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Professor Igor Sokolov Uses Atomic Force Microscopy to Study Human Epithelial Cells

CAMP Professor Igor Sokolov, in collaboration with his M.S. student Tamara Berdyyeva and Professor Craig Woodworth (of Clarkson's Biology Department), discovered a change of elasticity of human epithelial (HKC) cells with ageing. This result was found by using an atomic force microscopy (AFM) technique in-vitro. The method used a silica sphere (5 Ám in diameter) glued to an AFM cantilever. This modified AFM probe provided stable and repeatable results over the entire area of an individual cell, which was a problem while using a standard AFM probe. See Figure 5.

During the measurements, three different areas of rigidity were identified on the cell surface: the area of the nucleus, the cytoplasmic area, and the cell edge area.

Younger cells (10 to 20 population doublings) were found to be consistently softer than the old cells (40 to 60 doublings), so-called senescent cells. Specifically, the nuclear regions of the old cells have 2 times higher Young modulus than the Young modulus of the young cells. Also the cytoplasm and edge regions of senescent cells have a 3-5 times higher Young's modulus than young ones.

The results have been proved statistically. The change of cell rigidity was proved based on measurements of tens of different cell samples. Also each cell was measured in hundreds of points.

The observed rigidity change might be attributed to a difference in the organization of cell cytoskeleton. At present, Professor Sokolov and his collaborators have developed a new method for visualizing the cellular cytoskeleton by using atomic force microscopy. Figure 6 presents an AFM scan showing a few cells and their cytoskeletons. Professor Sokolov's group is also investigating directional enzyme alteration of the cytoskeleton and its influence on the rigidity of young and old cells. Change of elasticity of human epithelial tissues with ageing has been known for a long time and is an important factor in the development of various diseases. Therefore rigidity change of the epithelial cells found in Professor Sokolov's work may be useful in the area of skin disease treatments. His reported results may have applications in the pharmaceutical industry as a preliminary screening tool of anti-ageing drugs, which would help to maintain the "young" cellular elasticity. In addition, this research may even bring attention to a new direction in rejuvenating human skin.

Figure 5. A 5 Ám silica sphere, glued to a standard AFM cantilever, was used to obtain stable and repeatable results over the area of the whole individual cell.

 

Figure 6. Visualizing the cell cytoskeleton is possible by the AFM technique using a new method developed by Professor Sokolov and his colleagues.

For more information about Professor Sokolov and his research, please call him at 315-268-2375 or send email to isokolov@clarkson.edu.

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