Cell-based therapies are emerging for Type I diabetes mellitus (T1D), an autoimmune disease characterized by the destruction of insulin producing pancreatic β-cells, as a means to provide long term restoration of glycemic control. The limited supply of donor islets has motivated research into methods for differentiating pancreatic β-cells from renewable pluripotent stem cells such as human pluripotent stem cells (hPSCs). Biomaterial scaffolds maintain the integrity of cell-to-cell and cell-to-matrix connections by avoiding the disruption of the cell niche during handling. This dissertation addresses three key questions with respect to cell therapy and immunomodulation for T1D, including culture system on porous PLG scaffold, functionalized scaffold for improved cell viability and maturation, and immunomodulation with the membrane coated nanoparticles (MCNPs).

Culture on porous biomaterial scaffolds of hPSCs was investigated at multiple stages of differentiation between Stage 0 and 6 for improved differentiation. Scaffolds are biomaterial devices that could provide chemical and physical cues to control the microenvironment and subsequently alter cellular behavior by facilitating cell-cell interactions. The culture of cells on the scaffolds was found to support maturation of SC derived beta cells depending on the stage of seeding. Suspension cultured-pancreatic progenitors seeded onto scaffolds for stage 5 culture (pancreatic endocrine development), demonstrated enhanced expression for many maturation genes compared to cells that remained in suspension culture through the end of stage 6. This study showcased the scaffold culture as a promising platform for maturation that allows cells to develop a niche and may allow for direct transplantation without manipulating cells.

Early engraftment and development of β-cells post transplantation are a major limitation for stem cell derived beta cells due in part to their being immature. The survival and development of hPSC-derived β-cells seeded onto PLG microporous scaffolds were investigated within the initial 2 weeks post transplantation. Early inflammatory events induced by the biomaterial and transplanted cells heavily affected hPSC-derived β-cell engraftment due to the innate immune response. The inflammation includes the production of soluble mediators, inflammatory cytokines and the recruitment of innate cells at the graft site, hindering early graft engraftment and in-vivo hPSC-derived β-cell maturation. The PLG-based biodegradable scaffold chemically linked with a novel form of FasL chimeric with streptavidin, SA-FasL, was applied to create an immunoprivileged transplant site by modulating the local inflammatory microenvironment. The β-cell viability and differentiation were found improved at the SA-FasL induced immunoprivileged site together with a suppressed inflammatory reaction.

Life-long systemic immune suppression due to allogenic graft/cell transplant also limits the translation of cell therapies for T1D. We investigated the design of membrane-coated nanoparticles (MCNPs), with membranes derived from bone marrow-derived dendritic cells and coated onto poly(lactic-co-glycolic acid) (PLGA) nanoparticle cores, to directly interact with both naïve and activated T cells. Mechanistic studies revealed that the developed MCNPs have the capability to communicate with allogenic T cells by modulating the cytokine secretion levels similar to professional antigen presenting cells. Furthermore, the MCNPs can be engineered pre- and post-fabrication for upregulated surface molecules or varied antigen binding and can be functionalized by biotinylation for a wider range of protein loading.

Overall, this dissertation discussed optimization and early immunomodulation of the biomaterial culturing system for hPSC-derived β cells, and development of tunable MCNPs for direct T cell communication.

Date: Monday, June 13, 2022
Time: 12:00 PM
Location: NCRC Building 520 Room 1122 and Zoom (https://umich.zoom.us/j/93840656651)
Chair: Dr. Lonnie Shea