Decellularisation and stem cell tissue engineering of valved right ventricular outflow tract xenografts for correction of tetralogy of Fallot

Abstract

Background: Tetralogy of Fallot (TOF) is a cyanotic congenital heart disease that often
requires right ventricular outflow tract (RVOT) replacement in infancy. Shortage of
small-diameter cardiac homografts necessitates the use of xenografts in paediatric
surgical reconstruction. Current RVOT substitutes have not proven to be a lifelong
solution for paediatric cardiac repair, being limited by immunoincompatibility and their
inability to grow. Decellularisation to eliminate immunogenic material is a method to
diminish rejection risk. To combat lack of growth, in vitro cellularisation with stem cells
is a promising solution. This work intends to produce a tissue engineered decellularised
RVOT xenograft to advance repair of TOF.
Methods: This research has developed and evaluated a porcine RVOT decellularisation
technique, customising a 3D printed flow chamber to produce decellularised scaffolds.
Recellularisation with mesenchymal stem cells has been explored to enhance immune
tolerance and endow the graft with growth capacity, applying a personalised approach
to seed the scaffold.
Results: Effective decellularisation has been achieved, using the customised 3D printed
flow system and protocol to significantly reduce nuclei count, remove DNA, and
eliminate known xenoantigen Galα1-3Galβ1-4GlcNAc-R. In parallel with removal of
immunogens associated with rejection, the extracellular matrix elastin, collagen, and
tensile properties are maintained, and the scaffold withstood inflation testing up to 100
mmHg. MSCs were successfully seeded onto the conduit using a novel in vitro seeding
technique, achieving a dense and uniform cell layer.
Conclusion: RVOTs have been decellularised and proven to possess seeding potential.
Future work would look to assess the dynamic durability of the scaffolds, as well as
develop the promising seeding methodology. Overall, the tissue engineered xenograft
provides a means to combat immunological mismatch between donor and patient and
show growth potential. The product may have future translational capacity as a surgical
alternative to support corrective intervention in paediatric TOF patients.

Date of Award	4 Feb 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Massimo Caputo (Supervisor), Giovanni Biglino (Supervisor), Francesca Bartoli-Leonard (Supervisor) & Adam W Perriman (Supervisor)