Continuous stretching of whole murine aortic rings yielded significantly higher collagen stiffness compared to discontinuous stretching (192.3 vs 89.9 N/m; p<0.01).
A novel automated continuous stretching device significantly reduces measurement time and prevents hysteretic force loss, revealing higher collagen stiffness in murine aortas compared to traditional discontinuous methods.
Absolute Event Rate: 192.3% vs 89.9%
p-value: p=<0.01
The aorta exhibits low stiffness in youth, acting as a secondary pump to convert pulsatile flow from the heart into continuous flow. Elastin degradation, collagen deposition, and smooth muscle hypertrophy with aging contribute to aortic stiffening. When an aorta is stretched it exhibits a bilinear increase in force, demonstrated by small increases in force at the onset of stretch and large increases in force near the aorta rupture point. The aorta is composed of layers, with the medial and external layers generating force when stretched. The medial layer contains collagen, elastin, and smooth muscle cells and generates most of the force, while the external layer contains collagen and contributes less force. In recent years, aortic stiffness has been measured by mounting aortic rings on a pin myograph and uniaxially stretching the rings until rupture. A limitation of this technique is that it is performed by discontinuously stretching rings by 50 µm every 3 min until rupture, with rupture occurring at ~2,000 µm of stretch. Discontinuous stretching is required because after each stretch the force generated demonstrates hysteretic force loss until reaching a stable value 2+ hours to perform this technique. Our laboratory recently developed an automated device that is retrofitted to a pin myograph and stretches aortic rings at a continuous rate of 500 µm/min, reducing the time to perform this measurement to 0.05) and in medial-only rings (discontinuous: 10.3±0.4 vs. continuous: 10.9±0.5 N/m, p>0.05). Elastin stiffness of whole and medial-only rings was similar within techniques (p>0.05). Collagen stiffness was lower using the discontinuous vs. continuous technique in whole rings (discontinuous: 89.9±5.7 vs. continuous: 192.3±23.5 N/m, p< 0.01) and in medial-only rings (discontinuous: 72.7±11.1 vs. continuous: 126.8±14.1 N/m, p< 0.01). Collagen stiffness tended to be greater in whole rings vs. medial-only rings using the discontinuous technique (p=0.10) but was only statistically greater in whole rings vs. medial-only rings using the continuous technique (p< 0.05). In summary, elastin stiffness was similar between techniques and ring preparations, while collagen stiffness differed between techniques and ring preparations. Hysteretic force loss with discontinuous stretching was likely responsible for differences in collagen stiffness between techniques, which may explain why collagen stiffness was not greater in whole rings vs. medial-only rings using the discontinuous technique. Future studies are warranted to further validate the continuous technique in advanced age and other conditions with aortic stiffening. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Friberg et al. (Fri,) conducted a other in Aortic stiffness (n=5). Continuous stretching technique vs. Discontinuous stretching technique was evaluated on Collagen stiffness in whole aortic rings (N/m) (p=<0.01). Continuous stretching of whole murine aortic rings yielded significantly higher collagen stiffness compared to discontinuous stretching (192.3 vs 89.9 N/m; p<0.01).
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