Effects of hypergravity on the cell shape and on the organization of cytoskeleton and extracelluar matrix molecules of in vitro human dermal fibroblasts.

In vitro human dermal fibroblasts were submitted to normal gravity (1 g) or to chronic hypergravity ranging from 2 to 20 g for 8 days. Changes only appeared above 15 g. The majority of 20 g-subjected cells showed fine filipods in the shape of a star whereas most control cells had rounded shapes and spread by forming lamellipodia. Indirect immunofluorescence staining of vinculin, alpha-actinin and actin stress fibers showed changes of the arrangement anchoring points of stress fibers under hypergravity. Tubulin staining showed that the centrosomal material generally located above the nucleus in control cells had migrated to the nucleus side in 20 g-exposed cells. After 8 d of culture under 20 g hypergravity the thickness of fibronectin network seemed to be increased and bundles of fibrils appeared linking ordered arrays of fibers. The fibrils of collagen I formed better delimited and thicker bundles of fibers. We may assume that 20 g hypergravity can induce changes in fibroblast cell shape, migration way, and anchorage leading to a reorganization of extracellular matrix without concomitant change of cell proliferation.