Abstract
Background: The intervertebral disc and spinal ligaments contain extensive and well organised elastic fibre networks which provide these tissues with elasticity. Morphologically elastic fibres are composed of an amorphous central core consisting mainly of elastin surrounded by a microfibrillar mesh. The importance of the microfibrils has been emphasised by the clinical manifestations of Marfan Syndrome (MFS) and congenital contractual arachnodactyly (CCA) which are caused respectively by mutations of Fibrillin-1 and Fibrillin-2, the main protein components of the microfibrillar mesh. Both patients of MFS and CCA can develop a spinal deformity. Recent studies on genetically modified mice suggested that minor components of the microfibrillar mesh can also play an important role in spine development; knockout mice containing no fibulin-5, microfibrillar associated glycoprotein-2 (MAGP-2), or latent TGF-b protein 3 (LTBP-3) can all develop spinal deformity. Our aim in this study was to understand the involvement of elastic fibre system in pathogenesis of scoliosis.
Methods: Tissue from Marfan patients and adolescent idiopathic kyphoscoliotic human intervertebral discs were removed during routine surgery with consent and ethical permission. Here we report on examination of disc tissue from three Marfan’s syndrome and three AIS patients (with ethical approval), age range 13–33 years. Tissues were dissected and then snap frozen within 4 hours after surgical excision and kept in −80 OC till used. Tissue sections of 20 micron were cut with a cryostat microtome and fixed with 10% formalin before immunostaining. Microfibrils and elastin fibre network were studied by immunostaining fibrillin-1 and elastin. The collagen network was examined by using fluores-cent microscopy with a polarised light system. Spines from transgenic mice, producing no elastin or fibulin-5, were paraffin embedded and sections were stained with Haematoxylin & Eosin or Alcien Blue. The morphology of cells, vertebral body and disc matrix were studied at light microscopic level.
Results and Discussion: Our histological studies on IVD tissues from MFS and AIS patients found that the elastic fibre and collagen networks were disorganised compared to that of normal controls. Studies on spines from fibulin-5 null or elastin null mice indicated delayed ossification of the vertebral body, lower expression of proteoglycans and an abnormal growth plate. Our initial results thus indicate that the elastic fibre system has an effect on matrix synthesis in connective tissue and plays a part in regulating bone growth. They are in agreement with reports that kypho-scoliosis occurs in transgenic mice deficient in other matrix components e.g. collagen-II and perlecan. Matrix-generated regulation of spine development and vertebral body growth thus appears to play an important role in the development of scoliosis.
Correspondence should be addressed to Jeremy C T Fairbank at The Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX7 7LD, UK
We thank the British Scoliosis Research Society and the Arthritis Research Campaign for support.
