the women. If possible, maternal
blood will be taken during routine blood sampling and cord blood will be taken
after fetal cord clamping this will not pose any risk on the individuals. The
adipose tissue biopsies will be collected during caesarean sections on tissue
which is already visible during the operation. The adipose tissue retrieval can
cause bleeding of the tissue but this risk is very small and the surgeon
monitors the sampling size while performing the operation. In comparison with
the caesarean section the risk of taken biopsies is negligible. Participation
in this study will not benefit the women personally. However, the present study
investigates the maternal immune system during pregnancy. Knowledge about the
pathogenesis of immune related complications of pregnancy may in the long term
benefit any pregnant woman.