Plenary Poster ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Uncovering dynamic changes in mineralised tissues with osteoarthritis using synchrotron-radiation micro-computed tomography (#303)

Pholpat Durongbhan 1 , Han Liu 1 , Zixuan C. Zhao 1 , Kathryn S. Stok 1
  1. Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia

Introduction: Calcified cartilage is a thin, mineralised tissue anchoring articular cartilage to subchondral bone, separating their respective biochemical environments while allowing force transmission and nutrient diffusion1. Calcified cartilage is dramatically altered during osteoarthritis (OA) progression, making it one of the hallmark features of the disease. However, imaging calcified cartilage for structural assessment, particularly in animal models like mice (10-30μm), remains challenging due to the resolution and polychromatic light of imaging systems. This study aims to leverage high-resolution, monochromatic beams of synchrotron-radiation micro-computed tomography (SR-microCT) to investigate structural changes in calcified cartilage and its surrounding mineralised tissues in a mouse model of spontaneous knee OA at different disease stages.

Methods: Tibiae from STR/ort (OA, n=56) and CBA/1 (Control, n=60) mice from a previous study were used2. Each sample was soaked in contrast agent solution (HexabrixTM), placed in a custom-built humidity chamber3, and imaged using SR-microCT (X02DA TOMCAT, Switzerland4) with 10x magnification and 3 μm isotropic voxel size. Tibiae were segmented, and trabecular regions were separated using our previously developed algorithm5. The remaining cortical (higher mineralisation) and calcified cartilage (lower mineralisation) regions were separated using a dual-threshold approach. Three-dimensional quantitative morphometric analysis of these tissues was performed to extract structural information.

Results: A representative SR-microCT image (Fig.1a) shows a distinct calcified cartilage layer with clear microstructural features. The described image processing workflow enables the segmentation of trabecular bone, cortical bone, and calcified cartilage (Fig.1b-c), leading to exemplar quantitative results (Fig.1d). Data from different disease stages will be presented to uncover structural changes in these mineralised tissues during OA progression.

Conclusion: Quantifying structural changes of calcified cartilage and bone during OA progression using SR-microCT can shed light on their complex remodelling processes. Future work will explore links between relative structural changes between calcified cartilage and mature subchondral bone at various OA stages.

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  1. Oliveira Silva, M., Gregory, J. L., Ansari, N. & Stok, K. S. Molecular Signaling Interactions and Transport at the Osteochondral Interface: A Review. Front. Cell Dev. Biol. 8, 750 (2020).
  2. Stok, K. S. et al. Revealing the interplay of bone and cartilage in osteoarthritis through multimodal imaging of murine joints. Bone 45, 414–422 (2009).
  3. Choo, R. J., Firminger, C., Müller, R. & Stok, K. S. Prevention of cartilage dehydration in imaging studies with a customized humidity chamber. Rev. Sci. Instrum. 84, (2013).
  4. Stampanoni, M. et al. Trends in synchrotron-based tomographic imaging: the SLS experience. in Developments in X-Ray Tomography V vol. 6318 (2006).
  5. Besler, B. A., Sondergaard, R. E., Müller, R. & Stok, K. S. Reproducibility of compartmental subchondral bone morphometry in the mouse tibiofemoral joint. Bone 81, 649–653 (2015).