Expression of peroxiredoxin-6 in the epididymal microenvironment and sperm of sheep

Sperm complete their maturation in the epididymis. Mature sperm are highly sensitive to oxidative damage. Peroxiredoxin-6 (PRDX6) is an important antioxidant enzyme. In this study, we investigated PRDX6 expression in the epididymal microenvironment and its distribution in the sperm of sheep. We found that PRDX6 mRNA and protein had the highest expression in the caput epididymis, followed by the corpus epididymis and cauda epididymis ( $p<0.01$ ). PRDX6 protein expression in epididymal fluid was higher in the caput epididymis than in the corpus epididymis and cauda epididymis ( $p<0.01$ ). Similarly, PRDX6 protein expression was higher in sperm derived from the caput epididymis and corpus epididymis than in sperm derived from the cauda epididymis ( $p<0.01$ ). Immunofluorescence revealed that PRDX6 was present only in the head of sperm derived from the caput epididymis and corpus epididymis but was distributed within the principal and middle regions of sperm derived from the cauda epididymis. Furthermore, PRDX6 was present in all parts of ejaculated sperm. In conclusion, PRDX6 showed a wider distribution in sperm cells during transport through the epididymis, and PRDX6 expression levels in epididymal tissue, epididymal fluid, and epididymal sperm decreased from the caput epididymis to the cauda epididymis. These results suggest that PRDX6 has an important role during sperm maturation in the epididymis.