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Title page for ETD etd-03232018-170107


Type of Document Dissertation
Author Saunders, Diane Caitlin
URN etd-03232018-170107
Title Towards Pancreatic β-Cell Regeneration: Modulating Islet Microenvironment and Identifying Markers of β-Cell Maturation
Degree PhD
Department Molecular Physiology and Biophysics
Advisory Committee
Advisor Name Title
David Jacobson, Ph.D. Committee Chair
Alvin C. Powers, M.D. Committee Member
Ambra Pozzi, Ph.D. Committee Member
Antonis Hatzopoulos, Ph.D. Committee Member
Roland Stein, Ph.D. Committee Member
Keywords
  • β-cell regeneration
  • pancreatic islet
  • endothelial cells
  • microenvironment
  • macrophage recruitment
Date of Defense 2018-03-20
Availability unrestricted
Abstract
Regeneration of endogenous β-cells is a promising therapy to treat diabetes, but there are considerable gaps in our understanding of the microenvironmental signals necessary to stimulate β-cell proliferation and the unique ways human β-cells differ from rodents. Our group previously modulated the islet microenvironment using a mouse model in which vascular endothelial growth factor A (VEGF-A) overexpression causes β-cell loss and endothelial cell (EC) expansion, followed by β-cell proliferation and regeneration that requires infiltrating macrophages. To determine the role of proliferative and quiescent ECs, we conditionally inactivated the key receptor mediating VEGF-A signaling, VEGFR2, in ECs and found that EC signaling was necessary for maximal macrophage recruitment and phenotype activation. We also showed that ablation of VEGFR2 in quiescent ECs during the β-cell regenerative phase induced rapid vessel regression that promoted β-cell proliferation, possibly mediated by growth factor release from the extracellular matrix. Extending these findings to human pancreas development, we determined that intra-islet EC area was greatest during the first year of postnatal life and coincided with the peak of β-cell proliferation, suggesting that vascular arrangement or EC-derived signals may impact human β-cell proliferation. Next, to advance the methodologies for studying human islets, we identified two molecular markers of developing and mature human β-cells. Secretory granule membrane major glycoprotein 2 (GP2) marks a population of multipotent pancreatic progenitor cells in the neonatal human pancreas, and can be utilized to improve efficiency of generating β-like cells from stem cells. Nucleoside triphosphate diphosphohydrolase 3 (NTPDase3) is a cell surface marker of adult human β-cells, and is a unique tool for isolating live β-cells by flow cytometry and performing in vivo β-cell imaging. These two markers will further our knowledge of islet development and allow us to assess β-cell gene expression and mass during the disease process, which we demonstrated by utilizing our islet cell isolation strategy to reveal transcriptional dysregulation in α-cells from donors with type 1 diabetes. Together, this work provides a framework for future efforts aimed at promoting β-cell regeneration and increasing functional β-cell mass.
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