Chiral force generation of cells on micropatterns

Abstract

The current study combines high throughput micropatterning, image processing, and traction force microscopy to develop a comprehensive system for examining the mechanical phenomena associated with the establishment of LR asymmetry. Observing the traction forces of chiral cells reveals an increase in the magnitude directly adjacent to the boundary of the ring micropattern. At the ring edges the traction forces in the radial direction pull inwards contracting the micropattern and the surrounding substrate. Forces in the circumferential direction at the ring boundaries are biased in the left or right direction depending on the observed cell chirality. In cells that are observed to have a counter-clockwise bias (C2C12 and MDCK) the circumferential forces are biased towards the right. For cell lines that are observed to have a clockwise bias (HUVEC) the circumferential forces are biased towards the left. The force imbalance in the circumferential direction is characteristic of collective biased migration. The inhibition of F-actin, using Latrunculin A, reduces the overall magnitude of traction forces, but not uniformly. A more effective decrease in circumferential traction forces compared to radial traction forces is observed, identifying actin as a crucial component in creating circumferential force imbalance. Inhibition of cell-cell communication through the disruption of adherens junctions yields non-chiral cell arrangements in the central portion of the micropattern, while cells on the edge remain biased. This highlights the importance of cell-cell adhesion in forming a global chiral bias. This work has demonstrated that inclusion of traction force analysis in the examination of cell chirality adds deeper understanding to the phenomenon and may, in the future, assist in determining causation of diseases pertaining to loss of LR asymmetry.

Asymmetric tissue development is a well-conserved biological property that is imperative during embryogenesis. Failure to establish proper left-right (LR) asymmetry (also known as handedness and chirality) results in potentially deadly disease states; such as congenital heart defects. Understanding which genetic and epigenetic factors affect the establishment of left-right asymmetry creates opportunities to better diagnose and treat disease. Wan et al. has developed a high throughput system utilizing micropatterning and image analysis software to effectively measure cell chirality through migration and alignment in vitro. Although robust, biomechanical mechanisms are not yet well understood.