Tiny Plastics in Ruminant Reproduction: Friends, Foes, or simply passing through?

Through forage ingestion, ruminants are primarily exposed to plastic contamination, largely due to its use in agricultural practices and withdrawal materials. Plastics are not only widespread environmental pollutants but also carriers for endocrine disruptors, posing serious threats to reproductive health. Although plastic fragments have been detected in human placenta(1), bovine follicular fluid(2) and semen(3), the health effects of these emerging contaminants remain unclear. We believe that throughout the bloodstream, plastics infiltrate highly vascularized reproductive organs, so we tested the effect of PETs in in vitro cellular systems of sheep placenta (oTP) and bovine mammary gland (MACT) cells. Virgin PETs (100–400 μm) were mechanically ground to mimic environmental degradation. Morphology, size distribution, and structural changes were analysed via Particle Flow Image Analysis and X-ray diffraction. Cells were exposed to <30 and 20–50 μm PETs (1, 5, 50 μg/mL) for 24 and 48 hours. PET-cell interactions were assessed by cell viability (MTT assay) and migration assay. MACTs exhibited greater resilience to PET exposure than oTPs, whose viability decreased at higher concentrations of 20–50 μm PETs, and cytotoxicity was observed from 1 μg/mL for <30 μm PETs. Although migration remained unaltered, cell–PET physical interactions were recorded at 50 μg/mL. Preliminary data suggest that PET effects are cell–type–dependent, with more sensitive cells showing size-specific responses, possibly due to steric hindrance. Prolonged exposure (>48 hours) may further impair cell viability. Moreover, studies employing environmentally aged particles, rather than virgins, are needed to assess their impact on key cellular functions. 1 Ragusa et al. Plasticenta: First evidence of microplastics in human placenta. Environment International, 146: 106274, 2021. 2 Greghi et al. Microplastics are present in women’s and cows’ follicular fluid and polystyrene microplastics compromise bovine oocyte function in vitro. eLife 12, RP86791. 2023. 3 Greghi et al. Microplastics are detected in bull epididymal sperm and polystyrene microparticles impair sperm fertilization. Biology of Reproduction, 111: 1341–1351, 2024.