Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Biomedical Engineering

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Flynn, Lauren

Abstract

The incorporation of meniscus extracellular matrix (ECM) into a 3D printable bioink has the potential to promote tissue regeneration by providing biological cues that direct cell survival, proliferation, and lineage-specific differentiation. This study developed region-specific meniscus ECM bioinks and assessed their effects on the viability, retention, and differentiation of adipose-derived stromal cells (ASCs). A novel meniscal decellularization protocol was developed and demonstrated effective removal of cellular content and preservation of key ECM constituents. When incorporated into alginate-based bioinks, the decellularized inner and outer meniscus demonstrated cell-instructive effects supporting ASC retention, and enhancing differentiation towards a fibrochondrogenic phenotype when cultured with chondrogenic differentiation medium. These studies provide relevant new insight supporting that region-specific ECM can be harnessed to direct cell phenotype and function within tissue-engineered scaffolds.

Summary for Lay Audience

The meniscus is the most commonly injured structure in the knee joint. With a limited capacity for self-repair, injury often requires surgical intervention. Due to a lack of repair techniques, the leading procedure used in this treatment is the complete or partial removal of the damaged tissue, otherwise known as a meniscectomy. The meniscus plays an important role in ensuring the health of the knee joint, and therefore, its removal is associated with wear and tear of the joint that ultimately leads to the onset of osteoarthritis (OA). OA inflicts significant health and economic burdens on society, as it is the second most prevalent chronic condition in Canada. As such, there is a critical need for an effective treatment that promotes regeneration and restores the function of the meniscus. Three-dimensional (3D) bioprinting is a technique that can be used to fabricate customizable meniscus implants. However, one limitation of this approach is that the standard materials being used do not incorporate biological cues to direct cells in the repair process. This project focuses on incorporating meniscus-specific proteins and a regenerative cell population into a printable bioink. Overall, these proteins may enhance cell survival and direct the differentiation of the encapsulated cells to help regenerate injured meniscal tissues. This thesis developed a new protocol for isolating meniscus-specific proteins with minimal changes to their native characteristics. A modified liquid form of these proteins was then incorporated into a printable bioink with regenerative cells derived from human fat tissue. As a first step towards testing the potential of this therapy, gel beads were made from the protein-containing bioinks and cultured for 28 days. For comparative purposes, an additional bioink that did not contain meniscus proteins was also cultured for 28 days. The results indicated that the incorporation of meniscus proteins into the bioink promoted the cells to remain inside of the beads and provided evidence that the regenerative cells were directed towards meniscus-like cells. These studies represent a key first step in developing a 3D bioprintable therapy to regenerate damaged meniscus.

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