Association of fibroblast orientation around titanium in vitro with expression of a muscle actin

The objective of this study was to investigate the association of cell orie ntation around a biomaterial with expression of a contractile actin isoform , Selected cytokines and a fungal metabolite known to alter the cytoskeleto n were used to modulate the fibroblast orientation around titanium in vitro and the synthesis of a specific muscle actin in order to reveal an associa tion between these processes. A novel culture system using a fibronectin-co ated silicone surface was employed to evaluate the orientation of human gin gival fibroblasts around titanium discs. Round glass cover slips, 25 mm in diameter, were coated with polydimethylsiloxane. During the heat-induced po lymerization process, two commercially pure titanium discs, 5 mm in diamete r, were placed on the silicone at a distance of approximately 0.5 mm apart. The rubbery consistency of the silicone stabilized the metal discs on the cover slip and eliminated the risk of developing a lip at the edge of the t itanium sample. The cover slip was then heated to complete polymerization o f the silicone and subsequently coated with fibronectin. One hundred thousa nd human gingival fibroblasts were plated onto each glass cover slip contai ning the titanium discs. The cells were treated with one of the following p rior to seeding on the cover slips: transforming growth factor-beta 1 (TGF- beta 1), platelet-derived growth factor-BB (PDGF-BB), interferon-gamma (IFN -gamma) for cytochalasin-D. Untreated cells served as controls. The orienta tion of the cells at the surface of the titanium discs was evaluated micros copically and the cell content of a-smooth muscle actin (SMA) was determine d by Western blot analysis and immunohistochemistry. A notable finding was the high correlation between the percentage of cells oriented perpendicular to the titanium surface and SMA synthesis. TGF-beta 1, IFN-gamma and cytoc halasin-D increased synthesis of SMA while PDGF-BB decreased it. The findin gs support the proposition that SMA-enabled cell contraction may play a rol e in the orientation of cells to a biomaterial surface. (C) 2000 Elsevier S cience Ltd. All rights reserved.