Balanced mechanical forces and microtubule contribution to fibroblast contraction

Abstract

Fibroblast locomotion is thought to generate tractional forces which lead to contraction and reorganisation of collagen in tissue development and repair. A culture force monitor device (CFM) was used to measure changes in force in fibroblast populated collagen lattices, which resulted from cytoskeletal reorganisation by cytochalasin B, colchicine, vinblastine, and taxol. Microfilament disruption abolished contraction forces, microtubule disruption elicited a new peak of contraction, while taxol stabilisation of microtubules produced a gradual fall in measured force across the collagen gel. Based on these measurements, it is suggested that the cell can be viewed as an engineering structure in which residual intracellular forces, from contractile microfilaments, exert compressive loading on microtubular elements. This microtubular structure appears to act as a "balanced space frame" (analogous to an aeroplane chassis), maintaining cell shape and consequently storing a residual internal tension (RIT). In dermal fibroblasts this hidden RIT was up to 33% of the measurable force exerted on the collagen gel. Phenotypic differences between space frame organisation and RIT levels could explain site and pathological variations in fibroblast contraction.

Microtubule function in fibroblast spreading is modulated according to the tension state of cell–matrix interactions

“…Either nocodazole or taxol blocked formation of fibroblast dendritic extensions in relaxed collagen matrices, which was important because nocodazole might have interfered with extensions by stimulating fibroblast contraction (25,26). Taxol, on the other hand, can block microtubule dynamics (27,28) without simultaneously increasing cell contraction (25,26).…”

“…Taxol, on the other hand, can block microtubule dynamics (27,28) without simultaneously increasing cell contraction (25,26). Also, microtubules were required for fibroblast spreading in relaxed collagen matrices regardless of whether cells were stimulated with PDGF or LPA.…”

GEF-H1 Couples Nocodazole-induced Microtubule Disassembly to Cell Contractility via RhoA

“…Although microtubules themselves do not generate contractile forces, it has been noticed that microtubule depolymerization induces the formation of actin stress fibers and cell contraction (Danowski, 1989;Brown et al, 1996;Verin et al, 2001;Birukova et al, 2004b). However, in spite of the apparent universality of this phenomenon, the molecular basis by which microtubule disassembly stimulates cell contractility is not clearly established.…”

Stiffening of Human Skin Fibroblasts with Age

“…This is not surprising, since active and passive cellular biomechanics based on the stability provided by the cytoskeleton impacts many essential cellular functions. In addition to the role of the cytoskeleton in cellular motility and division (11,12), it has been shown that a functionally intact cytoskeleton is crucial to build up contraction forces in a three-dimensional collagen lattice (13,14). These cell functions are essential for the homeostasis of the extracellular matrix (ECM).…”

“…In vivo, there are many cells able to perform mechanical work, for example, muscle cells or cells of connective tissues that are connected to the proteins of the ECM. Three-dimensional collagen lattices seeded with fibroblasts have been used to analyze the effect of actin or microtubule disruption on the mechanical activity of cells (13,14). The mechanical properties of cells and the state of the cytoskeleton affect the interaction between fibroblasts and the ECM (30)(31)(32), so mechanical changes may reveal new aspects of the age-related degradation of the elastic properties of the dermis.…”