The effect of titanium dioxide nanoparticles injection in neonatal period on ovaries in mature rats

Titanium dioxide nanoparticles are one of the most widely used materials in various industrial and biological fields. In this study, due to the importance of reproduction in organisms, the toxicity of titanium oxide nanoparticles was investigated on ovaries. In this experimental study, concentrations of 50, 100 and 150 mg/kg titanium dioxide nanoparticles (TiO₂ NPs) with10-20 nm diameter  were injected (IP) into immature female (age 35-40 days) for 5 consecutive days. Blood collection was performed three months after the last injection (at puberty) and the levels of hormones (LH, FSH, estrogen and progestron) in the serum were measured by ELISA. After anesthesia and dissection of animals, tissue sections of ovary were prepared and stained with hematoxylin-eosin. Then, the morphological status of ovarian tissue was investigated by optical microscopy. Data were analyzed using ANOVA. Results showed that weight of body and levels of LH and FSH in treated groups did not change significantly. Whereas, the amounts of estrogen and progesterone hormones increased significantly in the concentration of 150 mg/kg of TiO2 NPs. The TiO2 NPs caused histopathologic changes in the ovary including loss of Graafian follicles, destruction of follicles wall, reducing the thickness of Granulosa and Thec layers. Also, there was a significant decrease in the number of Corpus luteum, growing and Graafian follicles at concentrations of 100 and 150 mg/kg. It appears that injection of concentrations higher than 50mg/kg of TiO2 NPs in the pre-pubertal period leads to impaired ovarian activity and structure after puberty, however further studies are needed to solidify fertility reduction in these treatments.