Collagen gene expression and mechanical properties of intervertebral disc cell-alginate cultures

Cells of the intervertebral disc have a limited capacity for matrix repair that may contribute to the onset and progression of degenerative disc chang es. In this study, the biosynthetic capacity of cells isolated from specifi c regions of the porcine intervertebral disc was evaluated in vitro. Using a competitive reverse transcription-polymerase chain reaction technique, ge ne expression levels for types I and II collagen were quantified in cells c ultured for up to 21 d in a three-dimensional alginate culture system and c ompared to levels obtained for cells in vivo. The mechanical properties of cell-alginate constructs were measured in compression and shear after perio ds of culture up to 16 weeks, Cells from the anulus fibrosus expressed the most type I collagen mRNA in vivo and in vitro, while cells from the transi tion zone expressed the most type II collagen mRNA in vivo and in vitro. Me chanical testing results indicate that a mechanically functional matrix did not form at any time during the culture period; rather, decreases of up to 50% were observed in the compressive and shear moduli of the cell-alginate constructs compared to alginate with no cells. Together with results of pr ior studies, these results suggest that intervertebral disc cells maintain characteristics of their phenotype when cultured in alginate, but the molec ules they synthesize are not able to form a mechanically functional matrix in vitro. (C) 2001 Orthopaedic Research Society. Published by Elsevier Scie nce Ltd. All rights reserved.