No abstract

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.

Recently, therapeutic angiogenesis has been proposed as an alternative for the treatment of ischemic diseases unresponsive to conventional therapy. This strategy is based on the concept that a supply-side approach with growth factors would overcome the endogenous deficit and result in more robust collateralization. We have developed a strategy based on local delivery of human tissue kallikrein gene for potentiation of microcirculation and rescue of peripheral ischemia. Following successful application in otherwise healthy animals, the approach resulted to be of therapeutic value in rats with endothelial dysfunction caused by arterial hypertension. In addition, human tissue kallikrein prevents or rescues microvascular rarefaction caused by diabetes mellitus. In this model, human tissue kallikrein was able to stimulate vascular growth and contrast apoptosis. The strategy displays interesting pharmacological features because is devoid of obvious side effects and is effective even at low infecting doses. In addition, the neovascularization promoted by human tissue kallikrein is well organized and durable. It is reasonable to anticipate that the new approach will have a great impact in the treatment of cardiovascular ischemic complications.