PROJECT SUMMARY/ABSTRACT In the pancreas the islet is surrounded by a specialized protein scaffold called the extracellular matrix (ECM) that regulates cell survival and insulin secretion. The ECM surrounding the islet consists mainly of laminin-10 and type IV collagen (COL IV) which provide mechanical and biochemical cues to the β-cells. During the onset of T1D, immune cells infiltrate the pancreas and the peri-islet ECM is degraded, leading to β-cell death. While changes to the peri-islet ECM have been well documented in T1D, the role of these ECM changes to T1D pathogenesis are largely unknown. Changes to ECM stiffness have been correlated to changes in insulin secretion; however, the mechanisms of mechanotransduction regulating insulin secretion have not been studied in the islet. Infiltrating immune cells also produce high levels of pro-inflammatory cytokines that cause islet dysfunction and death. While some studies have suggested that infiltrating immune cells degrade the peri-islet ECM, a recent study has shown that β-cell interactions with macrophages induces ECM remodeling by the β- cell. A role for the β-cell degrading the peri-islet ECM has not been established in T1D. Our overall goal is to determine the effect of changes in peri-islet ECM on islet function and to determine the role of autoreactive immune cells and cytokine stressed β-cells in remodeling the peri-islet ECM in T1D. We will utilize a novel reverse thermal gel scaffold functionalized with laminin-10 and COL IV with encapsulated mouse and human islets to accomplish this goal. Towards this goal we propose two specific aims: (1) Determine the effect of changes in ECM stiffness on islet function and insulin secretion dynamics; (2) Determine the role of autoreactive CD4+ and CD8+ T-cells and cytokine stressed β-cells in remodeling the peri-islet ECM in T1D. The results from this work will support a role for ECM mechanical properties in regulating islet function and will define a role for the β-cell in peri-islet ECM degradation and in the pathogenesis of T1D. The innovation of this work will provide useful insight into treating T1D and will help to improve diabetes therapies and the lives of patients.