Exosomes Derived from Yak Follicular Fluid Increase 2-Hydroxyestradiol Secretion by Activating Autophagy in Cumulus Cells

SIMPLE SUMMARY: Exosomes in the follicular fluid can carry and transfer regulatory molecules to recipient cells, thus influencing their biological functions. In this study, after being treated with yak follicular fluid for 24 h, most yak cumulus cells took up the exosomes, activated autophagy, and increased their secretion of 2-hydroxyestrodiol. Conversely, the inhibition of autophagy with the chemical reagent 3-methyladenine blocked these effects, suggesting that autophagy has an important role in 2-hydroxyestrodiol secretion in the yak cumulus cells. The results of rapamycin treatment of the yak cumulus cells showed a similar effect on yak follicular fluid exosomes as there was an increase in 2-hydroxyestrodiol secretion due to the activation of autophagy. The results suggest that autophagy is activated by yak follicular fluid exosomes and this increases 2-hydroxyestrodiol secretion in the yak cumulus cells. ABSTRACT: Exosomes in the follicular fluid can carry and transfer regulatory molecules to recipient cells, thus influencing their biological functions. However, the specific effects of yak follicular fluid exosomes on 2-hydroxyestrodiol (2-OHE(2)) secretion remain unknown. Here, we investigated whether yak follicular fluid exosomes can increase 2-OHE(2) secretion through the activation of autophagy in cumulus cells (YCCs). In vitro cultured YCCs were treated with yak follicular fluid exosomes for 6, 12, and 24 h. The effects of yak follicular fluid exosomes on autophagy and 2-OHE(2) secretion were evaluated through real-time quantitative fluorescence PCR (RT-qPCR), Western blotting (WB), transfected with RFP-GFP-LC3, immunohistochemistry, and ELISA. To further investigate whether 2-OHE(2) secretion was related to autophagy, YCCs were administered with yak follicular fluid exosomes, 3-methyladenine (3-MA), and rapamycin (RAPA). The results revealed that treatment with yak follicular fluid exosomes activated autophagy in YCCs and increased 2-OHE(2) secretion. Conversely, the inhibition of autophagy with 3-MA blocked these effects, suggesting that autophagy has an important role in 2-OHE(2) secretion in YCCs. Treatment of YCCs with rapamycin showed similar results with yak follicular fluid exosomes as there was an increase in 2-OHE2 secretion due to the activation of autophagy in the treated cumulus cells. Our results demonstrate that autophagy is enhanced by yak follicular fluid exosomes, and this is associated with an increase in 2-OHE(2) secretion in YCCs.