Surface ultrastructure and mechanical propertyof human chondrocyte revealed by atomic force microscopy

Objective: The mechanical properties of chondrocytes influence maintenance of the articular cartilage extracellular matrix. To differentiate the mechanical properties of chondrocytes between a young, normal modulus and an old, osteoarthritic (OA) modulus, we used an atomic force microscope (AFM) to probe the surface ultrastructure and to measure their adhesion force and stiffness. Methods: We directly visualized a single chondrocyte cell by using AFM and quantitatively measured the dimensions of the cells. Results: Profiles displayed heights of 1026 203 and 1668 352 nm for old and young cells, respectively. Contour maps revealed differences in the sizes and structures of the two groups. Mean calculated adhesion forces differed between normal and OA chondrocytes (7.06 +/- 3.35 and 2.97 +/- 1.82 nN, respectively), as did calculated stiffness values (0.0960 +/- 0.009 and 0.0347 +/- 0.005 N/m, respectively). Conclusion: These findings suggested that the mechanical properties of normal chondrocytes substantially differed from those of OA chondrocytes. We believe this study represents the first direct characterization of the surface ultrastructure and mechanical measurements of human chondrocytes between normal and OA stages. This new approach could be a useful technique for investigating age-related changes in the properties of human chondrocytes. (C) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.