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Published on: July 30, 2020
Rapamycin rescues the poor developmental capacity of aged porcine oocytes
Seung Eun Lee1, Eun Young Kim2, Hyun Yong Choi1
1Stem Cell Research Center, Jeju National University, Jeju 690-756, Korea.
Abstract:
Unfertilized oocytes age inevitably after ovulation, which limits their fertilizable life span and embryonic development. Rapamycin affects mammalian target of rapamycin (mTOR) expression and cytoskeleton reorganization during oocyte meiotic maturation. The goal of this study was to examine the effects of rapamycin treatment on aged porcine oocytes and their in vitro development. Rapamycin treatment of aged oocytes for 24 h (68 h in vitro maturation [IVM]; 44 h+10 μM rapamycin/24 h, 47.52±5.68) or control oocytes (44 h IVM; 42.14±4.40) significantly increased the development rate and total cell number compared with untreated aged oocytes (68 h IVM, 22.04±5.68) (p<0.05). Rapamycin treatment of aged IVM oocytes for 24 h also rescued aberrant spindle organization and chromosomal misalignment, blocked the decrease in the level of phosphorylated-p44/42 mitogen-activated protein kinase (MAPK), and increased the mRNA expression of cytoplasmic maturation factor genes (MOS, BMP15, GDF9, and CCNB1) compared with untreated, 24 h-aged IVM oocytes (p<0.05). Furthermore, rapamycin treatment of aged oocytes decreased reactive oxygen species (ROS) activity and DNA fragmentation (p<0.05), and downregulated the mRNA expression of mTOR compared with control or untreated aged oocytes. By contrast, rapamycin treatment of aged oocytes increased mitochondrial localization (p<0.05) and upregulated the mRNA expression of autophagy (BECN1, ATG7, MAP1LC3B, ATG12, GABARAP, and GABARAPL1), anti-apoptosis (BCL2L1 and BIRC5; p<0.05), and development (NANOG and SOX2; p<0.05) genes, but it did not affect the mRNA expression of pro-apoptosis genes (FAS and CASP3) compared with the control. This study demonstrates that rapamycin treatment can rescue the poor developmental capacity of aged porcine oocytes.
Insights
Rapamycin treatment improves aged porcine oocytes by enhancing development and rescuing cellular defects. This study shows rapamycin can overcome age-related oocyte quality decline, improving fertility potential.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cellular Aging
Background:
- Unfertilized oocytes have a limited lifespan post-ovulation, impacting fertility and embryonic development.
- Oocyte aging leads to reduced developmental potential and cellular abnormalities.
- Mammalian target of rapamycin (mTOR) and cytoskeleton are crucial for oocyte maturation.
Purpose of the Study:
- To investigate the effects of rapamycin on aged porcine oocytes and their in vitro developmental capacity.
- To assess rapamycin's impact on cellular integrity, gene expression, and developmental potential in aged oocytes.
Main Methods:
- Aged porcine oocytes were treated with rapamycin (10 μM) for 24 hours during in vitro maturation (IVM).
- Development rates, cell numbers, spindle organization, chromosome alignment, and gene expression (cytoplasmic maturation factors, mTOR, autophagy, apoptosis, development genes) were analyzed.
- Reactive oxygen species (ROS) activity, DNA fragmentation, and mitochondrial localization were also assessed.
Main Results:
- Rapamycin treatment significantly increased the oocyte development rate and total cell number compared to untreated aged oocytes.
- It rescued aberrant spindle organization and chromosomal misalignment, maintained phosphorylated-p44/42 mitogen-activated protein kinase (MAPK) levels, and increased cytoplasmic maturation factor gene expression.
- Rapamycin decreased ROS activity and DNA fragmentation, downregulated mTOR expression, increased mitochondrial localization, and upregulated autophagy, anti-apoptosis, and development gene expression.
Conclusions:
- Rapamycin treatment can effectively rescue the poor developmental capacity of aged porcine oocytes.
- It ameliorates age-related cellular defects, including spindle/chromosome abnormalities and oxidative stress.
- Rapamycin enhances oocyte quality by modulating key cellular pathways, offering potential for improving reproductive outcomes in aged females.
