Trophoblasts Modulate the Ca2+ Oscillation and Contraction of Myometrial Smooth Muscle Cells by Small Extracellular Vesicle- (sEV-) Mediated Exporting of miR-25-3p during Premature Labor

Emerging role of toll-like receptors signaling and its regulators in preterm birth: a narrative review

INTRODUCTION

Despite intensive research, preterm birth (PTB) rates have not decreased significantly in recent years due to a lack of understanding of the underlying causes and insufficient treatment options for PTB. We are committed to finding promising biomarkers for the treatment of PTB.

METHODS

An extensive search of the literature was conducted with MEDLINE/PubMed, and in total, 151 studies were included and summarized in the present review.

RESULTS

Substantial evidence supports that the infection and/or inflammatory cascade associated with infection is an early event in PTB. Toll-like receptor (TLR) is a prominent pattern recognition receptor (PRR) found on both immune and non-immune cells, including fetal membrane cells. The activation of TLR downstream molecules, followed by TLR binding to its ligand, is critical for infection and inflammation, leading to the involvement of the TLR signaling pathway in PTB. TLR ligands are derived from microbial components and molecules released by damaged and dead cells. Particularly, TLR4 is an essential TLR because of its ability to recognize lipopolysaccharide (LPS). In this comprehensive overview, we discuss the role of TLR signaling in PTB, focus on numerous host-derived genetic and epigenetic regulators of the TLR signaling pathway, and cover ongoing research and prospective therapeutic options for treating PTB by inhibiting TLR signaling.

CONCLUSION

This is a critical topic because TLR-related molecules and mechanisms may enable obstetricians to better understand the physiological changes in PTB and develop new treatment and prevention strategies.

Human Trophoblast Cell-Derived Extracellular Vesicles Facilitate Preeclampsia by Transmitting miR-1273d, miR-4492, and miR-4417 to Target HLA-G

Extracellular vesicles (EVs) can intercellularly transmit a wide range of bioactive molecules, and these cargoes may potentially serve as therapeutic biomarkers for preeclampsia. Herein, the current study aims to elucidate the mechanism underlying the human trophoblast cell-derived EV-mediated miRNA-mRNA network that could potentially influence the development of preeclampsia based on microarray datasets from publicly available GEO databases. Preeclampsia-related genes were retrieved from the GeneCards and CTD databases, which were then subjected to GO and KEGG enrichment analyses in an effort to identify key pathways in preeclampsia. The obtained results suggested an important role of the immune- and inflammation-related pathways in preeclampsia. Infiltration proportion of 22 immune cells was subsequently analyzed using the CIBERSORT algorithm. Placental tissues of patients with preeclampsia presented with increased proportion of resting NK cells and resting dendritic cells, while there was a reduction in the proportion of activated NK cells. Differentially expressed mRNAs were additionally predicted in the preeclampsia-related datasets retrieved from the GEO database, and then intersected with preeclampsia-related genes to identify the key genes. HLA-G was indicated as a key target gene in the development of preeclampsia and further associated with hypoxia, immune, and inflammatory pathways. The upstream microRNAs (miRNAs/miRs) of the key genes were further predicted and intersected with differentially expressed miRNAs in the human trophoblast cell-derived EV-related datasets from the GEO database to obtain the key miRNAs. EVs secreted by human trophoblast cells under hypoxic conditions were associated with 3 key upstream miRNAs of HLA-G, namely miR-1273d, miR-4492, and miR-4417, which might be implicated in the development of preeclampsia via targeting of HLA-G. Collectively, our findings highlighted that EVs secreted by human trophoblast cells under hypoxic conditions transferred miR-1273d, miR-4492, and miR-4417, all of which targeted HLA-G, thus orchestrating immune- and inflammation-related pathways and consequently promoting the development of preeclampsia.