Cellular responses to environmental stimuli: Influence of fluid shear and substratum hydrophobicity on adhesion of human fibroblasts

Morphological changes in human skin fibroblasts adhering to hydrophobic and hydrophilic substrata were studied in a parallel‐plate flow chamber using light‐ and scanning electron microscopy. Cells were seeded on the bottom plate of the flow chamber, which was made of the substratum being studied, and allowed to adhere for 3–6 h. Then, the seeded cells were exposed to an incrementally increased laminar flow. Light microscope observations were performed in situ in the flow chamber. Fixation for electron microscopy was also done in situ in order to avoid passing cells through a liquid‐air interface which would create a high shear stress relative to ones which remain submerged. Cells spread far less on the hydrophobic material than on the hydrophilic material and reached the point of detachment at a significantly lower shear stress (22 dynescm^‐2 vs 324 dynescm^‐2 on the hydrophilic substratum). Cells on the point of detachment had a similar morphology on both substrata, viz. rounded to a nearly spherical shape and occasionally displaying filopodial networks when viewed by scanning electron microscopy. In situ observations showed that some cells on the point of detachment were anchored to the surface only by thread‐like extrusions up to 100 pm long, thus resisting detachment. These structures returned to the cell body upon detachment and cellular debris ("footprints") was seldom seen. Summarizing, this study shows that fluid shear may be an important environmental stimulus causing adhering cells to adjust their morphology and that, the effect of fluid shear is dependent on substratum hydrophobicity.

Key words:

• fibroblasts
• hydrophobicity
• shear
• adhesion
• spreading
• detachment

Notes

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