Effects of Cyclic Stretch Waveform on Endothelial Cell Morphology Using Fractal Analysis

Abstract

Endothelial cells are remodeled when subjected to cyclic loading. Previous in vitro studies have indicated that frequency, strain amplitude, and duration are determinants of endothelial cell morphology, when cells are subjected to cyclic strain. In addition to those parameters, the current study investigated the effects of strain waveform on morphology of cultured endothelial cells quantified by fractal and topological analyses. Cultured endothelial cells were subjected to cyclic stretch by a designed device, and cellular images before and after tests were obtained. Fractal and topological parameters were calculated by development of an image-processing code. Tests were performed for different load waveforms. Results indicated cellular alignment by application of cyclic stretch. By alteration of load waveform, statistically significant differences between cell morphology of test groups were observed. Such differences are more prominent when load cycles are elevated. The endothelial cell remodeling was optimized when the applied cyclic load waveform was similar to blood pressure waveform. Effects of load waveform on cell morphology are influenced by alterations in load amplitude and frequency. It is concluded that load waveform is a determinant of endothelial morphology in addition to amplitude and frequency, and such effect is elevated by increase of load cycles. Due to high correlation between fractal and topological analyses, it is recommended that fractal analysis can be used as a proper method for evaluation of alteration in cell morphology and tissue structure caused by application of external stimuli such as mechanical loading.

Relationship Between Cell Compatibility and Elastic Modulus of Silicone Rubber/Organoclay Nanobiocomposites

“…It has been shown that inorganic nanofillers have higher surface energy than polymer matrix (19). Silicone rubber is hydrophobic due to the presence of methyl groups, hence PDMS is considered as a low surface energy polymer (21). Increasing in OMMT leads to the rise of free surface energy by mechanism of enhancing surface roughness (22).…”

“…To study cell morphology on membranes, the samples were placed firstly in a culture plate and 5 x 10 3 HUVECs with culture medium were added to each well. Subsequently, cells-included culture plate was incubated at 37°C in a CO 2 incubator to adhere cells to the membranes after whichseveral images were captured via inverted microscope (Zeiss, Germany) overnight (21). Cell proliferation was analyzed taking advantage of MTT (3-[4, 5-dimethyltriazol-2-y1]-2, 5-diphenyl tretrazolium bromide) ().…”

Mechanical Stretching for Tissue Engineering: Two-Dimensional and Three-Dimensional Constructs

“…The 2D stretch study using human umbilical vein endothelial cells showed an intriguing observation that the asymmetric load waveform, which mimics the blood pressure wave by applying the velocity of extension to be greater than that of the release, induced most optimized endothelial remodeling. 55 This was assessed by spindle-shaped cell morphology and increased cell orientation relative to symmetric load waveform data. Thus, establishing biomimicking stretch conditions with respect to strain rate and frequency would be beneficial for mechanical tissue regeneration.…”

“…51 Stretch parameters, such as stretching mode (uniaxial, biaxial, and equiaxial), magnitude of strain, strain rate, frequency, stretch waveform (sinusoidal, ramp, and static), and insertion of rest periods, have been found to induce significant cell regulatory effects. [52][53][54][55][56][57][58] These parameters have been studied vigorously in 2D, but relatively less systematic studies on these parameters as applied for the tissue engineering of 3D tissues have been done. This section reviews findings on 2D stretching that may be leveraged to engineer better tissues, and then highlights current 3D stretch studies.…”

Overcoming physical constraints in bone engineering: ‘the importance of being vascularized’

“…These cells are physiologically subjected to unique mechanical stimuli consisting of flow-induced shear stress and tensile strain due to distension and stretching of the tissues. Under cyclic stretch, vascular ECs increase stress filament area in response to shear stress and regulate autocrine and paracrine signaling for angiogenesis and endothelial remodeling (Chien, 2007;Haghighipour, Tafazzoli-Shadpour, Shokrgozar, & Amini, 2010;Yung, Chae, Buehler, Hunter, & Mooney, 2009). Cyclic stretch, shear stress, and pressure on mesenchymal stem cells (MSCs) produce significant differences in cell morphology and lineage specification (Maul, Chew, Nieponice, & Vorp, 2011).…”