Figure 3.

Shear stress transformed the thin KIF bundles found in control cells (see Fig. 1) into much thicker tonofibrils in a shear time-dependent manner. A–D) Cells were exposed to flow generating a shear force of 15 dyn/cm² for 2 h (A), 4 h (B), 7 h (C), or 6 h (D). The thickened KIF bundles become progressively more convoluted (wavy) with increasing shear times. Shearing also resulted in the disappearance of most of the keratin particles from the interfilamentary spaces (C). Not all cells responded to shear stress in this way. KIF networks in 2 cells shown in D were extensively reconfigured by flow, whereas several others in proximity (asterisks) were entirely unaffected and retained all of the features of nonsheared cells (cf. Fig. 1). E) Vertical section through 2 adjacent cells reconstructed from a Z stack of confocal images. Cells were sheared for 4 h at 15 dyn/cm² and stained with K18 pAb. Note that the height of the cell that responded to flow (left) is considerably greater (∼1.5×) than the one that did not (right). This difference was seen consistently when responder cells were compared to nonresponders. Reverse-contrast confocal (monochrome) images of sheared cells fixed in formaldehyde and immmunostained with pAb K18. Scale bars = 10 μm (A, B, D); 5 μm (C).