Cellular motility in vitro as revealed by scanning acoustic microscopy depends on cell-cell contacts

Abstract

A new method is described for observing and quantifying an aspect of contact inhibition of cell movement that is sometimes called "contact paralysis". Based on the scanning acoustic microscope (SAM), the method can detect changes in the mechanical properties of cells, as well as changes in their motility and may therefore be more sensitive to some dynamic changes than methods based on optical microscopy. With this method intracellular motility of normal and transformed cells of epithelial and fibroblastic origin was investigated. By subtraction of SAM images patterns of motility, domains were detected that changed in a characteristic way among various cell lines. Wave-like and nucleating domains could be distinguished; they were also used for the quantification of motility. Like migration intracellular motility is influenced by cell-cell contacts. In zones where a cell touches its neighbours motility domains change or disappear depending on the cell type. In immortalized epithelial cells (XTH-2 cells) large quiescent zones developed in the region where contact with neighbouring cells was established, whereas in fibroblastic (3T3) cells motility was reduced less and did not change in domain pattern. Epithelial and fibroblastic cells were less motile when in contact with other cells or in confluent cultures than when solitary, i.e. their motility was contact inhibited. Transformed (SV40 3T3) cells, however, did not reduce their motility when in contact to or enclosed by other cells. The molecular basis for motility domains remains to be investigated.

Dependence of Energy Metabolism on the Density of Cells in Culture.

“…This reduction in substrate supply seems to be balanced by diminished ATP requirements as is shown by almost constant energy charge just before further proliferation is inhibited. The reduction of two important energy consuming processes may be involved in the reduction of ATP requirements, cell motility (2,22,23,40) including the turnover of cytoskeletal elements and the Na/K-ATPase (17, for review see 7), both of which are reduced by cell-cell contacts. Kajstura and Korhoda (1982) postulate depletion of basic metabolites for macromolecular synthesis by the reduction of respiration (citric acid cycle).…”

Tension modulates cell surface motility: A scanning acoustic microscopy study

“…Both terms represent the extent of the grey level distribution change in the specified area. To take both terms equally into account, they were multiplied [modified from Zoller et al, 1997]. The grey value differences due to motility are rather small.…”

“…In general, SubSAM revealed that the cell surface is highly inhomogenous in its dynamic behaviour. The surface activities within 10 s appear as distinct domains of active zones (motility domains) distributed over the otherwise non-active quiet surface Zoller et al, 1997]. Corresponding to their shape, the domains were differentiated into spot-shaped nucleating domains all over the surface and wave-like domains at the cell edges.…”

“…In addition, SubSAM reveals disappearing protrusions as well. Cell surface activities were commonly studied in locomoting cells, whereby SubSAM studies revealed that all investigated cell types in a non-migrating state (fibroblasts, epithelial and endothelial cells) exhibit cell surface motility Zoller et al, 1997].…”

“…The motility can be quantitated by the changes of grey levels and is expressed as a standardised motility value (M); This M-value is shown to be correlated to the cytoplasmic ATP-content. The first investigations using SubSAM revealed that tumour transformed cells have a higher level of cell surface motility Zoller et al, 1997]. With regard to the observations that tumour cells reveal an altered cytoskeletal organization [Pokorná et al, 1994] and that they may have a reduced surface tension [Thoumine and Ott, 1997], the influence of tension and cytoskeletal integrity on subcellular surface motility became of interest.…”