Ultrastructural immunolocalization of alpha-elastin and keratan sulfate proteoglycan in normal and scoliotic lumbar disc.
METHODS
Comparative ultrastructural study of intervertebral discs from normal subjects and patients with scoliosis.


OBJECTIVE
To identify ultrastructural relations among keratan sulfate (KS) proteoglycan, alpha-elastin, collagen fibers, and elastic fibers in normal and scoliotic discs.


BACKGROUND
KS proteoglycans, elastic fibers, and collagen fibers play important mechanical roles in the intervertebral disc, but the distributions of KS proteoglycans and elastin in this tissue have received little attention.


METHODS
Tissues were fixed in 4% paraformaldehyde. Monoclonal antibody 5-D-4 (which recognizes a KS epitope on aggrecan, fibromodulin, and lumican) and polyclonal anti-alpha-elastin were visualized with a 10-nm immunogold-conjugated secondary antibody.


RESULTS
In a normal disc, a regular pattern of KS labeling occurred around collagen fibers, in the cell cytoplasm, and in the rough endoplasmic reticulum; the nucleus pulposus was more densely labeled for KS than was the anulus fibrosus. In scoliotic disc anulus fibrosus, KS labeling was weak throughout the matrix and pericellularly but abundant in lysosomes and on electron-dense material in degenerate cells. Degenerate collagen fibers in scoliotic tissue bore less KS than did normal fibers. KS labeling of the microfibrillar region of elastic fibers was strong in normal disc but weak in scoliotic disc. Elastin labeling of elastic fibers was weaker in scoliotic than in normal tissue.


CONCLUSIONS
KS proteoglycans and elastic fibers are closely associated with the lamellar organization of the collagen fibers in a normal disc. In scoliosis, impaired regulation of collagen fibrillogenesis by lumican or fibromodulin may result in disruption of the lamellar structure.
Akhtar
Saeed
S
School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom. akhtars@cardiff.ac.uk
Davies
Janet R
JR
Caterson
Bruce
B
D000293:Adolescent; D000328:Adult; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis / Q000648:ultrastructure*; D004549:Elastin / Q000032:analysis / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000648:ultrastructure*; D007632:Keratan Sulfate / Q000032:analysis / Q000648:ultrastructure*; D008159:Lumbar Vertebrae / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure*; D000071234:Lumican; D008297:Male; D012600:Scoliosis / Q000473:pathology*
D011508:Chondroitin Sulfate Proteoglycans; C000604306:LUM protein, human; D000071234:Lumican; D004549:Elastin; D007632:Keratan Sulfate