Role of Prostaglandin I₂in the Gene Expression Induced by Mechanical Stress in Spinal Ligament Cells Derived from Patients with Ossification of the Posterior Longitudinal Ligament

Abstract

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments, and mechanical stress has been suggested to play an important role in the progression of OPLL. To identify the genes that participate in OPLL, the differential display reverse transcription-polymerase chain reaction (RT-PCR) method was used. A 283-base pair cDNA fragment corresponding to prostaglandin I 2 (PGI 2 ) synthase was highly expressed in OPLL cells compared with non-OPLL cells. To examine the effect of mechanical stress on the expression of PGI 2 synthase, cells were subjected to uniaxial cyclic stretch (0.5 Hz, 20% stretch), and PGI 2 synthase mRNA expression was assessed by quantitative RT-PCR. Cyclic stretch induced an increase in PGI 2 synthase in OPLL cells in a time-dependent manner, whereas no change was observed in non-OPLL cells. Cyclic stretch for 9 h also induced a 2.86ϫ increase in PGI 2 production. Beraprost (a stable PGI 2 analog) and dibutyryl cAMP (a membrane-permeable cAMP analog) increased the mRNA expression of alkaline phosphatase (ALP) as a marker for osteogenic differentiation up to 240 and 200%, respectively, in OPLL cells, whereas no change was observed in non-OPLL cells. The increases in ALP mRNA induced by beraprost and cyclic stretch were both inhibited by SQ22536, a potent adenylate cyclase inhibitor. These data suggest that the increase in PGI 2 synthase induced by mechanical stress plays a key role in the progression of OPLL, at least in part through the induction of osteogenic differentiation in spinal ligament cells via the PGI 2 /cAMP system.

Upregulated expression of PERK in spinal ligament fibroblasts from the patients with ossification of the posterior longitudinal ligament

“…Attempts have been made to simulate the mechanical stress in vitro, mostly with a motor-driven uniaxial sinusoidal cyclic stretch [18]. The system induced the transcription of messenger ribonucleic acids of several growth factors, including BMP-2, BMP-4, prostaglandin I 2 synthase, and osteoblast-specific transcription factor in the cells from OPLL patients [9,19,24,30]. At the same time, several studies have suggested that ER stress response can be activated by mechanical stress in some cellular pathological processes, such as apoptosis in rat annulus fibrosus cells or human connective tissue cells [32].…”

Ossification of the posterior longitudinal ligament: a review

“…22 Prostacyclin synthase levels in ligament cells from OPLL patients have been shown to be elevated after applying mechanical stress and induced osteogenic differentiation via the PGI 2 / cyclic adenosine monophosphate pathway. 97 Mechanical stress also induces mRNA expression of alkaline phosphatase, osteopontin, BMP-2, BMP-4, BMP receptors, 121 and mRNA expression of Cbfa1, Type I collagen, osteocalcin, integrin b1, 43 and endothelin-1. 47 The P2Y1 purinoceptor subtypes, intensively expressed in OPLL cells, responded to mechanical stress-induced extracellular adenosine triphosphate, which stimulated OPLL progression.…”

Current Topics in Pharmacological Research on Bone Metabolism: Molecular Basis of Ectopic Bone Formation Induced by Mechanical Stress

“…Addition of BMP-2 or conditioned medium from OPLL cells exposed to cyclic stretching enhanced the expression of ALP in OPLL cells, and this effect was significantly blocked by an anti-BMP antibody (20). As suggested by the cyclic stretch-induced PGI 2 synthase expression (Table 1), enhanced release of prostacyclin was observed in OPLL cells (8). Furthermore, addition of beraprost, a stable Fig.…”