Maternal insulin-like growth factor 1 and 2 differentially affect the renin-angiotensin system during pregnancy in the guinea pig.
OBJECTIVE
Insulin-like growth factors (IGFs) are known to interact with the renin-angiotensin system (RAS). We previously demonstrated that administration of IGF1 to guinea pigs in early to mid pregnancy promotes placental function and fetal growth in mid to late gestation. Early administration of IGF2 had sustained, but not acute, effects on these parameters and also on placental structural differentiation. Here, we aimed to determine whether the IGFs interact with the placental RAS in early to mid gestation to modulate placental development and increase fetal growth and survival, and if IGF2 binding the IGF2R is implicated in the sustained effects of IGF2 treatment.


METHODS
At day 20 of pregnancy, guinea pigs were infused with 1m g/kg/day of IGF1, IGF2, (Leu27)IGF2 or vehicle for 18days and sacrificed on either day 62 (late pregnancy) or during the infusion period on day 35 (early-mid pregnancy). Placental structure at day 35 was analyzed using morphometric technique and expression of RAS genes in the placenta and placental and plasma renin activity were measured at both time points.


RESULTS
Compared with vehicle at day 35 of gestation, IGF1 infusion reduced the total midsagittal cross-sectional area of the placenta (-17%, p = 0.02) and the labyrinth area (-22%, p = 0.014) but did not alter the labyrinth volume nor labyrinth:interlobium ratios. IGF2 treatment did not affect placental structure. IGF1 did not alter placental mRNA for any of the RAS genes quantified at day 35 (AGTR1, ACE, AGT, TGFB1) but increased TGFB1 expression by more than 16-fold (p = 0.005) at day 62. IGF2 increased placental expression of AGTR1 (+88%, p = 0.03) and decreased AGT (-73%, p = 0.01) compared with the vehicle-treated group at day 35, and both IGF2 and (Leu27)IGF2 increased expression of TGFB1 at day 62 by 9-fold (p = 0.016) and 6-fold (p = 0.019) respectively. Both IGFs increased the ratio of active:total placental renin protein (+22% p = 0.026 p = 0.038) compared to vehicle compared to vehicle at day 35 but not 62. At day 62, IGF2-treated mothers showed a marked increase in total plasma renin (+495%) and active renin (+359%) compared to vehicle but decreased the ratio of active to total renin by 41% (p = 0.042). (Leu27)IGF2-treated animals had higher levels of placental active renin (+73%, p = 0.001) and total renin (+71%, p = 0.001) compared with the vehicle control.


CONCLUSIONS
The data obtained in the current study suggest the potential for alternate roles for the induction of the RAS after IGF treatment. IGF1 and 2 treatments increase the activation of prorenin to renin in the placenta, possibly due to increased protease activity. In addition, IGF2 treatment in early pregnancy may enhance the maternal adaptation to pregnancy through stimulation of renin in the kidney. The sustained effects on placental differentiation and function after IGF2 treatment suggest therapeutic potential for exogenous administration of IGFs in improving pregnancy outcomes.
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Prue
P
Standen
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Amanda N
AN
Sferruzzi-Perri
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Robyn
R
Taylor
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Gary
G
Heinemann
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Jamie V
JV
Zhang
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Amanda R
AR
Highet
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia; School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute, University of Newcastle, New South Wales, Australia.
Kirsty G
KG
Pringle
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Julie A
JA
Owens
School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute, University of Newcastle, New South Wales, Australia.
Vasumathy
V
Kumarasamy
School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute, University of Newcastle, New South Wales, Australia; Department of Physiology and Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
Eugenie R
ER
Lumbers
School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia. Electronic address: claire.roberts@adelaide.edu.au.
Claire T
CT
Roberts
D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D005865:Gestational Age; D006168:Guinea Pigs; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D010920:Placenta / Q000187:drug effects*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012084:Renin-Angiotensin System / Q000187:drug effects* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II
Insulin-like growth factors; Placenta; Pregnancy; Renin–angiotensin system