RESUMEN
Mechanical properties, along with biochemical and molecular properties, play crucial roles in governing cellular function and homeostasis. Cellular mechanics are influenced by various factors, including physiological and pathological states, making them potential biomarkers for diseases and aging. While several methods such as AFM, particle-tracking microrheology, optical tweezers/stretching, magnetic tweezers/twisting cytometry, microfluidics, and micropipette aspiration have been widely utilized to measure the mechanical properties of single cells, our understanding of how aging affects these properties remains limited. To fill this knowledge gap, we provide a brief overview of the commonly used methods to measure single-cell mechanical properties. We then delve into the effects of aging on the mechanical properties of different cell types. Finally, we discuss the importance of studying cellular viscous and viscoelastic properties as well as aging induced by different stressors to gain a deeper understanding of the aging process and aging-related diseases.
RESUMEN
Ventricle dysfunction is the most common cause of heart failure, which leads to high mortality and morbidity. The mechanical behavior of the ventricle is critical to its physiological function. It is known that the ventricle is anisotropic and viscoelastic. However, the understanding of ventricular viscoelasticity is much less than that of its elasticity. Moreover, the left and right ventricles (LV&RV) are different in embryologic origin, anatomy, and function, but whether they distinguish in viscoelastic properties is unclear. We hypothesized that passive viscoelasticity is different between healthy LVs and RVs. Ex vivo cyclic biaxial tensile mechanical tests (1, 0.1, 0.01 Hz) and stress relaxation (strain of 3, 6, 9, 12, 15%) were performed for ventricles from healthy adult sheep. Outflow track direction was defined as the longitudinal direction. Hysteresis stress-strain loops and stress relaxation curves were obtained to quantify the viscoelastic properties. We found that the RV had more pronounced frequency-dependent viscoelastic changes than the LV. Under the physiological frequency (1 Hz), the LV was more anisotropic in the elasticity and stiffer than the RV in both directions, whereas the RV was more anisotropic in the viscosity and more viscous than the LV in the longitudinal direction. The LV was quasi-linear viscoelastic in the longitudinal but not circumferential direction, and the RV was nonlinear viscoelastic in both directions. This study is the first to investigate passive viscoelastic differences in healthy LVs and RVs, and the findings will deepen the understanding of biomechanical mechanisms of ventricular function.
