Cells in 3D matrices under interstitial flow: Effects of extracellular matrix alignment on cell shear stress and drag forces

Abstract

a b s t r a c tInterstitial flow is an important regulator of various cell behaviors both in vitro and in vivo, yet the forces that fluid flow imposes on cells embedded in a 3D extracellular matrix (ECM), and the effects of matrix architecture on those forces, are not well understood. Here, we demonstrate how fiber alignment can affect the shear and pressure forces on the cell and ECM. Using computational fluid dynamics simulations, we show that while the solutions of the Brinkman equation accurately estimate the average fluid shear stress and the drag forces on a cell within a 3D fibrous medium, the distribution of shear stress on the cellular surface as well as the peak shear stresses remain intimately related to the pericellular fiber architecture and cannot be estimated using bulk-averaged properties. We demonstrate that perpendicular fiber alignment of the ECM yields lower shear stress and pressure forces on the cells and higher stresses on the ECM, leading to decreased permeability, while parallel fiber alignment leads to higher stresses on cells and increased permeability, as compared to a cubic lattice arrangement. The Spielman-Goren permeability relationships for fibrous media agreed well with CFD simulations of flow with explicitly considered fibers. These results suggest that the experimentally observed active remodeling of ECM fibers by fibroblasts under interstitial flow to a perpendicular alignment could serve to decrease the shear and drag forces on the cell.

Interstitial flow influences direction of tumor cell migration through competing mechanisms

“…Flow-induced stresses on a cell are a function of flow rate and, in contrast to an autocrine or paracrine signaling stimulus, independent of cell density. Shear stress has long been known to play a role in EC migration (3,(33)(34)(35)(36); however, in our system, cells are suspended in a 3D matrix, and the presence of this porous medium causes the force due to fluid pressure gradient across the cell to dominate the fluid shear force (37). By modeling a cell as a sphere embedded in a porous medium, we found the force due to the pressure drop across the cell (F pm ) relative to the shear stress imparted by the fluid (F s ) scales as…”

“…Pressure forces from flow past a cell in a 3D matrix lead to a transcellular stress gradient (37), and this stress results in asymmetric force in cell-matrix interactions-e.g., tensile force on the upstream side and compressive force on the downstream side. Previous work demonstrates that FAK colocalizes with activated integrins and activates Src kinase (28,29), which modulates traction forces important for tumor cell migration (43,44).…”

Three-Dimensional Characterization of Tissue-Engineered Constructs by Contrast-Enhanced Nanofocus Computed Tomography

“…Fluid flow is known to enhance matrix synthesis within TE constructs during perfusion culture. 19,40,50 Furthermore, differences in fibrillar collagen organization of the ECM, which are flow dependent, 51 could also explain the ECM differences that were observed by PTA staining as the ECM morphology could influence the binding mechanism of PTA to the ECM proteins. In Figure 5, it may also be observed that the difference in collagen content, as determined by Picrosirius Red staining, for the different flow rates is less pronounced than the one observed with the PTA staining.…”

Mechanotransduction of fluid stresses governs 3D cell migration

“…This elevated fluid pressure drives interstitial flow (IF) and alters chemical transport within the tumor (13), and IF influences tumor cell migration through the generation of autocrine chemokine gradients (14). Equally important, although not as well understood, is the physical drag imparted on the ECM and constitutive cells (15) by IF, which is analogous to the FA-activating shear stresses generated on endothelial cells by hemodynamic forces (16). With endothelial cells, shear stress can be the dominant mechanical stimulus that induces FAK activation and cytoskeletal remodeling; however, for cells embedded within a porous matrix scaffold, the ratio of the force due to the pressure drop across the cell to the total shear force is inversely proportional to hydrogel permeability (SI Appendix, Eq.…”