Generation of Human Regulatory Dendritic Cells from Cryopreserved Healthy Donor Cells and Hematopoietic Stem Cell Transplant Recipients

Acute graft versus host disease (GVHD) remains a significant complication following hematopoietic stem cell transplant (HSCT), despite improved human leukocyte antigen (HLA) matching and advances in prophylactic treatment regimens. Previous studies have shown promising results for future regulatory dendritic cell (DCreg) therapies in the amelioration of GVHD. This study evaluates the effects of cryopreservation on the generation of DCreg, the generation of young and older DCreg in serum-free media, and the feasibility of generating DCreg from young and older HSCT patient monocytes. DCregs were generated in X-vivo 15 serum-free media from donor or patient monocytes. This study includes the use of monocytes from young and older healthy, donor, and HSCT patients with varying hematological diseases. Phenotypic differences in cell populations were assessed via flow cytometry while pro-inflammatory and anti-inflammatory cytokine production was evaluated in culture medium. The number of DCreg generated from cryopreserved monocytes of healthy donors was not significantly different from freshly isolated monocytes. DCreg generated from cryopreserved monocytes had comparable levels of co-stimulatory molecule expression, inhibitory molecule expression, and cytokine production as freshly isolated monocytes. Young and older healthy donor monocytes generated similar numbers of DCreg with similar cytokine production and phenotype. Although monocytes from older HSCT patients generated significantly fewer DCreg, DCreg from young and older HSCT patients had comparable phenotypes and cytokine production. Monocytes from young and older myelodysplastic syndrome (MDS) patients generated reduced numbers of DCreg compared to non-MDS-derived DCreg. We demonstrate that the cryopreservation of monocytes from HSCT patients of varying hematological diseases allows for the cost-effective generation of DCreg on an as-needed basis. Although the generation of DCreg from MDS patients requires further assessment, these data support the possibility of in vitro-generated DCreg as a therapy to reduce GVHD-associated morbidity and mortality in young and older HSCT recipients.

Cellular Immunotherapy in Mice Prevents Maternal Hypertension and Restores Anti-Inflammatory Cytokine Balance in Maternal and Fetal Tissues

Preeclampsia is the leading cause of maternal-fetal morbidity worldwide. The concept that persistent feto-placental intolerance is important in the pathogenesis of preeclampsia (PreE) has been demonstrated by our lab and others. Arginine vasopressin (AVP) infusion during pregnancy induces cardiovascular, renal, and T helper (TH) cell alterations in mice consistent with human PreE. In addition to their conventional immuno-stimulatory role, dendritic cells (DCs) also play a vital role in immune tolerance. In contrast to conventional DCs, regulatory DCs (DCregs) express low levels of co-stimulatory markers, produce anti-inflammatory cytokines, induce T regulatory (Treg) cells, and promote tolerance. In mice, DCregs prevent pro-inflammatory responses and induce antigen-specific tolerance. Given these known functions of DCregs, we hypothesize that DCregs will prevent the development of AVP-induced PreE in mice. C57BL/6J females were infused with AVP (24 ng/h) or saline throughout gestation via an osmotic minipump. Bone-marrow-derived DCregs were injected into AVP-infused dams at the time of the pump implantation or on gestational day (GD) 7. The blood pressure of the mice was taken throughout their pregnancy. The maternal urine proteins and TH-associated cytokines in maternal and fetal tissues were measured on GD 18. The treatment with DCregs effectively prevented the elevation of maternal blood pressure, proteinuria, and fetal growth restriction that were observed in AVP-infused dams. Furthermore, we noted a reduction in the pro-inflammatory TH-associated cytokines IFNγ and IL-17, while anti-inflammatory cytokines IL-4, IL-10, and TGFβ showed an increase following DCreg treatment. These outcomes provide strong evidence supporting the potential of DCregs as a valuable therapeutic approach in addressing PreE.

Efferocytosis of viable versus heat-inactivated MSC induces human monocytes to distinct immunosuppressive phenotypes

BACKGROUND

Immunomodulation by mesenchymal stromal cells (MSCs) can occur through trophic factor mechanisms, however, intravenously infused MSCs are rapidly cleared from the body yet a potent immunotherapeutic response is still observed. Recent work suggests that monocytes contribute to the clearance of MSCs via efferocytosis, the body's natural mechanism for clearing dead and dying cells in a non-inflammatory manner. This begs the questions of how variations in MSC quality affect monocyte phenotype and if viable MSCs are even needed to elicit an immunosuppressive response.

METHODS

Herein, we sought to dissect MSC's trophic mechanism from their efferocytic mechanisms and determine if the viability of MSCs prior to efferocytosis influences the resultant phenotype of monocytes. We cultured viable or heat-inactivated human umbilical cord MSCs with human peripheral blood mononuclear cells for 24 h and observed changes in monocyte surface marker expression and secretion profile. To isolate the effect of efferocytosis from MSC trophic factors, we used cell separation techniques to remove non-efferocytosed MSCs before challenging monocytes to suppress T-cells or respond to inflammatory stimuli. For all experiments, viable and heat-inactivated efferocytic-licensing of monocytes were compared to non-efferocytic-licensing control.

RESULTS

We found that monocytes efferocytose viable and heat-inactivated MSCs equally, but only viable MSC-licensed monocytes suppress activated T-cells and suppression occurred even after depletion of residual MSCs. This provides direct evidence that monocytes that efferocytose viable MSCs are immunosuppressive. Further characterization of monocytes after efferocytosis showed that uptake of viable-but not heat inactivated-MSC resulted in monocytes secreting IL-10 and producing kynurenine. When monocytes were challenged with LPS, IL-2, and IFN-γ to simulate sepsis, monocytes that had efferocytosed viable MSC had higher levels of IDO while monocytes that efferocytosed heat inactivated-MSCs produced the lowest levels of TNF-α.

CONCLUSION

Collectively, these studies show that the quality of MSCs efferocytosed by monocytes polarize monocytes toward distinctive immunosuppressive phenotypes and highlights the need to tailor MSC therapies for specific indications.

Placenta-specific protein 1 (PLAC1) expression is significantly down-regulated in preeclampsia via a hypoxia-mediated mechanism

OBJECTIVE

Examine a mechanism of PLAC1 regulation and its potential role in preeclampsia (PE).

MATERIALS AND METHODS

Placental tissue samples and detailed clinical information were obtained through the University of Iowa Maternal Fetal Tissue Bank (IRB# 200910784) from gestational and maternal age-matched control (n = 17) and PE affected pregnancies (n = 12). PLAC1 and PLAC1 promoter-specific expression was measured using quantitative polymerase chain reaction (qPCR) and differences were assessed via the standard ΔΔCt method. In addition, the role of hypoxia in PLAC1 transcription was investigated through the exposure of HTR8/SVneo human trophoblast cells to the hypoxia mimic dimethyloxaloylglycine (DMOG).

RESULTS

PLAC1 expression is seen to be 8.9-fold lower in human placentas affected by preeclampsia in comparison with controls (p < .05). Further, this decrease is paralleled by a significantly lower expression of the P2 or proximal PLAC1 promoter (p < .05). Expression of mediator complex subunit 1 (MED1), a known hypoxia-sensitive transcription coactivator and PLAC1 effector, is significantly correlated with PLAC 1 expression (r2 = 0.607, p < .001). These data suggest that PLAC1 expression is significantly down-regulated in preeclampsia at least in part via a MED1 hypoxia-mediated mechanism.

CONCLUSIONS

We confirm that PLAC1 transcription is suppressed in the placentae of women affected by preeclampsia. We further demonstrate that this suppression is driven through the P2 or proximal PLAC1 promoter. This demonstration led to the identification of the MED1-TRAP cofactor complex as the hypoxia-sensitive driver.

Reduced Maternal Circulating Cell-Free Mitochondrial DNA Is Associated With the Development of Preeclampsia

Background Circulating cell-free mitochondrial DNA (ccf-mtDNA) is a damage-associated molecular pattern that reflects cell stress responses and tissue damage, but little is known about ccf-mtDNA in preeclampsia. The main objectives of this study were to determine (1) absolute concentrations of ccf-mtDNA in plasma and mitochondrial DNA content in peripheral blood mononuclear cells and (2) forms of ccf-mtDNA transport in blood from women with preeclampsia and healthy controls. In addition, we sought to establish the association between aberrance in circulating DNA-related metrics, including ccf-mtDNA and DNA clearance mechanisms, and the clinical diagnosis of preeclampsia using bootstrapped penalized logistic regression. Methods and Results Absolute concentrations of ccf-mtDNA were reduced in plasma from women with preeclampsia compared with healthy controls (P≤0.02), while mtDNA copy number in peripheral blood mononuclear cells did not differ between groups (P>0.05). While the pattern of reduced ccf-mtDNA in patients with preeclampsia remained, DNA isolation from plasma using membrane lysis buffer resulted in 1000-fold higher ccf-mtDNA concentrations in the preeclampsia group (P=0.0014) and 430-fold higher ccf-mtDNA concentrations in the control group (P<0.0001). Plasma from women with preeclampsia did not induce greater Toll-like receptor-9-induced nuclear factor kappa-light-chain enhancer of activated B cells-dependent responses in human embryonic kidney 293 cells overexpressing the human TLR-9 gene (P>0.05). Penalized regression analysis showed that women with preeclampsia were more likely to have lower concentrations of ccf-mtDNA as well as higher concentrations of nuclear DNA and DNase I compared with their matched controls. Conclusions Women with preeclampsia have aberrant circulating DNA dynamics, including reduced ccf-mtDNA concentrations and DNA clearance mechanisms, compared with gestational age-matched healthy pregnant women.

Association between plasma leptin and cesarean section after induction of labor: a case control study

Background

Obesity in pregnancy is common, with more than 50% of pregnant women being overweight or obese. Obesity has been identified as an independent predictor of dysfunctional labor and is associated with increased risk of failed induction of labor resulting in cesarean section. Leptin, an adipokine, is secreted from adipose tissue under the control of the obesity gene. Concentrations of leptin increase with increasing percent body fat due to elevated leptin production from the adipose tissue of obese individuals. Interestingly, the placenta is also a major source of leptin production during pregnancy. Leptin has regulatory effects on neuronal tissue, vascular smooth muscle, and nonvascular smooth muscle systems. It has also been demonstrated that leptin has an inhibitory effect on myometrial contractility with both intensity and frequency of contractions decreased. These findings suggest that leptin may play an important role in dysfunctional labor and be associated with the outcome of induction of labor at term. Our aim is to determine whether maternal plasma leptin concentration is indicative of the outcome of induction of labor at term. We hypothesize that elevated maternal plasma leptin levels are associated with a failed term induction of labor resulting in a cesarean delivery.

Methods

In this case-control study, leptin was measured in 3rd trimester plasma samples. To analyze labor outcomes, 174 women were selected based on having undergone an induction of labor (IOL), (115 women with successful IOL and 59 women with a failed IOL). Plasma samples and clinical information were obtained from the UI Maternal Fetal Tissue Bank (IRB# 200910784). Maternal plasma leptin and total protein concentrations were measured using commercially available assays. Bivariate analyses and logistic regression models were constructed using regression identified clinically significant confounding variables. All variables were tested at significance level of 0.05.

Results

Women with failed IOL had higher maternal plasma leptin values (0.5 vs 0.3 pg, P = 0.01). These women were more likely to have obesity (mean BMI 32 vs 27 kg/m², P = 0.0002) as well as require multiple induction methods (93% vs 73%, p = 0.008). Logistic regression showed Bishop score (OR 1.5, p < 0.001), BMI (OR 0.92, P < 0.001), preeclampsia (OR 0.12, P = 0.010), use of multiple methods of induction (OR 0.22, P = 0.008) and leptin (OR 0.42, P = 0.017) were significantly associated with IOL outcome. Specifically, after controlling for BMI, Bishop Score, and preeclampsia, leptin was still predictive of a failed IOL with an odds ratio of 0.47 (P = 0.046). Finally, using leptin as a predictor for fetal outcomes, leptin was also associated with of fetal intolerance of labor, with an odds ratio of 2.3 (P = 0.027). This association remained but failed to meet statistical significance when controlling for successful (IOL) (OR 1.5, P = 0.50).

Conclusions

Maternal plasma leptin may be a useful tool for determining which women are likely to have a failed induction of labor and for counseling women about undertaking an induction of labor versus proceeding with cesarean delivery.

Abstract 30: Role For Adverse Childhood Experiences And Depression In Preeclampsia

Hypertensive diseases are associated with adverse experiences in childhood as well as depression. In order to determine if these associations were present in women with preeclampsia (PreE), a particularly devastating hypertensive disease in pregnancy, the scores from three questionnaires: Adverse Childhood Experiences (ACE), Edinburgh Postnatal Depression Scale (EPDS), and the Patient Health Questionnaire-9 (PHQ-9) were compared between women with PreE (n=32) and women without PreE (n=46) between 9 and 48 months postpartum (IRB# 201808705). ACE scores are calculated by summing an individual’s affirmative responses to specific adverse experiences during childhood. In our study, the average ACE score of individuals with PreE was higher than that of women without PreE (1.69 vs. 1.02, P=.04). We also divided women into groups based on whether their ACE score was ≤3 or ≥4 due to evidence that individuals who have experienced ≥4 ACEs are at greatest risk for physical and mental health conditions. Among our participants, 80% of women with an ACE score ≥4 (n=10) had PreE while only 35.3% of women with a score ≤3 (n=68) developed the condition (P=0.01). As well, the odds of having PreE were higher in those with ACE scores ≥4, compared with those with scores ≤3 (OR= 7.34; 95% CI = 1.44, 37.33). In a subset of participants, scores were available from EPDS, survey that identifies women who have postpartum depression 6 weeks after birth, and from the PHQ-9, another assessment for depression. Among our participants, the average EPDS score was higher in women with PreE than women without PreE (6.38, n=21 vs. 3.71, n=42 P=0.01), indicating more severe symptoms of postpartum depression in women who also had PreE. In addition, the average PHQ-9 score among women with PreE was higher than that of women without PreE (3.71, n=15 vs 1.86, n=37 P=.02) with a higher score indicating more severe depression. The average PHQ-9 score was also higher in women who had ACE scores ≥4 than women with scores ≤3 (4.00, n=4 vs. 2.27, n=48 P=.01) indicating that women with more adverse childhood events were more likely to experience depression. Together, these findings indicate that PreE may be associated with adverse events during childhood as well as depression in late pregnancy and/or postpartum.

Abstract P209: Loss Of Rgs2 Specifically In CD4+ T Cells Decreases The Hypertensive Response To Vasopressin

Regulator of G protein Signaling (RGS) family members can modulate multiple cardiovascular hormones and are associated with hypertension and preeclampsia, a hypertensive disorder in pregnancy. We previously observed a 9-fold increase in RGS2 in CD4+ T cells isolated from women with preeclampsia compared to normotensive women. Further, in non-pregnant mice, we showed that loss of RGS2 in CD4+ T cells prevented angiotensin II-induced hypertension (measured via radiotelemetry) and resulted in increased levels of the anti-inflammatory cytokines interleukin 4 and transforming growth factor beta. We hypothesize that modulating RGS2 in CD4+ T cells may be a therapeutic strategy for hypertension. The objective of this study was to determine if loss of RGS2 specifically in CD4+ T cells protects against the development of arginine vasopressin-induced hypertension in mixed background CD4+ RGS2 knockout mice (CD4 RGS2 KO ). To generate mice wherein RGS2 is specifically knocked out in CD4+ T cells, CD4-Cre+ mice (C57BL/6J) were crossed with RGS2 flox/flox mice (B6SJLF1/J). Female 8-12 week old CD4 RGS2 KO or littermate control mice (n=5 per group) from this mixed strain were administered 24 ng/hr vasopressin for 21 days via mini-osmotic pump. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MP), and heart rate (HR) were assessed using a high throughput non-invasive blood pressure system. Prior to vasopressin infusion, KO and CTL mice showed no differences in SBP, DBP, MP, or HR. At 9-13 days of vasopressin-infusion, KO mice had a significantly lower 24-hr SBP [KO 138.7 ±4.7 vs CTL 155.9 ±3.4 mmHg, p<0.05], DBP [KO 106.9 ±4.1 vs CTL 122.8 ±2.9 mmHg, p<0.05], MP [KO 117.2 ±4.3 vs CTL 133.5 ±3.0 mmHg, p<0.05], and HR [KO 378 ±18.7 vs CTL 445 x±12.8 BPM, p<0.05] compared to CTL mice. Here, we demonstrate that in a mixed strain CD4+ RGS2 KO mouse, loss of RGS2 specifically in CD4+ T cells prevented vasopressin-induced hypertension. Therefore, RGS2 expression in CD4+ T cells may play an expanded role in the modulation of hypertension.

Beat-to-Beat Blood Pressure Variability in the First Trimester Is Associated With the Development of Preeclampsia in a Prospective Cohort: Relation With Aortic Stiffness

Women with preeclampsia, a hypertensive disorder of pregnancy, exhibit greater beat-to-beat blood pressure variability (BPV) in the third trimester after clinical onset of the disorder. However, it remains unknown whether elevated BPV precedes the development of preeclampsia. A prospective study cohort of 139 women (age 30.2±4.0 years) were enrolled in early pregnancy (<14 weeks gestation). BPV was quantified by time domain analyses of 10-minute continuous beat-to-beat blood pressure recordings via finger photoplethysmography in the first, second, and third trimesters. Aortic stiffness (carotid-femoral pulse wave velocity) and spontaneous cardiovagal baroreflex sensitivity were also measured each trimester. Eighteen women (13%) developed preeclampsia. Systolic BPV was higher in all trimesters among women who developed versus did not develop preeclampsia (first: 4.8±1.3 versus 3.7±1.2, P=0.001; second: 5.1±1.8 versus 3.8±1.1, P=0.02; third: 5.2±0.8 versus 4.0±1.1 mm Hg, P=0.002). Elevated first trimester systolic BPV was associated with preeclampsia (odds ratio, 1.94 [95% CI, 1.27-2.99]), even after adjusting for risk factors (age, body mass index, systolic blood pressure, history of preeclampsia, and diabetes mellitus) and was a significant predictor of preeclampsia (area under the receiver operator characteristic curve=0.75±0.07; P=0.002). Carotid-femoral pulse wave velocity was elevated in the first trimester among women who developed preeclampsia (5.9±0.8 versus 5.2±0.8 m/s; P=0.002) and was associated with BPV after adjustment for mean blood pressure (r=0.26; P=0.005). First trimester baroreflex sensitivity did not differ between groups (P=0.23) and was not related to BPV (P=0.36). Elevated systolic BPV is independently associated with the development of preeclampsia as early as the first trimester, possibly mediated in part by higher aortic stiffness.

Abstract 3: Preeclampsia-induced T Helper-associated Cytokine Imbalances Persist Postpartum

Preeclampsia (PreE), a hypertensive disorder in pregnancy, contributes to long-term maternal cardiovascular disease risk. By 2025, it is estimated that more women than men will have hypertension (HTN), yet the mechanisms contributing to the development of HTN in women are less understood. One potential mechanism underlying HTN in women is a persistent imbalance of anti- and pro- inflammatory T H cells following PreE. Consistent with this, anti-inflammatory T helper (T H ) cytokines are reduced and pro-inflammatory T H cytokines are increased during a PreE pregnancy.

De-identified and coded plasma samples and clinical data were obtained from the Magee-Women’s Research Institute & Foundation or the University of Iowa Maternal-Fetal Tissue Bank (IRB 201808705) from women 1-3 (N=93) or 8-10 (N=58) years (yrs) following a normotensive (CTL) or PreE-affected pregnancy. Postpartum (PP) HTN was defined as having stage 1 or higher HTN as designated in the updated 2017 ACC/AHA guidelines. Women with PreE had higher rates of HTN at 1-3 years and at 8-10 years PP, (24% vs. 5% and 65% vs. 17%, all p<0.05) compared to women with a normotensive pregnancy.

To determine if T H cells play a role in the future development of HTN, we investigated if the T H cytokine changes observed in PreE persist 1-3 yrs and 8-10 yrs PP. Cytokine concentrations were determined via ELISAs and normalized to total protein. Average cytokine concentrations are reported in pg/g. At 1-3 yrs PP, concentrations of anti-inflammatory cytokines IL-4 (47 vs. 6819, p<0.05), IL-10 (1204 vs. 15042, p<0.05) and TGFβ (8.2x10 5 vs. 4.4x10 6 , p<0.05) were reduced in women with a prior PreE pregnancy vs. women with a CTL pregnancy. At 8-10 yrs PP, pro-inflammatory IL-6 (86 vs. 18, p<0.05) and TNFα (298 vs. 53, p<0.05) were both significantly increased in women with prior PreE compared to women with a CTL pregnancy.

Here, we confirm women with a prior PreE pregnancy present with a higher prevalence of HTN early (1-3 yrs) and later (8-10 yrs) PP compared to women with a normotensive pregnancy. Further, we show an altered T H cytokine milieu persists following delivery in women with PreE. This pro-inflammatory milieu is associated with increased rates of HTN and thus, may underlie the future development of HTN in women with a history of PreE.

Abstract P186: Position Effects Blood Pressure Measurement During Pregnancy

Hypertension in pregnancy is a leading cause of maternal morbidity and mortality. Studies demonstrate that body positions affect the blood pressure (BP) measurements and have led to guidelines for proper positioning by the ACC and AHA. However, studies excluded pregnant women and did not include all common patient positions, such as semi-Fowlers. These studies cannot be applied to pregnant women due to dynamic cardiovascular changes in pregnancy. We measured BP in pregnant women in inpatient and outpatient settings in various positions. These BPs were compared to the published ACC/AHA guideline position: seated with arms and feet supported. Trained team members used an aneroid sphygmomanometer and stethoscope and/or a validated electronic BP machine. There is no significant difference between BP measurements using a sphygmomanometer/stethoscope vs. an electronic BP machine in the ACC/AHA guideline position (systolic p=0.60 diastolic p=0.91). There was not a significant difference in either systolic or diastolic means in the semi-Fowlers position (at 45 degrees measured by goniometer) (systolic=0.60 diastolic=0.95). Positioning did affect the diastolic BP measurement in the seated without support position (p=0.01) and both the systolic (p< 0.001) and diastolic (p<0.001) measurements in the left lateral recumbent position. Our data demonstrate that an accurate BP measurement in pregnancy is dependent upon patient position. Monitoring BP position in left lateral recumbent may mask an elevated BP. This study also suggests that it may be possible to substitute semi-Fowlers position for reliable BP measurements when chair sitting is not practical, such as labor.

Abstract P137: Knock Out Of Regulatory G Protein Signaling 2 Specifically In CD4 T Cells Prevents Angiotensin II Induced Hypertension

Preeclampsia (PreE) is a hypertensive disorder in pregnancy. Aberrations of Regulator of G protein Signaling (RGS) family members are associated with PreE and hypertension (HTN). We previously observed a 9-fold increase in RGS2 in CD4+ T cells during PreE. In total, our work suggests that modulating T cells may be a therapeutic strategy for HTN. We hypothesize that reducing RGS2 specifically in CD4+ T cells will restore anti-inflammatory T cell responses and prevent HTN.

Utilizing an angiotensin (ANG) II infusion mouse model, we aimed to investigate 1) the impact of the loss of RGS2 in CD4+ T cells on cytokine production and 2) if the loss of RGS2 in CD4+ T cells will protect against the development of HTN. RGS2 was knocked-out in CD4+ T cells (CD4-Cre x RGS2 flox mice; KO ). CD4 RGS2 KO (n=5) or littermate control mice (CTL, n=3) were administered 490 ng/kg/min ANG II for 21 days via mini-osmotic pump. Blood pressure was assessed by radiotelemetry. ELISAs were performed to determine pro- and anti- inflammatory cytokine levels in tissues from KO (n=9) and CTL (n=8) mice.

Pro-inflammatory cytokines IFNγ and IL-17 were not significantly different in the heart, kidney, liver or spleen of KO vs CTL mice. The anti-inflammatory cytokines IL-4 (KO 410 vs CTL 339 pg/mL, p<0.05) and TGFβ (KO 5.7x10 5 vs 5.0x10 5 pg/mL, p<0.05) were increased in the kidneys of KO mice compared to CTL mice. At baseline, KO and CTL mice showed no differences in 24-hr heart rate (HR), systolic or diastolic blood pressure (SBP and DBP, respectively). Throughout the study, KO mice had a significantly lower 24-hr SBP (Day 7: KO 132.3 vs CTL 149.7 mmHg, p<0.05; Day 14: KO 123.6 vs CTL 162.3 mmHg, p<0.05; Day 21: KO 118.3 vs 154.8 mmHg, p<0.05) and DBP (Day 7: KO 101.2 vs CTL 113.8 mmHg, p<0.05; Day 14: KO 98.4 vs CTL 121.8 mmHg, p<0.05; Day 21: KO 96.8 vs 116.4 mmHg, p<0.05) compared to CTL mice. The 24-hr HR was only significantly lower at three weeks ANG II (KO 493.4 vs CTL 540.6 bpm, p<0.05) compared to CTL mice.

The increased levels of IL-4 and TGFβ observed in KO mice support a role of RGS2 in anti-inflammatory immune responses. In accordance with our hypothesis, the loss of RGS2, specifically in CD4+ T cells prevented ANG II-induced hypertension. Therefore, RGS2 expression in CD4+ T cells plays a critical role in the development of HTN.

Reduced mRNA Expression of RGS2 (Regulator of G Protein Signaling-2) in the Placenta Is Associated With Human Preeclampsia and Sufficient to Cause Features of the Disorder in Mice

Cascade-specific termination of G protein signaling is catalyzed by the RGS (regulator of G protein signaling) family members, including RGS2. Angiotensin, vasopressin, and endothelin are implicated in preeclampsia, and RGS2 is known to inhibit G protein cascades activated by these hormones. Mutations in RGS2 are associated with human hypertension and increased risk of developing preeclampsia and its sequelae. RGS family members are known to influence maternal vascular function, but the role of RGS2 within the placenta has not been explored. Here, we hypothesized that reduced expression of RGS2 within the placenta represents a risk factor for the development of preeclampsia. Although cAMP/CREB signaling was enriched in placentas from human pregnancies affected by preeclampsia compared with clinically matched controls and RGS2 is known to be a CREB-responsive gene, RGS2 mRNA was reduced in placentas from pregnancies affected by preeclampsia. Experimentally reducing Rgs2 expression within the feto-placental unit was sufficient to induce preeclampsia-like phenotypes in pregnant wild-type C57BL/6J mice. Stimulation of RGS2 transcription within immortalized human HTR8/SVneo trophoblasts by cAMP/CREB signaling was discovered to be dependent on the activity of histone deacetylase activity, and more specifically, HDAC9 (histone deacetylase-9), and HDAC9 expression was reduced in placentas from human pregnancies affected by preeclampsia. We conclude that reduced expression of RGS2 within the placenta may mechanistically contribute to preeclampsia. More generally, this work identifies RGS2 as an HDAC9-dependent CREB-responsive gene, which may contribute to reduced RGS2 expression in placenta during preeclampsia.

Abstract P3038: Reduced Renal Responsiveness and Altered Fluid Volume in an African Green Monkey ( Chlorocebus Aethiops Sabaeus) Preeclampsia Model

Preeclampsia is a prevalent, multi-organ complication of late pregnancy characterized by de novo gestational hypertension (GH) and proteinuria. Our group has demonstrated that arginine vasopressin (AVP) secretion, as measured by copeptin, is predictive of the development of human preeclampsia. Altered regulation of AVP early in gestation has been demonstrated in human preeclampsia. Recently, the nonhuman primate, African Green Monkey (AGM) has been characterized as a spontaneous, translational model of chronic hypertension, GH and preeclampsia. AGMs also have similar gestation and placentation to humans. We hypothesized that the AGM model of preeclampsia would demonstrate similar AVP related plasma and fluid volume changes as humans with preeclampsia. AGMs (n=10) were anesthetized with ketamine during late third trimester of pregnancy to obtain physiologic and obstetric measurements. Compared to normotensive (NT, n=4) third trimester pregnant females, GH females (n=6) had higher systolic and diastolic blood pressures (106 ± 5 vs. 162 ± 11 mmHg; 46 ± 4 vs. 86 ± 12, p=0.01) with no differences in heart rates (158 ± 4 vs. 169 ± 18 bpm, p=0.64). Consistent with other models of GH and preeclampsia, the GH AGM had decreased offspring birthweight in comparison to NT offspring (352 ± 11 vs. 275 ± 12 g, p=0.01). Further, plasma osmolality of GH females was higher in late third trimester compared to NT females (286 ± 11 vs. 312 ± 9 mOsm, p=0.05). This higher plasma osmolality was associated with the GH female’s trend to higher AVP secretion as measured by copeptin (2 ± 2 vs. 4 ± 1 ng/g, p=0.280). In contrast to human pregnancies, late third trimester plasma [Na + ] of GH females was elevated compared to NT females (149 ± 3 vs. 157 ± 2 mMol/L, p=0.04). These data demonstrate that that the AGM model of preeclampsia replicates the plasma volume restricted findings consistent with human preeclampsia and possible insensitivity to control by AVP. Ongoing studies in early pregnancy will quantify changes in renal function during preeclampsia, differences in fluid volumes among NT and GH AGMs, and further the understanding of hormonal regulation of kidney function in the pathogenesis of preeclampsia in this translational AGM nonhuman primate.

Abstract 030: Low Indoleamine 2,3 Dioxygenase Activity in Pregnancy are Associated With Increased Carotid-Femoral Pulse Wave Velocity in Preeclampsia

Preeclampsia is a prevalent multi-organ complication of pregnancy that is characterized by gestational hypertension and proteinuria. Immunologic and vascular alterations clearly occur before clinical disease. One mechanism that could explain both the exaggerated immune response and vascular dysfunction involves indoleamine 2, 3 dioxygenase (IDO). We have previously shown that the IDO-KO mouse replicates the vascular and obstetric phenotypes of human preeclampsia. We hypothesize that decreases in IDO activity are associated with vascular dysfunction as measured by carotid-femoral pulse wave velocity (PWV), a measure of aortic stiffness. We test this hypothesis in this nested case control study of two similarly recruited prospective cohorts (Preeclampsia IDO Vascular Function and Perinatal Outcomes study IRB: 201009701), and the (Early Vascular Dysfunction and Elevated Copeptin in Human Preeclampsia study IRB: 201503789). A total of 136 control and 13 preeclamptic pregnant women were recruited to measure vascular function and immunovascular factors throughout gestation. Plasma IDO activity was colorimetrically measured and trimester specific quartiles for IDO activity were calculated. PWV was measured via tonometry. Highest and lowest IDO activity quartile groups were compared. First trimester IDO activity was not associated with differences in PWV throughout gestation. Lower second and third trimester IDO activity was associated with higher PWV throughout gestation (1 st trimester: 6.8 ± 0.3 vs 5.5 ± 0.2, P<0.001; 2 nd trimester: 7.1 ± 0.4 vs 5.1 ± 0.2 P<0.001; 3 rd trimester 6.5 ± 0.2 vs 5.9 ± 0.2 m/s, P<0.001). Even after controlling for preeclampsia, third trimester IDO activity was inversely associated with PWV (Beta IDO=-11, p=0.023 and Beta preeclampsia=0.150, p=0.753). Consistent with our hypothesis, our data demonstrate IDO activity is inversely associated with vascular dysfunction. Future studies will elucidate the molecular immunovascular mechanisms underlying this association in preeclampsia.

Abstract P3039: Altered Maternal and Fetal Vasopressin Receptors in Response to Hypertensive Stress in Pregnancy

Children born to women with hypertensive disorders in pregnancy have an elevated risk of developing hypertensive disorders later in life. The mechanisms for this fetal programming are unclear. Because vasopressin (AVP) is a hormone that functions to regulate blood pressure and volume homeostasis, we hypothesized that differences in expression of vasopressin receptors (AVPRs) and related genes are also altered in children born from preeclampsia-affected pregnancies. We measured the expression of receptors AVPR1a, AVPR1b, AVPR2, OXTR, and CUL5 as well as LNPEP, the major aminopeptidase that cleaves AVP. Expression in umbilical cord blood cells and maternal peripheral blood cells from women with 1) no hypertensive disorders in pregnancy (control subjects) (N=20) 2) pregnant women with chronic hypertension (N=20) and 3) women with preeclampsia (N=10) in the index pregnancy were compared. Coded cell samples and associated clinical data were obtained from the University of Iowa Maternal Fetal Tissue Bank (IRB# 200910784). RNA was purified from the cells and used for real-time quantitative PCR to assess variation in receptor expression in children born to women with hypertensive disorders of pregnancy relative to control subjects. In children born to women with chronic hypertension, AVPR2 (-8.2 Fold Change, P<0.001), LNPEP (-13 Fold Change, P<0.001), CUL5 (-14 Fold Change, P<0.001), AVPR1b (-3.1 Fold Change, P=0.001), and OXTR (-4.3 Fold Change) were all significantly under-expressed when compared to normotensive controls. Samples from children born to women with preeclampsia had significantly lower expression of AVPR1a (-4.7 Fold Change, P<0.001), AVPR1b (-2.5 Fold Change, P=0.045), AVPR2 (-2.5 Fold Change, P=0.001), and OXTR (-2.8 Fold Change, P<0.001) when compared to non-preeclamptic samples. Differences in expression were also mirrored early in pregnancy in maternal blood in women with chronic hypertension. For example, CUL5 and LNPEP were decreased in the first trimester (-3.01 Fold Change, P=0.004 and -3.64 Fold Change P=0.007, respectively). The differences in gene expression in cord blood may be related to the future risk of hypertension later in life for children born to women with hypertensive diseases in pregnancy.

Abstract P132: Differential and Sex Dependent Expression of Vasopressin Receptors by B Cells, NK Cells, and Dendritic Cells

Arginine vasopressin (AVP) has been shown to play a role in preeclampsia, a hypertensive and immune-mediated disorder in pregnancy. Chronic infusion of AVP during gestation into wild-type mice results in the pregnancy-specific physiological changes (hypertension, kidney damage, fetal growth restriction) as well as increased CD4+ T H 1 and T H 17 associated cytokine responses observed in human pregnancies affected by preeclampsia. Further, human CD4+ T cells isolated from preeclamptic women were found to differentially express AVP receptors (AVPRs) 1a and 2 compared to control pregnancies. Abnormalities in other immune cells are seen during preeclampsia, including auto-antibody production (B cells), poor placental development (natural killer (NK) cells), and increased pro-inflammatory T cells responses (via dendritic cells (DC)). We, therefore, hypothesize that B cells, NK cells, and DC express AVPRs. To begin to understand 1) the expression pattern of AVPRs on CD4- lymphocytes and 2) if there are differences in expression between males and females, we evaluated the expression of AVPR 1a, 2, and 1b specifically on B cells, NK cells, and DC. Each subset was purified via negative selection from de-identified human peripheral blood mononuclear cells obtained through Leukocyte Reduction System (LRS) cone donors at the DeGowin Blood Center followed by qPCR for AVPR 1a, 2, and 1b expression (N=6 per cell type). B cells, NK cells, and DC expressed all three AVPRs 1a, 2, and 1b. All three lymphocyte populations showed a lower expression of AVPR1b compared to expression of 1a and 2, with B cells having the lowest expression of AVPR1b (p<0.05). Interestingly, while B cells and NK cells showed no differences in expression based on sex of the donor, DC isolated from male donors more highly expressed AVPR1b compared to female donors (p=0.0035). In conclusion, we demonstrate that B cells, NK cells, and DC highly express AVPR1a and 2, and that DC expression of AVPRs is sex dependent. Further investigation into the utilization of these receptors by these immune cells and the potential impact of sex-specific differences may elucidate newly identified mechanisms of AVP and immune interactions in not only preeclampsia, but possibly other cardiovascular-related diseases as well.

Arginine vasopressin infusion is sufficient to model clinical features of preeclampsia in mice

Copeptin, a marker of arginine vasopressin (AVP) secretion, is elevated throughout human pregnancies complicated by preeclampsia (PE), and AVP infusion throughout gestation is sufficient to induce the major phenotypes of PE in mice. Thus, we hypothesized a role for AVP in the pathogenesis of PE. AVP infusion into pregnant C57BL/6J mice resulted in hypertension, renal glomerular endotheliosis, intrauterine growth restriction, decreased placental growth factor (PGF), altered placental morphology, placental oxidative stress, and placental gene expression consistent with human PE. Interestingly, these changes occurred despite a lack of placental hypoxia or elevations in placental fms-like tyrosine kinase-1 (FLT1). Coinfusion of AVP receptor antagonists and time-restricted infusion of AVP uncovered a mid-gestational role for the AVPR1A receptor in the observed renal pathologies, versus mid- and late-gestational roles for the AVPR2 receptor in the blood pressure and fetal phenotypes. These findings demonstrate that AVP is sufficient to initiate phenotypes of PE in the absence of placental hypoxia, and indicate that AVP may mechanistically (independently, and possibly synergistically with hypoxia) contribute to the development of clinical signs of PE in specific subtypes of human PE. Additionally, they identify divergent and gestational time-specific signaling mechanisms that mediate the development of PE phenotypes in response to AVP.

Abstract P311: Static Urine Osmolality With Elevated First Trimester Urine Copeptin in Human Preeclampsia

We have previously shown that maternal plasma copeptin (CPP), as a marker of vasopressin, is highly predictive of preeclampsia (PE) in the first trimester and remains elevated throughout pregnancy. Furthermore, in maternal urine samples we demonstrated that CPP was also significantly elevated in the first trimester in women who later developed PE. Because a urine dipstick test could be easily used in the clinic, we sought to validate this finding in a new and expanded cohort of samples and to determine whether these changes persist throughout pregnancy. In addition, to begin to address the mechanism for this difference, we also assessed urine osmolality to further probe renal function. In a case-control study (IRB# 2015038355), banked maternal urine samples and clinical data from each trimester from women who developed PE (N=117) and controls (N=593) were obtained from the University of Iowa Maternal Fetal Tissue Bank (MFTB) (IRB# 200910784). CPP concentrations were measured by ELISA. Osmolality was determined by freezing point depression. Differences between groups were detected by Chi square, Student’s T Test, or ANOVA as appropriate. Using a validation cohort and a different ELISA (USCN vs Phoenix Pharmaceuticals), we validated our earlier findings. We again find a significant increase in the concentration of urine CPP in the first trimester in women who developed preeclampsia compared to women who did not (0.304 ± 0.03 vs 0.223 ± 0.01 pg/ml, P =0.03). No significant differences in copeptin were observed in urine CPP in the 2nd and 3rd trimesters from PE and control women (2 nd tri: 0.205 ± 0.04 vs 0.213 ± 0.02; 3 rd tri: 0.290 ± 0.03 vs 0.336 ± 0.02 pg/ml P >0.05 in 2 nd and 3 rd trimesters). In this cohort, we did not detect differences in urine osmolality between preeclamptics and controls in any trimester (1 st tri: 606.09 ± 50.16 vs 604.28 ± 16.72; 2 nd tri 582.10 ± 36.30 vs 596.96 ± 16.98; 3 rd tri: 479.63 ± 58.81 vs 583.75 ± 19.61 mOsm/kg H 2 O). We conclude that (i) PE is associated with increased maternal urinary CPP in the 1st trimester, (ii) this increase does not correlate with expected increases in urine osmolality. Future work will focus on understanding the mechanisms involved in the elevation in urinary CPP such as early immunologic changes or renal concentrating responses.

Abstract 014: Betamethasone: A Novel Therapeutic Intervention for Preeclampsia

The early pathogenesis of preeclampsia (PE) involves a systemic inflammatory immune response. Recent data demonstrate that increased circulating arginine vasopressin (AVP) in humans is predictive of PE and that infusion of AVP in mouse dams phenocopies the pregnancy-specific cardiovascular and immune alterations observed in human PE. Specifically, AVP suppresses anti-inflammatory cytokines and cells. Betamethasone (BMTZ), commonly given to women at risk for preterm birth, is both an AVP and immune response modulator. We hypothesize that early treatment with BMTZ will prevent the development of AVP-induced PE. C57BL/6J dams were infused with AVP (24 ng/hour) or saline throughout gestation via osmotic minipump. AVP dams received a single subcutaneous injection of BMTZ (100ug) early post-placentation (gestational day (GD) 7). Blood pressure was measured throughout pregnancy. Total protein was measured on 24 hour urine collected on GD 17. Maternal and fetal tissues were collected on GD 18. Cytokine concentrations were determined via commercially available ELISAs and normalized to total protein. BMTZ reversed the hypertension (ANOVA n=11, p=0.007) and proteinuria (ANOVA n=11, p=0.025) induced by AVP. BMTZ reversed the AVP-induced decreases in the maternal and fetal anti-inflammatory responses. In maternal kidney, both anti-inflammatory IL-4 (AVP: 0.034, n=10 vs BTMZ: 0.092, n=5 ug/g, p<0.05) and TGFb (AVP: 4.3, n=10 vs BTMZ: 9.2, n=5 ug/g, p<0.05) were increased in BMTZ-treated dams. Decreases in fetal kidney IL-4 (AVP: 0.013, n=5 vs BTMZ: 0.043, n=5 ug/g, p<0.05), IL-10 (AVP: 1.2, n=5 vs BTMZ: 2.1, n=5 ug/g, p=0.05), and TGFb (AVP: 1.8, n=5 vs BMTZ: 2.9, n=5 ug/g, p<0.05) were reversed with BMTZ treatment. Lastly, placental concentrations of IL-4 (AVP: 0.002, n=5 vs BTMZ: 0.005, n=5 ug/g, p<0.05) and TGFb (AVP: 0.090, n=5 vs BTMZ: 1.4, n=5 ug/g, p<0.05) were also improved following BMTZ in AVP-infused dams. Supportive of our hypothesis, early BMTZ treatment prevented hypertension and reduced proteinuria in AVP-infused dams. BMTZ also reversed AVP-induced inhibition of anti-inflammatory responses, creating a more tolerogenic milieu. These data support the concept for the potential use of BMTZ in early gestation as a novel preventative agent for PE.

Abstract P314: Regulatory Dendritic Cell Treatment Prevents the Development of Vasopressin-Induced Preeclampsia

The concept that persistent feto-placental intolerance is important in the pathogenesis of preeclampsia (PE) has been demonstrated by our lab and others. Arginine vasopressin (AVP) infusion during pregnancy induces cardiovascular, renal, and immune alterations in mice consistent with human PE. These findings identify AVP as a potential contributor to poor fetal tolerance and the development of PE. In addition to their conventional immuno-stimulatory role, dendritic cells (DCs) also play a vital role in immune tolerance. In contrast to conventional DCs, regulatory DCs (DCregs) express low levels of co-stimulatory markers, produce anti-inflammatory cytokines, induce T regulatory cells, and promote tolerance. In mice, DCregs are able to prevent pro-inflammatory responses and induce antigen-specific tolerance. Given these known functions of DCregs, we hypothesize that DCregs will prevent the development of AVP-induced PE. C57BL/6J dams were infused with AVP (24 ng/hour) or saline throughout gestation via osmotic minipump. To generate DCregs, bone marrow derived cells from C57BL/6J mice were cultured with human TGF-b1, and murine GM-CSF and IL-10 and phenotype confirmed via flow cytometry. At the time of pump implantation or early post-placentation on gestational day (GD) 7, AVP dams received a single intravenous injection of DCregs. Blood pressure was taken throughout pregnancy and total urine protein was measured on GD 17. Maternal tissues were collected on GD 18. Cytokine concentrations were determined via commercially available ELISAs and normalized to total protein. Treatment of AVP-infused dams with DCregs before mating (GD -3) and on GD 7 prevented AVP-induced hypertension (AVP: 120 ±1.8, n=27 vs GD -3: 108 ±3.3, n=7 vs GD 7: 110 ±4.4, n=5 p<0.05) and elevations in urine protein (AVP: 37.4 ±2.3, n=24 vs GD -3: 25.6 ±2.9, n=7 vs GD 7: 24.1 ±3.1, n=5 p<0.05). Treatment with DCregs also reversed AVP-induced suppression of anti-inflammatory TGFb (AVP: 1.3, n=9 vs GD -3: 3.2, n=7 vs GD 7: 2.9, n=5 ug/g, p<0.05) in the plasma. These data support the hypothesis that DCreg treatment prevents AVP-induced PE. It further provides evidence for the use of personalized, cellular therapy in the prevention of cardiovascular, renal, and immune alterations induced in PE.

Elevated vasopressin in pregnant mice induces T-helper subset alterations consistent with human preeclampsia

The pathogenesis of preeclampsia (PreE), a hypertensive disorder of pregnancy, involves imbalanced T helper (TH) cell populations and resultant changes in pro- and anti-inflammatory cytokine release. Elevated copeptin (an inert biomarker of arginine vasopressin (AVP)), secretion precedes the development of symptoms in PreE in humans, and infusion of AVP proximal to and throughout gestation is sufficient to initiate cardiovascular and renal phenotypes of PreE in wild-type C57BL/6J mice. We hypothesize that AVP infusion in wild-type mice is sufficient to induce the immune changes observed in human PreE. AVP infusion throughout gestation in mice resulted in increased pro-inflammatory interferon γ (IFNg) (TH1) in the maternal plasma. The TH17-associated cytokine interleukin (IL)-17 was elevated in the maternal plasma, amniotic fluid, and placenta following AVP infusion. Conversely, the TH2-associated anti-inflammatory cytokine IL-4 was decreased in the maternal and fetal kidneys from AVP-infused dams, while IL-10 was decreased in the maternal kidney and all fetal tissues. Collectively, these results demonstrate the sufficiency of AVP to induce the immune changes typical of PreE. We investigated if T cells can respond directly to AVP by evaluating the expression of AVP receptors (AVPRs) on mouse and human CD4+ T cells. Mouse and human T cells expressed AVPR1a, AVPR1b, and AVPR2. The expression of AVPR1a was decreased in CD4+ T cells obtained from PreE-affected women. In total, our data are consistent with a potential initiating role for AVP in the immune dysfunction typical of PreE and identifies putative signaling mechanism(s) for future investigation.

Abstract P262: Vasopressin Receptors Regulate Immune Responses in Preeclampsia

The pathogenesis of preeclampsia (PE) involves imbalanced T helper (T H ) cell populations and resultant changes in pro- and anti-inflammatory cytokine release. Elevated secretion of arginine vasopressin (AVP) precedes the development of symptoms in PE in humans, and chronic infusion of AVP (24 ng/hr s.c.) throughout gestation is sufficient to initiate cardiovascular, renal, and immune phenotypes of PE in wild-type C57BL/6J mice. We hypothesize that increased AVP signaling may mediate the immune changes observed in PE. AVP infusion throughout gestation in mice resulted in increased pro-inflammatory IFNγ (T H 1) in the maternal plasma (N=7, p<0.05) and IL-17 (T H 17) in the placenta (N≥10, p<0.001). The T H 2-associated anti-inflammatory cytokines IL-4 and IL-10 were decreased in maternal kidney (IL-4: N=8, p<0.05; IL-10: N=5, p<0.01) and fetal kidney (IL-4: N=5, p<0.05; IL-10: N=5, p<0.05) of AVP-infused dams. To elucidate the receptor dependency of these effects, AVP-infused dams were simultaneously treated with chronic infusion of AVP V 1A and/or V 2 receptor antagonists (22 ng/hr s.c). Combined blockade of V 1a +V 2 receptors by conivaptan, as well as specifically blocking V 2 by tolvaptan, corrected AVP induced reductions in IL-4 in maternal (conivaptan: N=5, p<0.05; tolvaptan: N=5, p<0.0.0001) and fetal kidneys (conivaptan: N=5, p<0.0001; tolvaptan: N=5, p<0.05). These data implicate V 2 as the receptor involved in kidney IL-4 deficiency in PE, whereby blockade of V 2 restores IL-4, preventing inflammation. Combined blockade of V 1A +V 2 receptors by conivaptan corrected the placental loss of IL-4 (N=5, p<0.05), whereas blockade of either receptor alone was insufficient, suggesting loss of placental IL-4 via AVP is mediated by both V 1a and V 2 receptors. In contrast, increased placental IL-17 was only corrected by selective blockade of V 1A by relcovaptan (N=5, p<0.05), suggesting a novel role for V1a receptor in pro-inflammatory placental IL-17 production in PE. Collectively these results demonstrate the sufficiency of AVP to induce the immune changes typical of PE, and support a dominant role for V 1A in the induction of pro-inflammatory IL-17 (T H 17) release versus a dominant role for V 2 receptors in the suppression of anti-inflammatory IL-4 (T H 2) release.

Abstract P256: Vasopressin Infusion During Pregnancy in Mice Induces Early Histological Placental Phenotypes of Preeclampsia

Human preeclampsia (PE) is associated with elevated secretion of arginine vasopressin (AVP), and chronic infusion of AVP into pregnant mice is sufficient to model PE by causing hypertension, renal glomerular endotheliosis, proteinuria, fetal placental hypoxia, and growth restriction. Early stages of PE are associated with defective trophoblast invasion of maternal spiral arteries, leading to decreased artery diameter and placental oxygenation. AVP infusion (24 ng/hr, sc) into pregnant mice caused placental hypoxia (chromatin-bound HIF1α on gestational day (GD)17.5; saline n=5, 0.31±0.01; AVP n=5, 0.34±0.01 AU, p<0.05) and reduced placental growth factor mRNA (n=18, 1.0 (0.7-1.3) vs n=21, 0.3 (0.2-0.4) fold (1 se), p<0.05). Therefore, we performed histological analyses of placentas collected from mice at GD12.5 infused with saline or AVP, with the hypothesis that AVP leads to early placental PE phenotypes. Similar to effects on GD17.5, this preliminary cohort demonstrated increased urine protein content (n=7, 27±3 vs n=13, 44±3, g/L p<0.05) and mid-gestational systolic blood pressure (-7.6±3.1 vs +3.5±2.2, mmHg p<0.05), similar fetal (75±7 vs 78±4 mg, p=0.75) and placental (83±10 vs 81±4 mg, p=0.80) masses, and similar changes in heart rate (+37±16 vs +39±12 bpm, p=0.93). GD12.5 placentas were then stained with haemotoxylin and eosin or immunostained for cytokeratin-8 to examine morphological changes induced by AVP. AVP infusion had no significant effects on labyrinth (saline n=3, 647±25 vs AVP n=7, 602±35 um, p=0.45), spongiotrophoblast (342±19 vs 363±24 um, p=0.61), or decidua (622±47 vs 520±47 um, p=0.24) layer thicknesses. AVP caused a reduction in average maximum spiral artery diameter (171±28 vs 121±8 um, p<0.05) and a trend toward reduced total spiral artery number (8.4±2.9 vs 4.9±0.7, p=0.13), but no difference in the maximum invasion depth of CK8-positive trophoblasts (310±50 vs 286±37 um, p=0.72). We conclude that AVP infusion is sufficient to induce cardinal mid-gestational features of PE in pregnant mice, including reduced spiral artery diameter. Such morphological changes may be associated with the placental hypoxia and reduced placental growth factor expression in model.

Abstract P261: Vasopressin System Components are Dysregulated in Human Preeclamptic Placenta

Preeclampsia (PE) is a cardiovascular disorder of late pregnancy characterized by pregnancy-specific onset of hypertension and proteinuria. Although initiating events leading to PE development remain unclear, emerging studies suggest arginine vasopressin (AVP) signaling may contribute to PE pathogenesis, as elevated circulating copeptin (a stable biomarker of AVP secretion) levels precede the onset of human PE, and chronic infusion of AVP into wildtype mice phenocopies PE. Here, we tested the hypothesis that AVP signaling is dysregulated in PE placenta by performing in-silico reanalysis of a publically available gene expression dataset derived from placentas of human PE and normal pregnancies (GSE75010). Significant increases in expression [log 2 values] of AVP (Con: 6.96 ± 0.02, PE: 7.03 ± 0.17, p=0.005) and its receptors AVPR1a (Con: 5.73 ± 0.02, PE: 5.80 ± 0.02, p=0.03) and OXTR (Con: 6.58 ± 0.02, PE: 6.65 ± 0.02, p=0.003) were observed in PE placentas (n=80) compared to normal placentas (n=77). Preeclamptic placentas also displayed an enrichment in a hypoxic gene signature, as shown by gene set enrichment analyses (NES: 1.75, FDR q<0.001, FWER p <0.001), suggesting that these placentas exhibited increased hypoxia-related signaling. Interestingly, AVPR1a expression as well as OXTR is positively and significantly correlated with the expression of two hypoxia-inducible genes HK2 and DDIT4 ( AVPR1a v HK2 : r 2 =0.04, p=0.02, AVPR1a v DDIT4 : r 2 =0.06, p=0.003, OXTR v HK2 : r 2 =0.05, p=0.007, OXTR v DDIT4 : r 2 =0.04, p=0.008). To further elucidate the role hypoxia may play in promoting AVP signaling, HTR8/SVNeo cells (immortalized human first trimester trophoblasts) were treated with the hypoxia mimetic dimethyloxallyl glycine (DMOG). DMOG incubation did not significantly alter the expression of AVP and AVPR1a . Unexpectedly, a marked reduction in OXTR expression was observed upon DMOG treatment. In summary, these data suggest that 1) components of the AVP signaling pathway are aberrantly expressed in human PE placentas, 2) PE placentas exhibit a gene expression signature consistent with increased canonical hypoxia signaling, and 3) hypoxia may not be the cause of elevated placental AVP , AVPR1a , and OXTR expression in human PE.

Abstract P270: First Trimester Elevation in Circulating Endothelin-1 and Arterial Stiffness are Predictive of Late Pregnancy Preeclampsia

Preeclampsia (PE) is characterized by late pregnancy hypertension and proteinuria. PE causes significant morbidity for the maternal-fetal unit. Circulating endothelin-1 (ET-1), a potent vasoconstrictor, is elevated at the time of diagnosis of human PE. In addition, women with PE demonstrate arterial stiffness as early as the end of the first trimester. However, it is unknown if arterial stiffness is associated with a first trimester elevation in ET-1 and post-delivery placental ET-1. We hypothesized that 1) first trimester plasma ET-1 is elevated and is associated with arterial stiffness in women who develop PE; 2) first trimester ET-1 is predictive of PE; and 3) placental ET-1 is increased in PE. To address these questions, we performed a nested case-control study in women at risk for PE. First trimester plasma ET-1 was measured via ELISA; aortic stiffness and carotid beta-stiffness (CβS) were measured by carotid-femoral pulse-wave velocity (CFPWV) and carotid tonometry/ultrasound, respectively. While the maternal age of controls (n=126; age 30 ± 0.45 years) and PE (n=15; age 31 ± 1.3 years) were similar, the PE group had a higher first trimester BMI (35 ± 3 vs. 29 ± 1 kg/m 2 , p = 0.01), systolic (125 ± 2 vs. 113 ± 1 mmHg, p< 0.01) and diastolic blood pressure (68 ± 2 vs. 60 ± 1 mmHg, p< 0.01) compared with controls. In addition, first trimester plasma ET-1 (2.7 ± 0.4 vs. 2.0 ± 0.2 pg/mL, p < 0.01), CFPWV (7.2 ± 0.5 vs. 6.1 ± 0.2 m/s, p = 0.016), and CβS (8.4 ± 1.9 vs. 6.3 ± 0.3, p = 0.055) were higher in the PE group. Consistent with previous studies, third trimester plasma ET-1 was elevated in the PE group (2.9 ± 1.1 vs. 1.6 ± 0.1 pg/mL, p < 0.01) which paralleled a 2.5 fold increase in placental decidual ET-1 mRNA (p < 0.0001). ROC analyses showed that first trimester plasma ET-1 (AUC=0.71, p < 0.001) and CFPWV (AUC=0.70, p=0.014) were predictive of PE. This study supports the novel concept that elevated ET-1 in preeclampsia begins early in the first trimester and is associated with premature arterial stiffness. Further, these novel data suggest that ET-1 may play an important role in the first trimester prediction and pathogenesis of preeclampsia.

Abstract P322: Vasopressin Release is Enhanced Before the Development of Preeclampsia in Humans Despite Exaggerated Suppression of Plasma Osmolality

Plasma osmolality (Osm) suppression is of critical importance to maintain appropriate blood volume to perfuse the uterus during pregnancy. Osm is reduced starting at the fifth week of gestation via increased arginine vasopressin (AVP) secretion. This increased secretion is maintained via a decrease in the AVP/osmotic release threshold. We previously demonstrated that pregnant women who develop preeclampsia (PreE) exhibit exaggerated AVP secretion as early as the 6th week of gestation via measurement of copeptin, the stable C-terminal fragment of AVP. It is unclear whether AVP secretion is elevated before the onset of PreE due to osmotic or non-osmotic stimuli. We tested the hypothesis that elevated AVP secretion before PreE may be associated with elevated Osm (a strong stimulant of AVP secretion). Plasma and clinical data from pregnant women were obtained from the University of Iowa Maternal-Fetal Tissue Bank (IRB#200910784). Osm was measured using the freezing-point suppression technique. Osm was assessed in non-pregnant women (n=109), pregnant women who later developed PreE (n=12 for 7-12 weeks, n=9 for 16-24 weeks), and maternal and gestational age matched controls (n=25 for 6-13 weeks, n=15 for 14-27 weeks). As expected, Osm was decreased in control pregnancies (non-pregnant 291±1 vs pregnant 286±1 mOsm/kg, p<0.05). Contrary to our hypothesis, the Osm decrease was exaggerated in women who would later develop PreE (1st trimester: PreE 279±4 vs control 287±3, and 2 nd trimester: PreE 277±4 vs control 285±3 mOsm/kg; effect of PreE p<0.05, gestational age p=NS, interaction p=NS) even after controlling for age, BMI, diabetes, chronic hypertension, history of preeclampsia, and gravida (model p<0.05). Despite suppressed Osm, plasma copeptin was elevated in the PreE group at all timepoints (p<0.05). These data support the conclusion that long before the development of clinical symptoms of PreE, the rate of secretion of AVP is inappropriately increased despite maintenance of normal osmotic-regulating actions of AVP. This effect must be the result of increased non-osmotic stimuli for AVP, and a suppression of the AVP/osmotic release threshold beyond that observed in control pregnancies.

Abstract P177: Reduced Expression of Regulator of G-Protein Signaling-2 (RGS2) in the Placenta During Preeclampsia

Preeclampsia (PE) is a serious cardiovascular condition of late pregnancy. Genetic risk factors and the early-gestational etiology remain largely unclear, though evidence supports excessive activation of Gαq signaling within the placenta in response to various hormones including vasopressin, endothelin, and angiotensin. Regulator of G-protein Signaling 2 (RGS2) acts as an endogenous terminator of Gαq signaling, and previous association studies have identified an increased risk for PE and its sequelae in women carrying a single nucleotide polymorphism that is expected to reduce levels of RGS2. We hypothesized that RGS2 is expressed in placental trophoblasts, and that reduced expression of RGS2 in placental tissue may represent a risk factor for the development of PE. Whole placenta samples and clinical data from preeclamptic and clinically-matched control pregnancies were obtained from the University of Iowa Maternal-Fetal Tissue Bank (IRB#200910784) and examined for mRNA levels of the B/R4 family of RGS proteins, including RGS2. Of the members examined (RGS2, -3, -4.2, -4.3, -4.4, -4.5, and -5) in control placentas (n=9), only RGS2 (Ct 28.8±0.7 vs 18S Ct 12.1±0.4) and RGS4.3 (Ct 23.0±0.4 vs 18S Ct 13.3±0.3) transcripts were expressed above background levels. RGS2 protein expression was then confirmed in human placental tissues by Western blot. RGS2 mRNA expression was 3-fold higher in fetal (amniotic, p<0.05) layers than maternal (decidual) layers. In preeclamptic placenta (n=11), RGS2 may be suppressed (1.0±0.4 vs 0.2±0.3-fold, p=0.1) while RGS4.3 remains unchanged (1.0±0.4 vs 1.1±0.4 fold, p=0.8). Initial immunohistochemical detection confirms cytoplasmic localization of RGS2 in trophoblasts of wildtype mouse placenta, despite exclusive nuclear localization in other tissues. We conclude that human placenta expresses RGS2, and that this expression may be suppressed during preeclampsia. Loss of RGS2 expression may result in disinhibited trophoblast Gαq signaling, and ultimately placental insufficiency.

Abstract P178: Vasopressin Induces Discrete Symptoms of Preeclampsia Through Receptor- and Gestational Age-specific Mechanisms

Preeclampsia (PE) is a common late-gestational disorder characterized by de novo pregnancy specific hypertension, proteinuria, and renal glomerular endotheliosis (RGE). Arginine vasopressin (AVP) secretion (as measured by copeptin) is elevated as early as 6 weeks gestation in pregnancies which later develop PE, and chronic low-dose AVP infusion is sufficient to phenocopy PE in pregnant mice. However, the identity and timeframe of involvement of specific AVP receptors initiating discrete symptoms of PE in this model remain unclear. Wildtype C57BL/6J mice were instrumented with subcutaneous osmotic minipumps to infuse AVP (24 ng/hr) and/or inhibitors during gestation. To clarify the involvement of AVP V 1A and V 2 receptors, one cohort of saline- or AVP-infused pregnant mice was simultaneously infused with the combined V 1A +V 2 antagonist, conivaptan (22 ng/hr). Conivaptan co-treatment ameliorated the hypertension phenotype (SBP on gestational day (GD)15: saline 108.3±2.1, n=24; AVP 120.5±2.1, n=17; conivaptan 112.8±4.1, n=8; AVP+conivaptan 109.8±3.5 mmHg, n=11) but did not prevent proteinuria (on GD17: saline 46.4±6.4, n=15; AVP 79.3±8.5, n=15; conivaptan 64.6±6.7, n=7; AVP+conivaptan 72.9±12.3 mg/mL, n=11) or RGE. To clarify the important timeframes of involvement of AVP for discrete symptoms, subsets of mice were infused with AVP throughout gestation or to only GD10. Continuous infusion of AVP was required to maintain the hypertensive phenotype, as infusion to only GD10 initially elevated blood pressure (SBP at GD10: saline 103.7±1.3, n=26; AVP to GD10 111.5±1.6 mmHg, n=19) but failed to sustain hypertension for the remainder of gestation (SBP at GD15: 112.2±1.3 mmHg, n=19). In contrast, infusion of AVP only to GD10 caused a sustained proteinuria (at GD17: 88.2±9.2 mg/mL, n=19). Infusion of AVP only to GD3 had no effect on any examined endpoint. These data support a specific role for AVP V 1A /V 2 receptors throughout gestation for the hypertension but not proteinuria or RGE phenotypes of PE. Our results therefore indirectly support an early-gestational role for other receptors (perhaps V 1B , cullin-5, or the oxytocin receptor) in the proteinuria and RGE phenotypes of this disorder.

Abstract P321: Differential Leptin Levels are Associated with Hypertensive Disorders of Pregnancy and Adverse Pregnancy Outcomes

During pregnancy, there are normal changes in maternal body weight and blood pressure that occur. Leptin is found in higher levels in obese individuals and has been demonstrated to have an inhibitory effect on myometrial contractility and to regulate blood pressure. Obesity in pregnancy is common and is associated with many complications, including hypertension in pregnancy, failed induction of labor (IOL), and intrauterine growth restriction. Our goal was to determine whether maternal leptin in a pregnant population is indicative of hypertensive disorders in pregnancy, dysfunctional labor, and whether there is a correlation between cord blood leptin and birthweight. We utilized a case control study with samples from the UI Maternal Fetal Tissue Bank (IRB#200910784). In order to analyze labor outcomes, 168 women were selected based on having undergone an IOL, including 54 failed IOL. Maternal/neonatal characteristics were collected from the medical record. Maternal and cord blood plasma leptin and total protein levels were measured using commercially available ELISAs. Bivariate analyses and logistic regression models were constructed using regression identified clinically-significant confounding variables. All variables were tested at significance level of 0.05. Women with hypertensive disorders in pregnancy, including pregnancy-induced hypertension and preeclampsia, had higher maternal leptin levels (14783 vs. 21440 pg/mL, p=0.049). Women with failed IOL also had higher maternal plasma leptin values (0.5 vs 0.3 leptin/protein [pg/ug], P = 0.01). Birthweight was also correlated with cord blood leptin (correlation coefficient 0.494 P < 0.001). These data suggest that maternal and fetal leptin levels are associated with the central mechanisms responsible for poor pregnancy outcomes.

Abstract P323: Arginine Vasopressin and Indoleamine 2,3 Dioxygenase: The Early Immunovascular Interface in Preeclampsia

Preeclampsia (PreE), a hypertensive disease of pregnancy, causes maternal and fetal health complications. Abnormal placental development/angiogenesis and poor immunoregulation (involving T cells, Indoleamine 2, 3 Dioxygenase (IDO), and dendritic cells) are central to the development of PreE. IDO, produced by regulatory immune cells, degrades tryptophan to arrest inflammatory T cell proliferation and induces T regulatory cell development. Our data and others show decreased IDO placental expression from human preeclamptic pregnancies. We published that deletion of IDO (IDO KO) in pregnant mice results in pathognomonic glomerular endotheliosis, proteinuria, and intrauterine growth restriction, hallmark features of PreE. Our group also demonstrated that, plasma copeptin, a stable bio-marker of vasopressin (AVP) secretion, is elevated early in human PreE pregnancies; and AVP infusion into wild-type C57BL/6J dams phenocopies human PreE, including increased inflammatory T cells and highly activated dendritic cells. Here, we test our hypothesis that AVP (via copeptin measurement) is elevated in the IDO KO mouse model of PreE and that IDO activity is decreased in the AVP mouse model of PreE. Copeptin, measured by ELISA, was elevated in both the placenta (2.4±0.2 vs. 1.7±0.2 pg/mg, p=0.03) and maternal serum (2.1±0.2 vs. 1.2±0.4 pg/mg, p=0.03) from IDO KO pregnancies compared to wild-type at gestational day (GD) 18. In our chronic infusion of AVP model of PreE (24 ng/hour), GD 18 colorimetric IDO activity was decreased by 22% in the maternal kidney (N=10 per group) and by 27% in the amniotic fluid (saline N=8 vs. AVP N=12) of AVP-infused dams in comparison to controls. Collectively, these data demonstrate an inverse relationship between IDO activity and copeptin expression in PreE pregnancies. As both IDO and AVP sit at the crossroads between vascular and immune dysfunction, these data suggest that the IDO-AVP interaction may contribute to the maternal and fetal renal phenotype observed in preeclampsia.

Abstract P094: Vasopressin Infusion in Mice During Pregnancy Results in Immune Alterations Consistent with Human Preeclampsia

The immediate and long-term maternal and fetal health complications of preeclampsia (PreE) have been linked to an aberrant T helper immune response and pro-inflammatory cytokine profile. AVP secretion is both stimulated by and stimulates pro-inflammatory cytokine secretion and activation of lymphocytes. Our AVP infusion mouse model of PreE closely replicates human PreE. The objective of this study was to investigate if AVP infusion induces the maternal-fetal immune alterations in PreE.

Immune responses were evaluated in wild-type C57BL/6 female mice chronically infused with AVP (24 ng/hr or saline s.c.) throughout pregnancy. By flow cytometry, we observed an increase in the frequency of IL-17 (1.2% vs. 2.6%, p<0.05), TNFα (0.9% vs. 1.6%, p<0.0001), and IFNγ (1.8% vs. 3.4%, p<0.05) expressing T cells in AVP dams. An increase in the frequency of IL-12 producing cells (1.0% vs. 2.4%, p<0.05) and elevated expression of co-stimulatory molecules on dendritic cells (DCs) from AVP dams suggested enhanced DC function. The maternal plasma revealed a significant reduction in IL-17 (7.1e+6 vs. 3.4e+5 ng/g, p<0.05) and IL-6 (3.4e+5 vs. 0.0 ng/g, p<0.01) production in AVP dams by ELISA as seen in human PreE. Pro-inflammatory TNFα was also significantly decreased in the maternal kidney of AVP dams (2.3e+9 vs. 1.3e+9 ng/g, p<0.05). IL-4 production was significantly reduced in the maternal kidney of AVP dams (5.7e+7 vs. 3.4+7 ng/g, p<0.05) suggesting a blunted Th2 response as seen in human PreE. AVP infusion did not result in alterations of cytokine production in the maternal liver, or fetal liver and kidney. Interestingly, IL-17 production was increased in the amniotic fluid (3.0e+6 vs. 1.3e+7 ng/g, p<0.05) and lower in the placenta (2.5e+7 vs. 1.3e+7 ng/g, p<0.0001) of AVP dams. IL-4 production was decreased in both the amniotic fluid (4.5e+5 vs. 2.0e+5 ng/g, p<0.05) and placenta (3.1e+6 vs. 2.0e+6 ng/g, p<0.05) of AVP dams again suggesting a lower Th2 response.

These data support our hypothesis that AVP induces maternal-fetal immune alterations consistent with human PreE. Ongoing experiments are aimed at identifying the lymphocytes and cytokines involved as well as local vs. systemic immune dysfunction induced by AVP in pregnancy.

Abstract 041: Elevated Circulating Copeptin in Mid-Gestation is Associated with Increased Aortic Stiffness and Vascular Endothelial Dysfunction in Pregnant Women at High Risk for Preeclampsia

Circulating copeptin, a stable biomarker of vasopressin (AVP) secretion, is elevated throughout pregnancy in women who develop preeclampsia (PreE) and is a strong predictor of PreE as early as the 6th week gestation. Reduced vascular endothelial function and increased aortic stiffness occur in mid-gestation before clinical signs/symptoms of PreE manifest, suggesting that maternal vascular dysfunction may be an early event in the pathogenesis of PreE. However, it is unknown whether elevated copeptin/AVP in early/mid gestation contributes to vascular dysfunction in pregnant women who subsequently develop PreE. Therefore, we hypothesized that elevated copeptin would be associated with increased aortic stiffness and reduced vascular endothelial function in early/mid gestation of pregnant women at high risk for PreE. Pregnant women in the 1st trimester (n=72; age=30 ±1 yrs; BMI=34 ± 1 kg/m2) with at least 1 risk factor for PreE were enrolled. Aortic stiffness (carotid-femoral pulse wave velocity, CFPWV), vascular endothelial function (brachial artery flow-mediated dilation, FMD), blood pressure (BP) and plasma copeptin (ELISA) were assessed in both the 1st (11.7 ± 0.2 wks) and 2nd (18.8 ± 0.4 wks) trimesters. In the 1st trimester, CFPWV (7.3 ± 0.2 vs. 7.3 ± 0.5 m/sec, P=0.86), brachial artery FMD (12.9 ± 1.1 vs. 14.3 ± 2.0%, P=0.53), BP, BMI and age did not differ between women in the highest (1513 ± 221 pg/ml) vs. lowest (279 ± 12 pg/ml) quartile of copeptin (P<0.01). In contrast, 2nd trimester CFPWV was greater (7.2 ± 0.2 vs. 6.4 ± 0.2 m/sec, P<0.05) and brachial artery FMD was lower (10.2 ± 2.8 vs. 16.5 ± 1.3 %, P<0.05) among women in the highest (1714 ± 481 pg/ml) vs. the lowest (249 ± 13 pg/ml) quartile of copeptin (P<0.01), in the absence of differences in BP, BMI or age. For the entire cohort, (log)copeptin was significantly correlated with CFPWV (r=0.23, P=0.04) and tended to correlate with FMD (r=-0.23, P=0.06) in the 2nd but not in the 1st trimester. These data suggest that elevated copeptin in mid-gestation is associated with aortic stiffness and vascular endothelial dysfunction in pregnant women at high risk for PreE, but whether increased copeptin/AVP causes vascular dysfunction in pregnancies destined for PreE requires further studies using animal models.

Vasopressin: the missing link for preeclampsia?

Preeclampsia is a devastating cardiovascular disorder of late pregnancy, affecting 5-7% of all pregnancies and claiming the lives of 76,000 mothers and 500,000 children each year. Various lines of evidence support a "tissue rejection" type reaction toward the placenta as the primary initiating event in the development of preeclampsia, followed by a complex interplay among immune, vascular, renal, and angiogenic mechanisms that have been implicated in the pathogenesis of preeclampsia beginning around the end of the first trimester. Critically, it remains unclear what mechanism links the initiating event and these pathogenic mechanisms. We and others have now demonstrated an early and sustained increase in maternal plasma concentrations of copeptin, a protein by-product of arginine vasopressin (AVP) synthesis and release, during preeclampsia. Furthermore, chronic infusion of AVP during pregnancy is sufficient to phenocopy essentially all maternal and fetal symptoms of preeclampsia in mice. As various groups have demonstrated interactions between AVP and immune, renal, and vascular systems in the nonpregnant state, elevations of this hormone are therefore positioned both in time (early pregnancy) and function to contribute to preeclampsia. We therefore posit that AVP represents a missing mechanistic link between initiating events and established midpregnancy dysfunctions that cause preeclampsia.

Pregnant mice lacking indoleamine 2,3-dioxygenase exhibit preeclampsia phenotypes

Preeclampsia is a cardiovascular disorder of late pregnancy that is, commonly characterized by hypertension, renal structural damage and dysfunction, and fetal growth restriction. Prevailing etiologic models of this disorder include T-cell dysfunction as an initiating cause of preeclampsia. Indoleamine 2,3-dioxygenase (IDO), an enzyme that mediates the conversion of tryptophan to kynurenine, has been linked to preeclampsia in humans, and is known to regulate T-cell activity and an endothelial-derived relaxing factor. To test the hypothesis that IDO is causally involved in the pathogenesis of preeclampsia, mice deficient for IDO (IDO-KO) were generated on a C57BL/6 background. IDO-KO and wild-type C57BL/6 mice were bred, and preeclampsia phenotypes were evaluated during pregnancy. Pregnant IDO-KO mice exhibited pathognomonic renal glomerular endotheliosis, proteinuria, pregnancy-specific endothelial dysfunction, intrauterine growth restriction, and mildly elevated blood pressure compared to wild-type mice. Together these findings highlight an important role for IDO in the generation of phenotypes typical of preeclampsia. Loss of IDO function may represent a risk factor for the development of preeclampsia. By extension, increased IDO activity, reductions in IDO reactants, or increases in IDO products may represent novel therapeutic approaches for this disorder.

Abstract 091: Chronic Vasopressin Infusion: A Novel, Clinically Significant, and Pregnancy-Specific Mouse Model of Preeclampsia

Recently we demonstrated that the late-pregnancy cardiovascular disorder, preeclampsia, is characterized by robust, early and sustained vasopressin (AVP) hypersecretion in all three trimesters of pregnancy in humans. We hypothesize a causative role for elevated AVP in the pathogenesis of preeclampsia. This concept was tested by chronically infusing AVP (0.24 - 240 ng/hr, s.c., or saline vehicle) in wildtype C57BL/6J female mice throughout pregnancy. In pregnant mice, AVP infusion caused pregnancy-specific increases in systolic blood pressure by tail-cuff plethysmography with significant increases in the pregnant cohort (saline n=16: 110±3, vs 24 ng/hr AVP n=11: 120±3 mmHg on GD15/16, P<0.05), but no significant difference in the nonpregnant cohort (saline n=14: 108±3, vs 24 ng/hr AVP n=5: 108±5 mmHg, P>0.05). In addition, the AVP infused mice exhibited increased proteinuria (0.24 ng/hr n=2: 66±73, 2.4 ng/hr n=5: 348±56, 24 ng/hr n=2: 799±297 mg/d, P<0.05), intrauterine growth restriction (saline n=25: 0.78±0.06, vs 24 ng/hr n=65: 0.55±0.03 g/fetus, P<0.05), spontaneous feto-placental unit resorption (saline: 0/65=0%, 0.24 ng/hr: 0/16=0%, 2.4 ng/hr: 2/45=4%, 24 ng/hr 8/73=11%, P<0.05), and maternal renal glomerular endotheliosis by electron microscopy. High doses of AVP reduced rates of successful pregnancy with single-night breeding (saline 8/18=44% vs 240 ng/hr 1/20=5%, P<0.05). These data demonstrate that AVP infusion - which simulates the large sustained increases in AVP secretion during human preeclampsia - is sufficient to induce all the cardinal phenotypes of preeclampsia in pregnant C57BL/6J mice. This identifies AVP infusion as a novel, clinically significant, and pregnancy-specific physiological model of preeclampsia in mice. These data support our hypothesis that AVP hypersecretion during pregnancy may be causative for the development of preeclampsia. Ongoing experiments are aimed at identifying the causes of AVP hypersecretion in human preeclampsia, the target tissues and receptors involved, and the utility of targeting AVP signaling as a novel therapeutic for preeclampsia.

Vasopressin in preeclampsia: a novel very early human pregnancy biomarker and clinically relevant mouse model

Preeclampsia, a cardiovascular disorder of late pregnancy, is characterized as a low-renin hypertensive state relative to normotensive pregnancy. Because other nonpregnant low-renin hypertensive disorders often exhibit and are occasionally dependent on elevated arginine vasopressin (AVP) secretion, we hypothesized a possible use for plasma AVP measurements in the prediction of preeclampsia. Copeptin is an inert prosegment of AVP that is secreted in a 1:1 molar ratio and exhibits a substantially longer biological half-life compared with AVP, rendering it a clinically useful biomarker of AVP secretion. Copeptin was measured throughout pregnancy in maternal plasma from preeclamptic and control women. Maternal plasma copeptin was significantly higher throughout preeclamptic pregnancies versus control pregnancies. While controlling for clinically significant confounders (age, body mass index, chronic essential hypertension, twin gestation, diabetes mellitus, and history of preeclampsia) using multivariate regression, the association of higher copeptin concentration and the development of preeclampsia remained significant. Receiver operating characteristic analyses reveal that as early as the sixth week of gestation, elevated maternal plasma copeptin concentration is a highly significant predictor of preeclampsia throughout pregnancy. Finally, chronic infusion of AVP during pregnancy (24 ng per hour) is sufficient to phenocopy preeclampsia in C57BL/6J mice, causing pregnancy-specific hypertension, renal glomerular endotheliosis, proteinuria, and intrauterine growth restriction. These data implicate AVP release as a novel predictive biomarker for preeclampsia very early in pregnancy, identify chronic AVP infusion as a novel and clinically relevant model of preeclampsia in mice, and are consistent with a potential causative role for AVP in preeclampsia in humans.

Characterization of regulatory dendritic cells that mitigate acute graft-versus-host disease in older mice following allogeneic bone marrow transplantation

Despite improvements in human leukocyte antigen matching and pharmacologic prophylaxis, acute graft-versus-host disease (GVHD) is often a fatal complication following hematopoietic stem cell transplant (HSCT). Older HSCT recipients experience significantly increased morbidity and mortality compared to young recipients. Prophylaxis with syngeneic regulatory dendritic cells (DCreg) in young bone marrow transplanted (BMT) mice has been shown to decrease GVHD-associated mortality. To evaluate this approach in older BMT recipients, young (3–4 months) and older (14–18 months) DCreg were generated using GM-CSF, IL-10, and TGFβ. Analysis of young versus older DCreg following culture revealed no differences in phenotype. The efficacy of DCreg treatment in older BMT mice was evaluated in a BALB/c→C57Bl/6 model of GVHD; on day 2 post-BMT (d +2), mice received syngeneic, age-matched DCreg. Although older DCreg-treated BMT mice showed decreased morbidity and mortality compared to untreated BMT mice (all of which died), there was a small but significant decrease in the survival of older DCreg-treated BMT mice (75% survival) compared to young DCreg-treated BMT mice (90% survival). To investigate differences between dendritic cells (DC) in young and older DCreg-treated BMT mice that may play a role in DCreg function in vivo, DC phenotypes were assessed following DCreg adoptive transfer. Transferred DCreg identified in older DCreg-treated BMT mice at d +3 showed significantly lower expression of PD-L1 and PIR B compared to DCreg from young DCreg-treated BMT mice. In addition, donor DC identified in d +21 DCreg-treated BMT mice displayed increased inhibitory molecule and decreased co-stimulatory molecule expression compared to d +3, suggesting induction of a regulatory phenotype on the donor DC. In conclusion, these data indicate DCreg treatment is effective in the modulation of GVHD in older BMT recipients and provide evidence for inhibitory pathways that DCreg and donor DC may utilize to induce and maintain tolerance to GVHD.