Relaxin causes proliferation of human amniotic epithelium by stimulation of insulin-like growth factor-II.
OBJECTIVE
The study was conducted to determine whether relaxin has a proliferative effect on amniotic epithelial cells and to show that this effect is caused by its stimulation of the insulin-like growth factor-II (IGF-II) gene.


METHODS
Immunolocalization and Northern analysis were used to confirm the expression of IGF-II by the fetal cells in the membranes. Human amniotic epithelial (WISH) cells were treated with doses of IGF-II or human relaxin and their proliferative effects measured. The mechanism of the effect of relaxin on cellular proliferation was studied with the use of an IGF-II-blocking antibody and Northern analysis for IGF-II gene expression after treatment with relaxin. An in vivo correlate was sought by quantitation of relaxin gene expression in 10 fetal membranes from women with normally grown and large for gestational age infants.


RESULTS
The amniotic epithelial and cytotrophoblast cells of the fetal membranes expressed IGF-II, as did the amniotic epithelial-like (WISH) cell line. Treatment of WISH cells with IGF-II or relaxin caused a significant (P <.03) and dose-related increase in WISH cell proliferation over 5 days. The concurrent treatment with a blocking antibody to IGF-II significantly decreased the proliferative response to IGF-II (P <.002) and relaxin (P <.002). Treatment with relaxin caused a significant increase (P <.003) in the transcription of IGF-II in 24 hours. In fetal membranes, the levels of relaxin gene expression correlated with fetal membrane surface area (r = 0.76) and was significantly greater (P <.008) in the membranes from macrosomic infants (4020-4729 g) compared with those normally grown (2855-3830 g).


CONCLUSIONS
IGF-II and relaxin both caused the proliferation of WISH cells. Concurrent treatment with an IGF-II-blocking antibody abrogated the proliferative effects of both hormones. Relaxin increased the transcription of IGF-II, and its expression levels in the fetal membranes correlated with the membrane surface area as well as neonatal birth weight. These data suggest that relaxin is a growth factor for the fetal membranes.
Millar
Lynnae K
LK
Pacific Biomedical Research Center and the Divisions of Cell and Molecular Biology and Obstetrics and Gynecology, University of Hawaii, Honolulu, HI 96822, USA. LynnaeM@apiolani.org
Reiny
Roxanne
R
Yamamoto
Sandra Y
SY
Okazaki
Kristie
K
Webster
Lisa
L
Bryant-Greenwood
Gillian D
GD
D000650:Amnion / Q000737:chemistry / Q000166:cytology*; D000906:Antibodies / Q000494:pharmacology; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D002823:Chorion / Q000737:chemistry; D003656:Decidua / Q000737:chemistry; D004847:Epithelial Cells / Q000737:chemistry / Q000166:cytology; D005260:Female; D005320:Fetal Macrosomia / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007118:Immunoassay; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D010920:Placenta / Q000737:chemistry; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D012065:Relaxin / Q000235:genetics / Q000494:pharmacology*
D000906:Antibodies; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II; D012065:Relaxin