Document Type

Thesis

Degree Name

Master of Kinesiology (MKin)

Department

Kinesiology and Physical Education

Faculty/School

Faculty of Science

First Advisor

Dr. Diane Gregory

Advisor Role

Supervisor

Abstract

Previous literature has investigated the biomechanical properties of various animal models, but few have studied an isolated and intact rat tail annulus fibrosus. Decorin, a class 1 small leucine-rich protein (SLRP) has the potential to trigger an inflammatory environment as previous research has shown that it may stimulate inflammation via the toll-like receptor (TLR) pathway. An increased inflammatory environment can have biomechanical implications for the disc, and so the ability of decorin to stimulate an environment that alters the mechanical properties of the disc was investigated.

The purpose of this study was to investigate the potential of decorin, a proteoglycan native to the intervertebral disc, to stimulate a pro-inflammatory environment and alter the mechanical integrity and tensile properties of a rat tail annulus fibrosus.

Sixty whole annulus fibrosus samples were dissected from 15 rat tails. The samples were randomized into three culture conditions: i) control – standard media (n=20); ii) low dose – 0.5µg/mL standard+decorin (n=20); iii) high dose – 5µg/mL standard+decorin (n=20). All samples were cultured in an incubator for 6 days and then mechanically tested via a tensile mechanical testing system (BioTester, Cellscale, Waterloo, ON.). Various tensile mechanical properties were analyzed including, tissue stiffness, stress (MPa) and strain (%) at the end of the toe region, at initial failure, and at ultimate tensile strength.

No significant findings for disc mechanics were observed in this study. Although a visible and reoccurring trend of increasing strength was seen in response to increasing decorin concentration, contrary to what was hypothesized. ELISA (enzyme-linked immunosorbent assay) kits were used to determine the concentration of three proinflammatory cytokines (IL-6, MCP-1, MIP-2) in culture media collected at day 6. The main effect of MIP-2 concentration was found to be significantly greater for the control condition compared to the high dose condition (p=0.009), contrary to what was expected.

Decorin did not significantly alter disc mechanics in an isolated and free-floating rat tail annulus fibrosus, however, a consistent trend of increased strength with increased decorin concentration was seen. Although there are many possible reasons for the lack of significant findings with respect to mechanics, one possible reason is that decorin did not create the inflammatory environment that was expected. In fact, based on the finding of MIP-2 concentration, decorin conditions may have even been less inflammatory. It is possible that annular cell death (loss of cell viability) occurred, either due to the long incubation period, or concentrations of decorin utilized, although this was not confirmed. Future work is necessary to investigate the relationship between decorin concentration and mechanical properties, however, a shorter incubation period is suggested.

Convocation Year

2023

Convocation Season

Spring

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Available for download on Monday, September 29, 2025

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