By Sean Henahan, Access Excellence

NEW ORLEANS- November 12, 1996 A close-up look of living heart cells provided by atomic force microscopy is providing new insights into the importance of the protein fiber network or "skeleton" supporting the cell membranes, report researchers.

Investigators at Johns Hopkins University studied the matrices of living heart cells using atomic force microscopy, a technique in which an image is formed from data provided by a minute needle passing over the surface of the cell.

The work indicated that the structural components of heart cells help control chemical activities within the cells. The Hopkins team reduced the normal amount of the protein actin in the "skeletons" of living connective tissue cells in the heart. The scientists then used the microscope, which also measures a cell's mechanical properties, to touch the outer surface of the cells.

Cell surfaces usually have hard and soft regions, but the results showed that cells with less actin lost elasticity over their entire surface. This indicates that actin plays an important role in a cell's structural integrity and internal chemical activities.

The experiments were testing whether actin helps control the cells' internal motions, and whether reducing actin would affect the cells' structure and function. Cells, whether normal or abnormal, are always active. This includes occasionally disassembling and reassembling their skeletal fibers as the cells carry on chemical reactions. These studies are the first to provide evidence that disrupting a particular protein weakens the cellular "skeletons", the protein fiber network supporting the cell membrane, of some heart cells.

The findings suggest that measuring elasticity of some heart cells may improve understanding of healthy and diseased cells. This in turn could lead to better diagnosis and treatment of heart disease, according to scientists.

"Our results suggest atomic force microscopy is a powerful tool for better measuring and understanding what's going on inside these cells," says Frank Chi-Pong Yin, M.D., Ph.D., professor of medicine at Johns Hopkins.

The scientists' next step will eb to determine if a less elastic "skeleton" prevents cells from functioning normally. This may eventually help to develop therapies to repair abnormal cells or stop them from doing harm, says Dr. Yin.