Tiny miRNA in the placenta may explain why female fetuses bear the brunt of growth restriction

Fetal growth restriction, or FGR, is one of the most consequential complications of human pregnancy, affecting between five and ten percent of all pregnancies and leaving affected babies facing higher risks of perinatal death, lifelong metabolic disease, and neurodevelopmental impairment. The dominant pathological driver is placental insufficiency: the placenta simply fails to build the dense microvascular network that the growing fetus depends on for oxygen and nutrients. Now a research team in Shijiazhuang, China, has traced that failure, at least in female fetuses, to a single molecular misstep involving a tiny regulatory RNA, a pro-angiogenic growth factor, and one of the cell’s most fundamental survival circuits.

The new study, published in Frontiers in Cell and Developmental Biology, focuses on miR-543, a microRNA that had already surfaced in the team’s earlier transcriptomic sequencing work as the most significantly dysregulated microRNA in the placentas of female fetuses with growth restriction. MicroRNAs are short non-coding RNA molecules that fine-tune gene expression after transcription, typically by binding to the 3-prime untranslated region of target messenger RNAs and blocking their translation or hastening their degradation. What makes the new finding striking is its sex specificity: miR-543 was markedly downregulated in female FGR placentas compared with matched controls, but showed no significant change in male FGR placentas, a pattern that mirrors the broader observation that female placentas are more susceptible to angiogenic dysfunction than male ones.

To pin down the mechanism, the researchers collected placental tissue from pregnancies delivered at the Fourth Hospital of Shijiazhuang between January 2022 and December 2024, recruiting ten FGR cases and ten controls for each fetal sex, with FGR defined by a birth weight below the tenth percentile for gestational age. Samples were retrieved within thirty minutes of vaginal delivery, snap-frozen in liquid nitrogen, and stored at minus eighty degrees Celsius, with fragments taken from five different placental regions and from sites four to six centimeters from the umbilical cord insertion to minimize sampling bias. Pregnancies complicated by preeclampsia, gestational diabetes, preterm delivery before thirty-seven weeks, or multiple gestation were excluded, and the study was registered with the Chinese Clinical Trial Registry before recruitment began.

Bioinformatic screening with two independent target-prediction algorithms, TargetScan and miRanda, converged on ANGPT2, the gene encoding angiopoietin-2, as the leading candidate target of miR-543, alongside AGGF1. Angiopoietin-2 is a well-known pro-angiogenic factor that cooperates with vascular endothelial growth factor during the non-branching phase of placental vascular development, the critical window in which the villous microvasculature, the functional unit of fetoplacental exchange, is established. The predictive confidence was high, with a miRanda energy score of minus 11.6 and a TargetScan score of 95, and a dual-luciferase reporter assay in HEK-293T cells confirmed the interaction directly: co-transfection of miR-543 mimics with a wild-type ANGPT2 reporter plasmid significantly reduced luciferase activity, while a mutant reporter carrying a disrupted seed sequence showed no such suppression.

One of the study’s most technically impressive moves was the use of laser capture microdissection to isolate endothelial cells from frozen placental sections. Because placental tissue is a mosaic of trophoblasts, stromal cells, perivascular cells, and endothelial cells, bulk tissue analysis can mask cell-specific gene expression. The team stained twelve-micrometer frozen sections with hematoxylin and eosin, identified capillary-rich regions under the microscope, and used an ArcturusXT system with CapSure HS caps to pluck endothelial cells directly from the tissue. Quantitative PCR on these microdissected cells revealed a marked upregulation of ANGPT2 in female FGR placentas, and immunofluorescence staining showed that ANGPT2 co-localized with CD31, the canonical endothelial marker, confirming that the dysregulation was concentrated precisely in the cells that build the placental microvasculature.

Functional assays in human umbilical vein endothelial cells, or HUVECs, the standard laboratory model of endothelial biology, then mapped out the consequences of the miR-543/ANGPT2 axis. Overexpressing miR-543 reduced cell proliferation over time in CCK-8 assays, suppressed migration in wound healing and Transwell systems, curtailed invasion through Matrigel-coated membranes, and diminished tube formation on Matrigel, reducing node number, master junctions, mesh count, and total tubule length. Knocking miR-543 down had the opposite effect, enhancing every one of these angiogenic parameters. ANGPT2 overexpression promoted proliferation, migration, invasion, and tube formation, while ANGPT2 silencing impaired them, and flow cytometry with Annexin V and 7-AAD staining showed that miR-543 overexpression increased endothelial apoptosis while ANGPT2 overexpression protected against it.

Western blotting then connected the axis to a signaling pathway. KEGG enrichment analysis of predicted miR-543 targets pointed to the PI3K/AKT/mTOR cascade, a core pro-survival circuit that regulates cell growth, proliferation, and resistance to apoptosis and has already been implicated in preeclampsia and FGR. The blots showed that phosphorylation of PI3K, AKT, and mTOR was suppressed by miR-543 overexpression or ANGPT2 knockdown and enhanced by miR-543 inhibition or ANGPT2 overexpression. Caspase-3, the executioner protease of apoptosis, rose when miR-543 was overexpressed or ANGPT2 silenced. Rescue experiments with LY294002, a pharmacological PI3K inhibitor, enhanced endothelial apoptosis and confirmed pathway specificity, while TUNEL staining showed that angiopoietin-2 could reverse miR-543-induced cell death in a PI3K/AKT-dependent manner.

The authors interpret the downregulation of miR-543 in female FGR placentas as a compensatory response rather than a primary cause. Because reduced miR-543 releases ANGPT2 from repression, the female placenta appears to attempt an adaptive surge of angiogenic activity under adverse intrauterine conditions, echoing observations in diabetic retinopathy where miR-543 suppresses angiogenic responses in retinal endothelial cells. Intriguingly, miR-543 has been reported to promote angiogenesis in lung cancer and myocardial infarction models, so its opposite role in placental capillaries underscores how context-dependent microRNA biology can be. The sex-specific pattern also fits a growing literature on sexual dimorphism in placental epigenetic regulation, including prior work showing that male fetuses are more susceptible to early-life insults while female placentas show greater vulnerability to angiogenic dysfunction.

The study has acknowledged limitations. The sample size of ten cases per sex per group restricts statistical power, HUVECs may not fully recapitulate the biology of fetal placental microvascular endothelial cells, and the mechanism was not validated in vivo, so neither miR-543 nor ANGPT2 can yet be proposed as therapeutic targets. The authors call for future work using larger clinical cohorts, primary placental endothelial cells or placental organoids, and appropriate animal models to confirm the axis and explore its clinical potential.

Even so, the findings add a genuinely novel layer to the pathogenesis of fetal growth restriction: a microRNA-mediated, sex-dependent, and cell-specific regulatory mechanism in which miR-543 directly represses ANGPT2, modulating endothelial survival and capillary angiogenesis through the PI3K/AKT/mTOR pathway. If the axis holds up in larger studies, it could eventually yield biomarkers for identifying female fetuses at risk of growth restriction, or even targets for interventions aimed at restoring placental vascular function before the damage becomes irreversible.

Subject of Research: Placental Biology

Article Title: miRNA-543 attenuates placental angiogenesis in female fetal growth restriction by targeting ANGPT2 and inhibiting the PI3K/AKT/mTOR pathway

Article References: Song, W., Yang, X., Yang, C., Zhao, Y., Zhang, X., & Guo, Q. (2026). miRNA-543 attenuates placental angiogenesis in female fetal growth restriction by targeting ANGPT2 and inhibiting the PI3K/AKT/mTOR pathway. Frontiers in Cell and Developmental Biology, 14, Article 1912518. https://doi.org/10.3389/fcell.2026.1912518

Image Credits: AI Generated

DOI: 10.3389/fcell.2026.1912518

Keywords: fetal growth restriction, placental angiogenesis, miR-543, ANGPT2, PI3K/AKT/mTOR, endothelial cells, sexual dimorphism, microRNA, miRNA-543, attenuates, placental, angiogenesis