Synthetic mechanobiology: engineering cellular force generation and signaling

Abstract

Mechanobiology seeks to understand and control mechanical and related biophysical communication between cells and their surroundings. While experimental efforts in this field have traditionally emphasized manipulation of the extracellular force environment, a new suite of approaches has recently emerged in which cell phenotype and signaling are controlled by directly engineering the cell itself. One route is to control cell behavior by modulating gene expression using conditional promoters. Alternatively, protein activity can be actuated directly using synthetic protein ligands, chemically induced protein dimerization, optogenetic strategies, or functionalized magnetic nanoparticles. Proof-of-principle studies are already demonstrating the translational potential of these approaches, and future technological development will permit increasingly precise control over cell mechanobiology and improve our understanding of the underlying signaling events.

Figure 1. Graded control of cell mechanpbiology using conditional gene expression

Delivery of a constitutively active (CA) RhoA under the control of a tetracycline-repressible promoter allowed for concentration-dependent expression (a) and activity (b) of RhoA. This graded expression of CA RhoA or CA MLCK produced graded cell migration speeds (c) or traction force generation (d,e) compared to control (f). Reproduced with permission from Mackay et al. [16]

Figure 2. Control of cell contractile forces using optogenetics

(a) Skeletal muscle fiber isolated from mice expressing EYFP-tagged channelrhodopsin-2 (green), which localizes to the cell membrane, including the T-tubule membrane invaginations that surround sarcomeric alpha-actinin (magenta). Scale bar shows 10 µm. (b) Explanted soleus muscles contracted in response to blue light with dependence on light pulse duration and intensity. “Functional expression of ChR2 in skeletal muscle.” by Bruegmann et al. [45], licensed under CC BY 4.0 (c) Devices comprised of skeletal myotubules expressing channelrhodopsin-2 in matrigel-collagen gels surrounding PDMS cantilevers can be induced to contract axially or rotationally by controlling the region of illumination (circled in red). Reproduced with permission from Sakar et al.[46]