Analysis of Alterations in Morphologic Characteristics of Mesenchymal Stem Cells by Mechanical Stimulation during Differentiation into Smooth Muscle Cells

Objective: Mesenchymal stem cells (MSCs) can be expanded and differentiated into many mature cell types including smooth muscle cells (SMCs). In addition to growth fac- tor, cyclic stretch contributes to differentiation of stem cells. Mechanical stimuli are critical to morphological changes, development, regeneration, differentiation and pathology of mesenchymal tissues. The aim of this study is to investigate effects of cyclic stretch with differing amplitudes on morphology and differentiation of mesenchymal stem cells. Materials and Methods: Mesenchymal stem cells are extracted from human bone mar- row. Cells are cultured on silicone membrane and exposed to cyclic stretch by a custom made device. Cellular images are captured before and after tests. Effects of 5% and 15% uniaxial strain with 1Hz frequency and 1-8 hour durations on morphology of human mes- enchymal stem cells are investigated. It is assumed that environmental factors such as mechanical loading regulate MSCs differentiation to SMCs. Fractal analysis is used to quantify alterations in cellular morphology. An image processing method with a designed code is used for evaluation of fractal dimension parameter. Results: Results demonstrate statistically significant change in cell morphology due to mechanical stretch. By elevation of strain amplitude and number of load cycles, fractal dimensions of cell images decrease. Such decrease is equivalent to alignment of cells by mechanical stimulus. Cells are differentiated to SMCs purely by cyclic stretch. The initia- tion and rate of differentiation depend on mechanical conditions. Conclusion: To produce functional SMCs for engineered tissues, MSCs can be exposed to uni- axial cyclic stretch. The functionality of differentiated SMCs depends on loading conditions.