Doctor of Philosophy
Anatomy and Cell Biology
Flynn, Lauren E.
Human decellularized adipose tissue (DAT) represents a promising extracellular matrix (ECM) source for the development of biomaterials, with its properties conductive of angiogenesis, adipogenesis, and scaffold remodelling. This thesis sought to provide new fundamental insight into the design of ECM-derived bioscaffolds by developing novel modular biomaterials for soft connective tissue regeneration and by studying the effects of ECM composition on cell function and fate.
Initial studies explored the effects of ECM composition of pre-assembled bead foams derived from DAT or commercially-sourced bovine collagen (COL) on human wound edge dermal fibroblasts (weDFs) sourced from chronic wounds. In vitro testing under conditions simulating chronic wound stresses and in vivo investigation in a murine subcutaneous implantation model indicated that weDF survival and angiogenic marker expression were significantly enhanced in the DAT bead foams as compared to the COL bead foams. These results confirmed DAT as an ECM source with pro-regenerative properties.
Building from this work, a novel scaffold format comprised of fused networks of ECM-derived beads was generated through a “cell-assembly” approach using human adipose-derived stromal cells (ASCs) seeded on DAT beads. The cell-assembled bead foams, stabilized by the synthesis of new ECM, were structurally robust, easily handled, and contained a high density of viable ASCs distributed throughout the scaffold. Within a murine subcutaneous implantation model, the cell-assembled DAT bead foams showed enhanced early cell retention using a non-invasive in vivo cell tracking approach, along with increased detection of CD31+ endothelial cells within the implant at day 28, relative to ASC-seeded pre-assembled DAT bead foams. Overall, it was found that the novel cell-assembled DAT bead foams represented a promising pro-regenerative cell-delivery system.
The novel cell-assembly methods were extended to produce tissue-specific cell-assembled bead foams derived from decellularized trabecular bone (DTB) and COL. Preliminary findings indicated that the DAT and COL scaffold groups provided a highly supportive microenvironment for adipogenic differentiation in culture. Results also suggested that the DTB group may have inhibitory effects on ASC adipogenesis. Overall, this work established that the cell-assembly approach can be used to generate platforms for exploring the effects of ECM composition on stem cell differentiation.
Summary for Lay Audience
Soft connective tissues have a limited healing capacity following traumatic injuries or when subjected to chronic disease conditions, such as peripheral vascular disease and chronic wounds. To drive the repair and regeneration of these tissues, cellular therapies and biomaterials have both been independently investigated. However, a growing body of evidence is now showing that approaches combining the use of biomaterials and pro-regenerative cell populations may augment the efficacy of these new strategies.
Recognizing the need for new regenerative therapies, human decellularized adipose tissue (DAT) represents a promising source for the development of new biomaterials that can facilitate the localized delivery of therapeutic cells, such as adipose-derived stromal cells (ASCs). From this perspective, this thesis aimed to develop novel modular biomaterials for soft connective tissue regeneration using DAT and ASCs, and to study the effects of ECM composition within DAT-based biomaterials.
Initial studies explored the effects of ECM composition of “pre-assembled” bead foams on human wound edge dermal fibroblasts (weDFs) sourced from chronic wounds. Using pre- assembled bead foams derived from DAT and commercially-sourced bovine collagen (COL), it was found that the survival and capacity of the weDFs to stimulate blood vessel formation were significantly enhanced on the DAT bead foams. Building from these findings, a next- generation scaffold format was developed through a new cell-assembly approach using DAT beads seeded with ASCs. The novel “cell-assembled” DAT bead foams were structurally robust, easily handled, and contained a high density of viable ASCs homogeneously distributed throughout the biomaterial. Results from animal experiments showed that the new cell- assembled bead foams had a greater pro-angiogenic capacity than the previously-established pre-assembled bead foams, confirming their pro-regenerative potential. Lastly, the effects of ECM composition in this new biomaterial format were investigated by comparing cell- assembled bead foams produced from distinct ECM sources, including DAT, COL, and decellularized trabecular bone (DTB). Preliminary data suggested the DAT and COL bead foams promoted ASC differentiation into fat cells, while the DTB bead foams inhibited differentiation. Overall, the work completed in this thesis supports the rationale that DAT-derived bioscaffolds are promising pro-regenerative biomaterials and cell delivery platforms for applications in soft tissue regeneration.
Morissette Martin, Pascal, "Extracellular Matrix-Derived Modular Bioscaffolds for Soft Connective Tissue Regeneration" (2020). Electronic Thesis and Dissertation Repository. 6840.
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