Enhanced expression of tissue inhibitor of metalloproteinases-4 gene in human osteoarthritic synovial membranes and its differential regulation by cytokines in chondrocytes.

OBJECTIVE: Tissue inhibitors of metalloproteinases (TIMPs) are multi-functional proteins with matrix metalloproteinases-inhibiting activities. We studied expression of anti-inflammatory, TIMP-4 gene in human joint tissues and its regulation by arthritis-associated cytokines. RESULTS: TIMP-4 RNA expression originating from synovial fibroblasts was significantly (2.4 fold; p<0.001) elevated in 8 osteoarthritic (OA) versus 7 non-arthritic synovial membranes. Non-arthritic and OA femoral head and knee chondrocytes displayed substantial but variably constitutive expression of the TIMP-4 mRNA. In articular chondrocytes, transforming growth factor beta (TGF-ß1) and oncostatin M (OSM) upregulated TIMP-4 RNA and protein expression while interleukin-1 (IL-1ß) and tumor necrosis factor alpha (TNF-α) did not, suggesting differential regulation by arthritis-associated cytokines. Interleukin 17 (IL-17) mildly induced TIMP-4 mRNA. TGF-ß1 induction of TIMP-4 expression was partly inhibited by ERK pathway and Sp1 transcription factor inhibitors. CONCLUSION: Enhanced TIMP-4 gene expression in OA synovial membranes and cartilage may be due to induction by TGF-ß1, OSM and IL-17, suggesting its pathophysiological role in tissue remodeling in human joints. TGF-ß1 induction of TIMP-4 expression is mediated partly by ERK pathway and Sp1 transcription factor.

Transforming growth factor Beta1 induction of tissue inhibitor of metalloproteinases 3 in articular chondrocytes is mediated by reactive oxygen species.

Transforming growth factor beta1 (TGF-beta1) stimulates cartilage extracellular matrix synthesis but, in excess, evokes synovial inflammation, hyperplasia, and osteophyte formation in arthritic joints. TGF-beta1 induces tissue inhibitor of metalloproteinases 3 (TIMP-3), an inhibitor of cartilage-damaging matrix metalloproteianases and aggrecanases. We investigated the role of reactive oxygen species (ROS) in TIMP-3 induction by TGF-beta1. In primary human and bovine chondrocytes, ROS scavenger and antioxidant N-acetylcysteine (NAC) inhibited TGF-beta1-induced TIMP-3 mRNA and protein increases. Ebselen and ascorbate also reduced this induction. TGF-beta1 time-dependently induced ROS production that was suppressed by NAC. Hydrogen peroxide, a ROS, induced TIMP-3 RNA. The TIMP-3 increase induced by TGF-beta1 was partly Smad2-dependent. TGF-beta1-stimulated Smad2 phosphorylation was inhibited by NAC. Reduced glutathione and L-cysteine also blocked Smad2 and TIMP-3 induction by TGF-beta1, whereas a nonthiol, N-acetylalanine, did not. Smad2 was not activated by H2O2. Smad2 phosphorylation was independent, and TIMP-3 expression was dependent, on new protein synthesis. TGF-beta-stimulated ERK and JNK phosphorylation was also inhibited by NAC. However, inhibitory actions of NAC were not mediated by ERK activation. Thus, ROS mediate TGF-beta1-induced TIMP-3 gene expression. Blocking TGF-beta1-induced gene expression by modulating cellular redox status with thiols can be potentially beneficial for treating arthritic and other disorders caused by excessive TGF-beta1.

Metabolic activity of osteoblasts retrieved from osteoarthritic patients after stimulation with mediators involved in periprosthetic loosening.

OBJECTIVE: To compare the effects of polymethylmetacrylate (PMMA), interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) on osteoarthritic (OA) human osteoblasts (Ob). METHODS: Ob cell cultures were prepared from metaphyseal trabecular bone of OA patients (n=9). Their cellular metabolic activity was characterized by measuring alkaline phosphatase (ALPase), osteocalcin (Oc), osteoprotegerin (OPG), prostaglandin E2 (PGE2), IL-6, macrophage colony-stimulating factor (M-CSF) and soluble receptor activator of NF-kappaB ligand (sRANKL) in supernatants after Ob stimulation with PMMA, IL-1beta, IL-6 or TNF-alpha. RESULTS: IL-6 and PGE2 production by Ob was significantly increased by all mediators used. PMMA and TNF-alpha both stimulated M-CSF and sRANKL production whereas PMMA decreased and TNF-alpha augmented OPG release by Ob. The ratio sRANKL/OPG was significantly increased with PMMA and TNF-alpha, and treatment with anti-IL-6 antibodies did not alter this ratio. ALPase levels remained constant while only PMMA affected Oc production. Subclassification of patients into high or low endogenous producers of IL-6 and PGE2 before stimulation of Ob indicated that the two subgroups maintained similar responses to stimulation by all mediators. CONCLUSION: PMMA and TNF-alpha have comparable dual action on Ob, lowering their anabolic capacity and favoring production of bone resorption activators, an action not mediated by IL-6. This study confirms the important role of PMMA in implant loosening. However, the pertinence of high and low metabolic activities in OA Ob remains unclear, but could be involved in the pathophysiology of bone disease and aseptic loosening.

Induction of matrix metalloproteinase-13 gene expression by TNF-alpha is mediated by MAP kinases, AP-1, and NF-kappaB transcription factors in articular chondrocytes.

Tumor necrosis factor alpha (TNF-alpha), a major proinflammatory cytokine, induces arthritic joint inflammation and resorption of cartilage by matrix metalloproteinase-13 (MMP-13). RNA for MMP-13 is increased in human arthritic femoral cartilage. Mechanisms of this induction were investigated by pretreating primary human osteoarthritic (OA) femoral head chondrocytes or chondrosarcoma cells with the potential inhibitors of TNF-alpha signal transduction and downstream target transcription factors followed by stimulation with TNF-alpha and analysis of MMP-13 RNA/protein. TNF-alpha rapidly activated phosphorylation of extracellular signal-regulated kinases (ERKs), p38, and c-jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases in human chondrocytes. Inhibitors of ERK (U0126, PD98059, and ERK1/2 antisense phosphorothioate oligonucleotide), JNK (SB203580, SP600125, and curcumin), and p38 (SB203580 and SB202190) pathways down-regulated the TNF-stimulated expression of MMP-13. Inhibitors of the transcription factors AP-1 (nordihydroguaiaretic acid, NDGA) and NF-kappaB (curcumin, proteasome inhibitors, and Bay-11-7085) suppressed TNF-alpha-induced MMP-13 expression in primary chondrocytes and SW1353 cells. These results suggest that induction of the MMP-13 gene by TNF-alpha is mediated by ERK, p38, and JNK MAP kinases as well as AP-1 and NF-kappaB transcription factors. Blockade of TNF-alpha signaling and its target transcription factors by the approaches tested here may be beneficial for reducing cartilage breakdown by MMP-13 in arthritis.

Metabolic activity of osteoblasts from periprosthetic trabecular bone in failed total hip arthroplasties and osteoarthritis as markers of osteolysis and loosening.

OBJECTIVE: This study explored whether osteoblast metabolism in trabecular bone of failed total hip replacement (fTHR) in primary osteoarthritis (OA) plays a role in differential failure. METHODS: Osteoblast cell cultures were prepared from metaphyseal trabecular bone of normal individuals, OA patients, OA patients with fTHR with massive cavitary osteolysis (fTHR-O) and without massive cavitary osteolysis (fTHR-NO). Osteoblasts were characterized by measuring osteocalcin, cellular alkaline phosphatase (ALP), and urokinase plasminogen activator (uPA) activity. The cellular metabolic activity was also evaluated by measuring the production of interleukin (IL)-1beta, IL-6, and prostaglandin E2 (PGE2). RESULTS: ALP activity was increased in osteoblasts from patients with OA and fTHR-O compared to normal controls and fTHR-NO. Osteocalcin release was increased only in fTHR-O compared to all other groups. uPA activity was highest in the subgroup of "high metabolic OA" and in fTHR-O, while it was lowest in the subgroup of "low metabolic OA" and in fTHR-NO. IL-6 and PGE2 production was higher in the high metabolic OA and fTHR-O compared to fTHR-NO and low metabolic OA patients. CONCLUSION: Osteoblasts from fTHR-O and a subgroup of OA patients present similarly increased osteoblast markers compared to normal subjects, the low metabolic OA subgroup, and fTHR-NO. This information suggests the differential role of osteoblasts in osteolysis pathophysiology in primary THR surgery. The pertinence of the differential high and low metabolic activities of osteoblasts to the pathophysiology of OA remains to be fully established.

Tissue inhibitor of metalloproteinases-4 (TIMP-4) gene expression is increased in human osteoarthritic femoral head cartilage.

Tissue inhibitor of metalloproteinases-4 (TIMP-4), the newest member of the TIMP family, blocks the activities of several matrix metalloproteinases (MMPs) implicated in the arthritic cartilage erosion. By utilizing semi-quantitative RT-PCR, immunoblotting, and immunohistochemistry, we investigated whether the TIMP-4 gene is expressed in human non-arthritic and osteoarthritic (OA) cartilage. Directly analyzed femoral head cartilage showed TIMP-4 RNA expression in 2 of 9 non-arthritic and 12 of 14 OA patients. Femoral head cartilage from 6 of 9 OA patients had elevated TIMP-4 protein compared to the low-level expression in 3 of 8 non-arthritic controls. In most patients, there was correlation between TIMP-4 RNA and protein expression. TIMP-4 protein was also detected immunohistochemically in the upper zone of OA cartilage. The widespread TIMP-4 RNA and protein expression and augmentation in femoral OA cartilage suggests its important role in joint tissue remodeling and pathogenesis of OA. Increased TIMP levels in arthritic cartilage may not be a sufficiently effective defense against cartilage resorption by excessive multiple MMPs and aggrecanases.