Microenvironment specified lineage commitment of musculoskeletal progenitor cells derived from human embryonic stem cells

Human embryonic stem cells (hESCs), derived from the inner cell mass of the blastocyst, may have significant potential to impact musculoskeletal tissue engineering. The obvious advantage of using ES cells for musculoskeletal tissue regeneration is that ES cells are immortal and could potentially provide unlimited numbers of musculoskeletal-progenitor cells for transplantation. hESC expansion and differentiation in vitro are generally controlled by a 'cocktail' of growth factors, signaling molecules, extracellular environment and/or genetic manipulation. Clearly, more efficient and selective methods are needed to direct the proliferation and differentiation of stem cells, especially ES cells, to produce a homogenous population of specific cell types for regeneration applications. The general goals of this thesis therefore were to investigate human ES cells as a possible cell source for musculoskeletal tissue engineering. The long term objective of this research was to isolate mesenchymal precursor cells and chondrocytes from hESCs and characterize and identify the extracellular microenvironment cues, and the downstream signaling pathways, that drive the lineage specification and differentiation of cells derived from hESCs.; The extracellular microenvironment plays a significant role in controlling cellular behavior. Identification of appropriate biomaterials that support cellular attachment, proliferation and, most importantly in the case of hESCs, lineage specific differentiation is also critical for tissue engineering and cellular therapy. In addition to growth factors and morphogenetic factors known to induce lineage commitment of stem cells, a number of scaffolding materials, including synthetic and naturally derived biomaterials, have been utilized in tissue engineering to direct differentiation. In this study, scaffolds functionalized with specific peptides or naturally occurring biological proteins to influence cell function were created. Cell-ECM interaction as well as morphogenetic factors, either from exogenous supplementation or via cell-cell communication mediated secretions, played a pivotal role in regulating the lineage specification and formation of specific tissues. Based on recent emerging findings and well-characterized in vitro and in vivo differentiation models, this study established that hESCs are an attractive source of cells for musculoskeletal tissue engineering as well as understanding the musculoskeletal tissue development.