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Mitosis of resident macrophages in the adult rat testis
S Schlatt1, D M de Kretser, M P Hedger
1Institute of Reproduction and Development, Monash University, Monash Medical Centre, Clayton, Australia.
Abstract:
Resident macrophages are maintained at a comparatively high, yet stable, tissue concentration in the adult rat testis. After destruction of Leydig cells by ethane dimethane sulphonate treatment, the number of resident macrophages increases briefly and then decreases to below normal values, but returns to normal after the reappearance of Leydig cells. The mechanisms by which the adult testicular macrophage population is maintained, either by monocyte recruitment or by mitosis of the resident macrophages, have not been examined. An immunohistochemical dual labelling approach using a specific monoclonal antibody for resident macrophages, ED2, and markers of mitotic activity (bromodeoxyuridine incorporation and expression of the proliferating cell nuclear antigen) was used to investigate resident macrophage proliferation in Bouin's-fixed paraffin wax-embedded adult rat testes. Detection of the normally fixation sensitive antigen recognized by ED2 was achieved by using a decreased fixation time and antigen retrieval. Peaks of resident macrophage mitotic activity were observed during the phases of macrophage proliferation immediately after ethane dimethane sulphonate treatment and during the recovery phase associated with Leydig cell restoration. These data demonstrate that resident macrophages have the capacity to proliferate within the adult rat testis and, thus, this population of resident macrophages is maintained, at least in part, by mitotic division in situ.
Insights
Adult rat testicular macrophages proliferate to maintain their population. This study shows resident macrophages divide in situ, particularly after Leydig cell damage and during recovery, confirming their self-renewal capacity.
Area of Science:
- Reproductive biology
- Immunology
- Cell biology
Background:
- Resident macrophages maintain a stable concentration in adult rat testes.
- Leydig cell destruction alters testicular macrophage numbers, but maintenance mechanisms remain unclear.
- Potential mechanisms include monocyte recruitment or resident macrophage mitosis.
Purpose of the Study:
- To investigate the proliferation of resident macrophages in the adult rat testis.
- To determine if resident macrophages can divide in situ.
- To examine the role of resident macrophage proliferation in response to Leydig cell changes.
Main Methods:
- Immunohistochemical dual labeling using ED2 antibody for resident macrophages.
- Assessment of mitotic activity via bromodeoxyuridine incorporation and proliferating cell nuclear antigen.
- Optimized fixation and antigen retrieval for sensitive ED2 antigen detection.
Main Results:
- Peaks of resident macrophage mitotic activity were observed.
- Proliferation occurred after ethane dimethane sulphonate-induced Leydig cell destruction.
- Increased mitotic activity coincided with Leydig cell restoration during the recovery phase.
Conclusions:
- Resident macrophages possess the capacity for mitotic division within the adult rat testis.
- The resident macrophage population is maintained, at least partially, by in situ proliferation.
- This finding clarifies the self-renewal mechanism of testicular macrophages.
