Smooth muscle cells freshly isolated from rat thoracic aortas are much stiffer than cultured bovine cells: Possible effect of phenotype

Tensile properties of rat aortic smooth muscle cells (RASMs) freshly isolated by enzymatic digestion were obtained under a physiological salt solution at 37 degreesC and compared with those of cultured bovine aortic smooth muscle cells (BASMs, P6-7). Overall elastic modulus of RASMs and BASMs were 9.3 +/- 2.8 kPa (mean +/- SEM, n = 8) and 1.5 +/- 0.2 kPa (n = 6), respectively under the strain rate of 0.2 - 4%/s. Due to the difference in the cell preparation method, RASMs and BASMs are considered to show contractile and synthetic phenotype, respectively. Contractile cells are much more abundant in myofilaments than synthetic cells. Myofilament bundles may be stiffer than other cellular components and extends throughout the cytoplasm. Contractile cells may thus be stiffer than synthetic cells. The difference in the mechanical properties of these cells may be due to the difference in the phenotype of the two cell specimens.