| Summary: | There is increasing evidence to suggest that activin can function as
an autocrine/paracrine regulator in various tissues, including the
reproductive system. At the cellular level, activin acts via a family of
activin receptor (ActR) subtypes which includes two type I (ActRI and
ActRLB) and two type II (II and ILB) receptors. The role of activin in the
human placenta is not clearly understood. In this study, the detection of
inlubin/activin subunit and ActRI mRNA were examined in first trimester
cytotrophoblasts, term cytotrophoblasts, extravillous trophoblast (EVT)
cells, immortalized extravillous trophoblast (LEVT) cells, JEG-3 cells,
decidual tissue, and decidual cells. Regulation of ActRI mRNA levels was
also studied in LEVT cells using competitive polymerase chain reaction
(cPCR).
With the exception of JEG-3 cells, ActRILB mRNA was detected in
all cell populations, mRNA transcripts encoding inhibina, inhibinRA,
inhibinpB, ActRI, ActRII and ActRILB were detected in the whole cell
populations. However, ActRLB mRNA could not be detected in all cell
populations.
With Northern blot hybridization analysis, it was found that the
ActRI mRNA level was greatest in first trimester EVT cells followed in
decreasing order of first trimester cytotrophoblasts, JEG-3 cells and term
cytotrophoblasts.
An internal standard of ActRI cDNA for cPCR was constructed for
the precise quantitation of the ActRI mRNA levels in LEVT cells. The
ActRI mRNA accumulation was stimulated in a dose-dependent manner by activin-A with a maximal effect three times that of control culture at a
dose of 10 ng/ml activin-A. The time course of the activin-A effects on
ActRI mRNA levels showed an early response with the maximal increase
at 6 hours. The effects of follistatin, an activin binding protein, with and
without the concomitant presence of activin-A, were also examined.
Follistatin had no effect on ActRI mRNA levels in the absence of activin-
A. Co-treatment of activin-A and follistatin demonstrated the blocking
effect of follistatin on activin-A with dose dependent manner.
This study provides evidence for the first time that activin-A and
follistatin modulate the ActRI mRNA levels in an autocrine/paracrine
manner in human placental trophoblast cells. === Medicine, Faculty of === Obstetrics and Gynaecology, Department of === Graduate
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