Distribution of proteins within different compartments of tendon varies according to tendon type.
Although the predominant function of all tendons is to transfer force from muscle to bone and position the limbs, some tendons additionally function as energy stores, reducing the energetic cost of locomotion. To maximise energy storage and return, energy-storing tendons need to be more extensible and elastic than tendons with a purely positional function. These properties are conferred in part by a specialisation of a specific compartment of the tendon, the interfascicular matrix, which enables sliding and recoil between adjacent fascicles. However, the composition of the interfascicular matrix is poorly characterised and we therefore tested the hypothesis that the distribution of elastin and proteoglycans differs between energy-storing and positional tendons, and that protein distribution varies between the fascicular matrix and the interfascicular matrix, with localisation of elastin and lubricin to the interfascicular matrix. Protein distribution in the energy-storing equine superficial digital flexor tendon and positional common digital extensor tendon was assessed using histology and immunohistochemistry. The results support the hypothesis, demonstrating enrichment of lubricin in the interfascicular matrix in both tendon types, where it is likely to facilitate interfascicular sliding. Elastin was also localised to the interfascicular matrix, specifically in the energy-storing superficial digital flexor tendon, which may account for the greater elasticity of the interfascicular matrix in this tendon. A differential distribution of proteoglycans was identified between tendon types and regions, which may indicate a distinct role for each of these proteins in tendon. These data provide important advances into fully characterising structure-function relationships within tendon.
Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK.
Chavaunne T
CT
Thorpe
Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK.
Kabelan J
KJ
Karunaseelan
Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK.
Jade
J
Ng Chieng Hin
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
Graham P
GP
Riley
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Helen L
HL
Birch
Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Neston, UK.
Peter D
PD
Clegg
Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London, UK.
Hazel R C
HR
Screen
D000818:Animals; D004549:Elastin; D006023:Glycoproteins; D006736:Horses; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D013710:Tendons / Q000378:metabolism*; D000099158:Proteoglycan 4
D004549:Elastin; D006023:Glycoproteins; D000099158:Proteoglycan 4
endotenon; histology; immunohistochemistry; interfascicular matrix; proteoglycans