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

Abstract

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 cusp, 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.

X-ray-Based 3D Histology of Murine Hearts Using Contrast-Enhanced Microfocus Computed Tomography (CECT) and Cryo-CECT

“…The important tissue shrinkage observed in the heart due to paraffin embedding (during which the biological samples are totally dehydrated to progressively replace the water content with liquid paraffin) could be avoided by using, for instance, cryostat sections, which do not involve paraffin embedding. However, this usually requires fine-tuning in order to avoid freezing damage (e.g., when and how to use cryoprotectant and an embedding matrix such as OCT and the selection of the freezing method) and results in poor structural preservation, such as ruptures and cracks [37][38][39][40]. These results are added to the well-known limitations of classical 2D histology, namely, the irreversible cut performed in the sample along with a single cutting orientation and an anisotropic voxel size (in the rare case that serial sections were successfully obtained).…”

Perspective Chapter: Role of Frozen Allografts in Aortic Valve Surgery

“…It has been suggested, that fresh wet storage of AVA may accelerate calcification [52]. Decellularized heart valves, frozen without protection, presented porosity of histoarchitecture, altering biomechanics; sucrose reduced or diminished its formation [53].…”