The influence of decorin, a potential pro-inflammatory stimulant, on the mechanical properties of the annulus fibrosus.

Abstract

Purpose: Structural disruption of the intervertebral disc can result in fragmentation of extracellular matrix components such as decorin, which has the capacity to mount an inflammatory response. However, it is unknown if decorin also alters the biomechanical properties of the intervertebral disc, and specifically the annulus fibrosus. Therefore, the purpose of this study was to investigate the potential of decorin to stimulate a pro-inflammatory environment and alter the mechanical integrity and tensile properties of a rat tail annulus.

Methods: Sixty annulus fibrosus rings were dissected from 15 rat tails and randomized into three culture conditions: (i) control; (ii) 0.5 µg/mL bovine decorin (low dose); (iii) 5 µg/mL bovine decorin (high dose). Samples were cultured for 6 days then tested via a tensile mechanical testing system. IL-6 and MIP-2 concentration in the culture media were quantified via enzyme-linked immunosorbent assays at day 6.

Results: IL-6 and MIP-2 were present in the media after six days of culture but did not differ between conditions. Decorin did, however, impact a number of tensile properties of the annulus. Specifically, the high dose of decorin resulted in greater toe region strain (p < 0.001) and greater failure strain (p < 0.001) as well as greater initial failure stress (p = 0.024) and maximum stress (p = 0.001).

Discussion: The observed increase in annulus strength may be a result of reorganization of the load-bearing collagen fibres while the increased strain may be due to degradation of other matrix proteins. Future work is necessary to further elucidate the complex relationship between decorin exposure and altered tissue mechanics.