Cell-free mitochondrial DNA increases granulosa cell apoptosis and reduces aged oocyte blastocyst development in the...

Area of Science:

• Reproductive biology
• Cellular and molecular biology
• Immunology

Background:

• Extracellular cell-free mitochondrial DNA (cf-mtDNA) can trigger inflammatory responses and cellular damage.
• The impact of cf-mtDNA on ovarian granulosa cell function and oocyte developmental competence remains incompletely understood.

Purpose of the Study:

• To investigate the effects of cf-mtDNA on mouse ovarian granulosa cell function.
• To assess the influence of cf-mtDNA on the developmental competence of in vitro matured oocytes, particularly in aged mice.

Main Methods:

• Treatment of mouse ovarian granulosa cells and oocytes with cf-mtDNA.
• Assessment of granulosa cell ATP content, apoptosis, and apoptosis-related gene/protein expression.
• Measurement of Toll-like receptor 9 (TLR9), NF-κB p65, and MAPK p38 signaling pathway activation.
• Evaluation of oocyte developmental competence, including blastocyst formation rates after in vitro maturation.

Main Results:

• cf-mtDNA treatment led to decreased ATP content and increased apoptosis in granulosa cells.
• mRNA and protein levels of apoptosis-related factors were elevated in cf-mtDNA treated granulosa cells.
• Expression of TLR9, NF-κB p65, and MAPK p38 was significantly increased in granulosa cells exposed to cf-mtDNA.
• Blastocyst formation rates were significantly reduced in oocytes from aged mice matured in cf-mtDNA-containing media, while oocytes from young mice were unaffected.

Conclusions:

• cf-mtDNA impairs granulosa cell function and induces apoptosis, negatively impacting oocyte developmental competence in aged mice.
• The detrimental effects of cf-mtDNA on granulosa cells and oocytes may involve TLR9 binding and activation of NF-κB p65 and MAPK p38 signaling pathways.