High magnitude, in vitro, biaxial, cyclic tensile strain induces actin depolymerization in tendon cells - PubMed (original) (raw)

eCollection 2015 Apr-Jun.

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High magnitude, in vitro, biaxial, cyclic tensile strain induces actin depolymerization in tendon cells

Michael Lavagnino et al. Muscles Ligaments Tendons J. 2015.

Abstract

Background: the cytoskeleton is a dynamic arrangement of actin filaments that maintain cell shape and are vital in mediating the mechanobiological response of the cell.

Methods: to determine the cytoskeletal response to varying in vitro, biaxial stretch amplitudes, rat-tail tendon cells were paired into control and cyclically strained groups of 4.75, 9.5, or 12% strain at 1 Hz for 2 hours and the actin cytoskeleton stained. The cells were analyzed for actin staining intensity as a measure of relative depolymerization and for cell shape. Collagenase gene expression was measured in cells undergoing 12% cyclic strain at 1 Hz for 24 hours.

Results: there was no significant difference in the degree of actin staining intensity between the control group and cells strained at either 4.75 or 9.5%. However, cells strained at 12% demonstrated a significant decrease in actin staining intensity (depolymerization) compared to control cells, increased collagenase expression by 81%, and a clear shift towards a more rounded cell shape.

Conclusion: the results of this study demonstrate that the previously reported induction of collagenase activity associated with the application of high magnitude, in vitro, tensile strains may actually be a result of cytoskeletal depolymerization, which causes loss of tensional homeostasis and alteration of cell shape.

Keywords: actin intensity; cell shape; collagenase; mechanobiology; tendinopathy; under-stimulation.

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Figures

Figure 1

Figure 1

Histogram of percentage of cells within each cell conformation range for 15% strain as well as control cells. A cell conformation of 1 corresponds to a round cell while higher values correspond to more elongate cells.

Figure 2

Figure 2

Representative photomicrographs of an elongate cell with intense fluorescence of actin stress fibers in the control group (A) and a round cell with less intense staining of the actin stress fibers in the 15% strain group (B).

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