Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Medical Biophysics

Collaborative Specialization

Molecular Imaging

Supervisor

Ronald, John

2nd Supervisor

Flynn, Lauren

Co-Supervisor

Abstract

Cell-based therapies using biomaterial scaffolds for localized injection of pro-regenerative cells offer a promising approach for vascular regeneration in peripheral artery disease. The objective of this project was to evaluate decellularized adipose tissue (DAT) hydrogels as an injectable delivery vehicle to enhance the localized retention of monocytes, using the THP-1 monocytic cell line as a surrogate for human monocytes. The THP-1 cells were engineered to co-express the red fluorescence reporter gene dTomato, the bioluminescence imaging (BLI) reporter gene firefly luciferase 2, and the magnetic resonance imaging reporter gene organic anion transporting polypeptide 1B3 to longitudinally track viable cell retention within the DAT hydrogels. In vitro BLI confirmed THP-1 cell persistence in DAT hydrogels over 11 days. Additionally, BLI demonstrated retention and survival of THP-1 cells following intramuscular injection in NOD/SCID mice within the DAT hydrogels compared to saline delivery controls, highlighting the potential of DAT hydrogels for localized monocyte delivery.

Summary for Lay Audience

Peripheral artery disease (PAD) is characterized by fat build up in the arteries leading to narrowed and obstructed arteries in the limbs. Critical limb ischemia (CLI) is the advanced stage of PAD, where poor blood flow results in tissue death, and non-healing wounds. Current therapies focus on symptom management, or surgical revascularization in severe cases. In some patients, limb amputation is inevitable. To mitigate the risk of limb amputation and the high mortality rate, there is a great interest in testing cell-based therapies to improve blood flow. Monocytes are a type of circulating white blood cell that has shown potential in improving blood flow in laboratory animals with CLI. Further, to help improve cell retention and survival following injection, biomaterials can function as cell-supportive delivery platforms. Specifically, this project explored the use of a biomaterial derived from human fat tissues, called decellularized adipose tissue (DAT) hydrogels. DAT hydrogels was shown to encapsulate the monocytic cells and support their retention and survival in cell culture over multiple days. Next, injection of cells in mice demonstrated that injection within DAT hydrogels improved cell survival and retention at the injection site compared to cells injected without the DAT hydrogels. Overall, this project contributes to the development of biomaterials as a regenerative strategy to enhance monocyte cell survival and retention towards the future development of a cell therapy to treat PAD.

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