Cell Migration

A kerytcyte migrates along a glass slide and runs into an obstacle: an AFM cantilever stuck to the glass slide (vertical bar near the center of the image). The keratocyte continues moving around the obstacle on both side, where finally the larger part of the cell "wins". This optical microscopy videograph has been recorded with a technique called Reflection Interference Contrast Microscopy (RIFM), or often called Antiflex. In this technique the contrast is due to interference between the upper surface of the glass slide and the lower surface (membrane) of the cell. Depending on the distance interference fringes are visible for small distances up to 1 µm or so. So, these images only show parts of the cell, which are close to the substrate, and do not show parts of the cell far away from the substrate. So, the images can be misleading: e.g. the final images right before the left part of the cell is pulled over to the right shows only a very thin connection between the two parts of the cell. However: there is only a thin connection between these two parts of the cells in contact. The large fraction of the cell is detached and therefore not visible here.

(Zeiss Axiovert 135, 63x oil immersion, Antiflex lense)

A migrating keratocyte runs into a flexible AFM cantilever and deflects it while squeezing under it. In this video sequence the large deflection by the cell body, exerting a force of 40 nN can be easily picked up by eye. What is harder to see by eye, but can be extracted by image analysis to analyze the initial contact of the leading edge of the cell with the obstacle.

Time lapse movie of fibroblast migration on a petri dish. At 14:36:54 the myosin light chain kinase inhibitor DM is injected, resulting in a retraction of cells. At 14:46:25 the cells recoverd from the drug and start adhering again.