Morphological features of the internal organs in mice after prolonged microplastics consumption

Introduction.Microplastics (MP) pollute the environment and can pose a danger to living organisms including humans. Experimental studies on mice and rats demonstrated that microplastics can enter the internal environment, causing structural damage to and dysfunction of various organs. However, data on this issue are scarce and contradictory. The aim of this paper was to characterize morphological changes in the internal organs in mice after prolonged MP consumption in different doses. Materials and methods. We formed four groups (n=5 each): three experimental and one control group. Mice of the experimental groups were given a 5-μm polystyrene particle suspension in distilled water at a concentration of 0.1, 1, and 10 mg/l for 4 weeks. The daily consumption doses averaged 0.023, 0.23, and 2.3 mg of microparticles per kg of animal body weight, respectively. The control group received distilled water throughout the experiment. We conducted a morphological examination of the colon, spleen, liver, kidneys, lungs, thymus, mesenteric lymph nodes, brain, heart, testicles, and thigh muscles. In the colon, morphometric methods were used to evaluate inflammatory infiltration, the number of endocrine and goblet cells, and the content of neutral and highly sulfated mucins in the latter. Results. On morphological examination under the influence of 5-μm polystyrene particle consumption in different doses, we revealed pathological changes only in the spleen and colon. However, a decrease in the goblet cell volume fraction in the colon mucosa was found in the group with low dose of microplastics (0.023 mg/kg/day). The group that consumed 2.3 mg/kg/day of microplastics showed the activation of both spleen compartments, an increased endocrine cells count, and a decreased proportion of highly sulfated mucins in goblet cells. Conclusion. Polystyrene microparticles with a 5-μm diameter consumed for 4 weeks at doses of 0.023–2.3 mg/kg/day cause adaptive morphological and functional changes in the colon and spleen. Keywords: microplastics, polystyrene, spleen, colon, internal organs