230-LB: A Composite Capsule Strategy Support Longevity of Microencapsulated Pancreatic ß Cells

Abstract

Microencapsulation of islets in immunoprotective membranes offers an alternative treatment for type 1 diabetes in absence of systemic immunosuppression. However, periods of survival of transplanted islets are still limited. A factor that might be involved in a limited duration of survival is permanent damage to the extracellular matrix (ECM) during enzymatic islet-isolation which enhances susceptibility of islets for inflammatory stress. Here we investigated whether a combination of inclusion of ECM components (collagen IV and RGD), necroptosis inhibitor necrostatin-1 (Nec-1), amino acids (AA), and inclusion of the immunomodulatory polymer pectin in microcapsules can enhance the functionality of β-cells. The impact of these factors individually or combined was tested on MIN6 β-cells and human islet-cells. Viability, function, and immune activation via danger-associated molecular patterns (DAMPs) release and NF-κB activation in THP1-reporter cells were determined. Also, impact on mitochondrial dynamics was tested. Our data show that composite capsules of pectin/ECM/Nec-1/AA improve insulin secretion and enhance the mitochondrial activity of β-cells in vitro till day 7 after encapsulation. The alginate-pectin based microcapsules also showed immunomodulatory effects with decreased DAMPs release and lower NF-κB activation. After cytokine exposure, pectin/ECM/Nec-1/AA prevented the cytokine-induced decrease of mitochondrial activity and prevented viability loss until day 5. The rescuing effects were accompanied by modulation of mitochondrial fusion and fission gene expression, similar to that of untreated controls. Our data suggest that this composite capsule strategy using pectin/ECM/Nec-1/AA supports survival of microencapsulated β-cells and lowers susceptibility of β-cells for inflammatory stress. This strategy to create a better intracapsular microenvironment is a potentially promising way to preserve islet function and enhance graft survival time. Disclosure T. Qin: None. A. M. Smink: None. P. De vos: None. Funding JDRF (2-SRA-2018-523-S-B); China Scholarship Council (201906230339)