Wharton's Jelly-Mesenchymal Stem Cells- engineered conduit for pediatric translation in Heart Defect.

The materials available for the Right Ventricular Outflow Tract (RVOT) reconstruction in patients with Tetralogy of Fallot (TOF)/pulmonary atresia come with the severe limitation of long-term degeneration and lack of growth potential, causing right ventricular dysfunction, aneurysm formation and arrhythmias, thus necessitating several high-risk reoperations throughout patients' life. In this study, we evaluated the capacity of Mesenchymal Stem Cells (MSCs) derived from the Wharton's Jelly (WJ-MSCs), the gelatinous inner portion of the umbilical cord, to grow and recellularize an extracellular matrix (ECM) graft in our optimised xeno-free, good manufacturing practice- compliant culture system. WJ-MSCs were phenotypically and functionally characterised by flow cytometry and multi-lineage differentiation capacity, respectively. The typical MSCs immunophenotype and functional characteristics were retained in our xeno-free culture system, as well as the capacity to grow and engraft onto a naturally occurring scaffold. Wharton's Jelly MSCs, from both human and swine source, showed excellent capacity to recellularize ECM graft producing a living cell-seeded construct. In addition, we have provided an in vivo proof of concept of feasibility of the cellularised conduit, engineered with swine Wharton's Jelly MSCs, to be used in a novel porcine model of main pulmonary artery reconstruction, where it showed good integration within the host tissue. Our study indicates that the addition of WJ-MSCs to the ECM scaffold can upgrade the material, converting it into a living tissue, with the potential to grow, repair and remodel the RVOT. These results could potentially represent a paradigm shift in paediatric cardiac intervention towards new modalities for effective and personalised surgical restoration of pulmonary artery and RVOT function in TOF/pulmonary atresia patients.