Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (753 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
Female germ cells derived from oogonia and termed oocytes when they enter meiosis. The primary oocytes begin meiosis but are arrested at the diplotene state until ovulation at puberty to give rise to haploid secondary oocytes or ova (OVUM).
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Oocyte; Ovocytes; Ovocyte.
Where it fits in the MeSH classification
- Broader topics
- Ovum
- Narrower topics
- Polar Bodies
- See also
- In Vitro Oocyte Maturation Techniques
Related concepts
Research landscape
PubMed indexes 54,642 records tagged with the MeSH heading “Oocytes” (counts retrieved 2026-10-31). 8,074 of them (14.8%) were published from 2020 onward, and the busiest period so far is through 1999 with 17,186 records.
Reviews account for 4,515 records (8.3%) and meta-analyses for 115. Randomized controlled trials number 506 (0.9%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 17,186 |
| 2000-2009 | 15,690 |
| 2010-2019 | 13,692 |
| 2020 onward | 8,074 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 4,515 | 8.3% |
| Meta-analyses | 115 | 0.2% |
| Randomized controlled trials | 506 | 0.9% |
Method: PubMed query "Oocytes"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in anatomy and physiology
Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| The effect of chronic inflammation on female fertility | 2025 | Review article Design not recorded in structured metadata | 24 | cc by PMID 39932461 · DOI · PMC11896653 |
| RSPO2 Coordinates with GDF9:BMP15 Heterodimers to Promote Granulosa Cell and Oocyte Development in Mice | 2025 | Research article Design not recorded in structured metadata | 13 | cc by PMID 40492505 · DOI · PMC12376590 |
| The RNA m6A landscape during human oocyte-to-embryo transition | 2025 | Research article Design not recorded in structured metadata | 13 | cc by PMID 40467862 · DOI · PMC12264149 |
| Increased stiffness mimicking ovarian aging induces a fibroinflammatory response in follicles and impairs oocyte quality | 2026 | Research article Design not recorded in structured metadata | 12 | cc by PMID 41575513 · DOI · PMC13695885 |
The effect of chronic inflammation on female fertility [1]
Abstract reading summary — source excerpts
- Opening excerpt
- In briefChronic inflammation causes serious medical conditions in many organs and tissues, including female fertility.
- Closing excerpt
- Finally, we discuss the notion that in many cases, the effect of chronic inflammation is tightly correlated with and resembles the effect of aging, drawing interesting parallels between these processes, possibly through the effect of aging-associated inflammaging.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (226 words)
In briefChronic inflammation causes serious medical conditions in many organs and tissues, including female fertility. Here we review the current literature, showing that chronic inflammation has a negative impact on oocyte quality, folliculogenesis, hormone production, immune signaling and other processes that affect fertility in females.AbstractInflammation has key biological roles in the battle against pathogens and additional key processes in development and tissue homeostasis. However, when inflammation becomes chronic, it can become a serious medical concern. Chronic inflammation has been shown to contribute to the etiology and symptoms of serious medical conditions such as ulcerative colitis, cardiovascular diseases, endometriosis and various cancers. One of the less recognized symptoms associated with chronic inflammation is its effect on reproduction, specifically on female fertility. Here we review the current literature, showing that chronic inflammation has a negative impact on oocyte quality, folliculogenesis, hormone production, immune signaling and other processes that affect fertility in females. We discuss several factors involved in the etiology of chronic inflammation and its effect on female fertility. We also discuss possible mechanisms by which these effects may be mediated and how interventions may mitigate the effect of chronic inflammation. Finally, we discuss the notion that in many cases, the effect of chronic inflammation is tightly correlated with and resembles the effect of aging, drawing interesting parallels between these processes, possibly through the effect of aging-associated inflammaging.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 39932461 · DOI · PMC11896653
RSPO2 Coordinates with GDF9:BMP15 Heterodimers to Promote Granulosa Cell and Oocyte Development in Mice [2]
Abstract reading summary — source excerpts
- Opening excerpt
- The generation of mature oocytes, a cornerstone of reproduction, relies on the coordinated interactions between oocytes and surrounding follicular somatic cells.
- Closing excerpt
- These findings establish RSPO2 as an essential factor in the oocyte-granulosa cell regulatory loop, crucial for ovarian function and fertility.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (200 words)
The generation of mature oocytes, a cornerstone of reproduction, relies on the coordinated interactions between oocytes and surrounding follicular somatic cells. Central to this process is the bidirectional communication between the oocyte and granulosa cells, mediated by oocyte-secreted factors (OSFs), including GDF9 and BMP15. While GDF9 and BMP15 are well-established regulators of oocyte and follicle development, the role of additional OSFs and their coordination with GDF9 and BMP15 remains largely unclear. Here, RSPO2 is identified as a key OSF that coordinates with the GDF9:BMP15 heterodimer to regulate granulosa cell development and enhance oocyte competence. RSPO2, primarily expressed in oocytes, interacts with GDF9:BMP15 to preserve transcriptomic integrity in preantral granulosa cells. This coordination is gene-specific, exhibiting either synergistic or antagonistic effects depending on the target genes, and involves crosstalk between CTNNB1- and SMAD2-dependent pathways. Conditional knockout of Rspo2 in oocytes causes severe defects in granulosa cell and oocyte development, leading to subfertility and earlier reproductive lifespan termination. Transcriptomic analysis shows that RSPO2 loss disrupts key granulosa cell genes (e.g., Amh, Ccnd2, Inhbb, Kitl) and compromises oocyte mitochondrial function, reducing developmental competence. These findings establish RSPO2 as an essential factor in the oocyte-granulosa cell regulatory loop, crucial for ovarian function and fertility.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40492505 · DOI · PMC12376590
The RNA m6A landscape during human oocyte-to-embryo transition [3]
Abstract reading summary — source excerpts
- Opening excerpt
- RNA N6-methyladenosine (m6A, m6A) modification is a critical regulator for a range of physiological processes.
- Closing excerpt
- In summary, this study provides a resource to broaden our understanding about the regulatory roles of m6A during early human embryo development.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (151 words)
RNA N6-methyladenosine (m6A, m6A) modification is a critical regulator for a range of physiological processes. However, the dynamic m6A profiles within human preimplantation embryos remain uncharacterized. Here, we present the first RNA m6A landscape of single human oocytes and early embryos. Comparative analyses with mouse data reveal an intriguing divergence during the window of zygotic genome activation. m6A-modified genes are involved in regulation of gene transcription, while unmodified genes are mainly associated with basic metabolic processes. Maternal decay mRNAs exhibit a propensity for m6A modifications, and these genes are targeted by miRNAs. m6A modified genes that are constantly expressed across all stages demonstrate higher translation efficiency. Moreover, we observe frequent m6A enrichment on stage-specifically expressed retrotransposons, particularly within young subfamilies. m6A inhibitor leads to m6A erasure on massive retrotransposons. In summary, this study provides a resource to broaden our understanding about the regulatory roles of m6A during early human embryo development.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40467862 · DOI · PMC12264149
Increased stiffness mimicking ovarian aging induces a fibroinflammatory response in follicles and impairs oocyte quality [4]
Abstract reading summary — source excerpts
- Opening excerpt
- Reproductive aging in females is characterized by decreased ovarian reserve and oocyte quality.
- Closing excerpt
- Our findings demonstrate that follicles are highly mechanosensitive and that stiffness alone can trigger hallmarks of ovarian aging, including reduced follicle growth, reduced oocyte quality, and a fibroinflammatory phenotype potentially integrated into the oocyte via transzonal projections.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (176 words)
Reproductive aging in females is characterized by decreased ovarian reserve and oocyte quality. With aging, both mouse and human ovaries become pro-fibrotic and stiff. However, whether follicles sense and respond to microenvironmental stiffness and affect folliculogenesis and oocyte quality independent of other aging-related factors is unknown. To address this question, we cultured mouse secondary follicles in alginate hydrogels that reproduce the stiffness of reproductively young and old mice. RNA-sequencing revealed that follicles respond rapidly to increased stiffness and exhibit enrichment in genes related to inflammation and extracellular matrix remodeling. Long-term culture in stiff hydrogels resulted in reduced follicle survival, granulosa cell viability, estradiol synthesis, and oocyte quality. To begin to determine how stiffness is transmitted within the follicle, we examined transzonal projections, which mediate granulosa cell-oocyte communication and nutrient exchange. In stiff conditions, the number of transzonal projections decreased. Our findings demonstrate that follicles are highly mechanosensitive and that stiffness alone can trigger hallmarks of ovarian aging, including reduced follicle growth, reduced oocyte quality, and a fibroinflammatory phenotype potentially integrated into the oocyte via transzonal projections.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41575513 · DOI · PMC13695885
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance [5]
- Research article Oxidative stress in oocyte aging and female reproduction [6]
- Research article The Role of Mitochondria in Oocyte Maturation [7]
- Research article Clinical application of oocyte vitrification: a systematic review and meta-analysis of randomized controlled trials [8]
- Research article The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization [9]
- Research article Mitochondria: Their relevance during oocyte ageing [10]
References
- Ameho S, Klutstein M. The effect of chronic inflammation on female fertility. . 2025. PMID 39932461 · DOI · PMC11896653
- Wang Y, Li H, You L, Wang S, Bie J, Su Z, et al.. RSPO2 Coordinates with GDF9:BMP15 Heterodimers to Promote Granulosa Cell and Oocyte Development in Mice. . 2025. PMID 40492505 · DOI · PMC12376590
- Li Y, Wang Y, Cengiz A, Jin KX, Castroviejo BC, Lin X, et al.. The RNA m6A landscape during human oocyte-to-embryo transition. . 2025. PMID 40467862 · DOI · PMC12264149
- Pietroforte S, Amargant F. Increased stiffness mimicking ovarian aging induces a fibroinflammatory response in follicles and impairs oocyte quality. . 2026. PMID 41575513 · DOI · PMC13695885
- Rienzi L, Gracia C, Maggiulli R, LaBarbera AR, Kaser DJ, Ubaldi FM, et al.. Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance. Hum Reprod Update. 2017. PMID 27827818 · DOI · PMC5850862
- Wang L, Tang J, Wang L, Tan F, Song H, Zhou J, et al.. Oxidative stress in oocyte aging and female reproduction. J Cell Physiol. 2021. PMID 34121193 · DOI
- Kirillova A, Smitz JEJ, Sukhikh GT, Mazunin I. The Role of Mitochondria in Oocyte Maturation. Cells. 2021. PMID 34572133 · DOI · PMC8469615
- Cobo A, Diaz C. Clinical application of oocyte vitrification: a systematic review and meta-analysis of randomized controlled trials. Fertil Steril. 2011. PMID 21718983 · DOI
- Turathum B, Gao EM, Chian RC. The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization. Cells. 2021. PMID 34571941 · DOI · PMC8470117
- van der Reest J, Nardini Cecchino G, Haigis MC, Kordowitzki P. Mitochondria: Their relevance during oocyte ageing. Ageing Res Rev. 2021. PMID 34091076 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.