The influence of elaborated pericellular matrix on the deformation of isolated articular chondrocytes cultured in agarose.

This study investigates the mechanical influence of pericellular matrix on the deformation of isolated articular chondrocytes compressed within 3% agarose specimens. After 1 day in culture, the cells were associated with minimal amounts of sulphated glycosaminoglycan (GAG) and hydroxyproline and exhibited substantial deformation from a spherical to an oblate ellipsoid morphology when subjected to 20% gross compressive strain. However, over the 6 day culture period, there was a reduction in cell deformation associated with an increase in matrix content. Treatment with testicular hyaluronidase at days 3 and 6 reduced sulphated GAG content to levels observed in untreated specimens at day 1. At day 3, the resulting cell deformation during 20% compression was equivalent to that in specimens compressed at day 1. However, at day 6 cell deformation was only partially restored, suggesting the presence of additional structural matrix components, other than sulphated GAG, which were not present at day 3. Dual scanning confocal microscopy indicated that the elaborated matrix formed a pericellular shell which did not deform during compression and was therefore stiffer than the 3% agarose substrate. Therefore, the elaboration of a mechanically functional pericellular matrix within 6 days, effectively limits the potential involvement of cell deformation in mechanotransduction within cell seeded systems such as those employed for cartilage repair.