Maintenance and Acceleration of Pericellular Matrix Formation within 3D Cartilage Cell Culture Models

Objective: In native articular cartilage, chondrocytes are surrounded by a thin pericellular matrix (PCM) forming chondrons. The PCM is exclusively rich in type VI collagen. The retention of the PCM has a significant influence on the metabolic activity of the chondrocytes. Design This study investigated the influence of 2 hydrogels (hyaluronic acid [HA] and agarose) and 2 media compositions (basal and chondrogenic) on the preservation/maintenance and acceleration of PCM formation over a 21-day time course. Different combinations of chondrocytes, chondrons, and mesenchymal stem cells (MSCs) were studied. Results: Both hydrogels preserved chondrons PCM from day 1 up to 21-day culture regardless of media composition. Type VI collagen immunostaining of the cultured chondrons appeared both dense and homogenous. The presence of MSCs did not influence this outcome. At day 1, type VI collagen was not present around chondrocytes alone or their co-culture with MSCs. In the HA hydrogel, type VI collagen was located within the PCM after 7 days in both mono- and co-cultures. In the agarose hydrogel, collagen VI was located within the PCM at 7 days (co-cultures) and 14 days (monocultures). In both hydrogel systems, chondrogenic media enhanced the production of key extracellular matrix components in both mono- and co-cultures in comparison to basal media (11.5% and 14% more in glycosaminoglycans and type II collagen for chondrocytes samples at day 21 culture samples, respectively). However, the media types did not enhance type VI collagen synthesis. Conclusion: Altogether, a 3D chondrogenic hydrogel environment is the primary condition for maintenance and acceleration of PCM formation.

Automated summary

Both hyaluronic acid and agarose hydrogels preserved the pericellular matrix of chondrons over a 21-day culture period, with type VI collagen appearing dense and homogeneous. The presence of mesenchymal stem cells did not influence this outcome. Chondrogenic media enhanced the production of key extracellular matrix components, but did not enhance type VI collagen synthesis, suggesting that a 3D chondrogenic hydrogel environment is crucial for pericellular matrix formation.