Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Physiology and Pharmacology

Collaborative Specialization

Developmental Biology

Supervisor

Hess, David A.

Affiliation

Robarts Research Institute

Abstract

Previously, pharmacological activation of Wnt-signaling in human bone marrow-derived multipotent stromal cells (hMSC) generated conditioned media (CM) that promoted β-cell regeneration in streptozotocin-treated mice. Ductal-derived endocrine progenitors, which have been shown to generate β-cells following pancreatic injury, represent a candidate for the ‘signal-receiving cell’. Ductal (CK19+) cells from mice pancreata obtained by purification of live Dolichos Biflorus Agglutinin lectin+ cells and cultured in minimal media supplemented with Untreated, Wnt-activated, or Wnt-inhibited CM demonstrated a significantly increased proportion of EdU+/CK19+ cells following 48-hours of supplementation but no endocrine phenotype acquisition. Lineage-tracing CK19-CreERT;Ai9(RCL-tdT) mice treated with tamoxifen (single dose) demonstrated specific labeling of pancreatic CK19+ cells. Streptozotocin treatment (60 mg/kg/day, 5 days) resulted in decreased β-cell mass, islet density, and insulin+ cell frequency, as well as impaired glucose tolerance and increased pancreatic leukocyte infiltration. This model will be used in future studies to lineage-trace CK19+ cell contribution during hMSC CM-induced islet regeneration.

Summary for Lay Audience

Type 1 diabetes is characterized by the destruction of insulin-producing β-cells in pancreatic islets, leaving patients unable to control their blood glucose. Regeneration of lost β-cells represents a promising treatment strategy. Our lab pioneered the use of transplanted human bone-marrow derived mesenchymal stem cells (MSC) to stimulate islet regeneration in mice with β-cell destruction. Pharmacological activation of the Wnt-pathway in MSC cultures generated a concentrated protein mixture (CM) that consistently reduced blood glucose levels in mice with diabetes. However, the identity of signal-receiving cells that mediate islet regeneration within the pancreas remains unknown. Recently, regeneration of β-cells from pancreatic duct cells has been demonstrated. Treating isolated pancreatic duct cells with MSC CM increased their replication compared to minimal culture conditions but did not stimulate expression of other pancreatic cell proteins. We also characterized a specialized mouse model designed to follow the fate of duct cells. This model will be used in future studies to investigate ductal cell contribution to islet regeneration following CM injection. These studies contribute to the development of ‘cell-free’ regenerative medicine therapies for diabetes.

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