The Establishment of Intervertebral Endplate Degeneration: A Novel in-vivo Diurnal-Axial Controllable Loading Model in Rat Tail

Abstract

Background. Cartilage endplate (CEP) acts as an important mechanical barrier and nutrient channel for the intervertebral disc (IVD). Its vulnerability to excessive loading and subsequent degeneration might be an initial trigger for IVD degeneration. This study aims to build a new in-vivo animal model of rat-tail CEP degeneration through implementing a controllable axial compressive device.Methods. An axial controllable compressive load was conducted on the 8–9 th coccygeal IVD of adult rat tail through puncturing 4 Kirschner wires into its superior and inferior vertebra. The exact compression loads were controlled and adjusted by a remote controller. The compression and decompression periods were set as 8 h/16 h per day. The control group was set as no device installation, while the Kirschner wires were punctured without compression in the sham group. After each 4, 8 and 12 weeks, 3 rats in each group were sacrificed and compressed disc were analyzed.Results. After compression, the targeted CEP degenerated gradually with time. Through 12 weeks' loading, the CEP structure collapsed completely and the Schmorl's nodes formed and penetrated from the cartilage layer into the vertebra. When compared with the control group, the number of micro porosities in the CEP becomes extremely scarce with loading, while the content of aggrecan and collagen II decreased significantly. However, these significant changes did not show up when sham and control groups were compared.Conclusions. A new excessive force induced CEP degeneration animal model was developed with its contribution as a practical alternative for further studying mechanisms of CEP degeneration.