Clinical images: Melting candle wax, an uncommon presentation of an uncommon disease

✍ Scribed by P. Auethavekiat; N. S. Murali; N. J. Manek

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 112 KB
• Volume: 50
• Category: Article
• ISSN: 0004-3591
• DOI: 10.1002/art.20614

✦ Synopsis

The matrix metalloproteinase (MMP) family comprises Ͼ20 currently known enzymes that are capable of degrading most extracellular matrix proteins. Kevorkian et al reported interesting findings on expression profiling of MMPs and their inhibitors in cartilage (1). They obtained human cartilage from femoral heads during joint replacement surgery for osteoarthritis (OA) or following fracture to the femoral neck, and assayed gene expression using quantitative real-time polymerase chain reaction (PCR). Their findings demonstrated that among MMPs, expression of the MMP-28/epilysin gene was significantly increased in OA cartilage compared with cartilage from normal femoral heads (P Ͻ 0.001). However, they noted that the role of MMP-28/epilysin in the OA disease process was unknown and that it was difficult to speculate upon this (1).

MMP-28/epilysin, the most recently identified member of the MMP family, was first cloned from human keratinocyte and testis complementary DNA (cDNA) libraries (2) and also from a lung cDNA library (3). Illman et al described the detection of MMP-28/epilysin messenger RNA in a number of mouse tissues, with the highest expression in the lung, placenta, heart, and uterus and lower levels in the testis and gastrointestinal tract. The wide expression of MMP-28/epilysin in intact, healthy tissues suggested that this MMP has a role in physiologic tissue homeostasis and turnover (4). We now provide evidence for high expression of MMP-28/epilysin in cartilage obtained from patients with rheumatoid arthritis (RA) compared with that in cartilage from OA patients or healthy subjects.

We obtained human cartilage from OA and RA patients (n ϭ 5 in each group) who were undergoing total knee replacement, and from femoral heads of patients with femoral neck fracture (n ϭ 5) as controls. OA was diagnosed by physical examination along with radiographic findings, and RA patients had disease that met the 1987 criteria of the American College of Rheumatology (formerly, the American Rheumatism Association) (5). The patients with fracture had no known history of joint disease. All patients provided informed consent.

Cartilage was dissected, and total RNA was directly isolated from cartilage with Isogen (Nippon Gene, Tokyo, Japan) and an RNeasy Mini Kit (Qiagen, Chatsworth, CA). Complementary DNA was synthesized from 1 g of total RNA, using Superscript II and random hexamers (Invitrogen, San Diego, CA), and real-time PCR was performed using the ABI Prism 7900HT sequence detection system and SYBR Green PCR Master Mix in accordance with the protocol suggested by the manufacturer (PE Applied Biosystems, Foster City, CA). The primer sets used were as follows: MMP-28 sense 5Ј-TGACATCCGGCTCACCTTCT-3Ј, antisense 5Ј-ATCAAAGGCATTGCCCAGC-3Ј (PCR product 61 bp in size); G3PDH sense 5Ј-GGGAAGGTGAAGGTCGGA-3Ј, antisense 5Ј-GCAGCCCTGGTGACCAG-3Ј (PCR product 62 bp in size). PCR conditions were as follows: 10 minutes at 95°C, followed by 40 cycles each consisting of 15 seconds at 95°C and 1 minute at 59°C. Values were calculated based on standard curves generated for each gene. Normalization of samples was determined by dividing the number of copies of MMP-28 by the number of copies of G3PDH.

As shown Figure 1, the gene expression of MMP-28/ epilysin was much higher in cartilage from RA patients than in that from OA patients or in normal cartilage. Consistent with the data presented by Kevorkian et al (1), the expression of MMP-28/epilysin was significantly increased in cartilage from patients with OA compared with normal cartilage. Saarialho-Kere U et al suggested that MMP-28/epilysin is implicated in wound repair, being produced by proliferating keratinocytes upon injury to the epidermis (6). Although the physiologic substrates of this MMP have not yet been identified, those authors propose that it may be needed for restructuring of the newly formed basement membrane (6). RA cartilage is usually highly damaged compared with OA cartilage in patients undergoing total knee replacement. Taken together, the findings