Department of Thoracic and Cardiovascular Surgery, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany.
Department of Cardiothoracic Surgery, Royal Brompton and Harefield Foundation Trust, Harefield, UK.
Eur J Cardiothorac Surg. 2019 Mar 1;55(3):484-493. doi: 10.1093/ejcts/ezy292.
Frozen cryopreservation (FC) with the vapour phase of liquid nitrogen storage (-135°C) is a standard biobank technique to preserve allogeneic heart valves to enable a preferable allograft valve replacement in clinical settings. However, their long-term function is limited by immune responses, inflammation and structural degeneration. Ice-free cryopreserved (IFC) valves with warmer storage possibilities at -80°C showed better matrix preservation and decreased immunological response in preliminary short-term in vivo studies. Our study aimed to assess the prolonged performance of IFC allografts in an orthotopic pulmonary sheep model.
FC (n = 6) and IFC (n = 6) allografts were transplanted into juvenile Merino sheep. After 12 months of implantation, functionality testing via 2-dimensional echocardiography and histological analyses was performed. In addition, multiphoton autofluorescence imaging and Raman microspectroscopy analysis were applied to qualitatively and quantitatively assess the matrix integrity of the leaflets.
Six animals from the FC group and 5 animals from the IFC group were included in the analysis. Histological explant analysis showed early inflammation in the FC valves, whereas sustainable, fully functional, devitalized acellular IFC grafts were obtained. IFC valves showed excellent haemodynamic data with fewer gradients, no pulmonary regurgitation, no calcification and acellularity. Structural remodelling of the leaflet matrix structure was only detected in FC-treated tissue, whereas IFC valves maintained matrix integrity comparable to that of native controls. The collagen crimp period and amplitude and elastin structure were significantly different in the FC valve cusps compared to IFC and native cusps. Collagen fibres in the FC valves were less aligned and straightened.
IFC heart valves with good haemodynamic function, reduced immunogenicity and preserved matrix structures have the potential to overcome the known limitations of the clinically applied FC valve.
使用液氮蒸气相（-135°C）进行冷冻保存（FC）是一种标准的生物库技术，可用于保存同种异体心脏瓣膜，以便在临床环境中进行更优的同种异体瓣膜置换。然而，它们的长期功能受到免疫反应、炎症和结构退化的限制。无冰冷冻保存（IFC）的瓣膜在-80°C 下具有更温暖的储存可能性，在初步的短期体内研究中显示出更好的基质保存和降低的免疫反应。我们的研究旨在评估 IFC 同种异体移植物在原位肺绵羊模型中的长期性能。
将 FC（n=6）和 IFC（n=6）同种异体移植物移植到幼年美利奴绵羊体内。植入 12 个月后，通过二维超声心动图和组织学分析进行功能测试。此外，还应用多光子自发荧光成像和拉曼微光谱分析对瓣膜的基质完整性进行定性和定量评估。
FC 组有 6 只动物和 IFC 组有 5 只动物纳入分析。组织学分析显示，FC 瓣膜早期存在炎症，而获得的 IFC 移植物具有可持续的、完全功能的、失活的无细胞状态。IFC 瓣膜表现出优异的血液动力学数据，梯度较小，无肺反流，无钙化和无细胞性。仅在 FC 处理的组织中检测到瓣叶基质结构的结构重塑，而 IFC 瓣膜保持的基质完整性与天然对照相似。与 IFC 和天然瓣叶相比，FC 瓣叶的胶原卷曲周期和幅度以及弹性蛋白结构有显著差异。FC 瓣膜中的胶原纤维排列不规则，变直。
具有良好血液动力学功能、降低免疫原性和保留基质结构的 IFC 心脏瓣膜有可能克服临床应用的 FC 瓣膜的已知局限性。
