Efficacy evaluation of immuno-protected cellular therapeutics for diabetes treatment

Abstract

Immuno-isolation of therapeutic cells is a promising approach for immunosuppressant-free cellular therapy to restore glycaemic control in Type 1 Diabetes. However, the clinical application of this technology is confronted by hindered oxygen and nutrient transfer at the avascularized transplantation site leading to reduced oxygen uptake and impaired cellular viability. Strategies targeting distribution homogeneity and non-spheroidal geometry of the encapsulated microtissues have showed potential in supporting oxygen uptake and subsequently cellular viability in immortalized β cell models. This thesis aims to investigate the feasibility of developing a macro-encapsulation device integrating these strategies using clinical-relevant cells for in vivo efficacy and potential clinical translation. In particular, stem cell has been extensively investigated for unlimited generation of insulin-secreting β cells for cell-based therapy of T1D. Hence, this thesis explores the feasibility of fabricating toroidal microtissues from stem cell-derived islets for future application in macrodevice. First, we developed a novel encapsulation macrodevice termed waffle-inspired hydrogel-based macrodevice (WIM) that enabled the encapsulation of spheroidal microtissues, fabricated in situ or ex situ, in a homogeneous distribution. The device design parameters were optimized to maximize the homogeneous distribution of encapsulated microtissues in the device. We demonstrated that microtissues, when homogeneously distributed, maintained both high cellular viability and glucose-responsive insulin-secreting function. Furthermore, we investigated the feasibility of fabricating WIM device using rat primary islets and its therapeutic efficacy in vivo. We demonstrated that WIM devices encapsulating rat primary islets were fabricated with preserved cellular viability and functionality that reversed diabetes in chemically induced diabetic mouse model following subcutaneous transplantation. Second, we developed an advanced macrodevice that encapsulated in situ fabricated toroidal insulin-secreting microtissues arranged in homogeneous distribution, termed Hexagonal Toroid Encapsulation Device (HTED). Using rat primary islets, we optimized the device fabrication for optimal in vitro viability and functionality. Our results demonstrated the robust formation and encapsulation of toroidal microtissues within the device while maintaining their viability and responsive insulin-secreting function. Additionally, a proof-of-concept study showcased the in vivo glycaemic correction when transplanted these devices subcutaneously in chemically induced diabetic mice. Lastly, we explored the feasibility of utilizing clinically relevant cells for toroid microtissue fabrication. Human stem cell-derived islet-like cells (SC-islet cells) were investigated for the ability to reaggregate into toroid microtissues following enzymatic dispersion. We showed that toroid microtissues with robust mechanical properties could be fabricated using human cells with preserved viability. In particular, toroid microtissues derived from SC-islet cells maintained higher cellular viability compared to spheroidal shape following 20 days in vitro culture. Moreover, dynamic GSIS analysis showed the glucose-responsive insulin secretion following dispersion and reaggregation into toroid microtissues. Overall, the results of this thesis showed the versatility and robustness of toroid microtissue fabrication with preserved cellular viability and function from different clinically relevant cells. Moreover, macrodevice encapsulating in situ fabricated toroid microtissues in homogeneous distribution showed the potential in promoting the clinical translation of cell-based therapy for T1D.