<em>In vitro</em> method for 3D morphometry of human articular cartilage chondrons based on micro-computed tomography

Abstract

<div lang="en" class="abs"><p class="abs_header">Summary</p><p><em>Objective:</em> 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.</p><p><em>Method:</em> 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, <em>n</em> = 6; OARSI grades 3.0–3.5, <em>n</em> = 6).</p><p><em>Results:</em> 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 (<em>P</em> < 0.001) and less spherical (<em>P</em> < 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.</p><p><em>Conclusion:</em> 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).</p></div>