Role of cell-associated matrix in the development of free-swelling and dynamically loaded chondrocyte-seeded agarose gels

Chondrocytes embedded in agarose and subjected to dynamic deformational loading produce a functional matrix with time in culture, but there is usually a delay in the development of significant differences compared to free swelling. In this study, we hypothesized that the initial presence of a cell-associated matrix would expedite construct development in response to dynamic deformational loading. Seeded samples with enzymatically isolated chondrocytes and chondrons (the chondrocyte and its pericellular matrix) and examined the effects of seeding density and dynamic loading on the development of tissue properties. At 60 million/ml, dynamic loading significantly augmented the development of material properties in chondrocyte- and chondron-seeded constructs. Biochemical content and histological analysis indicated that the deposition of GAG, link protein and collagens are affected by the pre-existing cell-associated matrix of the chondron-seeded samples. The pericellular matrix associated with the chondrons did not expedite the development of material properties in response to deformational loading, disproving our hypothesis. The relative concentration and distribution of matrix proteins may play a major role in the disparate responses observed for the chondrocyte- and chondron-seeded cultures. In further support of these findings, culturing chondrocytes in agarose for two weeks prior to the application of deformational loading also did not exhibit expedited construct development.