The Significance of Calcified Fibrocartilage on the Cortical Endplate of the Translational Sheep Spine Model

Abstract

To gain an understanding of the vertebral cortical endplate and factors that may affect the ability to achieve skeletal attachment to intervertebral implants and fusion, this study aimed to characterize the hypermineralized tissue on the cortical endplate of the vertebral body on a commonly used animal model. Skeletally mature sheep were injected with tetracycline prior to euthanasia and the C2-C3, T5-T6, and L2-L3 spinal motion segments were excised and prepared. Vertebral tissues were imaged using backscatter electron (BSE) imaging, histology, and tetracycline labeling was used to assess bone remodeling within different tissue layers. It was determined that the hypermineralized tissue layer was calcified fibrocartilage (CFC). No tetracycline labels were identified in the CFC layer, in contrast to single and double labels that were present in the underlying bone, indicating the CFC present on the cortical endplate was not being actively remodeled. The average thickness of the CFC layer was 146.3 6 70.53 mm in the cervical region, 98.2 6 40.29 mm in the thoracic region, and 150.89 6 69.25 mm in the lumbar region. This difference in thickness may be attributed to the regional biomechanical properties of the spine. Results from this investigation indicate the presence of a nonremodeling tissue on the cortical endplate of the vertebral body in sheep spines, which attaches the intervertebral disc to the vertebrae. This tissue, if not removed, would likely prevent successful bony attachment to an intervertebral device in spinal fusion studies and total disc replacement surgeries. Anat Rec,

Excessive Activation of TGFβ by Spinal Instability Causes Vertebral Endplate Sclerosis

“…Similar to the LSI model, the CSI model also demonstrated EP hypertrophy likely from abnormal bone remodeling in the osseous EP area. Although bone remodeling is coupled with angiogenesis and reduces the distance between circulating nutrients and IVD3031, the nutrient diffusion is actually impaired as a consequence of the replacement with cortical bone matrix32. The cortical bone matrix type I collagen in conjunction with loss of local type II collagen and change in spatial orientation contributes to EP sclerosis.…”

Multiphoton imaging and Raman spectroscopy of the bovine vertebral endplate

“…57 However, there is still some evidence of good connectivity between the two regions. 58,59 Our work contributes to the expanding knowledge of the endplate region through parallel imaging of mineralised and non-mineralised tissues allowing for clear identification of the three endplate regions of the bony endplate, mineralised and non-mineralised cartilage. Here we were not only able to study compositional and structural changes across the endplate zone, but also between the endplate of the annulus and nucleus.…”