Expression of Avian β-Defensin 3, an Antimicrobial Peptide, by Sperm in the Male Reproductive Organs and Oviduct in Chickens: An Immunohistochemical Study

The aim of this study was to determine whether chicken sperm express avian beta-defensin 3 (AvBD-3), an antimicrobial peptide, and retain it during the residence in the male and female reproductive tract. Immunocytochemistry to identify AvBD-3 was performed in the testis, epididymis, ductus deferens, ejaculated sperm, and utero-vaginal junction of the oviduct of inseminated hens. Reverse transcription-PCR analysis was also performed to confirm the synthesis of AvBD-3 by testicular cells and ejaculated sperm. The immunoreaction products for AvBD-3 were identified in the elongated spermatids attached to the seminiferous epithelium and in the sperm in the lumen of seminiferous tubules. Immunoreaction products were found in the sperm in the epididymal ducts and ductus deferens. In the ejaculated sperm, immunoreaction products were distributed in the midpiece and cephalic region of the tail of sperm, but not in the head. The AvBD-3 immunoreaction products were also identified in the sperm stored in the sperm storage tubules in the uterovaginal junction. Reverse transcription-PCR analysis showed the expression of AvBD-3 mRNA in the testicular tissue, but not in the ejaculated sperm. These results suggest that AvBD-3 is synthesized by late stage of spermatids in the testis, and this molecule is retained by the sperm during the passage of male reproductive tract, and even in the sperm storage tubules of oviduct. The sperm AvBD-3 is assumed to play roles in protecting the sperm from the microbial infection and enable to survive in the male and female reproductive tracts.