Bioactive glass serves as a substrate for maintenance of phenotype of nucleus pulposus cells of the intervertebral disc

The objective of the study was to investigate the capability of bioactive g lass 45S5 to serve as a substrate for nucleus pulposus cells in vitro. Nucl eus pulposus cells were isolated from adult rabbit discs and seeded onto bi oactive glass. At selected time intervals, the cells and glass were evaluat ed. We found that the cells rapidly attached to the substrate, colonizing i t within 12 h. By 21 days, they had formed a lawn of cells over the glass s ubstrate. DNA measurements showed a progressive increase in cell number wit h time. The phenotype was maintained; the cells expressed aggrecan, and col lagen type II and I, but were negative for collagen type X. CD44, a cell-su rface glycoprotein that binds hyaluronate, was also expressed by these cell s. Electron dispersive X-ray analysis and Fourier transform infrared spectr oscopy revealed calcium phosphate-rich layer formation on the substrate sur face. The results of this study suggest that nucleus pulposus cell prolifer ation may be an anchorage dependent event, and that the cells use the calci um phosphate-rich layer to facilitate cell adhesion, and subsequent prolife ration. These findings point to the importance of the conditioned bioactive glass as a substrate for nucleus pulposus cells. (C) 2000 John Wiley & Son s, Inc.