The placental-umbilical unit in sickle cell disease pregnancy: A model for studying in vivo functional adjustments to hypoxia in humans

Sickle cell anemia in pregnant Saudi women and its impact on birth weight and gestational maturity

BACKGROUND

It is well documented that sickle cell anemia (SCA) in pregnancy increases the risk of problems that can influence the growth and maturation of the newborn. To assess the gestational maturity and birth weight of babies born to Saudi mothers with SCA in the Jazan region.

METHODS

A case-control study was conducted in three hospitals in the Jazan region. An interview with a semi-structured questionnaire was used to collect data from the participants' women, and then the birth weight was taken.

RESULTS

Of 187 delivered women, 20.3% had SCA (13% had sickle cell disease, and the remaining had sickle cell trait). Among the 38 affected mothers, 15.7% were considered to have an additional risk (7.9% had diabetes mellitus, 5.3% had hypertension, and 2.6% were smokers). The mean birth weight was 2.95 ± 0.40 kg and 2.99 ± 0.55 kg in the case and control groups, respectively. However, the low birth weight babies constitute 31% of the delivered babies in the SCA group with a weight of 2.33 ± 0.16 kg and 15% of the control group with a mean weight of 2.16 ± 0.30 kg. The gestational age was 39.36 ± 1.02 weeks in the SCA group compared to 39.5 ± 1.17 weeks in the control group. Maternal age and hypertension significantly influence the birth weight in the SCA group compared to the influence of diabetes mellitus on the birth weight in the control group.

CONCLUSION

This study indicates that SCA in pregnant mothers influences birth weight, which is more impacted by maternal age and co-morbidities. Therefore, a multidisciplinary approach must monitor these risky pregnancies well to avoid undesirable neonatal outcomes.

Maternal hereditary hemolytic anemia and birth defects in the National Birth Defects Prevention Study

OBJECTIVES

Hereditary hemolytic anemia (HHA) results from genetic mutations that cause red blood cell abnormalities. Little research exists on the relationship between HHA and birth defects. Using data from the National Birth Defects Prevention Study (NBDPS), we described characteristics of HHA-exposed women and estimated associations between HHA during pregnancy and specific birth defects.

METHODS

The NBDPS was a population-based, case-control study of major birth defects and included pregnancies with estimated delivery dates from October 1997 through December 2011. Participants were ascertained from hospital discharge lists or birth defect registries at 10 sites. Trained interviewers collected information about pregnancy exposures via telephone questionnaire. We described characteristics among HHA-exposed women and calculated crude odds ratios and exact 95% confidence intervals for defects with ≥3 exposed cases.

RESULTS

Among 31 HHA-exposed women (28 cases/3 controls), 13 (42%) reported sickle cell anemia, 17 (55%) reported thalassemia, and one (3%) reported hereditary spherocytosis. The average age at delivery for HHA-exposed case women was 27.3 years (range: 17-38). The majority (82%) of HHA-exposed case women reported additional conditions during pregnancy, including hypertension, genitourinary infections, and respiratory illnesses. Additionally, 93% of case women reported using medication during pregnancy. Among the 28 cases, 18 (64%) had isolated birth defects. The defects with ≥3 exposed cases were anencephaly, atrial septal defect, gastroschisis, and cleft palate. Except for anencephaly, the 95% confidence intervals for all estimates were close to or included the null.

CONCLUSION

This hypothesis-generating study adds to the sparse literature on the association between HHA and birth defects.

Main Complications during Pregnancy and Recommendations for Adequate Antenatal Care in Sickle Cell Disease: A Literature Review

Sickle cell disease (SCD) is the most common monogenic disease worldwide, with a variable prevalence in each continent. A single nucleotide substitution leads to an amino-acid change in the β-globin chain, altering the normal structure ofhemoglobin, which is then called hemoglobin S inherited in homozygosity (HbSS) or double heterozygosity (HbSC, HbSβ), and leads to chronic hemolysis, vaso-occlusion, inflammation, and endothelium activation. Pregnant women with SCD are at a higher risk of developing maternal and perinatal complications. We performed a narrative review of the literature considering SCD and pregnancy, the main clinical and obstetrical complications, the specific antenatal care, and the follow-up for maternal and fetal surveillance. Pregnant women with SCD are at a higher risk of developing clinical and obstetric complications such as pain episodes, pulmonary complications, infections, thromboembolic events, preeclampsia, and maternal death. Their newborns are also at an increased risk of developing neonatal complications: fetal growth restriction, preterm birth, stillbirth. Severe complications can occur in patients of any genotype. We concluded that SCD is a high-risk condition that increases maternal and perinatal morbidity and mortality. A multidisciplinary approach during pregnancy and the postpartum period is key to adequately diagnose and treat complications.

Preserved efficiency of sickle cell disease placentas despite altered morphology and function

INTRODUCTION

Pregnant women with sickle cell disease (SCD) are at high risk for sickle cell-related complications, obstetrical complications, and perinatal morbidity. Chronic inflammation and the proangiogenic environment associated with SCD have been associated with endothelial damage. It is unknown whether SCD complications could be associated with placental dysfunction or abnormal placental morphology. Moreover, circulating angiogenic factors in pregnant women with SCD are unexplored.

METHODS

Clinical records, placental and blood samples were collected at term delivery for 21 pregnant patients with SCD and 19 HbAA pregnant controls with adapted to gestational age birth weight newborns. Histological and stereological analyses and scanning electron microscopy (SEM) of the placenta, and PlGF and sFlt1 measurements in blood were performed.

RESULTS

In the SCD group, the parenchyma-forming villi of placentas were thinner than in controls, and increased fibrinoid necrosis and an overabundance of syncytial knots were seen. SEM revealed elongated intermediate villous endings with a reduction in the number of terminal villi compared to controls, indicating a significant branching defect in SCD placentas. Finally, SCD patients had an imbalance in the angiogenic ratio of sFlt1/PlGF (p = 0.008) with a drop of PlGF concentrations.

DISCUSSION

We evidence for the first time both abnormal placenta morphology and altered sFlt1/PlGF ratio in SCD patients, uncorrelated with maintained placental efficiency and fetal growth.

Placental transcriptome profile of women with sickle cell disease reveals differentially expressed genes involved in migration, trophoblast differentiation and inflammation

Sickle cell disease (SCD) is a group of disorders whose common characteristic is the presence of hemoglobin (Hb) S in erythrocytes. The main consequence of this abnormality is vaso-occlusion, which can affect almost all organs including the placenta. This study aimed to evaluate the gene expression profile in placentas of women with SCD by means of total RNA sequencing. For this, we proposed a case-control study, with three groups of pregnant women: HbSS (n = 10), HbSC (n = 14) and HbAA (n = 21). The results showed differences in expression in a number of genes such as NOS2 (fold change, FC = 4.52), HLAG (FC = 5.56), ASCL2 (FC = 3.61), CXCL10 (FC = -3.66) and IL1R2 (FC = 3.92) for the HbSC group and S100A8 (FC = -3.82), CPXM2 (FC = 4.57), CXCL10 (FC = -4.59), CXCL11 (FC = -3.72) and CAMP (FC = -4.55) for the HbSS group. Differentially expressed genes are mainly associated with migration, trophoblast differentiation and inflammation. The causes leading to altered gene expression in placentas of sickle cell patients are not fully understood, but the presence of intravascular hemolysis and vaso-occlusion, with cycles of ischemia and reperfusion, may contribute to the emergence of an environment which can be very harmful for placental physiology, altering the nutrient supply and metabolic exchange for fetal growth.

Interleukin-6 in pregnancy with sickle cell disease

BACKGROUND

Despite advances in health care for sickle cell disease patients, as well as in the improvement in reproductive issues mainly in women with the disease, pregnancy is still a challenge, both for the mother and the child, with high rates of maternal and fetal morbidity and mortality. Besides their chronic hemolytic status and vaso-occlusive events that confer systemic complications, pregnant women also have higher rates of pain episodes, infections, abortion, intrauterine growth retardation, pre-term births, eclampsia, stillbirth and the hemolysis, elevated liver enzymes and low platelets syndrome. The physiologic mechanisms of the disease in pregnancy are still unknown and chronic inflammatory responses may interfere in the adverse outcomes. The cytokine and chemokine profiles in pregnancy with sickle cell disease remain unknown. The aim of this study was to evaluate the cytokine profile of the inflammatory response of pregnant women with sickle cell disease.

METHOD

Blood samples from 20 pregnant women with sickle cell disease, 24 women with sickle cell disease in steady state, 16 healthy pregnant women and a control group with 9 women at childbearing age were assayed for interleukin-6.

MAIN RESULTS

Pregnant women with sickle cell disease presented high serum levels of interleukin-6, compared to healthy pregnant women (p=0.0115).

CONCLUSION

These data suggest that the increased production of interleukin-6 may occur during pregnancy with sickle cell disease and that the role of this cytokine in the sickle cell disease pathophysiology and pregnancy complications should be further studied.

Different morphological and gene expression profile in placentas of the same sickle cell anemia patient in pregnancies of opposite outcomes

IMPACT STATEMENT

Environmentally induced changes in placental morphological and molecular phenotypes may provide relevant insight towards pathophysiology of diseases. The rare opportunity to evaluate the same patient, with sickle cell anemia (SCA), in two different pregnancies, of opposite outcomes (one early onset severe preeclampsia (PE) and the other mostly non-complicated) can prove such concept. In addition, the comparison to other conditions of known placental and vascular/inflammatory involvement strengthens such findings. Our results suggest that the clinical association between SCA and PE can be supported by common pathophysiological mechanisms, but that pathways involving response to copper and triglyceride metabolism may be important drivers of the pathophysiology of PE. Future studies using in a larger number of samples should confirm these findings and explore pathways involved in the pathophysiology of PE and its relationship with SCA.

Differences in prenatal aneuploidy screening among African-American women with hemoglobin S variants

OBJECTIVE

It has been shown that hemoglobinopathies increase the risk of pregnancy complications and placental dysfunction. This could alter the placental analytes examined during prenatal aneuploidy screening. Our objective was to determine whether there is a difference in maternal serum screening results for women with hemoglobin S variants (AS, SS, SC, S/beta thalassemia) compared with women with normal hemoglobin (AA).

STUDY DESIGN

This is a retrospective cohort study in African-American women receiving aneuploidy screening at MedStar Washington Hospital Center from 2008 to 2015. We evaluated 79 women with hemoglobin S variants (69 AS and 10 sickle cell disease (SCD)) and 79 controls. Descriptive statistics (means, medians, and frequencies) were calculated for each group. For the continuous variables, differences in the averages between the two groups were tested using the t test or Wilcoxon rank sum test. Differences in the averages between three or more groups were tested using the analysis of variance test or the Kruskal-Wallis test.

RESULTS

Demographics were similar between cases and controls. The overall screen positive rate for Down syndrome among patients with sickle cell trait (AS) was 3% (2/69). For patients with SCD, the overall screen positive rate was 10% (1/10). None of the women in the control population (AA) has a positive Down syndrome screening result (0/79).

CONCLUSION

As expected, the screen positive rate in patients with hemoglobin S variants was higher than controls, however, patients with sickle cell trait do not appear to be at an increased risk for false-positive results with serum aneuploidy screening compared with the general population. We did, however, find an increased risk of false-positive quad screen results in patients with sickle cell disease.

Abnormal expression of inflammatory genes in placentas of women with sickle cell anemia and sickle hemoglobin C disease

Sickle cell disease (SCD) is a complex disease that is characterized by the polymerization of deoxyhemoglobin S, altered red blood cell membrane biology, endothelial activation, hemolysis, a procoagulant state, acute and chronic inflammation, and vaso-occlusion. Among the physiological changes that occur during pregnancy, oxygen is consumed by fetal growth, and pregnant women with SCD are more frequently exposed to low oxygen levels. This might lead to red blood cells sickling, and, consequently, to vaso-occlusion. The mechanisms by which SCD affects placental physiology are largely unknown, and chronic inflammation might be involved in this process. This study aimed to evaluate the gene expression profile of inflammatory response mediators in the placentas of pregnant women with sickle cell cell anemia (HbSS) and hemoglobinopathy SC (HbSC). Our results show differences in a number of these genes. For the HbSS group, when compared to the control group, the following genes showed differential expression: IL1RAP (2.76-fold), BCL6 (4.49-fold), CXCL10 (-2.12-fold), CXCR1 (-3.66-fold), and C3 (-2.0-fold). On the other hand, the HbSC group presented differential expressions of the following genes, when compared to the control group: IL1RAP (4.33-fold), CXCL1 (3.05-fold), BCL6 (4.13-fold), CXCL10 (-3.32-fold), C3 (-2.0-fold), and TLR3 (2.38-fold). Taken together, these data strongly suggest a differential expression of several inflammatory genes in both SCD (HbSS and HbSC), indicating that the placenta might become an environment with hypoxia, and increased inflammation, which could lead to improper placental development.

Role of DNA methyltransferase 1 on the altered eNOS expression in human umbilical endothelium from intrauterine growth restricted fetuses

Reduced fetal growth associates with endothelial dysfunction and cardiovascular risk in both young and adult offspring and the nitric oxide (NO) system has been implicated in these effects. Epigenetic processes are likely to underlie such effects, but there is to date no evidence that endothelial dysfunction in early life results from epigenetic processes on key genes in the NO system, such as NOS3 (eNOS) and ARG2 (arginase-2). We determined basal DNA methylation status in NOS3 and ARG2 promoters, and DNA methyltransferase 1 (DNMT1) effect on eNOS and arginase-2 expression using human endothelial cells isolated from umbilical arteries (HUAEC) and veins (HUVEC) from control and intrauterine growth restricted (IUGR) fetuses. Compared with cells from control pregnancies, eNOS protein and mRNA levels were increased in HUAEC, but decreased in HUVEC, from IUGR, while arginase-2 levels were increased in IUGR-HUVEC. The NOS3 promoter showed a decrease in DNA methylation at CpG -352 in IUGR-HUAEC, and an increase in IUGR-HUVEC, when compared with control cells. Methylation in the hypoxia response element of the NOS3 promoter was increased in IUGR-HUAEC and decreased in HUVEC. Methylation in the AGR2 promoter in IUGR-HUVEC was decreased in a putative HRE, and without changes in IUGR-HUAEC. Silencing of DNMT1 expression normalized eNOS expression in IUGR endothelial cells, and restored the normal response to hypoxia in HUVEC, without effects on arginase-2. This data suggest that eNOS expression in IUGR-derived endothelial cells is programmed by altered DNA methylation, and can be reversed by transient silencing of the DNA methylation machinery.

Expression of the growth factor progranulin in endothelial cells influences growth and development of blood vessels: a novel mouse model

Progranulin is a secreted glycoprotein that regulates cell proliferation, migration and survival. It has roles in development, tumorigenesis, wound healing, neurodegeneration and inflammation. Endothelia in tumors, wounds and placenta express elevated levels of progranulin. In culture, progranulin activates endothelial proliferation and migration. This suggested that progranulin might regulate angiogenesis. It was, however, unclear how elevated endothelial progranulin levels influence vascular growth in vivo. To address this issue, we generated mice with progranulin expression targeted specifically to developing endothelial cells using a Tie2-promoter/enhancer construct. Three Tie2-Grn mouse lines were generated with varying Tie2-Grn copy number, and were called GrnLo, GrnMid, and GrnHi. All three lines showed increased mortality that correlates with Tie2-Grn copy number, with greatest mortality and lowest germline transmission in the GrnHi line. Death of the transgenic animals occurred around birth, and continued for three days after birth. Those that survived beyond day 3 survived into adulthood. Transgenic neonates that died showed vascular abnormalities of varying severity. Some exhibited bleeding into body cavities such as the pericardial space. Smaller localized hemorrhages were seen in many organs. Blood vessels were often dilated and thin-walled. To establish the development of these abnormalities, we examined mice at early (E10.5-14.5) and later (E15.5-17.5) developmental phases. Early events during vasculogenesis appear unaffected by Tie2-Grn as apparently normal primary vasculature had been established at E10.5. The earliest onset of vascular abnormality was at E15.5, with focal cerebral hemorrhage and enlarged vessels in various organs. Aberrant Tie2-Grn positive vessels showed thinning of the basement membrane and reduced investiture with mural cells. We conclude that progranulin promotes exaggerated vessel growth in vivo, with subsequent effects in the formation of the mural cell layer and weakening of vessel integrity. These results demonstrate that overexpression of progranulin in endothelial cells influences normal angiogenesis in vivo.

Endothelial eNOS/arginase imbalance contributes to vascular dysfunction in IUGR umbilical and placental vessels

Placental vascular tone is critically influenced by nitric oxide (NO) derived from endothelial NO synthase (eNOS) activity. Placental vessels from pregnancies complicated with intrauterine growth restriction present altered NOS-dependent vasodilation. Arginase-2 competes with eNOS for l-arginine and counteracts the NOS-dependent relaxation in umbilical vessels from normal pregnancies. However there is no data regarding the contribution of arginase activity on the impaired endothelial function in IUGR placenta. We studied whether arginase-2 participates in IUGR-related placental vascular dysfunction counteracting eNOS-dependent relaxation, and the regulation of arginase-2 and eNOS expression in endothelial cells from IUGR umbilical arteries (HUAEC) and veins (HUVEC). In IUGR-derived umbilical arteries (UA) and veins (UV), and chorionic arteries (CA), NOS-dependent vasoactive response in the presence and absence of BEC (arginase inhibitor) was studied. Protein levels of eNOS (total and Ser(1177)-P-eNOS), arginase-2 and arginase activity were determined in IUGR HUAEC and HUVEC. In IUGR vessels eNOS-dependent relaxation was reduced, being improved by BEC. This effect was higher in arteries than veins, and in chorionic compared with umbilical vessels. In cultured IUGR endothelial cells, arginase-2 protein expression and activity were increased in HUVEC, without changes in HUAEC. In IUGR-derived endothelium there was a generalized reduction in the in vitro eNOS activation (Ser(1177)-P-eNOS/eNOS), and therefore a decreased eNOS/arginase activity ratio. Here we provide ex vivo and in vitro evidence for a vascular role of arginase throughout placental vasculature, negatively controlling NOS activity. This effect seems to be crucial in the pathophysiology of endothelial dysfunction present in IUGR feto-placental vessels.

Oxidative damage to pre-eclamptic placenta: immunohistochemical expression of VEGF, nitrotyrosine residues and von Willebrand factor

OBJECTIVE

To determine the relationship of biomarkers of placental damage by oxidative stress in pre-eclamptic placenta.

METHODS

A case-control study was performed on a population of 14 pregnant women with PE and 12 women with normal pregnancies. Immunohistochemical expressions of VEGF, vWF distribution, (Na + K)-ATPase activity, and abundance of nitrotyrosine residues, were assessed in the placental tissue.

RESULTS

Women with pre-eclampsia showed increased VEGF expression and abundance of nitrotyrosine residues in placental villous, and plasma vWF levels (p < 0.05), whereas placental (Na + K)-ATPase activity were significantly reduced. The syncytiotrophoblast and the maternal space of pre-eclamptic placenta showed diminished and increased vWF expression, respectively, but no significant differences in its expression were found in the placental endothelium and stroma (p < 0.05).

CONCLUSIONS

It could be suggested that increased oxidative stress and VEGF contribute to enhance the impairment of placental perfusion by increasing peroxynitrite formation, product of the NO and superoxide reaction, thereby partly contributing to account for the pathophysiology of this disease. The presence of vWF in the maternal space and its diminished expression in syncytiotrophoblast of pre-eclamptic placenta also might have pathogenic implications.

Role of arginase-2 and eNOS in the differential vascular reactivity and hypoxia-induced endothelial response in umbilical arteries and veins

The main vasodilator in the placenta is nitric oxide (NO), which is synthesized by endothelial NO synthase (eNOS). Arginase-2 competes with eNOS for l-arginine, and its activity has been related with vascular dysfunction. Recently, we showed that hypoxia induces arginase-2, and decreases eNOS activity in human umbilical vein endothelial cells (HUVEC). However there is evidence that vascular responses to hypoxia are not similar throughout the placental vascular tree. We studied whether arginase-2 plays a role controlling vascular tone in human umbilical vessels, and the changes in the expression of arginase-2 and eNOS proteins by hypoxia in endothelial cells from umbilical arteries (HUAEC) and veins (HUVEC). In isolated umbilical vessels the presence of eNOS and arginase-2 was determined in the endothelium, and the NO-dependent vasoactive responses in the presence and absence of S-(2-boronoethyl)-L-cysteine (BEC, arginase inhibitor) were studied. Additionally, HUAEC and HUVEC were exposed (0-24 h) to hypoxia (2% O2) or normoxia (5% O2), and protein levels of eNOS (total and phosphorylated at serine-1177) and arginase-2 were determined. In umbilical arteries and veins arginase-2 and eNOS were detected mainly at the endothelium. BEC induced a higher concentration-dependent relaxation in umbilical arteries than veins, and these responses were NOS-dependent. In HUAEC exposed to hypoxia there were no changes in eNOS and arginase-2 levels, however there was a significant increase of p-eNOS. In contrast, HUVEC showed an increase in arginase-2 and a reduction of p-eNOS in response to hypoxia. These results show that arginases have a vascular role in placental vessels counteracting the NOS-dependent relaxation, which is differentially regulated in placental artery and vein endothelial cells.

Immunohistochemical expression of von Willebrand factor in the preeclamptic placenta

Preeclampsia is a high-prevalence systemic pregnancy disorder associated with maternal and foetal mortality. Its pathogenesis is unknown, but it is thought that oxidative stress and endothelial dysfunction may play a fundamental role. Von Willebrand factor (vWF), a marker of endothelial cell injury, can be found in different cells and zones of the placenta. To determine the differential immunoexpression of vWF at different tissue types of preeclamptic placenta and endothelial dysfunction markers at maternal serum of preeclamptic pregnancies. A case-control study was performed on a population of pregnant women with preeclampsia (n = 14), and normal pregnancies (n = 8). Placental and blood plasma samples were withdrawn at delivery. Immunohistochemical vWF expression in the placental tissue was determined. Endothelial dysfunction was assessed through plasminogen activator inhibitor (PAI) 1 and 2 ratio and vWF concentration in maternal plasma. P values less than 0.05 were considered statistically significant. Preeclamptic women showed increased plasma PAI-1/PAI-2 ratio (P < 0.05). There was diminished placental vWF expression in syncytiotrophoblast and increased in the intervillous space of preeclamptic placentas (P < 0.05). No significant differences in vWF expression were found in the villous endothelium and stroma, but it was significantly higher in maternal plasma (P < 0.05). In preeclampsia occurs endothelial damage and placental cell injury. Cell damage in syncytiotrophoblast that occurs in preeclampsia could liberate vWF from syncytiotrophoblast to the placental intervillous space, and this may have pathogenic implications.

The mechanisms of low birth weight in infants of mothers with homozygous sickle cell disease

OBJECTIVE

A low mean birth weight is a constant finding in pregnancies of women with homozygous sickle cell disease. The factors responsible are largely unknown and have now been investigated in an 11-year retrospective analysis.

METHODS

Records for 126 pregnancies of mothers with homozygous sickle cell disease and 126 pregnancies of control women with an AA phenotype, matched according to age and date of delivery, were examined. Events during pregnancy and outcomes of pregnancy were recorded.

RESULTS

Pregnancy outcomes for mothers with homozygous sickle cell disease confirmed the lower birth weight, gestational age, and placental weight. A low birth weight in infants of mothers with homozygous sickle cell disease was strongly related to gestational age and placental weight and weakly related to reticulocyte counts and a history of preeclampsia in univariate analyses, but only gestational age and placental weight remained significant in multivariate analyses. No relationships were seen with maternal age, parity, anthropometric features, other hematologic features (hemoglobin levels, fetal hemoglobin levels, mean cell volume, and alpha-thalassemia), pregnancy-induced hypertension, or prepartum hospital admissions (expressed as number or total days). Compared with Jamaican standards, birth weight was affected more than head circumference or length in infants of mothers with homozygous sickle cell disease, indicating asymmetric growth retardation, which occurred for 27% of boys and 38% of girls (compared with 4% and 9%, respectively, among infants of control mothers).

CONCLUSIONS

A chronic condition such as homozygous sickle cell disease might have been expected to cause symmetric growth retardation throughout pregnancy. The finding of asymmetric retardation might indicate adverse factors emerging late in pregnancy and might have relevance for the poor pregnancy outcomes in such mothers.

Pregnancy and Sickle Cell Disease

With advances in management, men and women with sickle cell disease are enjoying an improved quality of life well into adulthood, when they may elect to plan a family. Pregnancy has been associated with exacerbation of sickle cell disease and may place women, especially those with sickle cell anemia (HbSS), at an additional risk for obstetric complications. Appropriate management by health care providers familiar with sickle cell diseases and high-risk obstetric care can result in a successful pregnancy for most women with sickle cell disease.