The organisation of elastin and fibrillins 1 and 2 in the cruciate ligament complex

Authors

  • Kinley D. Smith,

    1. Department of Musculoskeletal Biology, Institute of Aging and Chronic disease and School of Veterinary Science, Leahurst Campus, University of Liverpool, Liverpool, UK
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  • Anne Vaughan-Thomas,

    1. Department of Musculoskeletal Biology, Institute of Aging and Chronic disease and School of Veterinary Science, Leahurst Campus, University of Liverpool, Liverpool, UK
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    • Dr Vaughan-Thomas is deceased.

  • David G. Spiller,

    1. Centre for Cell Imaging, University of Liverpool, Liverpool, UK
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  • John F. Innes,

    1. Department of Musculoskeletal Biology, Institute of Aging and Chronic disease and School of Veterinary Science, Leahurst Campus, University of Liverpool, Liverpool, UK
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  • Peter D. Clegg,

    1. Department of Musculoskeletal Biology, Institute of Aging and Chronic disease and School of Veterinary Science, Leahurst Campus, University of Liverpool, Liverpool, UK
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  • Eithne J. Comerford

    1. Department of Musculoskeletal Biology, Institute of Aging and Chronic disease and School of Veterinary Science, Leahurst Campus, University of Liverpool, Liverpool, UK
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Kinley D. Smith, Small Animal Hospital, Faculty of Veterinary Medicine, University of Glasgow, 464 Bearsden Road, Glasgow G61 1QH, UK. T: +44 (0) 141 330 5848; F: +44 (0) 141 330 3663; E:k.smith@vet.gla.ac.uk

Abstract

Although elastin fibres and oxytalan fibres (bundles of microfibrils) have important mechanical, biochemical and cell regulatory functions, neither their distribution nor their function in cruciate ligaments has been investigated. Twelve pairs of cruciate ligaments (CLs) were obtained from 10 adult dogs with no evidence of knee osteoarthritis. Elastic fibres were identified using Verhoeff’s and Miller’s staining. Fibrillins 1 and 2 were immunolocalised and imaged using confocal laser scanning microscopy. Hydrated, unfixed tissue was analysed using Nomarski differential interference microscopy (NDIC), allowing structural and mechanical analysis. Microfibrils and elastin fibres were widespread in both CLs, predominantly within ligament fascicles, parallel to collagen bundles. Although elastin fibres were sparse, microfibrils were abundant. We described abundant fibres composed of both fibrillin 1 and fibrillin 2, which had a similar pattern of distribution to oxytalan fibres. NDIC demonstrated complex interfascicular and interbundle anatomy in the CL complex. The distribution of elastin fibres is suggestive of a mechanical role in bundle reorganisation following ligament deformation. The presence and location of fibrillin 2 in oxytalan fibres in ligament differs from the solely fibrillin 1-containing oxytalan fibres previously described in tendon and may demonstrate a fundamental difference between ligament and tendon.

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