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

: Biermann, Anna; Marzi, Julia; Brauchle, Eva; Schneider, Maria; Kornberger, Angela; Abdelaziz, Sherif; Wichmann, Julian L.; Arendt, Chirstophe T.; Nagel, Eike; Brockbank, Kelvin; Seifert, Martina; Schenke-Layland, Katja; Stock, Ulrich A.


European journal of cardio-thoracic surgery 53 (2018), Nr.4, S.784-792
ISSN: 1010-7940
ISSN: 1567-4258
ISSN: 1873-734X
Fraunhofer IGB ()
ice-free cryopreservation; heart valve transplantation; Allograft; Xenograft; T-cell-mediated immune response; organ scarcity

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.