The Role of Syncytin in Placental Angiogenesis and Fetal Growth

HSD17B1-mediated trophoblast differentiation lowers estrogen levels in early-onset preeclampsia

Early-onset preeclampsia (EOPE) with fetal growth restriction (FGR) is a severe hypertensive disorder of pregnancy characterized by placental dysfunction and estrogen deficiency. Based on single-cell RNA sequencing (scRNA-seq) profiling of specific placental trophoblast subtypes from EOPE-FGR and normotensive pregnancies, we identified HSD17B1, which encodes a key enzyme mediating estradiol conversion, as the central dysregulated node in EOPE pathogenesis. Multi-modal computational analysis (cluster annotation, cellular proportion calculation, comparison of differentially expressed genes, and characterization of cellular developmental trajectories) revealed key expression dynamics during syncytiotrophoblast (SCT) differentiation, with substantial suppression in EOPE specimens. Further validation using clinical placental samples confirmed the downregulation of HSD17B1 at the protein level in patients with EOPE, as demonstrated by immunohistochemistry and western blotting. Mechanistically, HSD17B1 knockdown in BeWo trophoblast models recapitulated the core EOPE phenotypes of impaired SCT differentiation and estrogen biosynthesis blockade. These findings reveal that HSD17B1 is a master coordinator of trophoblast-endocrine crosstalk, the impairment of which in placental trophoblasts may contribute to EOPE pathogenesis. Our findings provide a mechanistic basis for developing HSD17B1-targeted interventions that could contribute to the concurrent restoration of placental competence and hormonal regulation, improving the perinatal outcomes of patients with EOPE.

Rosiglitazone-Mediated Activation of PPARγ Induces PlGF Expression in Trophoblast Cells

Preeclampsia (PE) is a hypertensive pregnancy disorder marked by impaired trophoblast invasion and placental vascular dysfunction, resulting in severe maternal and fetal complications. Placental growth factor (PlGF) is critical for proper placental angiogenesis and is transcriptionally regulated by glial cell missing-1 (GCM1), a downstream effector of peroxisome proliferator-activated receptor-gamma (PPARγ). Decreased PPARγ activity in PE may therefore contribute to diminished PlGF levels, worsening placental pathology. In this study, we investigated the mechanistic role of rosiglitazone, a PPARγ agonist, in rescuing PlGF expression under 1.5% oxygen/reoxygenation stress mimicking PE. Using JEG-3 trophoblast cells, we show that rosiglitazone enhances PPARγ nuclear translocation, leading to increased GCM1 and cyto-protective heme oxygenase-1 (HO-1) expression, and subsequent upregulation of PlGF production under both 21% oxygen and 1.5% oxygen/reoxygenation conditions. Pharmacologic inhibition of PPARγ with T0070907 or siRNA-mediated knockdown abrogated these effects, underscoring PPARγ's essential role in maintaining GCM1-driven PlGF expression. Notably, rosiglitazone treatment rescued PlGF production in 1.5% oxygen/reoxygenation-stressed cells, highlighting a potential therapeutic strategy to mitigate placental dysfunction. These findings define the PPARγ-GCM1-PlGF axis as a mechanistic cornerstone of placental health and suggest that pharmacological activation of PPARγ may offer clinical benefit in improving pregnancy outcomes in PE.

Reproductive Immunology and Pregnancy 2.0

This Special Issue comprises original articles in the field of clinical studies whose major topics concern the genetic and immunological aspects of miscarriage and pre-eclampsia, the isolation of decidua macrophages and Hofbauer cells in the placenta for diagnostic purposes, and epigenetic mechanisms that trigger labor [...].

Disruption of maternal vascular remodeling by a fetal endoretrovirus-derived gene in preeclampsia

BACKGROUND

Preeclampsia, one of the most lethal pregnancy-related diseases, is associated with the disruption of uterine spiral artery remodeling during placentation. However, the early molecular events leading to preeclampsia remain unknown.

RESULTS

By analyzing placentas from preeclampsia, non-preeclampsia, and twin pregnancies with selective intrauterine growth restriction, we show that the pathogenesis of preeclampsia is attributed to immature trophoblast and maldeveloped endothelial cells. Delayed epigenetic reprogramming during early extraembryonic tissue development leads to generation of excessive immature trophoblast cells. We find reduction of de novo DNA methylation in these trophoblast cells results in selective overexpression of maternally imprinted genes, including the endoretrovirus-derived gene PEG10 (paternally expressed gene 10). PEG10 forms virus-like particles, which are transferred from the trophoblast to the closely proximate endothelial cells. In normal pregnancy, only a low amount of PEG10 is transferred to maternal cells; however, in preeclampsia, excessive PEG10 disrupts maternal vascular development by inhibiting TGF-beta signaling.

CONCLUSIONS

Our study reveals the intricate epigenetic mechanisms that regulate trans-generational genetic conflict and ultimately ensure proper maternal-fetal interface formation.

Cell Fusion and Syncytia Formation in Cancer

The natural phenomenon of cell-cell fusion does not only take place in physiological processes, such as placentation, myogenesis, or osteoclastogenesis, but also in pathophysiological processes, such as cancer. More than a century ago postulated, today the hypothesis that the fusion of cancer cells with normal cells leads to the formation of cancer hybrid cells with altered properties is in scientific consensus. Some studies that have investigated the mechanisms and conditions for the fusion of cancer cells with other cells, as well as studies that have characterized the resulting cancer hybrid cells, are presented in this review. Hypoxia and the cytokine TNFα, for example, have been found to promote cell fusion. In addition, it has been found that both the protein Syncytin-1, which normally plays a role in placentation, and phosphatidylserine signaling on the cell membrane are involved in the fusion of cancer cells with other cells. In human cancer, cancer hybrid cells were detected not only in the primary tumor, but also in the circulation of patients as so-called circulating hybrid cells, where they often correlated with a worse outcome. Although some data are available, the questions of how and especially why cancer cells fuse with other cells are still not fully answered.

COVID-19. Biology, pathophysiology, and immunology: a pathologist view

Even if the SARS-CoV-2 pandemic has been declared over, several risks and clinical problems remain to be faced, including long-COVID sequelae and possible outbreaks of pathogenic variants. Intense research on COVID-19 has provided in these few years a striking amount of data covering different fields and disciplines, which can help to provide a knowledge shield against new potential infective spreads, and may also potentially be applied to other fields of medicine, including oncology and neurology. Nevertheless, areas of uncertainty still remain regarding the pathogenic mechanisms that subtend the multifaceted manifestations of the disease. To better clarify the pathogenesis of the disease, a systematic multidisciplinary evaluation of the many mechanisms involved in COVID-19 is mandatory, including clinical, physiological, radiological, immunological and pathological studies. In COVID-19 syndrome the pathological studies have been mainly performed on autopsy cases, and only a few studies are available on biopsies. Nevertheless, these studies have provided relevant information that can substantially contribute to decipher the complex scenario characterizing the different forms of COVID-19 and long-COVID-19. In this review the data provided by pathological investigations are recapitulated and discussed, in the light of different hypothesis and data provided by clinical, physiological and immunological data.