Effects of Constant Static Pressure on the Biological Properties of Porcine Aortic Valve Leaflets

Abstract

An understanding of how mechanical forces impact cells within valve leaflets would greatly benefit the development of a tissue-engineered heart valve. In this study, the effect of constant ambient pressure on the biological properties of heart valve leaflets was evaluated using a custom-designed pressure system. Native porcine aortic valve leaflets were exposed to static pressures of 100, 140, or 170 mmHg for 48 h. Collagen synthesis, DNA synthesis, sulfated glycoaminoglycan (sGAG) synthesis, alpha-SMC actin expression, and extracellular matrix (ECM) structure were examined. Results showed that elevated pressure caused an increase in collagen synthesis. This increase was not statistically significant at 100 mmHg, but at 140 mmHg and 170 mmHg collagen synthesis increased by 37.5 and 90%, respectively. No significant difference in DNA or sGAG synthesis was observed at elevated pressures, with the exception that DNA synthesis at 100 mmHg decreased. A notable decline in alpha-SMC actin was observed over the course of the experiments although no significant difference was observed between the pressure and control groups. It was concluded that elevated pressure caused a proportional increase in collagen synthesis of porcine aortic valve leaflets, but was unable to preserve alpha-SMC actin immunoreactive cells.

Synergistic effects of cyclic tension and transforming growth factor-β1 on the aortic valve myofibroblast

“…Therefore, the effects of cyclic tension were thought to be a major contributor in AVIC mechanobiological function. Previously, static pressure [28] and constant shear [29] of AVLs has been unable to maintain the SMA+ AVIC phenotype; hence, we sought to examine the cellular response due to circumferential cyclic tension in the physiologic range. As expected, SMA and Hsp47 levels of the Tension group at day 14 most resembled those of day 0 compared to the other treatment groups.…”

Normal Physiological Conditions Maintain the Biological Characteristics of Porcine Aortic Heart Valves: An Ex Vivo Organ Culture Study

“…5 Mechanical forces also modulate cell physiology and have been shown to affect the biosynthetic activity of cells in tissue matrices. 20,23 Porcine aortic valve ECs subjected to 20 dyne/cm 2 of steady laminar shear stress showed different organization of focal adhesion complexes and cell alignment than in static EC culture, suggesting that valvular ECs exhibit altered responses to mechanical forces. 1 In vivo studies using Wistar Kyoto rats with acute left ventricular pressure overload showed increased DNA synthesis and mRNA amounts of both collagen types I and III comparable to age-matched hypertensive rats.…”

Simplified Pulse Reactor for Real-Time Long-Term In Vitro Testing of Biological Heart Valves

“…35,36 In tissue engineered valve constructs, mechanical stimulation promotes cell differentiation and development of tissue mechanical properties. 2,16,20,30,40 Tissue engineered heart valves usually contain biocompatible or biodegradable scaffolds that are seeded and populated with cells of the future valve recipient to make it more compatible with the recipient's body than a conventional prosthetic valve or even exhibit self-regeneration and growth potential.…”