Inhibition of mTORC1/2 by INK-128 Impairs in vitro Oocyte Maturation in Mice
ABSTRACT
Objective:
Oocyte maturation is a complex process that encompasses both nuclear and cytoplasmic events, tightly regulated by multiple signaling pathways. The mammalian target of rapamycin (mTOR) has been implicated in follicular development and oocyte maturation, primarily through the activity of its two complexes, mTORC1 and mTORC2. While first-generation inhibitors such as rapamycin have been extensively studied, the simultaneous inhibition of both mTORC1 and mTORC2 by second-generation inhibitors remains poorly characterized in oocytes. In this study, we investigated the effect of INK-128, a dual mTORC1/2 inhibitor, on in vitro maturation (IVM) of mouse oocytes.
Materials and Methods:
Germinal vesicle (GV) stage oocytes were isolated from 6-week-old Balb/c female mice following 5 IU pregnant mare serum gonadotropin (PMSG) stimulation. The oocytes were cultured in vitro for 18 hours in the presence of 10 nM, 50 nM, or 100 nM INK-128, while untreated oocytes served as controls. Maturation outcomes were assessed by morphological evaluation, total oocyte scoring (TOS), and immunofluorescence staining of α-tubulin and mTOR expression.
Results:
Our results showed that INK-128 treatment reduced the overall maturation rate from GV to metaphase II (MII) stage. In particular, MII oocytes exhibited significantly decreased mTOR expression at 50 nM (p=0.0162) and 100 nM (p<0.0001) concentrations compared to controls. Furthermore, higher doses of INK-128 were associated with abnormal spindle organization and increased cytoplasmic granularity.
Conclusion:
These findings suggest that dual inhibition of mTORC1/2 by INK-128 impairs oocyte maturation and highlights a potential role for mTOR in the MI-to-MII transition. Further investigations are required to elucidate the underlying mechanisms and to explore the translational relevance of mTOR modulation in assisted reproductive technologies.
Keywords:
Oocyte maturation,
mTORC1,
mTORC2,
INK-128,
in vitro maturation,
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