Axisymmetric Drop Shape Analysis for Estimating the Surface Tension of Cell Aggregates by Centrifugation

Abstract

Biological tissues behave in certain respects like liquids. Consequently, the surface tension concept can be used to explain aspects of the in vitro and in vivo behavior of multicellular aggregates. Unfortunately, conventional methods of surface tension measurement cannot be readily applied to small cell aggregates. This difficulty can be overcome by an experimentally straightforward method consisting of centrifugation followed by axisymmetric drop shape analysis (ADSA). Since the aggregates typically show roughness, standard ADSA cannot be applied and we introduce a novel numerical method called ADSA-IP (ADSA for imperfect profile) for this purpose. To examine the new methodology, embryonic tissues from the gastrula of the frog, Xenopus laevis, deformed in the centrifuge are used. It is confirmed that surface tension measurements are independent of centrifugal force and aggregate size. Surface tension is measured for ectodermal cells in four sample batches, and varies between 1.1 and 7.7 mJ/m2. Surface tension is also measured for aggregates of cells expressing cytoplasmically truncated EP/C-cadherin, and is approximately half as large. In parallel, such aggregates show a reduction in convergent extension-driven elongation after activin treatment, reflecting diminished intercellular cohesion.

Cadherin Point Mutations Alter Cell Sorting and Modulate GTPase Signaling

“…Importantly, a 3-fold difference in the three-dimensional (solution) affinity corresponds to a difference in bond energies of ,1 kcal/mole at 37˚C that could be readily offset by cadherin expression levels or cortical tension (Duguay et al, 2003;Kalantarian et al, 2009;Krieg et al, 2008;Manning et al, 2010;Steinberg and Takeichi, 1994;Winklbauer, 2009). The capacity of cadherin affinities to regulate actin organization through GTPase signaling introduces an additional mechanism that could augment or offset differential cadherin adhesion.…”

Tissue surface tension measurement by rigorous axisymmetric drop shape analysis

“…In previous work [8], after centrifugation, aggregates were fixed and fractured (cut in half in a vertical plane) so that each half could be lay on its side and its cross-section imaged from above. In the present study, explants were placed on an immersed surface adjacent to an angled mirror (Fig.…”

“…In previous work, we demonstrated a simple drop shape method called ADSA-IP (axisymmetric drop shape analysis for imperfect profile) and used it to measure tissue surface tensions of centrifuged aggregates from the frog Xenopus laevis [8]. ADSA-IP fits experi- mental profiles to Laplacian curves by matching width, height, and volume.…”

Mechanosensitive shivering of model tissues under controlled aspiration

“…It has been shown that cellular aggregates behave like viscoelastic liquids possessing a surface tension (16). The mechanical properties of cellular aggregates have been characterized by parallel-plate compression (16,17), micropipette aspiration (18), and aggregate centrifugation (19). The origin of the surface tension has not been fully elucidated, but the cellular cortical tension (which determines the surface tension of a single cell) and the cell-cell adhesion have been identified as the two major responsible mechanisms (20)(21)(22).…”