Steady-state levels of aquaporin 1 mRNA expression are increased in idiopathic polyhydramnios.
OBJECTIVE
Polyhydramnios is a condition associated with significant perinatal morbidity. While the exact pathophysiology of this condition is unknown in the absence of obvious anatomic or organic etiologies, impaired intramembranous water transport has been shown. Previous studies from our laboratory have shown that the water channel aquaporin 1 (AQP1) is expressed in human fetal membranes from term pregnancies with normal amniotic fluid (AF) volume. Therefore, we hypothesized that in pregnancies with idiopathic polyhydramnios, AQP1 expression might be reduced in fetal membranes from pregnancies with this AF volume disorder.


METHODS
Placentas were collected from women at term (37-40 weeks) who presented with either polyhydramnios (amniotic fluid index [AFI] >24.0 cm) or normal AF volume (AFI 5.0-23.9 cm). Immediately after delivery, the membranes (amnion and chorion) directly overlying the placenta and the free-floating reflected membranes were sampled (total of 4 samples from each placenta). RNA was isolated from each sample and expression was quantified using real-time reverse transcriptase polymerase chain reaction (PCR) and relative quantification of gene expression.


RESULTS
Relative to pregnancies with normal AF volume, there was an increase in expression of the water channel AQP1 in all regions of the fetal membranes. The greatest increase (33-fold) was seen in the reflected amnion.


CONCLUSIONS
AQP1 expression is increased in polyhydramnios. This finding suggests that alterations in AQP1 expression may be a compensatory response to and not a cause of idiopathic polyhydramnios. We speculate that therapies focused on regulating AQP1 expression may be useful for treating this condition.
Mann
Stephanie E
SE
Phoenix Integrated Residency in Obstetrics and Gynecology, Maricopa Medical Center, Phoenix, AZ 85008, USA. stephanie_mann@medprodoctors.com
Dvorak
Natalia
N
Gilbert
Heather
H
Taylor
Robert N
RN
D051398:Aquaporin 1 / Q000235:genetics*; D005321:Extraembryonic Membranes / Q000737:chemistry; D005260:Female; D006801:Humans; D010920:Placenta / Q000737:chemistry; D006831:Polyhydramnios / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis*
D012333:RNA, Messenger; D051398:Aquaporin 1