Monocyte chemoattractant protein-1 (MCP-1/CCL2) in experimental autoimmune orchitis

Experimental autoimmune orchitis (EAO) is characterized by an interstitial mononuclear cell infiltrate and a severe lesion of seminiferous tubules with germ cells that undergo apoptosis and sloughing. The mechanism by which immune cells migrate and extravasate in the testicular interstitium is poorly understood. The aim of this study was to detect the variations in the expression of monocyte chemoattractant protein-1 (MCP-1/CCL2) and its receptor in the testis of rats undergoing autoimmune orchitis. EAO was induced in Sprague-Dawley adult rats by active immunization with an emulsion of testicular homogenate and complete Freund adjuvant using Bordetella pertussis as co-adjuvant. Control rats injected with saline and adjuvants and normal untreated rats were also studied. By ELISA we observed a significant increase of MCP-1 in the testicular fluid (TF) and in the conditioned medium obtained from cultures of testicular macrophages of rats with EAO compared with control groups. By immunohistochemistry, an increase in MCP-1 expression was observed in mononuclear, endothelial, Leydig and peritubular cells. MCP-1 immunoreactivity was also detected in Sertoli cell cytoplasm of rats with severe orchitis. A 2-fold increase in the number of mononuclear cells that express CCR2 was also found in rats with orchitis compared with controls. In conclusion, we demonstrated in vivo that MCP-1 is highly expressed in testicular interstitial cells suggesting that this chemokine has an important role in recruiting immune cells to the testis in rats undergoing autoimmune orchitis.