IGF-1 regulation of type II collagen and MMP-13 expression in rat endplate chondrocytes via distinct signaling pathways

• Published in: Osteoarthritis and cartilage Vol. 17; no. 1; pp. 100 - 106
• Main Authors: Zhang, M., Ph.D, Zhou, Q., M.D., Ph.D, Liang, Q.-Q., Ph.D, Li, C.-G., M.D, Holz, J.D., M.S, Tang, D., M.D, Sheu, T.-J., Ph.D, Li, T.-F., M.D., Ph.D, Shi, Q., M.D, Wang, Y.-J., M.D., Ph.D
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-01-2009
• Subjects: Animals; Cells, Cultured; Cervical Vertebrae - drug effects; Cervical Vertebrae - metabolism; Chondrocytes - drug effects; Chondrocytes - metabolism; Col2a1; Collagen Type II - biosynthesis; Collagen Type II - genetics; Dose-Response Relationship, Drug; Down-Regulation - drug effects; Endplate chondrocyte; ERK/MAPK; Gene Expression Regulation, Enzymologic - drug effects; IGF-1; Insulin-Like Growth Factor I - pharmacology; MAP Kinase Signaling System - drug effects; MAP Kinase Signaling System - physiology; Matrix Metalloproteinase 13 - biosynthesis; MMP-13; PI3K; Rats; Rats, Sprague-Dawley; Rheumatology; RNA, Messenger - genetics; Transcription, Genetic; Up-Regulation - drug effects; Col2a1; MMP-13; IGF-1; Endplate chondrocyte; PI3K; ERK/MAPK
• ISSN: 1063-4584; 1522-9653
• DOI: 10.1016/j.joca.2008.05.007

Summary Objective Abnormal maturation and ossification of the endplate chondrocytes play a central role in the pathogenesis of degenerative disorders of the cervical spine. It is widely held that insulin like growth factor-1 (IGF-1) stimulates chondrocyte proliferation and inhibits chondrocyte terminal differentiation both in vitro and in vivo . However, the mechanism underlying such regulation is not fully understood. The present study aimed to determine the role of IGF-1 on the mRNA expression of collagen type II, alpha 1 (Col2a1) and matrix metallopeptidase 13 (MMP-13) in rat endplate chondrocytes. The possible pathways that transduce IGF-1 effects such as phosphatidylinositol-3 (PI-3)-kinase (PI3K) and mitogen activated protein kinase (MAPK) were also investigated in these cells. Methods Cultured endplate chondrocytes harvested from rat cervical spines were treated with IGF-1 (100 ng/ml), and the changes in Col2a1 and MMP-13 mRNA were monitored with real-time polymerase chain reaction (PCR). MMP-13 activity was also assayed. Activation of signaling proteins was evaluated by western blot analysis. Cells were also treated with pharmacological agents that block PI3K and MAPK signaling pathways. Results IGF-1 increased Col2a1 mRNA expression in rat endplate chondrocytes in a time- and dose-dependent manner. IGF-1 treatment resulted in a fourfold increase of Col2a1 mRNA with the effect maximizing at 24 h. In contrast, IGF-1 treatment for 24 h caused a roughly 50% reduction in MMP-13 mRNA. Similar effects were seen on the protein levels of type II collagen (col2) and MMP-13. Consistent with these results, IGF-1 also repressed MMP-13 activity. IGF-1 activated both the PI3K and the extracellular signal-regulated kinase (ERK) pathways as evidenced by phosphorylation of either Akt or ERK1/2 (respectively). The PI3K inhibitor Wartmannin significantly inhibited the IGF-1 effect on Col2a1 mRNA expression but did not affect IGF-1-induced repression of MMP-13 expression. In contrast, the ERK/MAPK inhibitor PD98059 significantly inhibited the effect of IGF-1 on MMP-13 mRNA repression and enhanced IGF-1-induced Col2a1 mRNA expression. Conclusions In rat endplate chondrocytes the PI3K pathway mainly transduces IGF-1 effect on col2 expression while the ERK pathway mediates IGF-1 effect on MMP-13 expression.