transforming-growth-factor-alpha and Osteoarthritis

Growth-hormones like Insulin-Like-Growth-Hormone-1 (IGF-1) and Tissue-Growth-Factor-beta (TGF-beta) and Cytokines IL-1, IL-6 and TGF-alpha play an important part in the homeostasis and also degradation of the articular cartilage. IL-1 stimulates the production of proteolytic enzymes and inhibits the synthesis of aggrecan and leads therefore to a degradation of the cartilage. TNF-alpha acts in a similar way, whereas the significance of IL-6 for chondrocytes is not yet fully understood. TGF-beta and IGF-1 in contrast have a positive influence on cartilage metabolism, f. ex. TGF-beta stimulates the synthesis of the natural occurring metalloproteinase-inhibitor (TIMP).

Topics: Cartilage, Articular; Cytokines; Glycoproteins; Homeostasis; Humans; Insulin-Like Growth Factor I; Interleukin-1; Interleukin-6; Osteoarthritis; Tissue Inhibitor of Metalloproteinases; Transforming Growth Factor alpha; Transforming Growth Factor beta

Transforming growth factor alpha (TGFα) is a growth factor involved in osteoarthritis (OA). TGFα induces an OA-like phenotype in articular chondrocytes, by inhibiting matrix synthesis and promoting catabolic factor expression. To better understand TGFα's potential as a therapeutic target, we employed two in vivo OA models: (1) post-traumatic and (2) aging related OA. Ten-week old and six-month old male Tgfa null mice and their heterozygous (control) littermates underwent destabilization of the medial meniscus (DMM) surgery. Disease progression was assessed histologically using the Osteoarthritis Research Society International (OARSI) scoring system. As well, spontaneous disease progression was analyzed in eighteen-month-old Tgfa null and heterozygous mice. Ten-week old Tgfa null mice were protected from OA progression at both seven and fourteen weeks post-surgery. No protection was seen however in six-month old null mice after DMM surgery, and no differences were observed between genotypes in the aging model. Thus, young Tgfa null mice are protected from OA progression in the DMM model, while older mice are not. In addition, Tgfa null mice are equally susceptible to spontaneous OA development during aging. Thus, TGFα might be a valuable therapeutic target in some post-traumatic forms of OA, however its role in idiopathic disease is less clear.

Topics: Aging; Animals; Collagen Type II; Disease Models, Animal; Disease Progression; Epitopes; Female; Heterozygote; Male; Matrix Metalloproteinase 13; Menisci, Tibial; Mice, Inbred C57BL; Mice, Knockout; Osteoarthritis; Transforming Growth Factor alpha; Wounds and Injuries

Transforming growth factor α (TGFα) is increased in osteoarthritic (OA) cartilage in rats and humans and modifies chondrocyte phenotype. CCL2 is increased in OA cartilage and stimulates proteoglycan loss. This study was undertaken to test whether TGFα and CCL2 cooperate to promote cartilage degradation and whether inhibiting either reduces disease progression in a rat model of posttraumatic OA.. Microarray analysis was used to profile expression of messenger RNA (mRNA) for Tgfa, Ccl2, and related genes in a rat model of posttraumatic OA. Rat primary chondrocytes and articular cartilage explants were treated with TGFα in the presence or absence of MEK-1/2, p38, phosphatidylinositol 3-kinase, Rho-associated protein kinase, or CCR2 inhibitors and immunostained for markers of cartilage degradation. The rat model was used to administer pharmacologic inhibitors of TGFα (AG1478) and CCL2 (RS504393) signaling for up to 10 weeks and assess histopathology and serum biomarkers of cartilage synthesis (C-propeptide of type II collagen [CPII]) and breakdown (C2C).. Tgfa and Ccl2 mRNA were simultaneously up-regulated in articular cartilage in the rat model of posttraumatic OA. TGFα induced expression of CCL2, Mmp3, and Tnf in primary chondrocytes. Cleavage of type II collagen and aggrecan (by matrix metalloproteinases and ADAMTS-4/5, respectively) induced by TGFα was blocked by pharmacologic inhibition of CCL2 in cartilage explants. In vivo pharmacologic inhibition of TGFα or CCL2 signaling reduced Osteoarthritis Research Society International cartilage histopathology scores and increased serum CPII levels, but only TGFα inhibition reduced C2C levels intreated versus untreated rat OA cartilage.. TGFα signaling stimulates cartilage degradation via a CCL2-dependent mechanism, but pharmacologic inhibition of the TGFα-CCL2 axis reduces experimental posttraumatic OA progression in vivo.

Topics: Animals; Benzoxazines; Cartilage, Articular; Chemokine CCL2; Disease Models, Animal; Disease Progression; Male; Osteoarthritis; Quinazolines; Rats; Rats, Sprague-Dawley; Signal Transduction; Spiro Compounds; Transforming Growth Factor alpha; Tyrphostins; Up-Regulation; Wounds and Injuries

Previously, our lab identified transforming growth factor-alpha (TGFα) as a novel factor involved in osteoarthritis (OA) in a surgical model of the disease. In the same study, we also observed increased transcript levels for endothelin receptor A (ET(A)R), a known contributor to cartilage pathology. To investigate the connection between TGFα and endothelin signaling in OA, primary articular chondrocytes and osteochondral explants were isolated from Sprague-Dawley rats and treated with vehicle or TGFα. Expression of ET(A)R protein and its encoding gene Ednra was assessed. Chondrocytes and cartilage explants were also treated with the endothelin receptor A/B antagonist Bosentan, in order to determine whether TGFα effects could be blocked. TGFα induced expression of ET(A)R protein and its encoding gene Ednra. In primary chondrocyte cultures, Bosentan did not block TGFα responses of the anabolic genes Sox9, Agc1, and Col2a1, but reduced the induction of Mmp13 and Ednra transcripts by TGFα. In osteochondral explants, the inhibitor partially blocked TGFα reduction of type II collagen, as well as induction of MMP-13 and type II collagen neoepitopes. TGFα induces ET(A)R expression in articular chondrocytes and receptor antagonism appears to block some TGFα-induced catabolic effects in a three-dimensional organ culture system. Thus, TGFα may be a therapeutic target upstream of ET(A)R in OA.

Topics: Animals; Antihypertensive Agents; Bosentan; Cartilage, Articular; Cells, Cultured; Extracellular Matrix; Male; NF-kappa B; Nitric Oxide Synthase Type II; Organ Culture Techniques; Osteoarthritis; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Sulfonamides; Transforming Growth Factor alpha

Articular cartilage degeneration is the most consistently observed feature of osteoarthritis (OA). Animal and human studies have shown that various forms of exercise influence the course of the disease in different ways. In addition, early changes in articular cartilage that influence the progression of OA, such as the expression of cytokines, require further investigation. We have used a surgically induced experimental model of knee OA to address these questions. Here, we discuss our recent studies investigating the effects of an exercise paradigm in surgically induced OA, which determined that the destabilized knee joint is susceptible to enhanced degeneration when subjected to low-intensity, low-impact exercise. Further, we investigated early global changes in gene expression in articular chondrocytes from degenerating cartilage. Identified candidate genes including genes involved in chemokine, endothelin, and transforming growth factor-alpha signaling are discussed in the context of articular cartilage degeneration in early OA.

Topics: Animals; Cartilage; Chemokines; Chondrocytes; Cytokines; Disease Models, Animal; Disease Progression; Endothelins; Gene Expression Regulation; Humans; Knee; Knee Joint; Osteoarthritis; Rats; Signal Transduction; Transforming Growth Factor alpha

The potentialities of a new non-invasive optical scanning microscopy technique were evaluated through 3D analysis of chondrocyte-matrix interactions. Five different 2D or 3D culture systems were used: (1) MonoLayer (ML) of human chondrosarcoma cell line; (2) rat or human chondrocytes encapsulated in Alginate Bead (AB); (3) human chondrocytes encapsulated in Alginate Sponge (AS); (4) Rat Femoral Head Cap (RFHC); (5) slices of knee human Osteoarthritic Cartilage (HOAC). Chondrocytes ML, AB, RFHC were incubated for 24 h in vitro in the presence of recombinant human interleukin1-beta (rhIL1-beta) and the effects on cytoskeleton organisation (F-actin filament), Focal Adhesion Kinase (FAK) expression (tyrosine kinase), collagenase B expression (metalloprotease) were studied. Furthermore, the production of intracellular IL1-beta by LPS- or rhIL1-beta-stimulated chondrocytes was shown to be partly suppressed by rhein (active metabolite of diacerhein) in all culture systems. This high resolution light microscopy gave complementary information that could be important for a better understanding of the interaction of chondrocytes with the extracellular matrix in a variety of culture devices.

Topics: Actins; Animals; Cell Culture Techniques; Chondrocytes; Culture Techniques; Cytoskeleton; Extracellular Matrix; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Humans; Integrins; Interleukin-1; Lipopolysaccharides; Matrix Metalloproteinase 9; Microscopy, Confocal; Microspheres; Osteoarthritis; Protein-Tyrosine Kinases; Rats; Recombinant Proteins; Transforming Growth Factor alpha

The immunologic response to prosthetic biomaterial particles is characterized by macrophage-rich inflammatory infiltrate, formation of multinucleated giant cells, and aseptic loosening at the site of arthroplasty. We investigated the in vivo expression and tissue distribution of transforming growth factor alpha, macrophage colony-stimulating factor, and the receptor for colony-stimulating factor-1 at the site of bone erosion in patients with clinically failed orthopaedic implants (n = 30). The expression was further compared with that detected in the inflamed synovial membranes from patients with rheumatoid arthritis or osteoarthritis (n = 15) and one patient with osteoclastoma (giant cell tumour of bone). Immunostaining of the tissue demonstrated positivity for transforming growth factor alpha within the inflammatory macrophage and multinucleated giant cell infiltrate in the diseased synovial membrane and the bone-implant interface. A comparative analysis between the synovium and retrieval interface membranes (pseudosynovium) revealed a high level of expression of transforming growth factor alpha, with intense membrane staining on multinucleated giant cells in all failed arthroplasties with pseudosynovium. In addition, the frequency, antigenic phenotype, and pattern of transforming growth factor alpha expression on multinucleated giant cells in the interface were markedly similar to those observed for multinucleated giant cells in osteoclastoma. Multinucleated giant cells within the interface lacked the expression of macrophage colony-stimulating factor and colony-stimulating factor-1 receptor, whereas those at the bone surfaces exhibited strong immunoreactivity. The predominant expression of transforming growth factor alpha by multinucleated giant cells in the bone-implant interface and its similarity to osteoclastoma highlight the importance of assessing transforming growth factor alpha as a possible contributor to the development of bone-resorbing giant cells at the site of failed orthopaedic implants.

Topics: Arthritis, Rheumatoid; Arthroplasty, Replacement, Hip; Arthroplasty, Replacement, Knee; Bone Neoplasms; Breast Neoplasms; Carcinoma, Ductal, Breast; Fluorescent Antibody Technique, Indirect; Giant Cell Tumor of Bone; Giant Cells; Hip Prosthesis; Humans; Knee Prosthesis; Macrophage Colony-Stimulating Factor; Osteoarthritis; Osteolysis; Receptors, Colony-Stimulating Factor; Synovial Membrane; Transforming Growth Factor alpha