Influence of Decorin on the Mechanical, Compositional, and Structural Properties of the Mouse Patellar Tendon

Abstract

The interactions of small leucine-rich proteoglycans (SLRPs) with collagen fibrils, their association with water, and their role in fibrillogenesis suggests that SLRPs may play an important role in tendon mechanics. Some studies have assessed the role of SLRPs in the mechanical response of the tendon, but the relationships between sophisticated mechanics, assembly of collagen, and SLRPs have not been well characterized. Decorin content was varied in a dose dependent manner using decorin null, decorin heterozygote, and wild type mice. Quantitative measures of mechanical (tension and compression), compositional, and structural changes of the mouse patellar tendon were evaluated. Viscoelastic, tensile dynamic modulus was increased in the decorin heterozygous tendons compared to wild type. These tendons also had a significant decrease in total collagen and no structural changes compared to wild type. Decorin null tendons did not have any mechanical changes; however, a significant decrease in the average fibril diameter was found. No differences were seen between genotypes in elastic or compressive properties, and all tendons demonstrated viscoelastic mechanical dependence on strain rate and frequency. These results suggest that decorin, a member of the SLRP family, plays a role in tendon viscoelasticity that cannot be completely explained by its role in collagen fibrillogenesis. In addition, reductions in decorin do not cause large changes in indentation compressive properties, suggesting that other factors contribute to these properties. Understanding these relationships may ultimately help guide development of tissue engineered constructs or treatment modalities.

Effect of Age and Proteoglycan Deficiency on Collagen Fiber Re-Alignment and Mechanical Properties in Mouse Supraspinatus Tendon

“…Although changes in the mechanical properties with theremoval of the PGs and glycosaminoglycans have been debated [10][11][12][13], this study shows that decorin and biglycan contribute to tendon's response to load. While there were minimal differences between genotypes at each age (supporting previous studies negating the role of PGs and GAGs in tendon mechanics), there were changes with the effect of aging on those properties and changes in the realignment of collagen fibers.…”

“…While some in vitro work has shown that the addition of decorin, a major PG in tendon, improves the mechanical properties of self-assembled collagen fibrils [9], studies with enzymatic removal of GAGs in tendon and ligament have not provided conclusive evidence to support this mechanism [10][11][12]. Recently, the contribution of PGs to tendon mechanical properties has been closely studied, due to the ability to create transgenic mouse strains lacking the major proteoglycans in tendon, decorin, and biglycan [13]. Since PGs are known to play a role in the regulation of fibril structure during development [14,15], one might hypothesize that they may also affect the structure of tendon and, thus, the mechanical properties, throughout the aging process.…”

Collagen V-heterozygous and -null supraspinatus tendons exhibit altered dynamic mechanical behaviour at multiple hierarchical scales

“…Twenty specimens from each group designated for dynamic viscoelastic testing were subjected to a testing protocol as described previously [13,14,40]. Tendons were first preloaded and preconditioned for 10 cycles to 1.5% grip strain at 0.25 Hz.…”

“…In addition, the dynamic modulus jE*j (defined as the stress amplitude divided by the strain amplitude) and the phase angle d (between the stress and strain) were computed at each frequency and strain level. The dynamic modulus (jE*j) represents how difficult the material is to deform under dynamic loading, while the tangent of the phase angle (tan d) is the ratio of loss over storage moduli [13,14,40,42]. Comparisons were made using one-way ANOVA for each parameter with post-hoc Bonferroni tests to correct for family-wise error associated with multiple comparisons.…”

New insight of some extracellular matrix molecules in beef muscles. Relationships with sensory qualities

“…Their addition to collagen gels increases compressive resistance of these gels (Nishiyama et al, 1994;Margaron et al, 2010). Decorin could also play a role in mechanical properties of tissues, however, its role has not been elucidated (Lewis et al, 2010;Dourte et al, 2012). Our study shows a high muscle effect on the decorin ratio to collagen or PGs and tenascin-X to PGs.…”