Localization of degradative enzymes and their inhibitors in the degenerate human intervertebral disc

Abstract

The histological and biochemical changes that occur in the extracellular matrix of the intervertebral disc (IVD) during ageing and degeneration have been investigated extensively. However, the mechanisms behind these changes are not fully understood. A number of studies have suggested the involvement of matrix metalloproteinases (MMPs) and ADAMTS in IVD degeneration, but few have localized the site of production of these enzymes to the cells of the degenerate disc. This study uses immunohistochemical techniques to localize and quantify the production of degrading enzymes (MMPs 1, 3, and 13, and ADAMTS 4) and their inhibitors (TIMPS 1, 2, and 3) within non-degenerate and degenerate discs of varying severity of degeneration. In all discs investigated, the cells that produced the enzymes and their inhibitors were the chondrocyte-like cells of the nucleus pulposus and inner annulus fibrosus (AF), with little immunopositivity in the outer AF. Non-degenerate discs showed low numbers of cells expressing the degradative enzymes MMP 1 and ADAMTS 4, suggesting a role for these enzymes in normal homeostasis. No MMP 3 or MMP 13 immunopositivity was observed in non-degenerate discs. In degenerate discs, the number of cells immunopositive for MMPs 1, 3, 13 and ADAMTS 4 increased with the severity of degeneration. This increase in degrading enzymes was also accompanied by increases in the number of cells immunopositive for TIMPs 1 and 2 but not TIMP 3. This study highlights that although the expression of a number of MMPs increases with degeneration, this is accompanied by an increase in their inhibitors. However, the increase in the number of cells immunoreactive for ADAMTS 4 with increasing degeneration was not paralleled by a rise in its inhibitor TIMP 3. This finding indicates that the aggrecanases, rather then the MMPs, are a possible therapeutic target for the inhibition of disc degeneration.

Transcript levels of major MMPs and ADAMTS-4 in relation to the clinicopathological profile of patients with lumbar disc herniation

“…Numerous studies in literature have examined the protein expression levels of MMPs and ADAMTS in human herniated discs [10,19,20,26,29]. Using immunohistochemical techniques, Weiler et al [29] found a significant correlation between MMP protein activity and histological signs of degeneration in human IDs.…”

Biological impact of the fibroblast growth factor family on articular cartilage and intervertebral disc homeostasis

“…For example, as matrix equilibrium shifts to a pro-catabolic state with advancing degeneration in articular cartilage, collagenasemediated degradation of type II collagen becomes more prominent (Hollander et al, 1994;Billinghurst et al, 1997). Among the collagenases, collagenase-3 (MMP-13) has been found to play a significant role in the development of both OA and DDD (Billinghurst et al, 1997;Fernandes et al, 1998;Anderson et al, 2002;Le Maitre et al, 2004). In articular cartilage, MMP-13 is almost exclusively produced by chondrocytes and has a dual role in ECM *Correspondence to : Hee-Jeong Im, Ph.D., Cohn Research BD 516, 1735 W. Harrison, Chicago, IL 60612, 312-942-3091 (Tel), 312-942-3053 (fax), Email : Hee-Jeong_Sampen@rush.edu.destruction as it degrades bothaggrecan and collagen type II (Fosang et al, 1996;Mitchell et al, 1996;Reboul et al, 1996;Fernandes et al, 1998).…”

“…In articular cartilage, MMP-13 is almost exclusively produced by chondrocytes and has a dual role in ECM *Correspondence to : Hee-Jeong Im, Ph.D., Cohn Research BD 516, 1735 W. Harrison, Chicago, IL 60612, 312-942-3091 (Tel), 312-942-3053 (fax), Email : Hee-Jeong_Sampen@rush.edu.destruction as it degrades bothaggrecan and collagen type II (Fosang et al, 1996;Mitchell et al, 1996;Reboul et al, 1996;Fernandes et al, 1998). In the IVD, MMP-13 expression increases with increasing severity of disc degeneration (Le Maitre et al, 2004). Therefore, defining the key factors, receptors, and regulators of MMP-13 expression is important to clearly understand the molecular etiology of OA and DDD.…”

What is Intervertebral Disc Degeneration, and What Causes It?

“…Certain markers of altered cell metabolism, such as increased cytokine and MMP activity, 100,101 could be used as a definition. They are associated with structural defects in the disc, 27 but currently available markers are unable to differentiate degeneration from growth, adap-tive remodeling, and healing.…”