TiC nanosheet-induced autophagy derails ovarian functions.

Background: Two-dimensional ultrathin TiC (MXene) nanosheets have gained significant attention in various biomedical applications. Although previous studies have described the accumulation and associated damage of TiC nanosheets in the testes and placenta. However, it is currently unclear whether TiC nanosheets can be translocated to the ovaries and cause ovarian damage, thereby impairing ovarian functions.

Results: We established a mouse model with different doses (1.25, 2.5, and 5 mg/kg bw/d) of TiC nanosheets injected intravenously for three days. We demonstrated that TiC nanosheets can enter the ovaries and were internalized by granulosa cells, leading to a decrease in the number of primary, secondary and antral follicles. Furthermore, the decrease in follicles is closely associated with higher levels of FSH and LH, as well as increased level of E and P, and decreased level of T in mouse ovary. In further studies, we found that exposure toTiC nanosheets increased the levels of Beclin1, ATG5, and the ratio of LC3II/Ι, leading to autophagy activation. Additionally, the level of P62 increased, resulting in autophagic flux blockade. TiC nanosheets can activate autophagy through the PI3K/AKT/mTOR signaling pathway, with oxidative stress playing an important role in this process. Therefore, we chose the ovarian granulosa cell line (KGN cells) for in vitro validation of the impact of autophagy on the hormone secretion capability. The inhibition of autophagy initiation by 3-Methyladenine (3-MA) promoted smooth autophagic flow, thereby partially reduced the secretion of estradiol and progesterone by KGN cells; Whereas blocking autophagic flux by Rapamycin (RAPA) further exacerbated the secretion of estradiol and progesterone in cells.

Conclusion: TiC nanosheet-induced increased secretion of hormones in the ovary is mediated through the activation of autophagy and impairment of autophagic flux, which disrupts normal follicular development. These results imply that autophagy dysfunction may be one of the underlying mechanisms of TiC-induced damage to ovarian granulosa cells. Our findings further reveal the mechanism of female reproductive toxicity induced by TiC nanosheets.