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Abstract
Appropriate growth, development and function of the
placenta is central to the success of nutrient
partitioning between the mother, placenta and fetus.
Hormones such as placental lactogen (PL) and leptin are
produced in the bovine placenta and play an important role
in nutrient partitioning and regulation of placental and
fetal growth. Nuclear transfer pregnancies are associated
with a number of fetal and placental abnormalities,
including increased placental growth and macrosomia, and
hence represent a unique situation to gain insight into
feto-placental growth regulation. We have examined the
expression of bovine PL (bPL) and leptin in placentomes of
artificially inseminated (AI), in vitro produced (IVP) and
nuclear transfer (NT) pregnancies at days 50, 100 and 150
of gestation in the cow. Immunolocalization studies showed
that spatial and temporal patterns of expression of bPL
and leptin were markedly altered in the placentomes of NT
pregnancies compared to AI or IVP controls. Concentrations
of bPL in allantoic fluid, as determined by
radioimmunoassay (RIA), were significantly higher
(P
0.001) in NT pregnancies (17.9 ± 3.2
ng/ml; mean ± sd) compared with AI (2.03 ±
1.5 ng/ml), but not IVP (23.4 ± 12.8 ng/ml)
pregnancies on d150 of gestation. In contrast,
amniotic fluid levels of bPL were significantly decreased
in NT pregnancies at d150 gestation. Leptin mRNA
expression, as determined by real-time RT-PCR, was
increased 2.4-3.0 fold in NT placentomes compared to AI
controls, at all gestational ages examined. We speculate
that the observed dysregulation of expression of bPL and
leptin in NT placentomes could contribute to aberrations
in cell migration and invasion and subsequently to
alterations in placental metabolism and transfer of
nutrients to the fetus, thus leading to increased
placental and fetal macrosomia in NT pregnancies.
Key words:
Female Reproductive Tract •
Pregnancy •
Cytokines •
Growth factors •
Placenta
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