Functional Capacity of Human Islets After Long-Distance Shipment and Encapsulation

Abstract

Human islets produced at an isolation center are shipped to researchers, usually taking short periods to arrive at their destination. In this study, we investigated whether human islets after long-distance shipment across the Pacific Ocean for 2 to 3 days and encapsulation could maintain their functionality. Human islets were encapsulated in alginate and viability assessed using carboxyfluorescein diacetate and propidium iodide. Stimulation index after static glucose incubation was calculated. Streptozotocin-induced diabetic nonobese diabetic/severe combined immunodeficient mice were transplanted with 3000, 2000, or 1000 islet equivalents of nonencapsulated and encapsulated islets and glucose levels monitored. When levels were normal, the graft was retrieved and assessed. Viability of human islets was unaltered after long-distance shipment with a retrieval rate of 88.3% ± 1.9%. After encapsulation, the viability was unchanged (before encapsulation 86.1% ± 0.7% vs after encapsulation 80.8 ± 0.7%) at 11 days after isolation. Function in vitro of nonencapsulated and encapsulated islets was unaffected with a stimulation index of 2.2 and 1.9, respectively. Euglycemia was achieved in 100% mice receiving 2000 and 3000 islet equivalents of nonencapsulated and encapsulated islets, respectively. Capsules retrieved after transplantation was intact, free floating, and contained viable islets. Human islets can be shipped safely for long distances without compromising viability and function even after encapsulation and culture.