Morphology and mechanical function of long-term in vitro engineered cartilage.

Cartilage tissue can be engineered in vitro with articular chondrocytes and poly(glycolic acid) nonwoven scaffolds as previously shown over 12 weeks in vitro. This study addressed whether engineered cartilage would further evolve and approach natural cartilage in extracellular matrix organization and biomechanical properties, especially aggregate modulus through longer term in vitro cultivation. Cellularity, cell size, compressive modulus, and permeability of the in vitro engineered cartilage stabilized within the 12-week cultivation time and remained at the same levels as those of natural cartilage thereafter. The linear range of the stress-strain curve was from 0 to a strain value between 5 and 10% for all the engineered cartilage tissues that were in vitro cultured for longer than 2 weeks, which was the same linear range for natural cartilage. The aggregate modulus further increased from week 12 to week 20 and remained approximately the same value thereafter during a 25-week in vitro cultivation. The aggregate modulus of the engineered cartilage reached 179+/-9 kPa after 20 weeks of in vitro cultivation, which was 40% that of natural articular cartilage. To our knowledge this is the highest aggregate modulus value yet reported of any in vitro engineered cartilage tissue. Copyright 1999 John Wiley & Sons, Inc.