Effects of polymethylmethacrylate on rabbit articular chondrocytes in monolayer culture

The effects of polymethylmethacrylate (PMMA) on DNA, protein, and sulfated-proteoglycan synthesis by rabbit articular chondrocytes were observed in monolayer cultures. PMMA pellets in ratios of 1:1 and 1:2 (liquid monomer:powder) significantly reduced [3H]thymidine incorporation into DNA during the first 24 h of culture and less so after 48 and 72 h. The reduction in [3H]thymidine incorporation was restricted to the cohort of chondrocytes nearest the PMMA. Consequently, cellular proliferation was unaltered by PMMA. By contrast, PMMA failed to inhibit [3H]leucine or [3H]serine/35SO4 incorporation. Both control and PMMA (1:1)-treated chondrocyte CsCl density gradient medium fraction dA1 eluted as a retarded peak on Sepharose CL-2B under associative conditions. The average partition coefficient (Kav) of PMMA-treated fraction dA1 was 0.41, as compared with 0.27 for control cultures. The Kav of medium fraction dD1 (proteoglycan monomer) was unaltered. Both control and PMMA-treated dA1 fraction elution profiles on Sepharose CL-2B were altered by incubation with Streptomyces hyaluronidase, indicating the presence of proteoglycan aggregate. The PMMA-treated cultures synthesized smaller proteoglycan aggregates. Since PMMA has been a critical factor in the success of total joint arthroplasty, defining interactions of differentiated cells with the cement is imperative for an understanding of the effects of PMMA on the biology of cartilage and bone.