Downregulation of apelin in the human placental chorionic villi from preeclamptic pregnancies

The role of the endogenous apelin system in pregnancy is not well understood. Apelin's actions in pregnancy are further complicated by the expression of multiple forms of the peptide. Using radioimmunoassay (RIA) alone, we established the expression of apelin content in the chorionic villi of preeclamptic (PRE) and normal pregnant women (NORM) at 36-38 wk of gestation. Total apelin content was lower in PRE compared with NORM chorionic villi (49.7±3.4 vs. 72.3±9.8 fmol/mg protein; n=20-22) and was associated with a trend for lower preproapelin mRNA in the PRE. Further characterization of apelin isoforms by HPLC-RIA was conducted in pooled samples from each group. The expression patterns of apelin peptides in NORM and PRE villi revealed little or no apelin-36 or apelin-17. Pyroglutamate apelin-13 [(Pyr1)-apelin-13] was the predominant form of the peptide in NORM and PRE villi. Angiotensin-converting enzyme 2 (ACE2) activity was higher in PRE villi (572.0±23.0 vs. 485.3±24.8 pmol·mg(-1)·min(-1); n=18-22). A low dose of ANG II (1 nM; 2 h) decreased apelin release in NORM villous explants that was blocked by the ANG II receptor 1 (AT1) antagonist losartan. Moreover, losartan enhanced apelin release above the 2-h baseline levels in both NORM and PRE villi (P<0.05). In summary, these studies are the first to demonstrate the lower apelin content in human placental chorionic villi of PRE subjects using quantitative RIA. (Pyr1)-apelin-13 is the predominant form of endogenous apelin in the chorionic villi of NORM and PRE. The potential mechanism of lower apelin expression in the PRE villi may involve a negative regulation of apelin by ANG II.

Hemodynamic responses to angiotensin-(1-7) in women in their third trimester of pregnancy

BACKGROUND

To understand the role of Angiotensin-(1-7) (Ang-(1-7)) in vasculature of pregnant women, we compared cardiac output (CO), total peripheral resistance (TPR) and forearm blood flow (FBF) responses to Ang-(1-7) infusion between normotensive pregnant women in their third trimester and healthy age matched non-pregnant women. The responses of skin microcirculation to Ang-(1-7) were tested in preeclamptic, normotensive pregnant and non-pregnant women. Responses to Angiotensin II (Ang II) were also determined.

METHODS

Non-invasive methods for systemic (bioimpedance and VascuMAP), FBF (venous occlusion strain gauge plethysmography), and skin (laser Doppler) hemodynamics assessments were used.

RESULTS

Compared to non-pregnant women, systemic infusion of Ang-(1-7) (2000 pmol/min) resulted in a greater increase in CO (9.4 ± 6.4 versus -3.3 ± 2.1%, n = 9-10) in normotensive pregnant women. Brachial local infusion of Ang-(1-7) had no effect on FBF in either group. In non-pregnant and normotensive pregnant women, local Ang II induced a dose-dependent decrease in FBF and increase in forearm resistance at 50 and 100 pmol/min (p < 0.05 versus corresponding baseline, n = 7-10). Following iontophoretic application of 5 mmol/l dose of Ang-(1-7), the change in skin flow was higher in normotensive pregnant versus preeclamptic women (182.5 ± 93 versus 15.76 ± 19.46%, n = 14-15). Skin flow was lower in normotensive pregnant versus preeclamptic women (-46.5 ± 48.7 versus 108.7 ± 49.1%, n = 14-15) following Ang II infusion at 1.0 pmol/min.

CONCLUSION

In the third trimester of pregnancy, Ang-(1-7) induces alterations in CO and differentially regulates micro- and macro-circulations, depending on the dose. Dysregulation in skin vasculature may contribute to the development of vascular dysfunction and hypertension in preeclampsia.

Abstract 634: Apelin as a Novel Therapeutic Target in Preeclampsia

Preeclampsia is a major cause for perinatal fetal and maternal morbidities and mortalities. The endogenous apelin system is an emerging target for the regulation of cardiovascular homeostasis; however, its role in pregnancy is not well understood. Apelin and its receptor are expressed in placental trophoblasts and fetal endothelial cells. We have reported that total immunoreactive apelin was lower in the placenta of preeclamptic women (PRE) compared to normotensive women (NT). The processing of the apelin precursor is complex and may yield a number of bioactive forms of the peptide. Presently, it is not known whether differences exist in the expression of the various molecular forms of apelin in the human placenta and whether the distribution pattern of apelin is altered in PRE. To address this issue, placental samples were pooled from NT (n=4) or PRE (n=4) at 37-38 weeks of gestation and the apelin forms resolved by HPLC coupled to an apelin radioimmunoassay (RIA). Total apelin content was lower in the placenta of PRE compared to NT (4.2 vs. 6.1 pg/mg wet weight). The HPLC analysis revealed negligible levels of apelin-36 from the placentas of NT (0.09 pg/mg wet weight) and PRE (0.11 pg/mg wet weight). A peak of apelin-17 was detected in both NT and PRE samples, but the shorter forms of apelin were more abundant. Therefore, separation conditions were tailored to achieve greater resolution of the lower molecular weight forms of apelin. This analysis revealed that the predominant apelin in both PRE and NT placentas was pyroglutamylated apelin-13 (Pyr-apelin-13; NT: 7.1 and PRE: 6.6 pg/mg wet weight); however, apelin-12 and apelin-13 were lower in PRE vs. NT placentas (1.8 and 22 fold, respectively). Lower expression of apelin-13 may reflect an inability to effectively influence blood pressure in PRE. Indeed, we further show that systemic infusion of apelin-13 (2 mg/kg/day) from day 13 to 20 of gestation reduced mean blood pressure (144±1 vs. 163±5 mmHg, n=4-6, p<0.01) in preeclamptic transgenic rats. In conclusion, we demonstrate that Pyr-apelin-13 is the predominant endogenous isoform of apelin in both NT and PRE placentas, while apelin-13 and apelin-12 are downregulated in PRE placentas. As a novel therapeutic agent, apelin may prevent the development of preeclampsia.

Abstract 549: Angiotensin II Attenuates Apelin-36 Release from Human Placental Chorionic Villi

Angiotensin II (Ang II) and apelin have opposing actions in the regulation of blood pressure, vascular tone and angiogenesis, factors known to be important in pregnancy. Chorionic villi (CV) are essential for the transport of oxygen and metabolites in the maternal-fetal interface. Previous studies from our group demonstrated the upregulation of Ang II in the CV of preeclamptic women. Since the interaction between Ang II and apelin have been suggested in the cardiovascular system, we determined whether Ang II alters the release of apelin from the placental CV obtained from normotensive pregnant (NP) and preeclamptic (PRE) women. We also established whether Ang-(1-7) influences apelin release from the same set of tissue samples. CV were dissected from the placental tissue, washed and incubated for 0, 2 and 16 hours in DMEM/F12 media with or without Ang II (1 nM and 1 μM) or Ang-(1-7) (1 nM and 1 μM) under controlled O2 and CO2 tensions. The unstimulated release of apelin measured by a competitive radioimmunoassay was significantly reduced in the conditioned media from PRE compared to NP chorionic villi at 2 hrs (PRE: 181.1 ± 31 vs. NP: 309.5 ± 51.4 pg/ml, p<0.05). There was a significant increase in apelin release from both NP (267.8 ± 34.8 vs. baseline: 118.4 ± 27.3 pg/ml, p<0.01) and PRE (293.5 ± 25.8 vs. baseline: 122.6 ± 24.8 pg/ml, p<0.01) CV at 16 hours. Ang II or Ang-(1-7) inhibited the release of apelin from CV of the NP (p<0.05) but not of PRE at 2 hours. At 16 hours, however, Ang II or Ang-(1-7) inhibited the release of apelin from both NP and PRE villi (p<0.05). Immunostaining revealed the predominant localization of apelin receptor to syncytiotrophoblasts and fetal vascular cells of CV - areas associated with AT1 receptor localization. Our data showing a negative influence of Ang II on apelin release from chorionic villi suggest an opposing interaction between these peptides in the human placental tissue. Reduced apelin activity would remove its counter-regulatory actions on Ang II-induced endothelial dysfunction, increased vascular resistance, and inflammation - abnormalities which precede and sustain preeclampsia. A surprising inhibitory effect of Ang-(1-7) on apelin suggests a complex regulation of apelin within the RAS.

Placental endothelial nitric oxide synthase in multiple and single dose betamethasone exposed pregnancies

OBJECTIVE

To compare endothelial nitric oxide synthase expression and capillary density (CDS) in placentas exposed to single or multiple courses of betamethasone.

STUDY DESIGN

Placental specimens exposed to single vs repeat courses of betamethasone were analyzed through immunohistochemistry and digital image quantification for endothelial nitric oxide synthase and CD34. Quantified endothelial nitric oxide synthase staining, calculated capillary density, ratio of endothelial nitric oxide synthase to capillary density, and clinical characteristics were compared. Linear regression was performed with these as dependent variables.

RESULTS

Mean and maximum capillary density were increased (P = .013 and .005) and the ratio of endothelial nitric oxide synthase to capillary density decreased (P = .016) in specimens exposed to 4 courses of betamethasone compared with 1 to 3 courses. Exposure to 4 courses of betamethasone was associated with increased capillary density, but not with endothelial nitric oxide synthase expression.

CONCLUSION

Exposure to 4 courses of betamethasone is associated with increased placental capillary density. The placental effects of multiple courses of betamethasone are unrelated to endothelial nitric oxide synthase expression.

Robotic-assisted laparoscopic repair of symptomatic cesarean scar defect: a report of two cases

BACKGROUND

Symptomatic cesarean scar defect is one of the commonly reported long-term complications of cesarean section.

CASES

We present two cases of symptomatic cesarean scar defect treated conservatively by robotic-assisted laparoscopy at our institution. Both patients presented with hematocele, pelvic discomfort and secondary infertility. Transvaginal ultrasound revealed hematocele measuring 3.7 x 1.9 x 3.8 cm and 3.0 x 2.0 x 1.6 cm in the lower uterine segments, respectively. After surgery normal menses resumed in both patients, and their childbearing potential was preserved. The patients conceived 3 and 11 months after surgery, respectively.

CONCLUSION

Recognition of cesarean scar defect is important in the explanation of certain menstrual disorders since surgical intervention can result in improvement of symptoms and prevent the related secondary obstetric and gynecologic complications. Robotic-assisted laparoscopic approach is a good minimally invasive alternative for the repair of cesarean scar defect.

Identifying risk factors for uterine rupture

Uterine rupture, whether in the setting of a prior uterine incision or in an unscarred uterus, is an obstetric emergency with potentially catastrophic consequences for both mother and child. Numerous studies have been published regarding various risk factors associated with uterine rupture. Despite the mounting data regarding both antepartum and intrapartum factors, it currently is impossible to predict in whom a uterine rupture will occur. This article reviews the data regarding these antepartum and intrapartum predictors for uterine rupture. The author hopes that the information presented in this article will help clinicians assess an individual's risk for uterine rupture.

Intrapartum predictors of uterine rupture

This case-controlled study reviewed 26 cases of uterine rupture at an academic medical center. Controls were selected in a 2:1 design by reviewing the immediate successful vaginal birth after cesarean delivery (VBAC) before and after each case of uterine rupture. At less than 2 hours before delivery or acute uterine rupture, mild and severe variable decelerations, persistent abdominal pain, and hyperstimulation were more common in cases of uterine rupture as compared to controls and had statistically significant positive likelihood ratios (LR). Mild and severe variable fetal heart rate decelerations, especially in the presence of persistent abdominal pain, may predict uterine rupture in patients attempting VBAC.

Inhibition of cyclooxygenase-2: effects on renin secretion and expression in fetal lambs

The importance of prostaglandins in the regulation of the renin-angiotensin system during development is not known. These experiments were conducted to examine the effects of prostaglandin synthesis inhibitors on basal and isoproterenol-induced plasma renin concentration and renin gene expression in the late-gestation fetal lamb. Eighteen lamb fetuses ranging in gestational age from 129 to 138 days underwent surgical insertion of femoral arterial and venous catheters under general endotracheal anesthesia. After a period of recovery, animals underwent an infusion of isoproterenol after administration of a saline bolus (control experiments); 24-48 h later a second study was performed after administration of NS-398, a cyclooxygenase (COX)-2 inhibitor, or saline for a second control study. Administration of COX-2 inhibitor significantly reduced baseline plasma renin levels and attenuated responses in fetal renin secretion to isoproterenol infusions. Renal cortical cells from animals receiving COX-2 inhibitor had significantly lower levels of renin mRNA compared with animals receiving only saline. Renal cortical cells in culture from animals receiving only saline exhibited increased levels of renin mRNA when treated with isoproterenol, forskolin, or IBMX. Only forskolin increased renin mRNA levels in renal cortical cells in culture from animals receiving COX-2 inhibitor. We conclude that prostaglandins play a stimulatory role in the regulation of the renin-angiotensin system and are necessary for beta-adrenergic stimulation of renin secretion and gene expression in the late-gestation fetal lamb.

Antibiotics and preterm labor

Prematurity is a profound obstetric problem and to date no effective treatment or prevention strategies have been found. Many animal and clinical data exist to link infection and preterm labor, yet clinical trials examining the effect of antibiotic treatment in patients with patterns labor and intact membranes have been conflicting and disappointing. Beyond treatment to reduce neonatal group B streptococcal infection, sexually transmitted infections, symptomatic bacterial vaginosis, and bacteriuria, no clinical data exist at this time to support the routine use of antibiotics in patients with preterm labor and intact membranes.

Early diagnosis of ectopic pregnancy. Does use of a strict algorithm decrease the incidence of tubal rupture?

OBJECTIVE

To determine if tubal rupture rates are decreased when a strict diagnostic algorithm is employed in the evaluation of women with suspected ectopic pregnancy as compared to individualized diagnostic methods.

STUDY DESIGN

Between 1994 and 1996, a group of investigators at Charleston Area Medical Center employed a strict diagnostic algorithm consisting of serum quantitative human chorionic gonadotropin (hCG) levels, progesterone levels, ultrasound and endometrial curettage in order to expedite diagnosis when ectopic pregnancy was suspected (group A patients). Other practitioners employed traditional criteria in similar clinical situations (group B patients). Medical records of patients diagnosed with ectopic pregnancy in this period were retrospectively reviewed. Demographic data, clinical and laboratory characteristics, and rate of tubal rupture were compared.

RESULTS

Sixty-one of 122 patients were diagnosed with ectopic pregnancy by strict criteria. These patients did not differ significantly from those evaluated by an individualized approach in regard to age, gravidity, parity or risk factors for ectopic pregnancy. Menstrual age, hCG levels and progesterone levels were similar as well. Group A patients had a median diagnostic interval of 2 days, with a range of 0-16. Group B patients had a median diagnostic interval of 8 days, with a range of 0-44 (P < .001). Of patients evaluated by this strict algorithm, 3.3% experienced rupture as compared to 23% of patients in group B (P < .001).

CONCLUSION

Use of a strict diagnostic algorithm in the evaluation of patients with suspected ectopic pregnancy resulted in decreased tubal rupture rates. Such an algorithm could be disseminated to all locations for triage of patients and use in a standardized manner. This practice could result in a reduction in loss of reproductive function and mortality secondary to ectopic pregnancy.