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Cell- and matrix-based approaches for improvement of islet beta-cell survival and function in vitro and in vivo

University of British Columbia

Islet transplantation provides a feasible approach for treatment of type 1 diabetes (T1D), in which islet β-cells are destroyed by autoimmune attack. However, its efficacy is currently limited by poor long-term islet graft survival. Loss of islet extracellular matrix (ECM) and formation of human islet amyloid polypeptide (hIAPP) aggregates are two important non-immunological factors contributing to β-cell destruction. In this study, we developed novel matrix- and cell-based approaches under 3 different objectives. We hypothesized that these new strategies can protect islet β-cells from the toxicity induced by non-immune or autoimmune factors thereby enhancing the viability and function of islet β-cells in both in vitro and in vivo diabetes models. To provide surrogate ECM materials for islets, three-dimensional scaffolds, collagen matrix (CM) alone and human fibroblasts-populated collagen matrix (FPCM) were developed in objective 1. Isolated human islets were then either embedded within the scaffolds or cultured in two-dimensional free-floating condition (control) for 7 days. The findings showed markedly lower formation of hIAPP aggregates in the scaffold-embedded islets as compared to control islets. The morphology, viability, and functionality of ECM-populated islets were significantly improved as compared to control islets. In objective 2, we evaluated the signaling pathways involved in the cytotoxicity induced by hIAPP aggregation. Protein kinase B (PKB), a key effector of the pro-survival phosphoinositide 3 (PI3)-kinase signaling pathway was studied. Our findings demonstrated that both exogenously applied and endogenously formed hIAPP aggregates reduce PKB activation in islet β-cells, likely via IL-1β signaling. Autoimmunity is another causative factor of β-cell destruction during islet transplantation and T1D. In objective 3, we aimed to prevent the progression of T1D in non-obese diabetic (NOD) mice. We used dermal fibroblasts expressing indoleamine 2,3-dioxygenase (IDO), which is an immuno-modulating enzyme. We found that intraperitoneal injection of 15 million dermal fibroblasts into NOD mice successfully reversed the progression of T1D through inhibiting the β-cell specific autoreactive T cells and Th17 cells, as well as inducing regulatory T cells. Collectively, the approaches developed in this study can reduce the destruction of islet β-cells by non-immune and autoimmune factors thereby enhancing viability and function of islet β-cells in diabetes.

Text

2016-06-30

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/51504

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/