Biomedical subjects

Marc Fajardo

Publications and source records attributed to Marc Fajardo.

3 recordsLinked to original sources

PubMed2006

ADAMTS-7: a metalloproteinase that directly binds to and degrades cartilage oligomeric matrix protein.

Degradative fragments of cartilage oligomeric matrix protein (COMP) have been observed in arthritic patients. The physiological enzyme(s) that degrade COMP, however, remain unknown. We performed a yeast two-hybrid screen (Y2H) to search for proteins that associate with COMP to identify an interaction partner that might degrade it. One screen using the epidermal growth factor (EGF) domain of COMP as bait led to the discovery of ADAMTS-7. Rat ADAMTS-7 is composed of 1595 amino acids, and this protein exhibits higher expression in the musculoskeletal tissues. COMP binds directly to ADAMTS-7 in vitro and in native articular cartilage. ADAMTS-7 selectively interacts with the EGF repeat domain but not with the other three functional domains of COMP, whereas the four C-terminal TSP motifs of ADAMTS-7 are required and sufficient for association with COMP. The recombinant catalytic domain and intact ADAMTS-7 are capable of digesting COMP in vitro. The enzymatic activity of ADAMTS-7 requires the presence of Zn2+ and appropriate pH (7.5-9.5), and the concentration of ADAMTS-7 in cartilage and synovium of patients with rheumatoid arthritis is significantly increased as compared to normal cartilage and synovium. ADAMTS-7 is the first metalloproteinase found to bind directly to and degrade COMP.

ADAM Proteins↗

PubMed2005

Disease-modifying therapies for osteoarthritis : current status.

Osteoarthritis, the most common form of arthritis, is a debilitating progressive disease principally affecting the elderly. Osteoarthritis therapy has evolved in the past few decades from symptomatic treatment to possible disease-modifying solutions. In this paper, the pathophysiology of osteoarthritis is first reviewed, including an examination of the mechanisms underlying osteoarthritis and discussions of the roles of cartilage, synovial fluid and subchondral bone. The remainder of the paper discusses therapeutic approaches in current use and those in development, with special attention given to pharmacological treatments. Current approaches to treating osteoarthritis--i.e. medications; nonpharmacological modalities, such as physical therapy, exercise, weight management and orthotics; and (as a last resort) surgery--focus on reducing pain and improving (or at least maintaining) mobility. Drugs currently used to treat osteoarthritis fall into several categories: analgesics, NSAIDs, cyclo-oxygenase-2 (COX-2) inhibitors, corticosteroids, viscosupplementation, and symptomatic slow-acting drugs ('nutraceuticals'). The analgesics (paracetamol [acetaminophen] and opiates) have demonstrated less symptomatic efficacy than NSAIDs, while the latter have displayed mixed results in terms of joint space narrowing. COX-2 inhibitors have been demonstrated to be equal to or superior to NSAIDs in effectiveness. However, once considered a safer alternative, COX-2 inhibitors have become the subject of intense scrutiny since recent clinical evidence has cast suspicion on their cardiovascular safety profile. Injectable therapies, such as corticosteroids and viscosupplementation have elicited favorable short-term response but no long-term structural modification. On the other hand, the slow-acting drugs, especially chondroitin and glucosamine sulfate, have shown promising results. Also reviewed are other established and experimental therapies that seek to modify and/or even reverse the course of osteoarthritis. These include such medications as colchicine, bisphosphonates and hormones; dietary therapeutics, such as ginger extract and green tea; and such truly experimental treatments as matrix metalloproteinase inhibitors, cytokines, nitric oxide, growth factors and gene therapy. Osteoarthritis continues to be a difficult disorder to treat, as there is no cure as such and current treatments focus mainly on relieving pain and maintaining joint function. The search nevertheless continues for management regimens that can slow, alter or reverse the degenerative processes of osteoarthritis.

Aged↗

PubMed2004

Leukemia/lymphoma-related factor, a POZ domain-containing transcriptional repressor, interacts with histone deacetylase-1 and inhibits cartilage oligomeric matrix protein gene expression and chondrogenesis.

Mutations in the human cartilage oligomeric matrix protein (COMP) gene have been linked to the development of pseudoachondroplasia and multiple epiphyseal dysplasia. We previously cloned the promoter region of the COMP gene and delineated a minimal negative regulatory element (NRE) that is both necessary and sufficient to repress its promoter (Issack, P. S., Fang, C. H., Leslie, M. P., and Di Cesare, P. E. (2000) J. Orthop. Res. 18, 345-350; Issack, P. S., Liu, C. J., Prazak, L., and Di Cesare, P. E. (2004) J. Orthop. Res. 22, 751-758). In this study, a yeast one-hybrid screen for proteins that associate with the NRE led to the identification of the leukemia/lymphoma-related factor (LRF), a transcriptional repressor that contains a POZ (poxvirus zinc finger) domain, as an NRE-binding protein. LRF bound directly to the NRE both in vitro and in living cells. Nine nucleotides (GAGGGTCCC) in the 30-bp NRE are essential for binding to LRF. LRF showed dose-dependent inhibition of COMP-specific reporter gene activity, and exogenous overexpression of LRF repressed COMP gene expression in both rat chondrosarcoma cells and bone morphogenetic protein-2-treated C3H10T1/2 progenitor cells. In addition, LRF also inhibited bone morphogenetic protein-2-induced chondrogenesis in high density micromass cultures of C3H10T1/2 cells, as evidenced by lack of expression of other chondrocytic markers, such as aggrecan and collagen types II, IX, X, and XI, and by Alcian blue staining. LRF associated with histone deacetylase-1 (HDAC1), and experiments utilizing the HDAC inhibitor trichostatin A revealed that LRF-mediated repression requires deacetylase activity. LRF is the first transcription factor found to bind directly to the COMP gene promoter, to recruit HDAC1, and to regulate both COMP gene expression and chondrogenic differentiation.

Alcian Blue↗