Ruumi Yamazaki, Koji Takahashi, Kaoru Sawasaki, Masanori Nakamura, Sota Kondo, Naoyuki Kimura, Koji Kawahito and Naoya Sakamoto : A synergistic effect of wall shear stress and impinging jet velocity on vascular endothelial cell morphology and actin cytoskeleton, Journal of Biorheology, 38, 2, 39-46, 2024.
Kaoru Sawasaki, Masanori Nakamura, Naoyuki Kimura, Koji Kawahito, Masashi Yamazaki, Hiromichi Fujie and Naoya Sakamoto : Endothelial-derived nitric oxide impacts vascular smooth muscle cell phenotypes under high wall shear stress condition, Biochemical and Biophysical Research Communications, 740, 151005, 2024.
(Summary)
The Phenotypic states of vascular smooth muscle cells (SMCs) are essential to understanding vascular pathophysiology. SMCs in vessels generally express a specific set of contractile proteins, but decreased contractile protein expression, indicating a phenotypic shift, is a hallmark of vascular diseases. Recent studies have suggested the relation of abnormally high wall shear stress (WSS) of approximately 20 Pa with the aortic disease pathogenesis. However, due to the lack of appropriate experimental models to assess SMC phenotypic states, the details of the phenotypic shift under high WSS conditions remain unclear. In this study, we developed a coculture model where vascular endothelial cells (ECs) were cocultured with SMCs expressing calponin 1, a contractile protein involved in the phenotypic shift of SMCs. We investigated the effects of a pathologically high WSS condition on the phenotypic states of SMCs. Increased calponin 1 expression was found upon exposure to 20 Pa WSS compared with a physiological 2 Pa condition, whereas the expression of another contractile protein, α-smooth muscle actin (αSMA) remained unchanged. Furthermore, the inhibition of EC-derived nitric oxide (NO), which is associated with endothelial dysfunction in vascular diseases, resulted in a trend of decreasing αSMA and Calponin 1 expression under 20 Pa WSS conditions compared with 2 Pa. Our findings suggest that EC-derived NO under pathologically high WSS conditions may impact the expression of contractile proteins implicated in aortic pathophysiology.
Kaoru Sawasaki, Masanori Nakamura, Shuta Imada, Yuta Horie, Koji Takahashi, Ruumi Yamazaki, Naoyuki Kimura, Koji Kawahito and Naoya Sakamoto : Disruptive effect of impinging jet flow environment on the integrity of endothelial monolayer, Journal of Biorheology, 37, 2, 130-137, 2023.
Yuya Hiroshima, Yuki Oyama, Kaoru Sawasaki, Masanori Nakamura, Naoyuki Kimura, Koji Kawahito, Hiromichi Fujie and Naoya Sakamoto : A Compressed Collagen Construct for Studying Endothelial-Smooth Muscle Cell Interaction Under High Shear Stress, Annals of Biomedical Engineering, 50, 8, 951-963, 2022.
(Summary)
The coculture of vascular endothelial cells (ECs) on collagen gels containing smooth muscle cells (SMCs) has been carried out to investigate cellular interactions associated with blood vessel pathophysiology under wall shear stress (WSS) conditions. However, due to a lack of gel stiffness, the previous collagen gel coculture constructs are difficult to use for pathologic higher WSS conditions. Here, we newly constructed a coculture model with centrifugally compressed cell-collagen combined construct (C6), which withstands higher WSS conditions. The elastic modulus of C6 was approximately 6 times higher than that of the uncompressed collagen construct. The level of α-smooth muscle actin, a contractile SMC phenotype marker observed in healthy arteries, was elevated in C6 compared with that of the uncompressed construct, and further increased by exposure to a physiological level WSS of 2 Pa, but not by a pathological level of 20 Pa. WSS conditions of 2 and 20 Pa also induced different expression ratios of matrix metalloproteinases and their inhibitors in the C6 coculture model but did not in monocultured ECs and SMCs. The C6 coculture model will be a powerful tool to investigate interactions between ECs and SMCs under pathologically high WSS conditions.
Shingo Tsukamoto, Hwee Keng Chiam, Takumi Asakawa, Kaoru Sawasaki, Naoyuki Takesue and Naoya Sakamoto : Compressive forces driven by lateral actin fibers are a key to the nuclear deformation under uniaxial cell-substrate stretching, Biochemical and Biophysical Research Communications, 597, 37-43, 2022.
(Summary)
Cells sense the direction of mechanical stimuli including substrate stretching and show morphological and functional responses. The nuclear deformation with respect to the direction of mechanical stimuli is thought of as a vital factor in mechanosensitive intracellular signaling and gene transcription, but the detailed relationship between the direction of stimuli and nuclear deformation behavior is not fully solved yet. Here, we assessed the role of actin cytoskeletons in nuclear deformation caused by cell substrate stretching with different directions. Cells on a PDMS stretching chamber were subjected to a step-strain and changes of long- and short-axes of nucleus before and after stretching were evaluated in terms of nuclear orientation against the direction of stretching. Nuclei oriented parallel to the stretching direction showed elongation and shrinkage in the long and short axes, respectively, and vice versa. However, calculation of the aspect ratio (ratio of long- and short-axes) changes revealed orientation-depend nuclear deformation: The nucleus oriented parallel to the stretching direction showed a greater aspect ratio change than it aligned in the perpendicular direction of the stretching. A decrease in actin cytoskeletal tension significantly changed the nuclear deformation only in the short axis direction, thereby abolishing the orientation-depend deformation of the nucleus. These results suggest that lateral compressive forces exerted by the actin cytoskeleton is a key factor of orientation-depend deformation in short axis of the nucleus under the cell-substrate stretching condition, and may be crucial for mechano-sensing and responses to the cell-substrate stretching direction.