TISSUES FORMED DURING DISTRACTION OSTEOGENESIS IN THE RABBIT ARE DETERMINED BY THE DISTRACTION RATE: LOCALIZATION OF THE CELLS THAT EXPRESS THE mRNAs AND THE DISTRIBUTION OF TYPES I AND II COLLAGENS

Authors

  • G. Li,

    1. Nuffield Department of Orthopaedic Surgery, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, U.K.
    2. Bone Research Laboratory, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, U.K.
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    • Present address: Orthopaedic Research Unit, Musgrave Park Hospital, Belfast, BT9 7JB, U.K.

  • A. S. Virdi,

    1. Bone Research Laboratory, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, U.K.
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    • Present address: Department of Anatomy, Rush-Presbyterian-St. Luke's Medical Center, Rush University, Chicago, IL60612-3832, U.S.A.

  • Doreen E. Ashhurst,

    Corresponding author
    1. Department of Anatomy, St. George's Hospital Medical School, London, SW17 0RE, U.K.
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  • A.H.R.W. Simpson,

    1. Nuffield Department of Orthopaedic Surgery, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, U.K.
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  • J. T. Triffitt

    1. Bone Research Laboratory, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, U.K.
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To whom correspondence should be addressed. Dr D. E. Ashhurst, Department of Anatomy, St George's Hospital Medical School, Tooting, London SW17 0RE, U.K. Tel: 0181 725 5224; Fax: 0181 725 3326. E-mail:d.ashhurst@sghms.ac.uk

Abstract

An experimental model of leg lengthening was used to study the morphology of, the collagenous proteins present, and the collagen genes expressed in the regenerating tissue following 20% lengthening at four different distraction rates. At a distraction rate of 0.3mm/day (8 weeks distraction), the regenerate consists of intramembranous bone and localized areas of fibrocartilage. At rates of 0.7 (4 weeks) and 1.3mm/day (2 weeks), the bone that grows from the cut ends of the cortical bone is separated by fibrous tissue and cartilage is present. At 2.7mm/day (1 week), only fibrous tissue and sparse bone are present. Type I collagen is present in the matrices around the cells expressing its mRNA and similarly, type II collagen is located around the chondrocytes. Type I collagen mRNA is expressed predominantly by the fibroblasts in the fibrous tissue, the bone surface cells and to a reduced extent by the osteocytes. Type II collagen mRNA is expressed by chondrocytes. The results suggest that osteoblasts and chondrocytes within the regenerate originate from the same pool of progenitor cells, and the differentiation of these cells and the expression of types I and II collagen genes are altered by different rates of distraction. These observations suggest that the optimal rate of distraction in the model is 0.7mm/day.

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