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Improving Islet Function and Engraftment by Co-culturing Islets with Mesenchymal Stem Cells and the Formation of Pseudoislets

  • Author / Creator
    Gamble, Anissa
  • Islet transplantation has proven to be efficacious in preventing severe hypoglycemia and restoring insulin independence in selected patients with type 1 diabetes. The well-established procedure has gained popularity due to notable refinements over the past two decades. However, islet transplantation is not a permanent solution for glycemic control as multiple infusions are often required to achieve and maintain insulin independence, and chronic lifelong immunosuppression is required. Substantial islet loss occurs prior to and post-transplant due to multiple factors including nutrient depletion, the instant blood-mediated inflammatory reaction, and potent host auto- and alloimmune responses. To circumvent islet loss, this thesis evaluates the effect of co-culturing islets with mesenchymal stem cells and alternatively reformation of islets into pseudoislets as two potential discrete strategies to improve long term islet function and survival. We first evaluated the effect of co-culturing murine and human islets for 48 hours with human adipose-derived mesenchymal stem cells. In vitro, murine islets co-cultured with adipose-derived mesenchymal cells demonstrated superior islet yield, vitality, survival and function relative to islets cultured alone. In an immunodeficient mouse model, we demonstrated a marginal islet mass co-transplanted with adipose-derived mesenchymal stem cells without prior co-culture failed to restore normoglycemia as efficiently as islets alone. However, islets co-cultured with adipose-derived mesenchymal stem cells for 48 hours and subsequently co-transplanted into mice had improved glycemic profiles relative to islet cultured and transplanted alone. We demonstrated preserved mouse islet function and recovery during a co-culture and co-transplantation with adipose-derived mesenchymal stem cells relative to islets alone. In the second part of this thesis, we evaluated the function and efficacy of the bioengineered islets called pseudoislets. Utilizing the Aggerwell® system developed by Mark Ungrin and colleagues from the University of Calgary, human islets were dissociated and re-aggregated into uniform sizes. We sought to determine the optimal size and dose for islet function and engraftment. We found that reaggregated pseudoislets demonstrated improved in vitro insulin secretion and hypoxia tolerance. When tested in vivo in a chemically diabetic murine model, pseudoislets reversed diabetes at a similar rate and demonstrated improved glucose clearance compared to native islets. We found that dissociated and re-aggregated islets had comparable outcomes when compared to native islets. This intriguing finding provides room for considerable future investigation.

  • Subjects / Keywords
  • Graduation date
    Fall 2018
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R30V8B00N
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.