Use of sucrose to diminish pore formation in freeze-dried heart valves

Andrés Vásquez-Rivera, Harriëtte Oldenhof, Daniele Dipresa, Tobias Goecke, Artemis Kouvaka, Fabian Will, Axel Haverich, Sotirios Korossis, Andres Hilfiker, Willem F. Wolkers
2018 Scientific Reports  
Freeze-dried storage of decellularized heart valves provides easy storage and transport for clinical use. Freeze-drying without protectants, however, results in a disrupted histoarchitecture after rehydration. In this study, heart valves were incubated in solutions of various sucrose concentrations and subsequently freeze-dried. Porosity of rehydrated valves was determined from histological images. In the absence of sucrose, freeze-dried valves were shown to have pores after rehydration in the
more » ... usp, artery and muscle sections. Use of sucrose reduced pore formation in a dose-dependent manner, and pretreatment of the valves in a 40% (w/v) sucrose solution prior to freeze-drying was found to be sufficient to completely diminish pore formation. The presence of pores in freeze-dried valves was found to coincide with altered biomechanical characteristics, whereas biomechanical parameters of valves freeze-dried with enough sucrose were not significantly different from those of valves not exposed to freeze-drying. Multiphoton imaging, Fourier transform infrared spectroscopy, and differential scanning calorimetry studies revealed that matrix proteins (i.e. collagen and elastin) were not affected by freeze-drying. Heart valve diseases are one of the main causes of death worldwide and represent an increasing problem in medical practice 1 . Currently, heart valve dysfunction is typically treated via replacement with mechanical or biological prostheses. Risks associated with mechanical valves include hemorrhage and thromboembolism 2 . Bioprosthetic valves are made by treating bovine or porcine tissue with glutaraldehyde. These glutaraldehyde-treated tissue matrices are inherently different from native matrices because proteins are irreversibly cross-linked 3 . Bioprosthetic valves have been implicated in fibrosis, calcification, degeneration and immunogenic complications 4 . Decellularized heart valves hold promise as alternative for mechanical or bioprosthetic valves. The histoarchitecture of decellularized heart valves closely resembles that of native tissue, and implanted valves have been shown to be repopulated with autologous cells resulting in tissue regeneration and growth 5 . The use of decellularized heart valves to replace a malfunctioning heart valve reduces the risk of immunogenic rejection, whereas anti-coagulation therapy is generally not required 6 . In the surgical practice, sufficient availability of decellularized heart valves of different sizes is required. To satisfy this demand, appropriate preservation methods are needed to preserve valves until they are required. If it were possible to dry heart valves without damaging the tissue, this would increase their shelf-life and ensure off-the-shelf availability, while decreasing the incidence of bacterial contamination. Freeze-drying allows for easy transport and room temperature storage. Biological materials are generally prone to degradation, particularly when they are immersed in water and at higher temperatures. Previous studies have shown that heart valves can be stored at 4 °C in 50-80% sucrose solutions or in pure glycerol for up to 52 and 12 weeks, respectively 6,7 . However, stored samples showed separation and clumping of collagen as well as changes in microscopic structure and elastic properties. Moreover, valves that are stored in liquid have an increased risk of bacterial contamination during prolonged storage. These
doi:10.1038/s41598-018-31388-4 pmid:30154529 fatcat:jh5iftb7nnbsxddc5suhwmln44