Recent advances in biological uses of traction force microscopy

Cell traction forces (CTF) generated by the actomyosin cytoskeleton onto a substrate or extracellular matrix (ECM) are essential for many biological processes, including developmental morphogenesis, tissue homeostasis, and cancer metastasis. Because the cellular physical properties are closely related to the pathological states of the cells, affected by various physicochemical stimuli from their neighboring cells or surrounding environments, it is crucial to develop a quantitative measure for cellular responses to these external stimuli. Since the pioneering work of Harris et al. in 1980s1, traction force microscopy (TFM) has been widely used as a standard tool that allows the optical measurement of cellular tractions exerted on 2- and 3-dimensional soft elastic substrates. Recently, there have been many technical advances in conventional TFM to enhance its spatial and temporal resolutions as well as the range of applicability. In this review, we provide a survey on the recent advancement in TFM, especially with a special emphasis on platforms that can externally apply various stimuli such as fluid shear, mechanical tension or compression, biochemical factors, and electric field in a physiologically relevant regime.