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Objective evaluation of chondrocyte density & cloning after joint injury using convolutional neural networks
Journal article   Open access   Peer reviewed

Objective evaluation of chondrocyte density & cloning after joint injury using convolutional neural networks

Linjun Yang, James A. Martin, Marc J. Brouillette, Joseph A. Buckwalter and Jessica E. Goetz
Journal of orthopaedic research, Vol.40(11), pp.2609-2619
02/16/2022
DOI: 10.1002/jor.25295
PMCID: PMC9378771
PMID: 35171527
url
https://doi.org/10.1002/jor.25295View
Published (Version of record)CC BY-NC-ND V4.0 Open Access

Abstract

Variations in chondrocyte density and organization in cartilage histology sections are associated with osteoarthritis progression. Rapid, accurate quantification of these two features can facilitate the evaluation of cartilage health and advance the understanding of their significance. The goal of this work was to adapt deep-learning-based methods to detect articular chondrocytes and chondrocyte clones from safranin-O-stained cartilage to evaluate chondrocyte cellularity and organization. The U-net and "you-only-look-once" (YOLO) models were trained and validated for identifying chondrocytes and chondrocyte clones, respectively. Validated models were then used to quantify chondrocyte and done density in talar cartilage from Yucatan minipigs sacrificed 1 week, 3, 6, and 12 months after fixation of an intraarticular fracture of the hock joint. There was excellent/good agreement between expert researchers and the developed models in identifying chondrocytes/clones (U-net: R-2 = 0.93, y = 0.90x-0.69; median F1 score: 0.87/YOLO: R-2 = 0.79, y = 0.95x; median F1 score: 0.67). Average chondrocyte density increased 1 week after fracture (from 774 to 856 cells/mm(2)), decreased substantially 3 months after fracture (610 cells/mm(2)), and slowly increased 6 and 12 months after fracture (638 and 683 cells/mm(2) , respectively). Average detected clone density 3, 6, and 12 months after fracture (11, 11, 9 clones/mm(2)) was higher than the 4-5 clones/mm(2) detected in normal tissue or 1 week after fracture and show local increases in clone density that varied across the joint surface with time. The accurate evaluation of cartilage cellularity and organization provided by this deep learning approach will increase objectivity of cartilage injury and regeneration assessments.
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