Age-related Changes in the Prostate and Testes of the Beagle Dog

Abstract

Age-related changes in the histologic morphology of the Beagle dog prostate have been used as a model for similar changes that occur in human beings. Previous studies of the aging changes in Beagle dogs have been limited to animals less than 10 years of age. In this study, the prostate, testes, and serum testosterone levels were evaluated in healthy Beagle dogs that were grouped by age to provide five groups of dogs that ranged from 3 to 14 years of age. Tissue sections from the prostate and testes were examined qualitatively and quantitatively by light microscopy. All animals 6 years of age and older had histologic characteristics of complex benign prostatic hyperplasia. A mean statistically significant increase in prostatic weight with increased age was noted (mean value 1.08 ± 0.22 g/kg body weight at 3 years of age, increasing to 2.64 ± 0.37 g/kg body weight at 14 years of age). Morphometric analysis of the prostatic tissue suggested that similar to the change observed in human males, the increase in size was primarily due to an increase in the absolute volume of interstitial tissues (mean value 2.8 ± 1.1 cm3 at 3 years of age, increasing to 7.4 ± 1.3 cm3 at 14 years of age). The epithelial component did not contribute to the increase noted, with the exception that the percentage of glandular lumen did increase with age, indicating progressive cystic dilatation of the glands. Stereologic analysis of the testes showed a decrease in the relative percentage of germ cells with increasing age (mean value 58.5 ± 2.3% at 3 years of age, decreasing to 45.2 ± 4.0% at 14 years of age). No distinct age-related trend was detected in serum testosterone concentrations. These findings indicate that the progression of benign prostatic hyperplasia occurs throughout the entire life span of the dog; an association with changes in the testes was not identified.