ABSTRACT
Objective To design a novel strain loading device for studying the mechanical biology of adherent cells. Methods Based on the technology of substrate deformation loading, the device adopted controllable stepper to cause deformation of the silastic chamber, so as to realize cell loading with multiple units and large strain. The device was developed to test its loading functions. The three-dimensional (3D) models of the silastic chamber were established to simulate the loaded chamber by the finite element technology, and uniformity of the strain field was analyzed. The device applied 5% strain to bone marrow stromal cells (BMSCs) with 0.5 Hz stretch frequency at 2 hours per day for 5 days, and an inverted phase contrast microscope was used to observe the morphology of BMSCs. Results The developed strain loading device for adherent cells in vitro could provide mechanical unidirectional strain up to 50% with three groups of cell loading substrates; within the 10% stain range, the area of uniform strain filed on the silastic chamber remained above 50%, which ensured that the cells were loaded evenly; the morphology of BMSCs was obviously altered, and the direction of arrangement tended to be perpendicular to the loading direction of principal strain. Conclusions The device shows the advantages of reliable operation, wide strain range, adjustable frequency and convenient operation. It can be used to load multiple cell culture substrates at the same time, which provides convenient conditions for the study of cell mechanobiology.
ABSTRACT
Objective To develop an in vitro vascular tensile stress loading device and study the distributions of tensile stress and tensile strain on the elastic basement membrane (silicone sheet). Method The in vitro vascular tensile stress loading device which simulated the human hemodynamic environment was developed based on the elastic basement membrane deformation loading technology. The images of grid points before and after the stretch of the silicon sheet were recorded by camera and transformed into the digital images. The characteristics for the location of the grid points were calculated by using Matlab software, so as to obtain the strain distribution on the silicon sheet. Experiments were conducted on the silicon sheet by using the universal material testing machine, so as to calculate the mechanical parameters of the silicon sheet. The finite element model was established according to the mechanical parameters, and the distribution of tensile stress and tensile strain on the silicon sheet was simulated and calculated. The experimental results and simulative results were then compared. Results The finite element results were basically in accordance with the experimental results. The maximum value of tensile stress and tensile strain appeared on the loading point, while the stress and strain in intermediate area were comparatively homogeneous. 60% of the intermediate area in the silicone sheet could be regarded as homogeneous strain fields Conclusions The research finding can provide experimental techniques for the dynamic culture of vascular endothelial cells and the research on cell mechanics in the future.
ABSTRACT
OBJECTIVE: To identify the effectiveness of a weight loading device as a method for assessment of unilateral knee pain. METHOD: Twenty-five patients with unilateral knee pain and 25 pain-free controls participated in this study. Patients with a score of 2 or more on modified Kellgren-Lawrence scale based on the radiologic findings were diagnosed as degenerative arthritis. We constructed a device of segmental foot plates with strain gauge weight sensors to measure the weight load of each leg during self-selected walking speed. Using this device, we obtained the ratio of symptomatic side to asymptomatic side of weight load (RATIO) for each patient. The degree of pain according to visual analogue scale (VAS), abnormalities in radiologic findings, and weight load ratio were compared with each other. RESULTS: The RATIO was 1.00+/-0.03 in the control group, and 0.92+/-0.08 in the patient group (p<0.05). In the patient group, there was a significant correlation between RATIO and the VAS score (r=-0.44, p=0.03). In the patient group with degenerative arthritis, the RATIO (p=0.75) and VAS (p=0.94) were not different from those in patient group without degenerative arthritis. CONCLUSION: The foot plate weight loading device may be an effective tool for convenient measurements of knee pain.