Silica nanoparticles suppress porcine oocyte maturation via oxidative stress, metabolic dysfunction, and impaired cholesterol trafficking.

Silica nanoparticles (SiNPs), as common feed additives, are widely applied in livestock diets and pose potential risks to reproductive health owing to their tissue accumulation. In the present study, we explored the effects and underlying mechanisms of SiNPs exposure during in vitro maturation (IVM) of porcine oocytes. The results showed that SiNPs significantly suppress porcine oocyte maturation as evidenced by decreased first polar body (PB1) release rate. Notably, SiNPs significantly induced abnormal expansion of cumulus cells and impaired gap junction intercellular communication (GJIC), accompanied by decreased Connexin 43 (CX43) expression and aberrant F-actin structure. Furthermore, DCFH-DA staining showed that SiNPs significantly increased reactive oxygen species (ROS) levels and malondialdehyde (MDA) content, and decreased the mRNA levels of antioxidant-related genes, including SOD1, SOD2, CAT, GPX1, PRDX2, and NRF2. JC-1 staining showed that SiNPs significantly induced mitochondrial dysfunction via diminished mitochondrial membrane potential (ΔΨm) and aberrant distribution, and decreased the mRNA levels of energy metabolism-related genes, such as NOX4 and COX2. Additionally, SiNPs significantly disrupted lysosomal function and cholesterol trafficking and decreased the mRNA levels of LDLR, NPC1, NPC2, and LAMP2, leading to reduced free cholesterol levels and the mRNA levels of estrogen synthesis-related genes, including STAR, CYP19A1, and HSD-3β. Collectively, SiNPs suppress porcine oocyte maturation, at least partly, through oxidative stress, metabolic disruption, and impaired cholesterol trafficking.