Biorheology - Volume 45, issue 3-4

Authors: Stoltz, J.F.

Article Type: Other

DOI: 10.3233/BIR-2008-0501

Citation: Biorheology, vol. 45, no. 3-4, pp. 189-189, 2008

Authors: Gratz, Kenneth R. | Wong, Benjamin L. | Bae, Won C. | Sah, Robert L.

Article Type: Research Article

Abstract: Focal damage to articular cartilage is commonly found in symptomatic knees and may contribute to patient discomfort and progressive cartilage degeneration. The objective of this study was to quantify changes in cartilage intra-tissue strain and sliding occurring near a focal defect. Pairs of human osteochondral blocks were compressed by 20% of the total cartilage thicknesses, and tissue deformation was recorded by video microscopy. Then, a single, full-thickness defect was created in one block from each pair, blocks were allowed to re-swell, and the pairs were retested. Stained nuclei, acting as fiducial markers, were tracked by digital image correlation and used …to calculate cartilage strains and surface displacement. With intact samples, axial strain decreased with depth, as is typical of cartilage, and relatively little sliding occurred between surfaces. With defect samples, axial compression of cartilage at the defect rim rose by ~30%, shear in the opposing tissue increased 10-fold to ~0.15, and local sliding was elevated to >50 μm. In vivo, tissue near a defect likely experiences increased overall compression, magnifying these observed in vitro effects. Excessive strains may contribute to cell death, matrix damage, or accelerated wear, and repair efficacy may depend on the ability to alleviate adverse mechanical conditions. Show more

Keywords: Osteoarthritis, biomechanics, cartilage damage, cartilage deformation

DOI: 10.3233/BIR-2008-0475

Citation: Biorheology, vol. 45, no. 3-4, pp. 193-207, 2008

Authors: Scott, John E.

Article Type: Research Article

Abstract: Animal shapes are maintained by connective tissue extracellular matrices (ECMs). ECM shapes depend on keeping collagen fibrils in the right places, held by regular frequent proteoglycan (PG) bridges attached at specific sites. The PGs carry anionic glycosaminoglycan (AGAG) ‘strings’ that span and determine interfibrillar distances, thus holding us together. I called these repeating structures ‘shape modules’. The strings are aggregated antiparallel chains of dermochondan, keratan and chondroitan sulphates (DS, KS and CS); stabilised by hydrophobic and H-bonds. Shape modules are elastic. AGAG/AGAG interactions break under stress and reform when the stress is removed and/or they contain an elastic sugar, L-iduronate …(in DS). Cartilage ECMs are also based on shape modules. Depots therein of aggrecan, the large PG which carries many chains of CS and KS, imbibe water, thereby exerting swelling pressure. External pressure forces this water into the elastic shape modules, from whence it is returned post compression. Cartilage anisotropic responses (along and at right angles to shape module axes) to compressive and tensile stresses are now interpretable. Degradation of shape modules in osteoarthrosis reduces these responses. Inability to hold collagen fibrils together results in imbibition of excess water, fissuring and erosion, characteristic of this condition. Show more

Keywords: Shape modules, collagen fibrils, proteoglycans, decoran, aggrecan, osteoarthrosis

DOI: 10.3233/BIR-2008-0477

Citation: Biorheology, vol. 45, no. 3-4, pp. 209-217, 2008

Authors: Haudenschild, D.R. | D'Lima, D.D. | Lotz, M.K.

Article Type: Research Article

Abstract: The signal transduction mechanisms in chondrocytes that recognize applied forces and elicit the appropriate biochemical cellular responses are not well characterized. A current theory is that the actin cytoskeleton provides an intracellular framework onto which mechanosensation mechanisms are assembled. The actin cytoskeleton is linked to the extracellular matrix at multi-protein complexes called focal adhesions, and evidence exists that focal adhesions mediate the conversion of external physical forces into appropriate biochemical signal transduction events. The Rho GTPases affect the arrangement of actin cytoskeletal structures, and enhance the formation of focal adhesions, which link the cytoskeleton to the extracellular matrix. A …major effector pathway downstream of Rho is the activation of Rho kinase (ROCK), which phosphorylates and activates Lim kinase, which in turn phosphorylates and inhibits the actin-depolymerizing protein cofilin. The objectives of this study were threefold: first, to quantify the actin reorganization in response to dynamic compression of agarose-embedded chondrocytes. Second, to test whether Rho kinase is required for the actin cytoskeletal reorganization induced by dynamic compression. Third, to test whether dynamic compression alters the intracellular localization of Rho kinase and actin remodeling proteins in chondrocytes. Dynamic compression of agarose-embedded chondrocytes induced actin cytoskeletal remodeling causing a significant increase in punctate F-actin structures. Rho kinase activity was required for these cytoskeletal changes. Dynamic compression increased the amount of phosphorylated Rho kinase. The chemokine CCL20 and inducible nitric oxide synthase (iNOS) were the most highly upregulated genes by dynamic compression and this response was reduced by the Rho kinase inhibitors. In conclusion, we show that dynamic compression induces changes in the actin cytoskeleton of agarose-embedded chondrocytes, and we establish methodology to quantify these changes. Furthermore, we show that Rho kinase activity is required for this actin reorganization and gene expression induced by dynamic compression. Show more

Keywords: ROCK, gene expression, LIM kinase, CCL20, NOS2A

DOI: 10.3233/BIR-2008-0499

Citation: Biorheology, vol. 45, no. 3-4, pp. 219-228, 2008

Authors: Akanji, O.O. | Lee, D.A. | Bader, D.A.

Article Type: Research Article

Abstract: Endogenous electrical activity has been detected in articular cartilage. It has previously been suggested that the associated electrical currents and potentials are important to the mechanotransduction processes in cartilage. The present study investigates the effects of direct current on cell proliferation and matrix synthesis, using the well established 3D chondrocyte – agarose model system. Bovine chondrocytes isolated from metacarpalphalangeal joints were seeded in agarose constructs and exposed to a current density of 4 mA/cm2 for 6 h, a magnitude and period which was shown to maintain cell viability. The influence of the optimized electric stimulus was assessed by …protein incorporation and mRNA measurements, using radiolabels and real-time QPCR, respectively. Results indicated no systematic influences of electrical current on protein synthesis, cell proliferation and mRNA expression levels. These data suggest that both the mode of stimulation and the model system are critical for the in vitro modulation of chondrocyte metabolism. Show more

Keywords: Electric stimulation, chondrocyte, proteoglycan, collagen

DOI: 10.3233/BIR-2008-0473

Citation: Biorheology, vol. 45, no. 3-4, pp. 229-243, 2008

Authors: Anghelina, Mirela | Sjostrom, Danen | Perera, Priyangi | Nam, Jin | Knobloch, Thomas | Agarwal, Sudha

Article Type: Research Article

Abstract: Physical therapies and exercise are beneficial not only for physiological recovery in inflamed or injured joints, but also for promoting a homeostatic equilibrium in healthy joints. Human joints provide the pivot points and physiological hinges essential for ambulation and movement to the body, and it is this mobility that in return promotes the health of the joints. But how mobilization regulates the joint microenvironment at the molecular level has remained enigmatic for many years. Recent advances in joint biomechanics and molecular approaches have facilitated an enriched understanding of how joints operate. Consequently, the mechanisms active during joint inflammation that lead …to arthritic conditions, both in vivo in animal models, and in vitro at cell and tissue levels, have become increasingly detailed and defined. These efforts have produced mounting evidences supporting the premise that biomechanical signals play a fundamental role in both the etiopathogenesis of arthritic diseases and in the physiological restoration of joints. This report aims to summarize current peer-reviewed literature and available experimental data to explain how the signals generated by mechanical forces/joint mobilization generate beneficial effects on inflamed articular cartilage, and to propose the basis for using appropriate physical therapies for the optimal benefit to the patient suffering from joint associated injuries. Show more

Keywords: Cartilage, chondrocytes, mechanical strain, NF-κB, signal transduction, inflammation

DOI: 10.3233/BIR-2008-0472

Citation: Biorheology, vol. 45, no. 3-4, pp. 245-256, 2008

Authors: Chowdhury, T.T. | Akanji, O.O. | Salter, D.M. | Bader, D.L. | Lee, D.A.

Article Type: Research Article

Abstract: Interleukin-1β (IL-1β) induces the release of nitric oxide (· NO) and prostaglandin E2 (PGE2 ) by chondrocytes and this effect can be reversed with the application of dynamic compression. Previous studies have indicated that integrins may play a role. In addition, IL-1β upregulates the expression of iNOS and COX-2 mRNA via upstream activation of p38 MAPK. The current study examines the involvement of these pathways in mediating · NO and PGE2 release in IL-1β stimulated bovine chondrocytes subjected to dynamic compression. Bovine chondrocytes were seeded in agarose constructs and cultured with 0 or 10 ng·ml−1 IL-1β …with or without the application of 15% dynamic compressive strain at 1 Hz. Selected inhibitors were used to interrogate the role of α5β1 integrin signalling and p38 MAPK activation in mediating the release of · NO and PGE2 in response to both IL-1β and dynamic compression. The relative expression levels of iNOS and COX-2 were assessed using real-time quantitative PCR. Nitrite, a stable end product of · NO, was measured using the Griess assay and PGE2 release was measured using an enzyme immunoassay. IL-1β enhanced · NO and PGE2 release and this effect was reversed by the application of dynamic compression. Co-incubation with an integrin binding peptide (GRGDSP) abolished the compression-induced effect. Real-time quantitative PCR analysis revealed that IL-1β enhanced iNOS and COX-2 mRNA levels, with the maximum expression at 6 or 12 hours. Dynamic compression reduced this effect via a p38 MAPK sensitive pathway. These results suggest that dynamic compression acts to abrogate of · NO and PGE2 release by directly influencing the expression levels of iNOS and COX-2. Show more

Keywords: P38 MAPK, nitric oxide, PGE_2, mechanotransduction, chondrocyte

DOI: 10.3233/BIR-2008-0474

Citation: Biorheology, vol. 45, no. 3-4, pp. 257-274, 2008

Authors: Holledge, M. Maruo | Millward-Sadler, S.J. | Nuki, G. | Salter, D.M.

Article Type: Research Article

Abstract: The importance of biomechanical forces in regulating normal chondrocyte metabolism is well established and the mechanisms whereby mechanical forces are transduced into biochemical responses by chondrocytes are beginning to be understood. Previous studies have indicated that cyclical mechanical stimulation induces increased aggrecan gene expression in normal but not osteoarthritic chondrocytes in monolayer. It remains unclear, however, whether these effects on gene expression are associated with changes in proteoglycan production and whether any changes in proteoglycan expression is dependent on integrins or integrin associated proteins. Normal and osteoarthritic articular chondrocytes in monolayer were exposed to 0.33 Hz mechanical stimulation for …20 min in the absence or presence of function modifying anti-integrin antibodies. Following stimulation GAG and proteoglycan (PG) synthesis was assessed by DMMB assay and western blotting. Mechanical stimulation of normal chondrocytes resulted in increased GAG synthesis that was blocked by the presence of antibodies to α5 and αVβ5 integrins and CD47. Electrophoretic patterns of PGs released from normal chondrocytes following mechanical stimulation showed an increase in newly-synthesized aggrecan that was not fragmented or degraded. Chondrocytes from osteoarthritic cartilage showed lower levels of GAG production when compared to normal chondrocytes and synthesis was not influenced by mechanical stimulation. These studies show that chondrocytes derived from normal and OA cartilage have different matrix production responses to mechanical stimulation and suggest previously unrecognised roles for αVβ5 integrin in regulation of chondrocyte responses to biomechanical stimulation. Show more

Keywords: GAG, cartilage, CD47, monolayer

DOI: 10.3233/BIR-2008-0476

Citation: Biorheology, vol. 45, no. 3-4, pp. 275-288, 2008

Authors: Nishida, Takashi | Maeda, Azusa | Kubota, Satoshi | Takigawa, Masaharu

Article Type: Research Article

Abstract: Mechanical stress plays an important role in the cartilage metabolism. The aim of this study is to determine the influence of mechanical load magnitude and frequency on cartilage metabolism in terms of the expression of hypertrophic chondrocyte-specific gene product 24/connective tissue growth factor/CCN family 2 (Hcs24/CTGF/CCN2), as an essential mediator of extracellular matrix (ECM) production. When a human chondrocytic cell line, HCS-2/8 was exposed to uni-axial cyclic mechanical force (6% elongation, 10 times/min) only for 30 min, the expression level of Hcs24/CTGF/CCN2 (CCN2) increased, and c-Jun N-terminal protein kinase (JNK) was activated. These findings suggest that stretch-induced CCN2 may be …mediated by the JNK pathway. When HCS-2/8 cells were subjected to cyclic tension force at 15 kPa, 30 cycles/min, which has been reported to be a degradation force for HCS-2/8 cells, the expressions of CCN2 and aggrecan were inhibited, and such expressions remained unchanged in rabbit hyaline costal cartilage cells. However, these expressions increased in rabbit meniscus tissue cells. These findings suggest that the sensitivity of mechanical stretch may be different depending on the type of cells. Furthermore, CCN2 was co-localized with aggrecan in this meniscus tissue region exposed to mechanical stress in vivo. These findings suggest that CCN2 induced by mechanical stress may therefore play some role in meniscus growth and regeneration. Show more

Keywords: Mechanobiology, meniscus cells, chondrocytes, hypertrophic chondrocyte-specific gene product 24/connective tissue growth factor/CCN family 2 (Hcs24/CTGF/CCN2), aggrecan, mechanical stress

DOI: 10.3233/BIR-2008-0478

Citation: Biorheology, vol. 45, no. 3-4, pp. 289-299, 2008

Authors: Gosset, Marjolaine | Berenbaum, Francis | Levy, Arlette | Pigenet, Audrey | Thirion, Sylvie | Cavadias, Simeon | Jacques, Claire

Article Type: Research Article

Abstract: NOTE: Several parts of this article were copied verbatim or close to verbatim from an article that was published in Arthritis Research & Therapy, 2006, 8:R135, doi:10.1186/ar2024. No acknowledgement of, or reference to, the previously published article in Arthritis Research & Therapy was made at the time of publication of the article in Biorheology. In this updated version of the article all the copied parts are highlighted. An Erratum has been published in Biorheology 49(4) (2012), 299. Knee osteoarthritis (OA) results, at least in part, from overloading and inflammation leading to cartilage degradation. Prostaglandin E2 (PGE2 ) …is one of the main catabolic factors involved in OA in which metalloproteinase (MMP) is crucial for cartilage degradation. Its synthesis is the result of cyclooxygenase (COX) and prostaglandin E synthase (PGES) activities whereas NAD+-dependent 15 hydroxy-prostaglandin dehydrogenase (15-PGDH) is the key enzyme implicated in the catabolism of PGE2 . Among the isoforms described, COX-1 and cytosolic PGES are constitutively expressed whereas COX-2 and microsomal PGES type 1 (mPGES-1) are inducible in an inflammatory context. We investigated the regulation of the COX, PGES and 15-PGDH and MMP-2, MMP-9 and MMP-13 genes by mechanical stress applied to cartilage explants. Mouse cartilage explants were subjected to compression (0.5 Hz, 1 MPa) from 2 to 24 h. After determination of the PGE2 release in the media, mRNA and proteins were extracted directly from the cartilage explants and analyzed by real-time RT-PCR and western blot respectively. Mechanical compression of cartilage explants significantly increased PGE2 production in a time dependent manner. This was not due to the synthesis of IL-1, since pretreatment with IL1-Ra did not alter the PGE2 synthesis. Interestingly, COX-2 and mPGES-1 mRNA expression significantly increased after 2 hours, in parallel with protein expression. Moreover, we observed a delayed overexpression of 15-PGDH just before the decline of PGE2 synthesis after 18 hours suggesting that PGE2 synthesis could be altered by the induction of 15-PGDH expression. MAPK are involved in signaling, since specific inhibitors partially inhibited COX-2 and mPGES-1 expressions. Lastly, compression induced MMP-2, -9, -13 mRNA expressions in cartilage. We conclude that dynamic compression induces pro-inflammatroy mediators release and matrix degradating enzymes synthesis. Notably, compression increases mPGES-1 mRNA and protein expression in cartilage explants. Thus, the mechanosensitive mPGES-1 enzyme represents a potential therapeutic target in osteoarthritis. Show more

Keywords: PGE_2, mPGES-1, COX-2, 15-PGDH, MMP, murine cartilage, mechanical stress, osteoarthritis

DOI: 10.3233/BIR-2008-0494

Citation: Biorheology, vol. 45, no. 3-4, pp. 301-320, 2008