Expression of ADAMTS-7 and ADAMTS-12 in Nucleus Pulposus during Degeneration of Rat Caudal Intervetebral Disc

Abstract

Earlier reports have shown that ADAMTS-7 and ADAMTS-12 (a disintegrin and metalloproteinase with thrombospondin motifs) can bind to and degrade COMP (cartilage oligomerix matrix protein) in cartilage. However, the expression of ADAMTS-7, 12 in both normal intervertebral discs and degenerative intervertebral discs (IVD) is still unknown and the changes that occur in the degenerating intervetebral disc remain to be determined. The aim of this study was to explore the expression and role of the ADAMTS in degenerative process of intervertebral disc. Rat caudal discs were loaded at 1.3 MPa in vivo with an external compression device. The discs were loaded for one week, and nucleus pulposus (NP) were harvested to investigate cell apoptosis and expression of collagen II and aggrecan for confirmation of disc degeneration. The changes of ADAMTS-7, 12 and COMP were recorded during one-week loading. A second group of rats receiving no load were used as controls. After one-week of loading, the NP suffered degenerative changes as reflected by decreases in cell viability, collagen II, and aggrecan. Dramatic increase in expression of ADAMTS-7, 12 and COMP fragment were detected after 18 hr of loading; this was however accompanied by sharp decrease of COMP expression. These changes were not observed in the control group. The significant increase in COMP possibly suggests a favorable role of COMP in preventing loading and degeneration of matrix, however this positive effect might be diminished by ADAMTS-7 and ADAMTS-12, whose augmentation were dramatic during disc degeneration.