Deposition of collagen fibril bundles by long-term culture of fibroblasts in a collagen sponge.

Human fibroblasts cultured for 10 days in a collagen sponge migrated through the pores of the sponge and expressed a moderate mitotic activity, which stabilized after 10 days, and a high collagen and protein synthesis. Between 10 and 27 days, the newly synthesized collagen filled the pores of the sponge. This matrix accumulation induced a delayed decrease of collagen and protein synthesis. Finally, after 27 days of culture, the fibroblasts expressed low bio-synthetic activities similar to the ones exhibited in vivo. The newly synthesized matrix was highly differentiated, as shown by the presence of a dense network of quarter-staggered collagen fibrils (42 nm ± 6 nm in diameter) surrounding the cells. The size and the shape of these fibrils demonstrated that the newly synthesized procollagen was fully processed in collagen by removal of their N- and C-terminal propeptides. Moreover, these fibrils were packed in bundles organized into an interwoven network that mimics the pattern of the papillary dermis. These findings show that fibroblasts cultured for one month in a collagen sponge construct large amounts of a highly differentiated connective tissue. © 1996 John Wiley & Sons, Inc.