Contact guidance in vitro: A light, transmission, and scanning electron microscopic study

Abstract

Contact guidance was studied in cultures of chick heart fibroblasts and kidney epithelium by observing the relation of these cells to fine grooves ruled in plastic culture dishes, and also to ridges or grooves in plastic replicas moulded from rulings made in metal. The relation of the cells to the regularly arranged collagen fibers of fish scales was also studied by scanning and transmission electron microscopy (SEM and TEM). On the rulings with groove periodicity in the range of 5 μm about 75% of the cells were aligned, but on grooves separated about 30 μm only 60% of cells were aligned. Cytoplasmic components of the cells such as microfilaments maintained a constant relation to the axis of the cell as a whole, but they, and also any cytoplasmic extensions, such as filopodia, bore no consistent relation to any features of the substratum, whether or not the cells were aligned. The cells were not guided to become aligned by filopodia or lamellipodia. The most remarkable and consistent finding was that cells bridged over grooves without contacting their surfaces, whether the grooves were 2 or 10 μm wide. The bridging was a characteristic of cells growing on any of the substrates, including those with grooves or ridges, and also of collagen substrates made from fish scales. A hypothesis is proposed to explain the contact guidance seen on ridged or grooved substrata and on the orientated collagen fibers involving the observed cell bridging and the fact that linear cell-to-substrate contacts (focal contacts) are known to be vital for cell movement. The cell is considered to be stiff so that as it bridges over much of the substratum there is only a limited area available for contact. Assuming that focal contacts need to be of a certain length to provide adhesion, a cell orientation that presents the maximum linear contact would be favoured. An examination of the results of this study and of the reports in the literature shows that cells on these types of substrata take on an orientation such that linear contacts would be expected to predominate.