Expression of insulin-like growth factor in the placenta of intrauterine growth-retarded human fetuses

Modulation of fetoplacental growth, development and reproductive function by endocrine disrupters

Maternal endocrine homeostasis is vital to a successful pregnancy, regulated by several hormones such as human chorionic gonadotropin, estrogen, leptin, glucocorticoid, insulin, prostaglandin, and others. Endocrine stress during pregnancy can modulate nutrient availability from mother to fetus, alter fetoplacental growth and reproductive functions. Endocrine disrupters such as bisphenols (BPs) and phthalates are exposed in our daily life's highest volume. Therefore, they are extensively scrutinized for their effects on metabolism, steroidogenesis, insulin signaling, and inflammation involving obesity, diabetes, and the reproductive system. BPs have their structural similarity to 17-β estradiol and their ability to bind as an agonist or antagonist to estrogen receptors to elicit an adverse response to the function of the endocrine and reproductive system. While adults can negate the adverse effects of these endocrine-disrupting chemicals (EDCs), fetuses do not equip themselves with enzymatic machinery to catabolize their conjugates. Therefore, EDC exposure makes the fetoplacental developmental window vulnerable to programming in utero. On the one hand prenatal BPs and phthalates exposure can impair the structure and function of the ovary and uterus, resulting in placental vascular defects, inappropriate placental expression of angiogenic growth factors due to altered hypothalamic response, expression of nutrient transporters, and epigenetic changes associated with maternal endocrine stress. On the other, their exposure during pregnancy can affect the offspring's metabolic, endocrine and reproductive functions by altering fetoplacental programming. This review highlights the latest development in maternal metabolic and endocrine modulations from exposure to estrogenic mimic chemicals on subcellular and transgenerational changes in placental development and its effects on fetal growth, size, and metabolic & reproductive functions.

Expression and functional role of IGFs during early pregnancy in placenta of water buffalo

Adequate vascularisation is a key factor for successful fetal development. We hypothesized that Insulin-Like Growth Factor (IGF) family members regulate angiogenesis along with promoting fetal development and growth. In this experiment, we determined the expression and functional role of IGF family in placental compartments (caruncle; CAR, cotyledon; COT) during different stages of early pregnancy in the water buffalo (Bubalus bubalis). Samples were collected from early pregnancy 1 (EP1, 28-45 days), early pregnancy 2 (EP2, 45-90 days), and third stage of estrous cycle (11-16 days), which was taken as control. In addition, the role of IGF1 on mRNA expression of vWF, StAR, CYP11A1, 3βHSD, PCNA, and BAX were elucidated in cultured trophoblast cells (TCC) obtained from EP2. Quantitative real-time PCR (q-PCR), westernblot, and immunohistochemistry were done to investigate the gene expression, protein expression, and localization of examined factors, and RIA was also done to assess progesterone (P₄) concentration. Expression of IGFs, its receptors and binding proteins were found to be significantly higher (p < 0.05) in both CAR and COT as compared to control during early pregnancy, except binding proteins IGFBP1, 3 and 4 which were significantly (p < 0.05) downregulated in COT with advancement of pregnancy. mRNA expression was consistent with the findings of immunoblotting and immunolocalization experiments. Trophoblasts cell culture (TCC) study showed a significant time and dose-dependent effect of IGF1 onsteroidogenic transcript, which was found to be maximum at 100 ng/ml that paralleled with P₄ accretion in the media (p < 0.05). Further, IGF1 upregulated the transcripts of vWF, PCNA, and downregulated BAX at the same concentration (p < 0.05). Overall, our results demonstrated that the expression of IGFs is a site-specific phenomenon in placentome, which indicates autocrine/paracrine and endocrine function. Our in-vitro finding support that IGF1 plays a critical role in placental development by promoting angiogenesis, steroid synthesis, and cell proliferation during early pregnancy.

Differential expression of leukemia inhibitory factor and insulin like growth factor-1 between normal pregnancies, partial hydatidiform moles and complete hydatidiform moles

INTRODUCTION

Leukemia inhibitory factor (LIF) and insulin like growth factor-1 (IGF-1) are two of the most important growth factors mediating trophoblast actions. We hypothesized that the localization and expression patterns of LIF and IGF-1 in partial and complete hydatidiform moles (HM) compared with normal first trimester placentas may provide an understanding of the proliferative processes in HMs.

METHODS

The study population included curettage material of women diagnosed as complete or partial HM as a result of histopathological and immunohistochemical examination (complete HM group, n = 8; partial HM group, n = 8) and women undergoing dilatation&curettage for unwanted pregnancies (control group, n = 8). Expression of LIF and IGF-1 among placental cell groups was evaluated immunohistochemically and given a score depending on immunostaining intensity.

RESULTS

In normal chorionic villi strong expression of LIF and IGF-1 was present. Both LIF and IGF-1 expressions were weaker in the chorionic villi of complete HMs. In complete mole decidua there was a significant decrease in glandular and endothelial IGF-1 expression along with a decrease in decidual cell LIF expression compared to normal first trimester decidua. LIF expression in extravillous trophoblasts was stronger in complete molar placentas compared to normal placentas.

DISCUSSION

LIF and IGF-1 are important regulators of trophoblast proliferation and invasion. Differential expression of LIF and IGF-1 in molar trophoblasts and chorionic villi might have a role in regulation of trophoblasts in complete moles. Decreased expression of glandular IGF-1 and decidual LIF might be related to the decidual changes during trophoblastic proliferation and invasion of decidua in complete HMs.

Integrative analysis of 111 reference human epigenomes

The reference human genome sequence set the stage for studies of genetic variation and its association with human disease, but epigenomic studies lack a similar reference. To address this need, the NIH Roadmap Epigenomics Consortium generated the largest collection so far of human epigenomes for primary cells and tissues. Here we describe the integrative analysis of 111 reference human epigenomes generated as part of the programme, profiled for histone modification patterns, DNA accessibility, DNA methylation and RNA expression. We establish global maps of regulatory elements, define regulatory modules of coordinated activity, and their likely activators and repressors. We show that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease. Our results demonstrate the central role of epigenomic information for understanding gene regulation, cellular differentiation and human disease.

Glucose, insulin, and oxygen interplay in placental hypervascularisation in diabetes mellitus

The placental vasculature rapidly expands during the course of pregnancy in order to sustain the growing needs of the fetus. Angiogenesis and vascular growth are stimulated and regulated by a variety of growth factors expressed in the placenta or present in the fetal circulation. Like in tumors, hypoxia is a major regulator of angiogenesis because of its ability to stimulate expression of various proangiogenic factors. Chronic fetal hypoxia is often found in pregnancies complicated by maternal diabetes as a result of fetal hyperglycaemia and hyperinsulinemia. Both are associated with altered levels of hormones, growth factors, and proinflammatory cytokines, which may act in a proangiogenic manner and, hence, affect placental angiogenesis and vascular development. Indeed, the placenta in diabetes is characterized by hypervascularisation, demonstrating high placental plasticity in response to diabetic metabolic derangements. This review describes the major regulators of placental angiogenesis and how the diabetic environment in utero alters their expression. In the light of hypervascularized diabetic placenta, the focus was placed on proangiogenic factors.

Decreased placental expression of hPGH, IGF-I and IGFBP-1 in pregnancies complicated by fetal growth restriction

OBJECTIVE

The human Placental Growth Hormone (hPGH) and the Insulin-like Growth Factor (IGF) system are implicated in fetal development. This study aimed to evaluate the expression of hPGH, IGF-I, IGFBP-1 and IGFBP-3 genes in placentas from pregnancies complicated by fetal growth restriction (FGR).

DESIGN

The study group was comprised of term placentas from 47 FGR-complicated pregnancies of no recognizable cause. Thirty-seven placentas from normal pregnancies with appropriate for gestational age birth weight were used as controls. The expression status of the genes was evaluated by quantitative real-time PCR.

RESULTS

hPGH, IGF-I and IGFBP-1 exhibited significantly lower expression compared to the controls (p=0.003, p=0.049 and p=0.001, respectively). Numerically, lower IGFBP-3 expression was also demonstrated in the FGR-affected group, without however reaching statistical significance (p=0.129). Significant co-expression patterns were detected among the study genes in both the FGR and normal pregnancies.

CONCLUSION

Decreased placental expression levels of hPGH, IGF-I and IGFBP-1 were demonstrated in pregnancies with FGR. Whether these alterations are a causative factor of FGR or accompany other pathogenetic mechanisms requires further investigation.

The severe short stature in two siblings with a heterozygous IGF1 mutation is not caused by a dominant negative effect of the putative truncated protein

OBJECTIVE

While in previous studies heterozygosity for an Insulin-Like Growth Factor 1 (IGF1) defect only modestly decreased height and head circumference, we recently reported on two siblings with severe short stature with a maternally transmitted heterozygous duplication of 4 nucleotides, resulting in a frame shift and a premature termination codon in the IGF1 gene. In this paper we describe the structural and functional characteristics of the putative truncated IGF-I protein.

DESIGN

Two children, their mother and maternal grandfather carried the mutation. In addition, two family members who were not affected were included in the study. Mutant (MT) IGF-I was synthesized in oxidized and reduced form using two methods. Neutral gel filtration studies were carried out with wild-type (WT) and synthetic MT IGF-I. Binding analysis of synthetic MT IGF-I to the IGF1R and insulin receptors were performed with EBNA-293 cells, stably transfected with the IGF-I receptor, and IM9 cells. L6 cells were used to examine the mitogenic potency and the potential antagonizing effect of synthetic MT IGF-I by [(3)H]-thymidine incorporation assays.

RESULTS

In the sera of both the carriers and non-carriers the proportion of (125)I-IGF-I that was associated with the 150 kDa complex was somewhat less (varying between ~37 and ~52%) than in normal pooled serum (~53-~63%) and, instead, slightly increased amounts of radioactivity were eluted in the 40-50 kDa fraction (consisting of binary IGF-IGFBP complexes) or remained unbound. Synthetic MT IGF-I did not bind to the IGF-I receptor, nor antagonize the growth-promoting effect of IGF-I. It did bind to IGFBPs, but was barely incorporated into 150 kDa complexes. Because in all cases WT IGF-I immunoreactivity was recovered in one peak, corresponding to the MW of WT IGF-I, i.e. ~7.6 kDa, an interaction of circulating truncated mutant peptide with WT IGF-I is very unlikely.

CONCLUSIONS

There is no evidence that the severe short stature associated with heterozygosity for this novel IGF1 mutation in children born from a mother with the same mutation is caused by a dominant negative effect of the truncated protein. We speculate that the growth failure is caused by a combination of partial IGF-I deficiency, placental IGF-I insufficiency, and other genetic factors.

Insulin and the IGF system in the human placenta of normal and diabetic pregnancies

The insulin/insulin-like growth factor (IGF) system regulates fetal and placental growth and development. In maternal diabetes, components of this system including insulin, IGF1, IGF2 and various IGF-binding proteins are deregulated in the maternal or fetal circulation, or in the placenta. The placenta expresses considerable amounts of insulin and IGF1 receptors at distinct locations on both placental surfaces. This makes the insulin and the IGF1 receptor accessible to fetal and/or maternal insulin, IGF1 and IGF2. Unlike the receptor for IGF1, the insulin receptor undergoes a gestational change in expression site from the trophoblast at the beginning of pregnancy to the endothelium at term. Insulin and IGFs are implicated in the receptor-mediated regulation of placental growth and transport, trophoblast invasion and placental angiogenesis. The dysregulation of the growth factors and their receptors may be involved in placental and fetal changes observed in diabetes, i.e. enhanced placental and fetal growth, placental hypervascularization and higher levels of fetal plasma amino acids.

Placental expression of insulin-like growth factor-I, fibroblast growth factor-basic and neural cell adhesion molecule in pregnancies with small for gestational age fetuses

OBJECTIVE

To investigate placental expression of insulin-like growth factor-I (IGF-I), fibroblast growth factor-basic (FGF-b) and neural cell adhesion molecule (N-CAM) regarding the pathogenesis of pregnancies with small for gestational age (SGA) fetuses.

STUDY DESIGN

An immunohistochemical analysis using anti-IGF-I, anti-FGF-b and anti-N-CAM antibodies was carried out on 4% paraformaldehyde-fixed placental tissues of third trimester pregnancies complicated with SGA fetuses (n=12) and subjects exhibiting appropriately grown fetuses (n=10). Immunostaining patterns of chorionic villi and amniochorionic membranes were assessed.

RESULT

IGF-I, FGF-b and N-CAM immunostainings in chorionic villi demonstrated significantly increased immunoreactivities in cytotrophoblasts of SGA cases, whereas increased IGF-I immunostaining in syncitiotrophoblasts and increased N-CAM immunostaining in capillary endothelium were noted in the same group. IGF-I, FGF-b and N-CAM immunostainings in amniochorionic membranes revealed significantly decreased IGF-I immunoreactivities in extravillous trophoblasts and increased IGF-I immunoreactivities in decidual cells of SGA cases, while significantly decreased N-CAM immunoreactivities in both decidual cells and extravillous trophoblasts were noted. FGF-b immunostaining revealed no significant differences in both extravillous trophoblasts and decidual cells of SGA cases.

CONCLUSION

Increased placental expression of IGF-I, FGF-b and N-CAM may act in an autocrine and/or paracrine manner to restore the impaired trophoblastic proliferation, migration and metabolism at all gestational stages by means of a positive feedback mechanism.

The IGF axis and placental function. a mini review

It is well known that the insulin-like growth factor (IGF) axis is an important regulator of foetal growth and in recent years, it has been suggested that the ligands IGF-I and IGF-II may, in part, mediate this effect by promoting proper placental development and function. In other tissues, IGF effects on metabolism, proliferation and differentiation are primarily mediated via IGF binding protein-regulated interaction of IGFs with the type 1 IGF receptor and therefore here, we review the placental expression and postulated role, of each of the IGF axis components and discuss the cellular mechanisms through which these effects are exerted.

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

The integrity of the insulin-like growth factor (IGF) system is essential for normal fetal growth. Cytokine and IGF-IGFBP relationships have been shown in specific tissues, but it is unknown whether these occur in the placenta. We aimed to assess possible differences in the IGF system depending on gestational age (GA) from week 35 to 40, and to study relationships of IL-6 with components of the IGF system in the placenta and newborn infant. We followed 32 normal births and collected whole villous tissue and cord serum. Total RNA was extracted from the placenta samples, reverse transcribed and then real-time quantitative (TaqMan) RT-PCR was performed to quantify cDNA for IGF-I, IGF-II, IGFBP-1, IGFBP-2 and IL-6. The corresponding proteins were assayed in placenta lysates and cord serum using specific commercial kits. Two groups of subjects (Group 1, 35-37 weeks GA, N=12 and Group 2, 38-40 weeks GA, N=20) were studied. In placenta, IGF-I mRNA was more abundant than IGF-II mRNA at all times and together with IGFBP-1mRNA were less expressed at term. IGFBP-2 and IL-6 mRNAs were higher after week 37 GA. IL-6 and IGFBP-2 gene expression were closely related. The corresponding proteins showed similar differences to the genes but IGF-I was undetectable in the lysates, whereas IGF-II was abundant. IGFBP-2 concentrations were very high and greater than those of IGFBP-1. In the newborn, no difference was seen in any cord serum protein after week 35 GA. IGFBP-1 was negatively correlated with parameters of neonatal size. In conclusion, this study reports new insights into IL-6, IGF-IGFBP relationships within the human placenta and shows the importance of comparing subjects with the same GA.

Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus

The environment in which the fetus develops is critical for its survival and long-term health. The regulation of normal human fetal growth involves many multidirectional interactions between the mother, placenta, and fetus. The mother supplies nutrients and oxygen to the fetus via the placenta. The fetus influences the provision of maternal nutrients via the placental production of hormones that regulate maternal metabolism. The placenta is the site of exchange between mother and fetus and regulates fetal growth via the production and metabolism of growth-regulating hormones such as IGFs and glucocorticoids. Adequate trophoblast invasion in early pregnancy and increased uteroplacental blood flow ensure sufficient growth of the uterus, placenta, and fetus. The placenta may respond to fetal endocrine signals to increase transport of maternal nutrients by growth of the placenta, by activation of transport systems, and by production of placental hormones to influence maternal physiology and even behavior. There are consequences of poor fetal growth both in the short term and long term, in the form of increased mortality and morbidity. Endocrine regulation of fetal growth involves interactions between the mother, placenta, and fetus, and these effects may program long-term physiology.

Following the fate of murine epidermal stem cells in a syngeneic dermal equivalent in vivo

BACKGROUND

Stem cells in healthy epidermis have the capacity to produce structures, such as interfollicular epidermis, hair follicle, and sebaceous glands. Embryonic stem (ES) cells can be induced to differentiate into epidermal stem cells in vitro. These ESCs (epidermal or epidermoid stem cells derived from ES cells) have the potential to be an ideal replacement of those stem cells destroyed in severe injury, such as in deep and extensive burn. The aim of this study was to follow the fate of murine ESCs which were seeded in a syngeneic dermal equivalent and implanted into syngeneic recipient mice subcutaneously.

METHODS

ES cells were induced in vitro to differentiate into ESCs. Stained with a fluorescent dye Hoechst 33342, these ESCs were seeded into a fibroblast-collagen-gelatin sponge complex, functioning as a dermal equivalent model, and then implanted subcutaneously into 129/J mice, which were syngeneic to these stem cells.

RESULTS

These ESCs were clearly visible in the implant by fluorescent microscopy 3 weeks or longer after implantation. These cells remained viable, differentiating into hair follicle-like structures, glandular structures, and gave rise to additional structures resembling native dermis. A number of markers were expressed in the differentiated structures, including CD29 (integrin beta1 subunit) and cytokeratin 18 (CK18). No apparent rejection or severe side effects were observed at least during the 10 weeks following implantation.

CONCLUSIONS

Now that ESCs can survive in vivo in this dermal equivalent model and differentiate into hair follicle-like structures as well as glandular structures, it is feasible to use these cells as seed cells in studies to fabricate dermal equivalents that have the potential to develop dermal appendages.

Immunohistochemical analysis of neural cell adhesion molecule (N-CAM) and pan-cadherin in the small intestine of intrauterine growth-retarded newborn rats caused by maternal protein malnutrition

Cell-cell and cell-matrix adhesion molecules play an important role in morphogenesis, cell signaling and are involved in cell proliferation, cell death, cell polarization and differentiation. In the present study, we investigated N-CAM and pan-cadherin expression in small intestine of intrauterine growth-retarded (IUGR) newborn rats after maternal protein malnutrition during pregnancy. N-CAM and pan-cadherin immunostaining was increased in small intestine of IUGR newborn rats. This increase was evident in epithelial cells on villi, lamina propria, submucosa, muscularis mucosa and muscularis externa. The increase in numbers of villous N-CAM-positive and pan-cadherin-positive epithelial cells was statistically significant (p < 0.001). In most areas, crypts did not show any immunopositive epithelial cells or showed decreased expression of the adhesion molecules. Although the villous height was decreased in IUGR rats, the decrease was statistically not significant. Expression and recruitment of N-CAM and pan-cadherin in small intestine of newborn IUGR rats may indicate a direct or indirect involvement of adhesion mechanisms or signaling in the growth retardation process.

Over-expression and secretion of angiogenin in intrauterine growth retardation placenta

Human angiogenin is a potent inducer of neovascularization. There is a strong evidence to suggest that it might be involved in morphological and angiogenic changes in the placenta, that are necessary for a successful fetal outcome during pregnancy. However, its precise role in the pathogenesis of abnormal pregnancies is yet unknown. Intrauterine growth retardation (IUGR), an abnormal pregnancy is not a specific disease entity per se, but rather a manifestation of many possible fetal and maternal disorders. In this study, we demonstrated, for the first time, that placental explants in vitro secrete significantly elevated levels of angiogenin in placental tissues from patients with IUGR. We also observed enhanced mRNA expression in placenta from these patients. In addition, using the immunohistochemical methods, we observed identical staining of angiogenin to villous syncytiotrophobalst and fetal endothelial cells in both IUGR and normal placenta. Functionally active placental explants were used to detect immunoreactive angiogenin in conditioned media of all the samples from IUGR placenta and normal term group. The mean levels of angiogenin secreted by IUGR placenta were 1.4-, 1.6-, and 1.3-fold higher (P < 0.01) than normal term samples at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and IUGR cases are in agreement with its mRNA levels and immunoblot analysis. In conclusion, the significant elevated levels of angiogenin in IUGR placenta may provide a molecular mechanism for the abnormal placental development.