Antimicrobial Protection of the Mouse Testis: Synthesis of Defensins of the

We report the synthesis by mouse testicular cells of antibiotic peptides related to the defensins secreted by the Paneth cells of the intestinal epithelium. A Sertoli cell-derived line (15P-1), Ser-toli cells in primary cultures, and explanted testicular tissue in culture medium were observed to release protease-sensitive ma-terial with a broad-spectrum antibacterial activity. The activity of 15P-1 culture medium was increased 10- to 50-fold in the presence of fractions enriched in round spermatids and of nerve growth factor. Two series of results suggest that this activity may correspond to the release by testicular cells of defensin peptides, and specifically, of peptides of the cryptdin family first identified in the Paneth cells of intestinal crypts. First, a characteristic nu-cleotide sequence corresponding to the conserved first exon of the mouse cryptdin and cryptdin-related (CRS) genes was evi-denced in the RNA of 15P-1 cells and of the testis. Second, immunohistochemical analysis demonstrated the presence of cryptdins of the cryp-1,-2,-3,-6 group in 15P-1 cells, and iden-tified two distinct localizations in the testis. Inside the seminif-erous tubule, these cryptdins were found accumulated in Sertoli cells at stages corresponding to the maturation of spermatids. In the interstitial space, Leydig cells also contained immuno-reactive cryptdins