Testicular macrophages: core immune regulators and emerging therapeutic targets in spermatogenic dysfunction

A review of mouse studies argues rogue immune cells in the testis may drive some male infertility

Journal: Frontiers in Immunology | Published: 2026-06-23 | Type: Journal Article, Review | PMID: 42416067 Authors: Jiang Zesong, Xuan Xiaohe, Qiu Zhongjian, Zhou Xiang, Ma Hui, Zhu Zhiguo (Jining Medical University; Third Affiliated Hospital of Guangxi Medical University; Qingdao University) Funding/COI: No funding source listed. Authors declared no conflicts of interest.

Summary

This is a narrative review, not a new experiment. It compiles existing research on testicular macrophages, immune cells that normally keep the testis in a tolerant, inflammation-dampened state so sperm production can proceed undisturbed. The authors argue that when these macrophages shift toward a pro-inflammatory state, that shift correlates with spermatogenic dysfunction, including non-obstructive azoospermia, and they catalog several experimental interventions tested so far, entirely in animals.

Claims

• Testicular macrophages normally adopt immune-tolerance phenotypes that maintain the testis's immune-privileged status and support hormonal balance.
• In spermatogenic dysfunction, macrophage number, location, and activation state (notably M1 versus M2 polarization) shift, and this is linked to chronic low-grade inflammation in animal models.
• In mice, INSL3 signaling or corticosterone supplementation pushed testicular macrophages toward an anti-inflammatory M2-like phenotype.
• Blocking CMKLR1 signaling suppressed inflammatory activity and restored immunometabolic balance in experimental models.
• Transplanted stem Leydig cells (SLCs) modulated macrophage function via mitochondrial transfer, reducing testicular inflammation and aiding tissue repair in animal studies.

Study Quality

This is not a primary study and has no sample size, control group, or human cohort of its own, it is a literature synthesis. Its value depends entirely on how comprehensively and critically it handles the underlying primary studies, none of which are detailed here with their own methodological specifics (species, group sizes, blinding, replication). The abstract and conclusion are explicit that the evidence base is almost entirely rodent and in vitro work.

The authors themselves flag the central limitation: "most current studies remain confined to basic research and animal models, with a lack of high-quality human sample data and robust clinical evidence." That is an unusually candid admission for a review to make about its own subject matter, and it should be taken at face value rather than glossed over.

Red Flags

• Zero human clinical data underlies any of the therapeutic strategies discussed (M1/M2 polarization modulation, signaling pathway inhibition, stem cell transplantation).
• No funding source disclosed, funding transparency for the underlying primary literature is not addressed either.
• As a review, it inherits whatever selection and publication bias exists in the primary papers it cites, and this article gives no indication of a systematic search methodology (e.g., PRISMA), it appears to be a narrative rather than systematic review.
• "Emerging therapeutic targets" in the title outpaces what the content supports, everything described is preclinical.

Strengths

• Authors are transparent about the animal-only, non-clinical state of the evidence rather than overselling translational readiness.
• Synthesizes a fragmented mechanistic literature (macrophage origin, polarization, signaling pathways like NLRP3, NF-κB, CCR2) that would otherwise require chasing down dozens of separate papers.
• Ties immune mechanisms directly to a specific, common clinical entity (non-obstructive azoospermia) rather than staying purely theoretical.

Verdict

Useful as a mechanistic map for anyone trying to understand the immunology behind male infertility, but this is a review of mouse-level biology dressed up with a title that implies clinical relevance it doesn't have. Worth reading if you want the current state of testicular immunology; worth ignoring if you're looking for anything resembling a near-term treatment.