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Factors Influencing Insulin Secretion From Encapsulated Islets

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Adequate regulation of glucose levels by a microencapsulated pancreatic islet graft requires a minute-to-minute regulation of blood glucose. To design such a transplant, it is mandatory to have sufficient insight in factors influencing the kinetics of insulin secretion by encapsulated islets. The present study investigates factors influencing the glucose-induced insulin response of encapsulated islets in vitro. We applied static incubations and did the following observations. (i) Small islets (90–120 μm) showed a similar instead of a lower glucose-induced insulin response, suggesting that inclusion of only small islets, which are associated with lower protrusion and failing rates, has no consequences for the functional performance of the graft. (ii) A capsule diameter of 800 μm showed identical rather than lower glucose-induced insulin responses as smaller, 500-μm capsules. (iii) Capsule membranes constructed with a conventional permeability interfered with diffusion of insulin, as illustrated by a lower response of islets in capsules with a 10-min poly-L-lysine (PLL) membrane than islets in capsules with a 5-min PLL membrane. (iv) Irrespective of the tested porosity, the capsules provided sufficient immunoprotection because the 10-min PLL membranes did block diffusion of the cytokines IL-1β (17 kDa) and TNF-α (70 kDa) while the 5-min PLL membranes interfered with the diffusion of the vast majority of the cytokines. We conclude that capsules containing small islets (90–120 μm) and a membrane with a lower permeability than routinely applied is preferred in order to obtain a graft with adequate glucose-induced insulin responses.

Keywords: Alginate; Encapsulation; Islets; Poly-L-lysine; Transplantation

Document Type: Research Article


Affiliations: Immunoendocrinology, Department of Pathology and Laboratory Medicine, Section of Medical Biology, University of Groningen, Hanzeplein 1, 9700 RB Groningen, The Netherlands

Publication date: 2002-12-01

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  • Cell Transplantation publishes original, peer-reviewed research and review articles on the subject of cell transplantation and its application to human diseases. To ensure high-quality contributions from all areas of transplantation, separate section editors and editorial boards have been established. Articles deal with a wide range of topics including physiological, medical, preclinical, tissue engineering, and device-oriented aspects of transplantation of nervous system, endocrine, growth factor-secreting, bone marrow, epithelial, endothelial, and genetically engineered cells, among others. Basic clinical studies and immunological research papers are also featured. To provide complete coverage of this revolutionary field, Cell Transplantation will report on relevant technological advances, and ethical and regulatory considerations of cell transplants. Cell Transplantation is now an Open Access journal starting with volume 18 in 2009, and therefore there will be an inexpensive publication charge, which is dependent on the number of pages, in addition to the charge for color figures. This will allow work to be disseminated to a wider audience and also entitle the corresponding author to a free PDF, as well as prepublication of an unedited version of the manuscript.
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