[Retinoic acid-induced hyperostosis in the murine spine, particularly in the cervical spine]

In order to investigate the role of retinoic acid in inducing spinal hyperostosis, the murine spine was radiologically and histologically examined after a 24-week peroral administration of synthetic retinoic acid (etretinate). In the cervical spine, osteophytes on the ventral rims of the vertebral bodies were more developed after etretinate administration than in controls. Histologically, chondrocytes after etretinate administration proliferated in the anterior longitudinal ligaments at the junction of the ventro-caudal rim and the epiphyseal region of the C2 and C3 vertebral bodies. Endochondral ossification was a characteristic feature and immature chondrocytes and mesenchymal cells were found in the region. After etretinate administration, the incidence of proliferative changes was 67.6% at the C2 ventro-caudal rim, and 79.4% and 70.6%, respectively in the C2 and C3 ventral epiphyseal regions. These percentages were highly significant compared with controls, but they were not dosage-dependent. These findings suggested that retinoic acid was involved in the differentiation and proliferation of chondrocytes in ligaments.