The goal of this study was to compare expression of chondrocyte-associated antigen (CAA) and cartilage matrix molecules in 2-D (monolayer) and 3-D (Matrigel) culture. Chondrocytes isolated from the cartilage of 3-day-old rats were expanded in monolayer culture for 28 days. CAA expression gradually decreased and was not detected beyond the 96th hour of monolayer culture. Collagen type II and aggrecan mRNA levels decreased during culture. The collagen type I mRNA level increased during the first week and remained high. The increase in the versican mRNA level was less pronounced during the first week and declined slightly after further cultivation. Freshly isolated chondrocytes introduced into Matrigel still expressed CAA after 7 days. Moreover, CAA expression returned in chondrocytes re-cultured in Matrigel after 7 days in monolayer. Similarly, the increase in the mRNA levels of collagen type II and aggrecan in Matrigel was limited to freshly isolated chondrocytes and to those that remained in monolayer for 1 week. Collagen type I mRNA in monolayer and Matrigel cultures of freshly isolated chondrocytes was at a similar level. The introduction of freshly isolated or 7-day monolayer-cultured chondrocytes into Matrigel caused a decrease in the versican mRNA level in comparison with 7- and 14-day 2-D cultures, respectively. On the other hand, chondrocytes seeded in Matrigel after 14 days of monolayer culture did not express CAA, showed decreased levels of collagen type II and aggrecan mRNA and an increase in versican mRNA. In conclusion, it appears that changes in the expression of CAA in 2- and 3-D cultures occur in parallel to changes in typical cartilage matrix molecule expression.

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