Riveiro Rodríguez, Antonio, Badar, Waqas, Ali, Husna ORCID: 0000-0003-3059-1262, Brooker, Olivia N., Newham, Elis, Snow, Tim, Terrill, Nicholas J. ORCID: 0000-0002-8783-1282, Tozzi, Gianluca, Fratzl, Peter, Knight, Martin M. and Gupta, Himadri S. ORCID: 0000-0003-2201-8933 (2022) Collagen pre-strain discontinuity at the bone—Cartilage interface. PLOS ONE, 17 (9). e0273832. ISSN 1932-6203 (doi:https://doi.org/10.1371/journal.pone.0273832)

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Abstract

The bone-cartilage unit (BCU) is a universal feature in diarthrodial joints, which is mechanically-graded and subjected to shear and compressive strains. Changes in the BCU have been linked to osteoarthritis (OA) progression. Here we report existence of a physiological internal strain gradient (pre-strain) across the BCU at the ultrastructural scale of the extracellular matrix (ECM) constituents, specifically the collagen fibril. We use X-ray scattering that probes changes in the axial periodicity of fibril-level D-stagger of tropocollagen molecules in the matrix fibrils, as a measure of microscopic pre-strain. We find that mineralized collagen nanofibrils in the calcified plate are in tensile pre-strain relative to the underlying trabecular bone. This behaviour contrasts with the previously accepted notion that fibrillar pre-strain (or D-stagger) in collagenous tissues always reduces with mineralization, via reduced hydration and associated swelling pressure. Within the calcified part of the BCU, a finer-scale gradient in pre-strain (0.6% increase over ~50μm) is observed. The increased fibrillar pre-strain is linked to prior research reporting large tissue-level residual strains under compression. The findings may have biomechanical adaptative significance: higher in-built molecular level resilience/damage resistance to physiological compression, and disruption of the molecular-level pre-strains during remodelling of the bone-cartilage interface may be potential factors in osteoarthritis-based degeneration.

Item Type:	Article
Uncontrolled Keywords:	Bone-cartilage interface, SAXS, strain
Subjects:	Q Science > Q Science (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Engineering (ENG)
Last Modified:	26 Oct 2022 12:29
URI:	http://gala.gre.ac.uk/id/eprint/37895

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