Immunolocalization of PCNA, Ki67, p27 and p57 in normal and dexamethasone-induced intrauterine growth restriction placental development in rat

Intrauterine growth restriction (IUGR) is a major clinical problem which causes perinatal morbidity and mortality. Although fetuses with IUGR form a heterogeneous group, a major etiological factor is abnormal placentation. Despite the fact that placental development requires the coordinated action of trophoblast proliferation and differentiation, there are few studies on cell cycle regulators, which play the main roles in the coordination of these events. Moreover it is still not determined how mechanisms of coordination of proliferation and differentiation are influenced by dexamethasone-induced IUGR in the placenta. The aim of the study was to investigate the spatial and temporal immunolocalization of proliferating cell nuclear antigen (PCNA), Ki67, p27 and p57 in normal and IUGR placental development in pregnant Wistar rats. The study demonstrated altered expressions of distinct cell cycle proteins and cyclin dependent kinase inhibitors (CKIs) in IUGR placental development compared to control placental development. We found reduced immunostaining of PCNA and Ki67 and increased immunostaining of p27 and p57 in the dexamethasone-induced IUGR placental development compared to control placental development. In conclusion, our data show that the cell populations in the placenta stain for a number of cell cycle related proteins and that these staining patterns change as a function of both gestational age and abnormal placentation.     

Endothelial nitric oxide synthase in placental villous tissue from normal, pre-eclamptic and intrauterine growth restricted pregnancies

Nitric oxide (NO) regulates blood flow in the human placenta. As increased resistance to blood flow is seen in the fetal-placental vasculature in pregnancies complicated by pre-eclampsia and/or intrauterine growth restriction (IUGR), we examined expression of endothelial nitric oxide synthase (eNOS) in these placentas. Placental villous tissue sections were obtained from normotensive control (n = 5), IUGR alone (n = 5) or pre-eclamptic (with or without IUGR (n = 9) patients, immunostained for eNOS and scored for localization, type (punctate or diffuse) and intensity of eNOS staining in syncytiotrophoblast and placental vessels. The significance of differences was calculated using the Mann-Whitney U-test. No differences in intensity or type of immunostaining in syncytiotrophoblast were seen. Placentas from patients with pre- eclampsia with or without IUGR had a significantly more basal distribution of eNOS in syncytiotrophoblast. eNOS immunostaining was absent in terminal villous capillary and faint in stem villous vessel endothelium of normal placentas, but was intense in the endothelium of both of these types of vessels in the IUGR and pre-eclampsia groups, with significantly greater staining seen in stem vessels of patients with IUGR alone. This increased eNOS expression and hence increased NO production in the fetal-placental vasculature may be an adaptive response to the increased resistance and poor perfusion in these pathological pregnancies.      

Trisomy 9 confined to the placenta: Prenatal diagnosis and neonatal follow-up

Chorionic villus sampling (CVS), performed on a woman in the 23rd menstrual week because of bilateral fetal hydronephrosis and suspected intrauterine growth retardation (IUGR), documented trisomy 9 in all cells examined. Chromosomes of amniocytes and fetal blood lymphocytes were normal. The ongoing pregnancy was monitored closely, and at 37 weeks, a phenotypic normal male infant was delivered. Multiple placental biopsies showed 47,XY,+9, while a repeat chromosome analysis of the infant and biopsies from the amniotic membrane were normal (46,XY). This case further emphasizes the association between placental aneuploidy and IUGR. To our knowledge, nonmosaic trisomy 9 in CVS confined to the chorionic villi and later confirmed in the placenta has not been reported previously.     

正常足月胎盘和胎儿宫内生长迟缓胎盘中滋养细胞的凋亡及相关基因表达

目的 比较正常足月胎盘与胎儿宫内生长迟缓胎盘（IUGR）中的滋养细胞凋亡指数,以及bcl-2和fas的表达,以探讨滋养细胞的凋亡与bcl-2和fas表达的关系。方法 取正常足月胎盘组织和I－UGR胎盘组织各5例,固定、石蜡包埋、切片,每组分别TUNEL法以及ABC法抗bcl－2和抗fas免疫组织化学染色。镜下计数滋养细胞的凋亡指数,并对bcl-2和fas的表达量进行显微图像分析。结果 与正常足月胎盘相比,IUGR胎盘的凋亡指数显著增多（P＜0．01）,bcl－2表达量显著减低（P＜0．01）,而fas表达量无显著差异（P＞0．05）。结论 IUGR胎盘滋养细胞的凋亡指数明显增多可能与细胞bcl-2表达量减少有关,而不受fas表达量的影响。     

Hypoxia down-regulates placenta growth factor, whereas fetal growth restriction up-regulates placenta growth factor expression: molecular evidence for "placental hyperoxia" in intrauterine growth restriction

Early placental development occurs in an environment of relative hypoxia. Hypoxia promotes angiogenesis and up-regulates vascular endothelial growth factor (VEGF) expression while it down-regulates placenta growth factor (PIGF) that possess 53% homology with VEGF. Morphological studies show poor placental vascular development and an increase in the mitotic index of cytotrophoblasts in intrauterine growth restriction (IUGR). We hypothesized that the reported relatively high oxygen level in the intervillous space in contact with IUGR placental villi will limit angiogenesis by changes in VEGF and PIGF expression and function. Western immunoblot analysis demonstrates a diametric expression of PIGF and VEGF proteins throughout pregnancy with PIGF levels increasing and VEGF levels decreasing, consistent with placental oxygenation. In IUGR placentae, the ratio of PIGF/GAPDH mRNA was increased by 2.3-fold (p < 0.03) and PIGF protein levels were also increased, (p < 0.05) as compared with gestationally-matched normal placentae. PIGF mRNA and protein were localized to the trophoblast bilayer and villous mesenchyme of the human placenta throughout gestation. In vitro studies demonstrated that increasing oxygen tension (hyperoxia) up-regulated PIGF protein in term placental villous explants, whereas hypoxic culture of a term trophoblast choriocarcinoma cell line (BeWo) down-regulated PIGF mRNA and protein and VEGFR-1 (Flt-1) autophosphorylation. The addition of PIGF-1 to a spontaneously transformed first trimester cytotrophoblast cell line stimulated DNA synthesis while PIGF-2 had little effect. VEGF and PIGF exert their biological actions by means of a common receptor VEGFR-1. In the first trimester trophoblast cells, PIGF-1 increased the association of phosphorylated extracellular signal-related kinase (ERK) with VEGFR-1 immunoprecipitates while both PIGF-1 and PIGF-2 also potentiated endogenous VEGF mediated association of phosphorylated extracellular related kinase (ERK) with VEGFR-2 (KDR). More importantly, the addition of PIGF-1 had little effect while PIGF-2 inhibited cell growth in cultured endothelial cells derived from human umbilical vein. Nitric oxide (NO) is reported to promote angiogenesis and PIGF-2 inhibited the basal release of NO from the first trimester trophoblast. The tissue expression and functional studies support the hypothesis of "placental hyperoxia" in early-onset IUGR because hypoxia down-regulates trophoblast PIGF levels, PIGF expression is increased in IUGR, and PIGF-2 inhibits endothelial cell growth. Taken together, these changes provide a cellular explanation for the observed poor angiogenesis in the pathogenesis of IUGR and show that the two PIGF isoforms may modulate trophoblast and endothelial cell function differently, possibly through potentiation of VEGF mediated activation of VEGF-2.     

Insulin-like growth factor I in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation

We examined whether insulin-like growth factor-I (IGF-I) and one of its binding proteins (IGFBP-1) in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation (IUGR) and weight estimation by ultrasound. Cordocentesis sera from 27 fetuses suspected of having IUGR were analysed for IGF-I and IGFBP-1 by radioimmunoassay. The results showed that IGF-I concentrations were correlated significantly with birth weight (P < 0.001) and placenta weight (P < 0.05). Mean fetal concentrations of IGF-I were 38 +/- 18 microg/l. In patients (n = 11) with a weight deviation at delivery <-33%, IGF-I concentrations were 24.1 +/- 13.2 microg/l. IGFBP-1 was inversely correlated with birth weight (P < 0.006) and concentrations of IGF-I. Mean plasma concentrations of IGFBP-1 were 234.2 +/- 161.4 microg/l. Furthermore, IGF-I concentrations were correlated with the weight deviation estimated by ultrasonography at the time of cordocentesis (P < 0.007), as well as with the weight deviation at delivery (P < 0.0001). The actual weight deviation at delivery was correlated more strongly with fetal IGF-I concentrations than with the estimated weight deviation at cordocentesis. The lowest concentrations of IGF-I were found in patients with a weight deviation <-33%. Very low concentrations of IGF-I are thus associated with IUGR, indicating that IGF-I measured in fetal serum may increase the predictive value of ultrasonographic weight estimation.      

Genes or placenta as modulator of fetal growth: evidence from the insulin-like growth factor axis in twins with discordant growth

To determine whether fetal growth is regulated by placental and/or fetal factors, we measured maternal and fetal concentrations of insulin-like growth factor-I (IGF-I), IGF-II and insulin-like growth factor binding protein-1 (IGFBP-1) (total and non-phosphorylated) in dichorionic (DC) and monochorionic (MC) twins with (DC, n = 13; MC, n = 12) or without (DC, n = 13; MC, n = 12) discordant birth weight. In the discordant MC pregnancy, growth-restricted (IUGR) twins had lower IGF-II concentrations (P < 0.001) but similar IGF-I concentrations compared to the appropriate for gestational age(AGA) co-twin. The differences in IGF-II concentrations showed a positive association with percentage birth weight discordance (r = 0.60; P < 0.05) in MC twins. In contrast, IUGR DC twins had lower IGF-I concentrations (P < 0.05) but similar IGF-II concentrations compared to the AGA co-twins. There was a positive correlation between IGF-I concentrations and birth weight (r = 0.47; P < 0.05) in DC twins. Total IGFBP-1 concentrations were higher in both MC and DC IUGR twins (P < 0.05) compared to AGA twins. A negative association was found between total IGFBP-1 concentrations and birthweight of both MC (r = 0.47; P < 0.05) and DC (r = 0.58; P < 0.01) twins. No such differences in IGF concentrations were found between concordant MC and DC twin pairs. The maternal IGF concentrations were comparable between the MC and DC groups. These data suggest that growth discordances of twins exposed to the same maternal environment may be due to variations in either IGF-I or IGF-II/IGFBP-1, depending upon the functioning of the placenta.     

Placental leptin in normal, diabetic and fetal growth-retarded pregnancies

Leptin expression in third trimester placenta (p) and leptin concentrations in umbilical cord blood (cb) were investigated in normal pregnancies [n = 10 (p), 31 (cb)] and abnormal pregnancies complicated with (i) maternal insulin-dependent diabetes [IDDM: n = 3 (p), 13 (cb)], (ii) gestational diabetes [GD: n = 2 (p), 10 (cb)] and (iii) fetal growth retardation [FGR: n = 5 (p), 5 (cb)]. By in-situ hybridization and immunohistochemistry, placental leptin mRNA and protein were co-localized to the syncytiotrophoblast and villous vascular endothelial cells. Leptin receptor was immunolocalized to the syncytiotrophoblast. Relative to controls, the FGR group was characterized by low concentrations of placental and cord blood leptin. In a twin pregnancy, the normal-sized infant exhibited more placental and cord blood leptin than its growth-retarded twin. In contrast, both diabetic groups exhibited high concentrations of placental leptin mRNA and protein. The IDDM group exhibited the highest concentrations of leptin in cord blood. No change was observed in the expression of the leptin receptor in either the growth-retarded or diabetic pregnancies. In conclusion, the localization of placental leptin suggests that it may be released into both maternal and fetal blood. Furthermore, in fetal growth-retarded and diabetic pregnancies, the changes in leptin expression in the placenta and in leptin concentrations in umbilical cord blood appear to be related.     

Expression of IGR-IR and VEGF and trophoblastic proliferative activity in placentas from pregnancies complicated by IUGR

Intrauterine growth retardation (IUGR) is recognized as an important cause of low birth weight and elective preterm delivery. IUGR is associated with multiple causative factors, including placental dysfunction. The aim of this prospective study was to investigate the role of trophoblastic proliferative activity and type I insuline-like growth factor receptor (IGF-IR) and vascular endothelial growth factor (VEGF) expressions in the pathogenesis of IUGR. Immunohistochemistry using VEGF, IGF-IR, and Ki-67 antibodies was performed on formalin-fixed placental tissues of third-trimester pregnancies complicated by IUGR (n = 19) and pregnancies with appropriately grown fetuses (n = 27). In addition, histopathological examination of the placentas was performed, and histological findings were categorized into three groups: utero-placental vascular pathologies (UPVP), coagulation-related pathologies, and chronic inflammation. Statistical analysis revealed that villous trophoblastic IGF-IR immunostaining was significantly weaker in placentas with IUGR (p < 0.001), whereas trophoblastic Ki-67 proliferative index and VEGF immunoscoring did not show any significant difference. Histologically, UPVP and chronic inflammation were significant findings in placentas with IUGR (p = 0.04 and p = 0.04, respectively). In addition, placentas were significantly smaller in the IUGR group (p < 0.001). We conclude that villous trophoblastic IGF-IR expression may play a significant role in the pathogenesis of IUGR, and histopathological examination of placentas in pregnancies complicated by IUGR may yield significant findings. In contrast, based on our findings, trophoblastic proliferation and VEGF expression are unlikely to be significant parameters in the pathogenesis of IUGR.     

Distribution and maturity of dendritic cells in diseases of insufficient placentation

Problem The immunological equilibrium at the feto-maternal interphase contributes towards late gestational diseases like growth restriction (IUGR) pre-eclampsia (PE) and hemolysis, elevated liver enzymes, low platelets (HELLP)-syndrome. The state of activation of decidual dendritic cells (DC) has emerged as one of the central players influencing this immunological equilibrium. Method of study Paraffin-embedded tissue sections from 27 pregnancies were immunostained for DC markers DEC-205, DC-SIGN, DC-LAMP and costained for DC-SIGN/CD56 and DC-SIGN/ vascular endothelial growth factor receptor (VEGFR) -1 and -2. We investigated placental tissue of IUGR fetuses and of patients who developed PE or HELLP-syndrome as well as placental tissue derived from normal pregnancies. Results We found that expression of DEC-205 and DC-SIGN was significantly upregulated in HELLP placentas, whereas expression of DC-LAMP was abrogated almost entirely. Costaining showed an interaction between DC-SIGN(+) DC and natural killer cells as well as costaining of VEGFR-1 and -2 and DC-SIGN. Pre-eclamptic and IUGR placentas showed no significant change in any of the investigated markers compared to normal controls. Conclusion Our data suggest a participation of DC-mediated immunological mechanisms in HELLP syndrome.     

Heme oxygenases in pregnancy II: HO-2 is downregulated in human pathologic pregnancies

PROBLEM: We previously reported a diminished expression of the heme-degrading enzymes heme oxygenases (HO)-1 and HO-2 in decidua and placenta from mice undergoing Th1-mediated abortion, strongly indicating the protective effect of HO in murine pregnancy maintenance. Here we investigated whether the expression of HO-1 and HO-2 is also reduced at the feto-maternal interface of pathologic human pregnancies. METHOD OF STUDY: Immunohistochemistry was used to detect HOs expression in placental and decidual first-trimester tissue from patients with: spontaneous abortion (n = 14), choriocarcinoma (n = 14), hydatidiform mole (H-mole) (n = 12), compared with normally progressing pregnancies (n = 15). Further, we investigated early third-trimester decidual and placental tissue from patients with pre-eclampsia (n = 13) compared with fetal growth retardation (n = 14) as age-matched controls. RESULTS: In first trimester tissue, we observed a significant reduction of HO-2 expression in invasive trophoblast cells, endothelial cells, and syncytiotrophoblasts in samples from patients with spontaneous abortion compared with normal pregnancy. H-mole samples showed a diminished expression of HO-2 in invasive trophoblast cells and endothelial cells in comparison with NP, whereas choriocarcinoma samples showed no significant differences compared with the control. In third trimester tissue, HO-2 was also reduced in syncytiotrophoblasts and invasive trophoblast cells from pre-eclampsia compared with samples from fetal growth retardation. HO-1 expression was diminished in all pathologies investigated; however, the differences did not reach levels of significance. CONCLUSIONS: Our data indicate that HOs play a crucial role in pregnancy and low expression of HO-2, as observed in pathologic pregnancies, may lead to enhanced levels of free heme at the feto-maternal interface, with subsequent upregulation of adhesion molecules, allowing enhanced inflammatory cells migration to the feto-maternal interface.     

Growth retardation in rat fetuses induced by chlorpromazine hydrochloride (CPZ)

Maternal administration of 100 mg/kg of chlorpromazine hydrochloride on 14th gestation day led to a significant (P less than 0.001) intrauterine growth retardation (IUGR) in rat fetuses collected from 16th--20th days of gestation. Besides weight of the fetus, other measurements were used to assess the stunted growth, e.g. CR length, tail length and trans-umbilical distance (TUD). The latter was as efficacious as the weight since with each one of them the IUGR was found in 88% of fetuses at--2SD level on 20th day of gestation. The different components of the fetal environments, e.g. weight and volume of placenta, length of the umbilical cord, weight and volume of amniotic fluid were also investigated which showed a positive correlation between alteration in the fetal environment and IUGR.     

Expression of vascular endothelial growth factor receptors 1, 2 and 3 in placentas from normal and complicated pregnancies

Extensive angiogenesis and invasion of the maternal decidua by trophoblasts are essential for the development and function of the placenta. Vascular endothelial growth factors (VEGF), placenta growth factor (PlGF) and their receptors VEGFR-1/Flt-1, VEGFR-2/KDR and VEGFR-3/Flt4 have important roles in vasculogenesis and angiogenesis. We have studied the localization of these proteins by immunohistochemistry and Western blotting in the placenta and of PlGF in maternal serum, and their association with diabetes, pre-eclampsia, fetal growth restriction (FGR) and fetal alcohol syndrome (FAS). VEGFR-1 and VEGFR-3 were detected mainly in the syncytiotrophoblastic layer whereas VEGFR-2 was detected in the vascular endothelial cells of the placenta. VEGFR-1, but not the other receptors, showed increased expression in placental syncytiotrophoblasts from 50% of patients with severe pre-eclampsia and FGR when compared with normal placentas. PlGF was undetectable in 38 of 44 samples of amniotic fluid of mothers with normal and complicated pregnancies. However, maternal serum PlGF concentrations were significantly lower in pre-eclamptic patients and in those with FGR when compared to diabetic women or healthy controls. These results suggest that low maternal serum PlGF and increased placental expression of its receptor VEGFR-1 are associated with pre-eclampsia and FGR.     

Placental adaptive responses and fetal programming

Fetal programming occurs when the normal pattern of fetal development is disrupted by an abnormal stimulus or 'insult' applied at a critical point in in utero development. This then leads to an effect, for example diabetes or hypertension, which manifests itself in adult life. As the placenta is the regulator of nutrient composition and supply from mother to fetus and the source of hormonal signals that affect maternal and fetal metabolism, appropriate development of the placenta is crucial to normal fetal development. Placental function evolves in a carefully orchestrated developmental cascade throughout gestation. Disruption of this cascade can lead to abnormal development of the placental vasculature or of the trophoblast. Timing of a developmental 'insult' will be critical in consequent placental function and hence programming of the fetus. The 'insults' that alter placental development include hypoxia and abnormal maternal nutrient status, to which the placenta may adapt by alterations in transporter expression and activity to maintain fetal growth or by epigenetic regulation of placental gene expression. Hypoxia is physiological for organogenesis and placental tissue normally exists in a relatively hypoxic environment, but intrauterine growth restriction (IUGR) and pre-eclampsia are associated with a greater degree of trophoblast hypoxia. The metabolic activity of placental mitochondria leads to oxidative stress even in normal pregnancy which is exacerbated further in IUGR, diabetic and pre-eclamptic pregnancies and may also give nitrative stress known to lead to covalent modification and hence altered activity of proteins. Hypoxia, oxidative and nitrative stress all alter placenta development and may be a general underlying mechanism that links altered placental function to fetal programming.     

血管内皮生长因子及其可溶性血管内皮生长因子受体-1水平与胎儿出生体重

目的本研究通过对比血管内皮生长因子(VEGF)、可溶性血管内皮生长因子受体-1(sFlt-1)水平差异与新生儿出生体重的关系,以探讨其在胎儿出生体重发生中的作用。方法采用免疫组织化学法检测40例分娩正常出生体重儿组(AGA组)、30例高出生体重儿组(LGA组)及30例低出生体重儿组(SGA组)胎盘组织中VEGF、sFlt-1的表达水平。结果①LGA组胎盘组织中VEGF的表达高于AGA组,sFlt-1的表达水平低于AGA组,差异有统计学意义(χ2=21.17,P<0.01)。SGA组胎盘组织中VEGF的表达低于AGA组,sFlt-1的表达水平高于AGA组,差异有统计学意义(χ2=8.44,P=0.04)。②胎盘组织中VEGF的表达水平与胎儿出生体重呈正相关(r=0.427,P<0.01),胎盘组织中sFlt-1的表达水平与胎儿出生体重呈负相关(r=-0.569,P<0.01)。结论孕妇胎盘组织中VEGF及sFlt-1表达水平的变化可能与胎儿出生体重有关。     

Isolation of mesenchymal stem cells of fetal or maternal origin from human placenta

Recently we reported that second-trimester amniotic fluid (AF) is an abundant source of fetal mesenchymal stem cells (MSCs). In this study, we analyze the origin of these MSCs and the presence of MSCs in human-term AF. In addition, different parts of the human placenta were studied for the presence of either fetal or maternal MSCs. We compared the phenotype and growth characteristics of MSCs derived from AF and placenta. Cells from human second-trimester (mean gestational age, 19(+2) [standard deviation, +/- 1(+3)] weeks, n = 10) and term third-trimester (mean gestational age, 38(+4) [standard deviation, +/- 1] weeks, n = 10) AF, amnion, decidua basalis, and decidua parietalis were cultured in M199 medium supplemented with 10% fetal calf serum and endothelial cell growth factor. Cultured cells were immunophenotypically characterized, the adipogenic and osteogenic differentiation capacity was tested, and the growth kinetics were analyzed. The origin of fetal and maternal cells was determined by molecular human leukocyte antigen typing.We successfully isolated MSCs from second-trimester AF, amnion, and decidua basalis as well as term amnion, decidua parietalis, and decidua basalis. In contrast, MSCs were cultured from only 2 out of 10 term AF samples. The phenotype of MSCs cultured from different fetal and maternal parts of the placenta was comparable. Maternal MSCs from second-trimester and term decidua basalis and parietalis showed a significantly higher expansion capacity than that of MSCs from adult bone marrow (p < .05). Our results indicate that both fetal and maternal MSCs can be isolated from the human placenta. Amnion is a novel source of fetal MSCs, likely contributing to the presence of MSCs in AF. Decidua basalis and decidua parietalis are sources for maternal MSCs. The expansion potency from both fetal and maternal placenta-derived MSCs was higher compared with adult bone marrow-derived MSCs.     

Down-regulation of placental transport of amino acids precedes the development of intrauterine growth restriction in rats fed a low protein diet

Intrauterine growth restriction (IUGR) represents an important risk factor for perinatal complications and for adult disease. IUGR is associated with a down-regulation of placental amino acid transporters; however, whether these changes are primary events directly contributing to IUGR or a secondary consequence is unknown. We investigated the time course of changes in placental and fetal growth, placental nutrient transport in vivo and the expression of placental nutrient transporters in pregnant rats subjected to protein malnutrition, a model for IUGR. Pregnant rats were given either a low protein (LP) diet ( n = 64) or an isocaloric control diet ( n = 66) throughout pregnancy. Maternal insulin, leptin and IGF-I levels decreased, whereas maternal amino acid concentrations increased moderately in response to the LP diet. Fetal and placental weights in the LP group were unaltered compared to control diet at gestational day (GD) 15, 18 and 19 but significantly reduced at GD 21. Placental system A transport activity was reduced at GD 19 and 21 in response to a low protein diet. Placental protein expression of SNAT2 was decreased at GD 21. In conclusion, placental amino acid transport is down-regulated prior to the development of IUGR, suggesting that these placental transport changes are a cause, rather than a consequence, of IUGR. Reduced maternal levels of insulin, leptin and IGF-1 may link maternal protein malnutrition to reduced fetal growth by down-regulation of key placental amino acid transporters.     

Mammalian target of rapamycin in the human placenta regulates leucine transport and is down-regulated in restricted fetal growth

Pathological fetal growth is associated with perinatal morbidity and the development of diabetes and cardiovascular disease later in life. Placental nutrient transport is a primary determinant of fetal growth. In human intrauterine growth restriction (IUGR) the activity of key placental amino acid transporters, such as systems A and L, is decreased. However the mechanisms regulating placental nutrient transporters are poorly understood. We tested the hypothesis that the mammalian target of rapamycin (mTOR) signalling pathway regulates amino acid transport in the human placenta and that the activity of the placental mTOR pathway is reduced in IUGR. Using immunohistochemistry and culture of trophoblast cells, we show for the first time that the mTOR protein is expressed in the transporting epithelium of the human placenta. We further demonstrate that placental mTOR regulates activity of the l -amino acid transporter, but not system A or taurine transporters, by determining the mediated uptake of isotope-labelled leucine, methylaminoisobutyric acid and taurine in primary villous fragments after inhibition of mTOR using rapamycin. The protein expression of placental phospho-S6K1 (Thr-389), a measure of the activity of the mTOR signalling pathway, was markedly reduced in placentas obtained from pregnancies complicated by IUGR. These data identify mTOR as an important regulator of placental amino acid transport, and provide a mechanism for the changes in placental leucine transport in IUGR previously demonstrated in humans. We propose that mTOR functions as a placental nutrient sensor, matching fetal growth with maternal nutrient availability by regulating placental nutrient transport.     

Prenatal exposure to excess testosterone modifies the developmental trajectory of the insulin-like growth factor system in female sheep

Experimental elevation of maternal testosterone (T) from 30 to 90 days of gestation leads to intrauterine growth retardation (IUGR) and increased prepubertal growth rate in female lambs. This study tested the hypothesis that prenatal T treatment during mid-gestation alters the trajectory of the fetal insulin-like growth factor (IGF)–insulin-like growth factor binding protein (IGFBP) system to promote IUGR and subsequent postnatal catch-up growth in female lambs. Plasma IGF-I and IGFBPs were measured by radioimmunoassay and Western ligand blot, respectively, on 65, 90 and 140 days (d) of gestation, at birth, ∼5 months (prepubertal, the catch-up growth period), and ∼9.5 months (postpubertal). Northern blot analysis was used to measure hepatic mRNA content of IGF system components during fetal stages. At fetal 65 d, plasma protein and hepatic mRNA content of IGFBP-1, an inhibitor of IGF bioactivity, was elevated in prenatal T-treated fetuses although body weight did not differ. There was a transient increase in plasma IGF-I and IGFBP-3 concentrations at fetal 90 d in prenatal T-treated fetuses. Hepatic IGF-I mRNA and plasma IGFBP-3 content were reduced by 140 d when body weight was reduced in prenatal T-treated fetuses. Plasma IGFBP-2 content was significantly reduced in prenatal T-treated newborns, but by 4 months these females had significantly higher circulating IGF-I and IGFBP-3 concentrations and faster growth rates than control females. After puberty, plasma IGF-I remained elevated in prenatal T-treated females. These findings provide evidence that prenatal T excess programmes the developmental trajectory of the IGF/IGFBP system in female sheep to reduce IGF bioavailability during IUGR and increase IGF bioavailability during prepubertal catch-up growth.