COMPOSITION OF CELL-POLYMER CARTILAGE IMPLANTS

Cartilage implants for potential in vivo use for joint repair or recon structive surgery can be created in vitro by growing chondrocytes on b iodegradable polymer scaffolds. Implants 1 cm in diameter by 0.176 cm thick were made using isolated calf chondrocytes and polyglycolic acid (PGA). By 6 weeks, the total amount of glycosaminoglycan (GAG) and co llagen (types I and II) increased to 46% of the implant dry weight; th ere was a corresponding decrease in the mass of PGA. Implant biochemic al and histological compositions depended on initial cell density, sca ffold thickness, and the methods of cell seeding and implant culture. Implants seeded at higher initial cell densities reached higher GAG co ntents (total and per cell), presumably due to cooperative cell-to-cel l interactions. Thicker implants had lower GAG and collagen contents d ue to diffusional limitations. Implants that were seeded and cultured under mixed conditions grew to be thicker and more spatially uniform w ith respect to the distribution of cells, matrix, and remaining polyme r than those seeded and/or cultured statically.Implants from mixed cul tures had a 20-40-mu m thick superficial zone of flat cells and collag en oriented parallel to the surface and a deep zone with perpendicular columns of cells surrounded by GAG, Mixing during cell seeding and cu lture resulted in a more even cell distribution and enhanced nutrient diffusion which could be related to a more favorable biomechanical env ironment for chondrogenesis. Cartilage with appropriate form and funct ion for in vivo implantation can thus be created by selectively stimul ating the growth and differentiated function of chondrocytes (i.e., GA G and collagen synthesis) through optimization of the in vitro culture environment. (C) 1994 John Wiley & Sons, Inc.