Age-related changes in the extracellular matrix of nucleus pulposus and anulus fibrosus of human intervertebral disc.
METHODS
To characterize age-related changes in the matrix of human intervertebral disc (IVD) specimens, human specimens from the third to the eighth decade of life were collected and analyzed for collagen and proteoglycan (PG) composition.


OBJECTIVE
To identify age-related changes in the concentration of matrix macromolecules (collagen and PGs, including the small leucine-rich PGs biglycan, decorin, fibromodulin, and lumican) in human anulus fibrosus (AF) and nucleus pulposus (NP).


BACKGROUND
IVD degeneration is associated with changes in the concentration and fragmentation of matrix molecules. Deciphering age-related matrix alterations may help us to better understand the regulatory mechanisms underlying IVD degeneration.


METHODS
Forty-six whole IVDs were obtained from the thoracolumbar spines (T11-L5) of humans aged between 32 and 80 years. All specimens were classified as Thompson grade 1 or 2 according to MRI criteria. Specimens were separated into (i) outer-and (ii) inner AF, and (iii) NP. DNA, collagen, and PG contents were measured using chemical assays, whereas small nonaggregating PG levels were analyzed by comparative Western blotting.


RESULTS
Total PG and collagen contents in both the AF and NP consistently decreased with aging. The concentrations of small nonaggregating PGs varied. In the outer anulus, decorin levels decreased, whereas biglycan and fibromodulin levels increased with age. In the inner anulus and nucleus, biglycan demonstrated a significant increase with aging. These changes differed in most cases from those previously reported for degenerating disc tissues.


CONCLUSIONS
Collagen and PGs appeared to undergo specific age-related changes in the human IVD. Although the total contents of these 2 families of molecules decreased during aging, individual species of small nonaggregating PGs showed species-specific age-related changes. Interestingly, the level of biglycan rose and remained elevated in all 3 compartments of the disc with aging. The functional significance of these alterations is yet to be determined.
Singh
Kern
K
Department of Orthopedic Surgery, Rush Medical College at Rush University Medical Center, 1652 W. Congress Parkway, Chicago, IL 60612, USA.
Masuda
Koichi
K
Thonar
Eugene J-M A
EJ
An
Howard S
HS
Cs-Szabo
Gabriella
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D058578:Biglycan; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D058575:Decorin; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D000071235:Fibromodulin; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism*; D007632:Keratan Sulfate / Q000378:metabolism; D008159:Lumbar Vertebrae; D000071234:Lumican; D008297:Male; D008875:Middle Aged; D011509:Proteoglycans / Q000378:metabolism*; D013904:Thoracic Vertebrae
C546884:BGN protein, human; D058578:Biglycan; D011508:Chondroitin Sulfate Proteoglycans; C546878:DCN protein, human; D058575:Decorin; D016326:Extracellular Matrix Proteins; C000604330:FMOD protein, human; C000604306:LUM protein, human; D000071234:Lumican; D011509:Proteoglycans; D000071235:Fibromodulin; D003094:Collagen; D004247:DNA; D007632:Keratan Sulfate