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: 3 complete abstracts (597 words), 9 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
Mature male germ cells derived from spermatids. As spermatids move toward the lumen of the seminiferous tubules, they undergo extensive structural changes including the loss of cytoplasm, condensation of chromatin into the sperm head, formation of the acrosome cap, the sperm midpiece and the sperm tail that provides motility.
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: Sperm; Spermatozoon; X-Chromosome-Bearing Sperm; Sperms, X-Chromosome-Bearing; Sperm, X-Chromosome-Bearing; X Chromosome Bearing Sperm; X-Chromosome-Bearing Sperms; X-Bearing Sperm.
Where it fits in the MeSH classification
- Broader topics
- Germ Cells
- Narrower topics
- Sperm Head; Sperm Midpiece; Sperm Tail; Spermatids; Spermatocytes; Spermatogonia
- See also
- Antispermatogenic Agents; Oligospermia; Sperm Banks; Spermatocidal Agents
Related concepts
- Spermatids
- Seminiferous Tubules
- Chromatin
- Sperm Head
- Acrosome
- Sperm Midpiece
- Sperm Tail
Research landscape
PubMed indexes 79,720 records tagged with the MeSH heading “Spermatozoa” (counts retrieved 2026-10-31). 12,780 of them (16.0%) were published from 2020 onward, and the busiest period so far is through 1999 with 33,638 records.
Reviews account for 6,681 records (8.4%) and meta-analyses for 246. Randomized controlled trials number 447 (0.6%) 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 | 33,638 |
| 2000-2009 | 15,226 |
| 2010-2019 | 18,076 |
| 2020 onward | 12,780 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 6,681 | 8.4% |
| Meta-analyses | 246 | 0.3% |
| Randomized controlled trials | 447 | 0.6% |
Method: PubMed query "Spermatozoa"[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 |
|---|---|---|---|---|
| Cleavage of mRNAs by a minority of pachytene piRNAs improves sperm fitness | 2026 | Research article Design not recorded in structured metadata | 9 | cc by PMID 41639461 · DOI · PMC13061629 |
| Conserved shifts in sperm small non-coding RNA profiles during mouse and human aging | 2026 | Research article Design not recorded in structured metadata | 9 | cc by PMID 41559200 · DOI · PMC12909834 |
| Targeting SKAP2 restores sperm motility and morphology through modulating mitochondrial organization and cytoskeletal remodeling | 2025 | Research article Design not recorded in structured metadata | 5 | cc by PMID 41436426 · DOI · PMC12727759 |
Cleavage of mRNAs by a minority of pachytene piRNAs improves sperm fitness [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Animals use 18-33-nucleotide PIWI-interacting RNAs (piRNAs) to silence transposons in germ cells1-3.
- Closing excerpt
- Together, our findings explain the lack of conservation of most pachytene piRNA sequences and suggest that these 'selfish' small RNAs persist in mammalian evolution because target cleavage by a tiny minority of piRNAs supports male 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 (190 words)
Animals use 18-33-nucleotide PIWI-interacting RNAs (piRNAs) to silence transposons in germ cells1-3. In addition to transposon-silencing piRNAs, placental mammals make pachytene piRNAs4,5, an abundant class of testis-specific small RNAs derived from long noncoding RNA precursors. Although the sites of pachytene piRNA precursor transcription are often conserved among placental mammals, the sequences of the piRNAs themselves are rapidly diverging, even in the human population6. Consequently, the biological function and mechanism of action of pachytene piRNAs remain debated. Here we report that most mouse pachytene piRNAs have no biological function but instead 'selfishly' promote their own production. Our data suggest that pachytene piRNAs direct endonucleolytic cleavage of partially complementary targets and neither activate nor repress mRNA translation. Although many pachytene piRNAs guide cleavage of specific mRNAs, few alter the steady-state abundance of their targets. The minority of pachytene piRNAs that reduce target mRNA abundance enhance sperm fitness, thereby ensuring production of the entire pachytene piRNA repertoire. Together, our findings explain the lack of conservation of most pachytene piRNA sequences and suggest that these 'selfish' small RNAs persist in mammalian evolution because target cleavage by a tiny minority of piRNAs supports male fertility.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41639461 · DOI · PMC13061629
Conserved shifts in sperm small non-coding RNA profiles during mouse and human aging [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Sperm aging impacts male fertility and offspring health, highlighting the need for reliable aging biomarkers to guide reproductive decisions.
- Closing excerpt
- These findings provide novel insights into longitudinal dynamics of sncRNAs during sperm aging, highlighting an rsRNA length shift conserved in mice and humans.
- 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)
Sperm aging impacts male fertility and offspring health, highlighting the need for reliable aging biomarkers to guide reproductive decisions. However, the molecular determinants of sperm fitness during aging remain ill-defined. Here, we profiled sperm small non-coding RNAs (sncRNAs) using PANDORA-seq, which overcomes RNA modification-induced detection bias to capture previously undetectable sncRNA species associated with mouse and human spermatozoa throughout the lifespan. We identified an "aging cliff" in mouse sperm RNA profiles-a sharp age-specific transition marked by significant shifts in genomic and mitochondrial tRNA-derived small RNAs (tsRNAs) and rRNA-derived small RNAs (rsRNAs). Notably, rsRNAs in mouse sperm heads exhibited a transformative length shift, with longer rsRNAs increasing and shorter ones decreasing with age, suggesting altered biogenesis or processing with age. Remarkably, this sperm head-specific shift in rsRNA length was consistently observed in two independent human aging cohorts. Moreover, transfecting a combination of tsRNAs and rsRNAs resembling the RNA species in aged sperm was able to induce transcriptomic changes in mouse embryonic stem cells, impacting metabolism and neurodegeneration pathways, mirroring the phenotypes observed in offspring fathered by aged sperm. These findings provide novel insights into longitudinal dynamics of sncRNAs during sperm aging, highlighting an rsRNA length shift conserved in mice and humans.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41559200 · DOI · PMC12909834
Targeting SKAP2 restores sperm motility and morphology through modulating mitochondrial organization and cytoskeletal remodeling [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Sperm motility and morphology are indispensable for sperm-egg interaction and successful fertilization.
- Closing excerpt
- Altogether, these findings identify hnRNPR as a pivotal regulator of m6A-mediated Skap2 splicing during spermiogenesis and highlight extracellular vesicle SKAP2 as a promising therapeutic target for poor sperm quality and male infertility.
- 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 (207 words)
Sperm motility and morphology are indispensable for sperm-egg interaction and successful fertilization. However, the RNA splicing mechanisms in an m6A-dependent manner regulating spermiogenesis-related genes remain poorly defined, and targeted therapy strategies to restore impaired sperm motility and morphology are lacking. In this study, we identify heterogeneous nuclear ribonucleoprotein R (hnRNPR) as a critical m6A-dependent splicing mediator. Pathogenic mutations in HNRNPR cause sperm motility decline, morphological abnormality, and male infertility in both humans and mice. Mechanistically, Hnrnpr mutation disrupts m6A-dependent splicing of Skap2 pre-mRNA, thus impairing cytoskeletal structure and mitochondrial organization in sperm. Consistently, specific knockout of Skap2 in male germ cells displays sperm abnormalities, which phenocopy those observed in humans and mice with Hnrnpr mutants, unveiling a functional hnRNPR-SKAP2 axis. Leveraging these insights, we developed a therapeutic strategy to restore sperm motility and morphology, relying on extracellular vesicle-mediated SKAP2 delivery to enter the efferent ductules of the testicles, which could promote sperm cytoskeletal remodeling and mitochondrial organization. Notably, the co-culture of extracellular vesicle SKAP2 with human and mouse sperms also significantly enhanced the sperm motility. Altogether, these findings identify hnRNPR as a pivotal regulator of m6A-mediated Skap2 splicing during spermiogenesis and highlight extracellular vesicle SKAP2 as a promising therapeutic target for poor sperm quality and male infertility.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41436426 · DOI · PMC12727759
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 BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis [4]
- Research article The effect of sperm DNA fragmentation on miscarriage rates: a systematic review and meta-analysis [5]
- Research article A systematic review and meta-analysis to determine the effect of sperm DNA damage on in vitro fertilization and intracytoplasmic sperm injection outcome [6]
- Research article Measuring Sperm DNA Fragmentation and Clinical Outcomes of Medically Assisted Reproduction: A Systematic Review and Meta-Analysis [7]
- Research article The effect of sperm DNA fragmentation on live birth rate after IVF or ICSI: a systematic review and meta-analysis [8]
- Research article Paternal obesity negatively affects male fertility and assisted reproduction outcomes: a systematic review and meta-analysis [9]
References
- Cecchini K, Zamani M, Ajaykumar N, Vega-Badillo J, Bagci A, Bailey S, et al.. Cleavage of mRNAs by a minority of pachytene piRNAs improves sperm fitness. . 2026. PMID 41639461 · DOI · PMC13061629
- Shi J, Zhang X, Cai C, Liu S, Yu J, James ER, et al.. Conserved shifts in sperm small non-coding RNA profiles during mouse and human aging. . 2026. PMID 41559200 · DOI · PMC12909834
- Gan S, Yin L, Zhou J, Li S, Zhou S, Yang X, et al.. Targeting SKAP2 restores sperm motility and morphology through modulating mitochondrial organization and cytoskeletal remodeling. . 2025. PMID 41436426 · DOI · PMC12727759
- Sermondade N, Faure C, Fezeu L, Shayeb AG, Bonde JP, Jensen TK, et al.. BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis. Hum Reprod Update. 2013. PMID 23242914 · DOI · PMC3621293
- Robinson L, Gallos ID, Conner SJ, Rajkhowa M, Miller D, Lewis S, et al.. The effect of sperm DNA fragmentation on miscarriage rates: a systematic review and meta-analysis. Hum Reprod. 2012. PMID 22791753 · DOI
- Simon L, Zini A, Dyachenko A, Ciampi A, Carrell DT. A systematic review and meta-analysis to determine the effect of sperm DNA damage on in vitro fertilization and intracytoplasmic sperm injection outcome. Asian J Androl. 2017. PMID 27345006 · DOI · PMC5227680
- Cissen M, Wely MV, Scholten I, Mansell S, Bruin JP, Mol BW, et al.. Measuring Sperm DNA Fragmentation and Clinical Outcomes of Medically Assisted Reproduction: A Systematic Review and Meta-Analysis. PLoS One. 2016. PMID 27832085 · DOI · PMC5104467
- Osman A, Alsomait H, Seshadri S, El-Toukhy T, Khalaf Y. The effect of sperm DNA fragmentation on live birth rate after IVF or ICSI: a systematic review and meta-analysis. Reprod Biomed Online. 2015. PMID 25530036 · DOI
- Campbell JM, Lane M, Owens JA, Bakos HW. Paternal obesity negatively affects male fertility and assisted reproduction outcomes: a systematic review and meta-analysis. Reprod Biomed Online. 2015. PMID 26380863 · 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.