INTRODUCTION: Degeneration of the intervertebral disc (IVD) and endplate structures is linked to many pathological processes in the spine. Various animal models of IVD and endplate degeneration have been used to study the etiology and treatments of spinal disorders. Translation of animal research elucidating mechanisms of spinal injury and repair requires a characterization of the vertebral endplate in multiple species. In this study, we compared the endplate structure of laboratory animal species at the age range commonly used for modeling spine degeneration with that of an adult human.
METHODS: IVDs and the adjacent vertebral bodies were isolated from the lumbar spine of the adult mouse, rat, rabbit, goat and human donor (Gift of Hope). Segments were fixed in formaldehyde and decalcified. Tissues were then imbedded, sectioned and stained with Alcian Blue with Haematoxylin and Eosin (H&E) counter stain, and photographed.
RESULTS: Structure of the vertebral endplate varied significantly between adult species. All animal model species had at least two distinct layers: the cartilaginous endplate and the growth plate. In the rabbit and goat spine segments, an additional thin bony layer was found between the cartilaginous end plate and the growth plate; while the bony layer was not evident in the mouse and rat spine segments. The human endplate consisted of a cartilaginous layer between endplate and bone of the vertebral body, and had a more robust bony transition to cancellous bone. Unlike the animal model species, the growth plate in the adult human was absent.
DISCUSSION: Significant differences exist in histological features of the endplate across species. Adult rodents, rabbit and goat have endplates that are different from adult humans. Since IVDs depend on nutrients and oxygen to diffuse through the endplates, consideration should be given when animal models are used to study intervertebral disc degeneration and surgical treatments.