Adaptive Changes in Cardiac Fibroblast Morphology and Collagen Organization as a Result of Mechanical Environment

Abstract

There is a growing body of work in the literature that demonstrates the significant differences between 2D versus 3D environments in cell morphologies, spatial organization, cell-ECM interactions, and cell signaling. The 3D environments are generally considered more realistic tissue models both because they offer cells a surrounding environment rather than just a planar surface with which to interact, and because they provide the potential for more diverse mechanical environments. Many studies have examined cellular-mediated contraction of 3D matrices; however, because the 3D environment is much more complex and the scale more difficult to study, little is known regarding how mechanical environment, cell and collagen architecture, and collagen remodeling are linked. In the current work, we examine the spatial arrangement of neonatal cardiac fibroblasts and the associated collagen organization in constrained and unconstrained collagen gels over a 24 h period. Collagen gels that are constrained by their physical attachment to a mold and similar gels, which have been detached (unconstrained) from the mold and subsequently contract, offer two simple mechanical models by which the mechanisms of tissue homeostasis and wound repair might be examined. Our observations suggest the presence of two mechanical regimes in the unconstrained gels: an outer ring where cells orient circumferentially and local collagen aligns with the elongated cells; and a central region where unaligned stellate/bipolar cells are radially surrounded by collagen, similar to that seen throughout constrained gels. The evolving organization of cell alignment and surrounding collagen organization suggests that cellular response may be due to the cellular perception of the apparent stiffness of local physical environment.

Type II diabetes promotes a myofibroblast phenotype in cardiac fibroblasts

“…The collagen gel contraction assay is a well accepted system for studying the remodeling behavior of cells and has been used to assess the role of a variety of factors, including growth factors, mechanical environment and cell surface receptors, in mediating cellular response to an in vivo like collagen environment (Dallon and Ehrlich, 2008; Baxter et al, 2008; Grinnell, 2000; Carver et al, 1995). As shown in Fig.…”

Role of catch bonds in actomyosin mechanics and cell mechanosensitivity

“…The contraction of adherent cells is a phenomenon that plays a large role in many biological processes such as morphogenesis [1], wound contraction [2], stem cell differentiation [3], and the development of many diseases [4]. The molecular mechanisms by which cells generate motion and force depend on a series of highly coordinated events occurring in both the cytoskeleton and at the cell membrane.…”

Age-Dependent Expression of Collagen Receptors and Deformation of Type I Collagen Substrates by Rat Cardiac Fibroblasts

“…This may be explained in part by the differences in cell-ECM interactions reported to exist between 2D and 3D cell cultures (Cukierman et al, 2001); monolayer culture conditions do not appear to support the assembly of in vivo –like cell-ECM adhesions and may thus obscure differences in collagen contraction that are readily observed in 3D cultures. We have previously reported that peak strains within cardiac fibroblast-contracted 3D collagen gels approach −0.40 (i.e., 40% compression) (Baxter et al, 2008), whereas the peak strains in our monolayer cultures plateaued at ±~0.10. Age-related differences in contractility then may only emerge in the context of substrates mechanically permissive for greater deformation.…”