MT-MMPs in pre-eclamptic placenta: relationship to soluble endoglin production

Transthyretin binds soluble endoglin and increases its uptake by hepatocytes: A possible role for transthyretin in preeclampsia?

BACKGROUND

Preeclampsia is a common but life-threatening condition of pregnancy. It is caused by poor placentation resulting in release of trophoblast material (including soluble endoglin (sEng)) into the maternal circulation leading to maternal vascular dysfunction and to the life-threatening condition of eclampsia. The only cure is early delivery, which can have lifelong consequences for the premature child. The thyroid hormone binding protein transthyretin is dysregulated in preeclampsia, however it is not known if this plays a role in disease pathology. We hypothesised that transthyretin may bind sEng and abrogate its negative effects by removing it from the maternal serum.

METHODS

The effect of transthyretin on hepatocyte uptake of Alexa-labelled sEng was measured using live cell imaging. Interactions between transthyretin, and sEng were investigated using molecular modelling, direct binding on CnBr Sepharose columns, confocal imaging, and measurement of fluorescence resonance energy transfer.

RESULTS

Transthyretin directly bound to sEng and increased its uptake by hepatocytes. This uptake was altered in the presence of transforming growth factor-β1 (TGF-β1). Molecular modelling predicted that transthyretin and TGF-β1 bind at the same site in sEng and may compete for binding. Endocytosed transthyretin and endoglin entered cells together and co-localised inside hepatocyte cells.

CONCLUSION

Transthyretin can bind sEng and increase its uptake from the extracellular medium. This suggests that increasing transthyretin levels or developing drugs that normalise or mimic transthyretin, may provide treatment options to reduce sEng induced vascular dysfunction.

Placental Therapeutic Targets and Nanodelivery Systems

Pregnancy complications affect millions of women each year. Some of these diseases have high morbidity and mortality such as preeclampsia. At present, there is no safe and effective treatment for pregnancy complications, so it is still a difficult clinical problem. As many pregnancy complications are closely related to placental dysplasia, placenta-specific therapy, as an important method, is expected to be a safe, effective, and specific therapeutic strategy. This review explains in detail the placenta physiological structure, characteristics, and action mechanism of some biomolecules and signaling pathways that play roles in normal development and disorders of the development of the placenta, and how to use these biomolecules as therapeutic targets when the placenta disorder causes disease, combining the latest progress in the field of nanodelivery systems, so as to lay a foundation for the development of placenta-specific therapy of pregnancy complications.

Analyses of soluble endoglin and matrix metalloproteinase 14 using enzyme-linked immunosorbent assay in the diagnosis and assessment of severity of early- and late-onset pre-eclampsia

Objective

Abnormal trophoblastic invasion and impaired placentation have a crucial role in the etiopathogenesis of preeclampsia (PrE). Trophoblastic cells are involved in invading the maternal decidua and remodelling of the spiral arteries with matrix metalloproteinase-14 (MMP-14). MMP-14 cleavage of endoglin releases its extracellular region, the soluble form of endoglin (s-ENG), into the maternal circulation. In PrE, there is a relationship between endothelial dysfunction and s-ENG concentration. The aim was to determine and compare the serum levels of s-ENG and MMP-14 in different groups of PrE patients and healthy subjects.

Material and Methods

The study included 30 patients with late-onset preeclampsia (L-PrE) (group 1; gestational age ≥34 weeks), 33 patients with normal pregnancy (group 2; gestational age ≥34 weeks), 31 patients early-onset preeclampsia (E-PrE) (group 3; gestational age <34 weeks), and 31 patients with normal pregnancy (group 4; gestational age <34 weeks). s-ENG and MMP-14 concentrations measured using enzyme-linked immunosorbent assays were compared.

Results

In all groups, MMP-14 concentrations decreased with increasing gestational age. s-ENG concentrations were highest in the E-PrE group. In groups 1 and 3, 29 had mild PrE while 32 suffered severe PrE and s-ENG concentrations did not differ between mild and severe preeclampsia (p=0.133). However, there was a significant difference in MMP-14 concentration comparing mild with severe PrE (3.11±0.61 vs 3.54±1.00; p=0.047, respectively). There was no correlation between s-ENG and MMP-14 concentrations.

Conclusion

MMP-14 and s-ENG concentrations can be predictive biomarkers for the diagnosis of PrE. Maternal serum MMP-14 concentration may be a biomarker for determining the severity of PrE.

Pregnancy-Induced High Plasma Levels of Soluble Endoglin in Mice Lead to Preeclampsia Symptoms and Placental Abnormalities

Preeclampsia is a pregnancy-specific disease of high prevalence characterized by the onset of hypertension, among other maternal or fetal signs. Its etiopathogenesis remains elusive, but it is widely accepted that abnormal placentation results in the release of soluble factors that cause the clinical manifestations of the disease. An increased level of soluble endoglin (sEng) in plasma has been proposed to be an early diagnostic and prognostic biomarker of this disease. A pathogenic function of sEng involving hypertension has also been reported in several animal models with high levels of plasma sEng not directly dependent on pregnancy. The aim of this work was to study the functional effect of high plasma levels of sEng in the pathophysiology of preeclampsia in a model of pregnant mice, in which the levels of sEng in the maternal blood during pregnancy replicate the conditions of human preeclampsia. Our results show that wild type pregnant mice carrying human sEng-expressing transgenic fetuses (fWT(hsEng⁺)) present high plasma levels of sEng with a timing profile similar to that of human preeclampsia. High plasma levels of human sEng (hsEng) are associated with hypertension, proteinuria, fetal growth restriction, and the release of soluble factors to maternal plasma. In addition, fWT(hsEng⁺) mice also present placental alterations comparable to those caused by the poor remodeling of the spiral arteries characteristic of preeclampsia. In vitro and ex vivo experiments, performed in a human trophoblast cell line and human placental explants, show that sEng interferes with trophoblast invasion and the associated pseudovasculogenesis, a process by which cytotrophoblasts switch from an epithelial to an endothelial phenotype, both events being related to remodeling of the spiral arteries. Our findings provide a novel and useful animal model for future research in preeclampsia and reveal a much more relevant role of sEng in preeclampsia than initially proposed.

A Single Sphingomyelin Species Promotes Exosomal Release of Endoglin into the Maternal Circulation in Preeclampsia

Preeclampsia (PE), an hypertensive disorder of pregnancy, exhibits increased circulating levels of a short form of the auxillary TGF-beta (TGFB) receptor endoglin (sENG). Until now, its release and functionality in PE remains poorly understood. Here we show that ENG selectively interacts with sphingomyelin(SM)-18:0 which promotes its clustering with metalloproteinase 14 (MMP14) in SM-18:0 enriched lipid rafts of the apical syncytial membranes from PE placenta where ENG is cleaved by MMP14 into sENG. The SM-18:0 enriched lipid rafts also contain type 1 and 2 TGFB receptors (TGFBR1 and TGFBR2), but not soluble fms-like tyrosine kinase 1 (sFLT1), another protein secreted in excess in the circulation of women with PE. The truncated ENG is then released into the maternal circulation via SM-18:0 enriched exosomes together with TGFBR1 and 2. Such an exosomal TGFB receptor complex could be functionally active and block the vascular effects of TGFB in the circulation of PE women.

Soluble Fms-Like Tyrosine Kinase 1 (sFlt-1) and Risk of Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The molecular mechanisms underlying cerebral vasospasm and delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH) are incompletely understood. We hypothesized that circulating antiangiogenic factors, such as soluble Fms-like tyrosine kinase 1 (sFlt-1) and soluble transforming growth factor β coreceptor, soluble endoglin (sEng), are important markers of their pathophysiology.

METHODS

We performed a prospective study in patients with aSAH and measured cerebrospinal fluid and serum levels of sFlt-1 and sEng on postbleed day 1 and 6 and correlated levels with incidence and severity of cerebral vasospasm and DCI.

RESULTS

Twenty-seven patients with aSAH were enrolled in the study. Severe angiographic vasospasm was present in 14.8% of patients and DCI occurred in 33.3%. Serum sFlt1 levels were increased on postbleed day 6 in patients who developed vasospasm. However, on postbleed day 1, there were no differences in patients who developed vasospasm. Increased serum sFlt-1 levels on postbleed day 1 were found to predict the development of severe angiographic vasospasm with an area under the curve of 0.818 with an optimal cutoff value of 95 pg/mL. Alterations in sFlt1 were not associated with DCI. Serum and cerebrospinal fluid sEng levels did not correlate with vasospasm or DCI.

CONCLUSIONS

Serum levels of sFlt-1 are increased in patients with aSAH who are at risk for severe vasospasm. Further studies with larger sample sizes are needed to evaluate whether sFlt-1 levels may predict onset of severe vasospasm and DCI.

New Insights into the Role of Matrix Metalloproteinases in Preeclampsia

Preeclampsia is a severe pregnancy complication globally, characterized by poor placentation triggering vascular dysfunction. Matrix metalloproteinases (MMPs) exhibit proteolytic activity implicated in the efficiency of trophoblast invasion to the uterine wall, and a dysregulation of these enzymes has been linked to preeclampsia. A decrease in MMP-2 and MMP-9 interferes with the normal remodeling of spiral arteries at early pregnancy stages, leading to the initial pathophysiological changes observed in preeclampsia. Later in pregnancy, an elevation in MMP-2 and MMP-9 induces abnormal release of vasoactive factors conditioning hypertension. Although these two enzymes lead the scene, other MMPs like MMP-1 and MMP-14 seem to have a role in this pathology. This review gathers published recent evidence about the implications of different MMPs in preeclampsia, and the potential use of these enzymes as emergent biomarkers and biological therapeutic targets, focusing on studies involving human subjects.

Placental membrane-type metalloproteinases (MT-MMPs): Key players in pregnancy

Membrane-type matrix metalloproteinases (MT-MMPs) are a sub-family of zinc-dependent endopeptidases involved in the degradation of the extracellular matrix. Although MT-MMPs have been mainly characterized in tumor biology, they also play a relevant role during pregnancy. Placental MT-MMPs are required for cytotrophoblast migration and invasion of the uterine wall and in the remodeling of the spiral arteries. They are involved in the fusion of cytotrophoblasts to form the syncytiotrophoblast as well as in angiogenesis. All these processes are crucial for establishing and maintaining a successful pregnancy and, thus, MT-MMP activity has to be tightly regulated in time and space. Indeed, a de-regulation of MT-MMP expression has been linked with pregnancy complications such as preeclampsia (PE), fetal growth restriction (FGR), gestational diabetes mellitus (GDM) and was also found in maternal obesity. Here we review what is currently known about MT-MMPs in the placenta, with a focus on their general features, their localization and their involvement in pregnancy disorders.

A wash step at collection of placental biopsies from preeclamptic pregnancies does not adversely affect levels of sFlt-1 or endoglin

There is recent interest for uniform placental collection protocols so laboratories can share samples. However, concerns have been raised a wash step at collection causes significant loss of sFlt-1 and soluble endoglin, among the most studied proteins in placentology. We measured Flt-1 and endoglin mRNA and protein in 10 preeclamptic placentas that were washed, or left unwashed. Reassuringly, there was no significant change in the Flt-1, sFlt-1-e15a or sFlt-1-i13 mRNA or Flt-1 or sFlt-1 protein expression or localization. There was also no change in endoglin mRNA expression or protein localization. Washing preeclamptic placental samples does not alter anti-angiogenic factor expression.

Comparative proteome profile of human placenta from normal and preeclamptic pregnancies

To better understand the molecular mechanisms involved in pathological development of placenta in preeclampsia, we used LC-MS/MS to construct a large-scale comparative proteome profile of human placentas from normal and preeclamptic pregnancies. A total of 2636 proteins were detected in human placentas, and 171 different proteins were definitively identified between control and preeclamptic placentas. Further bioinformatics analysis indicated that these differentially expressed proteins correlate with several specific cellular processes which occur during pathological changes of preeclamptic placenta. 6 proteins were randomly selected to verify their expression patterns with Western blotting. Of which, 3 proteins’ cellular localizations were validated with immunohistochemistry. Elucidation of how protein-expression changes coordinate the pathological development would provide researchers with a better understanding of the critical biological processes of preeclampsia and potential targets for therapeutic agents to regulate placenta function, and eventually benefit the treatment of preeclampsia.