Heterogeneous nanostructural and nanoelastic properties of pericellular and interterritorial matrices of chondrocytes by atomic force microscopy

Hyaline cartilage consists of sparse chondrocytes and abundant extracellular matrix. There is a paucity of experimental data in support of the notion of conceivable regional differences in the mechanical properties of chondral matrices. Upon visual differentiation of the pericellular and interterritorial matrices in each of 19 fresh growth plate samples with toluidine blue and alizarin red labels, nanoindentation was applied separately to the pericellular matrix and interterritorial matrix to using fluid-phase atomic force microscopy and real-time imaging. The interterritorial matrix demonstrated elongated parallel ridges, whereas the pericellular matrix showed irregular, short-range elevations with characteristic pores and canals. Analysis of surface contours at 600nm(2) scan size revealed that the interterritorial matrix had significantly greater surface roughness (71+/-18nm; mean+/-SE) than the pericellular matrix (24+/-4nm) ( P< 0.001). The average Young's modulus of the interterritorial matrix was 636+/-123 (kPa), significantly greater than the pericellular matrix (265+/-53kPa) (P< 0.001 ). Thus, the interterritorial matrix appears to possess not only distinct microtopographic contours in comparison with the pericellular matrix, but also significantly greater mechanical stiffness. These distinctive nanostructural and nanomechanical properties may have implications in nutrient diffusion and fluid dynamics, both of which are of vital importance for cartilage health and function.