Search

Objective: We tested the effects of selective reduction of placental blood flow by mesenteric uterine artery branch ligation (MUAL) resulting in fetal growth restriction (FGR)., Methods: Timed mated C57BL/6J Day(D) 18 dams were divided into two groups: MUAL (n = 18); and control-sham (n = 18). Pups were delivered on D20, cross-fostered to surrogate CD-1 mothers for 4 weeks, and followed for 8 weeks. Outcome data included birth and placental weight, postnatal growth, placental volume determined by stereology, quantification of placental insulin-like growth factors-1(IGF-1) and IGF-2 and IGF binding proteins(IGFBP 2 and 6) by ELISA and gene expression by qPCR and GeneChip microarray analysis., Results: Compared with control, MUAL had an 11% reduction in mean birth weight (1.06 ± 0.13 g vs. 0.94 ± 0.13 g, p < 0.001) but no difference in placental weight. At 4 weeks of age, mean body weights of MUAL pups were significantly lower than sham. By 8 weeks, males but not females MUAL mice achieved equivalent mean body weight to control. Placental labyrinth depth, volume, and placental gene expression of IGF-1 and 2 were significantly reduced by MUAL. In contrast, placental protein level of IGFBP-2 and 6 were significantly elevated in the MUAL. Genomic expression analysis demonstrated that MUAL pups significantly up-regulated genes that were associated with apoptosis and growth pathways., Conclusion: This novel mouse animal model of FGR using selective ligation recapitulates multiple characteristics of placental vascular insufficiency (PI) in humans. This is the first non-genetic mouse model of PI which offers its application in transgenic mice to better study the underlying mechanisms in PI., Condensation: A new mouse model of placental vascular insufficiency by selective ligation of mesenteric uterine artery branch recapitulates multiple findings observed in human placental vascular insufficiency., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Information on the influence of poor maternal nutrition on the regulation of responses to pregnancy, placental and fetal growth and development is critical to a better understanding of pregnancy physiology and pathophysiology. We determined normal changes and effects of controlled and monitored moderate nutrient restriction (NR) (global nutrient intake reduced to 70% of food consumed by mothers feeding ad libitum from 0.16 to 0.5 of gestation) in the baboon, on important hematological, biochemical, and hormonal indices of fetal growth and placental function. Serum IGF-I:IGFBP-3 ratio was lower in pregnant than control non-pregnant baboons feeding ad libitum. Serum concentrations of total and free IGF-I were decreased in NR mothers compared with controls (p<0.05). The decrease in fetal IGF-I did not reach significance (p=0.057). Serum IGF-I: IGFBP-3 ratio was decreased by NR in both mothers and fetuses. Maternal serum IGF-II was unchanged by NR. Placental IGF-I mRNA and protein abundance were similarly reduced whereas IGF-II mRNA increased in placental tissue of NR compared to control mothers. Systemic (maternal) and local (placental) IGFBP-1 and IGFBP-3 mRNA and protein abundance were unchanged by NR. Type 1 IGF receptor protein in the syncytiotrophoblast increased in NR. Type 2 IGF receptor protein was present in the stem villi core, and decreased after NR. We conclude that moderate NR in this important non-human primate model significantly disrupts the maternal and placental IGF-IGFBP axis and influences placental expression of this key system at the gene and protein level. Changes observed appear to be directed toward preserving placental growth.

Insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) are paracrine regulators of tissue growth and development, and are expressed at the sites of biological action. To study the role of the IGFs and IGFBPs in mouse placental development, we determined the temporal and spatial expression patterns of the mRNAs at embryonic days 10.5 to 18.5 by in situ hybridization. IGF-II mRNA was expressed strongly in mesoderm and fetal blood vessels of early placenta and in labyrinthine trophoblast of later placenta. In the junctional zone, IGF-II mRNA was expressed first in spongiotrophoblasts, later strongly in glycogen cells and variably in giant cells. IGFBP-2 mRNA was expressed weakly in spongiotrophoblasts and glycogen cells. IGFBP-2, -5 and -6 mRNAs were detected in the stroma of the metrial gland. Myometrium expressed IGFBP-2 mRNA strongly, IGFBP-6 mRNA moderately and IGFBP-5 mRNA weakly. The endothelium of maternal blood vessels in decidua expressed IGFBP-3 and -5 mRNAs, and some deeper vessels expressed IGFBP-4 mRNA. In the yolk sac, IGF-II mRNA was expressed in endoderm and mesoderm, whereas IGFBP-1, -2 and -4 mRNAs were expressed only in endoderm, and IGFBP-4 mRNA in mesoderm. Strong expression of IGF-II mRNA in glycogen cells suggests a role in the autocrine/paracrine regulation of invasion. Similar to rat and guinea pig, but in contrast to man and primates, IGFBP mRNAs, except IGFBP-4, were not expressed in mouse decidua. However, IGFBP-3, -4 and -5 mRNAs were expressed in endothelium of maternal blood vessels, and IGFBP-2 and -6 mRNAs in myometrium, where IGFBPs may play a critical role in regulating trophoblast invasion. These findings suggest possible biological roles of the peptides at the feto-maternal interface.

To date, the clinicopathological features of intrauterine growth restriction (IUGR) are not clearly understood, and no effective therapy has been established for IUGR. This is the first study that uses microarray analysis to identify differentially expressed genes in the IUGR placenta. The expression profiles of a total of 9121 genes were examined by cDNA microarray analysis, using mRNA from an appropriate gestational age (AGA) placenta and an IUGR placenta from discordant dichorionic twins. Up-regulation of the IGFBP1 and Follistatin-like 3 genes was detected in the IUGR placenta, with a balanced differential degree of 20.7+/-1.3 and 13.1+/-2.1, respectively, while the balanced differential degrees of other genes were 2.6 or less. The expressions of the IGFBP1 and Follistatin-like 3 genes in four single IUGR and four AGA placentas were also examined by RT-PCR. Consistent with our data in discordant chorionic twin placentas, three of four IUGR placentas showed up-regulation of the IGFBP1 and all four IUGR placentas showed upregulation of Follistatin-like 3 genes when compared to the AGA placentas. Our results suggest that IGFBP1 and Follistatin-like 3 are highly up-regulated in IUGR in the placenta. IGFBP1 and Follistatin-like 3 are known critical regulators of fetal growth and differentiation. Pathways associated with these genes might be important for the pathogenesis of IUGR.

This study investigated the effects of maternal body condition and nutrition on placental and foetal growth in mid-gestation. Welsh Mountain ewes (n=24) of body condition 3.5 (high, H) and 2.0 (low, L) at mating, were fed either 100 per cent or 70 per cent of their daily maintenance requirements from day 22 of gestation, yielding four groups: H100 (n=5), H70 (n=6), L100 (n=7) and L70 (n=6). On day 65, placental and foetal parameters were measured. Whilst the placentome number tended to be lower in L than H ewes, the mean placentome weight was significantly greater in L100 than H100 animals. Nutritionally related changes in IGFBP expression within the placentome and intercotyledonary endometrium may explain these findings, with IGFBP-3 expression in the luminal epithelium and caruncular stroma of the placentome villi being inversely correlated to placentome number and the total placentome weight respectively. The foetal CRL was shorter and the ponderal index greater in L than H ewes. The foetal CRL was positively correlated to maternal IGF-I concentrations and the placentome number, although the foetal weight remained unaltered by treatment. This study therefore demonstrates that body condition and ration can alter foetal and placental growth, perhaps by modifying systemic parameters and uterine IGF expression.

To better understand the role of the insulin-like growth factors (IGF-I and -II) and their binding proteins (IGFBPs 1-6) in placental development and function, it is important to review similarities and differences between species in expression of the respective mRNAs. In human placenta, IGF-II mRNA is expressed in chorionic mesoderm and first trimester villous cytotrophoblast, but not in syncytiotrophoblast. In contrast, in rhesus monkey placenta, IGF-II mRNA is expressed in syncytiotrophoblast but not in chorionic mesoderm. IGFBP-3 mRNA is present in the chorionic mesoderm of placental villi from both these species and may modulate IGF-II action through a paracrine mechanism. In rodent placentae, IGF-II mRNA is expressed both in fetal mesoderm and in the trophoblast of the placental labyrinth. In guinea pig, where IGFBP-5 mRNA is expressed in the marginal and interlobular syncytium and IGF-II mRNA in the labyrinth, interaction between IGF-II and IGFBP-5 mRNA may be involved in vascularization of the placenta by fetal vessels. In sheep placenta, IGF-II mRNA is expressed, not in the trophoblast layer, but in the fetal mesoderm immediately adjacent to it. In the basal plate of human, rhesus monkey and baboon placentae, extravillous trophoblasts express IGF-II mRNA and uterine decidual cells IGFBP 1-6 mRNAs. The inference is that there is interaction between IGF-II and IGFBPs at the maternal-fetal interface of the primate placenta during trophoblast invasion and decidualization. IGFBP-1 expressed by the decidua may also interact with alpha(5)beta(1)integrin expressed by the extravillous trophoblast. The placentae of rodents are also of the invasive type. Glycogen cells of the mouse placenta are analogous with human extravillous trophoblast and express IGF-II mRNA. However, expression of IGFBP mRNAs in the mouse, as in the guinea pig, is confined to non-decidualized endometrium and myometrium. IGF-II mRNA is strongly expressed by trophoblasts invading uterine vessels in human and guinea pig placentae. Interactions probably occur between IGF-II expressed by these trophoblasts and IGFBPs expressed in the vessel walls. However, it is possible that IGFBPs expressed by maternal vessels are associated with processes that are independent of trophoblast invasion. Thus, IGFBP-3 mRNA is highly expressed in the maternal blood vessels of the non-deciduate sheep placenta. Findings to date highlight the diversity in the expression of the IGF system among placentae of man and different laboratory animals, and even between closely related species. Comparative studies will continue to be required to understand the functional role of IGFs and IGFBPs in each species.

To determine the temporal and spatial distribution of insulin-like growth factor (IGF) and its family of binding proteins (IGFBPs), guinea-pig yolk sac and chorioallantoic placentae were collected at 15, 20, 25, 29, 44-45, 55 and 65-66 days of gestation. Messenger RNAs for IGF I, IGF II and IGFBP 1-6 were identified in tissue sections by in situ hybridization, using 35S-cRNA probes. Epithelial and mesenchymal cell types were identified by immunohistochemistry for cytokeratin and vimentin, respectively. At 15 days of gestation, IGF-II mRNA was expressed in ectoplacental mesoderm, cytotrophoblasts and syncytiotrophoblast, and IGFBP-5 mRNA was detected in the syncytiotrophoblast. In the mid-gestation placenta, IGFBP-5 mRNA was expressed in the marginal and interlobular syncytium and IGF-II mRNA in the labyrinth. Near term, when expansion of the labyrinth was complete, IGFBP-5 mRNA was coexpressed with IGF-II mRNA in the marginal and interlobular syncytium. These observations suggest that interaction between IGF-II and IGFBP-5 plays a role in the vascularization of the placenta by fetal vessels. IGF-II mRNA was not expressed in the maternal tissues at any gestational age. IGFBP-2, -3 and -5 mRNAs were expressed in the endometrial stroma at 7-12 days of gestation but, following establishment of the placenta, IGFBP mRNAs were more abundant in the myometrium than in the decidua. IGF-II mRNA was detected in trophoblasts invading the walls of maternal vessels, and the endothelium of the preplacental vessels expressed IGFBP-4 mRNA, while IGFBP-2 and IGFBP-5 mRNAs were present in the tunica media of mesometrial arteries that had not been invaded by trophoblast. These findings suggest that IGF-II produced by the trophoblast acts in an autocrine and/or paracrine fashion to promote trophoblast invasion and that this process is modulated by interaction with IGFBPs present in maternal tissues.

Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) act as paracrine factors at or close to the sites of biosynthesis, i.e. cellular sites of expression of specific nRNAs. To determine the developmental pattern of expression of IGF-I, IGF-II, IGF-I R and IGFBP 1-6 mRNAs in the rhesus monkey placenta, in situ hybridization histochemistry was performed in placentae and fetal membranes from 65 days until term (165 +/- 5 days). IGF-I mRNA was not detectable in any of the specimens examined. IGF-II mRNA was localized abundantly in the placenta (syncytiotrophoblasts of the chorionic villi and the anchoring villi, and the extravillous cytotrophoblasts), and in the fetal membranes (chorion and amnion). IGF-I R mRNA was expressed predominantly in the decidua. All IGFBP mRNAs (IGFBP-1 to -6) were expressed in the maternal decidua in variable abundance. Only some IGFBP mRNAs, notably IGFBP-3 mRNA, was expressed in the fetal tissues, such as the chorionic mesoderm, some extravillous cytotrophoblasts and in the amnion and chorion. Gestational age did not alter the localization or relative abundance of all of the mRNAs studied. These findings suggest a role for IGF-II in the regulation of nutrient transport or placental hormone synthesis and/or secretion in the syncytiotrophoblasts, and a role for IGF-II and IGFBPs in the cell to cell communication and interaction at the feto-maternal interface.