Characterizing fibroblast migration on discrete collagen threads for applications in tissue regeneration.

Collagen threads with mechanical properties and fibrillar substructure similar to native tissue have been synthesized for the repair of injured tendon and ligament. While these scaffolding materials have demonstrated the potential for inducing tissue regeneration, one limitation has been an insufficient rate of tissue ingrowth for complete regeneration. We hypothesize that the structural hierarchy and biochemical cues on the surfaces of these threads will enhance the rate of cell migration and ultimately the rate of new tissue ingrowth. We developed an in vitro assay to measure the effects of various collagen sources and crosslinking on the rate of fibroblast migration on the surfaces of collagen threads. Threads were suspended from elevated platforms and seeded with fibroblast-populated collagen lattices. Cell migration rates ranging from 0.75 to 1.25 mm/day were measured as the fibroblasts left the lattices and migrated onto various thread types. Threads self-assembled from type I collagen were found to have migration rates similar to native tendon threads while crosslinking by severe dehydration decreased the rate. This novel in vitro model system allows examination of cell migration from a wound margin onto biomaterials to determine the effects of various cell types, matrix materials, and surface biochemistries on cell-matrix interactions. Ultimately, this assay will allow us to identify design parameters that will be most effective for enhancing the rate of tissue ingrowth on fiber-based collagen scaffolds for soft tissue regeneration.