Abstract
Congenital heart disease is an abnormality in the structure of the heart affecting roughly 1% of new-borns. Although prognosis has improved recently, reconstructive surgery remains inadequate due to the inability of prosthetic grafts to replicate the functionality or the somatic growth of native tissue. In malformations such as Tetralogy of Fallot, this results in repeated surgical intervention, which has a substantial impact on quality of life. Tissue engineering may offer a solution to the limitations of current graft technology by generating a biological graft with improved functionality. Indeed, recent evidence has demonstrated the feasibility of using cardiac pericytes engineered vascular grafts for reconstruction of the pulmonary artery; however, isolation of this cell population is reliant upon tissue obtained during initial palliative surgery or an ad hoc invasive cardiac biopsy, which carries elevated risk. In search of a more accessible cell source, this study aimed to explore the prospect of isolating pericytes from the umbilical cord or placenta and using them for neonatal vascular engineering applications.Different isolation methodologies were explored in parallel resulting in isolation and expansion of three different pericyte populations categorised by their isolation marker, namely NG2 umbilical cord pericytes (UCPs), CD146 UCPs and CD34 placenta pericytes. These populations were characterised to assess their purity and compare therapeutic properties. Of the three populations, NG2 UCPs demonstrated the most consistent antigenic phenotype and a high proliferation rate. After exposure to differentiation medium, they were successfully induced to a vascular smooth muscle cell-like phenotype, as evidenced by the expression of transgelin and smooth muscle myosin heavy chain. Analysis of cell monolayers and conditioned medium revealed production of extracellular matrix proteins and the secretion of major angiocrine factors, which conferred NG2 UCPs with ability to promote endothelial cell migration and tube formation. Decellularized swine-derived grafts were functionalized using UCPs and cultured under static and dynamic flow conditions. UCPs were observed to integrate into the outer layer of the graft and modify the extracellular environment, resulting in improved elasticity and rupture strain in comparison with acellular grafts.
These findings demonstrate that a homogeneous pericyte-like population can be efficiently isolated and expanded from human cords and integrated in acellular grafts currently used for repair of CHD. Functional assays and in vitro graft testing suggest that NG2 UCPs may represent a viable option for neonatal tissue engineering applications.
| Date of Award | 24 Jun 2021 |
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| Original language | English |
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| Supervisor | Paolo R Madeddu (Supervisor) |