Effect of circumferential constraint on nucleus pulposus tissue in vitro.
BACKGROUND
Degeneration of the intervertebral disc (IVD) involves structural changes in the annulus fibrosus (AF), which could alter the mechanical forces imposed on the nucleus pulposus (NP) tissue. This could contribute to degenerative changes that occur in the NP.


OBJECTIVE
The purpose of the study was to determine whether circumferential constraint affects anabolic and catabolic gene expression, biochemical composition, and mechanical properties of NP tissue.


METHODS
Nucleus pulposus cells were isolated from bovine caudal IVD and allowed to form tissue for a period of two weeks. The effect of no, intermediate, or high circumferential constraint on biochemical composition (cellularity and proteoglycan and collagen synthesis), gene expression, and compressive mechanical properties was evaluated.


RESULTS
Increasing the rigidity of circumferential constraint surrounding in vitro formed NP tissue resulted in decreased gene expression of aggrecan and type II collagen and increased expression of MMP-1 and ADAMTS-5. This was associated with decreased accumulation of extracellular matrix and a deterioration of the compressive mechanical properties of the tissue.


CONCLUSIONS
As increased circumferential constraint can have a significant negative effect on the composition and quality of NP tissue and this raises the possibility that the AF may contribute to the degenerative or age-related alterations that occur in the NP. Further study in a functional spinal unit is required to validate this.
Hamilton
Darla J
DJ
CIHR-BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital, 600 University Ave., Suite 6-441, Toronto, Ontario M5G 1X5, Canada.
Pilliar
Robert M
RM
Waldman
Stephen
S
Kandel
Rita A
RA
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D053674:Aggrecans / Q000235:genetics / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D007403:Intervertebral Disc / Q000378:metabolism* / Q000503:physiopathology; D020781:Matrix Metalloproteinase 1 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical
D053674:Aggrecans; D024043:Collagen Type II; D012333:RNA, Messenger; D051722:ADAM Proteins; D020781:Matrix Metalloproteinase 1