Diabetes, Vol 40, Issue 11 1511-1516, Copyright © 1991 by American Diabetes Association
Prolonged reversal of diabetic state in NOD mice by xenografts of microencapsulated rat islets
ZP Lum, IT Tai, M Krestow, J Norton, I Vacek and AM Sun
Department of Physiology, University of Toronto, Ontario, Canada.
Transplantation of the islets of Langerhans could be the most promising
approach to the clinical treatment of insulin-dependent (type I) diabetes
mellitus. In this study, we report on a modified encapsulation technique
that produces small alginate-polylysine capsules (0.25-0.35 mm diam). In an
in vitro study, both encapsulated and unencapsulated islets showed
comparable responses to glucose challenge in terms of insulin secretion.
With the new capsules, 16 spontaneously diabetic NOD mice received
transplants of 800 encapsulated rat islets/animal. Nonfasting blood glucose
concentration decreased from 24.4 +/- 1.4 to 4.0 +/- 1.3 mM. At 4 and 5 mo
posttransplantation, the capsules were removed from 2 recipients. Both
animals regressed to a hyperglycemic state after capsule removal. However,
after another islet transplantation, normoglycemia was again restored in
these 2 animals. In control mice, which received unencapsulated islets, the
xenografts remained functional for less than 10 days. A high mortality rate
was observed among these animals within 2 mo of the recurrence of the
hyperglycemic state. Our results clearly indicate that encapsulation of
pancreatic islets in the improved capsules can effectively prolong
xenograft survival without immunosuppression in an animal model that mimics
human type I diabetes mellitus.