Macrophage Interactions in Testicular Function

Macrophages within the testis constitute a specialised network of immune cells that extend far beyond host defence, orchestrating key aspects of organ development, immune privilege, spermatogenesis and steroid hormone production. Distinct populations—interstitial macrophages nestled among Leydig cells and peritubular macrophages arrayed around seminiferous tubules—derive from both yolk‐sac and haematopoietic stem‐cell lineages, establish long‐lived tissue residency and perform complementary roles. Interstitial macrophages furnish trophic signals that enhance Leydig‐cell steroidogenesis, while peritubular macrophages modulate the microenvironment of Sertoli cells and developing germ cells. Their ability to adopt pro‐inflammatory (M1) or anti‐inflammatory (M2) states ensures a dynamic balance between defence against infection and maintenance of immune privilege. Disruption of macrophage function, whether by aberrant recruitment, imbalanced polarisation or inflammatory insult, can impair germ‐cell differentiation, hinder testosterone synthesis and contribute to male infertility or age‐related decline in testicular function. A growing body of research is uncovering the molecular dialogues—cytokines, growth factors and direct cell–cell contacts—through which testicular macrophages sustain organ homeostasis and adapt to physiological and pathological challenges.

Research from Nature Portfolio

Recent studies using lineage tracing and single‐cell profiling have refined understanding of macrophage ontogeny and function within the developing testis. In one investigation, yolk‐sac‐derived macrophages were shown to seed the early gonad and support morphogenesis, while foetal haematopoietic stem‐cell–derived monocytes that colonise the testis during a narrow developmental window differentiate into adult interstitial and peritubular macrophages. Functional assays revealed that interstitial macrophages specifically potentiate Leydig‐cell steroidogenesis, whereas yolk‐sac‐derived counterparts primarily guide testicular vascular patterning. A complementary analysis employing high‐dimensional single‐cell sequencing delineated foetal‐liver versus embryonic precursors as the main contributors to interstitial and peritubular pools, respectively, and demonstrated that the prenatal presence of both macrophage types is indispensable for normal postnatal spermatogenesis. Together, these findings challenge previous dogma by clarifying the differentiation pathways, tissue‐specific roles and homeostatic maintenance of testicular macrophage populations.

Macrophage Interactions in Testicular Function publication trend

The graph below shows the total number of articles in macrophage interactions in testicular function across all publications each year (not limited to Nature Index journals).

Technical terms

Testicular macrophages: Resident immune cells in the testis that regulate development, immune privilege and hormone synthesis.

Interstitial macrophages: Macrophages located in the connective tissue between seminiferous tubules, closely associated with Leydig cells to support steroidogenesis.

Peritubular macrophages: Macrophages positioned around the walls of seminiferous tubules, influencing the germ‐cell niche and Sertoli‐cell function.

Steroidogenesis: The biosynthetic process by which steroid hormones, notably testosterone, are produced from cholesterol.

Polarisation: Functional programming of macrophages into pro‐inflammatory (M1) or anti‐inflammatory (M2) phenotypes in response to environmental cues.

References

1. Testicular macrophages are recruited during a narrow fetal time window and promote organ-specific developmental functions. Nature Communications (2023).
2. Generation, localization and functions of macrophages during the development of testis. Nature Communications (2020).
3. Macrophage-Related Testicular Inflammation in Individuals with Idiopathic Non-Obstructive Azoospermia: A Single-Cell Analysis. International Journal of Molecular Sciences (2023).
4. Mouse testicular macrophages can independently produce testosterone and are regulated by Cebpb. Biological Research (2024).
5. Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Rescue Testicular Aging. Biomedicines (2024).