Role of MAPK signaling pathway in osteopontin-mediated ossification of the ligamentum flavum / 中国组织工程研究

ABSTRACT

BACKGROUND:Mitogen-activated protein kinase (MAPK) signaling pathway is an important signal transduction system.Our precious animal experiments have shown that osteopontin can mediate the ossification of the ligamentum flavum.OBJECTIVE:To investigate the role of MAPK signaling pathway in osteopontin-induced ossification of the ligamentum flavum.METHODS:The ligamentum flavum specimens obtained from 16 cases undergoing thoracic/lumbar posterior decompression surgery were divided into ossification and non-ossification groups (n=8 per group).The expression of osteopontin and its receptors CD44 and integrin was observed by immunohistochemical staining.The activation of phosphorylation in MAPK signaling pathway was detected by western blot assay.The MAPK signaling pathway was blocked by SB203580 or U0126 blocker alone to observe the induction of osteopontin.RESULTS AND CONCLUSION:Osteopontin and its receptor CD44 were expressed in the ossification group,but not in the non-ossififcation group.However,the expression of integrin was not detected in the ossification group.The expression levels of alkaline phosphatase and osteocalcin in the ligamentum flavum were significnatly increased under the induction of osteopontin (P ＜ 0.05),and osteopontin could activate the phosphorylation of P38 and ERK1/2 in the MAPK signaling pathway (P ＜ 0.05),but the phosphorylation of JNK was not obvious.p38 phosphorylation blocked with SB203580 blocker could significantly inhibit the osteopontin-induced osteoblast differentiation of ligament flavum cells (P ＜ 0.05),while U0126 blocker had no obvious effect.These results indicate that p38 in MAPK signaling pathway is a key molecule in osteopontin-mediated ossification of the ligamentum flavum.