| Description |
Mesenchymal stem cell (MSC)-based therapies present several ideal attributes of a promising new drug candidate in their innate ability to secrete a dynamic pharmacology of bioactive cytokines and growth factors that can influence nearby cells via paracrine signaling. MSC signals in turn stimulate various endogenous biological processes desirable for tissue regeneration, including angiogenesis, immune modulation, and cell recruitment and proliferation. However, when injected as a suspension, these cells suffer from poor survival and localization, and suboptimal release of paracrine factors, limiting their clinical efficacy to date. Delivering MSCs within tissue-engineered threedimensional (3D) platforms not only resolves issues of cell localization, engraftment, and survival, but a growing body of evidence finds that 3D culture stimulates MSC paracrine activity in response to higher abundance physical cell contacts and biochemical cellular interactions, otherwise known as a tissue effect. The goal of this dissertation was to overcome historical limitations of MSC therapies by engineering engraftable 3D MSC tissue-like constructs optimized for therapeutic potency through a tailored tissue effect. To achieve this goal, we employ cell sheet tissue engineering, a foremost method for creating 3D cell constructs without the use of a biomaterial scaffold and comprising only cells and endogenous matrix, interconnected by cell-cell and cell-matrix interactions. The central hypotheses of this dissertation are that the desired tissue effect is fundamentally realized using cell sheet tissue engineering, and that unique 3D structure and physical and biochemical cellular interactions from cell sheet engineering can be enhanced within cell sheets to stimulate individual MSC cytokine production potency. These hypotheses are addressed by (1) demonstrating that 3D cell sheet structure and cellular interactions augment individual MSC pro-regenerative cytokine (vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), interleukin-10 (IL-10)) secretion capacity in vitro, (2) demonstrating that cell sheet centrifugation augments individual MSC proregenerative cytokine (VEGF, HGF, IL-10) secretion capacity by directly increasing 3D cellular interactions, and (3) demonstrating that cell sheet multilayering from centrifugation increases absolute MSC sheet construct secreted pro-regenerative cytokine (VEGF, HGF, IL-10) dose. Ultimately, this dissertation delivers a complete in vitro platform for engineering and multilayering MSC sheet tissue optimized for MSC cytokine production. This research culminates in the generation of highly functional MSC sheets as a 3D cell-delivery technology for cell therapy applications. |
