The effects of collagenase on the critical buckling pressure of arteries

The stability of arteries is essential to normal arterial functions and loss of stability can lead to arterial tortuosity and kinking. Tortuous arteries are often associated with hypertension, atherosclerosis, and aging. Collagen is a main extracellular matrix component that modulates the mechanical behavior of arteries. The degradation of collagen and deposition occur in pathological conditions and it is known that collagen degradation weakens the mechanical strength of arteries. However, the effect of collagen degradation on the mechanical stability of arteries is unclear. The objective of this study was to investigate the effects of collagen degradation on the critical buckling pressure of arteries. Arterial specimens were subjected to pressurized inflation testing to obtain their length and diameter deformations. The data was fitted utilizing theoretical equations for nonlinear thick-walled cylindrical model with the Fung strain energy function to obtain the stress strain relationship. The arteries were then tested for the critical buckling pressure at a set of axial stretch ratios. Then, arteries were divided into three groups and treated with Type III collagenase at three different concentrations (2000U, 640U, and 320U). Mechanical properties and buckling pressures of the arteries were determined after collagenase treatment. Additionally, the theoretical buckling pressures were determined using a buckling equation. Our results demonstrated that the buckling pressure for arteries was lower after collagenase treatment. The difference between pre- and post- treatment was statistically significant for the highest concentration of 2000U but not at the lower concentrations. The buckling equation was found to yield a fair estimation to the experimental critical pressure measurements. These results are useful in understanding the role of matrix remodeling on the mechanical stability of arteries and developments of tortuous arteries.