Stress fibers (SFs) in cells transmit external forces to cell nuclei, altering the DNA structure, gene expression, and cell activity. To determine whether SFs are involved in mechanosignal transduction upon intraluminal pressure, this study investigated the SF direction in smooth muscle cells (SMCs) in aortic tissue and strain in the SF direction. Aortic tissues were fixed under physiological pressure of 120 mmHg. First, we observed fluorescently labeled SFs using two-photon microscopy. It was revealed that SFs in the same smooth muscle layers were aligned in almost the same direction, and the absolute value of the alignment angle from the circumferential direction was 16.8° ± 5.2° (n = 96, mean ± SD). Second, we quantified the strain field in the aortic tissue in reference to photo-bleached markers. It was found in the radial-circumferential plane that the largest strain direction was − 21.3° ± 11.1°, and the zero normal strain direction was 28.1° ± 10.2°. Thus, the SFs in aortic SMCs were not in line with neither the largest strain direction nor the zero strain direction, although their orientation was relatively close to the zero strain direction. These results suggest that SFs in aortic SMCs undergo stretch, but not maximal and transmit the force to nuclei under intraluminal pressure.

细胞中的应力纤维 (SFs) 将外力传递到细胞核，改变 DNA 结构、基因表达和细胞活性。为了确定 SF 是否参与腔内压力下的机械信号转导，本研究调查了主动脉组织中平滑肌细胞 (SMC) 的 SF 方向和 SF 方向的应变。主动脉组织在120 mmHg的生理压力下固定。首先，我们使用双光子显微镜观察了荧光标记的 SF。结果表明，同一平滑肌层中的SFs几乎在同一方向排列，与圆周方向排列角度的绝对值为16.8°±5.2°（n = 96，平均值 ± SD）。其次，我们参考光漂白标记量化了主动脉组织中的应变场。发现在径向-圆周平面内，最大应变方向为-21.3°±11.1°，零法向应变方向为28.1°±10.2°。因此，主动脉 SMC 中的 SF 既不符合最大应变方向也不符合零应变方向，尽管它们的取向相对接近于零应变方向。这些结果表明主动脉 SMC 中的 SF 经历拉伸，但不是最大的，并且在腔内压力下将力传递到细胞核。