Persistence of vertebral growth plate cartilage in aged cynomolgus monkeys

Growth plates at each end of vertebral bodies play a pivotal role in longitudinal spinal growth. Epiphyseal closures are formed in adult humans. Although monkeys are frequently employed in bone and disc research, the age of epiphyseal closure has not been well documented. In this study, histological analyses of lumbar vertebral end plates and the surrounding tissue were performed in 11 normal cynomolgus monkeys aged approximately 9 to 15 years, and unclosed growth plate cartilage was detected in all the end plates. The data from this study constitute the first documentation of persistent vertebral growth plate cartilage in cynomolgus monkeys. The persistence of growth plate cartilage in cynomolgus monkeys approximately 15 years of age or younger, which differs from the complete epiphyseal closure exhibited in adult humans, may affect the biomechanical behavior of the spine. This is an important factor to consider in extrapolating the results of spine and intervertebral disc research using cynomolgus monkeys to adult humans.