Abstract
Congenital heart disease (CHD) is the most common birth defect, requiring multiplehigh-risk surgeries during the child’s lifetime. Standard surgical procedures require the use
of materials that are not able to grow or remodel as children grow. Three D-bioprinting
technology offers a tool to create cell-laden constructs. This work attempts to: (i) Generate
multi-layered 3D bioprinted structures composed of pig thymus derived mesenchymal
stem cells (ptMSCs) encapsulated in alginate hydrogel with increased cell viability and
increased mechanical strength. Several parameters such as number of continuous printed
layers, crosslinking concentration and time were optimized. Results showed that 100 mM
CaCl2 crosslinking solution yielded cell-laden, six-layered constructs with higher number
of live cells throughout the 14-day culture period, but lower ultimate tensile strength in
comparison with 500 mM CaCl2 crosslinking solution. (ii) Develop a decellularization
approach of various biomaterials that preserves the ECM structure and composition and
achieve good biomechanical characteristics. The human tissues (amniotic membrane,
Wharton’s Jelly) and pig tissues (pericardium, myocardium) were decellularized using
enzymatic, chemical or detergent-free agents. Histological, biochemical and biomechanical
assessments were conducted on the tissues, and results showed that the decellularization of
the tissues was proven to be successful in removing the cellular and nuclear contents whilst
preserving the ECM structure and composition. deECM human amniotic membrane
(deECM human AM) proved to be an ideal biomaterial due to its allogeneic nature,
novelty in the treatment of CHD, similarity in strength to native pig PV leaflets. (iii)
Develop deECM human AM bioink for 3D-bioprinting. A mixture of deECM human AM
and pure soluble collagen type I at ratio 1:3 of deECM human AM: pure soluble collagen
type I, was found to be optimum for 3D bioprinting. (iv) Explore the use of 3D bioprinting
as a tool for cell-seeding. Various geometries, types of scaffolds, cell seeding densities and
cell culture conditions were tested to search for the optimum conditions. Results showed
that 3D bioprinting achieved accurate positioning and homogenous cell distribution when
deposited on deECM human AM and commercial scaffolds. Moreover, no-grid geometry,
high cell seeding density and dynamic cell culture condition yielded high cell viability and
number of live cells. This approach holds promise to produce good quality of in-house
stem-cell patches that could potentially be used in cardiovascular regeneration. (v) Assess
the usage of cell-free deECM human AM as pulmonary valve leaflets stitched to a conduit
composed of commercial scaffold in a unique piglet model for RVOT reconstruction in
children suffering from Tetralogy of Fallot/pulmonary atresia. This one animal proof
of concept study demonstrated no signs of calcification, regurgitation, degradation or
obstruction when this valved conduit was implanted in the piglet, thereby paving the
way for its potential use in the RVOT reconstruction in children with CHD.
| Date of Award | 18 Mar 2025 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Mohamed Ghorbel (Supervisor), Dominga Iacobazzi (Supervisor) & Massimo Caputo (Supervisor) |