Erythropoietin in amniotic fluid as a marker of chronic fetal hypoxia

Robust increases in erythropoietin production by the hypoxic fetus is a response to protect the brain and other vital organs

Fetal erythropoietin (EPO), in addition to regulating erythropoiesis, has also tissue-protective properties based on its anti-inflammatory, anti-apoptotic, antioxidant, and neurotrophic effects. Notably, EPO concentrations needed for tissue protection are 100-1000 times higher than concentrations needed for regulating erythropoiesis. This dual effect of EPO is based on EPO-receptor (EPO-R) isoforms, which differ structurally and functionally. We hypothesize in this Integrated Mechanism Review that during severe fetal hypoxia the observed, but poorly understood, marked increases of fetal plasma EPO concentrations occur to protect the brain, heart, and other vital fetal organs. We further hypothesize that the concurrent marked increases of EPO in the amniotic fluid during fetal hypoxia, occur to protect newborn infants from necrotizing enterocolitis. This review presents experimental and clinical evidence in support of these hypotheses and points out unknown or poorly understood functions of EPO in the fetus. If these novel hypotheses are correct, the importance of fetal EPO as an antenatal hypoxia biomarker will become apparent. It will also likely point the way to important diagnostic and therapeutic fetal and neonatal interventions.

Erythropoietin and Neonatal Neuroprotection

Certain groups of neonates are at high risk of developing long-term neurodevelopmental impairment and might be considered candidates for neuroprotective interventions. This article explores some of these high-risk groups, relevant mechanisms of brain injury, and specific mechanisms of cellular injury and death. The potential of erythropoietin (Epo) to act as a neuroprotective agent for neonatal brain injury is discussed. Clinical trials of Epo neuroprotection in preterm and term infants are updated.

Erythropoietin in amniotic fluid as a potential marker in distinction between growth restricted and constitutionally small fetuses

OBJECTIVE

To determine if there is any difference in amniotic fluid erythropoietin (EPO) concentration between fetuses small for gestational age (SGA) and appropriate for gestational age (AGA), and between the constitutionally small (CSF) and growth-restricted (GRF) fetuses.

METHODS

EPO concentrations in the amniotic fluid samples were determined by EpoELISA test in 38 pregnancies with SGA and 15 pregnancies with AGA fetuses. In the SGA group we measured Ponderal index (PI) and skin-fold thickness (SFT). If PI and/or SFT were below 10th percentile the neonate was GRF. If both PI and SFT were above 10th percentile the neonate was CSF.

RESULTS

Higher levels of EPO were detected in the SGA in comparison to the AGA fetuses (p < 0.01). EPO concentration was higher in GRF compared to CSF (p < 0.05). The EPO cut-off level between SGA and AGA was 6.81 IU/L (sensitivity 92.3%; specificity 73.3%), and between GRF and CSF was 9.8 IU/L (sensitivity 81%; specificity 80%).

CONCLUSION

The preliminary results of this study suggest that amniotic fluid erythropoietin concentration is elevated in growth-restricted fetuses and could potentially be used for distinction between growth restricted and constitutionally small fetuses. Confirmation of these results on a larger group of pregnant women is needed.

Fetal pulmonary arterial vascular impedance reflects changes in fetal oxygenation at near-term gestation in a nonhuman primate model

OBJECTIVE

We tested the hypothesis that fetal pulmonary arterial circulation reacts to changes in fetal oxygenation status at near-term gestation.

STUDY DESIGN

A total of 20 rhesus macaques underwent fetal Doppler ultrasonography at near-term gestation. Right pulmonary artery (RPA), umbilical artery (UA), ductus arteriosus (DA), and ductus venosus (DV) blood velocity waveforms were obtained, and pulsatility index (PI) values were calculated. Fetal right and left ventricular cardiac outputs were determined. Ultrasonographic data were collected during 3 maternal oxygenation states: room air (baseline), hyperoxemia, and hypoxemia.

RESULTS

Fetal RPA PI values increased (P < .05) during maternal hypoxemia and decreased (P < .05) during maternal hyperoxemia, compared with baseline. Maternal hyperoxemia increased (P < .05) DA PI values from baseline. Fetal cardiac outputs, UA, and DV PI values were not affected.

CONCLUSIONS

Our results demonstrate that at near-term gestation, fetal pulmonary arterial circulation is a dynamic vascular bed that reflects acute and short-term changes in fetal oxygenation.

Trends in maternal BMI, glycaemic control and perinatal outcome among type 1 diabetic pregnant women in 1989-2008

AIMS/HYPOTHESIS

Our objective was to examine the trends in prepregnancy BMI and glycaemic control among Finnish type 1 diabetic patients and their relation to delivery mode and perinatal outcome.

METHODS

We analysed the obstetric records of 881 type 1 diabetic women with a singleton childbirth during 1989-2008. Maternal prepregnancy weight and height were obtained from the maternity cards, where they are recorded as reported by the mother.

RESULTS

Maternal BMI increased significantly during 1989-2008 (p < 0.001). The mean HbA(1c) in the first trimester remained unchanged, but the midpregnancy and the last HbA(1c) before delivery increased (p = 0.009 and 0.005, respectively). Elective Caesarean sections (CS) decreased (p for trend <0.001), while emergency CS increased (p for trend <0.001). The mean umbilical artery (UA) pH decreased in vaginal deliveries (p for trend <0.001). The frequency of UA pH <7.15 and <7.05 increased (p for trend <0.001 and 0.008, respectively). The macrosomia rate remained at 32-40%. Neonatal intensive care unit (NICU) admissions increased (p for trend 0.03) and neonatal hypoglycaemia frequency decreased (p for trend 0.001). In multiple logistic regression analysis, maternal BMI was associated with macrosomia and NICU admission. The last HbA(1c) value before delivery was associated with delivery before 37 weeks' gestation, UA pH <7.15, 1 min Apgar score <7, macrosomia, NICU admission and neonatal hypoglycaemia.

CONCLUSIONS/INTERPRETATION

Self-reported pregestational BMI has increased and glycaemic control during the second half of pregnancy has deteriorated. Poor glycaemic control seems to be associated with the observed increases in adverse obstetric and perinatal outcomes.

Stillbirth in diabetic pregnancies

Pregnancy in women with pregestational diabetes is associated with high perinatal morbidity and mortality. Stillbirth accounts for the majority of cases with perinatal death. Intrauterine growth restriction, pre-eclampsia, foetal hypoxia and congenital malformations may be contributing factors, but more than 50% of stillbirths are unexplained. Majority of stillbirths are characterised by suboptimal glycaemic control during pregnancy. Foetal hypoxia and cardiac dysfunction secondary to poor glycaemic control are probably the most important pathogenic factors in stillbirths among pregnant diabetic women. There is thus a need for new strategies for improving glycaemic control to near-normal levels throughout pregnancy and for preventing and treating hypertensive disorders in pregnancy. Antenatal surveillance tests including ultrasound examinations of the foetal growth rate, kick counting and non-stress testing of foetal cardiac function are widely used. However, future research should establish better antenatal surveillance tests to identify the infants susceptible to stillbirth before it happens.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Amniotic fluid S100B protein and erythropoietin in pregnancies at risk for fetal hypoxia

OBJECTIVE

S100B protein is a biochemical marker for brain injury, and high serum S100B levels have been observed in newborns with birth asphyxia. We hypothesized that the concentration of amniotic fluid erythropoietin, which increases in chronic fetal hypoxia, correlates with amniotic fluid S100B concentration.

STUDY DESIGN

Amniotic fluid samples in 35 pregnancies at high risk for chronic fetal hypoxia were obtained at cesarean section or by amniocentesis done within a median of 2 days before delivery. S100B and erythropoietin concentrations were measured by chemiluminescent immunoassays.

RESULTS

A positive correlation existed between the concentrations of S100B and erythropoietin in the amniotic fluid (r=0.57, p<0.0001). Amniotic fluid S100B concentration was higher (70 ng/l; 33-469, n=17) (median; range) in pregnancies with elevated amniotic fluid erythropoietin (>or= 50 IU/l) than in pregnancies with normal erythropoietin (34 ng/l; 20-340, n=18) (p<0.0001, Mann-Whitney U-test). S100B predicted an elevated amniotic fluid erythropoietin concentration in the study population with the sensitivity of 94% and specificity of 83%.

CONCLUSION

A strong positive correlation exists between amniotic fluid S100B and erythropoietin concentrations in pregnancies at high risk for chronic fetal hypoxia. This suggests that chronic fetal hypoxia increases the intrauterine release of S100B.

Increased fetal plasma and amniotic fluid erythropoietin concentrations: markers of intrauterine hypoxia

Tissue hypoxia is the major stimulus of erythropoietin (EPO) synthesis in fetuses and adults. Since EPO does not cross the placenta and is not stored, fetal plasma and amniotic fluid levels indicate EPO synthesis and elimination. Acutely, the rate and magnitude of the increase in plasma EPO levels correlate with the intensity of hypoxia. Amniotic fluid EPO levels correlate with cord plasma levels in normal and abnormal pregnancies, with fetal plasma EPO levels in humans averaging 2.6 times higher than the corresponding amniotic fluid EPO levels. Recent experimental and clinical studies demonstrate that EPO has neuroprotective effects related to its anti-apoptotic and vascular growth-promoting properties. Although under basal conditions the fetal kidneys are the main site of EPO production, during hypoxia recent experimental data indicate an important role of the placenta. Amniotic fluid EPO levels have been shown to increase exponentially during fetal hypoxia in preeclamptic, diabetic and Rh-immunized pregnancies, to correlate inversely with cord blood pH, pO(2) and base excess and to predict neonatal morbidities and NICU admission. As an indicator of chronic intrauterine hypoxia, fetal EPO measurements have increased our knowledge about the pathogenesis and importance of intrauterine growth restriction, macrosomia, diabetic pregnancy, prolonged pregnancy, meconium staining, fetal hemorrhage, fetal anemia, maternal smoking and alcohol consumption, abnormal fetal heart rate and abnormal Doppler flow patterns. While the clinical utility of fetal amniotic fluid and plasma EPO measurements in the management of high-risk pregnancies and their offspring is promising, adequately powered clinical trials are urgently needed.

Nucleated red blood cells are a direct response to mediators of inflammation in newborns with early-onset neonatal sepsis

OBJECTIVE

The objective of the study was to test the hypothesis that inflammation modulates fetal erythroblastosis and/or the release of nucleated red blood cells (NRBCs) independent of hypoxia or fetal stress. We sought to determine whether fetal inflammation is associated with an elevation in neonatal NRBC count in the setting of inflammation-associated preterm birth.

STUDY DESIGN

The relationships between peripheral NRBC count, histological chorioamnionitis, umbilical cord interleukin (IL)-6, erythropoietin (EPO), cortisol, and acid-base status were analyzed in 68 preterm singletons, born to mothers who had an amniocentesis to rule out infection. Proteomic profiling of amniotic fluid identified presence of intraamniotic inflammation according to established parameters. NRBC counts were assessed within 1 hour of birth. Early-onset neonatal sepsis (EONS) was established based on hematological and microbiological indices. IL-6, EPO, and cortisol levels were measured by immunoassays. Fetal acid-base status was determined within 10 minutes of delivery. Parametric or nonparametric statistics were used.

RESULTS

Fetuses with EONS (n = 19) were delivered at earlier gestational ages (mean +/- SD: 27.1 +/- 2.8 weeks, P = .001) and more often by mothers with intraamniotic inflammation (P = .022) and histological chorioamnionitis (P < .001). Neonates with EONS had higher absolute NRBC counts (P = .011). NRBC counts were directly correlated with cord blood IL-6 levels (P < .001) but not with EPO, cortisol or parameters of acid-base status levels regardless of EONS status. These relationships remained following correction for gestational age, diabetes, intrauterine growth restriction, and steroid exposure.

CONCLUSION

In the setting of inflammation-associated preterm birth and in the absence of hypoxia, elevations in NRBCs in the early neonatal period may be a direct response of exposure to inflammatory mediators in utero.

Epo and other hematopoietic factors

The growth factors erythropoietin and granulocyte-colony stimulating factor have hematopoietic and non-hematopoietic functions. Both are used clinically in their recombinant forms. Both also have interesting tissue-protective effects in other organs, which are unrelated to their hematopoietic functions. They have clinical hematopoietic uses in neonatal populations and in experimental non-hematopoietic research, and clinical potential as neuroprotective or tissue-protective agents.

Malaria during pregnancy and foetal haematological status in Blantyre, Malawi

BACKGROUND

Although maternal anaemia often stems from malaria infection during pregnancy, its effects on foetal haemoglobin levels are not straightforward. Lower-than-expected cord haemoglobin values in malarious versus non-malarious regions were noted by one review, which hypothesized they resulted from foetal immune activation to maternal malaria. This study addressed this idea by examining cord haemoglobin levels in relation to maternal malaria, anaemia, and markers of foetal immune activation.

METHODS

Cord haemoglobin levels were examined in 32 malaria-infected and 58 uninfected women in Blantyre, Malawi, in relation to maternal haemoglobin levels, malaria status, and markers of foetal haematological status, hypoxia, and inflammation, including TNF-alpha, TGF-beta, and ferritin. All women were HIV-negative.

RESULTS

Although malaria was associated with a reduction in maternal haemoglobin (10.8 g/dL vs. 12.1 g/dL, p < 0.001), no reduction in cord haemoglobin and no significant relationship between maternal and cord haemoglobin levels were found. Cord blood markers of haematological and hypoxic statuses did not differ between malaria-infected and uninfected women. Maternal malaria was associated with decreased TGF-beta and increased cord ferritin, the latter of which was positively correlated with parasitaemia (r = 0.474, p = 0.009). Increased cord ferritin was associated with significantly decreased birth weight and gestational length, although maternal and cord haemoglobin levels and malaria status had no effect on birth outcome.

CONCLUSION

In this population, cord haemoglobin levels were protected from the effect of maternal malaria. However, decreased TGF-beta and elevated ferritin levels in cord blood suggest foetal immune activation to maternal malaria, which may help explain poor birth outcomes.

Association between erythropoietin in cord blood of twins and size at birth: does it relate to gestational factors or to factors during labor or delivery?

We hypothesized that cord blood erythropoietin (EPO), a marker of fetal hypoxia, relates to gestational factors and not solely those associated with delivery. We investigated the association between birth weight SD score (SDS) and cord blood EPO in 290 twins (145 pairs), assessing the influence of gestational versus perinatal factors by comparing the association in those who were delivered by elective cesarean (CS) with that in other delivery modes. Blood EPO values were skewed, so geometric means are presented and log EPO values were used in statistical models. The birth size-EPO association was estimated in mixed-effects models that included terms that represented difference in log EPO and mean log EPO for each twin pair. Within-pair estimates of the association were unconfounded by maternal factors (because these were perfectly controlled). Geometric mean EPO was higher in boys versus girls (24.4 versus 17.0 IU/L; p = 0.0001) and increased with gestational age (p = 0.0003) but was similar after elective CS versus other delivery modes. The negative birth size-EPO association was stronger in infants who were delivered by elective CS than by other delivery modes [beta for log(2) EPO: -0.56 (95% CI, -0.77 to -0.36) versus -0.27 (-0.42 to -0.12), respectively; p = 0.02 for interaction). Because the association was seen after elective CS delivery, cord blood EPO must relate to factors during gestation, not just perinatal factors. There was no evidence of an association between birth weight SDS and pair mean log EPO, indicating that the association is entirely due to fetus-specific rather than pair-specific factors.

High amniotic fluid erythropoietin levels are associated with an increased frequency of fetal and neonatal morbidity in type 1 diabetic pregnancies

AIMS/HYPOTHESIS

In this study we investigated whether chronic fetal hypoxia, as indicated by amniotic fluid erythropoietin levels, is associated with perinatal morbidity in type 1 diabetic pregnancies.

METHODS

A total of 331 women with type 1 diabetes had at least one childbirth between 1995 and 2000. The amniotic fluid erythropoietin concentration was measured in 156 diabetic singleton pregnancies at a median time of 1 day before Caesarean section without labour contractions and in 19 healthy control subjects at Caesarean section.

RESULTS

The median amniotic fluid erythropoietin level was 14.0 mU/ml (range 2.0-1975.0) in diabetic pregnancies and 6.3 mU/ml (range 1.7-13.7) in controls (p<0.0001). Of the 156 diabetic patients, 21 (13.5%) had amniotic fluid erythropoietin levels higher than 63.0 mU/ml. Amniotic fluid erythropoietin levels correlated negatively with umbilical artery pH (r=-0.49, p<0.0001) and pO2 (r=-0.62, p<0.0001) at birth and neonatal lowest blood glucose level (r=-0.47, p<0.0001). Positive correlations were found between amniotic fluid erythropoietin levels and umbilical artery pCO2 (r=0.49, p<0.0001) and last maternal HbA1c (r=0.43, p<0.0001). Furthermore, a U-shaped correlation was demonstrated between amniotic fluid erythropoietin levels and birthweight z score (z score below -0.6 SD units: r=-0.63, p=0.0007; z score above +1.0 SD units: r=0.32, p=0.0014). Neonatal hypoglycaemia, hypertrophic cardiomyopathy and admission to the neonatal intensive care unit occurred significantly more often in cases with high amniotic fluid erythropoietin levels (>63.0 mU/ml) than in those with normal levels. Multivariate logistic regression analysis revealed that amniotic fluid erythropoietin was the only variable independently related to low umbilical artery pH (<7.21; p<0.0001) and neonatal hypoglycaemia (p=0.002). Low umbilical artery pO2 (<15.0 mm Hg) was explained by amniotic fluid erythropoietin (p<0.0001) and birthweight z score (p=0.004).

CONCLUSIONS/INTERPRETATION

Antenatal high amniotic fluid erythropoietin levels can identify type 1 diabetic pregnancies at increased risk of severe perinatal complications.

Amniotic fluid and cord plasma erythropoietin levels in pregnancies complicated by preeclampsia, pregnancy-induced hypertension and chronic hypertension

AIMS

The purpose of the present study was to compare fetal and neonatal outcomes with amniotic fluid erythropoietin (EPO) levels obtained in the antepartum period in pregnancies complicated by preeclampsia, pregnancy-induced hypertension or chronic hypertension.

METHODS

Erythropoietin concentrations were measured in amniotic fluid within 2 days before delivery and in cord blood at birth in 75 hypertensive women and in 23 healthy controls delivered by cesarean section before labor contractions. Erythropoietin levels did not influence clinical decisions.

RESULTS

Amniotic fluid erythropoietin levels correlated highly significantly with cord plasma EPO levels and were significantly higher in pregnancies complicated by hypertension than in control pregnancies. Umbilical arterial pH, acid-base and blood gas values at birth were not different from controls. Both cord plasma and amniotic fluid erythropoietin levels correlated with cord blood pH, acid-base and blood gas values at birth in the study group. Newborn infants admitted to the newborn intensive care unit had significantly higher fetal erythropoietin levels and were more acidotic, hypoxemic and hypoglycemic than infants admitted to the normal care nursery.

CONCLUSIONS

Our findings suggest that elevated amniotic fluid erythropoietin levels are markers of chronic or subchronic fetal hypoxia and are associated with neonatal morbidity in pregnancies complicated by hypertension.

Does erythropoietin protect the preterm brain?

There is a high incidence of hypoxic-ischaemic brain injury and intraventricular haemorrhage in newborn infants, particularly those born preterm. Many die during the newborn period or suffer permanent neurodevelopmental handicaps. Hypoxic brain injury develops over several hours and could potentially be influenced by intervention. At present, no drug exists that effectively prevents infant brain injury or ameliorates detrimental neurodevelopmental effects. The hypothesis is put forward that systemic administration of recombinant human erythropoietin positively affects the neurodevelopmental outcome of high risk preterm infants affected by brain injury. A multicentre, randomised, placebo controlled study is proposed to prospectively test this hypothesis.

Total protein concentration in human amniotic fluid is negatively associated with infant birth weight

Our objectives were 2-fold: 1) to assess the concentration and distribution of total protein in human amniotic fluid (AF) using 3 standard assays [Bradford, bicinchoninic acid solution (BCA), and Lowry] and 2) to establish whether these total protein concentrations were associated with and predictive of infant birth weight. Birth outcomes were determined using recently developed birth-weight-for-gestational-age categories (percentiles) for fetal growth where infants < 10% were classified as SGA (small-for-gestational-age), those between 10 and 90% as appropriate-for-gestational-age (AGA) and those infants >/= 90% as large-for-gestational-age (LGA). AF samples were collected from women undergoing routine amniocentesis for genetic testing (mean = 15 +/- 0.04 wk, range 12-20 wk), frozen, and later analyzed for total protein in 617 singleton-expectant mothers in Montréal, QC, Canada. Maternal and fetal characteristics were obtained from questionnaires and medical chart review. Mothers giving birth to LGA infants had uniformly lower AF protein concentrations at 12-20 wk gestation compared with AF protein concentrations for mothers of AGA infants. Multiple regression analyses demonstrated that total AF protein, collected during routine amniocentesis and later analyzed by the Lowry method, was negatively associated with birth weight at term in our population. These data suggest that one or more AF proteins might emerge as biomarkers of fetal growth.

Endogenous and recombinant erythropoietin levels decline in human amniotic fluid and fetal plasma in vitro at 37 degrees C

OBJECTIVE

To determine the in vitro stability of endogenous and recombinant erythropoietin (EPO) incubated at 37 degrees C in amniotic fluid (AF) and fetal plasma.

STUDY DESIGN

Endogenous and recombinant EPO in AF, fetal plasma and phosphate buffer were incubated in vitro for 21 days at 37 degrees C. Serial aliquots were analyzed for EPO and the rates of EPO decline were compared within and between groups.

RESULTS

Endogenous and recombinant EPO declined significantly in plasma and AF at 37 degrees C. Endogenous EPO displayed a similar linear rate of decline in AF and plasma, with nearly 70% of the initial hormone concentration remaining at 21 days. Recombinant EPO incubated in buffer did not change.

CONCLUSIONS

Using the rate of decline in endogenous EPO we observed, EPO levels measured in AF or plasma within 21 days of fetal demise can be extrapolated back to the level likely present at fetal death.

Amniotic fluid erythropoietin concentrations differentiate between acute and chronic causes of fetal death

BACKGROUND

Increased fetal plasma erythropoietin concentration is an indicator of chronic fetal hypoxia. Amniotic fluid erythropoietin levels correlate highly significantly with fetal erythropoietin levels before labor. We studied AF erythropoietin levels after fetal death in order to determine whether this could differentiate between stillbirths from acute or chronic causes.

METHODS

Amniotic fluid was obtained after fetal death for erythropoietin measurement following fetal death in 21 pregnancies. Two of the pregnancies had twins, of which one infant was born alive. All 22 stillborn fetuses had an autopsy. None had malformations. Without prior knowledge of the results of the erythropoietin analyzes, the causes of fetal death were divided into acute, chronic or unknown groups.

RESULTS

Eight pregnancies had an acute cause of fetal death (e.g. cord complication or placental abruption), eight pregnancies had a chronic cause (intrauterine growth restriction or erythroblastosis) and in five pregnancies the cause of fetal death could not be determined. In all eight pregnancies with an acute cause of fetal death, AF erythropoietin levels were normal (< 20 mU/mL). In contrast, six of the eight pregnancies with a chronic cause had AF erythropoietin levels above normal (range from 49.9 mU/mL to 391 mU/mL). In the five pregnancies with an unknown cause of fetal death, AF erythropoietin levels were normal in three and elevated in two.

CONCLUSIONS

Elevated AF erythropoietin levels, identified after fetal death, suggest that the fetus died from a chronic hypoxic event, whereas normal AF erythropoietin levels suggest that the fetus died from an acute event.

Expression of erythropoietin mRNA, protein and receptor in ovine fetal membranes

Erythropoietin and its receptor have been identified in human, murine and ovine placentas. Based on the common embryonic origin of the placenta and fetal membranes, we postulated that erythropoietin is similarly expressed in the fetal membranes. Using in situ hybridization and immunohistochemistry, we tested the hypothesis that ovine fetal membranes are sites of erythropoietin production and action. At 86, 103 and 138 days gestation, erythropoietin mRNA and protein were present in the amnion localized to the cell layer consisting largely of amniotic epithelium and in the chorion localized to the chorionic columnar cells consisting of cytotrophoblasts. Binucleate cells, differentiated cytotrophoblasts known to produce hormones, were identified in the chorion in the region of erythropoietin expression but were not observed in amniotic tissue. The erythropoietin receptor protein was present in the amnion and chorion at 103 and 138 days gestation but was not observed in either tissue at 86 days. In summary, erythropoietin appears to be produced as well as utilized within the ovine amnion and chorion. Within the amnion, the amniotic epithelial cells express the erythropoietin gene whereas, within the chorion, either the cytotrophoblasts or the binuclear cells may be the source. Due to the presence of the receptor, we speculate that the erythropoietin produced in the membranes may mediate fetal membrane function and/or growth through an autocrine and/or paracrine mechanism. Further, the fetal membranes may be the source of erythropoietin in the amniotic fluid.

Stability of filgrastim and epoetin alfa in a system designed for enteral administration in neonates

OBJECTIVE

To determine the stability of recombinant granulocyte colony-stimulating factor (rG-CSF, filgrastim) and recombinant erythropoietin (rEpo, epoetin alfa) in a solution designed for enteral administration in the neonatal intensive care unit.

DESIGN

Filgrastim and epoetin alfa were added to a solution with NaCl 0.9%, sodium acetate, potassium chloride, and human albumin in concentrations designed to mimic human amniotic fluid. Additionally, the solution was dripped through polyvinyl chloride feeding tubes to simulate feedings, and aliquots were collected before, during, and after priming of the tube. Other aliquots were either frozen immediately, stored at room temperature, or refrigerated for 0, 6, 12, 18, and 24 hours.

MAIN OUTCOME MEASURES

Filgrastim and epoetin alfa concentrations in the various aliquots were compared with the concentrations in the original solution.

RESULTS

Filgrastim and epoetin alfa concentrations were stable for at least 24 hours when refrigerated and for at least three weeks when frozen. At room temperature, filgrastim was stable for 18 hours and epoetin alfa for 24 hours. Filgrastim concentrations did not vary significantly before, during, or after priming of the feeding tube, whereas epoetin alfa concentrations decreased significantly unless the feeding tube was primed with 10 mL of solution.

CONCLUSIONS

Filgrastim and epoetin alfa were stable in our amniotic fluid-like solution. In this respect, our solution is suitable for enteral administration to patients in the neonatal intensive care unit.

Erythropoietin in the cerebrospinal fluid of neonates who sustained CNS injury

We previously reported that erythropoietin (Epo) is present in human cerebrospinal fluid (CSF). It is not known whether CSF Epo concentrations change under conditions of CNS injury or, if so, whether this change reflects loss of blood-brain barrier integrity or increased CNS Epo synthesis. We hypothesized that CSF Epo increases in conditions of neural injury including hypoxia, meningitis, and intraventricular hemorrhage (IVH) and that CSF Epo concentrations are independent of plasma Epo concentrations. To test these hypotheses, Epo concentrations were measured in 122 paired CSF and blood samples obtained from neonates and children categorized as follows: 16, asphyxia; 31, meningitis; 11, IVH; 41, controls. Twelve infants treated with recombinant Epo (rEpo) and 11 additional samples from children with miscellaneous neurologic problems were also evaluated. CSF and plasma Epo concentrations were significantly higher in asphyxiated infants than in controls (225.0+/-155.0 versus 4.5+/-0.5 mU/mL; mean +/- SEM, p < 0.05, respectively, in CSF; 1806.7+/-1254 versus 5.2+/-0.5, p < 0.05 in plasma). Neonates with IVH had higher CSF Epo concentrations than controls (p < 0.01) but did not have higher plasma Epo concentrations than controls. Patients with meningitis did not have elevated CSF or plasma Epo concentrations. There was no correlation between CSF and plasma Epo concentrations in infants treated with rEpo. We conclude that Epo is selectively increased in the CSF by hypoxia, less so by IVH, and not at all by meningitis. rEpo treatment does not elevate CSF Epo. These findings suggest that rEpo does not cross the blood-brain barrier and that hypoxia induces increased CNS synthesis of Epo.