Developmental Regulation of Placental Insulin-Like Growth Factor (IGF)-II and IGF-Binding Protein-1 and -2 Messenger RNA Expression During Primate Pregnancy1

Abstract

The present study was conducted to determine the developmental expression of placental insulin-like growth factor (IGF)-II, IGF-binding protein (IGFBP)-1 and -2, and IGF-II receptor mRNA expression during baboon pregnancy and whether estrogen, the levels of which increase with advancing pregnancy, regulates placental trophoblast IGF-II mRNA expression. Levels of the IGF-II 6.1-kilobase (kb) and 4.9-kb mRNA transcripts determined by Northern blot analysis progressively increased three- to fourfold in placental syncytiotrophoblast and whole-villous tissue between early (Day 60), mid (Day 100), and late (Day 170) baboon gestation (term = 184 days). In contrast, syncytiotrophoblast IGFBP-1 and -2 mRNA levels decreased, and IGF-II receptor mRNA expression remained relatively constant, with advancing baboon pregnancy. Placental cytotrophoblast IGF-II mRNA levels determined by competitive reverse transcription-polymerase chain reaction on Day 54 of gestation were increased (P < 0.05) almost twofold at 18 h after acute administration of estradiol to baboons, whereas long-term estrogen treatment had no effect. We propose that these changes in trophoblast IGF expression would provide a mechanism for enhancing net bioavailability and bioreactivity of IGF-II locally to promote the growth and development of the placenta and, consequently, of the fetus during primate pregnancy.

The IGF Axis in Baboon Pregnancy: Placental and Systemic Responses to Feeding 70% Global Ad Libitum Diet

“…In our study, both IGF-II mRNA and protein expression were detected in syncytiotrophoblast and cytotrophoblast with increased expression in placentae of the NR group. Our data are in agreement with observation of Zollers et al, who found IGF-II mRNA expression in baboon syncytiotrophoblast [6]. Increased placental expression of IGF-II has been detected with IUGR [43].…”

“…[4]). The placental IGF axis has been extensively studied in rats, sheep, horses, guinea pigs and nonhuman primates [5,6]. However, the placenta differs across species in its structure, conductive and exchange capacities, the mechanisms employed in nutrient exchange (reviewed in ref.…”

Hypoxia Regulates the Expression of PHLDA2 in Primary Term Human Trophoblasts

“…Interestingly, our findings regarding the expression of IGF-II in third trimester human trophoblasts are similar to those of Zollers et al [54] in primates and Hill et al [55] in humans, but not with those of Han et al [48], possibly reflecting differences in IGF-II assay sensitivity.…”

Interleukin-6 and insulin-like growth factor system relationships and differences in the human placenta and fetus from the 35th week of gestation

“…It is well known that IGF-I and IGF-II are both synthesized in the placenta [2,[10][11][12][13][14][15]. As in this tissue the localization of IGFs and IGFBPs was similar, it was suggested that the IGFBPs regulated IGFs within the placenta [16].…”