2104-LB: Alpha- and Beta-Cell Intercellular Communication via Extracellular Vesicles

Introduction & Objective: Type-1 diabetes (T1D) is characterized by autoimmune destruction of β-cells which is further associated with α-cells dysfunction leading to hypoglycemic unawareness. Both α and β cell types regulate each other in a paracrine manner. Exosomes are extracellular vesicles naturally secreted by most cell types and are involved in cell-to-cell communication. β-cells and α-cells also release exosomes, but the pathophysiological function needs investigation. Thus, the main objective is to study the intercellular communication between α and β-cell via exosomes.

Methods: Mouse α-TC-1 and βTC-6 cell lines were stimulated in low (2.5mM), basal (5.5mM) and high glucose (25mM) exosome depleted media for 24hrs. Exosomes are isolated using differential centrifugation and their presence were confirmed by using TEM, and western blot for exosomal markers. Quantification and characterization were done using micro-BCA, ELISA, and nanosight analysis. Exosomes were further used to cross-stimulate α and β cells under low and high glucose at various time points (6h, 12h, 24h, 48h). Insulin and Glucagon levels in media was measured by ELISA and regulation of transcription factors were measured by qPCR.

Results: TEM analysis revealed that α and β cells released cup-shaped, rounded vesicles of exosomes (30-300nm). Western blot analysis for exosomal markers (CD9) was confirmed. Glucagon expression in α-cells was significantly increased when stimulated with β-cell exosomes under low glucose condition (6h:P=0.0134; 24h:P=0.0455; 48h:P= 0.0532). The expression of glucagon in α-cell was not affected by β-cell exosomes under high glucose. MafB expression in α-cells correlated with glucagon expression. Interestingly, expression of insulin in β-cells was not significantly affected by α-cell exosomes.

Conclusion: Exosomes from β-cells seem to play a role in regulation of glucagon. Further investigation relating to production and release of insulin and glucagon in response to exosomes is warranted.