Immunomodulatory microporous annealed particle (MAP) gel protects delivery of islets to promote islet transplantation outcomes
Mingyang Ma1, Preeti Chhabra1, Colleen Roosa2, Donald Griffin2, Kenneth Brayman1.
1Surgery, University of Virginia, Charlottesville, VA, United States; 2Biomedical Engineering, University of Virginia, Charlottesville, VA, United States
Introduction: To investigate if coating dissociated or whole islets with microporous annealed particle (MAP) gel could support cell function and viability and improve islet transplantation outcomes.
Methods: a) C57BL/6 mouse islets were mixed with MAP gel and cultured in 24 well plates at 37°C. The viability of islets was scored after Propidium Iodide-Fluorescein Diacetate (PI/FDA) staining and Glucose stimulated insulin secretion (GSIS) assay performed on Day 1, 3, 5, and 7 post-culture. The experiment was done thrice. b) Single cells from C57BL/6 mouse dissociated islets were mixed with MAP gel, and cultured in 24 well plates at 37°C. Viability of cells was scored after PI/FDA staining and GSIS assay performed 1, 24, 48, and 72 hours post-culture. c) 100 C57BL/6 mouse islets were dissociated into single cells by Trypsin, mixed with MAP gel, and transplanted into syngeneic diabetic recipients under the kidney capsule. Blood glucose (BG) was measured daily.
Results: Mouse islets protected with MAP gel displayed similar GSIS and viability scores when compared to uncoated islets. Both groups retained above 95% viability, with the stimulation index (SI) of MAP gel-protected islets 3.2 and that of uncoated islets is 2.4. Viability of dissociated islets protected with MAP gel was 84% with a SI=8.5 at 72 hours post culture. In contrast, uncoated dissociated islets were nearly dead with only 35% viability and an SI=0.38 at 72 hours post culturing. In MAP scaffold, dissociated islet cell viability was density dependent − cell viability in the 50 and 12.5 dissociated islet conditions was on average >78%, while dissociated cells from 2.5 islets demonstrated 56% viability after 72 hours. In in vivo studies, no significant difference was observed in the ability to return Streptozotocin-induced diabetic mice to normoglycemia when either MAP gel coated or uncoated whole islets (75-100 islets) were transplanted under the mouse kidney capsule. C57BL/6 mouse islets (100 islets) that were dissociated to single cells and co-transplanted with MAP gel under the kidney capsule, permanently returned transplanted mice to normoglycemia, with glucose levels below 200 mg/dL within 18 days post-transplantation (n=6). In contrast, uncoated dissociated islets failed to restore normoglycemia in tranplanted mice. Treatment efficacy continued 40 days post-transplantation (time mice were monitored). The average blood glucose measured at Day 30 was 163 ± 38.2 mg/dL. Recipient mice transplanted with cells from dissociated islets without MAP gel remained hyperglycemic (n=6/group).
Conclusion: The MAP scaffold protects delivery of dissociated islet cells, and helps promote islet transplantation outcomes. Moreover, MAP scaffold provides a possible platform for delivering stem cell-derived insulin-secreting cells.
LaunchPad Ignite. NIH grant: NIBIB R21 Trailblazer [1R21EB028971-01A1].
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