Integrin Signaling via RGD Peptides and Anti-β1 Antibodies Confers Resistance to Apoptosis in Islets of Langerhans

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Abstract
Islet transplantation is associated with a high rate of early graft failure caused by early immune attack and poor functionality of islets. Apoptosis of islet cells appears soon after islet isolation and primarily involves the β-cell. The purpose of this study was to determine the effect of ligation to extracellular matrix (ECM) proteins on survival of the islets of Langerhans following islet isolation. Islets that had been cultured for 24 h on collagen type I showed an islet survival of 59.7 ± 8.7%, while islets that had been cultured on collagen type IV and laminin showed an islet survival of 88.6 ± 10.3 and 94.3 ± 5.6%, respectively. Islets that had been pretreated with anti-β1 antibodies and argenin-glycin-aspartic acid (RGD) peptides showed a decrease in the level of apoptosis by a factor of 2.5 and 3.1, respectively, and an increase of phospho-Akt Ser 473 activity by a factor of 3.1 and 2.9, respectively, compared with untreated islets. When detached from their natural ECM surrounding in the pancreas, islet cells undergo apoptosis, unless islets are cultured on collagen IV or laminin or treated with anti-β1 integrin antibodies or RGD peptides to mimic ECM ligation. These results indicate that inhibition of anoikis may offer opportunities to improve function and viability of islet cells.