Impact of T-cell-mediated immune response on xenogeneic heart valve transplantation: Short-term success and mid-term failure

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Abstract

OBJECTIVES: Allogeneic frozen cryopreserved heart valves (allografts or homografts) are commonly used in clinical practice. A major obstacle for their application is the limited availability in particular for paediatrics. Allogeneic large animal studies revealed that alternative ice-free cryopreservation (IFC) results in better matrix preservation and reduced immunogenicity. The objective of this study was to evaluate xenogeneic (porcine) compared with allogeneic (ovine) IFC heart valves in a large animal study. METHODS: IFC xenografts and allografts were transplanted in 12 juvenile merino sheep for 1-12 weeks. Immunohistochemistry, ex vivo computed tomography scans and transforming growth Factor-Β release profiles were analysed to evaluate postimplantation immunopathology. In addition, near-infrared multiphoton imaging and Raman spectroscopy were employed to evaluate matrix integrity of the leaflets. RESULTS: Acellular leaflets were observed in both groups 1 week after implantation. Allogeneic leaflets remained acellular throughout the entire study. In contrast, xenogeneic valves were infiltrated with abundant T-cells and severely thickened over time. No collagen or elastin changes could be detected in either group using multiphoton imaging. Raman spectroscopy with principal component analysis focusing on matrix-specific peaks confirmed no significant differences for explanted allografts. However, xenografts demonstrated clear matrix changes, enabling detection of distinct inflammatory-driven changes but without variations in the level of transforming growth factor-β. CONCLUSIONS: Despite short-term success, mid-term failure of xenogeneic IFC grafts due to a T-cell-mediated extracellular matrixtriggered immune response was shown.

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Biermann, A. C., Marzi, J., Brauchle, E., Schneider, M., Kornberger, A., Abdelaziz, S., … Stock, U. A. (2018). Impact of T-cell-mediated immune response on xenogeneic heart valve transplantation: Short-term success and mid-term failure. European Journal of Cardio-Thoracic Surgery, 53(4), 784–792. https://doi.org/10.1093/ejcts/ezx396

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