OS061. Placental growth factor reduces blood pressure and proteinuria in experimental preeclampsia.

INTRODUCTION: Preeclampsia is a disorder related to an imbalance in the angiogenesis axis manifesting as endothelial dysfunction. Animal and human studies have shown that sFLT-1 (soluble fms like tyrosine kinase 1) is increased and PlGF (placental growth factor) reduced during the disease state. There are a paucity of studies investigating the clinical significance of normalising angiogenic axis. OBJECTIVES: To use a non-human primate uteroplacental ischemic (UPI) model of preeclampsia to assess if reversing the angiogenic imbalance, by increasing circulating PlGF, is able to ameliorate the hypertension and proteinuria. METHODS: Hypertensive proteinuria was induced in a non-human primate (Papio hamadryas) by ligation of a unilateral uterine artery at 130days of an 182day pregnancy. After two weeks of UPI, PlGF was administered by subcutaneous injection (100mg/kg/day) for 5 days (n=3) or normal saline in an equivalent volume (n=3). Blood pressure was monitored via intra-arterial radiotelemetry, sFLT-1 measured via ELISA and spot urinary protein:creatinine ratios were measured to monitor proteinuria. Data was analysed using SPSS by t-tests and analysis of repeated measures. Significance was set at p<0.05 and data expressed as the mean ±SEM. RESULTS: After two weeks of UPI both groups demonstrated a significant elevation in blood pressure, proteinuria (p<0.05) and sFLT-1 (p<0.001). The systolic BP increased by 12.4±2.3mmHg and 11.7±2.9mmHg in the PlGF and control groups respectively compared to baseline (p<0.005). After PlGF administration, there was a significant reduction in blood pressure in the treated group (-5.2s±0.8mmHg) compared to the increase in BP in the control group (+6.5±3mmHg). Proteinuria also reduced in the treated group from 112±51mg/mmol to 38±12mg/mmol whilst proteinuria in the control group was unchanged. The total circulating sFLT-1 was not significantly affected by the administration of PlGF after 5days. Although this study was not designed to assess fetal safety or outcomes, there was no adverse fetal outcome attributable to the administration of the PlGF. CONCLUSION: Administration of PlGF resulted in a reduction in BP and proteinuria without significantly affecting total sFLT-1 levels. Correcting the angiogenic axis imbalance may improve the clinical parameters in a non-human primate animal model of preeclampsia.

OS067. VEGF, a novel stimulator of aldosterone production.

INTRODUCTION: Adrenal aldosterone production depends upon capillary integrity. Inadequately explained by increased renin secretion, aldosterone is high in pregnancy, a proangiogenic state. In preeclampsia, low aldosterone levels coincide with disturbed endothelial integrity due to disrupted VEGF signaling. OBJECTIVES: We hypothesized that the stimulation of adrenal aldosterone production is VEGF-sensitive. METHODS: We cultured endothelial cells (EC) in the presence and absence of VEGF. The supernatent was transferred to cultured adrenal cells, either the cell line H295R or isolated primary human adrenal cells from zona glomerulosa. aldosterone synthase mRNA and protein expression, aldosterone synthesis was assessed by adding radioactive labeled precursors or measuring aldosterone in the supernatent by Elisa. Cells were cultured either with angiotensin II (Ang II), VEGF or a combination hereof. Adenovirus-based overexpression of the soluble VEGF receptor type 1 (sFlt-1) was used to simulated conditions of preeclampsia in rats and its effect on the adrenocortical vasculature and circulating aldosterone levels. RESULTS: EC conditioning in the presence of VEGF enhanced aldosterone synthase activity in human adrenocortical cells. VEGF either alone or combined with Ang II increased aldosterone synthase transcription, enzyme availability and aldosterone production in adrenal cells. Neuropilin-1 and VEGF receptor expression differed only for Flt-1 which was present in ECs but not in adrenocortical cells. In contrast to Ang II, VEGF did not upregulate the steroidogenic acute regulatory protein. In line with this observation, Ang II stimulated both aldosterone and cortisol synthesis from progesterone whereas VEGF preferably the former. In rats, overexpression of sFlt-1 which traps VEGF led to adrenocortical capillary rarefaction. Serum aldosterone concentrations inversely correlated with sFlt-1 levels. CONCLUSION: In conclusion, VEGF stimulates aldosterone production indirectly via ECs and directlyin adrenocortical cells a finding explaining the increased aldosterone/renin ratio in normal pregnancy. It is reasonable to assume that the inappropriately low aldosterone availability in preeclampsia is a consequence of the known disturbed VEGF signaling.

PP016. Circulating lymphangiogenic factors in preeclampsia.

INTRODUCTION: Preeclampsia, a human pregnancy specific disorder is characterized by an anti-angiogenic state due to high levels of circulating soluble vascular endothelial growth factor 1 (sVEGFR1). However, the role of lymphangiogenesis in preeclampsia has not been investigated. Recently, impaired VEGF-C (factor that regulates lymphangiogenesis) signalling has been implicated in the pathogenesis of interstitial edema and salt-sensitive hypertension. OBJECTIVES: Therefore, we hypothesized that circulating VEGF-C and its circulating receptors (sVEGFR2 and sVEGFR3) may also be altered in preeclampsia and correlate with the severity of the phenotype. METHODS: We analyzed plasma levels of VEGF-C, sVEGFR1, sVEGFR2 and sVEGFR3 in women with gestational hypertension (GHTN, n=20), preeclampsia (PE, n=20) and normotensive pregnancies (NP, n=20) in the third trimester and values reported as mean±SD in pg/ml. RESULTS: As previously reported, sVEGFR1 levels were significantly higher in subjects with PE (19938 ± 12973) than in GHTN (7156±5432), p<0.01 or NP (7760±6018), p<0.01. VEGF-C levels were lower in subjects with GHTN (676±323) than in PE (1335±625), p<0.01, but not statistically different than in NP (971±556), p=0.11. There was a trend towards lower sVEGFR-2 in PE as compared to GHTN or NP. Interestingly sVEGFR-3 was significantly lower in PE (54,371±21,107) as compared to NP (83,709±24,983), p<0.01, but not different as compared to GHTN (54,642±26,947). The ratio of sVEGFR-2+sVEGFR-3/VEGF-C was dramatically lower during PE (57±38) as compared to GHTN (113±72), p<0.01 or NP (133±91), p<0.01. CONCLUSION: Preeclampsia is characterized by circulating pro-lymphangiogenic state as evidenced by decreased sVEGFR-3, slightly decreased VEGFR-2, increased VEGF-C and a dramatically lower ratio of sVEGFR2+sVEGFR3/VEGF-C. Our data suggests that the circulating pro-lymphoangiogenic state during preeclampsia may be a compensatory response to edema and hypertension. Additional studies are needed to evaluate the clinical relevance of the altered lymphangiogenic signalling pathway during preeclampsia.