Mechanism of intervertebral disc degeneration caused by nicotine in rabbits to explicate intervertebral disc disorders caused by smoking.
METHODS
The effects of nicotine on intervertebral discs in rabbits were studied experimentally.


OBJECTIVE
To investigate the effects of nicotine on the vascular buds in rabbits for elucidating the mechanism of nicotine-induced vertebral disc degeneration.


BACKGROUND
Several groups have suggested that cigarette smoking is associated with low back pain, but the exact mechanism is not yet fully understood.


METHODS
The pump was filled with a diluted nicotine solution, then implanted under the skin of rabbits for 8 weeks. This model was designed to maintain blood nicotine concentration at approximately 110 ng/mL. Rabbits receiving physiologic saline were used as control animals.


RESULTS
Nicotine treatment resulted in necrosis and hyalinization of the nucleus pulposus in all rabbits. The anulus fibrosus showed a disturbance of the pattern of overlapping laminae with and without clefts and separation. These resulted in changes indicative of stenosis of vascular buds and perivascular calcification. Nicotine treatment resulted in hypertrophy of vascular walls, necrotic changes in endothelial cells, and narrowing of the vascular lumen. Nicotine treatment resulted in delineation of vascular buds in the vicinity of the vertebral endplate and a reduction of their numbers. However, the control animals showed a dense vascular network. The number of vascular buds decreased in nicotine treatment.


CONCLUSIONS
The authors believe that both reduction in the density of vascular buds and narrowing of the vascular lumen result in decreased oxygen tension, leading to decreased synthesis of proteoglycan and collagen, thus facilitating degeneration of the disc.
Department of Orthopaedic Surgery, Nihon University School of Medicine, Tokyo, Japan. masaki3@ms.tokyo.jcom.ne.jp
Masaki
M
Iwahashi
Hiromi
H
Matsuzaki
Yasuaki
Y
Tokuhashi
Ken
K
Wakabayashi
Yoshinao
Y
Uematsu
D000818:Animals; D001808:Blood Vessels / Q000187:drug effects / Q000473:pathology; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D005260:Female; D015918:Infusion Pumps, Implantable; D007403:Intervertebral Disc / Q000098:blood supply / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D007405:Intervertebral Disc Displacement / Q000139:chemically induced* / Q000473:pathology; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000473:pathology; D009538:Nicotine / Q000008:administration & dosage / Q000633:toxicity*; D011817:Rabbits; D013116:Spinal Cord / Q000187:drug effects / Q000473:pathology
D009538:Nicotine