Endoplasmic Reticulum-Derived Multilamellar Bodies in Oocytes of Mouse Follicle Cultures under Oxidized Low-Density Lipoprotein Treatment

Abstract

Objective: Multilamellar bodies associated with an organized endoplasmic reticulum (ER) arise in various somatic cell types, and a subtype called multivesicular bodies is described in oocytes. Both entities, so far undetermined in significance, may occur in oocytes of follicles under oxidative stress. In preovulatory follicles, oxidative stress appears to be caused by oxidized low-density lipoprotein (ox-LDL). Method: Cultures of preantral mouse follicles were treated with 100 µg/ml ox-LDL or normal LDL (n-LDL) for 12–48 h or for 12 days during antral follicle growth followed by in vitro ovulation and harvest of cumulus oophorus complexes (COCs) with metaphase II (MII) oocytes on day 13. Preantral follicles, COCs, or MII oocytes were immunostained with anti-tubulin antibody or stained with actin-binding phalloidin for confocal microscopy. Ultrathin sections were prepared for electron microscopy. Results: Preantral follicles exposed to n-LDL or ox-LDL developed normally, and MII oocytes in COCs possessed normal spindles with well-aligned chromosomes. In contrast, treated cumulus cells underwent apoptosis. Only the ox-LDL-treated preantral follicle oocytes showed ER-derived multilamellar bodies (EMBs) of type I, consisting of rough ER membranes for the envelope. The MII oocytes of COCs showed type II EMBs consisting of smooth/vesicular ER and were more prominent after ox-LDL than after n-LDL exposure. Degenerating mitochondria were prominent in oocytes of the ox-LDL group and judged as a sign of oxidative stress. Conclusion: Oxidative stress presumably induces damage of proteins and organelles in the oocytes. The EMBs might sequester the damaged structures for oocyte survival. Thus, EMBs could represent a novel form of autophagy.

OX-LDL promotes insufficient autophagy and apoptosis of ovarian granulosa cells through regulation ROS-mediated PI3K/Akt/mTOR pathway

“…According to references [11,12], Katharina et al, (2013) [11] and Ying Liu et al, (2019) [12], POI mouse model was established by injecting OX-LDL (150 mg/kg), (n = 20). The establishment of the model was carried out by the Animal Laboratory of Sun Yat sen University.…”

“…According to references [11,12], mice ovarian granulosa cells were obtained from BALB/c mice (n = 6) of the Animal Laboratory of Sun Yat sen University (Guangzhou, China). The female BALB/c mice ovaries were quickly dissected under sterile conditions and put into pre-cooled PBS to remove the surrounding tissues and surface capsule.…”