Effects of hyaluronan on engineered articular cartilage extracellular matrix gene expression in 3-dimensional collagen scaffolds

Hyaluronan (HA) is a component of cartilage matrix with known effects on ch ondrocytes. We tested the effects of adding HA to 3-dimensional (3-D) colla gen sponges on chondrocyte function in vitro. Bovine articular chondrocytes isolated by collagenase digestion were injected into either collagen or HA /collagen scaffolds comprising different amounts of HA (2, 5, 10, and 14% w /w). Expression of aggrecan and type II collagen genes was measured by gene -specific quantitative competitive reverse tanscriptase-polymerase chain re actions, and the extracellular matrix was estimated by histomorphometrical analyses. After 7-day culture, the chondrocytes in 2% (w/w) HA sponges expr essed fourfold more mRNA transcripts for type II collagen (p = 0.002) and t wofold more mRNA transcripts for aggrecan (p = 0.022) than in control colla gen sponges. Furthermore, there was 45% more extracellular matrix in 2% (w/ w) HA sponges and 43% less matrix in the 10% (w/w) HA sponges compared with plain collagen sponges (p > 0.05). In sum, a small amount of HA in 3-D col lagen scaffolds enhanced chondrogenesis, but a greater amount was inhibitor y. This 3-D system represents a novel tool to identify mechanisms by which extracellular matrix molecules influence chondrocyte function. Further, the se results show the potential for modifying scaffolds to improve production of engineered cartilage for in vivo applications. (C) 2000 John Wiley & So ns, Inc.