Bone morphogenetic protein-7 protects human intervertebral disc cells in vitro from apoptosis.
BACKGROUND
Disc degeneration includes dysfunction and loss of disc cells leading to a decrease in extracellular matrix (ECM) components. Apoptosis has been identified in degenerated discs. Bone morphogenetic protein-7 (BMP-7) has been reported to stimulate ECM synthesis in the intervertebral disc (IVD), but its effect on disc cell viability is unknown.


OBJECTIVE
To investigate whether BMP-7 can protect disc cells from programmed cell death while enhancing ECM production.


METHODS
An in vitro study to examine the effect of BMP-7 on apoptosis of IVD cells.


METHODS
Human nucleus pulposus (NP) cells were cultured in monolayer, and human recombinant pure BMP-7 (rhBMP-7) was added to the medium when the cells were in the second passage. Thereafter, apoptosis was induced by either tumor necrosis factor-alpha (TNF-alpha) or hydrogen peroxide (H(2)O(2)). Cellular apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and caspase-3 activity. ECM synthesis was assessed by immunofluorescence for collagen-2 and aggrecan. To study the possibility of bone induction by rhBMP-7 in disc cells, alkaline phosphatase activity and Alizarin red-S staining were evaluated.


RESULTS
Apoptosis was induced by both TNF-alpha and H(2)O(2). Addition of rhBMP-7 resulted in inhibition of the apoptotic effects caused by both inducers. Further, BMP-7 decreased caspase-3 activity. In the presence of BMP-7, ECM production was maintained by the cells despite being in an apoptotic environment. No osteoblastic induction of the disc cells was seen.


CONCLUSIONS
BMP-7 was demonstrated to prevent apoptosis of human disc cells in vitro. One of the antiapoptotic effects of BMP-7 on NP cells might be a result of its inactivation of caspase-3. Collagen production was maintained by addition of rhBMP-7 in an apoptotic environment.
Wei
Aiqun
A
Orthopaedic Research Institute, The University of New South Wales, St George Hospital Campus, level 2, 4-10 South Street, Kogarah, NSW 2217, Australia.
Brisby
Helena
H
Chung
Sylvia A
SA
Diwan
Ashish D
AD
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D053938:DNA Fragmentation; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D006801:Humans; D007403:Intervertebral Disc / Q000187:drug effects* / Q000378:metabolism; D008875:Middle Aged; D011994:Recombinant Proteins / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D016326:Extracellular Matrix Proteins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta