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dcyphr | Polystyrene microplastics induced male reproductive toxicity in mice
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Contributors
Daniel Amuedo

I am a premedical student at Missouri St...

Abstract 

Microplastics (MP) have become a global threat recently. Their toxicity is largely unknown. This study looks at the toxic effects of 0.5 μm, 4 μm, and 10 μm polystyrene microplastic (PS-MPs) on the male reproductive system of adult mice. 4 and 10 μm MP accumulated in the testis of the mice, while all three sizes were able to enter into three different kinds of testicular cells. The testosterone levels and sperm quality both declined after exposure for 28 days. Cellular abnormalities were also reported. Generally the PS-MPs caused inflammation of the testicular tissue and breaking in the blood-testis barrier. Therefore, this study demonstrates reproductive issues as a result of PS-MPs exposure. 


Introduction 

MP are any plastic smaller than 5mm in diameter. The most common types are polyethylene, polypropylene, and polystyrene in the marine environment. They can accumulate and travel up the food chain. Previous studies show MPs can accumulate in the gastrointestinal tract, liver, kidney, and brain of both marine and mammalian organisms. Other studies have shown that they can cause disturbance of energy and lipid metabolism, cause neurotoxicity, trigger inflammation in the intestine of mice, reduce growth rate, reduce fertility, decrease the lifespan, increase reproduction time, reduce feeding activity and body health, cause oxidative damage, and  intestinal damage. 


Materials and Methods 

    0.5, 4, and 10 μm polystyrene microplastics were used. Gastric tissue was used as a positive control in this experiment. 


Results 

    The 4 and 10 μm PS-MPs caused a decrease in food consumption whereas the 0.5 μm did not cause a significant change. The PS-MPs caused the loss of spermatogenic cells, disordered arrangements of spermatogenic cells, and malformed multinucleated gonocytes within the seminiferous tubules. The sperm produced had decreased mobility and increased abnormalities. Similarly, the testis were inflamed. The Blood-testicle barrier (BTB) meant to protect sperm from harmful chemicals was also noted to have been disrupted. Finally, there was a decrease in testosterone levels compared to the control for all three groups. 


Discussion 

    The production of sperm is dependent upon many things: the blood-testis barrier to provide a safe environment, the nutrition from Sertoli cells, and the testosterone for signaling. All three of these were affected by the presence of MPs leading to decreased mobility and increased abnormalities. The data in this study suggests that there is no link between size of the MP and the amount of toxicity experienced by the organism. This study shows that PS-MPs can enter Sertoli {help to sustain the sperm}, Leydig {produce testosterone}, and Germ cells. 


Conclusion 

    This study shows that Polystyrene microplastics (PS-MPs) can induce reproductive toxicity in male mice. This leads to disorders of the spermatogenic cells {cells that produce sperm], decreased testosterone, testicular inflammation, and destruction of the blood-testis barrier. Future studies should investigate the mechanism of how this occurs.