Lymphangiogenesis in chronic inflammation in the testis

Lymphangiogenesis occurs in various organs under inflammatory conditions. Recently, it was demonstrated that activated macrophages play an important role in the process of lymphangiogenesis. However, lymphangiogenesis during testicular inflammation has not yet been studied. Here, we investigated lymphangiogenesis in experimental autoimmune orchitis, a immunologic male infertility model, in mice. Histological changes were observed using immunohistochemical staining with the monoclonal antibodies against F4/80 (mature macrophage marker), lymph vessel endothelium HA-receptor 1 (LYVE-1) (lymphatic endothelial cells marker) and CD31 (endothelial cells marker). The expression of angiogenesis and lymphangiogenesis factors, such as vascular endothelial growth factor (VEGF)-A, VEGF-C, VEGF-D and TNF-α, which are secreted by activated macrophages, were examined using real-time RT-PCR. The results showed that lymphangiogenesis occurred along the undersurface of the tunica albuginea but not into the interstitium proper between the seminiferous tubules (STs) during the orchitis. It was noted that some F4/80-positive macrophages expressed LYVE-1 at the undersurface of the tunica albuginea and also in the testicular interstitium proper. RT-PCR analysis revealed that the expressions of VEGF-A, VEGF-D and TNF-α were significantly increased but that of VEGF-C remained unchanged in the inflammatory testes. This study suggests that testicular macrophages are involved in the specific lymphangiogenesis in the chronic inflammation.