Cryopreserved human aortic root allografts arterial wall: Structural changes occurring during thawing.

Robert Novotny,Jaroslav Spatenka,Otakar Krs,Jan Burkert,Jaroslav Lindner,Pavel Mericka,Petr Mitas,Jaroslav Hlubocky,Dasa Slizova,Zuzana Hlubocka,Miroslav Spacek,Radovan Fiala,Alessandro Parolari

doi:10.1371/journal.pone.0175007

Abstract

BackgroundThe aim of our experimental work was to assess morphological changes of arterial wall that arise during different thawing protocols of a cryopreserved human aortic root allograft (CHARA) arterial wall.MethodsThe experiment was performed on CHARAs. Two thawing protocols were tested: 1, CHARAs were thawed at a room temperature at +23°C; 2, CHARAs were placed directly into a water bath at +37°C.Microscopic samples preparationAfter fixation, all samples were washed in distilled water for 5 min, and dehydrated in a graded ethanol series (70, 85, 95, and 100%) for 5 min at each level. The tissue samples were then immersed in 100% hexamethyldisilazane for 10 minutes and air dried in an exhaust hood at room temperature. Processed samples were mounted on stainless steel stubs, coated with gold.ResultsThawing protocol 1: All 6 (100%) samples showed loss of the endothelium and damage to the subendothelial layers with randomly dispersed circular defects and micro-fractures without smooth muscle cells contractions in the tunica media.Thawing protocol 2: All 6 (100%) samples showed loss of endothelium from the luminal surface, longitudinal corrugations in the direction of blood flow caused by smooth muscle cells contractions in the tunica media with frequent fractures in the subendothelial layerConclusionAll the samples thawed at the room temperature showed smaller structural damage to the CHARA arterial wall with no smooth muscle cell contraction in tunica media when compared to the samples thawed in a water bath.

Highlights

Cryopreserved aortic root allografts (CHARA) have been used extensively in cardiac surgery for their advantages over bioprosthetic and mechanical valves, such as excellent hemodynamic function, very low thrombotic event rates, and mainly their resistance toward infections [1,2,3].The era of allograft transplantation in cardiac surgery began after the first successful aortic valve transplantation performed by Ross in early 1962 based on Brewin experimental work [4,5]
All the samples thawed at the room temperature showed smaller structural damage to the cryopreserved human aortic root allograft (CHARA) arterial wall with no smooth muscle cell contraction in tunica media when compared to the samples thawed in a water bath
One of the most important experimental works performed by M’ Bengue-Gaye A et al on a rabbits carotid arteries clearly showed the effects of cryopreservation on allografts [12]

Summary

Introduction

Cryopreserved aortic root allografts (CHARA) have been used extensively in cardiac surgery for their advantages over bioprosthetic and mechanical valves, such as excellent hemodynamic function, very low thrombotic event rates, and mainly their resistance toward infections [1,2,3].The era of allograft transplantation in cardiac surgery began after the first successful aortic valve transplantation performed by Ross in early 1962 based on Brewin experimental work [4,5]. The first allograft transplants in cardiac surgery were freshly harvested aortic valves that underwent minimal treatment with no ABO Blood group matching These allograft transplants showed outstanding durability and performance, giving the basic foundation for this new type of surgical procedures. Due to do the lack of donors, cardiac centers started to treat allografts with antibiotics in order to prevent disease transmission, and cryopreserve them in order to prolong their life span. These techniques of allograft processing and cryopreservation led to significant decrease of allografts durability and their clinical performance between 1960s and early 1970s leading almost to the abandonment of this type of procedures [6]. The aim of our experimental work was to assess morphological changes of arterial wall that arise during different thawing protocols of a cryopreserved human aortic root allograft (CHARA) arterial wall

Methods

Results

Conclusion