TY - JOUR
T1 - Determination of the Poisson's ratio of the cell
T2 - Recovery properties of chondrocytes after release from complete micropipette aspiration
AU - Trickey, Wendy R.
AU - Baaijens, Frank P.T.
AU - Laursen, Tod A.
AU - Alexopoulos, Leonidas G.
AU - Guilak, Farshid
N1 - Funding Information:
This study was supported by grants from the National Science Foundation #DGE-9616283, the National Institutes of Health #AR50245, #AR48182, and #AG15768, and the Eindhoven University of Technology.
PY - 2006
Y1 - 2006
N2 - Chondrocytes in articular cartilage are regularly subjected to compression and recovery due to dynamic loading of the joint. Previous studies have investigated the elastic and viscoelastic properties of chondrocytes using micropipette aspiration techniques, but in order to calculate cell properties, these studies have generally assumed that cells are incompressible with a Poisson's ratio of 0.5. The goal of this study was to measure the Poisson's ratio and recovery properties of the chondrocyte by combining theoretical modeling with experimental measures of complete cellular aspiration and release from a micropipette. Chondrocytes isolated from non-osteoarthritic and osteoarthritic cartilage were fully aspirated into a micropipette and allowed to reach mechanical equilibrium. Cells were then extruded from the micropipette and cell volume and morphology were measured throughout the experiment. This experimental procedure was simulated with finite element analysis, modeling the chondrocyte as either a compressible two-mode viscoelastic solid, or as a biphasic viscoelastic material. By fitting the experimental data to the theoretically predicted cell response, the Poisson's ratio and the viscoelastic recovery properties of the cell were determined. The Poisson's ratio of chondrocytes was found to be 0.38 for non-osteoarthritic cartilage and 0.36 for osteoarthritic chondrocytes (no significant difference). Osteoarthritic chondrocytes showed an increased recovery time following full aspiration. In contrast to previous assumptions, these findings suggest that chondrocytes are compressible, consistent with previous studies showing cell volume changes with compression of the extracellular matrix.
AB - Chondrocytes in articular cartilage are regularly subjected to compression and recovery due to dynamic loading of the joint. Previous studies have investigated the elastic and viscoelastic properties of chondrocytes using micropipette aspiration techniques, but in order to calculate cell properties, these studies have generally assumed that cells are incompressible with a Poisson's ratio of 0.5. The goal of this study was to measure the Poisson's ratio and recovery properties of the chondrocyte by combining theoretical modeling with experimental measures of complete cellular aspiration and release from a micropipette. Chondrocytes isolated from non-osteoarthritic and osteoarthritic cartilage were fully aspirated into a micropipette and allowed to reach mechanical equilibrium. Cells were then extruded from the micropipette and cell volume and morphology were measured throughout the experiment. This experimental procedure was simulated with finite element analysis, modeling the chondrocyte as either a compressible two-mode viscoelastic solid, or as a biphasic viscoelastic material. By fitting the experimental data to the theoretically predicted cell response, the Poisson's ratio and the viscoelastic recovery properties of the cell were determined. The Poisson's ratio of chondrocytes was found to be 0.38 for non-osteoarthritic cartilage and 0.36 for osteoarthritic chondrocytes (no significant difference). Osteoarthritic chondrocytes showed an increased recovery time following full aspiration. In contrast to previous assumptions, these findings suggest that chondrocytes are compressible, consistent with previous studies showing cell volume changes with compression of the extracellular matrix.
KW - Arthritis
KW - Biphasic
KW - Cartilage
KW - Cell mechanics
KW - Nucleus
KW - Osteoarthritis
KW - Viscoelastic
UR - http://www.scopus.com/inward/record.url?scp=27744502570&partnerID=8YFLogxK
U2 - 10.1016/j.jbiomech.2004.11.006
DO - 10.1016/j.jbiomech.2004.11.006
M3 - Article
C2 - 16271590
AN - SCOPUS:27744502570
SN - 0021-9290
VL - 39
SP - 78
EP - 87
JO - Journal of Biomechanics
JF - Journal of Biomechanics
IS - 1
ER -