Large animal models of disc degeneration

Abstract

Intervertebral discs are largely of embryonic notochordal origin and impart a unique biomechanical function to the spine of vertebrate animals (Singh et al. 2005). The intervertebral disc is anatomically comprised of two constituents: a proteoglycan-rich nucleus pulposus contained within a collagen 1-rich annulus fibrosus (Singh et al. 2005). Together, these structures effectively dissipate mechanical loads within the spine while allowing controlled motion between adjacent vertebrae. The biologic environment of the disc is uniquely harsh due to the avascular nature of the tissue and the long distance between metabolically active cells and their nutritional source. Tissue degeneration progresses through a well-defined series of changes (Singh et al. 2005) including breakdown of the long-chain proteoglycan constituents of the extracellular matrix, loss of water-binding capacity, decreased cellularity, and annular disorganization/disruption (Lotz 2004).