ALB, GPX5 and PTGDS as potential biomarkers for the aging processes of the dog epididymis.

Alterations in the reproductive tract related to aging processes are reflected by changes in biochemical components such as proteins. This study aimed (1) to investigate changes in canine epididymal fluid protein abundance in relation to age, and (2) to select potential protein markers of canine reproductive tract aging. Twenty-three mixed-breed dogs were used in the study. The dogs were divided into the following three experimental groups: ExG1 (1-3 years old); ExG2 (3.5-6 years old); and ExG3 (6.5-11 years old). Cauda epididymal fluid was collected from dissected tissues and centrifuged to separate the epididymal fluid from the epididymal sperm. Chromatography coupled with mass spectrometry (nanoUPLC-Q-TOF/MS) was used to analyze the proteins in the epididymal fluid. The proteomic profiling uncovered 121, 122, and 56 unique proteins in ExG1, ExG2, and ExG3 respectively, with 48 proteins being common across all groups. Gene ontology analysis showed similar main molecular functions for all three ExGs; however, the percentage of particular proteins in each ExG differed. There were three proteins that showed significant (P < 0.05) changes in relative abundance among the ExGs, including albumin (ALB), epididymal secretory glutathione peroxidase (GPX5), and prostaglandin-H2 D-isomerase (PTGDS). The findings suggest that aging in dogs may influence epididymal fluid protein composition, particularly affecting ALB, GPX5, and PTGDS, which could play roles in oxidative and ion metabolic regulation. These findings suggest that ALB, GPX5, and PTGDS may serve as biomarkers for epididymal aging. Their detection could enhance the evaluation of epididymal semen quality, aiding reproductive medicine practices in dogs of different ages.