Wen Huang

Despite advances in in vitro fertilization (IVF), there is still a lack of non-invasive and reliable biomarkers for selecting embryos with the highest developmental and implantation potential. Recently, small non-coding RNAs (sncRNAs) have been identified in biological fluids, and extracellular sncRNAs are explored as diagnostic biomarkers in the prediction of IVF outcomes. To determine the predictive role of sncRNAs in embryo quality and IVF outcomes, a systematic review and meta-analysis was performed. Articles were retrieved from PubMed, EMBASE, and Web of Science from 1990 to 31 July 2022. Eighteen studies that met the selection criteria were analyzed. In total, 22 and 47 different sncRNAs were found to be dysregulated in follicular fluid (FF) and embryo spent culture medium (SCM), respectively. MiR-663b, miR-454 and miR-320a in FF and miR-20a in SCM showed consistent dysregulation in two different studies. The meta-analysis indicated the potential predictive performance of sncRNAs as non-invasive biomarkers, with a pooled area under curve (AUC) value of 0.81 (95% CI 0.78, 0.844), a sensitivity of 0.79 (95% CI 0.72, 0.85), a specificity of 0.67 (95% CI 0.52, 0.79) and a diagnostic odds ratio (DOR) of 8 (95% CI 5, 12). Significant heterogeneity was identified among studies in sensitivity (I2 = 46.11%) and specificity (I2 = 89.73%). This study demonstrates that sncRNAs may distinguish embryos with higher developmental and implantation potentials. They can be promising non-invasive biomarkers for embryo selection in ART. However, the significant heterogeneity among studies highlights the demand for prospective multicenter studies with optimized methods and adequate sample sizes in the future.

The prevalence of type 2 diabetes (T2D) is rapidly increasing across the globe. Fetal exposure to maternal diabetes was correlated with higher prevalence of impaired glucose tolerance and T2D later in life. Previous studies showed aberrant DNA methylation patterns in pancreas of T2D patients. However, the underlying mechanisms remained largely unknown. We utilized human embryonic stem cells (hESC) as the in vitro model for studying the effects of hyperglycemia on DNA methylome and early pancreatic differentiation. Culture in hyperglycemic conditions disturbed the pancreatic lineage potential of hESC, leading to the downregulation of expression of pancreatic markers PDX1, NKX6−1 and NKX6−2 after in vitro differentiation. Genome-wide DNA methylome profiling revealed over 2000 differentially methylated CpG sites in hESC cultured in hyperglycemic condition when compared with those in control glucose condition. Gene ontology analysis also revealed that the hypermethylated genes were enriched in cell fate commitment. Among them, NKX6−2 was validated and its hypermethylation status was maintained upon differentiation into pancreatic progenitor cells. We also established mouse ESC lines at both physiological glucose level (PG-mESC) and conventional hyperglycemia glucose level (HG-mESC). Concordantly, DNA methylome analysis revealed the enrichment of hypermethylated genes related to cell differentiation in HG-mESC, including Nkx6−1. Our results suggested that hyperglycemia dysregulated the epigenome at early fetal development, possibly leading to impaired pancreatic development.