Tumor necrosis factor-alpha modulates matrix production and catabolism in nucleus pulposus tissue.
METHODS
This study examines changes in the production of extracellular matrix molecules as well as the induction of tissue degradation in in vitro formed nucleus pulposus (NP) tissues following incubation with tumor necrosis factor (TNF)alpha.


OBJECTIVE
To characterize the response of NP cells to TNF-alpha, a proinflammatory cytokine present in herniated NP tissues.


BACKGROUND
TNF-alpha is a proinflammatory cytokine expressed by NP cells of degenerate intervertebral discs. It is implicated in the pain associated with disc herniation, although its role in intervertebral disc degeneration remains poorly understood.


METHODS
In vitro formed NP tissues were treated with TNF-alpha (up to 50 ng/mL) over 48 hours. Tissues were assessed for histologic appearance, proteoglycan and collagen contents, as well as proteoglycan and collagen synthesis. Reverse transcriptase polymerase chain reaction was used to determine the effect of TNF-alpha on NP cell gene expression. Proteoglycan degradation was assessed by immunoblot analysis.


RESULTS
At doses of 1-5 ng/mL, TNF-alpha induced multiple cellular responses, including: decreased expression of both aggrecan and type II collagen genes; decreases in the accumulation and overall synthesis of aggrecan and collagen; increased expression of MMP-1, MMP-3, MMP-13, ADAM-TS4, and ADAM-TS5; and induction of ADAM-TS dependent proteoglycan degradation. Within 48 hours, these cellular responses resulted in NP tissue with only 25% of its original proteoglycan content.


CONCLUSIONS
Because low levels of TNF-alpha, comparable to those present physiologically, induced NP tissue degradation, this suggests that TNF-alpha may contribute to the degenerative changes that occur in disc disease.
Séguin
Cheryle A
CA
BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital, Ontario, Canada.
Pilliar
Robert M
RM
Roughley
Peter J
PJ
Kandel
Rita A
RA
D051722:ADAM Proteins / Q000378:metabolism; D053674:Aggrecans; D000818:Animals; D002417:Cattle; D011508:Chondroitin Sulfate Proteoglycans / Q000187:drug effects / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism* / Q000473:pathology; D037181:Lectins, C-Type / Q000187:drug effects / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D046509:Tissue Culture Techniques; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*
D053674:Aggrecans; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D011994:Recombinant Proteins; D019714:Tissue Inhibitor of Metalloproteinases; D014409:Tumor Necrosis Factor-alpha; D003094:Collagen; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases