Expression of interferons-alpha and -gamma in testicular interstitial tissue and spermatogonia of the rat.

The testis is divided into two compartments: the seminiferous tubules and the interstitial tissue. The latter essentially consists of the blood and lymphatic vessels, testosterone-producing Leydig cells, and testicular macrophages. In the exploration of the testicular antiviral defense system, we initially searched for interferon (IFN) production by the seminiferous tubule cells. The site of virus entry into the testis is probably the interstitial compartment; thus, it is important to know whether and how the cells in this compartment are protected against viral infection. In addition, as germ cell precursors (spermatogonia) are only partially protected by the blood-testis barrier, it was important to explore the antiviral capability of these cells. In this study we searched for IFN production by Leydig cells, testicular macrophages, and spermatogonia after exposure to Sendai virus. We also investigated the effect of viral exposure on testosterone production by Leydig cells. Our results show that spermatogonia do not constitutively express IFNs and give a very poor response to the virus. In contrast, testicular macrophages constitutively produced type I IFNs, and this production was markedly stimulated by Sendai virus. Leydig cells produced twice as much type I IFNs as testicular macrophages after viral exposure, and they were the only cells producing both IFNalpha and -gamma, with these IFNs being dramatically induced/ increased in response to exposure to the virus. Furthermore, incubation of Leydig cells with the Sendai virus stimulated testosterone production. In conclusion, this study further establishes the topography of IFN expression within the testis. This allows us to hypothesize that the potential antiviral system represented by Leydig cells and, to a lesser extent, by macrophages plays a key role in protecting both androgen production and spermatogenesis.

The olfactory adenylyl cyclase type 3 is expressed in male germ cells.

Elements of the olfactory pathway, such as receptors, receptor-desensitization machinery, and cyclic nucleotide-gated channels, are expressed in male germ cells. Here we report the expression, in rat testis, of both adenylyl cyclase type 3 (AC3) and the olfactory G protein subunit, G(alpha)olf. Both are expressed in the same sub-population of germ cells, pachytene spermatocytes to spermatids, and in residual bodies. Neither AC3 nor G(alpha)olf was found in Sertoli or in peritubular cells, as shown by Western blotting and immunocytochemical analyses. It thus appears that male germ cells contain all the elements of the signaling cascade present in olfactory cells.

Interferons and interferon-induced antiviral proteins in the testis.

Despite the dramatic development of sexually transmissible diseases, the antiviral capabilities of testicular cells have not yet been explored. Interferons (IFNs) are proteins playing a key role in the antiviral defense system, their activity being mediated by several IFN-induced proteins. In the present study, we have investigated both the expression of IFN and of the three main IFN-induced proteins by isolated testicular cells. The highest responders to a viral stimulation in terms of IFN production are the Leydig and the Sertoli cells, followed by peritubular cells and testicular macrophages, while germ cells are devoid or virtually devoid of IFN and IFN-induced protein expression. Sertoli cells constitutively expressed the three IFN-induced proteins tested, and their levels were greatly increased after exposure to Sendai virus. Peritubular cells were also able to markedly express these three proteins after viral exposure. In conclusion, we hypothesize that, for a virus coming from the blood, the first testicular line of defence is ensured by Leydig cells and testicular macrophages, the second line being ensured by the myoid cells, lining the seminiferous tubules, and by Sertoli cells. These two barriers are probably fundamental in protecting both androgen production and spermatogenesis.

Type I and type II interleukin-1 receptor expression in rat, mouse, and human testes.

Despite clear indications of interleukin-1 (IL-1) action on Sertoli and germ cells, previous studies failed to detect IL-1 receptors (IL-1R) within the seminiferous tubules. Here, we investigated the existence of the type I signaling receptor (IL-1RI) and the type II decoy receptor (IL-1RII) mRNAs within the testis. Polymerase chain reaction analysis showed the presence of both receptor mRNAs in isolated rat, mouse, and human somatic testicular cells (macrophages, Leydig, Sertoli, and peritubular cells). While also present in rat and mouse isolated pachytene spermatocytes and early spermatids, these receptor mRNAs were not found in human germ cells. The distribution of both IL-1R mRNAs was then examined in adult rat and mouse testis using light and electron microscopic in situ hybridization. No IL-1RI signal was detected in rat testis. In mouse testis, we did not find any signal for IL-1RII. In contrast, IL-1RI mRNA was detected in a wide variety of mouse testicular cells. Strong expression was observed in the rete testis area and high expression was seen over the epithelium of the epididymal duct and in interstitial cells, while lower labeling was detected in peritubular and Sertoli cells and in all germ cell types from spermatogonia to early spermatids; no signal was seen in late spermatids. That the IL-IR was also strongly expressed in the interstitium, the rete testis and efferent duct areas, and the epididymis was established using an autoradiography technique. Overall, our study strongly supports the hypothesis that IL-1 is a regulator of testicular function of prime importance.