Mechanical Characterization of Microengineered Epithelial Cysts by Using Atomic Force Microscopy

Abstract

Most organs contain interconnected tubular tissues that are one-cell-thick, polarized epithelial monolayers enclosing a fluid-filled lumen. Such tissue organization plays crucial roles in developmental and normal physiology, and the proper functioning of these tissues depends on their regulation by complex biochemical perturbations and equally important, but poorly understood, mechanical perturbations. In this study, by combining micropatterning techniques and atomic force microscopy, we developed a simple in vitro experimental platform for characterizing the mechanical properties of the MDCK II cyst, the simplest model of lumen-enclosing epithelial monolayers. By using this platform, we estimated the elasticity of the cyst monolayer and showed that the presence of a luminal space influences cyst mechanics substantially, which could be attributed to polarization and tissue-level coordination. More interestingly, the results from force-relaxation experiments showed that the cysts also displayed tissue-level poroelastic characteristics that differed slightly from those of single cells. Our study provides the first quantitative findings, to our knowledge, on the tissue-level mechanics of well-polarized epithelial cysts and offers new insights into the interplay between cyst mechanics and cyst physiology. Moreover, our simple platform is a potentially useful tool for enhancing the current understanding of cyst mechanics in health and disease.

Reconstituted Postsynaptic Density as a Molecular Platform for Understanding Synapse Formation and Plasticity

“…When a target force (3 nN) was reached, the AFM probe retracted. The measured approach curves were found to be well described by the Hertz model (Kuznetsova et al, 2007;Shen et al, 2017), F = 4=3ER 1=2 d 3=2 , where E is the reduced Young's modulus of the material, R = 1/(1/R1 + 1/R2) is the effective radius of the probe R1 = d/2 and the droplet R2, and d is the indentation depth. In Figure 2D, the green dashed line shows the validity of the Hertz model for describing the measured approach curves, and the best fitting gives the elastic modulus E of the PSDs.…”

Edible Bird’s Nest, an Asian Health Food Supplement, Possesses Moisturizing Effect by Regulating Expression of Filaggrin in Skin Keratinocyte

“…The mechanical properties of HaCaT keratinocytes were characterized by atomic force microscope (AFM) (MFP-3D, Asylum Research, Santa Barbara, United States) supplemented with a colloidal probe. The colloidal probe was prepared by gluing a glass sphere ( in diameter) onto the free end of a tipless cantilever (CSC38, tipless, MikroMasch) with a typical spring constant ( Shen et al, 2017 ). The exact spring constant of the modified cantilever was calibrated by thermal power spectral density method ( Shen et al, 2017 ).…”

Hallmarks of Life in Single Cell Contact Mechanics: Outstanding Challenges and Perspectives

“…In the context of two-dimensional in-vitro cell culture models, cell confluency, or the percentage of substrate area covered by a monolayer of cells, has proven to be an influential factor in determining the mechanics of healthy epithelial cells, as compared to invasive tumor cells of the same type (Schierbaum et al, 2017), in enhancing membrane tension (Pietuch et al, 2013a,b) or in modifying the cell elasticity, although with quite different results in the latter case (Efremov et al, 2013;Schierbaum et al, 2017). In the context of 3D in vitro cell culture models, recent attempts have been reported to characterize the elasticity and cell-cell interfacial tensions of multicellular spheroids by cavitation rheology (Blumlein et al, 2017), as well as the overall viscoelasticity of epithelial cysts (Shen et al, 2017) and elasticity of multicellular spheres of mesenchymal stromal cells by AFM (Tietze et al, 2019). Both latter works provide evidence of characteristic relaxation dynamics and indentation mechanics that differ substantially to those of single cells.…”