Chondroitin sulphate glycosaminoglycans contribute to widespread inferior biomechanics in tendon after focal injury.
Both mechanical and structural properties of tendon change after injury however the causal relationship between these properties is presently unclear. This study aimed to determine the extent of biomechanical change in post-injury tendon pathology and whether the sulphated glycosaminoglycans (glycosaminoglycans) present are a causal factor in these changes. Equine superficial digital flexor tendons (SDF tendons) were surgically-injured in vivo (n=6 injured, n=6 control). Six weeks later they were harvested and regionally dissected into twelve regions around the lesion (equal medial/lateral, proximal/distal). Glycosaminoglycans were removed by enzymatic (chondroitinase) treatment. Elastic modulus (modulus) and ultimate tensile strength (UTS) were measured under uniaxial tension to failure, and tendon glycosaminoglycan content was measured by spectrophotometry. Compared to healthy tendons, pathology induced by the injury decreased modulus (-38%; 95%CI -49% to -28%; P<0.001) and UTS (-38%; 95%CI -48% to -28%; P<0.001) and increased glycosaminoglycan content (+52%; 95%CI 39% - 64%; P<0.001) throughout the tendon. Chondroitinase-mediated glycosaminoglycan removal (50%; 95%CI 21-79%; P<0.001) in surgically-injured pathological tendons caused a significant increase in modulus (5.6MPa/µg removed; 95%CI 0.31-11; P=0.038) and UTS (1.0MPa per µg removed; 95%CI 0.043-2; P=0.041). These results demonstrate that the chondroitin/dermatan sulphate glycosaminoglycans that accumulate in pathological tendon post-injury are partly responsible for the altered biomechanical properties.
Murray Maxwell Biomechanics Laboratory (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia; Raymond Purves Bone and Joint Research Laboratories (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia.
Rachel K
RK
Choi
Raymond Purves Bone and Joint Research Laboratories (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia.
Margaret M
MM
Smith
Murray Maxwell Biomechanics Laboratory (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia.
Joshua H
JH
Martin
Faculty of Health Sciences, University of Sydney, Lidcombe, New South Wales, Australia.
Jillian L
JL
Clarke
Research and Clinical Training Unit, University Veterinary Teaching Hospital, University of Sydney, Camden, New South Wales, Australia.
Andrew J
AJ
Dart
Raymond Purves Bone and Joint Research Laboratories (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia. Electronic address: christopher.little@sydney.edu.au.
Christopher B
CB
Little
Murray Maxwell Biomechanics Laboratory (Institute of Bone and Joint Research), Kolling Institute, Royal North Shore Hospital (Sydney Medical School, University of Sydney), St Leonards, New South Wales, Australia.
Elizabeth C
EC
Clarke
D000818:Animals; D001696:Biomechanical Phenomena; D002809:Chondroitin Sulfates / Q000378:metabolism*; D055119:Elastic Modulus; D006734:Horse Diseases / Q000378:metabolism* / Q000473:pathology; D006736:Horses; D006801:Humans; D008297:Male; D034561:Sheep, Domestic; D013708:Tendon Injuries / Q000378:metabolism* / Q000473:pathology; D013710:Tendons / Q000378:metabolism* / Q000473:pathology
C038142:chondroitin sulfate glycosaminoglycan; D002809:Chondroitin Sulfates
Biomechanics; Chondroitinase; Glycosaminoglycan; Tendinopathy; Tendon