SUBSTRATUM SURFACE-TOPOGRAPHY ALTERS CELL-SHAPE AND REGULATES FIBRONECTIN MESSENGER-RNA LEVEL, MESSENGER-RNA STABILITY, SECRETION AND ASSEMBLY IN HUMAN FIBROBLASTS

The regulation of cell shape, fibronectin mRNA level, secretion and as sembly by substratum surface topography was investigated in early pass age human gingival fibroblasts cultured on titanium-coated smooth or V -shaped grooved substrata produced by micromachining. Cells on grooved surfaces were significantly elongated and orientated along the groove s of the substratum, while cell height, measured using confocal scanni ng laser microscopy, was similar to 1.5-fold greater than that of cell s on smooth surfaces. Northern hybridization analysis revealed that on a per cell basis the grooved surface increased the amounts of fibrone ctin mRNA/cell similar to 3.5-fold at 16 hours, similar to 1.9-fold at 40 hours and similar to 2.2-fold at 90 hours, while the mRNA levels o f the house-keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAP D) were constant, The amounts of secreted fibronectin on the grooved s urface were increased similar to 2-fold for all time points, The stabi lity of fibronectin mRNA was also altered by substratum surface topogr aphy. The half-life of fibronectin mRNA on smooth surfaces was estimat ed to be similar to 5 hours, but on the grooved surfaces the half-life of fibronectin mRNA showed a two-phase response: a rapid 60% reductio n in the first half-life (t(1/2) similar to 2 hours) and a 2.4-fold in crease in the second half-life (t(1/2) similar to 12 hours) relative t o that observed on the smooth surface. The GAPD mRNA half-lives were e ssentially unaffected by the surface topography of the substrata, The grooved surface was also found to alter the amount of fibronectin asse mbled into the extracellular matrix, producing a similar to 2-fold inc rease in the cultures at all time points, It thus appears that substra tum surface topography alters cell shape and modulates fibronectin at the transcriptional and post-transcriptional levels, as well as the am ount of fibronectin assembled into extracellular matrix, Micromachinin g, which has the ability to precisely control surface topography over a wide range of dimensions and shapes, appears to be a useful techniqu e in investigating the relationship between cell shape and function.