Effects of high molecular weight hyaluronan on chondrocytes cultured within a resorbable gelatin sponge

Freshly isolated bovine articular chondrocytes were seeded into a resorbable gelatin sponge and cultured in the absence or presence of extrinsic high molecular weight hyaluronan (HA) for up to 1 month. The gelatin sponge could be uniformly and reproducibly loaded with chondrocytes. Immunostaining demonstrated that accumulation of pericellular HA increased in the presence of extrinsic HA. However, this approach could not differentiate between extrinsic and endogenous HA. More chondrocytes were retained within the loaded sponges in the presence of HA. Both cell number and matrix synthesis were increased in the presence of high molecular weight HA throughout the time course. Proteoglycan synthesis per cell increased by 22-fold in the presence of HA at 500 microg/mL. Our model demonstrates that HA can be used as a tool not only to expand freshly isolated chondrocyte numbers but also to increase matrix synthesis and deposition within a resorbable gelatin sponge. Autologous chondrocytes for tissue engineering are always in short supply, so this could be a useful tool with which to increase the retention of cells seeded into other types of scaffold matrices before implanting them into a cartilage defect.