Structural Integrity and Cellular Viability of Cryopreserved Allograft Heart Valves in Right Ventricular Outflow Tract Reconstruction: Correlation of Histopathological Changes with Donor Characteristics and Preservation Times

Abstract

Introduction Cryopreserved allograft heart valves (CAHV) show longer event-free survival compared to other types of protheses. However, all patients develop early and/or late allograft failure. Negative predictors are clinical, and there is a lack of evidence whether they correspond with the microscopic structure of CAHV. We assessed histopathological signs of structural degeneration, degree of cellular preservation, and presence of antigen-presenting cells (APC) in CAHV and correlated the changes with donor clinical characteristics, cryopreservation times, and CAHV types and diameters. Methods Fifty-seven CAHV (48 pulmonary, nine aortic) used for transplantation between November/2017 and May/2019 were included. Donor variables were age, gender, blood group, height, weight, and body surface area (BSA). Types and diameters of CAHV, cold ischemia time, period from decontamination to cryopreservation, and cryopreservation time were recorded. During surgery, arterial wall (n=56) and valvar cusp (n=20) samples were obtained from the CAHV and subjected to microscopy. Microscopic structure was assessed using basic staining methods and immunohistochemistry (IHC). Results Most of the samples showed signs of degeneration, usually of mild degree, and markedly reduced cellular preservation, more pronounced in aortic CAHV, correlating with arterial APC counts in both basic staining and IHC. There was also a correlation between the degree of degeneration of arterial samples and age, height, weight, and BSA of the donors. These findings were independent of preservation times. Conclusion CAHV show markedly reduced cellular preservation negatively correlating with the numbers of APC. More preserved CAHV may be therefore prone to stronger immune rejection.

Preservation of human heart valves for replacement in children with heart valve disease: past, present and future

“…Of note, the difference between cryopreservation and cold static storage at 4 °C might be insignificant if cryopreservation is preceded with a long period of storage at 4 °C. To illustrate, this was reported to be the case in a recent study with a period of up to 28 days of storage at 4 °C before cryopreservation (Fabian, et al 2022 ). Despite the inconsistencies in literature regarding differences in cryopreserved or fresh valves, it is important to note that neither short-term cold static storage at 4 °C nor cryopreservation leads to the implantation of viable valves with growth potential.…”

“…DMEM or RPMI-1640 media supplemented with foetal calf serum or HEPES (Lang et al 1994 ; Gerson et al 2009 )) although most studies do not report the preservation solutions used. It is important to note that valves preserved via this method are named “fresh valves” in literature (Schenke-Layland et al 2006 ; Fabian, et al 2022 ; Koolbergen et al 2002 ), (O’Brien et al 1987 ) despite the frequently observed loss of valve viability and loss of valve functionality compared to valves directly after extraction (Burkert et al 2008 ). Therefore, we believe that preservation at 4 °C for periods up to 95 days is unlikely to reflect the functionality and viability of fresh valves.…”

“…1 B, C). It has been proposed that the methods used to preserve and sterilize allograft valves cause loss of the valvular endothelium (Fabian, et al 2022 ; Krs et al 2004 ). Increasing the abundance and viability of VECs is considered an important step to increase durability of valve allografts after transplantation.…”

“…Remodelling of the valve ECM as a consequence of altered mechanical loading (Pant et al 2018 ) or post-natal valve stratification (Hulin et al 2019 ) is mediated by VECs and VICs and essential to maintain valve function throughout the millions of cycles during life of valve opening and closing (Kodigepalli et al 2020 ). The valvular ECM has been the base for valve tissue engineering approaches and loss of valve ECM integrity in allograft valves negatively impacts durability (Schenke-Layland et al 2006 ; Fabian, et al 2022 ). The loss of cellularity of allograft valves have led to the notion that allograft valves, as they are currently preserved, function as natural scaffolds to serve as a template for cellular attachment of circulating endogenous cells (Mendelson and Schoen 2006 ).…”

Impact of prolonged storage time on homograft ultrastructures: an attempt to find optimal guidelines for homograft processing

“…Collagen degeneration signs have previously been shown in vascular diseases such as aortic aneurysm and hypertension, and consist of increased waviness and disrupted fiber orientation, as well as disrupted D-bands with reduced contrast (Jones et al 2020 ). So far, studies have shown that mechanical and morphological properties of the extracellular matrix of the homograft vessel walls and cusps seem to keep intact after prolonged cold ischemic time prior to organ harvest (Smit et al 2015 ; Bester et al 2018 ; Fabian et al 2022 ). Forensic studies have shown that tissues with extracellular matrix that is rich in collagen and/or elastin, such as blood vessels, are resistant to both autolytic degeneration and microbiological decomposition and that adequate cooling slow the process even further (Cocariu et al 2016 ; Javan et al 2019 ).…”