Hypothesis / aims of study
Due to the problematic degradation properties of plastics, the decomposition of plastic results in the formation of numerous microplastics (MPs), less than 5 mm in diameter. These MPs enter the soil and the ocean, eventually passing through the air, water, or food chain back to the human body and harming human health. Recently, study on the possibility of microplastics invading various organs and causing adverse effects is in progress. In particular, some previous research results have been reported that microplastics can affect spermatogenesis or sperm quality through various pathways. Therefore, this research team studied the relationship between microplastic intake and infertility using 6-week-old C57BL/6 mouse.
Study design, materials and methods
Thirty C57BL/6 male mice were randomly allocated to six equally sized groups. Mice were exposed to Fluorescence polystyrene microparticles (5µm <18%, PS-MPs, Green) at a dose of 0 (control), 1mg/dl, 3mg/dl by oral gavage for 28 and 56 days. At the 28th and 56th day, blood samples were collected for biochemical analysis and testis, the gastrointestinal tract, liver, lung and kidneys were removed from each rat for Fluorescence polystyrene microparticles detection and western blot. Sperm quality, epididymal morphology, expressions of inflammatory markers, and expression in testicular tissues, and expressions of BTB junction proteins were detected.
Results
The results indicated that after exposure for 28days and 56 days, PS-MPs was detected in the testis of mice. The smallest PS-MPs had a size of 5.870 µm, and the largest size was observed up to 7.064 µm. (Figure 1) However, accumulation in the testis of PS-MPs was not observed. There weas significant difference between control group and PS-MPs exposure groups (1mg/dl, 3mg/dl; 1months and 2months) in sperm motility and proportion of normal shape of sperm (p<0.05). (Table 1) However, there was no significant difference between the groups in sperm concentration. In addition, there was no significant difference between three groups in sperm concentration, motility and proportion of normal shape of sperm (p>0.05).
Interpretation of results
These findings suggest that PS-MPs exposure may impact certain aspects of sperm quality in mice, specifically motility and morphology. While no significant difference in sperm concentration was observed, the findings indicate that the exposure to PS-MPs did have an impact on sperm quality. It is also worth noting that the detection of PS-MPs in the testis indicates that these particles can cross the blood-testis barrier, potentially having an impact on the development of sperm cells.
The results of this study contribute to a growing body of research on the impact of microplastics on living organisms, including potential impacts on reproductive health. Further research in this area is needed to better understand the mechanisms by which exposure to microplastics may impact sperm quality, and to determine the potential long-term impacts on reproductive health in both humans and animals.