Influence of gel properties on neocartilage formation by auricular chondrocytes photoencapsulated in hyaluronic acid networks.

The objective of this study was to determine how changes in the network structure and properties of hyaluronic acid (HA) hydrogels, due to variations in the macromer molecular weight (50-1,100 kDa) and macromer concentration (2-20 wt %), affect neocartilage formation by encapsulated auricular chondrocytes. To investigate tissue formation, swine auricular chondrocytes were photoencapsulated in the various networks, implanted subcutaneously in the dorsum of nude mice, and explanted after 6 and 12 weeks for biochemical and histological analysis. After 12 weeks, the various constructs were 81-93% water, contained between 0.1 x 10(6) and 0.6 x 10(6) chondrocytes per sample, and consisted of 0-0.049 microg chondroitin sulfate/mug wet weight (glycosaminoglycan (GAG) content) and 0.002-0.060 microg collagen/microg wet weight. Histological staining showed an even distribution of chondrocytes and GAGs in addition to minimal type I collagen staining and intense and uniform type II collagen staining in the constructs with greatest neocartilage production. Hydrogels fabricated from 2 wt % of the 50 kDa HA macromer most resembled the properties of native cartilage and show the greatest promise for continued development for cartilage regeneration.