S-glutathionylation, a redox switch disrupting angiogenic balance to promote the preeclampsia phenotype

Background Elevation of circulating anti-angiogenic factors is pivotal in the development of the preeclampsia (PE) phenotype of incomplete vascular remodelling, hypertension and kidney dysfunction during pregnancy. Oxidative stress is explicitly linked to PE with high levels measurable in the placenta. Yet antioxidant therapy has failed, in some cases worsening pregnancy outcomes. The modulation of protein activity by reversible oxidative post-translational modifications (oxPTM) under low levels of reactive oxygen species is emerging as an important “redox-switch” mechanism in cardiovascular diseases, although oxPTM have not been investigated in the context of PE. Of significance, S-glutathionylation is a common oxPTM which reversal by glutaredoxin (Grx) is predominant in preeclamptic placenta and was associated with attenuated revascularisation and sFlt-1 elevation in mice. Purpose We aimed to identify the molecular basis for how S-glutathionylation reversal by Grx may contribute to pregnancy-induced vascular complications by modulating angiogenic signalling at the maternofoetal interface. Methods We combined physiological in vivo assessment with bioinformatics proteomic analysis and exon-level microarray to investigate the role of S-glutathionylation in the development of PE phenotype. In vitro studies using primary endothelial cells (EC) and iPS-derived trophoblasts investigated the effects of oxPTM reversal on angiogenic signalling in individual placental cell types and the functional consequences were assessed in 3D models replicating early-pregnancy events. Results Overexpressing Grx transgenic mice (TG) developed gestational hypertension, kidney dysfunction and elevated plasma levels of the anti-angiogenic factor sFlt-1 compared to their littermate controls (WT) during timed pregnancy. Grx-mediated oxPTM reversal in EC disrupted angiogenic sprouting and promoted anti-angiogenic signals by increasing sFlt-1:PlGF ratio and decreasing endoglin levels. The rise in sFlt-1 was associated with an isoform switch promoting sFlt-e15a over sFlt-i13. In trophoblasts, Grx overexpression inhibited migration and syncytialisation and modulated angiogenic balance in a cell type-specific manner. The sFlt1-e15a:PlGF ratio was increased in syncytiotrophoblasts and decreased in extra-villous trophoblasts, while endoglin expression was decreased in both cell types. A genome-wide exon-level profiling of TG vs WT mice placenta revealed a global alteration of alternative splicing events. Conclusion Grx-mediated removal of oxPTM directly disrupts placental angiogenic balance via dysregulation of sFlt-1 isoforms, which may promote the PE phenotype of impaired vascular remodelling, hypertension and kidney dysfunction during pregnancy. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020 - Marie Skłodowska-Curie grant agreement (iPLACENTA)

Protease nexin-1 deficiency increases mouse hindlimb neovascularisation following ischemia and accelerates femoral artery perfusion

We previously identified the inhibitory serpin protease nexin-1 (PN-1) as an important player of the angiogenic balance with anti-angiogenic activity in physiological conditions. In the present study, we aimed to determine the role of PN-1 on pathological angiogenesis and particularly in response to ischemia, in the mouse model induced by femoral artery ligation. In wild-type (WT) muscle, we observed an upregulation of PN-1 mRNA and protein after ischemia. Angiography analysis showed that femoral artery perfusion was more rapidly restored in PN-1−/− mice than in WT mice. Moreover, immunohistochemistry showed that capillary density increased following ischemia to a greater extent in PN-1−/− than in WT muscles. Moreover, leukocyte recruitment and IL-6 and MCP-1 levels were also increased in PN-1−/− mice compared to WT after ischemia. This increase was accompanied by a higher overexpression of the growth factor midkine, known to promote leukocyte trafficking and to modulate expression of proinflammatory cytokines. Our results thus suggest that the higher expression of midkine observed in PN-1- deficient mice can increase leukocyte recruitment in response to higher levels of MCP-1, finally driving neoangiogenesis. Thus, PN-1 can limit neovascularisation in pathological conditions, including post-ischemic reperfusion of the lower limbs.

Affinity-Enhanced Multimeric VEGF (Vascular Endothelial Growth Factor) and PlGF (Placental Growth Factor) Variants for Specific Adsorption of sFlt-1 to Restore Angiogenic Balance in Preeclampsia

Preeclampsia is a potentially life-threatening multisystem disease affecting 4% to 8% of pregnant women after the 20th week of gestation. An excess of placental expressed antiangiogenic soluble VEGF (vascular endothelial growth factor)-receptor 1 (soluble FMS-like tyrosine kinase 1) scavenges VEGF and PlGF (placental growth factor), causing generalized endothelial dysfunction. Interventions to restore the angiogenic balance in preeclamptic pregnancies are intensively studied and improve maternal and neonatal outcomes. Especially extracorporeal strategies to remove sFlt-1 are promising in human pregnancy. However, available apheresis systems adsorb sFlt-1 unspecifically and with low efficiency. Affinity-enhanced ligands are needed to improve performance and compatibility of apheresis treatments. Using computerized molecular modeling, we developed multimeric VEGF molecules comprised of single-chain VEGF 165 dimers (scVEGF 165 ). A short peptide linker hampers intrachain dimerization to induce assembly preferably as tetrameric molecules as visualized in negative staining electron microscopy. scVEGF 165 multimers possess 1.2-fold higher affinity for sFlt-1 as compared to the available antibodies or monomeric VEGF. Consequently, scVEGF multimers have the ability to competitively release sFlt-1 bound PlGF and, in particular, VEGF. In ex vivo adsorption experiments using serum samples from patients with preeclampsia, scVEGF multimers reduce sFlt-1 levels by 85% and increase PlGF and VEGF levels by 20- and 9-fold, respectively. Finally, performance and stability of sFlt-1 capturing scVEGF 165 multimers were scrutinized on different matrices of which biocompatible agarose matrix yielded optimal results. We introduce the first VEGF-based highly efficient sFlt-1 apheresis system that is directly applicable in vivo due to utilization of inert agarose matrix, using a homomultimeric form of VEGF 165 to restore the angiogenic balance in preeclampsia.

Prenatal vitamin D supplementation reduces blood pressure and improves placental angiogenesis in an animal model of preeclampsia

The study demonstrates that prenatal vitamin D supplementation reduces blood pressure and restores angiogenic balance in an animal model of preeclampsia.

Trophoblast paracrine signaling regulates placental hematoendothelial niche

The placenta acts as a major organ for hematopoiesis. It is believed that placental hematopoietic stem and progenitor cells (HSPCs) migrate to the fetal liver to ensure optimum hematopoiesis in the developing embryo. The labyrinth vasculature in a mid-gestation mouse placenta provides a niche for the definitive hematopoietic stem cell (HSC) generation and expansion. It has been proposed that these processes are regulated by a host of paracrine factors secreted by trophoblast giant cells (TGCs) at the maternal-fetal interface. However, the molecular mechanism by which the TGCs regulate the hematoendothelial niche in a developing placenta is yet to be defined. Using a TGC-specific Gata2 and Gata3 double knockout mouse model, we show that the loss of GATA2 and GATA3 at the TGC layer leads to fetal growth retardation and embryonic death due to disruptions in the delicate hematopoietic-angiogenic balance in the developing placenta. Using single-cell RNA-Seq analyses, we also show that the loss of GATA factors in the TGCs results in the loss of HSC population within the placental labyrinth and is associated with defective placental angiogenesis. Interestingly, we also found that this TGC-specific GATA factor-loss leads to impaired differentiation and distribution of trophoblast progenitor cells. Our study helps to define the GATA-dependent non-autonomous signaling mechanisms of the primary parietal trophoblast giant cells by which it regulates the delicate hematopoietic-angiogenic balance in the developing placenta.