Todd McDevitt, Ph.D. (Advisor)
Thomas Barker, Ph.D.
Andrés Garcia, Ph.D.
Manu Platt, Ph.D.
Chunhui Xu, Ph.D. (Emory University)
Proteolytically Degradable Microparticles for Engineering the Extracellular Microenvironment of Pluripotent Stem Cell Aggregates
Embryonic stem cells (ESCs) offer tremendous promise for tissue engineering and regenerative medicine applications due to their pluripotent capacity to generate all bodily cell types. ESCs are typically differentiated as 3-dimensional aggregates, termed embryoid bodies (EBs), which recapitulate many biomolecular and biochemical events that occur during embryogenesis and facilitate the extracellular matrix production present in in vivo tissues that aid in stem cell regulation. However, EB differentiation is very heterogeneous, and manipulation of the EB microenvironment is increasingly being investigated to promote lineage specific differentiation, especially the potential of biomaterials to engineer the complex properties of the extracellular milieu. Incorporation of biomaterial microparticles (MPs) within EBs has demonstrated that materials are able to modulate stem cell pluripotency and differentiation, even in the absence of delivered biomolecules, however the mechanisms are not well known. Previous studies have demonstrated that introduction of proteolytically degradable materials within cellular environments have enhanced proteolytic activity specific to the introduced substrate. Additionally, protease activity has been highly implicated during stem cell differentiation, notably during the formation of all 3 germ lineages. The objective of this work was to engineer gelatin microparticles with tunable degradation rates and analyze their ability to modulate MMP activity and cellular differentiation. The central hypothesis was that incorporation of degradable gelatin MPs within EBs would enhance the proteolytic activity of the spheroids and would lead to enhanced mesodermal induction.