Aquaporin 3 expression in human fetal membranes and its up-regulation by cyclic adenosine monophosphate in amnion epithelial cell culture.
OBJECTIVE
The cell membrane water channel protein aquaporins (AQPs) may be important in regulating the intramembranous (IM) pathway of amniotic fluid (AF) resorption. The objective of the present study was to determine whether aquaporin 3 (AQP3) is expressed in human fetal membranes and to further determine if AQP3 expression in primary human amnion cell culture is regulated by second-messenger cyclic adenosine monophosphate (cAMP).


METHODS
AQP3 expression in human fetal membranes of normal term pregnancy was studied by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). To determine the effect of cAMP on AQP3 expression, primary human amnion cell cultures were treated in either heat-inactivated medium alone (control), or heat-inactivated medium containing: (1) SP-cAMP, a membrane-permeable and phosphodiesterase resistant cAMP agonist, or (2) forskolin, an adenylate cyclase stimulator. Total RNA was isolated and multiplex real-time RT-PCR employed for relative quantitation of AQP3 expression.


RESULTS
We detected AQP3 expression in placenta, chorion, and amnion using RT-PCR. Using IHC, we identified AQP3 protein expression in placenta syncytiotrophoblasts and cytotrophoblasts, chorion cytotrophoblasts, and amnion epithelia. In primary amnion epithelial cell culture, AQP3 mRNA significantly increased at 2 hours following forskolin or SP-cAMP, remained elevated at 10 hours following forskolin, and returned to baseline levels by 20 hours following treatment.


CONCLUSIONS
This study provides evidence of AQP3 expression in human fetal membranes and demonstrates that AQP3 expression in primary human amnion cell culture is up-regulated by second-messenger cAMP. As AQP3 is permeable to water, urea, and glycerol, modulation of its expression in fetal membranes may contribute to AF homeostasis.
Wang
Shengbiao
S
Department of Obstetrics and Gynecology, Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Torrance, California 90502, USA. sheng@labiomed.org
Amidi
Fataneh
F
Beall
Marie
M
Gui
Lizhen
L
Ross
Michael G
MG
D000650:Amnion / Q000378:metabolism*; D000653:Amniotic Fluid / Q000378:metabolism; D051400:Aquaporin 3 / Q000096:biosynthesis*; D018929:Cell Culture Techniques; D000242:Cyclic AMP / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006706:Homeostasis; D006801:Humans; D007150:Immunohistochemistry; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
C496027:AQP3 protein, human; D051400:Aquaporin 3; D000242:Cyclic AMP