FSP1 regulates ferroptosis and mitochondrial function during mouse oocyte maturation

Oocyte quality plays a fundamental role in fertilization and embryonic development. Emerging evidence indicates that ferroptosis may impair oocyte quality. Ferroptosis suppressor protein 1 (FSP1), a known ferroptosis inhibitor, has an uncharacterized function in regulating oocyte quality during meiotic maturation. This study identified FSP1 expression across all stages of meiotic maturation with localization to the cytoplasm of mouse oocytes. Aged mice exhibited a marked reduction in FSP1 expression within the ovaries and oocytes. Pharmacological inhibition of FSP1 disrupted germinal vesicle breakdown and polar body emission, leading to spindle defects and chromosome misalignment. Additionally, FSP1 inhibition persistently activated the spindle assembly checkpoint, resulting in meiotic arrest. At the mechanistic level, inhibition of FSP1 led to an increase in intracellular Fe²⁺ levels, enhanced dihydroethidium fluorescence, excessive accumulation of reactive oxygen species, and intensified lipid peroxidation. Disruptions in ferroptosis-associated gene expression further indicated that oocytes underwent ferroptosis. Moreover, mitochondrial dysfunction was evident following FSP1 inhibition, as reflected by aberrant mitochondrial distribution, diminished ATP production, and an elevated mitochondrial membrane potential. Collectively, these results establish FSP1 as a key regulator of oocyte meiotic maturation by modulating iron homeostasis and mitochondrial function, while its inhibition triggers ferroptosis-dependent meiotic failure.