Polystyrene and polyethylene terephthalate nanoplastics differentially impact mouse ovarian follicle function

Abstract

Exposure to micro- and nanoplastics is unavoidable. Foods and beverages contain plastic particles from environmental contamination and processing and packaging materials, which are frequently made of polyethylene terephthalate (PET). Micro- and nanoplastics have been detected in human tissues such as the brain, liver, and placenta, as well as in ovarian follicular fluid, but little is known about the effects nanoplastics have on the female reproductive system. In addition, few studies on the health impacts of nanoplastics have been performed using environmentally relevant plastic types and concentrations. Thus, this research tested the hypothesis that nanoplastics made of spherical polystyrene (PS), a common model nanoplastic, would have different effects on cultured mouse ovarian follicles compared to secondary PET nanoplastics at environmentally relevant doses. The ovary is a highly sensitive reproductive organ responsible for the development of follicles, which contain the oocyte, and production of steroid hormones. Follicles were harvested from adult mouse ovaries and cultured for 96 h with vehicle, spherical commercially available 200 nm PS nanoplastics (1-100 μg/mL), or lab-generated 240 nm PET nanoplastics (0.1-10 μg/mL). PS and PET nanoplastic exposure inhibited follicle growth and altered expression of genes related to steroid synthesis, cell cycle, and oxidative stress. PET nanoplastics increased levels of pregnenolone and decreased expression of Cyp17a1. Overall, both plastic types altered ovarian function, but they impacted different genes in similar pathways. These findings suggest that nanoplastic exposure at environmentally relevant concentrations may pose a risk to female reproductive health by disrupting hormonal and molecular pathways. In addition, environmentally relevant plastic types and doses are necessary for studying health impacts of nanoplastics.

Keywords: antral follicle; folliculogenesis; nanoplastics; ovary; steroidogenesis.

Figure 1

Nanoplastics were characterized using scanning electron microscopy (SEM) for purchased PS spheres (A, scale bar 100 nm) and lab ground PET before (B) and after (C) sonicating (scale bar 1μm).

Figure 2

Effect of PS (A) and PET (B) treatment on antral follicle growth. Follicle growth was measured every 24 hrs for 96 hrs. Graphs represent mean ± SEM from 5–6 independent replicates per treatment group. Asterisks (*) indicate significant differences from the control (p ≤ 0.05) and ^ indicates a trend toward significance.

Figure 3

Impact of PS (A) and PET (B) treatment on hormone levels in the media following 96 hrs of culture. Culture media were subjected to enzyme-linked immunosorbent assays. Asterisks (*) indicate significant differences from the control (p ≤ 0.05). Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05) and ^ indicates a trend toward significance.

Figure 4

Impact of PS (A) and PET (B) treatment on steroidogenesis gene expression measured via qPCR. Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05) and ^ indicates a trend toward significance (p ≤ 0.10).

Figure 5

Impact of PS (A) and PET (B) treatment on cell cycle regulator expression measured via qPCR. Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05) and ^ indicates a trend toward significance (p ≤ 0.10).

Figure 6

Impact of PS (A) and PET (B) treatment on apoptosis related gene expression measured via qPCR. Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05) and ^ indicates a trend toward significance (p ≤ 0.10).

Figure 7

Impact of PS (A) and PET (B) treatment on receptor gene expression measured via qPCR. Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05).

Figure 8

Impact of PS (A) and PET (B) treatment on oxidative stress gene expression measured via qPCR. Graphs represent mean ± SEM from 4–6 separate experiments. Asterisks (*) indicate significant differences from the control (p ≤ 0.05).