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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/191272
Engineered functional 3D spheroids for β-cell encapsulation
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[eng] Type 1 Diabetes Mellitus (T1DM) is known to be associated with the immune-mediated destruction of insulin-secreting β-cells. Cell replacement therapy is thought to be a potential long-lasting cure for diabetes. In this regard, allogeneic pancreatic islet transplantation is currently considered an alternative therapeutic option. However, the shortage of islet donors and the poor islet survival after transplantation restrict the use of this technique. Human embryonic (hESC) stem cell differentiation techniques have enabled the large-scale in vitro production of stem cell-derived β cells (SC-βs), for future cell replacement therapy. Even so, graft rejection can occur as a result of the innate and adaptive immune response, necessitating chronic immunosuppressive regimes.
A key component in successfully optimizing graft survival after transplantation is immune regulation, and the rapid establishment of blood flow for nutritional and oxygen supply. In this line, the application of immunosuppressive medication can be avoided when transplanted cells are embedded in immunoprotective membranes. These membranes can protect cells from the host immune system and provide a 3D architecture emulating the microenvironment found in vivo. The encapsulation in immunoprotective membranes can be done in two geometries, i.e., macro- and microdevices. The advantage of microdevices, such as microspheres lies in their high surface-to-volume ratio, which facilitates faster oxygen diffusion and the exchange of glucose, insulin, and nutrients. Further, microspheroids or spheroids can be easily handled in a fluid suspension, and precise spatial and dosing controls are possible for in vivo applications.
Current microsphere fabrication technologies have several drawbacks such as the need for an oil phase containing surfactants, diameter heterogeneity of the microspheres, and high time-consuming processes. Moreover, these methodologies frequently use alginate, which has low biocompatibilities and can lead to a fibrotic response, thereby limiting the efficacy of the graft. The use of collagen-based hydrogels is becoming increasingly recognized as an ideal biomaterial for cell-laden hydrogels. It is a natural material with good biological compatibility and low antigenicity. However, collagen is biodegradable, is challenging to handle and the fibrillar structure is weak for direct use. Consequently, we propose in this thesis a strategy for optimizing the cell delivery device. The first aim of this thesis was to develop a novel methodology to produce microspheres in an automated fashion, able to mask the encapsulated cells from the immune system, without adversely affecting cell viability. We generated three-dimensional (3D) bioprinted collagen microspheres by deposition of the cell-laden bioink into a superhydrophobic surface. Recent studies have proposed collagen crosslinkers that can confer mechanical firmness to collagen hydrogel. However, their plethora of disadvantages ranges from cytotoxicity to expensive cost and excessive crosslinking time. Here, we have crosslinked the bioprinted microspheres with tannic acid (TA) which improved spherical and structural consistency. Our results have also uncovered that TA prevents collagenase degradation and enhances spherical structural consistency and stiffness while allowing the diffusion of insulin.
The second aim of this thesis was to develop a pancreatic tissue-derived decellularized matrix hydrogel to obtain the extracellular matrix (ECM) properties to faithfully recreate the microenvironment of the islets in vivo. The use of decellularized ECM (dECM) scaffolds for bioengineering of human-tissue constructs is envisioned as a major platform for therapeutic applications. Here, we demonstrated an in-house optimal human decellularization protocol to generate a human dECM hydrogel. The developed hydrogel represented the possibility of engineering functional human insulin-secreting tissue constructs.
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CLUA FERRÉ, Laura. Engineered functional 3D spheroids for β-cell encapsulation. [consulta: 7 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/191272]