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Updated: Jan 3, 2026
Analysis of Epididymal Protein Synthesis and Secretion
Published on: August 25, 2018
Region-specific transcriptomic and functional signatures of mononuclear phagocytes in the epididymis
Maria A Battistone1, Alexandra C Mendelsohn1, Raul German Spallanzani2
1Program in Membrane Biology, Center for Systems Biology and Division of Nephrology, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States.
Abstract:
In the epididymis, prevention of autoimmune responses against spermatozoa and simultaneous protection against pathogens is important for male fertility. We have previously shown that mononuclear phagocytes (MPs) are located either in the epididymal interstitium or in close proximity to the epithelium. In the initial segments (IS), these 'intraepithelial' MPs extend slender luminal-reaching projections between epithelial cells. In this study, we performed an in-depth characterisation of MPs isolated from IS, caput-corpus and cauda epididymis of CX3CR1EGFP+/- mice that express EGFP in these cells. Flow cytometry analysis revealed region-specific subsets of MPs that express combinations of markers traditionally described in 'dendritic cells' or 'macrophages'. RNA sequencing identified distinct transcriptomic signatures in MPs from each region and revealed specific genes involved in inflammatory and anti-inflammatory responses, phagosomal activity and antigen processing and presentation. Functional fluorescent in vivo labelling assays showed that higher percentages of CX3CR1+ MPs that captured and processed antigens were detected in the IS compared to other regions. Confocal microscopy showed that in the IS, caput and corpus, circulatory antigens were internalised and processed by interstitial and intraepithelial MPs. However, in the cauda only interstitial MPs internalised and processed antigens, while intraepithelial MPs did not take up antigens, indicating that all antigens have been captured before they reached the epithelial lining. Cauda MPs may thus confer a stronger protection against blood-borne pathogens compared to proximal regions. By identifying immunoregulatory mechanisms in the epididymis, our study may lead to new therapies for male infertility and epididymitis and identify potential targets for immunocontraception.
Insights
Mononuclear phagocytes in the epididymis exhibit region-specific functions. Initial segment cells capture antigens, while cauda cells provide enhanced pathogen protection, crucial for male fertility.
Area of Science:
- Immunology
- Reproductive Biology
- Cell Biology
Background:
- Mononuclear phagocytes (MPs) are crucial for immune homeostasis in the epididymis, balancing self-tolerance and pathogen defense for male fertility.
- Previous work identified MPs in epididymal interstitium and epithelium, with specific 'intraepithelial' MPs extending projections in initial segments (IS).
Purpose of the Study:
- To comprehensively characterize epididymal mononuclear phagocytes (MPs) across different regions (IS, caput-corpus, cauda) using transcriptomic and functional analyses.
- To elucidate region-specific immune functions of MPs, particularly their role in antigen capture and processing, to understand male reproductive tract immunity.
Main Methods:
- Isolation and flow cytometry analysis of MPs from CX3CR1EGFP+/- mice epididymis.
- RNA sequencing to determine transcriptomic signatures of MPs from different epididymal regions.
- In vivo fluorescent labeling assays and confocal microscopy to assess antigen uptake and processing by MPs.
Main Results:
- MPs displayed region-specific subsets and distinct transcriptomic profiles, with genes related to inflammation, phagocytosis, and antigen presentation varying by location.
- Initial segment (IS) MPs showed higher antigen capture and processing rates compared to other regions.
- In IS, caput, and corpus, both interstitial and intraepithelial MPs processed antigens; however, only interstitial MPs in the cauda did so, suggesting proximal capture.
Conclusions:
- Epididymal MPs exhibit significant regional specialization in immune surveillance and antigen handling.
- Cauda epididymis MPs may offer superior protection against blood-borne pathogens due to efficient antigen capture before reaching the epithelium.
- Understanding these immunoregulatory mechanisms can inform therapies for male infertility, epididymitis, and novel immunocontraception strategies.
