Phenotypic modulation of fibroblasts and its application for periodontal regenerative therapy

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We investigated the relevance of proliferation to the deposition of fibronectin (FN) and matricellular proteins into the extracellular matrix (ECM) during the formation of multiple cell-layer sheets of fibroblasts. Normal human gingival fibroblasts grown to confluence were treated with 10% fetal bovine serum, ascorbic acid, and transforming growth factor-β for 6 days. This treatment led to a 3-fold increase in cell numbers on day 6. Bromodeoxyuridine (BrdU) incorporation assays showed that cells in the S phase of the cell cycle increased on day 2. BrdU-positive cells were uniformly distributed through monolayers on day 2 and were localized around multiple cell-layers on days 4 and 6. FN and thrombospondin-1 were densely arranged into a pericellular ECM on day 0. Similar results were observed for up to 6 days. Osteonectin/SPARC was detected in cells, but not in the ECM throughout the culture periods. Tenascin-C was sparsely distributed between cells on day 0, and was densely deposited into a pericellular ECM on day 2. Quantitative immunoassays showed a 6-fold increase in tenascin-C deposition on day 2. Thus, these results suggest that the deposition of tenascin-C into the ECM is relevant to the reentry of density-dependent growth-arrested fibroblasts into the cell cycle.