Rubber Substrata Research Articles

Tissue culture cells on deformable substrata: biomechanical implications.

A method has been developed for the study of the forces which individual cells exert during their locomotion. Polydimethyl-siloxane (silicone fluid) was crosslinked on its surface by brief flaming to form a thin layer of silicone rubber. Tissue culture cells of many types were then plated out onto these rubber substrata and the propulsive forces these cells exert as they adhere and spread became visible as wrinkles and other distortions in the rubber. From time-lapse films of these distortions, it appears that the component cells of the body move by exerting shearing forces through their plasma membranes. How these forces are exerted and how this technique for observing them could be made more quantitative are discussed.

Increased contractile strength and tightened adhesions to the substratum result from reverse transformation of CHO cells by dibutyryl cyclic adenosine monophosphate.

We have examined the changes in cellular contractility and adhesive morphology that accompany the reverse transformation of CHO cells caused by dibutyryl cyclic adenosine monophosphate. The ability of these cells to distort elastic silicone rubber substrata was found to increase markedly over the 5 h period following addition of cyclic AMP and testosterone to the medium, and to relax again following hormone removal. Parallel changes were observed in the interference reflexion image of the adhesion of these cells to glass substrata; broad grey-appearing 'close' contacts characteristic of the transformed state were gradually replaced by numerous small black-appearing 'focal contacts'. These changes in adhesive morphology required considerably longer (20-25 h) to be completed or to revert, however.

Behaviour of vascular smooth muscle cells during repeated stretching of the substratum in vitro

Smooth muscle cells derived from rat aortic media were established in subcultures and seeded from suspensions on smooth silicone rubber substrata in tissue culture flasks. Each flask contained two substrata, one stationary and one that was stretched and allowed to recoil at 15-s intervals. After 48 h or longer, the cells were fixed and their pattern on the 2 substrata examined by light or scanning electron microscopy. All stretched substrata showed 75% or more of cells lying within 45° of a line drawn at right angles to the direction of stretch and recoil. Cells on the stationary substrata showed a random orientation. The results suggest that stretching of the internal elastic lamina by arterial pulsation may be a factor in creating the characteristic longitudinal orientation of smooth muscle cells that appear in the subendothelial space after injury, diffuse intimal thickening or atherosclerosis.

Reorientation response of cells to repeated stretch and recoil of the substratum

The effect of directional stretching of the substratum on cell orientation was investigated using Earle's L strain fibroblasts. An apparatus was constructed that caused a silicon rubber substratum to undergo periodic elongation and recoil at 15 sec intervals. This substratum was contained within a flask that also held a control (static) substratum of the same material. Examination of the pattern of cells by scanning electron microscopy (SEM), made after 18–24 h incubation, showed a highly significant preponderance over the controls of cells on the stretching substrata arranged with their long axis at right angles to the direction of stretching. The observation is interpreted as an avoidance reaction to stretching based on the cells' adhesion by linear focal contacts, which run parallel to the long axis of the cells, and which are associated with microfilaments.

Silicone rubber substrata: a new wrinkle in the study of cell locomotion.

When tissue cells are cultured on very thin sheets of cross-linked silicone fluid, the traction forces the cells exert are made visible as elastic distortion and wrinkling of this substratum. Around explants this pattern of wrinkling closely resembles the "center effects" long observed in plasma clots and traditionally attributed to dehydration shrinkage.