In Vivo Experiments Reveal the Good, the Bad and the Ugly Faces of sFlt-1 in Pregnancy

Abstract

ObjectiveSoluble fms-like tyrosine kinase (sFlt)-1-e15a, a primate-specific sFlt-1-isoform most abundant in the human placenta in preeclampsia, can induce preeclampsia in mice. This study compared the effects of full-length human (h)sFlt-1-e15a with those of truncated mouse (m)sFlt-1(1-3) used in previous preeclampsia studies on pregnancy outcome and clinical symptoms in preeclampsia.MethodsMice were injected with adenoviruses or fiber-mutant adenoviruses overexpressing hsFlt-1-e15a, msFlt-1(1-3) or control GFP under the CMV or CYP19A1 promoters on gestational day 8 (GD8) and GD11. Placentas and pups were delivered by cesarean section, and dams were monitored postpartum. Blood pressure was telemetrically recorded. Urine samples were collected with cystocentesis and examined for albumin/creatinine ratios. Tissue specimens were evaluated for transgene as well as endogenous mFlt-1 and msFlt-1-i13 expression. H&E-, Jones- and PAS-stained kidney sections were histopathologically examined. Placental GFP expression and aortic ring assays were investigated with confocal microscopy.ResultsMean arterial blood pressure (MAP) was elevated before delivery in hsFlt-1-e15a-treated mice compared to controls (GD18: ΔMAP = 7.8 mmHg, p = 0.009), while ΔMAP was 12.8 mmHg (GD18, p = 0.005) in msFlt-1(1-3)-treated mice. Urine albumin/creatinine ratio was higher in hsFlt-1-e15a-treated mice than in controls (GD18, p = 0.04; PPD8, p = 0.03), and msFlt-1(1-3)-treated mice had marked proteinuria postpartum (PPD8, p = 4×10−5). Focal glomerular changes were detected in hsFlt-1-e15a and msFlt-1(1-3)-treated mice. Aortic ring microvessel outgrowth was decreased in hsFlt-1-e15a (p = 0.007) and msFlt-1(1-3)-treated (p = 0.02) mice. Full-length msFlt-1-i13 expression was unique for the placenta. In hsFlt-1-e15a-treated mice, the number of pups (p = 0.046), total weight of living pups (p = 0.04) and maternal weights (p = 0.04) were higher than in controls. These differences were not observed in truncated msFlt-1(1-3)-treated mice.ConclusionsTruncated msFlt-1(1-3) simulated the preeclampsia-promoting effects of full-length hsFlt-1. MsFlt-1(1-3) had strong effect on maternal endothelium but not on placentas and embryos. In contrast, hsFlt-1-e15a induced preeclampsia-like symptoms; however, it also increased litter size. In accord with the predominant placental expression of hsFlt-1-e15a and msFlt-1-i13, full-length sFlt-1 may have a role in the regulation of embryonic development. These observations point to the difference in the biological effects of full-length and truncated sFlt-1 and the changes in the effect of full-length sFlt-1 during pregnancy, and may have important implications in the management of preeclampsia.

Exposure to Experimental Preeclampsia in Mice Enhances the Vascular Response to Future Injury

“…A second group of mice (N=3 Control, N=5 experimental PE) had telemetry devices inserted prior to pregnancy exclusively to confirm the PE phenotype. In this subset of mice, overexpression of sFlt1 was associated with the characteristics of PE including significantly elevated systolic blood pressure and characteristic renal pathology in late gestation in the PE group similar to what has been described by other groups (Figure S1)(12;15;16;26;27). …”

“…High sFlt-1 levels produce endothelial dysfunction which contributes to abnormal vascular tone and hypertension, increased glomerular vascular permeability leading to proteinuria, and consumptive coagulopathy(13). When injected into pregnant rodents, sFlt-1 reproduces systemic endothelial dysfunction resulting in a syndrome that phenocopies human PE, supporting the concept that sFlt-1 is a pathogenic mediator of PE(12;14–16). …”

“…Female CD1 mice were randomized to receive either sFlt-1 adenovirus or CMV-null virus at gestational day (GD)9 of pregnancy resulting in hypertension, proteinuria and glomerular endothelial damage resembling human PE as previously described(12;15;16;26;27). …”

Longitudinal Changes in Placental Magnetic Resonance Imaging Relaxation Parameter in Murine Pregnancy: Compartmental Analysis

“…Animal care and handling followed the standards set forth by the National Research Council of the National Academies [43] and those published in our previous study [44]. Timed-pregnant CD-1 mice (n=9) were obtained from Charles River Laboratories (Wilmington, MA, USA).…”

Activation of Villous Trophoblastic p38 and ERK1/2 Signaling Pathways in Preterm Preeclampsia and HELLP Syndrome

“…The release of toxic placental substances and the decreased availability of pro-angiogenic molecules [e.g. placenta growth factor (PGF)] then promotes the terminal pathway of preeclampsia, including maternal systemic anti-angiogenic and pro-inflammatory states, generalized endothelial dysfunction, leukocyte activation, hypertension and proteinuria [4, 15, 17, 18, 20, 24–28]. Although placental histopathological and transcriptomic changes are less prevalent in late-onset preeclampsia [4–6], it has recently been suggested that normal placental growth may also induce syncytiotrophoblastic stress and increased production of sFlt-1 late in pregnancy, promoting the progression of the terminal pathway [29].…”