CULTURE SURFACES COATED WITH VARIOUS IMPLANT MATERIALS AFFECT CHONDROCYTE GROWTH AND METABOLISM

The effect on chondrocyte metabolism of culture surfaces sputter-coate d with various materials used for orthopaedic implants was studied and correlated with the stage of cartilage cell maturation. Confluent, fo urth-passage chondrocytes from the costochondral resting zone and grow th zone of rats were cultured for 6 or 9 days on 24-well plates sputte r-coated with ultrathin films of titanium, titanium dioxide, aluminum oxide, zirconium oxide, and calcium phosphate (1.67:1). Corona-dischar ged tissue culture plastic served as the control. The effect of surfac e material was examined with regard to cell morphology; cell prolifera tion (cell number) and DNA synthesis ([H-3]thymidine incorporation); R NA synthesis ([H-3] uridine incorporation); collagenase-digestible pro tein, noncollagenase-digestible protein, and percentage of collagen pr oduction; and alkaline phosphatase-specific activity, both in the cell layer and in trypsinized chondrocytes. Cell morphology was dependent on surface material; only cells cultured on titanium had an appearance similar to that of cells cultured on plastic. While titanium or titan ium dioxide surfaces had no effect on cell number or [H-3]thymidine in corporation, aluminum oxide, calcium phosphate, and zirconium oxide su rfaces inhibited both parameters. Cells cultured on aluminum oxide, ca lcium phosphate, zirconium oxide, and titanium dioxide exhibited decre ased collagenase-digestible protein, noncollagenase-digestible protein , and percentage of collagen production, but [H-3]uridine incorporatio n was decreased only in those chondrocytes cultured on aluminum oxide, calcium phosphate, or zirconium oxide. Chondrocytes cultured on titan ium had greater alkaline phosphatase-specific activity than did cells cultured on plastic, but the incorporation of [H-3]uridine and product ion of collagenase-digestible protein, noncollagenase-digestible prote in, and percentage of collagen was comparable. The response of chrondr ocytes from the growth zone and resting zone to culture surface was co mparable, differing primarily in magnitude. Cell maturation-dependent effects were evident when enzyme activity in trypsinized and scraped c ells was compared. These results indicate that different surface mater ials affect chondrocyte metabolism and phenotypic expression in vitro and suggest that implant materials may modulate the phenotypic express ion of cells in vivo.