Experimental growth retardation produced by transient period of uteroplacental ischemia in pregnant Sprague-Dawley rats

Molecular Pathways of Altered Brain Development in Fetuses Exposed to Hypoxia

Perinatal hypoxia is a major cause of neurodevelopmental impairment and subsequent motor and cognitive dysfunctions; it is associated with fetal growth restriction and uteroplacental dysfunction during pregnancy. This review aims to present the current knowledge on brain development resulting from perinatal asphyxia, including the causes, symptoms, and means of predicting the degree of brain damage. Furthermore, this review discusses the specificity of brain development in the growth-restricted fetus and how it is replicated and studied in animal models. Finally, this review aims at identifying the least understood and missing molecular pathways of abnormal brain development, especially with respect to potential treatment intervention.

Growth arrest-specific protein-6/AXL signaling induces preeclampsia in rats†

Preeclampsia (PE) is a complicated obstetric complication characterized by increased blood pressure, decreased trophoblast invasion, and inflammation. The growth arrest-specific 6 (Gas6) protein is known to induce dynamic cellular responses and is elevated in PE. Gas6 binds to the AXL tyrosine kinase receptor and AXL-mediated signaling is implicated in proliferation and migration observed in several tissues. Our laboratory utilized Gas6 to induce preeclamptic-like conditions in pregnant rats. Our objective was to determine the role of Gas6/AXL signaling as a possible model of PE. Briefly, pregnant rats were divided into three groups that received daily intraperitoneal injections (from gestational day 7.5 to 17.5) of phosphate buffered saline (PBS), Gas6, or Gas6 + R428 (an AXL inhibitor administered from gestational day 13.5 to 17.5). Animals dispensed Gas6 experienced elevated blood pressure, increased proteinuria, augmented caspase-3-mediated placental apoptosis, and diminished trophoblast invasion. Gas6 also enhanced expression of several PE-related genes and a number of inflammatory mediators. Gas6 further enhanced placental oxidative stress and impaired mitochondrial respiration. Each of these PE-related characteristics was ameliorated in dams and/or their placentae when AXL inhibition by R428 occurred in tandem with Gas6 treatment. We conclude that Gas6 signaling is capable of inducing PE and that inhibition of AXL prevents disease progression in pregnant rats. These results provide insight into pathways associated with PE that could be useful in the clarification of potential therapeutic approaches.

The investigation of calpain in human placenta with fetal growth restriction

PROBLEM

The mechanism of fetal growth restriction (FGR) is not fully understood. In this study, we explored the contribution of the calpain-calpastatin system and the activated states of calpains in human FGR placenta.

METHOD OF STUDY

The placentas were collected from patients of FGR (n = 17) and controls (n = 23) at elective cesarean sections in Nagoya City University Hospital and used for experiments upon informed consent. The existence and the expression of calpains and calpastatin in human placenta were compared between FGR and controls using immunohistochemistry, SDS-PAGE, and Western blotting.

RESULTS

Staining of calpains (pre-, post-μ-calpain, pre-, post-m-calpain, and calpain-6) and calpastatin was observed in cytoplasm of trophoblast cells, both in FGR and control placenta. Pre-μ-calpain was located in the cytoplasm, and post-μ-calpain was located mainly in proximity to the cytoplasmic membrane. The expression of pre-μ-calpain was significantly higher (P < .001) and calpain-6 was significantly lower (P = .01) in FGR placentas. The inactive μ-calpain (80 kDa) was significantly elevated (P < .01), and active μ-calpain (76 kDa) was significantly decreased (P = .01) in FGR placentas.

CONCLUSION

The results demonstrate that activation of μ-calpain is suppressed in FGR placentas and that calpain-6 in human placenta is involved in the pathology of FGR.

Animal models for neonatal brain injury induced by hypoxic ischemic conditions in rodents

Neonatal hypoxia-ischemia and resulting encephalopathies are of significant concern. Intrapartum asphyxia is a leading cause of neonatal death globally. Among surviving infants, there remains a high incidence of hypoxic-ischemic encephalopathy due to neonatal hypoxic-ischemic brain injury, manifesting as mild conditions including attention deficit hyperactivity disorder, and debilitating disorders such as cerebral palsy. Various animal models of neonatal hypoxic brain injury have been implemented to explore cellular and molecular mechanisms, assess the potential of novel therapeutic strategies, and characterize the functional and behavioural correlates of injury. Each of the animal models has individual advantages and limitations. The present review looks at several widely-used and alternative rodent models of neonatal hypoxia and hypoxia-ischemia; it highlights their strengths and limitations, and their potential for continued and improved use.

Effect of carbamylated erythropoietin on neuronal apoptosis in fetal rats during intrauterine hypoxic-ischemic encephalopathy

Background

Hypoxic-ischemic encephalopathy (HIE) is a common disease that occurs during the perinatal period. The primary cause of neonatal HIE is related to fetal intrauterine anoxia. Carbamylated erythropoietin (CEPO), a derivative of erythropoietin (EPO), does not exert any erythropoietic effect; however, the neuroprotective effects resemble those of EPO. Previous studies have shown the potential benefits of CEPO on the central nervous system. The present study aimed to investigate the role of CEPO in neuronal apoptosis during intrauterine HIE and the underlying mechanisms.

Results

To validate our hypothesis, we established an intrauterine HIE model by occluding the bilateral utero-ovarian arteries of pregnant Sprague–Dawley rats. Compared to the I/R group, neuronal apoptosis in the CEPO group was significantly lower at 4, 12, 24, and 48 h (P < 0.05). CEPO significantly inhibited CC3 expression (P < 0.05) during the early-stages after ischemia–reperfusion (0.5, 4, 8, 12 and 24 h), upregulated Bcl-2 expression, and downregulated Bax expression at 4, 8, 12, and 24 h (P < 0.05).

Conclusions

Carbamylated erythropoietin pretreatment inhibited the expression of proapoptotic protein CC3 in brain and regulated the Bcl-2/Bax ratio, resulting in reduced neuronal apoptosis and thus resulting in a protective effect on intrauterine HIE.

Evaluation of magnesium sulfate effects on fetus development in experimentally induced surgical fetal growth restriction in rat

Objective: The objective of this study was to evaluate the effect of magnesium sulfate in the prevention of fetal growth restriction due to the impaired uterine blood supply in the rat model.Methods: A total number of 24 female rats were used in this study. They were mated overnight and randomly divided into control and treatment groups. After anesthesia and incising abdominal midline in day 17 of gestation, the uterine artery was occluded by an atraumatic clamp for 60 min. The rats of the control group received normal saline after surgery and the rats of treatment group received magnesium sulfate subcutaneously. The laparotomy was repeated on day 21 of gestation, and the number of alive and dead fetuses was counted in each horn. The viability of fetuses was evaluated. The weight of the placenta and fetuses and the distance between the head and tail as well as back to the abdomen of the fetuses were also measured. Samples of the amniotic fluid (AF) were collected during both surgeries for biochemical analyses of the glucose, urea, lactate, and pyruvate levels by an AutoAnalyzer.Results: Among the total fetuses in ischemic horn, only 50% survived in the control group. Dead fetuses had less body consistency and had a dark color. In contrary, only 7.6% of the fetuses in the treatment group were absorbed and 92.4% were completely healthy and developed. Parameters related to placenta weight, fetus weight, fetus length, and fetus width had significant differences and those of the treatment group were higher. Glucose and lactate levels of the AF in the treatment group were significantly lower and urea level was significantly higher than the control group in day 21 of gestation. The changes in pyruvate levels were not significant.Conclusion: In conclusion, magnesium sulfate may counteract with the effects of temporary uterine ischemia in pregnant rats and prevent intrauterine growth restriction.

Fetal Growth Restriction Induced by Transient Uterine Ischemia-Reperfusion: Differential Responses in Different Mouse Strains

We characterized fetal and placental growth and uterine and placental inflammation in pregnant C3H/HeOuJ and C57BL/6J mice (strains with different sensitivities to metabolic and circulatory pathologies), using different uterine ischemia/reperfusion (I/R) protocols, to establish and refine a murine model of I/R-induced fetal growth restriction (FGR). Pregnant C3H/HeOuJ mice on gestation day 15 were subjected to unilateral uterine I/R by (1) total blood flow restriction (TFR) by occlusion of the right ovarian and uterine arteries for 30 minutes, (2) partial flow restriction (PFR) by occlusion of only the right ovarian artery for 30 minutes, or (3) sham surgery. Pregnant C57BL/6J mice were treated the same, but on gestation day 14 and with TFR for only 5 minutes due to high sensitivity of C57BL/6J mice to I/R. Four days post-I/R, the animals were euthanized to determine fetal and placental weight and fetal loss and to assay placental myeloperoxidase (MPO) activity. In C3H/HeOuJ mice, TFR/30 minutes induced significantly ( P < .05) lower fetal and placental weights and higher placental MPO activity, compared to controls. The PFR/30 minutes produced the same effects except placental weights were not reduced. In contrast, in C57BL/6J mice, TFR for only 5 minutes was sufficient to induce FGR and increase fetal loss; while PFR/30 minutes lowered fetal but not placental weights and increased fetal loss but not placental MPO activity. In summary, we present the first published model of I/R-induced FGR in mice. We find that mice of different strains have differing sensitivities to uterine I/R, therefore differing I/R response mechanisms.

Mild intrauterine hypoperfusion reproduces neurodevelopmental disorders observed in prematurity

Severe intrauterine ischemia is detrimental to the developing brain. The impact of mild intrauterine hypoperfusion on neurological development, however, is still unclear. We induced mild intrauterine hypoperfusion in rats on embryonic day 17 via arterial stenosis with metal microcoils wrapped around the uterine and ovarian arteries. All pups were born with significantly decreased birth weights. Decreased gray and white matter areas were observed without obvious tissue damage. Pups presented delayed newborn reflexes, muscle weakness, and altered spontaneous activity. The levels of proteins indicative of inflammation and stress in the vasculature, i.e., RANTES, vWF, VEGF, and adiponectin, were upregulated in the placenta. The levels of mRNA for proteins associated with axon and astrocyte development were downregulated in fetal brains. The present study demonstrates that even mild intrauterine hypoperfusion can alter neurological development, which mimics the clinical signs and symptoms of children with neurodevelopmental disorders born prematurely or with intrauterine growth restriction.

Endothelin Receptor A Antagonism Prevents Damage to Glycogen-Rich Placental Cells Following Uterine Ischemia-Reperfusion in the Rat

Fetal growth restriction (FGR) is a common cause of perinatal morbidity and mortality. Suboptimal uteroplacental perfusion is the most commonly identified cause of FGR, and ischemic lesions are often observed in placentas from pregnancies complicated by FGR. Ischemia followed by reperfusion is a strong stimulus to the production of the vasoconstrictor endothelin 1 (ET-1) which has been implicated in several models of FGR. We sought to investigate oxidative stress and placental morphology in a rat model of ischemia-reperfusion (I/R)-induced FGR and to evaluate the role of ET-1 in the observed pathology. Unilateral uterine I/R (30 min) was conducted, with and without simultaneous ET-1 receptor A (ET_A) antagonism, on pregnant rats at gestation day 17. Placental tissues collected 24 hours later were evaluated immunohistochemically for oxidative damage. Tissue pathology was studied using quantitative morphometry. Glycogen-rich cellular areas in the placental junctional zone exhibited only 50% intact cells (P < .001) in both uterine horns following unilateral I/R, compared to controls. ET_A antagonism prevented damage to the glycogen-rich cellular areas. Oxidative damage in response to I/R was prominent in the labyrinthine layer in both uterine horns and was not affected by ET_A antagonism. We conclude that glycogen-rich cellular areas of the placental junctional zone are particularly vulnerable to damage from uterine I/R in the rat. Nucleic acid oxidative damage in the labyrinth is a prominent effect of uterine I/R. ET_A antagonism protects placental cellular integrity during I/R challenge but does not prevent nucleic acid oxidative damage.

Hypoxia reduces placental mTOR activation in a hypoxia-induced model of intrauterine growth restriction (IUGR)

Mammalian target of rapamycin (mTOR) is a protein that regulates cell growth in response to altered nutrient and growth factor availability. Our objective was to assess activated mTOR and its intracellular intermediates p70, and 4EBP1 in placental and invasive trophoblast cells in a hypoxia‐induced model of intrauterine growth restriction (IUGR) in rats. Rats were treated with hypoxia (9%) for 4 days. Placental and fetal weights, as well as conceptus numbers were recorded at the time of necropsy. Immunohistochemistry was used to determine the level of trophoblast invasion and apoptosis. Western blots were used to determine the activation of mTOR, p70, and 4EBP1 in the placenta and the uterine mesometrial compartment. We observed (1) decreased placental (21%) and fetal (24%) weights (P < 0.05); (2) decreased trophoblast invasion; (3) significantly increased active 4EBP1 (28%; P < 0.05) in invasive trophoblast cells yet no changes in the activation of mTOR and p70 proteins; and (4) a significant decrease in the activation of mTOR (48%; P < 0.05) with no differences in p70 or 4EBP1 activation in the placenta. We conclude that the development of IUGR is correlated with decreased activation of the mTOR protein in the placenta and increased 4EBP1 activity in the invading trophoblast. These results provide important insight into the physiological relevance of these pathways. Furthermore, modification of these and other related targets during gestation may alleviate IUGR severity.

Maternal omega-3 fatty acid intake increases placental labyrinthine antioxidant capacity but does not protect against fetal growth restriction induced by placental ischaemia-reperfusion injury

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders. Oxidative stress occurs when excess reactive oxygen species (ROS) damages cellular components, an outcome limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) also limits ROS production. We recently reported that maternal dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation reduced placental oxidative damage and enhanced fetal and placental growth in the rats. Here, we examined the effect of n-3 PUFAs on placental antioxidant defences and whether n-3 PUFA supplementation could prevent growth restriction induced by placental ischaemia-reperfusion (IR), a known inducer of oxidative stress. Rats were fed either standard or high-n-3 PUFA diets from day 1 of pregnancy. Placentas were collected on days 17 and 22 in untreated pregnancies (term=day 23) and at day 22 following IR treatment on day 17. Expression of several antioxidant enzyme genes (Sod1, Sod2, Sod3, Cat, Txn1 and Gpx3) and Ucp2 was measured by quantitative RT-PCR in the placental labyrinth zone (LZ) and junctional zone (JZ). Cytosolic superoxide dismutase (SOD), mitochondrial SOD and catalase (CAT) activities were also analyzed. Maternal n-3 PUFA supplementation increased LZ mRNA expression of Cat at both gestational days (2- and 1.5-fold respectively; P<0.01) and female Sod2 at day 22 (1.4-fold, P<0.01). Cytosolic SOD activity increased with n-3 PUFA supplementation at day 22 (1.3-fold, P<0.05). Sod1 and Txn1 expression decreased marginally (30 and 22%, P<0.05). JZ antioxidant defences were largely unaffected by diet. Despite increased LZ antioxidant defences, maternal n-3 PUFA supplementation did not protect against placental IR-induced growth restriction of the fetus and placental LZ.

Decreased birth weight in psychosis: influence of prenatal exposure to serologically determined influenza and hypoxia

BACKGROUND

Decreased birth weight (BW) is associated with later psychosis, but the sources of decreased BW for those at risk for psychosis remain unclear.

AIM

To determine whether fetal exposure to influenza and/or hypoxia accounts for BW decreases among psychotic cases and controls.

METHOD

Subjects were 111 cases diagnosed with schizophrenia or affective psychosis and 333 matched controls from the Collaborative Perinatal Project. Psychiatric diagnoses were ascertained from medical records. Influenza and hypoxia were determined from maternal and cord sera collected at birth.

RESULTS

Cases exposed to severe fetal hypoxia or influenza had significantly lower BW compared with unexposed cases and controls, regardless of exposure status. No significant differences in BW were observed among controls based on exposure status.

CONCLUSIONS

Decreased BW appears to be a risk factor for psychosis only in the presence of other teratogens. Liability to psychosis likely renders fetuses vulnerable to decreased fetal growth in response to hypoxia and influenza.

Impact of toll-like receptor 4 deficiency on the response to uterine ischemia/reperfusion in mice

Our objective was to determine the role of toll-like receptor 4 (TLR4) in uterine ischemia/reperfusion (I/R)-induced fetal growth restriction (FGR). Pregnant TLR4-deficient and wild-type mice were subjected to I/R or a sham procedure. Fetal and placental weights were recorded and tissues were collected. Pep-1 (inhibits low-molecular-weight hyaluronan (LMW-HA) binding to TLR4) was used to determine whether LMW-HA-TLR4 interaction has a role in FGR. TLR4-deficient mice exhibited significantly lower baseline fetal weights compared with wild-type mice (P<0.05), along with extensive placental calcification that was not present in wild-type mice. Following I/R, fetal and placental weights were significantly reduced in wild-type (P<0.05) but not in TLR4-deficient mice. However, I/R increased fetal loss (P<0.05) only in TLR4-deficient mice. Corresponding with the reduced fetal weights, uterine myeloperoxidase activity increased in wild-type mice (P<0.001), indicating an inflammatory response, which was absent in TLR4-deficient mice. TLR4 was shown to have a regulatory role for two anti-inflammatory cytokines: interferon-B1 decreased only in wild-type mice (P<0.01) and interleukin-10 increased only in TLR4-deficient mice (P<0.001), in response to I/R. Pep-1 completely prevented I/R-induced FGR (P<0.001), indicating a potential role for the endogenous TLR4 ligand LMW-HA in I/R-induced FGR. In conclusion, uterine I/R in pregnancy produces FGR that is dependent on TLR4 and endogenous ligand(s), including breakdown products of HA. In addition, TLR4 may play a role in preventing pregnancy loss after uterine I/R.

EG-VEGF controls placental growth and survival in normal and pathological pregnancies: case of fetal growth restriction (FGR)

Identifiable causes of fetal growth restriction (FGR) account for 30 % of cases, but the remainders are idiopathic and are frequently associated with placental dysfunction. We have shown that the angiogenic factor endocrine gland-derived VEGF (EG-VEGF) and its receptors, prokineticin receptor 1 (PROKR1) and 2, (1) are abundantly expressed in human placenta, (2) are up-regulated by hypoxia, (3) control trophoblast invasion, and that EG-VEGF circulating levels are the highest during the first trimester of pregnancy, the period of important placental growth. These findings suggest that EG-VEGF/PROKR1 and 2 might be involved in normal and FGR placental development. To test this hypothesis, we used placental explants, primary trophoblast cultures, and placental and serum samples collected from FGR and age-matched control women. Our results show that (1) EG-VEGF increases trophoblast proliferation ([(3)H]-thymidine incorporation and Ki67-staining) via the homeobox-gene, HLX (2) the proliferative effect involves PROKR1 but not PROKR2, (3) EG-VEGF does not affect syncytium formation (measurement of syncytin 1 and 2 and β hCG production) (4) EG-VEGF increases the vascularization of the placental villi and insures their survival, (5) EG-VEGF, PROKR1, and PROKR2 mRNA and protein levels are significantly elevated in FGR placentas, and (6) EG-VEGF circulating levels are significantly higher in FGR patients. Altogether, our results identify EG-VEGF as a new placental growth factor acting during the first trimester of pregnancy, established its mechanism of action, and provide evidence for its deregulation in FGR. We propose that EG-VEGF/PROKR1 and 2 increases occur in FGR as a compensatory mechanism to insure proper pregnancy progress.

6-Mercaptopurine-induced histopathological changes and xanthine oxidase expression in rat placenta

The placenta secures the embryo and fetus to the endometrium and releases a variety of steroid and peptide hormones that convert the physiology of a female to that of a pregnant female. Chemical-induced alteration or deviation of placental function in the maternal and extraembryonic tissue can ultimately lead to pregnancy loss, congenital malformation and fetal death. The 6-mercaptopurine (6-MP), an anti-leukemic drug, is known to produce undesired effects on some organs, then the placenta/embryo toxicity of 6-MP was investigated in pregnant rats given 60 mg/kg with two intraperitoneal injections on gestation days (GD) 11 and 12. The rats were sacrificed and their placentas were collected on GD13 or 15. On GD15 small and limb-defected embryos were found in the 6-MP-treated rats. Placental weights were significantly reduced on GD15, as well as a reduced number of cells was detected in the labyrinth zone with both the labyrinth and basal zones having thinned. Cleaved caspase-3-positive cells increased in number in the labyrinth zone, while in the basal zone, glycogen cells reduced with cytolysis. The number of spongiotrophoblasts and trophoblastic giant cells also increased by 6-MP treatment. The 6-MP-treatment resulted in the increased xanthine oxidase (Xdh) expression in the placenta, which gene is related to the ischemic condition of tissues. These data suggest that apoptosis of the labyrinth zone cells may lead to decreased materno-fetal exchange. Moreover, subsequent ischemia in the placental tissue may occur and induce Xdh expression.

Melatonin preserves fetal growth in rats by protecting against ischemia/reperfusion-induced oxidative/nitrosative mitochondrial damage in the placenta

We have previously demonstrated that melatonin protects against ischemia/reperfusion-induced oxidative damage to mitochondria in the fetal rat brain. The purpose of the present study was to evaluate the effects of maternally administered melatonin on ischemia/reperfusion-induced oxidative placental damage and fetal growth restriction in rats. The utero-ovarian arteries were occluded bilaterally for 30 min in rats on day 16 of pregnancy to induce fetal ischemia. Reperfusion was achieved by releasing the occlusion and restoring circulation. Melatonin solution (20 microg/mL) or the vehicle alone was administered orally during pregnancy. A sham operation was performed in control rats, which were treated with vehicle alone. Laparotomy was performed on day 20 of pregnancy and the number and weight of fetal rats and placentas were measured. Placental mitochondrial respiratory control index (RCI), a marker of mitochondrial respiratory activity, was also calculated for each group. Using immunohistochemistry, we investigated the degree of immunostaining of 8-hydroxy-2-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, and redox factor-1(ref-1), which repairs DNA damage and acts as a redox-modifying factor in rat placenta. Predictably, the ischemia/reperfusion operation significantly decreased the weight of fetal rats and placentas and the RCI. Melatonin prevented ischemia/reperfusion-induced changes in RCI (1.55 +/- 0.05 to 1.83 +/- 0.09, P < 0.05) and fetal growth (3.04 +/- 0.17 to 3.90 +/- 0.1, P < 0.0001). Immunohistochemistry revealed significant positive staining for 8-OHdG and ref-1 following ischemia/reperfusion; these effects were also reduced by melatonin treatment. Results indicated that ischemia/reperfusion-induced oxidative placental DNA and mitochondrial damage and fetal growth restriction can be prevented by maternally administered melatonin.

Vasculogenesis and angiogenesis in the IUGR placenta

Placenta vascular formation is important for fetal growth and development. Proper development of the placenta ensures the exchange of oxygen/nutrients and blood flow necessary for fetal growth. In this chapter, we will discuss the processes of vasculogenesis, angiogenesis, and pseudovasculogenesis during placental development and in pregnancies complicated by intrauterine growth restriction. Some of the factors controlling these processes include oxygen, the VEGF family of growth factors, and their receptors. Disruption in the balance of these controlling factors may explain the vascular malformations seen in pregnancies complicated by intrauterine growth restriction.

Role of mitochondrial permeability transition in the immature brain following intrauterine ischemia

Recirculation following 30 minutes of intrauterine ischemia due to uterine artery occlusion has previously been found to be accompanied by delayed deterioration of the cellular bioenergetic state and of mitochondrial function in the fetal rat brain. The objective of this study was to assess whether the delayed deterioration is due to the activation of mitochondrial permeability transition (MPT), which is observed ultrastructurally as mitochondrial swelling. The respiratory activities and ultrastructure of isolated mitochondria and the cellular bioenergetic state in the fetal rat brain were examined at the end of 30 minutes of intrauterine ischemia and after 1, 2, 3 or 4 hours of recirculation. Cyclosporin A (CsA), a potent and specific MPT blocker, or vehicle was given 1 hour after recirculation. In the vehicle-treated animals, the transient ischemia was associated with a delayed deterioration of the cellular bioenergetic state and mitochondrial activities 4 hours of recirculation. The number of swollen mitochondria increased markedly after 4 hours of recirculation. Both the deterioration and swelling were prevented by CsA. The present study indicates that treatment with CsA improves recovery of energy metabolism and inhibits mitochondrial swelling following transient intrauterine ischemia in the fetal brain. The results suggest that mitochondria and MPT may be involved in the development of ischemic brain damage in the immature rat.

Endothelin and platelet-activating factor: significance in the pathophysiology of ischemia/reperfusion-induced fetal growth restriction in the rat

OBJECTIVE

The objective of the study was to evaluate the role of endothelin-1 and platelet-activating factor in ischemia/reperfusion-induced fetal growth restriction in the rat.

STUDY DESIGN

On day 17 of gestation, the right uterine and ovarian arteries were occluded for 30 minutes in experimental but not sham-operated rats. All rats received endothelin receptor A antagonist, A-127722 (10 mg/kg per day), platelet-activating factor antagonist, WEB-2086 (1 mg/kg), or vehicle. On gestational day 21, litter size, fetal viability, and fetal and placental weights were recorded. Reverse transcription-polymerase chain reaction for phospholipase A2-IIA and preproendothelin-1 messenger ribonucleic acid was performed on uterus and placentas from each uterine horn. Groups were compared statistically by analysis of variance.

RESULTS

Ischemia/reperfusion reduced fetal weights, in both the ischemic horn and the nonischemic horn (P < .001). Antagonism of either endothelin receptor A or platelet-activating factor normalized fetal growth in both horns. Neither placental weight nor the incidence of fetal demise was affected by ischemia/reperfusion. Phospholipase A2-IIA and preproendothelin-1 messenger ribonucleic acid expression did not differ between right and left uterine horns in any group. Uterine and placental tissues in the ischemia/reperfusion group exhibited increased phospholipase A2-IIA (P < .01) but not preproendothelin-1.

CONCLUSION

Endothelin-1 and platelet-activating factor are both important mediators in the pathophysiology of ischemia/reperfusion-induced fetal growth restriction in the rat, contributing to the fetal growth restriction observed in both the ischemic and nonischemic horns. Antagonism of either mediator produces normal fetal growth in this model of fetal growth restriction.

Elevation of both cyclooxygenase-2 and prostaglandin E2 receptor EP3 expressions in rat placenta after uterine artery ischemia-reperfusion

Intrauterine growth restriction (IUGR) has a multifactorial pathogenesis and is an important cause of perinatal mortality. The relationship between fetal weight and placental blood flow in an animal model of IUGR has been investigated, showing that fetal growth is regulated by placental blood flow. The aim of the present study was to determine whether ischemia-reperfusion (I/R) injury stimulates the prostaglandin E2 (PGE2) system or the vascular endothelial growth factor (VEGF) system in the placenta of a rat IUGR model. COX-2 is reported to be involved in ischemic damage in many organs. There are 4 types of PGE2 receptor (EP1, EP2, EP3 and EP4). It is well known that EP1 and EP3 is associated with vasoconstriction. In the present study, vessels were occluded in the right uterine horn on day 17 of pregnancy in rats, and the clamps were removed after 30 min of ischemia. At 24h, 48 h, and 5 days after I/R injury, the live fetuses and placentas were obtained by cesarean section. This study revealed that I/R injury caused IUGR 5 days after the treatment. COX-2 expression and EP3 receptor expression were significantly elevated at 24h after I/R injury, but VEGF mRNA expression was not altered in the placenta from the ischemic horn compared with the non-ischemic horn. These results suggested that induction of the COX-2-EP3 system in the placenta may be one of the causes of IUGR induced by uterine ischemia, because the EP3 receptor and PGE2 are well known to mediate vasoconstriction in many organs.

Maternal treatment with MCI-186 does not improve delayed deterioration of cellular bioenergetic state and mitochondrial activity following transient intrauterine ischemia in the fetal rat brain

The mitochondrial respiratory activities and energy metabolism in the fetal rat brain were measured at the end of 30 minutes of intrauterine ischemia and after 2 and 4 hours of recirculation. The transient ischemia was associated with a delayed deterioration of cellular bioenergetic state and mitochondrial activities. The deterioration was not prevented by a free radical scavenger, 3-methyl-1-phenyl-2-pyrazolin-5-one (MCI-186), given immediately after recirculation.

Expression of intestinal trefoil factor, proliferating cell nuclear antigen and histological changes in intestine of rats after intrauterine asphyxia

AIM: To study the expressions of intestinal trefoil factor (ITF) and proliferating cell nuclear antigen (PCNA) and histologic changes in intestine, to investigate the relationship between ITF and intestinal damage and repair after intrauterine hypoxia so as to understand the mechanism of intestinal injury and to find a new way to prevent and treat gastrointestinal diseases.

METHODS: Wistar rats, pregnant for 21 d, were used to establish animal models of intrauterine asphyxia by clamping one side of vessels supplying blood to uterus for 20 min, another side was regarded as sham operation group. Intestinal tissues were taken away at 0, 24, 48 and 72 h after birth and stored in different styles. ITF mRNA was detected by RT-PCR. PCNA expression was measured by immunohistochemistry. Intestinal tissues were studied histologically by HE staining in order to observe the areas and degree of injury and to value the intestinal mucosa injury index (IMDI).

RESULTS: ITF mRNA appeared in full-term rats and increased with age. After ischemia, ITF mRNA was decreased to the minimum (0.59±0.032) 24 h after birth, then began to increase higher after 72 h than it was in the control group (P<0.01). PCNA positive staining located in goblet cell nuclei. The PCNA level had a remarkable decline (53.29±1.97) 48 h after ischemia. Structure changes were obvious in 48-h group, IMDI (3.40±0.16) was significantly increased. Correlation analyses showed that IMDI had a negative correlation with ITF mRNA and PCNA (r = -0.543, P<0.05; r = -0.794, P<0.01, respectively).

CONCLUSION: Intrauterine ischemia can result in an early decrease of ITF mRNA expression. ITF and PCNA may play an important role in the damage and repair of intestinal mucosa.

Increased morbidity in severe early intrauterine growth restriction

OBJECTIVE

To determine the relative frequencies of complications in severe early intrauterine growth-restricted (IUGR) infants.

METHODS

All infants 32 weeks gestation or less with birth weight less than the fifth percentile admitted from January 1991 to December 1998 were identified retrospectively. Two infants were identified for each IUGR case: the subsequent admission with birth weight +/-100 g of the case, and the subsequent admission with the same gestational age. Infants with multiple congenital anomalies, congenital infections or admission after 48 hours of age were excluded. Maternal and neonatal demographic data, neonatal morbidity and mortality until discharge were gathered by chart review.

RESULTS

A total of 39 IUGR identified infants met criteria, with 41 gestational age infants and 33 birth weight infants. Mean birth weights and gestational ages for the IUGR group, gestational age group, and birth weight group were 744 g and 29.6 weeks, 1370 g and 29.7 weeks, and 781 g and 25.5 weeks respectively. Mortality was higher for IUGR infants than gestational age infants (20.5 vs 0%), but less than the birth weight infants (30%). In surviving infants, total ventilator days, total oxygen days, days to full feeds, and patent ductus arteriosis, were higher for IUGR infants than gestational age infants, but less than birth weight infants. Hypoglycemia, direct hyperbilirubinemia, necrotizing enterocolitis (NEC), thrombo-cytopenia, chronic lung disease and feeding difficulties occurred more frequently in IUGR infants than in both other groups. Length of stay for survivors and incidence of retinopathy of prematurity (ROP) was similar for the IUGR and birth weight infants.

CONCLUSIONS

Infants born prematurely who are also severely IUGR have higher neonatal morbidity and mortality when compared to infants of similar gestational age. The surviving IUGR infants had less intraventricular hemorrhage and periventricular leukomalacia than less mature infants of comparable birth weight, but a similar incidence of ROP and length of stay. They had a higher incidence of NEC, direct hyperbilirubinemia and chronic lung disease, probably due to end-organ damage in utero from chronic placental insufficiency. These findings highlight the unique pattern of mortality and morbidity seen in infants with severe early IUGR.

Role of mitochondrial permeability transition in fetal brain damage in rats

Recirculation after transient in utero ischemia has previously been found to be accompanied by delayed deterioration of cellular bioenergetic state and of mitochondrial function in the fetal rat brain. Our objective was to assess whether the delayed deterioration is a result of the activation of mitochondrial permeability transition which is observed ultrastructurally as mitochondrial swelling. The respiratory activities and ultrastructure of isolated mitochondria and the cellular bioenergetic state in fetal rat brain were examined at the end of 30 minutes of in utero ischemia and after 1, 2, 3 and 4 hours of recirculation. Cyclosporin A, a potent and virtually specific mitochondrial permeability transition blocker, or vehicle was administered 1 hour after recirculation. In the vehicle-treated animals, the transient ischemia was associated with a delayed deterioration of cellular bioenergetic state and mitochondrial activities at 4 hours of recirculation. The number of swollen mitochondria increased markedly after 4 hours of recirculation. The deterioration and the swelling were prevented by cyclosporin A. The present study indicates that cyclosporin A treatment improves recovery of fetal brain energy metabolism and inhibits the mitochondrial swelling after transient in utero ischemia. The results suggest that mitochondria and mitochondrial permeability transition may be involved in the development of ischemic brain damage in the immature rat.

Acetylcholine increase in amniotic fluid of experimental rats for intrauterine growth retardation

Previous reports from this laboratory have demonstrated evidence for synthesis and release of acetylcholine (ACh) and catecholamines (CAs) by human amniotic epithelial cells (HAEC) and the presence of ACh and CAs in amniotic fluid. To study the physiological role of amniotic ACh, we used an experimental pregnant rat model for intrauterine growth retardation. Prior to this experiment, we confirmed the presence of choline acetyltransferase in the HAEC by immunocytochemical staining. Amniotic fluid was collected at 48 and 72 h after a transient ligation of the uterine vessels near the lower and upper ends of the right horn of the pregnant rat. The ACh concentration in the amniotic fluid from rats received intrauterine ischemia increased with time to a greater degree compared with the control rat, although the increase was not statistically significant. These results suggest that intrauterine hypoxic conditions cause a tendency to increase ACh concentrations in the amniotic fluid.

Windows of therapeutic opportunity on fetal growth retardation induced by transient intrauterine ischemia in rats

OBJECTIVE

To assess the windows of therapeutic opportunity for drugs with various chemical actions on fetal growth retardation induced by transient intrauterine ischemia in rats.

METHODS

At 17 days of gestation, ischemia was induced by 30 min of right uterine artery occlusion. The administration of either alpha-phenyl-N-tert-butyl-nitrone (PBN), FK 506, nifedipine, or MK-801 to pregnant rats was randomly started before occlusion, 1 hour, 3 hours, or 24 hours after recirculation. All of the pups were delivered by cesarean section at 21 days of gestation and were weighed to determine the degree of fetal growth retardation.

RESULTS

The vehicle-treated animals exposed to ischemia showed a significant decrease in fetal body weight compared with the normoxic control animals. The growth disturbances were prevented by nifedipine and MK-801 only when given just prior to ischemia. In contrast, PBN and FK 506 had a protective effect even when given 1 hour and 3 hours after the start of recirculation, respectively.

CONCLUSIONS

The present results indicate that treatment with PBN and FK 506 gives relatively wide windows of therapeutic opportunity in fetal growth retardation induced by transient intrauterine ischemia in rats and suggest the possibility of therapeutic intervention after the start of recirculation.

Short therapeutic window for nifedipine in transient intrauterine ischemia in fetal rat brain

The aim of this study was to explore whether nifedipine influences the secondary deterioration of cerebral mitochondrial function after transient intrauterine ischemia in fetal rats. Intrauterine ischemia was induced by a 30-min occlusion of the right uterine artery at 20 days of gestation in Wistar rats. Nifedipine (1 mg kg(-1)) or vehicle was injected subcutaneously before the onset of ischemia or 1 h after the start of recirculation. Fetuses were delivered by cesarean section at the end of ischemia (n=6 with vehicle; n=6 with nifedipine pretreatment) or at 4 h of recirculation (n=6 with vehicle; n=6 with nifedipine pretreatment; n=6 with nifedipine posttreatment), and the cerebral mitochondrial respiration was measured polarographically. Tissue oxygen tension was evaluated in placental and fetal cerebral tissues (n=5 with vehicle; n=5 with nifedipine pretreatment). The vehicle treated animals showed a significant decrease in mitochondrial activities at the end of ischemia and 4 h of recirculation. Nifedipine attenuates the secondary deterioration at 4 h of recirculation when given just prior to ischemia, but had no neuroprotective activity when given 1 h after the start of recirculation. Nifedipine pretreatment had no influence on oxygen delivery in placenta and fetal cerebrum during and after ischemia. Despite the short therapeutic window, the treatment of nifedipine attenuates the secondary deterioration of cerebral mitochondrial function after transient intrauterine ischemia in fetal rats when given just prior to ischemia.

Vitamins ameliorate secondary mitochondrial failure in neonatal rat brain

Recirculation after transient intrauterine ischemia has previously been found to be accompanied by secondary mitochondrial dysfunction in the immature rat brain. This study was performed to assess the efficacy of combined treatment with ascorbic acid and alpha-tocopherol in improving secondary brain damage. On the 17th day of gestation, transient intrauterine ischemia was induced by 30 minutes of uterine artery occlusion. Either vehicle, ascorbic acid, alpha-tocopherol, or combination of ascorbic acid and alpha-tocopherol was randomly administered to pregnant rats before and after occlusion. The pups were delivered by cesarean section at 21 days of gestation, and cerebral neocortical tissue was sampled. The mitochondrial respiration was measured polarographically in homogenates. In the ischemia uterine horn, mitochondrial activity of the vehicle treatment decreased significantly to 56% of nonischemic controls. Treatment with ascorbic acid or alpha-tocopherol alone demonstrated a moderate improvement of the secondary mitochondrial dysfunction to 64% and 62% of nonischemic controls, respectively. The combined treatment caused a normalization of mitochondrial activity to 91% of nonischemic controls. These results indicate that combined treatment with ascorbic acid and alpha-tocopherol has a more protective effect against secondary mitochondrial dysfunction after transient intrauterine ischemia compared with the administration of ascorbic acid or alpha-tocopherol alone.

Circadian rhythm of ANP, aldosterone and PRA in normotensive IUGR

OBJECTIVE

Atrial natriuretic peptide (ANP) increases are reported during normal pregnancy, but the relation to arterial pressure and the renin-angiotensin system is debatable. We assessed whether normotensive pregnancies with intrauterine growth retardation (IUGR) present an alteration of maternal ANP levels.

DESIGN

A total of 11 pregnant women with IUGR, in the absence of any other maternal or fetal pathology, entered the study during the third trimester. They were compared with 12 healthy pregnant women of similar age and characteristics. We monitored all subjects for blood pressure (BP), ANP, aldosterone and plasma renin activity (PRA), under the same conditions for 24 h. All subjects were submitted to the same regimen of life; with homogeneous dark : light periods, salt intake and meal times.

METHODS

BP was monitored at 20 min intervals for 24 h and blood tests performed at six time points during the 24 h. EDTA plasma samples were immediately centrifuged. Hormone assays were performed by radioimmunoassay. Koch's nonparametric two-way analysis of variance (ANOVA) was used to compare the hormone time-dependent profiles in the two groups. Circadian rhythms were assessed by cosinor analysis.

RESULTS

The IUGR group was characterized by higher ANP values compared to normal pregnancy, (205 +/- 24 versus 146 +/- 21 pg/ml: P < 0.05) but not significant differences were shown for PRA, aldosterone and BP circadian rhythms.

CONCLUSIONS

This study shows higher ANP values in human pregnancy complicated by IUGR, with presence of normal BP, aldosterone and PRA profiles.

Influence of mild hypothermia on delayed mitochondrial dysfunction after transient intrauterine ischemia in the immature rat brain

The aim of this study was to determine the effect of different maternal thermal conditions during transient intrauterine ischemia on the mitochondrial respiratory activities in the immature rat brain. On 17 days of gestation, transient intrauterine ischemia was induced by 30 min of right uterine artery occlusion under hypothermic (33.5-34.5 degrees C, n=6), normothermic (36.5-37.5 degrees C, n=6), and hyperthermic conditions (39.5-40.5 degrees C, n=6). All of the pups were delivered by cesarean section at 21 days of gestation and cerebral neocortical tissue was sampled 1 h after delivery. The mitochondrial respiration was measured polarographically in homogenates. In the ischemic uterine horn, ADP-stimulated respiration of the normothermia and the hyperthermia groups decreased significantly to 73 and 74% of the non-ischemic controls, respectively. Since non-stimulated respiration remained unchanged, the respiratory control ratio (RCR) of the normothermia and the hyperthermia groups decreased significantly to 59 and 54% of the non-ischemic levels, respectively. In contrast, the mitochondrial respiratory activities of the hypothermia group showed no differences between the non-ischemic and the ischemic uterine horns. The results demonstrate that mild maternal hypothermia ameliorates the cerebral mitochondrial dysfunction in neonatal rats after intrauterine ischemia due to transient uterine artery occlusion and suggest that maternal thermal conditions, particularly during uteroplacental insufficiency, have important implications for the neuropathological outcome of the newborn.

Developmental changes in tolerance to transient intrauterine ischemia in rat cerebral mitochondria

OBJECTIVE

Mitochondfial respiratory activities were measured in neonatal rat brain to compare the influence of transient intrauterine ischemia in the preterm fetus with that in the term fetus and to evaluate the effect of alpha-phenyl-N -tert-butyl-nitrone treatment.

STUDY DESIGN

Intrauterine ischemia was induced by a 30-minute occlusion of the right uterine artery. The control group consisted of term fetuses (20 days old) exposed to normoxia (n = 8) and ischemia (n = 8). For the investigation into maturity effect, preterm fetuses (14 days old) were exposed to normoxia (n = 8) or ischemia (n = 8), and for the alpha-phenyl-N -tert-butyl-nitrone treatment investigation, term fetuses were exposed to ischemia with alpha-phenyl-N -tert-butyl-nitrone (n = 8). All subjects underwent cesarean delivery at 21 days of gestation, and the mitochondrial respiration was measured polarographically 1 hour after delivery.

RESULTS

In the control group the neonatal cortical tissue exposed to ischemia showed a significant decrease in mitochondrial activities compared with those in normoxic control animals. In the preterm group the mitochondrial activities of ischemic fetuses were maintained close to normoxic levels. The neonatal mitochondrial deterioration caused by term ischemia was prevented by alpha-phenyl-N -tert-butyl-nitrone.

CONCLUSION

The results indicate that preterm fetuses are more capable than term fetuses of maintaining mitochondrial function under conditions of transient intrauterine ischemia and suggest that oxygen derived free radicals may play a crucial role in the development of neonatal neurologic deficit.

Role of leukocytes in uterine hypoperfusion and fetal growth retardation induced by ischemia-reperfusion

We investigated leukocyte involvement in uterine hypoperfusion and intrauterine fetal growth retardation (IUGR) induced by ischemia-reperfusion (I/R) in Sprague-Dawley rats. On day 17 of gestation, leukocyte accumulation in the uterus and placenta subjected to 30 min of ischemia, followed by reperfusion, was assessed by measuring myeloperoxidase (MPO) activity. Uterine MPO activity was significantly higher after 1 h of reperfusion than it was before ischemia (P < 0.05), without any increase in placental MPO activity. Immunohistochemical staining showed leukocyte accumulation in the uterus subjected to I/R. The effects of treatment with monoclonal antibodies against CD11a (WT1) and CD18 (WT3) at a dose of 0.8 mg/kg on uterine blood flow and IUGR were investigated. Laser-Doppler flowmetry demonstrated that uterine hypoperfusion at 2 h after ischemia (blood flow, -51.7 +/- 1.2%; P < 0.01) was inhibited by WT1 and WT3 treatment. I/R-induced IUGR at full term (P < 0.05 vs. nonischemic horn) was prevented by WT1 and WT3 treatment on day 17. These results indicate that leukocyte accumulation may play an important role in the pathogenesis of uterine hypoperfusion and IUGR induced by I/R in pregnant rats.

Effect of the immunosuppressant drug FK506 on neonatal cerebral mitochondrial function and energy metabolism after transient intrauterine ischemia in rats

Mitochondrial respiratory activities and energy metabolism were measured in neonatal rat brains to evaluate the influence of transient intrauterine ischemia on the near-term fetus and to assess the effect of the immunosuppressant drug FK506 treatment. Transient intrauterine ischemia was induced by 30 min of right uterine artery occlusion at 17 days of gestation in Wistar rats. The vehicle or 1.0 mg/kg of FK506 was administered after 1 h of recirculation. All of the pups were delivered by cesarean section at 21 days of gestation and samples of cerebral cortical tissue were obtained from pups at 1 h after birth. The mitochondrial respiration was measured polarographically in homogenates. For the analysis of ATP, ADP, and AMP, neonatal brains were frozen in situ and fluorometric enzymatic techniques were used. In the neonatal cortical tissue exposed to ischemia, mitochondrial respiratory activities and ATP concentrations decreased significantly to approximately 59 and 67% of those in normoxic controls, respectively. The deterioration of both mitochondrial respiratory activities and high-energy phosphates was prevented by FK506, given 1 h after the start of recirculation. The present results indicate that transient intrauterine ischemia is accompanied by mitochondrial dysfunction and cellular bioenergetic failure in the neonatal rat brain and suggest that treatment with FK506 prevents the deterioration, even when administered after the ischemic periods.

Secondary mitochondrial dysfunction after transient intrauterine ischemia in the fetal rat brain

OBJECTIVE

Recirculation following transient intrauterine ischemia has previously been found to cause partial recovery and secondary deterioration of cellular bioenergetic states in the fetal rat brain. Our objective was to assess whether secondary bioenergetic failure is due to mitochondrial dysfunction.

STUDY DESIGN

Cerebral cortical tissues were obtained from 20-day-old fetal rats at the end of 30 minutes of intrauterine ischemia (n = 6) and after 1 hour (n = 6), 2 hours (n = 6), and 4 hours (n = 6) of recirculation. Mitochondrial respiratory activities were measured polarographically using homogenates.

RESULTS

Mitochondrial activities decreased to 45% of sham-operated controls at the end of ischemia. Recirculation (1 hour) brought about partial recovery, but continued reflow (2 hours and 4 hours) was associated with a secondary deterioration of mitochondrial activities.

CONCLUSION

The results indicate that although during the early time period after ischemia mitochondrial respiratory capacity is restored, secondary mitochondrial dysfunction develops in the immature rat brain.

Effect of alpha-phenyl-N-tert-butyl nitrone (PBN) on fetal cerebral energy metabolism during intrauterine ischemia and reperfusion in rats

The objective of the present study was to explore whether a free radical spin trap agent, alpha-phenyl-N-tert-butyl nitrone (PBN), influences bioenergetic failure induced in the 20-day-old fetal brain by 30 min of intrauterine ischemia in Wistar rats. Fetal brains were frozen in situ at the end of ischemia and after 1, 2, and 4 h of recirculation for analysis of ATP, ADP, AMP, and lactate. PBN or vehicle was given 1 h after recirculation. Tissue oxygen tension was evaluated in placental and fetal cerebral tissues throughout the whole periods of 30 min of ischemia and 4 h of recirculation. Ischemia was associated with a decrease in ATP concentration and an increase in lactate concentration (p < 0.001). Recirculation (1 and 2 h) led to a recovery of ATP concentration, but continued reflow (4 h) was associated with a secondary deterioration of high-energy phosphates (p < 0.01). Lactate concentration increased during this recovery period. This deterioration was prevented by PBN (p < 0.05). After 30 min of ischemia, tissue oxygen tension in placenta and fetal brain decreased to about 30% and 50% of control, respectively. However, recirculation brought about a recovery of oxygen delivery. The results indicate that although during the early time period after ischemia fetal cerebral energy metabolism is maintained by an acceleration of the anaerobic glycolytic rate, secondary deterioration of cellular bioenergetic state develops in the immature fetal brain. This deterioration may be due to mitochondrial dysfunction, which may be induced by oxygen-derived free radicals, and not by compromised microcirculation.

Angiogenesis and the expression of vascular endothelial growth factor in endometrium and placenta

PROBLEM

The demand for increased angiogenesis and microvascular permeability during cyclical changes in the endometrium and during placentation raises the possibility that aberrations in these events could lead to suboptimal reproductive performance. However, relatively little is presently known regarding the regulation of vascular growth and permeability in these tissues.

METHOD OF STUDY

This review of current literature focuses on the expression, regulation, and potential physiological effects of vascular endothelial growth factor (VEGF) within endometrial and placental tissue.

RESULTS

Spatial and temporal expression of VEGF as well as its restricted specificity, essential role in vasculogenesis/angiogenesis, and ability to induce vascular permeability makes VEGF an attractive regulator of vascular growth and permeability in the endometrium and placenta.

CONCLUSION

A better understanding of the production, regulation, and physiological responses of the vasculature to angiogenic growth factors may lead to new therapeutic strategies for reproductive disturbances secondary to vascular insufficiencies within the female reproductive tract.

Idiopathic fetal growth restriction: a pathophysiologic approach

Known causes of fetal growth restriction (FGR) can be traced in up to 40 percent of the cases. In the remainder of cases, FGR is idiopathic in origin. Evidence from experimental studies, antenatal findings at Doppler velocimetry of the uterine and umbilical arteries, and placental pathology studies suggests that idiopathic FGR can be divided into three groups: 1) primary abnormality in the uteroplacental perfusion; 2) primary abnormality in the fetoplacental perfusion; and 3) abnormal villous structure at the interface between fetal and maternal circulation. An improved understanding of the pathophysiology of idiopathic FGR is crucial to gain insight into its pathogenesis.