Supraspinatus tendon overuse results in degenerative changes to tendon insertion region and adjacent humeral cartilage in a rat model

• Type of Material: Article
• Authors: Akia N. Parks, Georgia Institute of Technology; Jennifer McFaline-Figueroa, Georgia Institute of Technology; Anne Coogan, Georgia Institute of Technology; Emma Poe-Yamagata, Georgia Institute of Technology; Robert E. Guldberg, Emory University; Manu Omar Platt, Emory University; Johnna Sue Temenoff, Emory University
• Language: English
• Date: 2017-09-01
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1002/jor.23496
• Title of Journal or Parent Work: Journal of Orthopaedic Research
• ISSN: 0736-0266
• Volume: 35
• Issue: 9
• Start Page: 1910
• End Page: 1918
• Grant/Funding Information: Grant sponsor: National Institute of Arthritis and Musculoskeletal; Grant sponsor: Skin Diseases of the National Institutes of Health; Grant number: R01AR063692; Grant sponsor: National Institutes of Health Cell and Tissue Engineering Training; Grant number: T32GM008433.
• Keywords: supraspinatus tendon; Life Sciences & Biomedicine; TENDINOPATHY; HUMAN OSTEOARTHRITIC CARTILAGE; ROTATOR CUFF TEAR; Orthopedics; zymography; cartilage; CATHEPSIN-K; micro-computed tomography; ANIMAL-MODELS; Science & Technology; EXPRESSION; V ACTIVITY; GLENOID CARTILAGE; MATRIX METALLOPROTEINASES; CYSTEINE CATHEPSINS; overuse injury
• Research Categories: Engineering, Mechanical; Engineering, Biomedical

Abstract

The etiology of rotator cuff tendon overuse injuries is still not well understood. Furthermore, how this overuse injury impacts other components of the glenohumeral joint, including nearby articular cartilage, is also unclear. Therefore, this study sought to better understand the time course of tendon protease activity in a rat model of supraspinatus overuse, as well as determine effects of 10 weeks of overuse on humeral head articular cartilage. For these studies, multiplex gelatin zymography was used to characterize protease activity profiles in tendon and cartilage, while histological scoring/mechanical testing and micro-computed tomography (μCT) imaging were used to quantify structural damage in the supraspinatus tendon insertion and humeral articular cartilage, respectively. Histological scoring of supraspinatus tendon insertions revealed tendinopathic cellular and collagen fiber changes after 10 weeks of overuse when compared to controls, while mechanical testing revealed no significant differences between tensile moduli (overuse: 24.5 ± 11.5 MPa; control: 16.3 ± 8.7 MPa). EPIC-μCT imaging on humeral articular cartilage demonstrated significant cartilage thinning (overuse: 119.6 ± 6.34 μm; control: 195.4 ± 13.4μm), decreased proteoglycan content (overuse: 2.1 ± 0.18 cm−1; control: 1.65 ± 0.14 cm−1), and increased subchondral bone thickness (overuse: 216.2 ± 10.9 μm; control: 192 ± 17.8μm) in the overuse animals. Zymography results showed no significant upregulation of cathepsins or matrix metalloproteinases in tendon or cartilage at 2 or 10 weeks of overuse compared to controls. These results have further elucidated timing of protease activity over 10 weeks and suggest that damage occurs to other tissues in addition to the supraspinatus tendon in this overuse injury model.