Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Flynn, Lauren E.

2nd Supervisor

Hebb, Matthew O.

Co-Supervisor

Abstract

The use of brain extracellular matrix (ECM) as a biomaterial has the potential to promote neural tissue regeneration by providing cell-instructive cues that direct survival, proliferation, and differentiation. This study developed a novel detergent-free decellularization protocol that effectively reduced cellular content while preserving key ECM components in porcine and rat brains. The resulting decellularized brain tissue (DBT) was incorporated into microcarriers to assess its effects on the growth, phenotype and neurotrophic factor gene expression of rat brain-derived progenitor cells cultured within spinner flask bioreactors, using purified collagen microcarriers as a control. Both types of microcarriers supported cell expansion and survival, with robust expression of Olig1 and nestin observed after two weeks in culture, indicative of an oligodendrocyte precursor cell phenotype. Furthermore, culture on the DBT microcarriers enhanced the expression of glial-derived neurotrophic factor, highlighting the bioactive effects that can be harnessed within microcarrier scaffolds for applications in neural tissue engineering.

Summary for Lay Audience

Neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease typically result in the death of brain cells, causing disability and impairment. Current treatment options rely on the administration of drugs to manage symptoms. The damage to the brain caused by these diseases is generally irreversible, however, the discovery of stem cells in the brain has prompted the emergence of new therapies that aim to reverse the disease. While the delivery of stem cells to damaged regions of the brain can help promote tissue regeneration, it is challenging to control the fate of these stem cells and they often experience poor retention and survival. As such, there is growing interest in the development of biomaterials that appropriately mimic the native environment of the brain to culture these cells outside the body and eventually deliver them to the brain. This thesis aimed to develop a platform for neural cell culture that incorporated brain extracellular matrix (ECM), the natural scaffolding of all tissues in the body, composed of proteins and other molecules that provide support for the cells. A new protocol was developed to isolate the ECM from brain tissue by removing components that could invoke a negative immune response, while maintaining key proteins that influence cell behavior. The protein-rich material was then incorporated into small bead-shaped biomaterials called microcarriers, which are useful for the large-scale expansion of cells that is required for stem cell therapies. As a first step in testing the potential of this approach, a brain-derived regenerative cell population was cultured on the microcarriers for two weeks in a stirred bioreactor system. The results showed that the microcarriers could support the attachment, survival, and growth of the cells, and the ECM provided cues that affected the cell fate. Overall, these studies represent a key first step in developing biomaterials that can improve cell therapies to regenerate tissue in a damaged brain.

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