Department of Orthopaedic Surgery, Carolinas Medical Center, 1000 Blythe Boulevard, PO Box 32861, Charlotte, NC 28232, USA.
Arthritis Res Ther. 2009;11(6):R184. doi: 10.1186/ar2876. Epub 2009 Dec 9.
The regulation and elevation in expression of the catabolic matrix metalloproteinases (MMPs) is of high importance in the human intervertebral disc since upregulation of these matrix-degrading enzymes results in matrix destruction associated with disc degeneration. MMP28 (epilysin) is a newly discovered MMP believed to play a role in matrix composition and turnover in skin. It is present in basal keratinocytes where its expression is upregulated with wound repair, and in cartilage and synovium where it is upregulated in osteoarthritis. Recent work has shown that mechanical compression can act to modulate expression of MMP28. The expression of MMP28 is unexplored in the intervertebral disc.
Following approval by our human subjects institutional review board, we employed microarray analyses to evaluate in vivo expression of MMP28 and the MMP28 precursor in human disc tissue, and utilized immunohistochemistry to determine cellular and extracellular matrix localization of MMP28 in 35 human disc tissue specimens. The percentage of cells positive for MMP28 immunocytochemical localization was also determined.
The present work documents the expression and presence of MMP28 in cells and extracellular matrix (ECM) of the human intervertebral disc. Gene expression levels in human disc tissue were detectable for both MMP28 and the MMP28 precursor. MMP28 cytoplasmic localization was present in cells of the outer annulus; it was also present in some, but not all, cells of the inner annulus and nucleus. MMP28 was not found in the ECM of healthier Grade I to II discs, but was identified in the ECM of 61% of the more degenerated Grade III to V discs (P = 0.0018). There was a significant difference in cellular MMP28 distribution in the disc (P = 0.008): the outer annulus showed the largest percentage of cells positive for MMP28 immunolocalization, followed by the inner annulus and then the nucleus. Herniated discs showed a significantly greater proportion of MMP28-positive cells compared with nonherniated discs (P = 0.034).
Findings presented here show the first documentation of intervertebral disc expression and production of MMP28. MMP28 was found in both disc cell cytoplasm and in the ECM of more degenerated specimens, with greater cellular localization in the outer annulus and in herniated disc specimens. These findings are important because of the key role of MMPs in disc turnover and homeostasis, and previous indications of a role for this MMP in matrix repair and matrix turnover in other tissues. Our data, which show the presence of MMP28 in human disc tissue, suggest that MMP28 may have a potentially important role in ECM modulation in the healthy and degenerating disc.
在人类椎间盘，细胞外基质金属蛋白酶（MMPs）的调节和表达升高具有重要意义，因为这些基质降解酶的上调会导致与椎间盘退变相关的基质破坏。MMP28（epilysin）是一种新发现的 MMP，被认为在皮肤的基质组成和更新中发挥作用。它存在于基底角质形成细胞中，在伤口修复时其表达上调，在软骨和滑膜中，在骨关节炎中其表达上调。最近的研究表明，机械压缩可以调节 MMP28 的表达。MMP28 在椎间盘中的表达尚不清楚。
在获得我们人类研究对象机构审查委员会的批准后，我们采用微阵列分析来评估 MMP28 和 MMP28 前体在人椎间盘组织中的体内表达，并利用免疫组织化学来确定 MMP28 在 35 个人椎间盘组织标本中的细胞和细胞外基质（ECM）中的定位。还确定了 MMP28 免疫细胞化学定位阳性细胞的百分比。
本研究记录了 MMP28 在人类椎间盘细胞和细胞外基质（ECM）中的表达和存在。人椎间盘组织中可检测到 MMP28 和 MMP28 前体的基因表达水平。MMP28 细胞质定位存在于外环细胞中；它也存在于内环和核的一些细胞中，但不是所有细胞中。在更退变的 III 至 V 级椎间盘的 ECM 中发现了 MMP28，但在健康 I 至 II 级椎间盘的 ECM 中未发现（P = 0.0018）。椎间盘细胞中 MMP28 的分布存在显著差异（P = 0.008）：外环显示出最大百分比的 MMP28 免疫定位阳性细胞，其次是内环，然后是核。疝出的椎间盘与非疝出的椎间盘相比，MMP28 阳性细胞的比例明显更高（P = 0.034）。
这里提出的发现首次证明了 MMP28 在椎间盘的表达和产生。MMP28 存在于椎间盘细胞的细胞质和退变标本的 ECM 中，在外环和疝出的椎间盘标本中细胞定位更大。这些发现很重要，因为 MMPs 在椎间盘更新和平衡中起着关键作用，并且先前有迹象表明该 MMP 在其他组织的基质修复和基质更新中起作用。我们的数据显示 MMP28 存在于人椎间盘组织中，表明 MMP28 可能在健康和退变椎间盘的 ECM 调节中发挥重要作用。
