Migration of intervertebral disc cells into dense collagen scaffolds intended for functional replacement

Invasion of cells from surrounding tissues is a crucial step for regeneration when using a-cellular scaffolds as a replacement of the nucleus pulposus (NP). The aim of current study was to assess whether NP and surrounding annulus fibrosus (AF) cells are capable of migrating into dense collagen scaffolds. We seeded freshly harvested caprine NP and AF cells onto scaffolds consisting of 1.5 and 3.0% type I collagen matrices, prepared by plastic compression, to assess cell invasion. The migration distance appeared both time and density dependent and was higher for NP (25%) compared to AF (10%) cells after 4 weeks. Migration distance was not enhanced by Hst-2, a peptide derived from saliva known to enhance fibroblast migration, and this was confirmed in a scratch assay. In conclusion, we revealed invasion of cells into dense collagen scaffolds and therewith encouraging first steps towards the use of a-cellular scaffolds for NP replacement.