Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Physiology and Pharmacology

Supervisor

Hess, David

Abstract

Diabetes affects ~537 million people worldwide. Although insulin can help manage blood glucose, 80% of patients suffer severe complications, prompting a need for novel therapies. Human bone marrow-derived multipotent stromal cells (MSC) expanded under Wnt-pathway stimulation secrete islet regenerative factors into conditioned media (Wnt+ CM). Proteomic analyses identified 8 secreted proteins (FAM3C, PSAP, SOD1, PPIA, GAL1, CTSB, TGM2, CALU) as top candidates; however, the islet regenerative functions of these proteins have not yet been functionally validated. We tested the islet regenerative capacity of these MSC-secreted proteins in vitro using human islet cultures and in vivo using streptozotocin-treated mice. Although the proteins had minimal effects on islet viability and proliferation in vitro, intrapancreatic injection of the 8-protein combination showed islet regenerative effects comparable to Wnt+ CM in vivo, including decreased hyperglycemia, improved glucose tolerance, and increased beta cell mass. This study provides proof-of-concept for the development of protein-based therapies for diabetes.

Summary for Lay Audience

Inside the islet of Langerhans in the pancreas, beta cells are responsible for producing insulin to decrease blood glucose levels by promoting glucose uptake and storage in tissues. Diabetes is a chronic disease in which the patient’s beta cells are destroyed, or the body stops reacting to insulin properly, resulting in elevated blood glucose levels. Although diabetes can be managed with insulin injection, there is no cure, and 80% of patients develop severe complications in the heart and kidney, which negatively impact their quality of life. Development of strategies to regenerate beta cells may be a possible solution. Multipotent stromal cells (MSC) isolated from the bone marrow secrete regenerative proteins that drive tissue repair. Our previous research has shown that proteins made by MSC can promote human beta cell growth and reduce elevated blood glucose when directly injected into the pancreas of diabetic mice. However, specific proteins that stimulate beta cell regeneration are currently unknown. We have identified 8 proteins highly implicated in islet regeneration. Our goal is to document the regenerative functions of the 8 MSC-secreted proteins using human islets and in mice with diabetes.

Although the 8-protein combination did not promote human beta cell survival or growth in lab, we found that 8-protein combination had potent effects in the mouse model, including decreased blood glucose levels and improved glucose tolerance compared to mice that did not receive any treatment. In addition, analyses on the mouse pancreas showed that injection of the 8-protein combination increased islet size, islet number, and overall beta cell mass, confirming that islets were regenerated after protein injection.

To conclude, our data confirmed the islet regenerative functions of the 8 proteins secreted by MSC. These proteins may have great therapeutic potential since a single injection was able to improve glucose control. In the future, we will need to test 8-protein combination in other diabetes models, determine the right dosage of the proteins, and test their long-term effects. Overall, these data may lead to the development of islet regenerative therapies for the many patients with diabetes.

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