Mitochondrial metabolic checkpoints, regulated by reactive oxygen species, gatekeep human gamete competence and fertility

Infertility affects millions globally, often linked to compromised gamete quality. Mitochondria are central to gamete metabolism and signaling, synchronizing energy generation with redox equilibrium. Historically, reactive oxygen species (ROS) were viewed solely as harmful byproducts of metabolism. However, emerging research suggests ROS are critical signaling molecules, creating a 'redox window of competence' essential for successful oocyte maturation, sperm capacitation, and early embryo development. A deeper understanding of these mitochondrial metabolic checkpoints and the precise role of ROS is crucial for improving assisted reproductive technologies (ARTs).

This comprehensive review synthesizes current understanding of mitochondrial metabolic checkpoints in human fertility, drawing from extensive in vitro and in vivo studies. The authors propose a framework where reactive oxygen species (ROS) act as crucial signaling molecules, rather than mere byproducts, regulating gamete competence. The review explores the dynamic interplay between mitochondrial activity, redox balance, and cellular signaling across key stages of reproduction, including oogenesis, spermatogenesis, fertilization, and early embryogenesis. It also examines how assisted reproductive technologies (ARTs) may inadvertently disrupt this delicate redox equilibrium and discusses potential therapeutic strategies.

The review highlights that ROS establish a critical 'redox window of competence' essential for proper oocyte maturation, sperm capacitation, and early embryo development. > Oocytes demonstrate a unique ability to maintain a nearly ROS-free metabolic state by strategically blocking specific respiratory-chain components, underscoring the profound importance of mitochondrial remodeling for gamete quality. Evidence indicates that ROS serve as dynamic gatekeepers at multiple critical junctures throughout the reproductive process, including oogenesis, spermatogenesis, fertilization, and early embryogenesis. Furthermore, the synthesis reveals that current ART practices can inadvertently disrupt this vital redox-metabolic balance, potentially compromising outcomes. The authors identify several promising translational strategies to optimize mitochondrial function, including precise modulation of oxygen tension, the use of mitochondria-directed antioxidants such as MitoQ and SS-31, and supplementation with key nutraceuticals like melatonin, CoQ10, and resveratrol.