<em>In vitro</em> method for 3D morphometry of human articular cartilage chondrons based on micro-computed tomography
Kestilä, I.; Thevenot, J.; Finnilä, M. A.; Karhula, S. S.; Hadjab, I.; Kauppinen, S.; Garon, M.; Quenneville, E.; Haapea, M.; Rieppo, L.; Pritzker, K. P.; Buschmann, M. D.; Nieminen, H. J.; Saarakkala, S.
Kestilä, I., Thevenot, J., Finnilä, M., Karhula, S., Hadjab, I., Kauppinen, S., Garon, M., Quenneville, E., Haapea, M., Rieppo, L., Pritzker, K., Buschmann, M., Nieminen, H., Saarakkala, S. (2018) In vitro method for 3D morphometry of human articular cartilage chondrons based on micro-computed tomography. Osteoarthritis and Cartilage, 26 (8), 1118-1126. doi:10.1016/j.joca.2018.05.012
© 2018 The Authors. Published by Elsevier Ltd on behalf of Osteoarthritis Research Society International. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Objective: The aims of this study were: to 1) develop a novel sample processing protocol to visualize human articular cartilage (AC) chondrons using micro-computed tomography (μCT), 2) develop and validate an algorithm to quantify the chondron morphology in 3D, and 3) compare the differences in chondron morphology between intact and osteoarthritic AC.
Method: The developed protocol is based on the dehydration of samples with hexamethyldisilazane (HMDS), followed by imaging with a desktop μCT. Chondron density and depth, as well as volume and sphericity, were calculated in 3D with a custom-made and validated algorithm employing semi-automatic chondron selection and segmentation. The quantitative parameters were analyzed at three AC depth zones (zone 1: 0–10%; zone 2: 10–40%; zone 3: 40–100%) and grouped by the OARSI histological grades (OARSI grades 0–1.0, n = 6; OARSI grades 3.0–3.5, n = 6).
Results: After semi-automatic chondron selection and segmentation, 1510 chondrons were approved for 3D morphometric analyses. The chondrons especially in the deeper tissue (zones 2 and 3) were significantly larger (P < 0.001) and less spherical (P < 0.001), respectively, in the OARSI grade 3–3.5 group compared to the OARSI grade 0–1.0 group. No statistically significant difference in chondron density between the OARSI grade groups was observed at different depths.
Conclusion: We have developed a novel sample processing protocol for chondron imaging in 3D, as well as a high-throughput algorithm to semi-automatically quantify chondron/chondrocyte 3D morphology in AC. Our results also suggest that 3D chondron morphology is affected by the progression of osteoarthritis (OA).
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