Towards a Complete Intervertebral Disc: Modulation of the Biochemical and Mechanical Properties of in vitro formed Nucleus Pulposus Tissue

This study aims to improve understanding of the intervertebral disc (IVD) as a complete unit. The influence of circumferential constraint provided by the annulus fibrosus is examined. Cultured bovine nucleus pulposus (NP) cells are allowed to form tissue and subjected to different degrees of circumferential constraint. As constraint increases NP cells increase gene expression of degradative molecules and decrease gene expression of matrix molecules. This leads to significantly decreased accumulation of extracellular matrix and inferior mechanical properties. Constraining NP tissue may be used as a model for IVD degeneration.

Creation of a novel triphasic structure consisting of calcium polyphosphate (bone substitute), cartilage, and NP tissue emulates in vivo structure by inclusion of a cartilage end plate. The structure is more adherent than NP tissue alone as demonstrated by improved tissue attachment.

Development of in vitro IVD models will lead to better understanding and treatments for disc degeneration.