Diagnostic potential for miRNAs as biomarkers for pregnancy-specific diseases

Exploring gene expression signatures in preeclampsia and identifying hub genes through bioinformatic analysis

INTRODUCTION

Preeclampsia (PE) is a multisystem disease that affects women during the pregnancy. Its pathogenicity remains unclear, and no definitive screening test can predict its occurrence so far. The aim of this study is to identify the critical genes that are involved in the pathogenicity of PE by applying integrated bioinformatic methods and to investigate the genes' diagnostic capability.

METHODS

Datasets that investigated PE have been downloaded from Gene Expression Omnibus (GEO) datasets. Differential gene expression, weighted gene co-expression analysis (WGCNA), protein-protein interaction (PPI) network construction, and finally, the calculation of area under the curve and Receiver operating characteristic curve (ROC) analysis were done for the potential hub genes. The results generated from the GSE186257 dataset (discovery cohort) were validated in the GSE75010 dataset (validation cohort). Following validation of the hub-genes, a multilayer regulatory network was constructed to include the up-stream regulatory elements (transcription factors and miRNAs) of the validated hub-genes.

RESULTS

WGCNA revealed six modules that were significantly correlated with PE. A total of 231 differentially expressed genes (DEGs) were identified. DEGs were intersected with the WGCNA modules' genes, totalling 55 genes. These shared genes were used to construct the PPI network; subsequently, four genes, namely FLT1, HTRA4, LEP and PAPPA2, were identified as hub-genes for PE in the discovery cohort. The expressional of these four hub genes were validated in the validation cohort and found to be highly expressed. ROC analysis in both datasets revealed that all these genes had a significant PE diagnostic ability. The regulatory network showed that FLT1 gene is the most connected and regulated gene among the validated hub-genes.

DISCUSSION

This integrated analysis revealed that FLT1, LEP, HTRA4 and PAPPA2 may be strongly involved in the pathogenicity of PE and act as promising biomarkers and potential therapeutic targets for PE.

Increased Levels of hsa-miR-199a-3p and hsa-miR-382-5p in Maternal and Neonatal Blood Plasma in the Case of Placenta Accreta Spectrum

Despite the increasing number of placenta accreta spectrum (PAS) cases in recent years, its impact on neonatal outcomes and respiratory morbidity, as well as the underlying pathogenetic mechanism, has not yet been extensively studied. Moreover, no study has yet demonstrated the effectiveness of antenatal corticosteroid therapy (CT) for the prevention of respiratory distress syndrome (RDS) in newborns of mothers with PAS at the molecular level. In this regard, microRNA (miRNA) profiling by small RNA deep sequencing and quantitative real-time PCR was performed on 160 blood plasma samples from preterm infants (gestational age: 33-36 weeks) and their mothers who had been diagnosed with or without PAS depending on the timing of the antenatal RDS prophylaxis. A significant increase in hsa-miR-199a-3p and hsa-miR-382-5p levels was observed in the blood plasma of the newborns from mothers with PAS compared to the control group. A clear trend toward the normalization of hsa-miR-199a-3p and hsa-miR-382-5p levels in the neonatal blood plasma of the PAS groups was observed when CT was administered within 14 days before delivery, but not beyond 14 days. Direct correlations were found among the hsa-miR-382-5p level in neonatal blood plasma and the hsa-miR-199a-3p level in the same sample (r = 0.49; p < 0.001), the oxygen requirements in the NICU (r = 0.41; p = 0.001), the duration of the NICU stay (r = 0.31; p = 0.019), and the severity of the newborn's condition based on the NEOMOD scale (r = 0.36; p = 0.005). Logistic regression models based on the maternal plasma levels of hsa-miR-199a-3p and hsa-miR-382-5p predicted the need for cardiotonic therapy, invasive mechanical ventilation, or high-frequency oscillatory ventilation in newborns during the early neonatal period, with a sensitivity of 95-100%. According to the literary data, these miRNAs regulate fetal organogenesis via IGF-1, the formation of proper lung tissue architecture, surfactant synthesis in alveolar cells, and vascular tone.

Extracellular Vesicles as Biomarkers of Pregnancy Complications

Extracellular vesicles (EVs) are double-membrane vesicles that facilitate intercellular communication and play a pivotal role in both physiological and pathological processes. A substantial body of evidence suggests that EVs play a role in the pathogenesis of various pregnancy complications. Because EVs can be detected in the peripheral blood, they are potential biomarkers for the early diagnosis of pregnancy complications and foetal developmental disorders. The majority of studies have demonstrated a correlation between alterations in the concentration of EVs and changes in their contents and the occurrence of pregnancy complications. Despite the current limitations in establishing a clear link between these findings and the pathogenesis of the disease, as well as the lack of sufficient evidence to support their use in clinical practice, it is noteworthy to highlight the potential role of specific miRNAs carried by EVs in the development of pregnancy complications. These include miR-210 and miR-136-5p for pre-eclampsia and gestational diabetes mellitus, miR-155, miR-26b-5p, miR-181a-5p, miR-495 and miR-374c for pre-eclampsia and preterm birth. The following miRNAs have been identified as potential biomarkers for preterm birth and gestational diabetes mellitus: miR-197-3p and miR-520h, miR-1323, miR-342-3p, miR-132-3p, miR-182-3p, miR-517-3p, miR-222-3p, miR-16-5p and miR-126-3p. Additionally, miR-127-3p has been linked to foetal growth restriction and preterm birth. Nevertheless, it would be premature to propose that EVs can be employed as biomarkers for pregnancy complications. Further research and the accumulation of results obtained using the methods proposed in the MISEV2023 guidelines will enable a definitive conclusion to be reached.

Circulating extracellular vesicular microRNA signatures in early gestation show an association with subsequent clinical features of pre-eclampsia

In a prospective cohort of subjects who subsequently developed preeclampsia (PE, n = 14) versus remaining healthy (NORM, n = 12), early gestation circulating extracellular vesicles (EVs) containing a panel of microRNA signatures were characterized and their biological networks of targets deciphered. Multiple microRNAs of which some arose from the placenta (19MC and 14MC) demonstrated changes in association with advancing gestation, while others expressed were pathognomonic of the subsequent development of characteristic clinical features of PE which set in as a late-onset subtype. This panel of miRNAs demonstrated a predictability with an area under the curve of 0.96 using leave-one-out cross-validation training in a logistic regression model with elastic-net regularization and precautions against overfitting. In addition, this panel of miRNAs, some of which were previously detected in either placental tissue or as maternal cell-free non-coding transcripts, lent further validation to our EV studies and the observed association with PE. Further, the identified biological networks of targets of these detected miRNAs revealed biological functions related to vascular remodeling, cellular proliferation, growth, VEGF, EGF and the PIP3/Akt signaling pathways, all mediating key cellular functions. We conclude that we have demonstrated a proof-of-principle by detecting a panel of EV packaged miRNAs in the maternal circulation early in gestation with possibilities of biological function in the placenta and other maternal tissues, along with the probability of predicting the subsequent clinical appearance of PE, particularly the late-onset subtype.

Expression and clinical significance of miR-141-5p as a biomarker in the serum of patients with early spontaneous abortion

AIM

miR-141-5p expression in patients with Early Spontaneous Abortion (ESA) and its correlation with hormone levels during pregnancy were investigated.

METHODS

A total of 70 pregnant women with ESA were selected as the research group, and 70 normal pregnant women who chose abortion for non-medical reasons were selected as the Con group. Serum β-HCG, Progesterone (P), and Estrogen (E2) were detected by enzyme-linked immunosorbent assay. Differentially expressed miRNAs were screened by miRNA microarray analysis. miR-141-5p expression was detected by RT-qPCR, and its correlation with serum β-HCG, P, and E2 levels was analyzed. The diagnostic value of miR-141-5p for ESA was evaluated by the ROC curve.

RESULTS

Serum β-HCG, P, and E2 were decreased and serum miR-141-5p was increased in patients with ESA. Pearson correlation analysis showed that serum β-HCG, P, and E2 levels were negatively correlated with miR-141-5p expression levels. ROC curve showed that miR-141-5p had a diagnostic value for ESA.

CONCLUSIONS

miR-141-5p is related to hormone levels during pregnancy and is expected to become a new candidate diagnostic marker for ESA.

microRNA as a Maternal Marker for Prenatal Stress-Associated ASD, Evidence from a Murine Model

Autism Spectrum Disorder (ASD) has been associated with a complex interplay between genetic and environmental factors. Prenatal stress exposure has been identified as a possible risk factor, although most stress-exposed pregnancies do not result in ASD. The serotonin transporter (SERT) gene has been linked to stress reactivity, and the presence of the SERT short (S)-allele has been shown to mediate the association between maternal stress exposure and ASD. In a mouse model, we investigated the effects of prenatal stress exposure and maternal SERT genotype on offspring behavior and explored its association with maternal microRNA (miRNA) expression during pregnancy. Pregnant female mice were divided into four groups based on genotype (wildtype or SERT heterozygous knockout (Sert-het)) and the presence or absence of chronic variable stress (CVS) during pregnancy. Offspring behavior was assessed at 60 days old (PD60) using the three-chamber test, open field test, elevated plus-maze test, and marble-burying test. We found that the social preference index (SPI) of SERT-het/stress offspring was significantly lower than that of wildtype control offspring, indicating a reduced preference for social interaction on social approach, specifically for males. SERT-het/stress offspring also showed significantly more frequent grooming behavior compared to wildtype controls, specifically for males, suggesting elevated repetitive behavior. We profiled miRNA expression in maternal blood samples collected at embryonic day 21 (E21) and identified three miRNAs (mmu-miR-7684-3p, mmu-miR-5622-3p, mmu-miR-6900-3p) that were differentially expressed in the SERT-het/stress group compared to all other groups. These findings suggest that maternal SERT genotype and prenatal stress exposure interact to influence offspring behavior, and that maternal miRNA expression late in pregnancy may serve as a potential marker of a particular subtype of ASD pathogenesis.

Serum exosomal miR-192 serves as a potential detective biomarker for early pregnancy screening in sows

OBJECTIVE

The study was conducted to screen differentially expressed miRNAs in sows at early pregnancy by high-throughput sequencing and explore its mechanism of action on embryo implantation.

METHODS

The blood serum of pregnant and non-pregnant Landrace×Yorkshire sows were collected 14 days after artificial insemination, and exosomal miRNAs were purified for high throughput miRNA sequencing. The expression patterns of 10 differentially expressed (DE) miRNAs were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The qRT-PCR quantified the abundance of serum exosomal miR-192 in pregnant and control sows, and the diagnostic power was assessed by receiver operating characteristic (ROC) analysis. The target genes of DE miRNAs were predicted with bioinformatics software, and the functional and pathway enrichment analysis was performed on gene ontology and the Kyoto encyclopedia of genes and genomes terms. Furthermore, a luciferase reporter system was used to identify the target relation between miR-192 and integrin alpha 4 (ITGA4), a gene influencing embryo implantation in pigs. Finally, the expression levels of miRNAs and the target gene ITGA4 were analyzed by qRT-PCR, and western blot, with the proliferation of BeWo cells detected by cell counting kit-8 (CCK-8).

RESULTS

A total of 221 known miRNAs were detected in the libraries of the pregnant and non-pregnant sows, of which 55 were up-regulated and 67 were down-regulated in the pregnant individuals compared with the non-pregnant controls. From these, the expression patterns of 10 DE miRNAs were validated. The qRT-PCR analysis further confirmed a significantly higher expression of miR-192 in the serum exosomes extracted from pregnant sows, when compared to controls. The ROC analysis revealed that miR-192 provided excellent diagnostic accuracy for pregnancy (area under the ROC curve [AUC] = 0.843; p>0.001). The dual-luciferase reporter assay indicated that miR-192 directly targeted ITGA4. The protein expression of ITGA4 was reduced in cells that overexpressed miR-192. Overexpression of miR-192 resulted in the decreased proliferation of BeWo cells and regulated the expression of cell cycle-related genes.

CONCLUSION

Serum exosomal miR-192 could serve as a potential biomarker for early pregnancy in pigs. miR-192 targeted ITGA4 gene directly, and miR-192 can regulate cellular proliferation.

Consequences of the exposome to gestational diabetes mellitus

The exposome is the cumulative measure of environmental influences and associated biological responses throughout the lifespan, including those from the environment, diet, behaviour, and endogenous processes. The exposome concept and the 2030 Agenda for the Sustainable Development Goals (SDGs) from the United Nations are the basis for understanding the aetiology and consequences of non-communicable diseases, including gestational diabetes mellitus (GDM). Pregnancy may be developed in an environment with adverse factors part of the immediate internal medium for fetus development and the external medium to which the pregnant woman is exposed. The placenta is the interface between maternal and fetal compartments and acts as a protective barrier or easing agent to transfer exposome from mother to fetus. Under and over-nutrition in utero, exposure to adverse environmental pollutants such as heavy metals, endocrine-disrupting chemicals, pesticides, drugs, pharmaceuticals, lifestyle, air pollutants, and tobacco smoke plays a determinant role in the development of GDM. This phenomenon is worsened by metabolic stress postnatally, such as obesity which increases the risk of GDM and other diseases. Clinical risk factors for GDM development include its aetiology. It is proposed that knowledge-based interventions to change the potential interdependent ecto-exposome and endo-exposome could avoid the occurrence and consequences of GDM.

Aggregation of Genome-Wide Association Data from FinnGen and UK Biobank Replicates Multiple Risk Loci for Pregnancy Complications

Complications endangering mother or fetus affect around one in seven pregnant women. Investigation of the genetic susceptibility to such diseases is of high importance for better understanding of the disease biology as well as for prediction of individual risk. In this study, we collected and analyzed GWAS summary statistics from the FinnGen cohort and UK Biobank for 24 pregnancy complications. In FinnGen, we identified 11 loci associated with pregnancy hypertension, excessive vomiting, and gestational diabetes. When UK Biobank and FinnGen data were combined, we discovered six loci reaching genome-wide significance in the meta-analysis. These include rs35954793 in FGF5 (p=6.1×10-9), rs10882398 in PLCE1 (p=8.9×10-9), and rs167479 in RGL3 (p=5.2×10-9) for pregnancy hypertension, rs10830963 in MTNR1B (p=4.5×10-41) and rs36090025 in TCF7L2 (p=3.4×10-15) for gestational diabetes, and rs2963457 in the EBF1 locus (p=6.5×10-9) for preterm birth. In addition to the identified genome-wide associations, we also replicated 14 out of 40 previously reported GWAS markers for pregnancy complications, including four more preeclampsia-related variants. Finally, annotation of the GWAS results identified a causal relationship between gene expression in the cervix and gestational hypertension, as well as both known and previously uncharacterized genetic correlations between pregnancy complications and other traits. These results suggest new prospects for research into the etiology and pathogenesis of pregnancy complications, as well as early risk prediction for these disorders.

Analysis of serum circulating MicroRNAs level in Malaysian patients with gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a severe global issue that requires immediate attention. MicroRNA expression abnormalities are possibly disease-specific and may contribute to GDM pathological processes. To date, there is limited data on miRNA profiling in GDM, especially that involves a longitudinal study. Here, we performed miRNA expression profiling in the entire duration of pregnancy (during pregnancy until parturition and postpartum) using a miRNA- polymerase chain reaction array (miRNA-PCRArray) and in-silico analysis to identify unique miRNAs expression and their anticipated target genes in Malay maternal serum. MiRNA expression levels and their unique potential as biomarkers were explored in this work. In GDM patients, the expression levels of hsa-miR-193a, hsa-miR-21, hsa-miR-23a, and hsa-miR-361 were significantly increased, but miR-130a was significantly downregulated. The area under the curve (AUC) and receiver operating characteristic (ROC) curve study demonstrated that hsa-miR-193a (AUC = 0.89060 ± 04,470, P = 0.0001), hsa-miR-21 (AUC = 0.89500 ± 04,411, P = 0.0001), and miR-130a (AUC = 0.6939 ± 0.05845, P = 0.0025) had potential biomarker features in GDM. In-silico analysis also revealed that KLF (Kruppel-Like family of transcription factor), ZNF25 (Zinc finger protein 25), AFF4 (ALF transcription elongation factor 4), C1orf143 (long intergenic non-protein coding RNA 2869), SRSF2 (serine and arginine rich splicing factor 2), and ZNF655 (Zinc finger protein 655) were prominent genes targeted by the common nodes of miR23a, miR130, miR193a, miR21, and miR361.Our findings suggest that circulating microRNAs in the first trimester has the potential for GDM screening in the Malay population.

The Role of Cluster C19MC in Pre-Eclampsia Development

Pre-eclampsia is a placenta-related complication occurring in 2-10% of all pregnancies. miRNAs are a group of non-coding RNAs regulating gene expression. There is evidence that C19MC miRNAs are involved in the development of the placenta. Deregulation of chromosome 19 microRNA cluster (C19MC) miRNAs expression leads to impaired cell differentiation, abnormal trophoblast invasion and pathological angiogenesis, which can lead to the development of pre-eclampsia. Information was obtained through a review of articles available in PubMed Medline. Articles on the role of the C19MC miRNA in the development of pre-eclampsia published in 2009-2022 were analyzed. This review article summarizes the current data on the role of the C19MC miRNA in the development of pre-eclampsia. They indicate a significant increase in the expression of most C19MC miRNAs in placental tissue and a high level of circulating fractions in serum and plasma, both in the first and/or third trimester in women with PE. Only for miR-525-5p, low levels of plasma expression were noted in the first trimester, and in the placenta in the third trimester. The search for molecular factors indicating the development of pre-eclampsia before the onset of clinical symptoms seems to be a promising diagnostic route. Identifying women at risk of developing pre-eclampsia at the pre-symptomatic stage would avoid serious complications in both mothers and fetuses. We believe that miRNAs belonging to cluster C19MC could be promising biomarkers of pre-eclampsia development.

Upregulation of miR-181a-5p and miR-125b-2-3p in the Maternal Circulation of Fetuses with Rh-Negative Hemolytic Disease of the Fetus and Newborn Could Be Related to Dysfunction of Placental Function

The transplacental transfer of maternal antibodies to the fetus is a critical mechanism for infant protection and perinatal disease. Hemolytic disease of the fetus and newborn (HDFN) is a representative fetal disease caused by transplacental transfer of maternal IgG antibodies. However, it is unclear whether placental-related miRNAs are expressed in Rh-HDFN. Through the investigation of the miR-181a-5p and miR-125b-2-3p levels in maternal plasma using qPCR, we found that both miR-181a-5p and miR-125b-2-3p were highly expressed in maternal plasma of newborns with Rh-HDFN compared with healthy controls, indicating the potential roles of these two miRNAs in Rh-HDFN. To demonstrate whether dysregulation of miR-125b-2-3p and miR-181a-5p contributes to Rh-HDFN development, we analyze the placental miRNA-/mRNA sequencing data (GSE73714) using weighted gene coexpression network analysis (WGCNA), miRNA target predictive databases, and DAVID (Database for Annotation, Visualization, and Integrated Discovery). The results showed that miR-125b-2-3p and miR-181a-5p could regulate several biological processes including cytoplasmic microtubule organization and angiogenesis. Moreover, core promoter sequence-specific DNA binding and protein binding were highly enriched molecular functions, indicating the potential roles of transcriptional regulation. Further pathway enrichment showed that miR-181a-5p and miR-125b-2-3p could regulate several biological pathways that were closely related to placental function, including the FoxO signaling pathway, focal adhesion, mTOR signaling pathway, and central carbon metabolism in cancer. In conclusion, the present results first revealed miRNA expression in the maternal circulation of newborns with Rh-HDFN, which could be caused by dysfunction of the placenta.

Integrative analysis of circulating microRNAs and the placental transcriptome in recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a major type of pathological pregnancy that still lacks reliable early diagnosis and effective treatment. The placenta is critical to fetal development and pregnancy success because it participates in critical processes such as early embryo implantation, vascular remodeling, and immunological tolerance. RPL is associated with abnormalities in the biological behavior of placental villous trophoblasts, resulting in aberrant placental function. MicroRNAs (miRNAs) are increasingly being recognized as essential regulators of placental development, as well as potential biomarkers. In this study, plasma miRNAs and placental messenger RNAs (mRNAs) from RPL patients and normal pregnant (NP) controls were sequenced and analyzed. Compared to those in NP controls, 108 circulating miRNAs and 1199 placental mRNAs were differentially expressed in RPL samples. A total of 140 overlapping genes (overlapping between plasma miRNA target genes and actual placental disorder genes) were identified, and functional enrichment analysis showed that these genes were mainly related to cell proliferation, angiogenesis, and cell migration. The regulatory network among miRNAs, overlapping genes, and downstream biological processes was analyzed by protein–protein interactions and Cytoscape. Moreover, enriched mRNAs, which were predictive targets of the differentially expressed plasma miRNAs miR-766-5p, miR-1285-3p, and miR-520a-3p, were accordingly altered in the placenta. These results suggest that circulating miRNAs may be involved in the pathogenesis of RPL and are potential noninvasive biomarkers for RPL.

microRNA signatures associated with fetal growth restriction: a systematic review

Placental-origin microRNA (miRNA) profiles can be useful toward early diagnosis and management of fetal growth restriction (FGR) and associated complications. We conducted a systematic review to identify case-control studies that have examined miRNA signatures associated with human FGR. We systematically searched PubMed and ScienceDirect databases for relevant articles and manually searched reference lists of the relevant articles till May 18th, 2021. Of the 2133 studies identified, 21 were included. FGR-associated upregulation of miR-210 and miR-424 and downregulation of a placenta-specific miRNA cluster miRNA located on C19MC (miR-518b, miR-519d) and miR-221-3p was reported by >1 included studies. Analysis of the target genes of these miRNA as well as pathway analysis pointed to the involvement of angiogenesis and growth signaling pathways, such as the phosphatidylinositol 3-kinase- protein kinase B (PI3K-Akt) pathway. Only 3 out of the 21 included studies reported FGR-associated miRNAs in matched placental and maternal blood samples. We conclude that FGR-associated placental miRNAs could be utilized to inform clinical practice towards early diagnosis of FGR, provided enough evidence from studies on matched placental and maternal blood samples become available.Prospective Register of Systematic Reviews (PROSPERO) registration number: CRD42019136762.

miR-373-3p Regulates the Proliferative and Migratory Properties of Human HTR8 Cells via SLC38A1 Modulation

The genetic pathogenesis of selective intrauterine growth restriction (sIUGR) remains elusive, with evidence suggesting an important role of epigenetic factors such as microRNAs. In this study, we explored the relevance of miR-373-3p to the occurrence of sIUGR. Hypoxia enhanced the levels of miR-373-3p and hypoxia-inducible factor (HIF)-1α, while HIF-1α knockdown not only boosted the migration and proliferation of HTR8 cells but also suppressed the hypoxia-induced upregulation of miR-373-3p and SLC38A1. By contrast, HIF-1α overexpression induced miR-373-3p downregulation and SLC38A1 upregulation, reducing cell growth and migration, which could be reversed by a miR-373-3p inhibitor. Importantly, the miR-373-3p inhibitor and mimic reproduced phenomena similar to those induced by HIF-1α downregulation and overexpression, respectively (including altered SLC38A1 expression, mTOR activation, cell growth, and migration). Mechanistically, the miRNA regulated cell behaviors and related mTOR signaling by targeting SLC38A1 expression through an interaction with the 3′-untranslated region of SLC38A1. The placental tissues of smaller sIUGR fetuses exhibited miR-373-3p and HIF-1α upregulation, SLC38A1 downregulation, and activated mTOR. Overall, miR-373-3p appears to restrict the growth and migration of HTR8 trophoblast cells by targeting SLC38A1, as observed in the placental tissues associated with smaller sIUGR fetuses, and it could have utility in the diagnosis and treatment of this disorder.

The downregulation of miR-22 and miR-372 may contribute to gestational diabetes mellitus through regulating glucose metabolism via the PI3K/AKT/GLUT4 pathway

Background

Identifying effective regulatory mechanisms will be significant for Gestational diabetes mellitus (GDM) diagnosis and treatment.

Methods

The expressions of miR‐22 and miR‐372 in placenta tissues from 75 pregnant women with GDM and 75 matched healthy controls and HRT8/SVneo cells (a model of insulin resistance) were analyzed by qPCR. The expressions of PI3K, AKT, IRS, and GLUT4 in high glucose‐treated HRT8/SVneo cells transfected with miR‐22 or miR‐372 mimics or inhibitors was assessed by Western blot. A luciferase gene reporter assay was employed to verify miRNAs' target genes.

Results

The expressions of miR‐22 and miR‐372 in placental tissues from GDM patients and HRT8/SVneo cells were significantly decreased compared with the respective controls. The GLUT4 expression was significantly decreased in the placenta tissues of GDM and HRT8/SVneo cells with high glucose transfected with miR‐22 and miR‐372 inhibitors. We confirmed that SLC2A4, the gene encoding GLUT4, was a direct target of miR‐22 and miR‐372. In this study, we report that the lower expressions of miR‐22 and miR‐372 in placental tissue from GDM patients.

Conclusion

Our results further suggested that the downregulations of miR‐22 and miR‐372 may contribute to GDM through regulating the PI3K/GLUT4 pathway.

miR-146b-5p and miR-520h Expressions Are Upregulated in Serum of Women with Recurrent Spontaneous Abortion

Unexplained recurrent spontaneous abortion (URSA) is characterized by two or more consecutive pregnancy losses before the 20th week of gestation with unknown etiology. Dysregulation of microRNAs (miRNAs) expression has been reported in reproductive diseases. This study aimed to compare differentially expressed miRNAs in the serum samples between URSA patients and healthy individuals. URSA cases were confirmed by a gynecologist. Peripheral blood sample was‏ gathered from 9 URSA patients, 15 normal pregnant, and 10 non-pregnant women without abortion history. After separating serum, the expression levels of the miR-101-3p, miR-517c-3p, miR-146b-5p, miR-221-3p, and miR-520 h were measured by qRT-PCR assay. The circulating level of miR-520 h in URSA patients was significantly up-regulated compared with healthy pregnant (P < 0.01) and healthy non-pregnant (P = 0.002) women. Furthermore, miR-520 h expression was significantly different between healthy non-pregnant and pregnant women (P = 0.002). Statistical analysis indicated miR-146b-5p expression was significantly up-regulated in URSA patients compared to normal pregnant women (P = 0.018). However, the transcription level of miR-146b-5p was insignificantly different between normal non-pregnant women and the other two groups. Also, circulating levels of miR-101-3p, miR-221-3p, and miR-517c-3p were not significantly different in the studied groups. Statistical analysis showed significant correlations between both miR-221-3p and miR-517c-3p and other miRNAs (P < 0.05). The circulating levels of miR-520 h and miR-146b-5p could be considered biomarkers for URSA diagnosis. Also, miR-517c-3p and miR-221-3p might play a regulatory role in other miRNAs expressions during pregnancy. Previous work, in contrary to our findings, claims that the expression levels of miR-221-3p, miR-101-3p, and miR-517c-3p increased in plasma and tissue samples of patients with URSA. However, our research for the first time indicates that the expression level of miR-520 h and miR-146b-5p in the serum of these patients has increased. Future investigations are necessary to confirm these findings.

Preeclamptic Women Have Disrupted Placental microRNA Expression at the Time of Preeclampsia Diagnosis: Meta-Analysis

Introduction: Preeclampsia (PE) is a pregnancy-associated, multi-organ, life-threatening disease that appears after the 20th week of gestation. The aim of this study was to perform a systematic review and meta-analysis to determine whether women with PE have disrupted miRNA expression compared to women who do not have PE. Methods: We conducted a systematic review and meta-analysis of studies that reported miRNAs expression levels in placenta or peripheral blood of pregnant women with vs. without PE. Studies published before October 29, 2021 were identified through PubMed, EMBASE and Web of Science. Two reviewers used predefined forms and protocols to evaluate independently the eligibility of studies based on titles and abstracts and to perform full-text screening, data abstraction and quality assessment. Standardized mean difference (SMD) was used as a measure of effect size. Results: 229 publications were included in the systematic review and 53 in the meta-analysis. The expression levels in placenta were significantly higher in women with PE compared to women without PE for miRNA-16 (SMD = 1.51,95%CI = 0.55-2.46), miRNA-20b (SMD = 0.89, 95%CI = 0.33-1.45), miRNA-23a (SMD = 2.02, 95%CI = 1.25-2.78), miRNA-29b (SMD = 1.37, 95%CI = 0.36-2.37), miRNA-155 (SMD = 2.99, 95%CI = 0.83-5.14) and miRNA-210 (SMD = 1.63, 95%CI = 0.69-2.58), and significantly lower for miRNA-376c (SMD = -4.86, 95%CI = -9.51 to -0.20). An increased level of miRNK-155 expression was found in peripheral blood of women with PE (SMD = 2.06, 95%CI = 0.35-3.76), while the expression level of miRNA-16 was significantly lower in peripheral blood of PE women (SMD = -0.47, 95%CI = -0.91 to -0.03). The functional roles of the presented miRNAs include control of trophoblast proliferation, migration, invasion, apoptosis, differentiation, cellular metabolism and angiogenesis. Conclusion: miRNAs play an important role in the pathophysiology of PE. The identification of differentially expressed miRNAs in maternal blood creates an opportunity to define an easily accessible biomarker of PE.

High-Throughput Sequencing of Circulating MicroRNAs in Plasma and Serum during Pregnancy Progression

Although circulating microRNAs (miRNAs) in maternal blood may play an important role in regulation of pregnancy progression and serve as non-invasive biomarkers for different gestation complications, little is known about their profile in blood during normally developing pregnancy. In this study we evaluated the miRNA profiles in paired plasma and serum samples from pregnant women without health or gestational abnormalities at three time points using high-throughput sequencing technology. Sequencing revealed that the percentage of miRNA reads in plasma and serum decreased by a third compared to first and second trimesters. We found two miRNAs in plasma (hsa-miR-7853-5p and hsa-miR-200c-3p) and 10 miRNAs in serum (hsa-miR-203a-5p, hsa-miR-495-3p, hsa-miR-4435, hsa-miR-340-5p, hsa-miR-4417, hsa-miR-1266-5p, hsa-miR-4494, hsa-miR-134-3p, hsa-miR-5008-5p, and hsa-miR-6756-5p), that exhibit level changes during pregnancy (p-value adjusted < 0.05). In addition, we observed differences for 36 miRNAs between plasma and serum (p-value adjusted < 0.05), which should be taken into consideration when comparing the results between studies performed using different biosample types. The results were verified by analysis of three miRNAs using qRT-PCR (p < 0.05). The present study confirms that the circulating miRNA profile in blood changes during gestation. Our results set the basis for further investigation of molecular mechanisms, involved in regulation of pregnancy, and the search for biomarkers of gestation abnormalities.

Placental expression of miR-21-5p, miR-210-3p and miR-141-3p: relation to human fetoplacental growth

BACKGROUND/OBJECTIVES

Dysregulation of microRNAs (miRNAs) and their target genes in placental tissue is associated with foetal growth restriction. We aimed to evaluate associations of placental miR-21-5p, miR-141-3p and miR-210-3p expression with maternal, placental and newborn parameters and with placental expression of their potential target genes PTEN, VEGF, FLT and ENG in a set of well-characterized small- (SGA) and appropriate- (AGA) for gestational age full-term singleton pregnancies.

SUBJECTS/METHODS

Placental samples (n = 80) from 26 SGA and 54 AGA were collected from full-term singleton pregnancies. Placental transcript abundances of miR-21-5p, miR-141-3p and miR-210-3p were assessed after normalization to a reference miRNA, mir-16-5p by real-time quantitative PCR. Placental transcript abundances of PTEN, VEGF, FLT and ENG were assessed after normalizing to a panel of reference genes.

RESULTS

Placental miR-21-5p transcript abundance was negatively associated with placental weight (n = 80, r = -0.222, P = 0.047) and this association was specific to the AGA births (n = 54, r = -0.292, P = 0.032). Placental transcript abundances of miR-210-3p and miR-141-3p were not associated with placental weight or birth weight in all 80 births. However, placental miR-210-3p transcript abundance was positively associated with birth weight specifically in the SGA births (n = 26, r = 0.449, P = 0.021). Placental transcript abundance of miR-21-5p was negatively associated with PTEN transcript abundance (Spearman's ρ = -0.245, P = 0.028) while that of miR-141-3p was positively associated with FLT (Spearman's ρ = 0.261, P = 0.019) and ENG (Spearman's ρ = 0.259, P = 0.020) transcript abundances in all 80 births.

CONCLUSION

We conclude that placental miR-21-5p and miR-210-3p may be involved in fetoplacental growth. However, this regulation is unlikely to be mediated through placental expression of PTEN, VEGF, FLT or ENG.

Amniotic fluid microRNA profiles in twin-twin transfusion syndrome with and without severe recipient cardiomyopathy

BACKGROUND

Twin-twin transfusion syndrome presents many challenges for clinicians, and the optimal means of identifying pregnancies that will benefit most from intervention is controversial. There is currently no clinically available biomarker to detect twin-twin transfusion syndrome or to stratify cases based on the risk factors. microRNAs are small RNAs that regulate gene expression and are biomarkers for various disease processes, including adult and pediatric heart failure. To date, no studies have investigated amniotic fluid microRNAs as biomarkers for disease severity, specifically for severe recipient cardiomyopathy in twin-twin transfusion syndrome cases.

OBJECTIVE

This study aimed to assess whether amniotic fluid microRNAs could be useful as biomarkers to identify pregnancies at greatest risk for severe recipient cardiomyopathy associated with twin-twin transfusion syndrome.

STUDY DESIGN

Amniotic fluid was collected at the time of amnioreduction or selective fetoscopic laser photocoagulation from monochorionic diamniotic twin pregnancies with twin-twin transfusion syndrome at any stage. Fetal echocardiography was performed on all twins before the procedure, and severe cardiomyopathy was defined as a right ventricular myocardial performance index of the recipient fetus of >4 Z-scores. microRNA was extracted from the amniotic fluid samples and analyzed using an array panel assessing 379 microRNAs (TaqMan Open Array, ThermoFisher). Student t tests were performed to determine significant differences in microRNA expression between pregnancies with severe recipient cardiomyopathy and those with preserved cardiac function. A stringent q value of <.0025 was used to determine differential microRNA expression. Random forest plots identified the top 3 microRNAs that separated the 2 groups, and hierarchical cluster analysis was used to determine if these microRNAs properly segregated the samples according to their clinical groups.

RESULTS

A total of 14 amniotic fluid samples from pregnancies with twin-twin transfusion syndrome with severe cardiomyopathy were compared with samples from 12 twin-twin transfusion syndrome control cases with preserved cardiac function. A total of 110 microRNAs were identified in the amniotic fluid samples. Twenty microRNAs were differentially expressed, and the top 3 differentiating microRNAs were hsa-miR-200c-3p, hsa-miR-17-5p, and hsa-miR-539-5p. Hierarchical cluster analysis based on these top 3 microRNAs showed a strong ability to differentiate severe cardiomyopathy cases from controls. The top 3 microRNAs were used to investigate the sensitivity and specificity of these microRNAs to differentiate between the 2 groups with a receiver operating characteristic curve demonstrating sensitivity and specificity of 80.8%. All 20 differentially expressed microRNAs were down-regulated in the group with severe cardiomyopathy.

CONCLUSION

Amniotic fluid microRNAs demonstrated differential expression between twin-twin transfusion syndrome recipient fetuses with severe cardiomyopathy and those without and have the potential to be important biomarkers of disease severity in this population.

Circulating Nucleic Acids in Maternal Plasma and Serum in Pregnancy Complications: Are They Really Useful in Clinical Practice? A Systematic Review

OBJECTIVE

A systematic review was carried out to summarize the available evidence to assess whether circulating nucleic acids in maternal plasma and serum (CNAPS) have the potential to serve as extra and independent markers for the prediction and/or progression monitoring of the most common and severe complications of pregnancy, including preeclampsia, intrauterine growth restriction, preterm delivery, morbidly adherent placenta, gestational diabetes, antiphospholipid syndrome, threatened abortion, intrahepatic cholestasis of pregnancy, and hyperemesis gravidarum.

METHOD

A comprehensive literature search of the MEDLINE (PubMed), EMBASE, and ISI Web of Knowledge databases was conducted to identify relevant studies that included amounts of CNAPS in the abovementioned pregnancy complications.

RESULTS

Eighty-three studies met the eligibility criteria. The vast majority of studies were conducted on the quantity of total circulating cell free DNA (cfDNA) and cell free fetal DNA (cffDNA), and some were conducted on messenger RNA (mRNA) species. A few studies have instead evaluated the cell free DNA fetal fraction (cfDNAff), but only in a limited number of pregnancy complications. Despite the growing interest and the abundance of the papers available, little information is available for other new CNAPS, including microRNA (miRNA), long noncoding RNA (lncRNA), mitochondrial DNA (mtDNA), and circular RNA.

CONCLUSION

Due to the heterogeneity of the populations enrolled, the scarcity of the studies that adjusted the CNAPS values for possible confounding factors, and the difficulty in interpreting the published data, no conclusion regarding the statistical robustness and clinical relevance of the data can be made at present. If assayed at the third trimester, the CNAPS have, however, shown better performance, and could be used in populations already at risk of developing complications as suggested by the presence of other clinical features. Other CNAPS, including miRNA, are under investigation, especially for the screening of gestational diabetes mellitus, but no data about their clinical utility are available. Circulating DNA (cfDNA, cffDNA, and cfDNAff) and mRNA have not been properly evaluated yet, especially in patients asymptomatic early in pregnancy but who developed complications later, perhaps because of the high cost of these techniques and the availability of other predictors of pregnancy complications (biochemical, biophysical, and ultrasound markers). Therefore, from the analysis of the data, the positive predictive value is not available. As regards the new CNAPS, including miRNA, there are still no sufficient data to understand if they can be promising markers for pregnancy complications monitoring and screening, since CNAPS are statistically weak and expensive. It is reasonable to currently conclude that the use of the CNAPS in clinical practice is not recommended.

Leptin and adiponectin concentrations in infants with low birth weight: relationship with maternal health and postnatal growth

Health in pregnancy and infancy can affect the risk of chronic non-communicable diseases. We aimed to describe leptin and adiponectin concentrations in low birth weight (LBW) infants and identify possible associations with maternal nutritional status, adequacy for gestational age, nutritional recovery, and current dietary intake. A cross-sectional study with LBW infants (9-12 months) including maternal background and pre-pregnancy nutritional condition was performed. From the Infants: anthropometry at birth and current was expressed as z-score (weight: WAZ, length, head circumference), nutritional recovery, dietary intake, leptin, and adiponectin blood concentrations. The mean age of the 54 infants was 10.0 ± 1.5 months, 32 (59.3%) were female, 36 (66.7%) preterm, 23 (42.6%) small for gestational age (SGA), and 25 pregnancies (46.3%) were twin. Almost all (98%) of the infants intake energy and protein above the recommendation, and 47 (87.6%) consumed ultra-processed foods. At the time of the assessment, 8 (14.8%) were overweight and 4 (7.4%) had short stature. SGA infants showed faster weight recovery (WAZ 1.54; 95% CI 1.17, 1.91; p = 0.001), higher leptin's concentration (3.0 ng/ml (1.7, 3.0) versus 1.6 ng/ml (0.9, 2.6); p = 0.032)), and leptin/adiponectin ratio (0.13 ± 0.08 versus 0.07 ± 0.07; p = 0.018). The pre-gestational BMI was a modifier of the effect of WAZ on leptin levels (p = 0.027) in LBW infants. Higher pre-gestational BMI increased the effect of WAZ variation (birth and current) on leptin levels. Concluding, LBW infants showed early changes in leptin and adiponectin concentrations, influenced by maternal (pre-gestational BMI), intrauterine (gestational age adequacy - SGA), and postnatal weight gain. This combination of factors may increase the risk of NCD for this group of children.

An Insight on the Role of Altered Function and Expression of Exosomes and MicroRNAs in Female Reproductive Diseases

Exosomes are small bilayer-lipid membrane vesicles secreted by living cells that are able to transfer regulatory molecules and genetic information from one cell to another. These vesicles are enriched with several nucleic acids including mRNAs, microRNAs (miRNAs), other non-coding RNAs, as well as proteins and lipids. Alterations in the exosomal content and functions are observed in numerous reproductive diseases in both animals and human cases. MicroRNAs, a class of small endogenous RNA molecules, can negatively regulate gene expression at the post-transcription level. Aberrant microRNA expression has been reported in multiple human reproductive diseases such as polycystic ovary syndrome, preeclampsia, uterine leiomyomata, ovarian cancer, endometriosis, and Asherman's syndrome. This study focuses to review recent research on alterations of microRNA expression and the role of exosomes in female reproductive diseases. It has been demonstrated that exosomes may be a potential therapeutic approach in various female reproductive diseases. In addition, changes in expression of microRNAs act as molecular biomarkers for diagnosis of several reproductive diseases in women, and regulation of their expression can potentially reduce infertility.

Association of Circulating miRNA Expression with Preeclampsia, Its Onset, and Severity

MicroRNAs (miRNAs) are one of the important regulators of cellular functions fundamental for healthy pregnancy processes, including angiogenesis and differentiation of trophoblast cells, and their deregulation could be implicated in the pathogenesis of pregnancy complications, including preeclampsia (PE). The aim of this study was to assess the association of miRNA expression in plasma samples with PE, its onset, and severity. Our study enrolled 59 pregnant women, 27 in the preeclamptic study group and 32 in the control group with physiological pregnancy. Preeclamptic pregnancies were divided into subgroups based on the severity and onset of disease. Relative expression of miR-21-5p, miR-155-5p, miR-210-5p, miR-16-5p, and miR-650 isolated from plasma samples was analysed by quantitative real-time PCR and normalised to experimentally established reference genes. Our results revealed upregulation of miR-21-5p (1.16-fold change, p = 0.0015), miR-155-5p (1.62-fold change, p = 0.0005) in preeclamptic pregnancies, compared to controls. Overexpression of these two miRNAs was observed, especially in subgroups of severe and late-onset PE compared to healthy pregnancies. Although we hypothesised that the expression level of studied miRNAs could vary between PE subtypes (mild vs. severe, early onset vs. late-onset), no obvious differences were detected. In conclusion, our study could contribute to the large-scale studies for the identification of non-invasive biomarkers for PE detection to improve outcomes for women and their new-borns.

Pre-eclampsia predictive ability of maternal miR-125b: a clinical and experimental study

Pre-eclampsia (PE) is a systemic maternal syndrome affecting 2-8% of pregnancies worldwide and involving poor placental perfusion and impaired blood supply to the foetus. It manifests after the 20th week of pregnancy as new-onset hypertension and substantial proteinuria and is responsible for severe maternal and newborn morbidity and mortality. Identifying biomarkers that predict PE onset prior to its establishment would critically help treatment and attenuate outcome severity. MicroRNAs are ubiquitous gene expression modulators found in blood and tissues. Trophoblast cell surface antigen (Trop)-2 promotes cell growth and is involved in several cancers. We assessed the PE predictive ability of maternal miR-125b in the first trimester of pregnancy by measuring its plasma levels in women with normal pregnancies and with pregnancies complicated by PE on the 12th week of gestation. To gain insight into PE pathogenesis we investigated whether Trop-2 is targeted by miR-125b in placental tissue. Data analysis demonstrated a significant association between plasma miR-125b levels and PE, which together with maternal body mass index before pregnancy provided a predictive model with an area under the curve of 0.85 (95% confidence interval, 0.70-1.00). We also found that Trop-2 is a target of miR-125b in placental cells; its localization in the basal part of the syncytiotrophoblast plasma membrane suggests a role for it in the early onset of PE. Altogether, maternal miR-125b proved a promising early biomarker of PE, suggesting that it may be involved in placental development through its action on Trop-2 well before the clinical manifestations of PE.

Inhibition of microRNA-149 protects against recurrent miscarriage through upregulating RUNX2 and activation of the PTEN/Akt signaling pathway

AIM

Recently, microRNA-149 (miR-149) has been indicated to act as an oncogene or a tumor suppressor in various malignant tumors, while its inner mechanisms in recurrent miscarriage (RM) are still in infancy. Therein, this study intends to decode the mechanism of miR-149 in RM.

METHODS

miR-149 and RUNX2 expression in the chorionic tissues of normal pregnant women and RM patients were first examined, and the correlation between miR-149 and RUNX2 was analyzed. Subsequently, miR-149 was upregulated in HTR-8 cells or downregulated in BEWO cells, and then the changes in biological functions of trophoblasts in RM were detected. Furthermore, the expression of PTEN/Akt signaling pathway-related factors in trophoblasts was detected by western blot analysis.

RESULTS

miR-149 expression was increased while RUNX2 expression was suppressed in RM patients, and miR-149 was negatively correlated with RUNX2. Overexpressed miR-149 induced cell apoptosis and inhibited cell activity, while reduced miR-149 in trophoblasts contributed to opposite experimental results. Moreover, miR-149 promoted the expression of PTEN and inhibited Akt phosphorylation by targeting RUNX2, thereby inhibiting trophoblast activity and promoting their apoptosis.

CONCLUSION

Our study demonstrates that miR-149 knockdown halted the RM development through upregulating RUNX2 and activation of the PTEN/Akt signaling pathway.

Expression levels of maternal plasma microRNAs in preeclamptic pregnancies

The present study aimed to identify the differential expression profiles of microRNAs in the plasma between patients with preeclampsia (PE) and healthy pregnancies using quantitative real-time PCR. The expression profiles of 32 miRNAs in maternal plasma from 31 patients with PE and 32 healthy pregnancies were evaluated. The expression levels of eight miRNAs including miR-210, miR-375, miR-197-3p, miR-132-3p, miR-29a-3p, miR-328, miR-24-3p, and miR-218-5p were significantly upregulated and the expression levels of three miRNAs, including miR-302b-3p, miR-191-5p, and miR-17-5p, were significantly downregulated in patients with preeclampsia when compared to healthy pregnant women. In conclusion, we identified 11 miRNAs that may be potential biomarkers for non-invasive diagnosis and a pivotal role in the prediction of PE. Considering the small cohort of patients, further studies with larger samples from different gestational stages are necessary to confirm our findings.IMPACT STATEMENTWhat is already known on this subject? The alterations in the release pattern of placenta-specific miRNAs detected in maternal serum have been found to be associated with pregnancy-related complications such as preeclampsia (PE).What do the results of this study add? In the present study, the release pattern of seven miRNAs had consistency and two of them had inconsistency with previous researches. Moreover, two novel miRNAs were also defined to demonstrate the interrelationship between PE and miRNAs.What are the implications of these findings for clinical practice and/or future research? The identification of 11 miRNAs that may be potential biomarkers for non-invasive diagnosis and a pivotal role in the prediction of PE. Considering the small cohort of patients, further studies with larger samples from different gestational stages are necessary to confirm our findings.

Circulating microRNAs as biomarkers for diagnosis and prediction of preeclampsia: A systematic review and meta-analysis

OBJECTIVE

We carried out a meta-analysis to quantitatively summarize the overall diagnostic and predictive effects of circulating microRNAs in diagnosis and prediction of preeclampsia, respectively.

STUDY DESIGN

We screened selected databases and systematically retrieved articles until September 20th, 2019 for analysis. After literature screening and data extraction, we firstly conducted quality assessment according to QUADAS-2 score system. And then the pooled diagnostic and predictive parameters were calculated using a bivariate random-effect meta-analysis model. We used threshold effect analysis and subgroup analysis to identify the sources of heterogeneity. The clinical utility was validated through the Fagan's Nomogram. Sensitivity analysis was performed to assess the reliability of each included study, and we evaluated publication bias with the Deeks' funnel plot asymmetry test.

RESULTS

The meta-analysis included 8 articles comprising 273 preeclampsia patients and 343 normal pregnancies. Pooled results of diagnostic values of 5 articles indicated a sensitivity of 0.88 (95 %CI: 0.80-0.93), specificity of 0.87 (95 %CI: 0.78-0.92) and diagnostic odds ratio of 50.24 (95 %CI: 21.28-118.62). The pooled sensitivity, specificity, DOR of circulating microRNAs for predicting preeclampsia of asymptomatic pregnancies were 0.61 (95 %CI: 0.55-0.68), 0.78 (95 %CI: 0.72-0.83) and 5.7 (95 %CI: 3.7-8.7) across other 3 articles. Subgroup analysis revealed that non-plasma specimen type, non-U6 reference gene and non-Asian had better diagnostic value while due to limited data, we did not conduct a subgroup analysis of predictive value.

CONCLUSIONS

Circulating miRNAs distinguish patients with preeclampsia from controls with relatively high diagnostic and predictive accuracy. Then we conclude that circulating miRNAs could be a useful screening tool to diagnose and predict preeclampsia. However, its utility should be judged with caution and large-sample prospective studies are warranted to explore if its implementation improves maternal and neonatal outcomes.

Extraction of Small RNAs by Titanium Dioxide Nanofibers

MicroRNAs (miRNAs) are small RNAs, that bind to mRNA targets and regulate their translation. Functional study of miRNAs and exploration of their utility as disease markers require miRNA extraction from biological samples, which contain large amounts of interfering compounds for downstream RNA identification and quantification. The most common extraction methods employ either silica columns or TRIzol reagent, but these approaches afford low recovery for small RNAs, possibly due to their short strand lengths. Here, we describe the fabrication of titanium dioxide nanofibers and the optimal extraction conditions to improve miRNA recovery from biological buffers, cell lysate, and serum.

Placental microRNAs: Responders to environmental chemicals and mediators of pathophysiology of the human placenta

MicroRNAs (miRNAs) are epigenetic modifiers that play an important role in the regulation of the expression of genes across the genome. miRNAs are expressed in the placenta as well as other organs, and are involved in several biological processes including the regulation of trophoblast differentiation, migration, invasion, proliferation, apoptosis, angiogenesis and cellular metabolism. Related to their role in disease process, miRNAs have been shown to be differentially expressed between normal placentas and placentas obtained from women with pregnancy/health complications such as preeclampsia, gestational diabetes mellitus, and obesity. This dysregulation indicates that miRNAs in the placenta likely play important roles in the pathogenesis of diseases during pregnancy. Furthermore, miRNAs in the placenta are susceptible to altered expression in relation to exposure to environmental toxicants. With relevance to the placenta, the dysregulation of miRNAs in both placenta and blood has been associated with maternal exposures to several toxicants. In this review, we provide a summary of miRNAs that have been assessed in the context of human pregnancy-related diseases and in relation to exposure to environmental toxicants in the placenta. Where data are available, miRNAs are discussed in their context as biomarkers of exposure and/or disease, with comparisons made across-tissue types, and conservation across studies detailed.

Genome-wide miRNA profiling in plasma of pregnant women with down syndrome fetuses

Down syndrome (DS) is one of the most common causes of intellectual disability and new approaches allowing its rapid and effective prenatal detection are being explored. In this study, we investigated the diagnostic potential of plasma microRNAs (miRNAs). This study builds upon our previous study in DS placentas, where seven miRNAs were found to be significantly up-regulated. A total of 70 first-trimester plasma samples from pregnant women were included in the present study (35 samples with DS fetuses; 35 with euploid fetuses). Genome-wide miRNA profiling was performed in the pilot study using Affymetrix GeneChip™ miRNA 4.1 Array Strips (18 samples). Selected miRNAs were then analysed in the validation study using quantitative reverse transcription PCR (RT-qPCR; 52 samples). Based on the current pilot study results (12 miRNAs), our previous research on chorionic villi samples (7 miRNAs) and the literature (4 miRNAs), a group of 23 miRNAs was selected for the validation study. Although the results of the pilot study were promising, the validation study using the more sensitive RT-qPCR technique and a larger group of samples revealed no significant differences in miRNA profiles between the compared groups. Our results suggest that testing of the first-trimester plasma miRNAs is probably not suitable for non-invasive prenatal testing (NIPT). Different results could be theoretically achieved at later gestational ages; however, such a result probably would have limited use in clinical practice.

A Data-Driven Review of the Genetic Factors of Pregnancy Complications

Over the recent years, many advances have been made in the research of the genetic factors of pregnancy complications. In this work, we use publicly available data repositories, such as the National Human Genome Research Institute GWAS Catalog, HuGE Navigator, and the UK Biobank genetic and phenotypic dataset to gain insights into molecular pathways and individual genes behind a set of pregnancy-related traits, including the most studied ones—preeclampsia, gestational diabetes, preterm birth, and placental abruption. Using both HuGE and GWAS Catalog data, we confirm that immune system and, in particular, T-cell related pathways are one of the most important drivers of pregnancy-related traits. Pathway analysis of the data reveals that cell adhesion and matrisome-related genes are also commonly involved in pregnancy pathologies. We also find a large role of metabolic factors that affect not only gestational diabetes, but also the other traits. These shared metabolic genes include IGF2, PPARG, and NOS3. We further discover that the published genetic associations are poorly replicated in the independent UK Biobank cohort. Nevertheless, we find novel genome-wide associations with pregnancy-related traits for the FBLN7, STK32B, and ACTR3B genes, and replicate the effects of the KAZN and TLE1 genes, with the latter being the only gene identified across all data resources. Overall, our analysis highlights central molecular pathways for pregnancy-related traits, and suggests a need to use more accurate and sophisticated association analysis strategies to robustly identify genetic risk factors for pregnancy complications.

Pregnancy-associated cardiac dysfunction and the regulatory role of microRNAs

Many crucial cardiovascular adaptations occur in the body during pregnancy to ensure successful gestation. Maladaptation of the cardiovascular system during pregnancy can lead to complications that promote cardiac dysfunction and may lead to heart failure (HF). About 12% of pregnancy-related deaths in the USA have been attributed to HF and the detrimental effects of cardiovascular complications on the heart can be long-lasting, pre-disposing the mother to HF later in life. Indeed, cardiovascular complications such as gestational diabetes mellitus, preeclampsia, gestational hypertension, and peripartum cardiomyopathy have been shown to induce cardiac metabolic dysfunction, oxidative stress, fibrosis, apoptosis, and diastolic and systolic dysfunction in the hearts of pregnant women, all of which are hallmarks of HF. The exact etiology and cardiac pathophysiology of pregnancy-related complications is not yet fully deciphered. Furthermore, diagnosis of cardiac dysfunction in pregnancy is often made only after clinical symptoms are already present, thus necessitating the need for novel diagnostic and prognostic biomarkers. Mounting data demonstrates an altered expression of maternal circulating miRNAs during pregnancy affected by cardiovascular complications. Throughout the past decade, miRNAs have become of growing interest as modulators and biomarkers of pathophysiology, diagnosis, and prognosis in cardiac dysfunction. While the association between pregnancy-related cardiovascular complications and cardiac dysfunction or HF is becoming increasingly evident, the roles of miRNA-mediated regulation herein remain poorly understood. Therefore, this review will summarize current reports on pregnancy-related cardiovascular complications that may lead to cardiac dysfunction and HF during and after pregnancy in previously healthy women, with a focus on the pathophysiological role of miRNAs.

miR-338-5p Targets Epidermal Growth Factor-Containing Fibulin-Like Extracellular Matrix Protein 1 to Inhibit the Growth and Invasion of Trophoblast Cells in Selective Intrauterine Growth Restriction

Selective intrauterine growth restriction (sIUGR) is a disorder of monochorionic (MC) twin pregnancies. However, the underlying mechanism remains largely unknown. Trophoblast cells are the major component of the placenta. Dysfunction of trophoblast cells is associated with placental dysfunction. Our previous study identified miR-338-5p is downregulated in placenta tissues sharing larger twins of sIUGR. In the present study, we aimed to investigate the role of miR-338-5p in trophoblast cells and explored its target. Our results further indicated that miR-338-5p was downregulated in placental tissues supporting larger twins of sIUGR, whereas epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) was upregulated. Moreover, miR-338-5p overexpression suppressed the growth and invasion of trophoblast cells. Importantly, results from luciferase reporter assay demonstrated that miR-338-5p bound on the 3'-UTR of EFEMP1. miR-338-5p suppressed the growth and invasion of trophoblast cells via targeting EFEMP1. Further, miR-338-5p/EFEMP1 might disrupt the function of trophoblast cells via inhibiting the phosphorylation of AKT.

Expression Profile of the Chromosome 14 MicroRNA Cluster (C14MC) Ortholog in Equine Maternal Circulation throughout Pregnancy and Its Potential Implications

Equine chromosome 24 microRNA cluster (C24MC), the ortholog of human C14MC, is a pregnancy-related miRNA cluster. This cluster is believed to be implicated in embryonic, fetal, and placental development. The current study aimed to characterize the expression profile of this cluster in maternal circulation throughout equine gestation. The expression profile of miRNAs belonging to this cluster was analyzed in the serum of non-pregnant (diestrus), pregnant (25 d, 45 d, 4 mo, 6 mo, 10 mo), and postpartum mares. Among the miRNAs examined, 11 miRNAs were differentially expressed across the analyzed time-points. Four of these miRNAs (eca-miR-1247-3p, eca-miR-134-5p, eca-miR-382-5p, and eca-miR-433-3p) were found to be enriched in the serum of pregnant mares at Day 25 relative to non-pregnant mares. To further assess the accuracy of these miRNAs in differentiating pregnant (25 d) from non-pregnant mares, receiver operating characteristic (ROC) analysis was performed for each of these miRNAs, revealing that eca-miR-1247-3p and eca-miR-134-5p had the highest accuracy (AUC_ROC = 0.92 and 0.91, respectively; p < 0.05). Moreover, eca-miR-1247-3p, eca-miR-134-5p, eca-miR-409-3p, and eca-miR-379-5p were enriched in the serum of Day 45 pregnant mares. Among those miRNAs, eca-miR-1247-3p and eca-miR-409-3p retained the highest accuracy as shown by ROC analysis. GO analysis revealed that these miRNAs are mainly implicated in nervous system development as well as organ development. Using in situ hybridization, we localized eca-miR-409-3p in the developing embryo (25 d) and extra-embryonic membranes (25 and 45 d). In conclusion, the present study is the first to elucidate the circulating maternal profile of C24MC-associated miRNAs throughout pregnancy and to suggest that serum eca-miR-1247-3p, eca-miR-134-5p, and eca-miR-409-3p could be used as pregnancy-specific markers during early gestation (25 and 45 d). Overall, the high abundance of these embryo-derived miRNAs in the maternal circulation suggests an embryo-maternal communication during the equine early pregnancy.

Comprehensive analysis of the differential expression profile of microRNAs in missed abortion

To screen the key circulating microRNAs (miRNAs) involved in missed abortion (MA) and explore their role in MA process. We examined the miRNA profile from the serum of three MA patients and three early pregnancy induced abortion patients (controls) by next-generation sequencing. We analyzed the target genes of the differentially expressed (DE) miRNAs to analyze the function and pathway enrichment using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, respectively. We validated five candidate miRNAs by real time-qPCR. Integrated miRNA-mRNA-pathway network analysis was performed to show the interaction network of the candidate miRNAs and their target genes of interest with the involved pathways. It was observed that 227 miRNAs were differently expressed between the MA group and the early pregnancy control group, with 58 miRNAs downregulated and 169 miRNAs upregulated in the MA group. Real-time qPCR results revealed that expression of the five candidate miRNAs, namely hsa-miR-22-3p, hsa-miR-145-3p, hsa-miR-107, hsa-miR-361-3p, and hsa-miR-378c, was consistent with the miRNA data obtained by sequencing. Integrated miRNA-mRNA-pathway network analysis illustrated that target genes of the candidate miRNAs were mainly involved in the PI3K-Akt signaling pathway, HIF-1 signaling pathway, and VEGF signaling pathway, which would have potential significance in pregnancy and MA. We are the first to reveal the DE miRNAs involved in MA and illustrate their functional interaction network. These results might provide potential circulating biomarkers and new therapeutic targets for MA.

Role of cell free microRNA-19a and microRNA-19b in gestational diabetes mellitus patients

Gestational diabetes mellitus (GDM) is associated with adverse pregnancy outcomes in pregnant women and it's prevalence is increasing worldwide. A total 100 cases of GDM and 100 healthy controls were included in a study and blood samples were collected in plain vials from all study participant. Difference among several variables which included BMI, glycemia, insulinaemia, HbA1c, total cholesterol, triglycerides, urinary albumin were compared between GDM cases and controls and were found to be statistically significant (p < 0.0001). Additionally, GDM cases showed 4.0 fold increase in miRNA-19a and 4.7 mean increase in miRNA-19b expression compared to healthy control individuals. A positive correlation was observed between miRNA-19a and miRNA-19b among GDM cases. However the correlation coefficient was 0.13 between miRNA-19a and miRNA-19b. This suggested that with the increase in miRNA-19a, miRNA-19b also increased. The findings of this study concludes that an increase in microRNA-19a and microRNA-19b is observed in GDM cases and could be linked with increased risk factor for worsening of the disease. MicroRNA-19a and 19b have been linked to alcoholism and smoking and could also be the factors in GDM.

MicroRNAs: Small molecules with a large impact on pre-eclampsia

As critical mediators in biological processes, microRNAs (miRNAs) which are small and endogenous noncoding RNAs have been associated with disease progression, cell proliferation, and development. Pre-eclampsia (PE), a pregnancy-related disorder with no early markers or symptoms is recognized as the main reason for fetal and maternal mortality and morbidity in the initial steps or even during pregnancy, worldwide. Clinical symptoms usually appear in the third trimester of the pregnancy. Although numerous research have unraveled several aspects of placenta development abnormalities associated with abnormal trophoblastic invasion and angiogenesis modification, many questions about the PE pathogenesis remains unanswered. A large number of studies have shown the important role of miRNAs as potential biomarkers in the PE prognosis and diagnosis. Here, the latest investigations about the PE and placental miRNAs expression, as well as, the crucial role of miRNA molecules including miR-210 and miR-155 which are deregulated in patients with PE, will be argued.

Blood-based biomarkers in the maternal circulation associated with fetal growth restriction

Fetal growth restriction (FGR) is associated with threefold to fourfold increased risk of stillbirth. Identifying FGR, through its commonly used surrogate-the small-for-gestational-age (SGA, estimated fetal weight and/or abdominal circumference <10th centile) fetus-and instituting fetal surveillance and timely delivery decrease stillbirth risk. Methods available to clinicians for antenatal identification of SGA fetuses have surprisingly poor sensitivity. About 80% of cases remain undetected. Measuring the symphysis-fundal height detects only 20% of SGA fetuses, and even universal third trimester ultrasound detects, at best, 57% of those born SGA. There is an urgent need to find better ways to identify this at-risk cohort. This review summarises efforts to identify molecular biomarkers (proteins, metabolites, or ribonucleic acids) that could be used to better predict FGR. Most studies examining potential biomarkers to date have utilised case-control study designs without proceeding to validation in independent cohorts. To develop a robust test for FGR, large prospective studies are required with a priori validation plans and cohorts. Given that current clinical care detects 20% of SGA fetuses, even a screening test with ≥60% sensitivity at 90% specificity could be clinically useful, if developed. This may be an achievable aspiration. If discovered, such a test may decrease stillbirth.

MicroRNA changes in maternal serum from pregnancies complicated by twin-twin transfusion syndrome: A discovery study

OBJECTIVE

MicroRNAs (miRNAs) are used as biomarkers in cardiovascular disease and cancer. miRNAs are involved in placental development but have not previously been investigated in twin-twin transfusion syndrome (TTTS). Our aim is to explore the miRNA profile of TTTS pregnancies.

METHOD

Initial miRNA profiling was performed using a reverse transcription polymerase chain reaction (RT-PCR) panel on maternal serum samples taken from five women prior to fetoscopic laser ablation for TTTS and compared with serum samples from five women with uncomplicated monochorionic diamniotic twin pregnancies. Validation RT-PCR was performed in an additional cohort of eight TTTS pregnancies and eight uncomplicated pregnancies.

RESULTS

Median gestational age at sampling in the TTTS and control groups was 20+0  weeks (interquartile range [IQR], 19+4 -20+0 ) and 20+2  weeks (IQR, 20+0 -20+2 ), respectively. All samples passed quality control. One control sample was excluded as a biological outlier. Thirty-one of 752 miRNAs were significantly different: 17 were upregulated and 14 downregulated in the TTTS group, although they did not remain significant following Benjamini-Hochberg correction for multiple testing. The six miRNAs chosen for validation demonstrated no significant difference.

CONCLUSION

This is the first study to investigate miRNA changes in TTTS pregnancies. We did not demonstrate a statistically significant difference in miRNAs in TTTS pregnancies, but further investigation is required.

Imprinted MicroRNA Gene Clusters in the Evolution, Development, and Functions of Mammalian Placenta

In mammals, the expression of a subset of microRNA (miRNA) genes is governed by genomic imprinting, an epigenetic mechanism that confers monoallelic expression in a parent-of-origin manner. Three evolutionarily distinct genomic intervals contain the vast majority of imprinted miRNA genes: the rodent-specific, paternally expressed C2MC located in intron 10 of the Sfmbt2 gene, the primate-specific, paternally expressed C19MC positioned at human Chr.19q13.4 and the eutherian-specific, maternally expressed miRNAs embedded within the imprinted Dlk1-Dio3 domains at human 14q32 (also named C14MC in humans). Interestingly, these imprinted miRNA genes form large clusters composed of many related gene copies that are co-expressed with a marked, or even exclusive, localization in the placenta. Here, we summarize our knowledge on the evolutionary, molecular, and physiological relevance of these epigenetically-regulated, recently-evolved miRNAs, by focusing on their roles in placentation and possibly also in pregnancy diseases (e.g., preeclampsia, intrauterine growth restriction, preterm birth).

Down-regulated miR-149-5p contributes to preeclampsia via modulating endoglin expression

OBJECTIVE

Endoglin is expressed in human placenta and plays an important role in the pathogenesis of preeclampsia. Dysregulation of microRNAs in placental tissues has been recently suggested to be involved in the pathogenesis of preeclampsia. Until now, few studies have shed light on the correlation between endoglin and microRNAs, the latter of which may regulate the expression of ENG, a gene encoding endoglin, in placenta. In this study, we aim to investigate the regulation of ENG by microRNAs.

STUDY DESIGN

We located the microRNAs that might regulate the expression of ENG. Candidate microRNAs were tested if they had an impact on trophoblast function.

MAIN OUTCOME MEASURES

We compared endoglin expression between normotensive and preeclamptic placentas by using immunohistochemistry and real-time PCR. Downregulated microRNAs in preeclamptic placenta were revealed from a literature review. A bioinformatics assay was performed to predict those that might target ENG. Real-time PCR, Western blotting and dual luciferase assay were used to verify the targeting. The effects of the microRNAs on trophoblasts were evaluated by transwell invasion assay.

RESULTS

The endoglin level was significantly higher in preeclamptic placenta than in normotensive placenta. ENG was validated as the direct target of miR-149-5p and was inversely correlated with it. MiR-149-5p promoted the invasion of trophoblast cells, and this promotion was abrogated by the overexpression of ENG.

CONCLUSIONS

Our findings highlight the importance of miR-149-5p in the pathogenesis of preeclampsia and provide new insight into the development of the disease.

Placental miR-340 mediates vulnerability to activity based anorexia in mice

Anorexia nervosa (AN) is a devastating eating disorder characterized by self-starvation that mainly affects women. Its etiology is unknown, which impedes successful treatment options leading to a limited chance of full recovery. Here, we show that gestation is a vulnerable window that can influence the predisposition to AN. By screening placental microRNA expression of naive and prenatally stressed (PNS) fetuses and assessing vulnerability to activity-based anorexia (ABA), we identify miR-340 as a sexually dimorphic regulator involved in prenatal programming of ABA. PNS caused gene-body hypermethylation of placental miR-340, which is associated with reduced miR-340 expression and increased protein levels of several target transcripts, GR, Cry2 and H3F3b. MiR-340 is linked to the expression of several nutrient transporters both in mice and human placentas. Using placenta-specific lentiviral transgenes and embryo transfer, we demonstrate the key role miR-340 plays in the mechanism involved in early life programming of ABA.

Anorexia nervosa is characterised by self-starvation but its etiology is not completely understood. Here the authors describe how prenatal stress can induce activity-based anorexia in the offspring during early adulthood by upregulating miR-340 expression in the placenta that affects expression of nutrient transporters.

Circulating microRNAs as biomarkers of disease and typification of the atherothrombotic status in antiphospholipid syndrome

We aimed to identify the plasma miRNA profile of antiphospholipid syndrome (APS) patients and to investigate the potential role of specific circulating miRNAs as non-invasive disease biomarkers. Ninety APS patients and 42 healthy donors were recruited. Profiling of miRNAs by PCR-array in plasma of APS patients identified a set of miRNAs differentially expressed and collectively involved in clinical features. Logistic regression and ROC analysis identified a signature of 10 miRNA ratios as biomarkers of disease. In addition, miRNA signature was related to fetal loss, atherosclerosis, and type of thrombosis, and correlated with parameters linked to inflammation, thrombosis, and autoimmunity. Hard clustering analysis differentiated 3 clusters representing different thrombotic risk profile groups. Significant differences between groups for several miRNA ratios were found. Moreover, miRNA signature remained stable over time, demonstrated by their analysis three months after the first sample collection. Parallel analysis in two additional cohorts of patients, including thrombosis without autoimmune disease, and systemic lupus erythematosus without antiphospholipid antibodies, each displayed specific miRNA profiles that were distinct from those of APS patients. In vitro, antiphospholipid antibodies of IgG isotype promoted deregulation in selected miRNAs and their potential atherothrombotic protein targets in monocytes and endothelial cells. Taken together, differentially expressed circulating miRNAs in APS patients, modulated at least partially by antiphospholipid antibodies of IgG isotype, might have the potential to serve as novel biomarkers of disease features and to typify patients’ atherothrombotic status, thus constituting a useful tool in the management of the disease.

Reference values for circulating pregnancy-associated microRNAs in maternal plasma and their clinical usefulness in uncomplicated pregnancy and hypertensive disorder of pregnancy

AIM

The aim of this study was to establish the reference values for circulating pregnancy-associated placental microRNAs in maternal plasma and clarify their clinical significance in patients with hypertensive disorder of pregnancy (HDP).

METHODS

Blood samples were collected from 145 women with uncomplicated pregnancies (24, 26, 31 and 32 women at 12, 23, 30 and 36 weeks of gestation, respectively, and 32 women 1 day after delivery). Plasma concentrations of pregnancy-associated placental microRNAs (miR-515-3p, miR-517a, miR-517c and miR-518b) were measured by quantitative real-time reverse-transcription polymerase chain reaction. Reference values for each microRNA were determined by the line of best fit and 95% prediction interval and are expressed as logarithmic transformation. To clarify the clinical significance of these reference values, we measured the plasma concentrations of pregnancy-associated microRNAs in a different population comprising 33 pregnant women with HDP and 44 women with uncomplicated pregnancies.

RESULTS

Reference values for circulating pregnancy-associated placental microRNAs on chromosome 19 miRNA clusters showed an increasing tendency as pregnancy progressed and decreased significantly 1 day after delivery (P < 0.05). The sensitivity and specificity of each reference value were 57.6% and 93.2% for miR-515-3p, 63.6% and 75.0% for miR-517a, 75.8% and 79.5% for miR-517c and 63.6% and 75.0% for miR-518b, respectively. The positive and negative predictive values of each reference value were 86.4% and 74.5% for miR-515-3p, 65.6% and 73.3% for miR-517a, 73.5% and 81.4% for miR-517c and 65.6% and 73.3% for miR-518b, respectively.

CONCLUSION

Establishing the reference values for circulating pregnancy-associated placental microRNAs in maternal plasma could be useful for the evaluation of HDP.

MicroRNA expression profiling in placenta and maternal plasma in early pregnancy loss

Early pregnancy loss (EPL), also termed early miscarriage, is determined as the unintentional expulsion of an embryo or fetus prior to the 12th week of gestation. EPL frequency is ~15% in pregnancies. Fetal development and growth is associate with placental function and vessel development; therefore, the placental genome would represent a useful miscarriage model for (epi)genetic and genomic studies. An important factor of placental development and function is epigenetic regulation of gene expression. microRNAs (miRNAs) are the primary epigenetic regulators which have an important role in placental development and function. In the present study, maternal plasma and villous tissue were collected from 16 EPL cases in 6th-8th gestational weeks (GWs) and 8 abortions (control group) in 6th-8th GWs. Detection of the differences in miRNA expression was performed using microarrays and dysregulated miRNAs were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). miRNA microarray findings revealed that four miRNAs, including hsa-miRNA (miR)-125a-3p, hsa-miR-3663-3p, hsa-miR-423-5p and hsa-miR-575 were upregulated in tissue samples. In maternal plasma, two miRNAs (hsa-let-7c, hsa-miR-122) were upregulated and one miRNA (hsa-miR-135a) was downregulated. A total of 6 out of 7 dysregulated miRNAs were validated using RT-qPCR. The target genes of these dysregulated miRNAs were detected using the GeneSpring database. The aim of the present study was to detect dysregulated miRNAs in maternal plasma and villous cells and identify the target genes of dysregulated miRNAs and their associated pathways. The target gene analyses have revealed that the affected genes are primarily associated with cell migration, proliferation, implantation, adhesion, angiogenesis and differentiation and all are involved with EPL pathogenesis. Therefore, the present study may contribute to the understanding of the molecular mechanisms which lead to EPL.

Extraction of microRNAs from biological matrices with titanium dioxide nanofibers

MicroRNAs (miRNAs) are small RNAs that bind to mRNA targets and regulate their translation. A functional study of miRNAs and exploration of their utility as disease markers require miRNA extraction from biological samples, which contain large amounts of interfering compounds for downstream RNA identification and quantification. The most common extraction methods employ silica columns or the TRIzol reagent but give out low recovery for small RNAs probably due to their short strand lengths. Herein, we fabricated the titanium dioxide nanofibers using electrospinning to facilitate miRNA extraction and developed the optimal buffer conditions to improve miRNA recovery from biological matrices of cell lysate and serum. We found that our TiO₂ fibers could obtain a recovery of 18.0 ± 3.6% for miRNA fibers while carrying out the extraction in the more complex medium of cell lysate, much higher than the 0.02 ± 0.0001% recovery from the commercial kit. The much improved extraction of miRNAs from our fibers could be originated from the strong coordination between TiO₂ and RNA's phosphate backbone. In addition, the binding, washing, and elution buffers judiciously developed in the present study can achieve selective extraction of small RNA shorter than 500 nucleotides in length. Our results demonstrate that TiO₂ nanofibers can work as a valuable tool for extraction of miRNAs from biological samples with high recovery. Graphical abstract Schematic for extraction of small RNAs using TiO₂ nanofibers.