Uni-axial cyclic stretch induces Cbfa1 expression in spinal ligament cells derived from patients with ossification of the posterior longitudinal ligament.
Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. Mechanical stress, which acts on the posterior ligaments, is thought to be an important factor in the progression of OPLL. To clarify this mechanism, we investigated the effects of in vitro cyclic stretch (120% peak to peak, at 0.5 Hz) on cultured spinal ligament cells derived from OPLL (OPLL cells) and non-OPLL (non-OPLL cells) patients. The mRNA expressions of Cbfa1 (an osteoblast-specific transcription factor), type I collagen, alkaline phosphatase (ALP), osteocalcin and integrin beta1 (a mechanotransducer) were increased by cyclic stretch in OPLL cells, whereas no change was observed in non-OPLL cells. The effects of cyclic stretch on the spinal ligament tissues derived from OPLL and non-OPLL patients were also analyzed by immunohistochemistry using an antibody against Cbfa1. The expression of Cbfa1 was increased by cyclic stretch at the center of the spinal ligament tissues of OPLL patients, whereas no change was observed in the tissues of non-OPLL patients. Furthermore, U0126, a specific inhibitor of MAPK kinase (MEK), suppressed the stretch-induced mRNA expressions of Cbfa1, ALP and type I collagen in OPLL cells. These results suggest that in OPLL cells, mechanical stress is converted by integrin beta1 into intracellular signaling and that Cbfa1 is activated through the MAP kinase pathway. Therefore, we propose that mechanical stress plays a key role in the progression of OPLL through an increase in Cbfa1 expression.
Iwasaki
K
K
Department of Pharmacology, Hirosaki University School of Medicine, Hirosaki, Japan.
Furukawa
K-I
KI
Tanno
M
M
Kusumi
T
T
Ueyama
K
K
Tanaka
M
M
Kudo
H
H
Toh
S
S
Harata
S
S
Motomura
S
S
D000368:Aged; D000469:Alkaline Phosphatase / Q000096:biosynthesis / Q000187:drug effects; D002070:Butadienes; D002478:Cells, Cultured; D024042:Collagen Type I / Q000096:biosynthesis / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D039641:Integrin beta Chains / Q000096:biosynthesis / Q000187:drug effects; D017846:Longitudinal Ligaments / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009570:Nitriles; D017887:Ossification of Posterior Longitudinal Ligament / Q000378:metabolism* / Q000503:physiopathology; D009999:Ossification, Heterotopic / Q000378:metabolism*; D015675:Osteocalcin / Q000096:biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000096:biosynthesis*
D002070:Butadienes; D024042:Collagen Type I; D050659:Core Binding Factor Alpha 1 Subunit; D004791:Enzyme Inhibitors; D039641:Integrin beta Chains; D009363:Neoplasm Proteins; D009570:Nitriles; D012333:RNA, Messenger; D014157:Transcription Factors; C113580:U 0126; D015675:Osteocalcin; D020929:Mitogen-Activated Protein Kinase Kinases; D000469:Alkaline Phosphatase