Measuring ultrastructural biophysics of extracellular tissue matrices using high-brilliance synchrotron X-ray nanomechanical imaging

Himadri S. Gupta

Professor of Bioengineering and Biophysics

Institute of Bioengineering, Queen Mary University of London,

London E1 4NS

The extracellular matrix (ECM) of musculoskeletal tissues like cartilage, bone and skin is fundamental to physiological function, and alterations in its biophysics are implicated in loss of natural biomechanical function, e.g., in musculoskeletal degeneration like osteoarthritis or in scarring [1]. However, the ubiquitous hierarchical nature of the ECM – from the molecular to the macroscopic organ scale – leads to coupled multiscale deformations, where critical mechano-structural mechanisms, especially at the sub-micron length scales, are challenging to measure or model. Quantifying the small-scale biophysical environment of the ECM will enable development of novel structural biomarkers in musculoskeletal disease, microscale bioengineering in vitro platforms and understanding cell-matrix mechanobiological coupling. In this talk, I discuss how small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD), coupled with in situ micromechanical probes, high brilliance synchrotron X-ray sources and micro-focus optics, can reveal the biophysics of the ECM with high quantitative precision. I will review our work applying these methods to the molecular-level biophysics of diarthrodial joint ageing, bone fracture in osteoporosis and connective tissue fibrosis [2-9]. A unifying theme will be the ability to detect strain and mechanics of the collagen fibrillar network in the ECM, in a spatio-temporally resolved manner bridging the nanometre to micrometre scales. Examples will include synthetic ageing of bovine cartilage [2-4], development of fragility in glucocorticoid-induced osteoporosis [5-7], the complex ECM environment in fibrosis and keloid scarring [8] and the bone-cartilage interface [9]. Common mechanisms like graded nanoscale pre-strains [2], dynamic inter-molecular rearrangements in the ECM [3] and three-dimensional reorientation of fibre motifs [4] will be revealed as key processes underpinning the biomechanics of such tissues. I conclude by discussing promising future directions in applying these techniques to musculoskeletal and mechanobiological challenges, including extensions to tensor-tomography approaches for full-field 3D imaging and integration with multiscale modelling and correlative analysis.

References:

1. C. F. Guimares et al, Nature Rev Mater. (2020)
2. S. R. Inamdar et al Acta Biomater. (2019)
3. S. R. Inamdar et al ACS Nano (2017)
4. S. R. Inamdar et al Acta Biomater. (2021)
5. L. Xi et al, Bone (2020)
6. L. Xi et al Acta Biomater. (2018)
7. Karunaratne et al Bone (2016)
8. Y. Zhang et al, Materials (2022)
9. W. Badar et al, PLoS ONE (2022)