Biorheology - Volume 39, issue 1-2

Article Type: Research Article

Citation: Biorheology, vol. 39, no. 1-2, pp. 1-1, 2002

Authors: Stoltz, J.‐F. | Wang, X.

Article Type: Research Article

Abstract: Biomechanics can be defined as the application of mechanical concepts to the living world, and various fields of research have been developed such as the mechanics of movement, ergonomics, the mechanical properties of cells and tissues, and the relationship between physiology and applied forces. In this paper, the authors give, through several examples, an outline of these approaches and their potential biomedical applications, as in tissue remodelling, cell and tissue engineering and the development of biotissues.

Keywords: Mechanobiology, biomechanics, stress, cell, tissue, remodelling

Citation: Biorheology, vol. 39, no. 1-2, pp. 5-10, 2002

Authors: Wang, Christopher C.‐B. | Guo, X. Edward | Sun, Dongning | Mow, Van C. | Ateshian, Gerard A. | Hung, Clark T.

Article Type: Research Article

Abstract: A non‐invasive methodology (based on video microscopy, optimized digital image correlation and thin plate spline smoothing technique) has been developed to determine the intrinsic tissue stiffness (Ha ) and the intrinsic fixed charge density (c0 F ) distribution for hydrated soft tissues such as articular cartilage. Using this technique, the depth‐dependent inhomogeneous parameters Ha (z) and c0 F (z) were determined for young bovine cartilage and incorporated into a triphasic mixture model. This model was then used to predict the mechanical and electrochemical events (stress, strain, fluid/osmotic pressure, and electrical potentials) inside the tissue specimen under a confined compression stress …relaxation test. The integration of experimental measurements with theoretical analyses can help to understand the unique material behaviors of articular cartilage. Coupled with biological assays of cell‐scale biosynthesis, there is also a great potential in the future to study chondrocyte mechanotransduction in situ with a new level of specificity. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 11-25, 2002

Authors: Quinn, T.M. | Schmid, P. | Hunziker, E.B. | Grodzinsky, A.J.

Article Type: Research Article

Abstract: With a view towards the development of methods for cartilage tissue engineering, matrix deposition around individual chondrocytes was studied during de novo matrix synthesis in agarose suspension culture. At a range of times in culture from 2 days to 1 month (long enough for cartilage‐like material properties to begin to emerge), pericellular distributions of proteoglycan and matrix protein deposition were measured by quantitative autoradiography, while matrix accumulation and cell volumes were estimated by stereological methods. Consistent with previous work, tissue‐average rates of matrix synthesis generally decreased asymptotically with time in culture, as de novo matrix accumulated. Cell‐scale analysis revealed that …this evolution was accompanied by a transition from predominantly pericellular matrix (within a few μm from the cell membrane) deposition early in culture towards proteoglycan and protein deposition patterns more similar to those observed in cartilage explants at later times. This finding may suggest a differential recruitment of different proteoglycan metabolic pools as matrix assembly progresses. Cell volumes increased with time in culture, suggestive of alterations in volume regulatory processes associated with changes in the microphysical environment. Results emphasize a pattern of de novo matrix construction which proceeds outward from the pericellular matrix in a progressive fashion. These findings provide cell‐scale insight into the mechanisms of assembly of matrix proteins and proteoglycans in de novo matrix, and may aid in the development of tissue engineering methods for cartilage repair. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 27-37, 2002

Authors: Lai, W.M. | Sun, D.D. | Ateshian, G.A. | Guo, X.E. | Mow, V.C.

Article Type: Research Article

Abstract: An important step toward understanding signal transduction mechanisms modulating cellular activities is the accurate predictions of the mechanical and electro‐chemical environment of the cells in well‐defined experimental configurations. Although electro‐kinetic phenomena in cartilage are well known, few studies have focused on the electric field inside the tissue. In this paper, we present some of our recent calculations of the electric field inside a layer of cartilage (with and without cells) in an open circuit one‐dimensional (1D) stress relaxation experiment. The electric field inside the tissue derives from the streaming effects (streaming potential) and the diffusion effect (diffusion potential). Our results …show that, for realistic cartilage material parameters, due to deformation‐induced inhomogeneity of the fixed charge density, the two potentials compete against each other. For softer tissue, the diffusion potential may dominate over the streaming potential and vice versa for stiffer tissue. These results demonstrate that for proper interpretation of the mechano‐electrochemical signal transduction mechanisms, one must not ignore the diffusion potential. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 39-45, 2002

Authors: Huyghe, J.M. | Janssen, C.F. | van Donkelaar, C.C. | Lanir, Y.

Article Type: Research Article

Abstract: The frictional properties of cartilaginous tissues, such as the hydraulic permeability, the electro‐osmotic permeability, the diffusion coefficients of various ions and solutes, and the electrical conductance, are vital data to characterise the extracellular environment in which chondrocytes reside. This paper analyses one‐dimensional measurement principles of these coefficients. Particular attention is given to the deformation dependence of them and the highly deformable nature of the tissues. A suggested strategy is the combination of a diffusion experiment using radiotracer methods, an electro‐osmotic flow experiment and an electro‐osmotic pressure experiment at low electric current.

Citation: Biorheology, vol. 39, no. 1-2, pp. 47-53, 2002

Authors: Wohlrab, David | Lebek, Susanne | Krüger, Thomas | Reichel, Heiko

Article Type: Research Article

Abstract: The goal of the study was to examine connections between ion channel activity and the proliferation of human chondrocytes. Chondrocytes were isolated form human osteoarthritic knee joint cartilage. In this study the concentration‐dependent influence of the ion channel modulators tetraethylammonium (TEA), 4‐aminopyridine (4‐AP), 4′ ,4′ diisothiocyanato‐stilbene‐2,2′ ‐disulfonic acid (DIDS), 4‐acetamido‐4′ ‐isothiocyano‐2,2′ ‐disulfonic acid stilbene (SITS), verapamil (vp) and lidocaine (lido) on the membrane potential and the proliferation of human chondrocytes was investigated using flow cytometry and the measurement of 3 H‐thymidine incorporation as measure for the cell proliferation. The results show an effect of the used ion channel modulators …causing a change of the membrane potential of human chondrocytes. The maximal measurable effects of the membrane potential were listed with 0.25 mmol/l verapamil (−18%) and 0.1 mmol/l lidocaine (+20%). When measuring DNA distribution, it became apparent that the human chondrocytes are diploid cells with a very low proliferation tendency. After 12 days culture duration, lidocaine and 4‐AP cause an increase of the DNA synthesis rate being a limited effect. These results allow the conclusion of an influence of ion channel modulators on chondrocyte proliferation. To gain knowledge of the regulation of chondrocyte proliferation via ion channel modulators could serve the research of new osteoarthritis treatment concepts. Show more

Keywords: Chondrocytes, ion channel modulators, membrane potential, proliferation

Citation: Biorheology, vol. 39, no. 1-2, pp. 55-61, 2002

Authors: Volokh, K.Yu. | Vilnay, O. | Belsky, M.

Article Type: Research Article

Abstract: The role of tensegrity architecture of the cytoskeleton in the mechanical behavior of living cells is examined by computational studies. Plane and spatial tensegrity models of the cytoskeleton are considered as well as their non‐tensegrity counterparts. Local buckling including deep postbuckling response of the compressed microtubules of the cytoskeleton is considered. The tensioned microfilaments cannot sustain compression. Large deformation of the whole model is accounted and fully nonlinear analysis is performed. It is shown that in the case of local buckling of the microtubules non‐tensegrity models exhibit qualitatively the same linear stiffening as their tensegrity counterparts. This result raises the …question of experimental validation of the local buckling of microtubules. If the microtubules of real cells are not straight, then tensegrity (in a narrow sense) is not a necessary attribute of the cytoskeleton architecture. If the microtubules are straight then tensegrity is more likely to be the cytoskeletal architecture. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 63-67, 2002

Authors: Bader, D.L. | Ohashi, T. | Knight, M.M. | Lee, D.A. | Sato, M.

Article Type: Research Article

Abstract: This paper presents a series of techniques, which examine the deformation characteristics of bovine articular chondrocytes. The direct contact approach employs well established methodology, involving AFM and micropipette aspiration, to yield structural properties of local regions of isolated chondrocytes. The former technique yields a non‐linear response with increased structural stiffness in a central location on a projected image of the chondrocyte. A simple viscoelastic model can be used with data from the micropipette aspiration technique to yield a mean value of Young's modulus, which is similar to that recently reported (Jones et al., 1999). An indirect approach is also described, …involving the response of chondrocytes seeded within compressed agarose constructs. For 1% agarose constructs, the resulting cell strain, yields a gross cell modulus of 2.7 kPa. The study highlights the difficulties in establishing unique mechanical parameters, which reflect the deformation behaviour of articular chondrocytes. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 69-78, 2002

Authors: Hunter, Christopher J. | Levenston, Marc E.

Article Type: Research Article

Abstract: This study examined the effects of mechanical compression on engineered cartilage in a novel hybrid culture system. Cylindrical holes were cut in discs of bovine articular cartilage and filled with agarose gels containing chondrocytes. These constructs were compressed in radiolabeled medium under static or oscillatory unconfined compression. Oscillatory compression at 1 Hz significantly stimulated synthesis above static control levels. Control experiments indicate that oscillatory compression does not stimulate freshly cast gels (without annuli), but does so after several weeks. This may be because physiologic fluid flow levels do not occur until sufficient extracellular matrix has accumulated. Finite element models predict …minimal fluid flow in the gel core, and minimal differences in flow patterns between free and constrained gels. However, the models predict fluid pressures in constrained gels to be substantially higher than those in free gels. Our results suggest that pressure variations may influence synthesis of engineered cartilage matrices, with implications for construct development and post‐implantation survival. Show more

Citation: Biorheology, vol. 39, no. 1-2, pp. 79-88, 2002