Mechanics and dynamics of cellular contacts

Mechanics and dynamics of adhesion during early development of Dictyostelium discoideum

Cell-substrate adhesion of eukaryotes still remains to be fully understood. As Dictyostelium discoideum  (D.d.) lacks integrins, it is ideally suited to study alternative adhesion properties reflective of eukaryotic evolution with Single Cell Force Spectroscopy (SCFS, Figure 1).

Figure 1:

SCFS assay. Side view of cell attached to cantilever.

Below: Force-separation curve.


We attach single cells to a cantilever and probe quantitatively cell-substrate adhesion. We analyse substratum adhesion on elastic substartes or during development in terms of e.g. maximum adhesion force FMax.Adh. and work of adhesion WAdh. (Figure 2).

Figure 2:

WAdh. and FMax.Adh are reduced during early development of Dictyostelium cells.


D. d. also synchronizes itself during starvation inducing waves of cAMP. We have quantified these collective phenomena on the intercellular level by applying electric impedance measurements. We showed that cells seeded on micrometer-sized gold electrodes provoke impedance oscillations [1]. We record time dependent correlation of Electrical-Cell-substrate Impedance Sensing (ECIS) signals [2, 3] and changes in height detected by TIRF-microscopy by comparing light intensity of subtracted BF images from both assays. A high impedance signal IZI is found to correlate with a high fluorescence intensity and thus with a small cell-surface-distance

Figure 3:

Periodic fluctuations of cell-substrate distance or contact area (arrow) from changes in the fluorescence intensity (TIRF) (A). 2-D aggregation (B): By counting isolated cells (green) on each frame (e.g. I vs II), we obtain an oscillating signal (red) highly crosscorrelated with the ECIS signal (blue), indicating a high number of aggregated cells (blue).

The arrangement of cells analyzed on bright field images reveals synchronous formation of cell aggregates contributing to impedance oscillations (Figure 3B), while a decrease of circularity <C> occurs out-of phase. Modeling calculations show that cells in united structures generate higher impedance values than the same number of isolated cells [4]. In addition, we analyze starving cells in microfluidic devices in combination with an impedimetric assay (no flow) [5]. The results provide a quantitative understanding of the overall cell morphology, e.g. dynamics of cell-cell and cell-substrate adhesion during early starvation (Figure 4).

Figure 4:

Above: Origin of impedance oscillations. Below: Scheme of morphological changes occurring in phase.

In a further study on cellular contacts and in collaboration with the Luther-group, the goal is to use ECIS setups to obtain quantitative results on the electromechanical coupling and connectivity of primary co-cultures of rat cardiac myocytes and Fibroblasts in vitro. We analyze cardiac contraction dynamics with the ECIS method and combine it with confocal microscopy as shown in Figure 5.

Figure 5:

(Left) Coculture of cardiac myocytes and fibroblasts stained for alpha-actinin (red), vimentin (green), connexin 43 (yellow) and DNA (blue, Dapi). (Right) Contractile dynamics of cocultures with varying fibroblast fractions detected via ECIS impedance spectroscopy for the real part at 4kHz.

Contact: Kaumudi Prabhakara, Laura Turco, Marco Tarantola, Eberhard Bodenschatz

[1] E. Schäfer, C. Westendorf, E. Bodenschatz, C. Beta, B. Geil, A. Janshoff , Small  7 (2011).
[2] M. Tarantola, E. Sunnick, D. Schneider, A.K. Marel, A. Kunze, A. Janshoff, Chem. Res. Toxicol. 24 (2011).
[3] D. Schneider, M. Tarantola, A. Janshoff, BBA-Mol. Cell Res. 1813 (2011)
[4] E. Schäfer, M. Tarantola, E. Polo, C. Westendorf, N. Oikawa, E. Bodenschatz, B.Geil, A. Janshoff , Plos One 8 (2013).
[5] E. Schäfer, D. Aue, M. Tarantola, E. Polo, C. Westendorf, N. Oikawa, E. Bodenschatz, B. Geil, A. Janshoff , Comm. & Int. Biol. 6 (2013).