Study question
Can higher concentrations of di-2-ethylhexyl phthalate (DEHP) in follicular fluid (FF) lead to an altered microRNA expression profile?
Summary answer
The present study indicates the upregulation of miR-203a-3p, miR-150-5p and miR-28-3p in the follicular fluid of women with higher DEHP concentrations (FDR<0.05).
What is known already
Women are exposed daily to endocrine-disrupting chemicals (EDCs) such as phthalates which can be found in hundreds of personal care products and plastic items. In studies of rodents exposed to certain phthalates, high doses have been shown to change hormone levels, disrupt folliculogenesis and cause birth defects. Recently, we reported a strong inverse association between DEHP metabolites and ovarian sensitivity index (OSI) in females undergoing ART treatment. Several mechanisms have been proposed to explain the association between DEHP and fertility in rodents, however not much is known about the mechanisms in humans.
Study design, size, duration
FF was collected from 96 women undergoing IVF treatment after controlled ovarian stimulation during ovarian puncture. 48 participants from Estonia were recruited at Nova Vita Clinic AS in Tallinn, Estonia in 2019 and 48 participants from Sweden were recruited at Carl von Linnekliniken in Uppsala, Sweden in 2016. In both cohorts, patients signed a written informed consent form. Both cohorts were matched for age, BMI, parity and the number of previous IVF treatments.
Participants/materials, setting, methods
DEHP metabolite concentrations in the FF samples were measured in our earlier study by LC-MS/MS. Cell free RNA was extracted from FF samples with Qiagen miRNeasy Micro kit, sequencing libraries were prepared with QIAseq miRNA library kit and sequenced on Illumina NextSeq 550 instrument. Differential miRNA expression analysis was performed with the DESeq2 package. Pathway enrichment analysis for differentially expressed miRNA targets was conducted with the miEAA tool integrated with WikiPathways.
Main results and the role of chance
In total, 465 miRNAs were observed at least twice in ≥ 24 samples. Differential expression analysis was conducted between DEHP-high and DEHP-low groups in combined cohorts using the cohort as a covariate. 16 miRNAs were found to be differentially expressed between DEHP groups with FDR<0.1. Three miRNAs: miR-203a-3p, miR-150-5p and miR-28-3p, were differentially expressed with FDR<0.05 and were more abundant in women with high DEHP-levels in both cohorts. Of these, miR-203a-3p was negatively correlated with OSI (Pearson R = -0.27, p = 0.0089). Six miRNAs (miR-10b-5p, miR-112-5p, miR-132-5p, miR-203-3p, miR-205-5p and miR-27-3p) were found to have predicted targets in the androgen receptor signalling pathway.
Limitations, reasons for caution
The miRNAs found in this study need to be validated in a larger set of patients as a cohort-dependent difference in the results was observed. There is a need for further functional studies to investigate miRNAs as possible mediators of the association between DEHP and ovarian sensitivity index.
Wider implications of the findings
The current study presents evidence that DEHP exposure alters the expression of FF miRNAs which are associated with androgen receptor signalling. These results provide novel evidence of the potential influence of endocrine-disrupting chemicals on female reproduction.
Trial registration number
NA
