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Zone Protein (zone + protein)
Selected AbstractsIncreased accumulation of superficial zone protein (SZP) in articular cartilage in response to bone morphogenetic protein-7 and growth factorsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2007Afshin Khalafi Abstract The purpose of this study was to investigate the role of bone morphogenetic proteins (BMPs), such as BMP-7, growth factors, and cytokines, in the accumulation of superficial zone protein (SZP) in bovine articular cartilage. Calf superficial articular cartilage discs and chondrocytes were obtained for explant and monolayer culture systems, respectively. Dose- and time-dependent actions of BMP-7 on SZP accumulation were investigated in both explant and monolayer culture systems. In addition, actions of various morphogens and growth factors [BMP-2, BMP-4, fibroblast growth factor 2 (FGF-2), insulin-like growth factor 1 (IGF-1), platelet-derived growth factor (PDGF), and transforming growth factor , (TGF-,1)], and cytokines [interleukin (IL)-1,, IL-1,, and tumor necrosis factor (TNF-,)] alone, and in combination with BMP-7, on SZP accumulation were investigated in monolayer culture systems. SZP accumulation was quantified in both the cartilage and the medium using SDS-PAGE and subsequent immunoblotting. In both explant and monolayer cultures, BMP-7 increased SZP accumulation in a dose- and time-dependent fashion (p,<,0.05). Furthermore, SZP accumulation was significantly increased in monolayer cultures by FGF-2, IGF-1, PDGF, and TGF-,1 (p,<,0.05). Both IL-1, and TNF-, significantly reduced SZP accumulation (p,<,0.05). The inhibition of SZP accumulation by TNF-, was partially alleviated by concurrent treatment with BMP-7. The results of this investigation provide novel insights into the role of morphogens, especially BMP-7, growth factors, and cytokines in the accumulation of SZP in articular cartilage. This information has clinical implications because stimulation of SZP may ameliorate the pathology of joint function in arthritis. Furthermore, tissue engineering approaches to articular cartilage may depend on the optimal synthesis and assembly of SZP in the superficial zone to ensure functional tissue architecture. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 2007 [source] The entrapment of corrosion products from CoCr implant alloys in the deposits of calcium phosphate: A comparison of serum, synovial fluid, albumin, EDTA, and waterJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2006A. C. Lewis Abstract Physical wear of orthopedic implants is inevitable. CoCr alloy samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, foetal bovine serum (FBS), synovial fluid, albumin in phosphate-buffered saline (PBS), EDTA in PBS, and water were studied using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The difference in the corrosive nature of human serum, water, albumin in PBS and synovial fluid after 5 days of immersion was highlighted by the oxide layer, which was respectively 15, 3.5, 1.5, and 1.5 nm thick. The thickness of an additional calcium phosphate deposit from human serum and synovial fluid was 40 and 2 nm, respectively. Co and Cr ions migrated from the bulk metal surface and were trapped in this deposit by the phosphate anion. This may account for the composition of wear debris from CoCr orthopedic implants, which is known to consist predominantly of hydroxy-phosphate compounds. Known components of synovial fluid including proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP), have been identified as possible causes for the lack of significant calcium phosphate deposition in this environment. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1587,1596, 2006 [source] Increased friction coefficient and superficial zone protein expression in patients with advanced osteoarthritisARTHRITIS & RHEUMATISM, Issue 9 2010C. P. Neu Objective To quantify the concentration of superficial zone protein (SZP) in the articular cartilage and synovial fluid of patients with advanced osteoarthritis (OA) and to further correlate the SZP content with the friction coefficient, OA severity, and levels of proinflammatory cytokines. Methods Samples of articular cartilage and synovial fluid were obtained from patients undergoing elective total knee replacement surgery. Additional normal samples were obtained from donated body program and tissue bank sources. Regional SZP expression in cartilage obtained from the femoral condyles was quantified by enzyme-linked immunosorbent assay (ELISA) and visualized by immunohistochemistry. Friction coefficient measurements of cartilage plugs slid in the boundary lubrication system were obtained. OA severity was graded using histochemical analyses. The concentrations of SZP and proinflammatory cytokines in synovial fluid were determined by ELISA. Results A pattern of SZP localization in knee cartilage was identified, with load-bearing regions exhibiting high SZP expression. SZP expression patterns were correlated with friction coefficient and OA severity; however, SZP expression was observed in all samples at the articular surface, regardless of OA severity. SZP expression and aspirate volume of synovial fluid were higher in OA patients than in normal controls. Expression of cytokines was elevated in the synovial fluid of some patients. Conclusion Our findings indicate a mechanochemical coupling in which physical forces regulate OA severity and joint lubrication. The findings of this study also suggest that SZP may be ineffective in reducing joint friction in the boundary lubrication mode at an advanced stage of OA, where other mechanisms may dominate the observed tribological behavior. [source] Induction of chondrogenesis from human embryonic stem cells without embryoid body formation by bone morphogenetic protein 7 and transforming growth factor ,1ARTHRITIS & RHEUMATISM, Issue 12 2009Toshiyuki Nakagawa Objective Human embryonic stem cells (ESCs) provide an unlimited supply of pluripotent cells for articular cartilage tissue engineering and regenerative medicine applications. Articular cartilage is an avascular tissue with precise polarity and organization comprising 3 distinct functional zones: surface, middle, and deep. To date, attempts at differentiating human ESCs into articular chondrocytes have been unsuccessful. The majority of studies have focused on chondrogenic (but not specifically articular cartilage) differentiation. Furthermore, previous investigations of induction of chondrogenesis by human ESCs required embryoid body formation; however, embryoid body formation often results in heterogeneous differentiation. The present study was undertaken to determine the in vitro chondrogenic potential of bone morphogenetic protein 7 (BMP-7) and transforming growth factor ,1 (TGF,1),induced human ESC differentiation toward the articular cartilage phenotype. Methods Dissociated single human ESCs were cultured and passaged on a gelatin-coated flask. The human ESCs were cultured as an aggregate in a pellet culture system for 14 days in basal chondrogenic medium (CM), CM with TGF,1, CM with BMP-7, or CM with both TGF,1 and BMP-7. Results The size and wet weight of the cartilage pellets and glycosaminoglycan levels increased, with the smallest, intermediate, and greatest increases, respectively, observed with CM plus TGF,1 treatment, CM plus BMP-7 treatment, and CM plus TGF,1 and BMP-7 treatment (compared with CM treatment alone). The largest size and highest weight of the pellet was in the group in which TGF,1 and BMP-7 were added to the medium. However, expression of the genes for cartilage-specific aggrecan and type II collagen II, as assessed by determination of messenger RNA levels, was highest in the BMP-7,treated group. Superficial zone protein (SZP)/lubricin, a marker of the superficial zone articular chondrocyte, was not detectable under identical culture conditions. Conclusion These results demonstrate an efficient and reproducible model system of human ESC-induced chondrogenesis, using a novel direct plating method in which intervening embryoid body formation does not occur. Further work is needed for optimization of conditions to obtain the articular cartilage phenotype that includes the superficial zone marker as demonstrated by SZP/lubricin synthesis. [source] Prevention of cartilage degeneration in a rat model of osteoarthritis by intraarticular treatment with recombinant lubricinARTHRITIS & RHEUMATISM, Issue 3 2009Carl R. Flannery Objective Lubricin, also referred to as superficial zone protein and PRG4, is a synovial glycoprotein that supplies a friction-resistant, antiadhesive coating to the surfaces of articular cartilage, thereby protecting against arthritis-associated tissue wear and degradation. This study was undertaken to generate and characterize a novel recombinant lubricin protein construct, LUB:1, and to evaluate its therapeutic efficacy following intraarticular delivery in a rat model of osteoarthritis (OA). Methods Binding and localization of LUB:1 to cartilage surfaces was assessed by immunohistochemistry. The cartilage-lubricating properties of LUB:1 were determined using a custom friction testing apparatus. A cell-binding assay was performed to quantify the ability of LUB:1 to prevent cell adhesion. Efficacy studies were conducted in a rat meniscal tear model of OA. One week after the surgical induction of OA, LUB:1 or phosphate buffered saline vehicle was administered by intraarticular injection for 4 weeks, with dosing intervals of either once per week or 3 times per week. OA pathology scores were determined by histologic analysis. Results LUB:1 was shown to bind effectively to cartilage surfaces, and facilitated both cartilage boundary lubrication and inhibition of synovial cell adhesion. Treatment of rat knee joints with LUB:1 resulted in significant disease-modifying, chondroprotective effects during the progression of OA, by markedly reducing cartilage degeneration and structural damage. Conclusion Our findings demonstrate the potential use of recombinant lubricin molecules in novel biotherapeutic approaches to the treatment of OA and associated cartilage abnormalities. [source] Mechanotransduction of bovine articular cartilage superficial zone protein by transforming growth factor , signalingARTHRITIS & RHEUMATISM, Issue 11 2007Corey P. Neu Objective Mechanical signals are key determinants in tissue morphogenesis, maintenance, and restoration strategies in regenerative medicine, although molecular mechanisms of mechanotransduction remain to be elucidated. This study was undertaken to investigate the mechanotransduction process of expression of superficial zone protein (SZP), a critical joint lubricant. Methods Regional expression of SZP was first quantified in cartilage obtained from the femoral condyles of immature bovines, using immunoblotting, and visualized by immunohistochemistry. Contact pressure mapping in whole joints was accomplished using pressure-sensitive film and a load application system for joint testing. Friction measurements on cartilage plugs were acquired under boundary lubrication conditions using a pin-on-disk tribometer modified for reciprocating sliding. Direct mechanical stimulation by shear loading of articular cartilage explants was performed with and without inhibition of transforming growth factor , (TGF,) signaling, and SZP content in media was quantified by enzyme-linked immunosorbent assay. Results An unexpected pattern of SZP localization in knee cartilage was initially identified, with anterior regions exhibiting high levels of SZP expression. Regional SZP patterns were regulated by mechanical signals and correlated with tribological behavior. Direct relationships were demonstrated between high levels of SZP expression, maximum contact pressures, and low friction coefficients. Levels of SZP expression and accumulation were increased by applying shear stress, depending on location within the knee, and were decreased to control levels with the use of a specific inhibitor of TGF, receptor type I kinase and subsequent phospho-Smad2/3 activity. Conclusion These findings indicate a new role for TGF, signaling in the mechanism of cellular mechanotransduction that is especially significant for joint lubrication. [source] ELKS, a protein structurally related to the active zone protein CAST, is involved in Ca2+ -dependent exocytosis from PC12 cellsGENES TO CELLS, Issue 6 2006Eiji Inoue The active zone protein CAST binds directly to the other active zone proteins RIM, Bassoon and Piccolo, and it has been suggested that these protein,protein interactions play an important role in neurotransmitter release. To further elucidate the molecular mechanism, we attempted to examine the function of CAST using PC12 cells as a model system. Although PC12 cells do not express CAST, they do express ELKS, a protein structurally related to CAST. Endogenous and exogenously expressed ELKS, RIM2 and Bassoon were colocalized in punctate signals in PC12 cells. Over-expression of full-length ELKS resulted in a significant increase in stimulated exocytosis of human growth hormone (hGH) from PC12 cells, similar to the effect of full-length RIM2. This increase was not observed following over-expression of deletion constructs of ELKS that lacked either the last three amino acids (IWA) required for binding to RIM2 or a central region necessary for binding to Bassoon. Moreover, over-expression of the NH2 -terminal RIM2-binding domain of Munc13-1, which is known to inhibit the binding between RIM and Munc13-1, inhibited the stimulated increase in hGH secretion by full-length RIM2. Furthermore, this construct also inhibited the stimulated increase in hGH secretion induced by full-length ELKS. These results suggest that ELKS is involved in Ca2+ -dependent exocytosis from PC12 cells at least partly via the RIM2-Munc13-1 pathway. [source] | ||||||||||