title: Repetitive tensile stress to rat caudal vertebrae inducing cartilage formation in the spinal ligaments: a possible role of mechanical stress in the development of ossification of the spinal ligaments.
abstract: OBJECTIVE
  Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed.
  
  
  METHODS
  The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically. After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein-2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans.
  
  
  CONCLUSIONS
  The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Tsukamoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Maeda
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Miura
authors.forename: Seiya
authors.initials: S
authors.lastname: Jingushi
authors.forename: Akira
authors.initials: A
authors.lastname: Hosokawa
authors.forename: Katsumi
authors.initials: K
authors.lastname: Harimaya
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Higaki
authors.forename: Kousaku
authors.initials: K
authors.lastname: Kurata
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism; D017846:Longitudinal Ligaments / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D017887:Ossification of Posterior Longitudinal Ligament / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D009418:S100 Proteins / Q000378:metabolism; D055758:SOX9 Transcription Factor; D013314:Stress, Mechanical; D013623:Tail; D013718:Tensile Strength / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D006609:High Mobility Group Proteins; D009418:S100 Proteins; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D014157:Transcription Factors