Frequency-modulated atomic force microscopy localises viscoelastic remodelling in the ageing sheep aorta

Area of Science:

• Biophysics
• Cardiovascular Research
• Materials Science

Background:

• Age-related aortic stiffening is a significant risk factor for cardiovascular diseases, including heart failure.
• The mechanical properties of aortic structural components like collagen and elastin are crucial for aortic function.
• Aberrant remodeling of these components with age necessitates precise characterization of micromechanical properties.

Purpose of the Study:

• To measure the micromechanical properties of the ascending aorta's medial layer in a sheep model of aging.
• To investigate age-related changes in the elastic and viscoelastic properties of the aortic medial lamellar unit.
• To demonstrate the utility of frequency-modulated atomic force microscopy (FM-AFM) for characterizing biological tissue biomechanics.

Main Methods:

• Utilized a novel, non-contact frequency-modulated atomic force microscopy (FM-AFM) technique operated at 30kHz.
• Applied FM-AFM in 'cantilever tune' mode on conventional AFM systems.
• Achieved a spatial resolution of approximately 1.6 microm(2) to analyze micromechanical properties in young (~18 months) and old (>8 years) female sheep aortas.

Main Results:

• Significant age-dependent alterations in elastic and viscoelastic properties were observed within the aortic medial lamellar unit.
• Elastic modulus (Young's modulus) increased significantly from 42.9 kPa in young sheep to 113.9 kPa in old sheep (P<0.0001).
• Storage modulus (G') and loss modulus (G″) also showed significant increases with age, consistent with previous Scanning Acoustic Microscopy (SAM) findings.

Conclusions:

• FM-AFM is a valuable, hardware-independent method for simultaneously assessing elastic and viscoelastic properties of biological tissues at the micrometer scale.
• Aging leads to substantial stiffening and altered viscoelasticity in the sheep aorta's medial layer.
• These findings highlight the potential of FM-AFM for understanding age-related cardiovascular changes and disease mechanisms.