Expression of fractalkine in the rat testis: molecular cloning of a novel alternative transcript of its gene that is differentially regulated by pro-inflammatory cytokines.

The testis is a very complex organ in which cellular communications and interactions are central to spermatogenesis and where inflammatory processes can lead to sterility. Fractalkine (CX3CL1) is a chemokine involved in cell-cell interactions and in leukocyte chemoattraction. It has been reported to be expressed in testis, but its cellular expression and function in this organ has not been described. In this study we report constitutive expression of fractalkine in the testis. Expression is higher in Leydig cells than Sertoli cells, spermatogonia, pachytene spermatocytes and elongated spermatids. In both, Sertoli cells stimulated by interleukin-1beta and tumour necrosis factor alpha, and in Leydig cells, two forms of fractalkine mRNA were observed: the previously described transcript of 3.7 kb and a novel transcript of 4.2 kb. The 4.2 kb transcript has a 5' elongation and is differentially regulated. To investigate fractalkine function in testis, we abolished Leydig cell expression of fractalkine by specific destruction of this cell type using ethylene dimethane sulphonate. The absence of fractalkine expression in Leydig cells did not seem to affect the fractalkine expression by other testicular cells. In addition, the destruction of testicular macrophages by Cl2MDP (chlodronate) did not seem to affect Leydig cell expression of fractalkine. We conclude that Leydig cell expression of fractalkine could be preferentially involved in inflammation in interstitial space whereas fractalkine expressed by germ cells may participate in the cellular interactions between germ cells and other seminiferous tubule cell types.

Study of the HIV-1 receptors CD4, CXCR4, CCR5 and CCR3 in the human and rat testis.

Sexual transmission of HIV is one of the main routes of transmission of AIDS. Despite the fact that the virus has been found in the semen and germ cells of patients with HIV, little is known about how the virus infects the cells of the genital tract. We studied the cellular distribution of CD4, a receptor necessary for HIV infection, and the major HIV co-receptors CCR3, CCR5 and CXCR4 in the rat and human testis. We used RT-PCR, Northern blotting and immunohistochemistry to demonstrate that CCR3 is absent from the testes of both species, whereas CCR5 and CXCR4 are present on the resident testicular macrophages in the interstitial space but not in the germ cell line. All of the human testicular macrophages expressed the markers CD45 and MAC387 and most also expressed CD4. Thus, our data suggest that macrophages in the testis may be infected by HIV and that these macrophages may be a site of early viral localization and a potential HIV reservoir. This may in turn alter the activity of Leydig cells and subsequently affect spermatogenesis.