Zonal responsiveness of the human intervertebral disc to bone morphogenetic protein-2.
METHODS
In vitro experiment using bone morphogenetic protein-2 (BMP-2) and cells from the nucleus pulposus (NP), transitional zone (TZ), and anulus fibrosus (AF) of the human intervertebral disc (IVD).


OBJECTIVE
To demonstrate the differential effect of BMP-2 on DNA synthesis, proteoglycan synthesis, and osteocalcin mRNA expression in human IVD cells from the NP, TZ, and AF, respectively.


BACKGROUND
BMP-2 has been proven to be effective in stimulating proteoglycan synthesis in articular chondrocytes and IVD cells from the NP. Nevertheless, the effect of BMP-2 on cells from different regions of the IVD has not yet been thoroughly elucidated.


METHODS
Human IVDs were harvested from surgical disc procedures and tissue from the NP, TZ, and AF was obtained. Disc tissue was enzymatically digested, and IVD cells were cultured three-dimensionally in alginate beads. Then IVD cell cultures from the NP, TZ, and AF were exposed to BMP-2. DNA synthesis and newly synthesized proteoglycan were measured. Reverse transcription-polymerase chain reaction for mRNA expression of bone sialoprotein, DLX5, osteocalcin, and collagen type I, was performed.


RESULTS
Cells from the AF responded to BMP-2 with mitogenesis. There was no significant increase in DNA synthesis in cultures from the NP and TZ treated with BMP-2. Only cells from the NP showed a significant increase in newly synthesized proteoglycan in response to BMP-2. IVD cells from all zones demonstrated no significant expression of bone sialoprotein, DLX5, osteocalcin mRNA after treatment with BMP-2.


CONCLUSIONS
BMP-2 clearly exerted a mitogenic effect on AF cells, and stimulated proteoglycan synthesis in NP cells. However, BMP-2 did not have an osteogenic effect in any IVD region. Taken together, these results confirm that BMP-2 can be used as an anabolic agent for mitogenesis in AF cells and NP cell matrix regeneration without the possibility of osteogenesis.
Kim
Hyang
H
Medical Science Graduated School, Yonsei University College of Medicine, Seoul, Korea.
Lee
Jeong-Uk
JU
Moon
Seong-Hwan
SH
Kim
Hyung-Chan
HC
Kwon
Un-Hae
UH
Seol
Nam-Hun
NH
Kim
Ho-Joong
HJ
Park
Jin-Oh
JO
Chun
Heoung-Jae
HJ
Kwon
Il-Keun
IK
Lee
Hwan-Mo
HM
D000328:Adult; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D024042:Collagen Type I / Q000235:genetics; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D007403:Intervertebral Disc / Q000187:drug effects* / Q000378:metabolism* / Q000503:physiopathology; D007405:Intervertebral Disc Displacement / Q000188:drug therapy* / Q000378:metabolism* / Q000503:physiopathology; D008875:Middle Aged; D015675:Osteocalcin / Q000235:genetics; D053495:Osteopontin / Q000235:genetics; D011509:Proteoglycans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012038:Regeneration / Q000187:drug effects* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D024042:Collagen Type I; C100596:DLX5 protein, human; D018398:Homeodomain Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D014157:Transcription Factors; D015675:Osteocalcin; D053495:Osteopontin; D004247:DNA