Effects of collagen type on the behavior of adult canine annulus fibrosus cells in collagen-glycosaminoglycan scaffolds.

The healing of intervertebral disc defects may be improved by the implantation of cell-seeded collagen-based scaffolds. The present study evaluated in vitro the effects of the collagen type (type I vs type II) from which the scaffolds were fabricated on the behavior of adult canine annulus fibrosus cell-seeded collagen-glycosaminoglycan (GAG) scaffolds. Protein and GAG biosynthesis continued through the 8-week period of the experiment, demonstrating the viability of the cells in type I and type II collagen-GAG scaffolds. Statistical analysis revealed no significant effect of the type of collagen that makes up the scaffold on the biosynthetic activity. For both scaffold types, the amount of retained newly synthesized proteins increased from 1 to 2 weeks and from 6 to the 8 weeks. In contrast, the rate of GAG retention increased to a maximum at 4 weeks for both types of scaffolds, then decreased to about 50% of that level after 8 weeks. The number of cells generally increased the first week but then decreased in type I scaffolds while remaining constant in type II scaffolds. It could be assumed that most newly synthesized protein was lost to the medium, as the quantity of protein and collagen remained constant. Cell-mediated contraction of the scaffolds contributed to folds that formed in the constructs and to create an oriented architecture tissue. These findings commend the use of a type II collagen-GAG scaffold for further study on the basis of its maintenance of cell number and the slightly higher accumulated GAG content.