Device for the application of a dynamic biaxially uniform and isotropic strain to a flexible cell culture membrane

Abstract

A large number of studies have demonstrated that mechanical perturbation modulates cellular metabolism; however, the systematic characterization of the molecular and cellular transduction mechanisms underlying mechanically induced metabolic modulation has been impeded, in part, by the limitations of the mechanical device. The objective of this investigation was to develop an in vitro experimental system that would provide independent control of the spatial and temporal biaxial strain distribution imposed on a flexible transparent tissue culture membrane that permits attachment, proliferation, and maintenance of the phenotypic expression of cultured embryonic osteoblasts. Such a device would permit a systematic investigation of the cellular response to specific, independently controlled parameters of mechanical deformation. Using a prototype device designed to impose a dynamic sinusoidal spatially isotropic biaxial strain profile, we confirmed experimentally that the strain was biaxially uniform and isotropic (radial = circumferential strain over the entire culture membrane) to within 14% (SD/mean) for the range of the peak strains tested (2.3-9.4%). Additionally, the uniformity was maintained at 1 Hz for at least 5 days of continuous operation. This experimental verification of the theoretically predicted isotropic strain profile suggests that the design principle is sound. Embryonic osteoblasts cultured on the flexible substrate proliferated and exhibited a temporal pattern of phenotypic expression (extracellular matrix accumulation and mineralization) comparable with that observed on polystyrene of tissue culture grade.

Small Mechanical Strains Selectively Suppress Matrix Metalloproteinase-1 Expression by Human Vascular Smooth Muscle Cells

“…This device provides a nearly homogeneous biaxial strain profile, i.e. strains that are equal at all locations on the membrane and in all directions (21). An advantage of this device over some commonly used systems is that it eliminates locations on the substrate that have very high strains (20 -30%) in one direction.…”

“…In many other types of cell-stretching devices, regions of the cell culture substrate have very high strains compared with the mean strain. For example, in one commonly used device, the strain can range from 0 to 33% depending on the location and orientation of the cell (21). We have previously demonstrated that cellular injury and fibroblast growth factor-2 release occur only when VSMCs are exposed to membrane strains higher than 10% (22).…”

Myocardial Fibrosis in Chronic Aortic Regurgitation

“…20 Cells grown on flexible, collagen-coated membranes were exposed continuously to 60 cycle/min equibiaxial stretching (maximalϭ25%, modeling diastolic strain of AR; minimal stretchϭ10%, modeling systolic strain of AR) for 4 days. Strains were those expected at LV midwall with LV dimensions and pressures typically seen in our rabbits with severe, chronic AR, derived from our validated LV wall stress model.…”

Mechanisms of Mechano-Transduction within Osteoblasts

“…These cells were plated at a density of 2 x 10 6 cells in 100 mm tissue culture dishes coated either with purified FN (lmg/ml) as previously described (Schaffer et al, 1994) or uncoated plates. Cultures were grown for two weeks until they reached confluence in minimum essential media supplemented with 10% fetal bovine serum (FBS).…”