Principal Investigator Laura Kiessling
Pluripotent stem cells have the remarkable ability to indefinitely self-renew in culture and differentiate into any cell type. Within the stem cell niche, human pluripotent stem (hPS) cells receive signals from the extracellular matrix, soluble factors, and neighboring cells. Together, these signals direct hPS cell fate. Cell surface glycosaminoglycans (GAGs) mediate important signaling pathways critical for mammalian cell physiology but little is known about their roles in hPS cell self-renewal and differentiation. Our research addresses this gap.
We leveraged surface arrays to identify surfaces that would support the growth of human pluripotent (embryonic and induced pluripotent) stem cells. Our surface array revealed that surfaces that display a single glycosaminoglycan (GAG)-binding peptide were highly effective. This finding was especially exciting to us because GAGs are polysaccharides present on the surface of all mammalian cells. While others have examined surfaces that can interact with cell-surface proteins, our data indicate that carbohydrate polymers are important in pluripotency. We are currently investigating the roles of hES cell-surface GAGs in pluripotency and differentiation to each germ layer.
We have investigated how the stiffness of the surface on which hPS cells are cultured influences cell fate. Stiff hydrogels (elastic module of ~10 kPa) displaying a heparan sulfate-binding peptide support long term self-renewal of hPS cells while a soft hydrogel cannot. Soft substrata (~0.7 kPa) independent of soluble inductive factors promote highly efficient differentiation of hPS cells into postmitotic neurons. In the absence of neurogenic factors, the effective substrata produce neurons rapidly (2 wks) and more efficiently (>75%) than conventional differentiation methods. Our current focus is on the molecular mechanisms underlying mechanosensing in hPS cells.