Indexed on: 04 May '17Published on: 04 May '17Published in: Journal of biomechanical engineering
Proteoglycans (PGs) have been reported to be broadly distributed within many soft tissues and, among other roles, often contribute to mechanical properties. Although PGs were once assumed to help support load in tendon, numerous studies have found no changes to tensile mechanics after PG depletion. Since PGs are known to help sustain non-tensile loading in other tissues (e.g., compressive forces in cartilage), we hypothesized that PGs might help support non-tensile loading in the human supraspinatus tendon (SST), a commonly injured tendon which functions in a complex multiaxial loading environment. Therefore, the objective of this study was to determine whether PGs contribute to the response of SST to shear loading, specifically in terms of multiscale mechanical properties and mechanisms of microscale matrix deformation. Results showed that ChABC treatment successfully digested PGs in SST samples while not disrupting collagen fibers. Peak and equilibrium shear stresses decreased only slightly after ChABC treatment and were not significantly different from pre-treatment values. Reduced stress ratios were computed and shown to be slightly greater after ChABC treatment compared to PBS incubation without enzyme, suggesting that these relatively small changes in stress values were not due strictly to tissue swelling. Microscale deformations were also not different after treatment. This study demonstrates that PGs possibly play a minor role in contributing to the mechanical behavior of tendon in shear, but are not a key tissue constituent to regulate shear mechanics.