Ovarian Stimulation and Oocyte Quality Dynamics

Ovarian stimulation is a cornerstone of assisted reproductive technologies, designed to recruit multiple follicles in a single cycle and thereby increase the yield of oocytes available for fertilisation. While exogenous gonadotrophins such as follicle‐stimulating hormone and luteinising hormone effectively amplify follicular development, they also impose a supraphysiological hormonal milieu that can affect oocyte competence. Quality dynamics of the oocyte encompass mitochondrial integrity, chromatin organisation, epigenetic marks and oxidative balance, all of which contribute to fertilisation potential and early embryonic development. Recent work has highlighted that repeated stimulation cycles may perturb the antioxidant machinery, alter mitochondrial DNA content and shift the balance between pro-survival and apoptotic pathways. Equally, changes in histone modifications and DNA methylation patterns in cumulus–oocyte complexes have been observed under intensive stimulation regimens. A nuanced understanding of these processes is essential to refine protocols, minimise long-term impacts on ovarian reserve and optimise outcomes for patients worldwide. Individualising stimulation dose and cycle timing, alongside antioxidative or adjunct therapies, emerges as a promising strategy to preserve oocyte quality while satisfying the growing demand for fertility treatments.

Research from Nature Portfolio

Studies in murine models have demonstrated that repeated superovulation leads to a progressive decline in mitochondrial DNA copy number within cumulus cells, accompanied by altered methylation and expression of nuclear-encoded polymerase genes. These mitochondrial perturbations coincide with shifts in respiratory chain transcript levels, indicating compromised energy metabolism after multiple stimulation rounds. In clinical settings, investigation of a traditional formulation targeting oxidative stress revealed enhancement of antioxidant enzyme activity in granulosa cells and follicular fluid, increased ATP content and mitochondrial DNA abundance, and up-regulation of key transcription factors that govern redox balance. These changes translated into higher rates of high-grade embryos, implantation and clinical pregnancy among patients undergoing repeated controlled ovarian stimulation.

Ovarian Stimulation and Oocyte Quality Dynamics publication trend

The graph below shows the total number of articles in ovarian stimulation and oocyte quality dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Controlled ovarian stimulation (COS): Administration of exogenous hormones to induce the development of multiple ovarian follicles in a single cycle.

Oocyte quality: Intrinsic and extrinsic attributes of an egg that determine its capacity to mature, be fertilised and support early embryogenesis.

Cumulus cells: Somatic cells encasing the oocyte that regulate its microenvironment and contribute signals essential for maturation.

Mitochondrial DNA (mtDNA): Genetic material within mitochondria that encodes components of the respiratory chain and reflects cellular energy status.

Oxidative stress: Condition arising from an imbalance between reactive oxygen species production and antioxidant defence mechanisms, leading to biomolecular damage.

References

1. Repeated Rounds of Gonadotropin Stimulation Induce Imbalance in the Antioxidant Machinery and Activation of Pro-Survival Proteins in Mouse Oviducts. International Journal of Molecular Sciences (2023).
2. Repeated superovulation may affect mitochondrial functions of cumulus cells in mice. Scientific Reports (2016).
3. Multiple superovulations alter histone modifications in mouse early embryos. Reproduction (2019).
4. Assessment of Repetitive Controlled Ovarian Stimulation (COS) Cycles on Oocyte Donors: Impact on Oocyte Quality and Viable Embryo Yield. Reproductive Sciences (2024).
5. Ameliorative Effect of Lycopene on Follicular Reserve Depletion, Oxidative Damage, Apoptosis Rate, and Hormonal Profile during Repeated Superovulations in Mice. Veterinary Sciences (2024).
6. Effects of Bushen-Tiaojing-Fang on the pregnancy outcomes of infertile patients with repeated controlled ovarian stimulation. Scientific Reports (2021).